tag:theconversation.com,2011:/us/topics/paleoanthropology-20528/articles
Paleoanthropology – The Conversation
2023-11-30T19:03:33Z
tag:theconversation.com,2011:article/216642
2023-11-30T19:03:33Z
2023-11-30T19:03:33Z
Controversial claims about extinct humans are stirring up evolution research. Here’s how the mess could have been avoided
<p>In June, researchers led by palaeoanthropologist Lee Berger published <a href="https://www.nytimes.com/2023/06/05/science/ancient-humans-homo-naledi-buried-dead.html">sensational claims</a> about an extinct human species called <em>Homo naledi</em> online and in the Netflix documentary <a href="https://www.imdb.com/title/tt27837467/">Unknown: Cave of Bones</a>. They argued the small-brained <em>H. naledi</em> <a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543127v1.article-metrics">buried their dead</a> in Rising Star Cave in South Africa more than 240,000 years ago, and may also have decorated the cave walls with engravings. </p>
<p>If true, this would be an astonishing new entry in the annals of human evolution. But <a href="https://theconversation.com/major-new-research-claims-smaller-brained-homo-naledi-made-rock-art-and-buried-the-dead-but-the-evidence-is-lacking-207000">many scientists</a> – including ourselves (the authors of this article, along with Ian Moffat at Flinders University in Australia, Andrea Zerboni at the University of Milan in Italy, and Kira Westaway at Macquarie University in Australia) – are not convinced by the evidence in the three online articles.</p>
<p>The peer reviewers of these articles and the journal editor found that the evidence was “inadequate” and <a href="https://elifesciences.org/reviewed-preprints/89106/reviews#tab-content">suggested a comprehensive list of changes</a> that would be needed to make the articles’ argument convincing. More recently, a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0047248423001434?dgcid=coauthor">strongly worded, peer-reviewed critique</a> by one of us (Herries) concluded there was not enough evidence to support the hypothesis that <em>H. naledi</em> carried out intentional burials.</p>
<h2>The need for an analytical revolution</h2>
<p>What would “enough evidence” for such claims look like? As we argue in a new comment piece in <a href="https://www.nature.com/articles/s41559-023-02215-5">Nature Ecology and Evolution</a>, there are modern scientific techniques that could provide it. </p>
<p>There are many kinds of evidence for human evolution, such as fossils and artefacts, and the sediment (or dirt) from which they are recovered. There are also many new and creative ways we can use to study this evidence. </p>
<p>We argue that the routine use of these techniques to generate supporting data will help avoid future controversies and increase public confidence in such claims. </p>
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<a href="https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A woman in a lab coat examining a dish full of rock or soil." src="https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1057&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1057&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1057&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1328&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1328&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559804/original/file-20231116-18-u8tdzn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1328&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Archaeological scientist Kelsey Hamilton at work, Flinders University, Adelaide.</span>
<span class="attribution"><span class="source">Mike Morley</span></span>
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<h2>Scientific collaborations</h2>
<p>Human evolution researchers deal with very long timescales, often measured in hundreds of thousands – or even millions – of years. Because of this, we often work with geologists and other Earth scientists, and use their ideas and tools to analyse traces of ancient humans.</p>
<p>The analytical techniques of the Earth sciences can provide extremely useful information about the context of fossils and archaeological material. </p>
<p>These techniques are commonly used to study the sediments that the archaeology and fossils are recovered from. These kinds of analyses can be carried out at the microscopic level, which means we can find information about the collected remains that would otherwise be impossible to obtain.</p>
<h2>Answers in the dirt</h2>
<p>Better instruments and ways to study dirt means that archaeological science can be used to understand the processes that form archaeological sites and preserve fossils and artefacts in incredibly detailed ways. We can even study evidence at the scale of <a href="https://theconversation.com/digging-deep-dna-molecules-in-ancient-dirt-offer-a-treasure-trove-of-clues-to-our-past-172489">molecules and elements</a>.</p>
<p>One way of studying dirt that is gaining traction in the field is known as micromorphology. This method involves the microscopic analysis of sediment that surrounds fossils or archaeology.</p>
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Read more:
<a href="https://theconversation.com/dishing-the-dirt-sediments-reveal-a-famous-early-human-cave-site-was-also-home-to-hyenas-and-wolves-122458">Dishing the dirt: sediments reveal a famous early human cave site was also home to hyenas and wolves</a>
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<p>By studying intact blocks of sediment removed from archaeological trenches, microscopic clues can be pieced together to reconstruct the past environments present at the site and in the local environment.</p>
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<img alt="A close up view of a slice of brown-and-white rock." src="https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/561786/original/file-20231127-27-h0u61t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A microscopic view of hyena coprolite (fossilised excrement) including pieces of bone.</span>
<span class="attribution"><span class="source">Mike Morley</span></span>
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<p>What’s more, the same blocks of sediment can be used for other analyses, such as refining the ages of the dirt and to better understand how archaeological sites form and preserve up until the point of discovery.</p>
<h2>What’s in the dirt? Science can tell us</h2>
<p>Micromorphology has proven to be a powerful tool for analysing ancient human remains and burial practices. In 2021, scientists who studied the oldest known human burial (78,000 years ago) used micromorphology to help identify the burial and publish the work in <a href="https://www.nature.com/articles/s41586-021-03457-8">Nature</a>.</p>
<p>Earlier, in 2017, the technique was used to identify <a href="https://www.sciencedirect.com/science/article/pii/S0305440316300838?casa_token=wf5YCUeuqCoAAAAA:PM8L5sZsNrsur2Jvvt49y2nVK2Q-d8VX5tIwBRpeL42Pjqp1Gp-q0B3dgoJdHV4ai9qHCkM-WQ">hearth features at Liang Bua cave (Indonesia)</a>. These small fireplaces were not obvious to the naked eye but under the microscope showed all of the characteristics of burning, including micro-traces of charcoal and ash. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of a thin slice of rock showing a dark band and traces of soot on a paler background." src="https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=896&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=896&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=896&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1126&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1126&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562032/original/file-20231128-29-qinibd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1126&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A microscope slide showing traces of an ancient fireplace at Liang Bua cave.</span>
<span class="attribution"><span class="source">Mike Morley</span></span>
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<p>Fossils of <em>H. floresiensis</em> (dubbed “hobbits”) were also found in this cave. However, it turned out the hearths were made by <em>H. sapiens</em> 46,000 years ago, after the last appearance of the hobbits (around 60,000–50,000 years ago).</p>
<p>In the case of <em>H. naledi</em>, micromorphology could have provided evidence for, or against, the idea that the remains were deliberately buried. It might have found traces of a grave cut or subtle differences in the sediment used to cover the body that might not have been obvious during excavation. </p>
<p>In fact, three of the four peer reviewers of the original burial paper suggested micromorphology could have been used to interpret the sediments of the possible grave fill.</p>
<h2>What next?</h2>
<p>As scientists working in the field of human evolution, we are thrilled about the Rising Star Cave fossils and the recognition of <em>H. naledi</em> as a new member of our genus, <em>Homo</em>. We trust the team working at the site will soon present new data that convinces us all one way or the other about the question of intentional burial.</p>
<p>On the weight of the currently available evidence we agree with others that there is no compelling case for that particular mortuary practice at the site. However, there are a raft of scientific techniques that could help end the controversy.</p>
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Read more:
<a href="https://theconversation.com/major-new-research-claims-smaller-brained-homo-naledi-made-rock-art-and-buried-the-dead-but-the-evidence-is-lacking-207000">Major new research claims smaller-brained _Homo naledi_ made rock art and buried the dead. But the evidence is lacking</a>
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<p>It can be incredibly difficult for the public to disentangle facts from fiction. We believe scientists need to be extremely careful about how they communicate their findings to avoid an increase in scepticism towards scientists that can have a major impact across all aspects of modern life.</p>
<p>Aside from the <em>H. naledi</em> burial debate, we would like to see a future where all investigations into human evolution use these scientific techniques from the outset. This might avoid future controversy and find clues that strongly support hypotheses. This would also allow for greater confidence in findings presented to the scientific community and public alike.</p><img src="https://counter.theconversation.com/content/216642/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike W Morley receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Andy I.R. Herries receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Anna M. Kotarba-Morley receives funding from Australian Research Council, National Centre for Science in Poland, Queensland Department of Environment, and Science and Rock Art Australia. </span></em></p><p class="fine-print"><em><span>Renaud Joannes-Boyau receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Vito C. Hernandez receives funding from the College of Humanities, Arts and Social Sciences of Flinders University, and the Australian Research Council Future Fellowship grant of Associate Professor Mike Morley.</span></em></p>
How, when and where did modern humans evolve? Nobody has all the answers, but studying rock and dirt can put the debate on firmer footing.
Mike W. Morley, Associate Professor and Director, Flinders Microarchaeology Laboratory, Flinders University
Andy I.R. Herries, Professor of Palaeoanthropology, La Trobe University
Anna M. Kotarba-Morley, Lecturer in Museum and Curatorial Studies, University of Adelaide
Renaud Joannes-Boyau, Associate Professor, Southern Cross University
Vito C. Hernandez, Geoarchaeologist and Postgraduate Research Scholar, Flinders University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/207000
2023-06-06T02:42:34Z
2023-06-06T02:42:34Z
Major new research claims smaller-brained ‘Homo naledi’ made rock art and buried the dead. But the evidence is lacking
<figure><img src="https://images.theconversation.com/files/530232/original/file-20230606-23-klb0fr.jpeg?ixlib=rb-1.1.0&rect=48%2C24%2C5306%2C2183&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Wikimedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>On September 13 2013, speleologists Rick Hunter and Steven Tucker descended deep into South Africa’s Rising Star cave system and discovered the first evidence of an extraordinary assemblage of <a href="https://australian.museum/learn/science/human-evolution/hominid-and-hominin-whats-the-difference/">hominin</a> fossils. </p>
<p>To date, the remains of more than 15 individuals belonging to a previously unknown species of extinct human, dubbed <em>Homo naledi</em>, have been found in the cave. These short-statured, small-brained ancient cousins are thought to have lived in Southern Africa between 335,000 and 241,000 years ago.</p>
<p>Rising Star Cave is an exceptional resource for exploring the origins of our species. However, archaeological work at the site has been some of the <a href="https://www.sciencenews.org/article/pieces-homo-naledi-story-continue-puzzle">most</a> <a href="https://www.newyorker.com/magazine/2016/06/27/lee-berger-digs-for-bones-and-glory">controversial</a> in the discipline.</p>
<p><a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543127v1">Three</a> <a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543133v1">new</a> <a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543135v1">studies</a> made available today (as pre-prints awaiting peer review) claim to have found evidence <em>Homo naledi</em> intentionally buried their dead (a sophisticated practice we usually associate with <em>Homo sapiens</em>) and made rock art, which suggests advanced cognitive abilities. </p>
<p>However, as archaeologists who investigate early humans in Africa, we’re not convinced the new research stacks up.</p>
<h2>Did <em>Homo naledi</em> bury their dead?</h2>
<p>The research purports to have evidence <em>Homo naledi</em> undertook deliberate burial of their dead – a major claim. </p>
<p>So far, the <a href="https://www.nature.com/articles/s41586-021-03457-8">earliest secure evidence</a> for burial in Africa comes from the Panga ya Saidi cave site in eastern Kenya, excavated by our team and dated to 78,000 years ago. This burial of a <em>Homo sapiens</em> child meets rigorous criteria agreed upon by the scientific community for identifying <a href="https://www.sciencedirect.com/science/article/pii/S004724841100090X?casa_token=Ij7IJcdPIaoAAAAA:-oP3zX8NHW18oJetZcL9X494dJ4EkFBIoGdi8md-th8lFlFbcCDMwCt_pWFIXrcrxYZOIYsD">intentional human burial</a>.</p>
<p>The aim of the criteria is to help differentiate burial from other practices and phenomena that could lead to the depositing of human remains. These include, for example, the natural accumulation of skeletal parts in a predator’s cavern, or the kind of <a href="https://www.bbc.com/future/article/20120919-respect-the-dead">carrying and protecting</a> of dead bodies observed among cognitively advanced non-human species such as gorillas and chimpanzees.</p>
<p>The claimed <em>Homo naledi</em> burials precede the Panga ya Saidi burial evidence by as much as 160,000 years. If the claim is correct, it significantly pushes back evidence for advanced mortuary behaviour in Africa. It also implies intentional burial wasn’t limited to our species or other big-brained hominins.</p>
<p>Such a finding would force us to rethink the role of brain size in advanced “meaning-making” cognition, as well as what distinguishes our species from our ancestors.</p>
<p>But is there actually evidence for funerary behaviour at Rising Star Cave? According to standards set by the palaeoanthropology community, the evidence presented so far indicates no.</p>
<h2>Insufficient evidence</h2>
<p>The site’s researchers <a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543127v1">claim to have evidence</a> for three intentional burials. </p>
<p>However, not one of the burials provides compelling evidence of a deliberately excavated pit. Indeed, the shallow cavities may not be dug pits at all, but natural depressions where the bodies accumulated and were later disturbed by trampling, or partial cave collapse. </p>
<p>The alleged burials also fail to meet another fundamental criteria for deliberate burials: anatomical alignment of the body and articulation of skeletal remains. </p>
<p>In a deliberate burial, the body is generally intact and any minimal displacement can be explained by decomposition. That’s because burial involves immediately covering the body with soil, which protects the anatomical integrity of the skeleton.</p>
<p>Rising Star Cave so far hasn’t produced evidence for anything other than the general spatial association of some skeletal elements. At most, it provides evidence for the in-situ decomposition of particular body parts, such as an ankle, and partial hand and foot articulations.</p>
<p>Moreover, confirming intentional burial in the past has required the presentation of human remains in an arrangement that can’t have been achieved by chance. However, the scattered distribution of the remains at Rising Star prevents reconstruction of their original positions.</p>
<p>Other claimed evidence for funerary behaviour is equally uncompelling. A stone artefact supposedly included in the burial as a “grave good” is said to have scratches and edge serrations from use. But this so-called artefact’s shape suggests it may be natural. It’s still encased in sediment and has only been studied through <a href="https://en.wikipedia.org/wiki/Synchrotron_light_source">synchrotron X-ray</a>.</p>
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<a href="https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/530237/original/file-20230606-17-cso4oh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=543&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The purported stone artefact (from synchrotron X-ray) showing so-called scratches and edge serrations may actually be a natural rock and not culturally modified.</span>
<span class="attribution"><span class="source">Lee Berger et al</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
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<p>But perhaps the biggest barrier to confirming the status of the findings is that so far none of the alleged burials have been fully excavated. It’s therefore impossible to assess the completeness of the bodies, their original position, and the limits of the purported pits.</p>
<h2>Did <em>Homo naledi</em> make rock art?</h2>
<p>An equally splashy claim made in one of the publications is that <em>Homo naledi</em> left rock art on the walls of Rising Star Cave.</p>
<p>The <a href="https://www.biorxiv.org/content/10.1101/2023.06.01.543133v1">report</a> describes engravings in the form of deeply impressed cross-hatchings and geometric shapes such as squares, triangles, crosses and X’s. Further claims are made about the preparation of and potential repeated handling or rubbing of the associated rock surface, and the use of a similar “tool” to the one they claim was found with the alleged burial.</p>
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<a href="https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=906&fit=crop&dpr=1 600w, https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=906&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=906&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1139&fit=crop&dpr=1 754w, https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1139&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/530224/original/file-20230606-27-9qrejq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1139&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The researchers point to engravings in the wall as evidence of <em>Homo naledi’s</em> capability to create art and symbols. But these etchings haven’t been dated, and some of the lines look relatively recently etched.</span>
<span class="attribution"><a class="source" href="https://www.biorxiv.org/content/10.1101/2023.06.01.543133v1">Lee Berger et al</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This claim has major implications. To date, rock art has only reliably been linked to <em>Homo sapiens</em> and, in rarer cases, some of our large-brained ancestors. Similar to deliberate burial, producing rock art has major implications for the cognitive abilities of a species. It denotes a capacity for representation, and the creation and communication of meaning via abstract symbols. </p>
<p>The problem with the rock art at Rising Star Cave is that it’s undated. To imply any link with <em>Homo naledi</em> requires firm dates. This could be achieved through using dating techniques on associated residues or <a href="https://www.science.org/doi/abs/10.1126/sciadv.abd4648">natural deposits</a> covering the art, or by studying materials from excavated and dated archaeological layers that can be linked to the art (for instance, if they contain engraving tools or engraved rock fall fragments).</p>
<p>In the absence of dating, it’s simply spurious to claim the engravings were made by <em>Homo naledi</em>, rather than by another species (and potentially at a much later date).</p>
<h2>Did <em>Homo naledi</em> light up Rising Star Cave?</h2>
<p>The researchers also claim the mortuary and engraving activities in Rising Star Cave involved strategic use of fire for illumination. </p>
<p>In <a href="https://www.youtube.com/watch?v=kOtX_Bcs_F4&ab_channel=CarnegieScience">public lectures</a> and on social media they clarify they have found new evidence for hearths, including charcoal, ash, discoloured clay and burned animal bones. Yet none of the scientific research needed to confirm the use of fire has been carried out. Or if it has, it hasn’t been published.</p>
<p>Previously acquired radiocarbon dates obtained by the site investigators on the apparent hearth material provided <a href="https://www.youtube.com/watch?v=kOtX_Bcs_F4&ab_channel=CarnegieScience">very late dates</a> that distanced the hearths from the remains of <em>Homo naledi</em> by several hundred thousand years.</p>
<p>We’re not opposed to the idea that the Rising Star Cave witnessed precocious mortuary behaviour involving the intentional disposal of bodies by <em>Homo naledi</em>. But it’s clear the latest inferences require further investigation before they’re accepted by the broader scientific community.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/i-was-part-of-the-team-that-found-the-homo-naledi-childs-skull-how-we-did-it-171153">I was part of the team that found the Homo naledi child's skull: how we did it</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/207000/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Homo naledi had a brain less than half the size of our own. Yet the new research claims it had cognitive abilities far beyond what we might expect.
Michael Petraglia, Director, Australian Research Centre for Human Evolution, Griffith University
Emmanuel K. Ndiema, Senior Research Scientist, National Museums of Kenya
María Martinón-Torres, CENIEH Director, Atapuerca Research Team and author of "Homo imperfectus" (Ed. Destino), Centro Nacional de Investigación sobre la Evolución Humana (CENIEH)
Nicole Boivin, Professor, Max Planck Institute of Geoanthropology
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/196555
2023-05-02T12:14:34Z
2023-05-02T12:14:34Z
Enigmatic human fossil jawbone may be evidence of an early ‘Homo sapiens’ presence in Europe – and adds mystery about who those humans were
<figure><img src="https://images.theconversation.com/files/522664/original/file-20230424-25-snjmo4.jpg?ixlib=rb-1.1.0&rect=1041%2C1616%2C9952%2C6772&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Close examination of digital and 3D-printed models suggested the fossil needs to be reclassified.</span> <span class="attribution"><span class="source">Brian A. Keeling</span></span></figcaption></figure><p><em>Homo sapiens</em>, our own species, evolved in Africa sometime between <a href="https://doi.org/10.1038/nature22336">300,000</a> and <a href="https://doi.org/10.1038/s41586-021-04275-8">200,000</a> years ago. Anthropologists are pretty confident in that estimate, based on <a href="https://doi.org/10.1098/rstb.2015.0237">fossil</a>, <a href="https://doi.org/10.1038/325031a0">genetic</a> and <a href="https://doi.org/10.1016/j.quascirev.2008.09.010">archaeological</a> evidence.</p>
<p>Then what happened? How modern humans spread throughout the rest of the world is one of the most active areas of research in human evolutionary studies.</p>
<p>The earliest fossil evidence of our species outside of Africa is found at <a href="https://www.science.org/content/article/ancient-jawbone-suggests-our-species-left-africa-40000-years-earlier-expected">a site called Misliya cave</a>, in the Middle East, and dates to around 185,000 years ago. While additional <em>H. sapiens</em> fossils are found from around 120,000 years ago in this same region, it seems modern humans reached Europe much later.</p>
<p>Understanding when our species migrated out of Africa can reveal insights into present-day biological, behavioral and cultural diversity. While we <em>Homo sapiens</em> are the only humans alive today, <a href="https://doi.org/10.1016/j.quaint.2016.06.008">our species coexisted</a> with different human lineages in the past, including <a href="https://doi.org/10.3998/jar.0521004.0069.202">Neandertals</a> and <a href="https://doi.org/10.17746/1563-0110.2020.48.3.003-032">Denisovans</a>. Scientists are interested in when and where <em>H. sapiens</em> encountered these other kinds of humans.</p>
<p><a href="https://scholar.google.com/citations?user=EjyT0fIAAAAJ&hl=en&oi=ao">Our</a> <a href="https://scholar.google.com/citations?user=JG6YfO4AAAAJ&hl=en&oi=ao">recent</a> reanalysis of a <a href="https://doi.org/10.1016/j.jhevol.2022.103291">fossil jawbone from a Spanish site called Banyoles</a> is raising new questions about when our species may have migrated to Europe.</p>
<h2><em>Homo sapiens</em> fossils found in Europe</h2>
<p>The <a href="https://australian.museum/learn/science/human-evolution/a-timeline-of-fossil-discoveries/">first documented discoveries</a> of human fossils were in Europe, just before Darwin’s 1859 publication of “<a href="https://www.britannica.com/biography/Charles-Darwin/On-the-Origin-of-Species">The Origin of Species</a>.” Ideas of evolution were being actively debated within European universities and scientific societies.</p>
<p>Many of the earliest fossil findings were <a href="https://www.nhm.ac.uk/discover/who-were-the-neanderthals.html">Neandertals</a>, a species that evolved in Europe by 250,000 years ago and became extinct around 40,000 years ago. They <a href="https://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals">are also our closest evolutionary relatives</a> and, because of ancient interbreeding, the genomes of people today include Neandertal DNA. Because of their early historical presence, Neandertal fossils had a big influence on how early researchers thought about human evolution. </p>
<p>The first <a href="https://doi.org/10.1073/pnas.192464099">fossil evidence of Neandertals was found in 1856</a> during quarrying activities from the Neander Tal (Neander Valley) in Germany. Paleontologists took the hint and started to search for human fossils in other caves and exposed areas that preserved ancient sediments.</p>
<p>More than a decade later, in 1868, paleontologists uncovered <em>H. sapiens</em> fossils at the <a href="https://humanorigins.si.edu/evidence/human-fossils/fossils/cro-magnon-1">site of Cro-Magnon in southern France</a>. For much of the 20th century, the 30,000-year-old Cro-Magnon fossils represented the earliest fossil evidence of our species in Europe.</p>
<p>More recently, evidence for an earlier <em>H. sapiens</em> presence in Europe has come from two sites in Eastern Europe, including a partial skull from <a href="https://doi.org/10.1038/s41559-021-01443-x">Zlatý kůň Cave in Czechia</a> dating to 45,000 years ago, as well as more fragmentary remains from <a href="https://doi.org/10.1038/s41586-020-2259-z">Bacho Kiro Cave in Bulgaria</a> dating to around 44,000 years ago. Ancient DNA analysis has confirmed that the fossils from these sites represent <em>H. sapiens</em>. Additional, potentially earlier, evidence is represented by a <a href="https://theconversation.com/new-research-suggests-modern-humans-lived-in-europe-10-000-years-earlier-than-previously-thought-in-neanderthal-territories-176648">single tooth dating to 54,000 years ago</a> from the <a href="https://doi.org/10.1126/sciadv.abj9496">Grotte Mandrin Cave in France</a>.</p>
<p>This is where the human fossil from Banyoles comes into the story.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/t_ZZkzCbd3U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A new look at an old fossil find potentially pushes back the date when <em>Homo sapiens</em> lived in Europe.</span></figcaption>
</figure>
<h2>Reinvestigating a ‘Neandertal’ mandible</h2>
<p>Over a century ago in 1889, a fossil human lower jaw, or mandible, was found at a quarry near the town of Banyoles, in northeastern Spain. Pere Alsius, a prominent local pharmacist, first studied the mandible, and the fossil has been curated by his family ever since.</p>
<p>A number of anthropologists have studied the fossil over time, but it has not usually been included in discussions about <em>H. sapiens</em> in Europe. Most researchers instead argued it represented a Neandertal or showed Neandertal-like features, in part because the Banyoles fossil lacks a feature considered typical and diagnostic of our own species: a bony chin on the front of the mandible.</p>
<p>Researchers did not have a good idea of how old the Banyoles mandible was, with most believing it likely dated to the Middle Pleistocene (780,000-130,000 years ago). That age made it seem too old to represent <em>H. sapiens</em>. Thus, with the absence of a chin and the presumed early date, the designation as a Neandertal seemed to make sense.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing the green and rocky terrain of Spain with fossil discovery sites indicated." src="https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502873/original/file-20230103-20-qzh844.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map of the Iberian Peninsula indicating where the Banyoles mandible (yellow star) was found, along with Late Pleistocene Neandertal (orange triangles) and <em>H. sapiens</em> (white squares) sites.</span>
<span class="attribution"><span class="source">Brian A. Keeling</span></span>
</figcaption>
</figure>
<p>Based on recent modern <a href="https://doi.org/10.1007/978-1-4020-4409-0_50">uranium-series</a> and <a href="https://doi.org/10.1007/978-1-4757-9694-0_8">electron spin resonance</a> dating, researchers now believe the Banyoles mandible is between 45,000 and 66,000 years old. This younger estimate overlaps with the early <em>H. sapiens</em> fossils from Eastern Europe.</p>
<p>Working with Spanish paleoanthropologists and archaeologists, we took another look at what species the fossil might represent. We relied on a CT scan to virtually reconstruct damaged or missing portions of the mandible and generated a 3D model of the complete fossil. Then, we studied its overall shape and distinctive anatomical features, comparing it to <em>H. sapiens</em>, Neandertals and other earlier human species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three side-by-side digital reconstructions of the Banyoles mandible, from side and above." src="https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=200&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=200&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=200&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=251&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=251&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502874/original/file-20230103-26-x4inu6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=251&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Virtual reconstruction of the 3D model of the Banyoles mandible. Highlighted piece in blue indicates a mirrored element that researchers used to fill out missing sections.</span>
<span class="attribution"><span class="source">Brian A. Keeling</span></span>
</figcaption>
</figure>
<p>In contrast to earlier analyses, our results revealed that the Banyoles jawbone was most similar to <em>H. sapiens</em> fossils – not Neandertals.</p>
<p>When we examined the mandible’s bony features where muscle tendons and ligaments would have attached, it most closely resembled <em>H. sapiens</em>. We also found no unique bony features shared with the Neandertals. Additionally, when we used sophisticated 3D analysis techniques, we found that Banyoles’ overall shape was a better match with <em>H. sapiens</em> than with Neandertal individuals.</p>
<p>While nearly all of our evidence suggests this prehistoric human was indeed a member of our species, the lack of a chin remains puzzling. This feature is present in all human populations today and should be present in Banyoles if it is a member of our species.</p>
<h2>Figuring out the closest match</h2>
<p>How do we reconcile our results showing that Banyoles is a modern human with the fact that it lacks one of the most distinctive modern human features? We considered several possible scenarios.</p>
<p>When the mandible was discovered, it was still encased in a hard travertine block and only partially exposed. During initial cleaning and preparation of the specimen, it was <a href="https://helvia.uco.es/bitstream/handle/10396/16390/carandell51.pdf?sequence=1&isAllowed=y">accidentally dropped</a> and the chin region was damaged. The fossil was subsequently reconstructed, with the damaged fragments aligned in their correct anatomical position, and the current state of the fossil does seem to accurately reflect an original chinless shape. Thus, the lack of a chin in Banyoles cannot be attributed to this initial incident.</p>
<p>Could the lack of a chin in the Banyoles fossil be a result of interbreeding with Neandertals, who also lacked a chin? <a href="https://doi.org/10.1371/journal.pgen.1002947">Genetic evidence</a> suggests that <em>H. sapiens</em> most likely interbred with Neandertals between 45,000 and 65,000 years ago, making this a possibility.</p>
<p>To assess this hypothesis, we compared Banyoles with an early <em>H. sapiens</em> mandible dating to about 42,000 years ago from <a href="https://doi.org/10.1073%2Fpnas.2035108100">a Romanian site called Peştera cu Oase</a>. <a href="https://doi.org/10.1038/nature14558">Ancient DNA analysis</a> has revealed that the Oase individual had a Neandertal ancestor between four and six generations back, making it close to a hybrid individual. However, unlike Banyoles, this mandible shows a full chin along with some other Neandertal features. Since Banyoles shared no distinctive features with Neandertals, we ruled out the possibility of this individual representing interbreeding between Neandertals and <em>H. sapiens</em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three different lower jaw bones side by side" src="https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=226&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=226&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=226&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=284&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=284&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502875/original/file-20230103-24-rjv92m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=284&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Comparison of mandibles between <em>H. sapiens</em>, at left; Banyoles, center; and a Neandertal, at right.</span>
<span class="attribution"><span class="source">Brian A. Keeling</span></span>
</figcaption>
</figure>
<p>We’re left with two possibilities. Banyoles may represent a hybrid individual between <em>H. sapiens</em> and a non-Neandertal archaic human lineage. This scenario might account for the absence of the chin as well as the lack of any other Neandertal features in Banyoles. However, scientists haven’t identified any such non-Neandertal archaic group in the fossil record of the European <a href="https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx">Late Pleistocene</a> (129,000-11,700 years ago), making this hypothesis less likely.</p>
<p>Alternatively, Banyoles may document a previously unknown lineage of largely chinless <em>H. sapiens</em> in Europe. Possible support for this hypothesis comes from the fact that early <em>H. sapiens</em> fossils from Africa and the Middle East show a less prominent chin than do living humans. </p>
<p>Additionally, <a href="https://doi.org/10.1038/nature17993">ancient DNA research</a> has shown that <em>H. sapiens</em> populations in Europe before 35,000 years ago did not contribute to the modern European gene pool. Thus, we believe the least unlikely hypothesis is that Banyoles represents an individual from one of these early <em>H. sapiens</em> populations.</p>
<p>Our study of Banyoles demonstrates how new discoveries about our evolutionary past do not solely rely on new fossil discoveries, but can also come about through applying new methodologies to previously discovered fossils. If Banyoles is really a member of our species, it would potentially represent the earliest <em>H. sapiens</em> lineage documented to date in Europe. Future ancient DNA analysis could confirm or refute this surprising result. In the meantime, <a href="https://www.morphosource.org/">the 3D model of Banyoles</a> is available for other researchers to study and form their own conclusions.</p><img src="https://counter.theconversation.com/content/196555/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Scientists had figured a fossil found in Spain more than a century ago was from a Neandertal. But a new analysis suggests it could be from a lost lineage of our species, Homo sapiens.
Brian Anthony Keeling, Doctoral Candidate in Anthropology, Binghamton University, State University of New York
Rolf Quam, Associate Professor of Anthropology, Binghamton University, State University of New York
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/203532
2023-04-13T18:03:53Z
2023-04-13T18:03:53Z
Wooded grasslands flourished in Africa 21 million years ago – new research forces a rethink of ape evolution
<figure><img src="https://images.theconversation.com/files/520610/original/file-20230412-18-2l6ftt.png?ixlib=rb-1.1.0&rect=5%2C808%2C3552%2C3217&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An ape that lived 21 million years ago was used to a habitat that was both grassy and wooded.</span> <span class="attribution"><span class="source">Corbin Rainbolt</span></span></figcaption></figure><p>Human evolution is tightly connected to the environment and landscape of Africa, <a href="https://humanorigins.si.edu/evidence/human-fossils/species/sahelanthropus-tchadensis">where our ancestors first emerged</a>.</p>
<p>According to the traditional scientific narrative, Africa was once a verdant idyll of vast forests stretching from coast to coast. In these lush habitats, around 21 million years ago, the earliest ancestors of apes and humans first evolved traits – including upright posture – that distinguished them from their monkey cousins.</p>
<p>But then, the story went, global climates cooled and dried, and forests began to shrink. By about 10 million years ago, grasses and shrubs that were better able to tolerate the increasingly dry conditions started to take over eastern Africa, replacing forests. The earliest hominins, our distant ancestors, ventured out of the forest remnants that had been home onto the grass-covered savanna. The idea was that this new ecosystem pushed a radical change for our lineage: We became bipedal.</p>
<p>For a long time, researchers have <a href="https://doi.org/10.1038/s41598-020-69378-0">linked the expansion of grasslands in Africa</a> to the evolution of numerous human traits, including walking on two legs, using tools and hunting.</p>
<p>Despite the prominence of this theory, mounting evidence from paleontological and paleoclimatological research undermines it. <a href="https://www.science.org/doi/10.1126/science.abq2834">In two</a> <a href="https://www.science.org/doi/10.1126/science.abq2835">recent papers</a>, our multidisciplinary team of Kenyan, Ugandan, European <a href="https://scholar.google.com/citations?user=DjYvbR8AAAAJ&hl=en">and</a> <a href="https://scholar.google.com/citations?user=W7H_Y0oAAAAJ&hl=en&oi=ao">American</a> <a href="https://scholar.google.com/citations?user=gwZCXkQAAAAJ&hl=en&oi=ao">scientists</a> concluded that it is time finally to discard this version of the evolutionary story.</p>
<p>A decade ago, we began what, at the time, was a unique experiment in paleoanthropology: Several independent research teams joined together to build a regional perspective on the evolution and diversification of early apes. The project, dubbed REACHE, short for Research on Eastern African Catarrhine and Hominoid Evolution, was based on the premise that conclusions drawn from evidence across many locations would be more powerful than interpretations from individual fossil sites. We wondered whether previous researchers had missed the forest for the trees.</p>
<h2>An ape in Uganda 21 million years ago</h2>
<p>Based on the lifestyle of apes alive today, scientists have hypothesized that the very first ones evolved in dense forests, <a href="https://doi.org/10.1086/284139">where they successfully fed on fruit</a>, thanks to a few key anatomical innovations.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/QKuyv6YdBx4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Chimpanzees move with an upright posture.</span></figcaption>
</figure>
<p>Apes have stable, upright backs. <a href="https://doi.org/10.1007/978-3-319-47829-6_2001-1">Once the back is vertical</a>, an ape no longer has to walk on the top of small branches like a monkey. Instead, it can grab different branches with its arms and legs, distributing its body mass across multiple supports. Apes can even hang below branches, making them less likely to lose their balance. In this way, they are able to access fruits growing on the edges of tree crowns that otherwise might be available only to smaller species.</p>
<p>But was this scenario true for the earliest apes? A 21 million-year-old site in Moroto, Uganda, became an ideal place to investigate this question. There our REACHE team discovered teeth and other remains belonging to <em>Morotopithecus</em>, the oldest ape for which scientists have found fossils from the cranium, teeth and other parts of the skeleton.</p>
<p>Two bones in particular helped us understand how this species moved. A lower backbone found decades ago and curated by the Uganda National Museum had already been noted for its <a href="https://doi.org/10.1006/jhev.1994.1012">bony attachments for back muscles</a>, indicating that <em>Morotopithecus</em> had a stiff lower back, good for climbing upright in the trees.</p>
<p>A discovery of our own confirmed this climbing behavior in a major way. At Moroto we found a fossil ape thigh bone that is short but strong, with a very thick shaft. This kind of bone is characteristic of living apes and helps them climb up and down trees with a vertical torso.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="vertebra, partial jaw and femur fossils" src="https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520652/original/file-20230413-20-yvp928.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Three fossilized bones from <em>Morotopithecus</em>: a vertebra, part of a jaw and a femur.</span>
<span class="attribution"><span class="source">L. MacLatchy and J. Kingston</span></span>
</figcaption>
</figure>
<p>Although both skeletal fossils are consistent with the fruit-eating, forest-dwelling ape hypothesis, <a href="https://www.science.org/doi/10.1126/science.abq2835">we found something astonishing</a> when we discovered an ape lower jaw fragment in the same excavation layer. Its molars were elongated, with well-developed shearing crests running between the cusps. These ridges are ideal for slicing leaves but are unlike the low, round, crushing tooth cusps of committed fruit eaters. If ape skeletal adaptations evolved in forests to aid in fruit exploitation, why would the earliest ape showing these locomotor features instead have teeth like a leaf eater’s?</p>
<p>Such inconsistencies between our evidence and the traditional narrative of ape origins led us to question other assumptions: Did <em>Morotopithecus</em> live in a forested habitat at all? </p>
<h2>The environment at Moroto</h2>
<p>To figure out <em>Morotopithecus’</em> habitat, we studied the chemistry of fossil soils – called paleosols – and the microscopic remains of plants they contain in order to reconstruct the ancient climate and vegetation at Moroto.</p>
<p>Trees and most shrubs and nontropical grasses are classified as C₃ plants, based on the type of photosynthesis they perform. Tropical grasses, which rely on a different photosynthetic system, are known as C₄ plants. Importantly, C₃ plants and C₄ plants differ in the proportions of the various carbon <a href="https://www.britannica.com/science/isotope">isotopes</a> they take in. That means carbon isotope ratios preserved in the paleosols can tell us the composition of the ancient vegetation.</p>
<p>We measured three distinct carbon isotope signatures, each providing a different perspective on the plant community: carbon resulting from decomposition of vegetation and soil microbes; carbon resulting from plant waxes; and calcium carbonate nodules formed in soils through evaporation.</p>
<p>Although each proxy gave us slightly different values, <a href="https://www.science.org/doi/10.1126/science.abq2834">they converged on a single remarkable story</a>. Moroto was not a closed forest habitat but rather a relatively open woodland environment. What’s more, we found evidence of abundant C₄ plant biomass – tropical grasses.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Traditional versus updated view of early ape habitat and evolution" src="https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=484&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=484&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=484&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=608&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=608&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520653/original/file-20230413-16-s1no2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=608&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">(A) Forested ecosystem traditionally believed to be the habitat of early apes, which ate fruit at the ends of tree branches, compared with (B) new perspective of grassy woodland ecosystem reconstruction, where early apes lived in open habitats and fed on leaves.</span>
<span class="attribution"><span class="source">Figure modified with permission from MacLatchy et al., Science 380, eabq2835 (2023)</span></span>
</figcaption>
</figure>
<p>This discovery was a revelation. C₄ grasses lose less water during photosynthesis than C₃ trees and shrubs do. Today, C₄ grasses dominate seasonally dry savanna ecosystems that <a href="https://unesdoc.unesco.org/ark:/48223/pf0000058054">cover more than half of Africa</a>. But scientists hadn’t thought the levels of C₄ biomass we measured at Moroto had evolved in Africa until 10 million years ago. Our data suggests it happened twice as far back in time, 21 million years ago.</p>
<p>Our colleagues <a href="https://scholar.google.com/citations?user=A5RCBfEAAAAJ&hl=en&oi=ao">Caroline Strömberg</a>, Alice Novello and <a href="https://scholar.google.com/citations?user=Sg0Q5xkAAAAJ&hl=en&oi=ao">Rahab Kinyanjui</a> used another line of evidence to corroborate the abundance of C₄ grasses at Moroto. They analyzed phytoliths, tiny silica bodies created by plant cells, preserved in the paleosols. Their results supported an open woodland and wooded grassland environment for this time and place.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Early Miocene grass phytoliths" src="https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520540/original/file-20230412-20-hnv0wy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Example of typical grass phytoliths, extracted from paleosol at one of the sites, some of which indicate the presence of C₄ grass.</span>
<span class="attribution"><span class="source">Alice Novello</span></span>
</figcaption>
</figure>
<p>Taken together, this evidence dramatically contradicts the traditional view of ape origins – that apes evolved upright torsos to reach fruit in forest canopies. Instead, <em>Morotopithecus</em>, the earliest known ape with upright locomotion, consumed leaves and inhabited an open woodland with grassy areas.</p>
<h2>A new, regional view of early ape habitats</h2>
<p>Through the REACHE project, we applied the same approach to reconstruct habitats at eight other fossil sites in Kenya and Uganda, ranging in age from around 16 million to 21 million years old. After all, <em>Morotopithecus</em> is only one of several apes that lived during this time period.</p>
<p>To our surprise, we discovered that the ecological signal measured at Moroto was not unique. Instead, it was part of a broader pattern in eastern Africa during this time. </p>
<p>Our isotopic proxies at each fossil site contributed two significant revelations. First, vegetation types ranged from closed canopy forests to open wooded grasslands. And second, every site had a mixture of C₃ and C₄ vegetation, with some locations having a high proportion of C₄ grass biomass. Phytoliths from the same paleosols again corroborated that abundant C₄ grasses were present at multiple sites. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cartoon depictions of nine paleoenvironments placed on timeline" src="https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=274&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=274&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=274&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=345&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=345&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520539/original/file-20230412-20-ys57ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=345&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Paleoenvironments for the nine fossil sites analyzed range from closed canopy forest to more open wooded grassland environments. Inset map shows the geographic location of sites in eastern Africa.</span>
<span class="attribution"><span class="source">Dan Peppe</span></span>
</figcaption>
</figure>
<p>The realization that such a variety of environments, especially open habitats with C₄ grasses, was present at the dawn of the apes forces a reassessment not just of the evolution of apes but of humans and other African mammals. Although some studies had suggested such habitat variation was present across Africa, our project was able to confirm it, repeatedly, within the very habitats that early apes and their animal contemporaries occupied.</p>
<p>Because the timing of the assembly of Africa’s grassland habitats underlies many evolutionary hypotheses, our discovery that they existed much earlier than expected calls for a recalibration of those ideas.</p>
<p>Regarding human origins, our study adds to a growing body of evidence that our divergence from apes – in anatomy, ecology, behavior – cannot be simply explained by the appearance of grassland habitats. Nevertheless, we cautiously remind ourselves that hominin evolution unfolded over many millions of years. It is almost certain that the vast and majestic grasslands of Africa played an important role in some of the many steps along the path to becoming human.</p><img src="https://counter.theconversation.com/content/203532/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura M MacLatchy receives funding from the US National Science Foundation, the LSB Leakey Foundation, the Wenner-Gren Foundation and the University of Michigan. </span></em></p><p class="fine-print"><em><span>Dan Peppe receives funding from National Science Foundation, Leakey Foundation, Baylor University.</span></em></p><p class="fine-print"><em><span>Kieran McNulty has received funding from the National Science Foundation, Leakey Foundation, Wenner-Gren Foundation, Leverhulme Foundation, and the University of Minnesota. </span></em></p>
Contrary to the idea that apes evolved their upright posture to reach for fruit in the forest canopy, the earliest known ape with this stature, Morotopithecus, lived in more open grassy environments.
Laura M. MacLatchy, Professor of Anthropology, University of Michigan
Dan Peppe, Associate Professor of Geosciences, Baylor University
Kieran McNulty, Professor of Anthropology, University of Minnesota
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/193167
2023-01-25T13:25:51Z
2023-01-25T13:25:51Z
Fossil teeth reveal how brains developed in utero over millions of years of human evolution – new research
<figure><img src="https://images.theconversation.com/files/505255/original/file-20230118-16643-pgt4h9.jpg?ixlib=rb-1.1.0&rect=861%2C1219%2C4422%2C3038&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Any hominid fossil find with molar teeth can be plugged into a new equation that reveals its species' prenatal growth rate.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/archaeologist-yossi-zaidner-from-the-hebrew-universitys-news-photo/1233682440?phrase=human%20fossil%20skull">Gil Cohen-Magen/AFP via Getty Images</a></span></figcaption></figure><p>Fossilized bones help tell the story of what human beings and our predecessors were doing hundreds of thousands of years ago. But how can you learn about important parts of our ancestors’ life cycle – like pregnancy or gestation – that leave no obvious trace in the fossil record?</p>
<p>The large brains, relative to overall body size, that are a defining characteristic of our species make pregnancy and gestation particularly interesting to <a href="https://scholar.google.com/citations?user=UdOOsTAAAAAJ&hl=en&oi=ao">paleoanthropologists like me</a>. <em>Homo sapiens’</em> big skulls contribute to our difficult labor and delivery. But the big brains inside are what let our species really take off.</p>
<p>My colleagues and I especially wanted to know how fast our ancestors’ brains grew before birth. Was it comparable to fetal brain growth today? Investigating when prenatal growth and pregnancy became humanlike can help reveal when and how our ancestors’ brains became more like ours than like our ape relatives’.</p>
<p>To investigate the evolution of prenatal growth rates, we focused on the in-utero development of teeth – which do fossilize. <a href="https://doi.org/10.1073/pnas.2200689119">By building a mathematical model</a> using the relative lengths of molar teeth, we were able to track evolutionary changes in prenatal growth rates in the fossil record. Based on our model, it looks as if pregnancy and prenatal growth became more humanlike than chimplike almost 1 million years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="pregnant woman's silhouette against sunset on landscape" src="https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505651/original/file-20230120-26-idfswj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pregnancy and delivery come with a lot of risks for parent and baby.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/silhouette-pregnant-woman-standing-on-field-against-royalty-free-image/1082494338">Jimy Lindner/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>Gestation and the human brain</h2>
<p><a href="https://doi.org/10.1002/(SICI)1520-6505(1998)6:2%3C54::AID-EVAN3%3E3.0.CO;2-W">Pregnancy and gestation are important periods</a> – they guide future growth and development and set the biological course for life.</p>
<p>But human pregnancy, and particularly labor and delivery, <a href="https://doi.org/10.1152/physiologyonline.1996.11.4.149">cost a lot of energy</a> and are often dangerous. The large fetal brain requires a lot of nutrients during development. The rate of embryonic growth during gestation, also known as the prenatal growth rate, exacts a metabolic and physiological toll on the gestating parent. And the <a href="https://doi.org/10.1002/ajpa.1330350605">tight fit of the infant’s head and shoulders</a> through the pelvic canal during delivery can lead to death, for both the mother and child.</p>
<p>As a trade-off to those potential downsides, there must be a really good reason to have such large heads. The justification is all the abilities that <a href="https://doi.org/10.1016/j.jhevol.2009.04.009">come along with having a big human brain</a>. The <a href="https://doi.org/10.1098/rstb.2012.0115">evolution of our large brain</a> contributed to our species’ dominance and is associated with increased use of technology and tools, creation of art and the ability to survive in diverse landscapes, among other advances.</p>
<p>The timing and sequence of events that led to the evolution of our large brains is entangled with the ability to find and process more resources, through the use of tools and <a href="https://doi.org/10.1086/667623">cooperative group work</a>, for example.</p>
<p>By investigating changes in prenatal growth, we are also investigating changes in how parents gathered food resources and distributed them to their offspring. These increasing resources would have also helped drive the evolution of an even bigger brain. Understanding more about when prenatal growth and pregnancy became humanlike at the same time reveals information about when and how our brains did too.</p>
<p><a href="https://doi.org/10.1073/pnas.2200689119">Humans have the highest prenatal growth rate</a> of all primates living today, at 0.41 ounces/day (11.58 grams/day). Gorillas, for example, have a much larger adult body size than humans, but their prenatal growth rate is only 0.29 ounces/day (8.16 grams/day). Because <a href="https://carta.anthropogeny.org/moca/topics/proportion-pre-and-postnatal-brain-growth">more than a quarter of all human brain growth</a> is completed during gestation, the rate of prenatal growth directly relates to how big an adult brain grows. How and when <em>Homo sapiens</em>‘ high prenatal growth rate evolved has been a mystery, until now.</p>
<h2>What teeth can tell about prenatal growth</h2>
<p>Researchers have spent centuries investigating variation in fossilized skeletal remains. Unfortunately brains – let alone gestation and prenatal growth rate – don’t fossilize.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ultrasound of a baby in utero" src="https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=623&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=623&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=623&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=783&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=783&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505250/original/file-20230118-20-a40toc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=783&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The developing brain of a human being gestating at 26 weeks.</span>
<span class="attribution"><span class="source">Tesla Monson</span></span>
</figcaption>
</figure>
<p>But my colleagues and I started thinking about how teeth develop very, very early in utero. Your permanent adult teeth started developing long before you were born, when you were just a 20-week-old fetus.
<a href="https://doi.org/10.1016/j.crpv.2016.10.006">Tooth enamel is more than 95% inorganic</a>, and the vast majority of everything we see in the vertebrate fossil record is teeth, or has teeth.</p>
<p>Building off this realization, we decided to investigate the relationship between prenatal growth rate, brain size and the lengths of teeth.</p>
<p>We measured the teeth of 608 recently living primates from skeletal collections all around the world. We compared those measurements to rates of prenatal growth that we calculated from average gestation length and mass at birth for each species. We also looked at endocranial volume – essentially how much space is inside the skull – as a proxy for brain size.</p>
<p><a href="https://doi.org/10.1073/pnas.2200689119">We found that the rate of prenatal growth</a> is significantly correlated with both adult brain size and relative tooth lengths, across apes and monkeys.</p>
<p>Because prenatal growth is so tightly correlated with relative molar lengths, we were able to use this statistical relationship to generate a mathematical equation that predicts prenatal growth rate from teeth alone. With this equation, we can take a few molar teeth from an extinct fossil species and reconstruct exactly how fast their offspring grew during gestation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="alt" src="https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=276&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=276&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=276&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=346&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=346&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505479/original/file-20230119-5264-t8y9ql.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=346&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Using the new equation, researchers found that prenatal growth rates increased over millions of years of human and hominid evolution.</span>
<span class="attribution"><span class="source">Tesla Monson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Using our new method, we then reconstructed prenatal growth rates for 13 fossil species, building a timeline of changes over the past 6 million years of human and hominid evolution. “Hominid” describes all the species on the human side of the family tree after the split about 6 million to 8 million years ago from the common ancestor we shared with chimpanzees. From our new research, we now know that prenatal growth rates increased throughout hominid evolution, reaching a humanlike rate that exceeds what we see in all other apes less than 1 million years ago.</p>
<p>A fully human prenatal growth rate appeared with the evolution of our species <em>Homo sapiens</em> only around 200,000 years ago. But other hominid species living in the past 200,000 years, such as Neanderthals, also had “human” prenatal growth rates. Which genes were involved in these changes in growth rate remains to be investigated.</p>
<h2>Equation means teeth now reveal even more</h2>
<p><a href="https://doi.org/10.1002/1096-8644(200103)114:3%3C192::AID-AJPA1020%3E3.0.CO;2-Q">Even with only a few teeth and some of the jaw</a>, <a href="http://www.annualreviews.org/doi/full/10.1146/annurev-an-42">a trained expert can tell countless things</a> about an extinct individual – what species it was, what kind of diet it ate, whether it competed for mates through fighting, how old it was when it died, whether or not it had any serious health issues and more.</p>
<p>Now, for the first time, we can add to that list knowing what pregnancy and gestation were like for that individual and other members of its species. Teeth can even indirectly hint at the emergence of human consciousness, via evolving brain size.</p>
<p>Interestingly, our model suggests that prenatal growth rates started increasing well before the emergence of our <em>Homo sapiens</em> species. We can hypothesize that having a fast prenatal growth rate was necessary for growing that big brain and evolving human consciousness and cognitive abilities.</p>
<p>These are the sorts of big-picture questions this research lets us start to formulate now – all from just a few teeth.</p><img src="https://counter.theconversation.com/content/193167/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This research was supported through grants to Tesla Monson's collaborators by the Washington Research Foundation and the John Templeton Foundation. Much of the data collection for the extant primates was funded by National Science Foundation Division of Behavioral and Cognitive Sciences grants 0500179, 0616308, and 0130277.</span></em></p>
Using a new equation based on today’s primates, scientists can take a few molar teeth from an extinct fossil species and reconstruct exactly how fast their offspring grew during gestation.
Tesla Monson, Assistant Professor of Anthropology, Western Washington University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/192595
2022-10-19T19:05:47Z
2022-10-19T19:05:47Z
First-ever genetic analysis of a Neanderthal family paints a fascinating picture of a close-knit community
<figure><img src="https://images.theconversation.com/files/489930/original/file-20221017-17-4qvy1b.jpg?ixlib=rb-1.1.0&rect=11%2C0%2C1243%2C718&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A Neanderthal father and his daughter.</span> <span class="attribution"><span class="source">Tom Björklund</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Our closest evolutionary relatives, the Neanderthals (<em>Homo neanderthalensis</em>), were once spread across Europe and as far east as the Altai Mountains in southern Siberia.</p>
<p>Yet more than 160 years since the first Neanderthal fossils were unearthed in Europe, little is known about the group size or social organisation of Neanderthal communities.</p>
<p>Using ancient DNA, a <a href="https://www.nature.com/articles/s41586-022-05283-y">new study</a> provides a snapshot of a Neanderthal community frozen in time.</p>
<p>With our colleagues, we show a group of Neanderthals living in the Altai foothills around 54,000 years ago consisted of perhaps 10 to 20 individuals. Many of them were closely related – including a father and his young daughter.</p>
<h2>The easternmost Neanderthals</h2>
<p>The first genetic clues to Neanderthals were obtained <a href="https://www.cell.com/fulltext/S0092-8674(00)80310-4">25 years ago</a> from a fragment of mitochondrial DNA, which is found in cell structures called mitochondria rather than in the cell nucleus.</p>
<p>Subsequent mitochondrial DNA studies and genome-wide nuclear data from 18 individuals have sketched the broad brushstrokes of Neanderthal history, revealing the existence of many genetically distinct groups between about 430,000 and 40,000 years ago.</p>
<p>Our new study is the first to analyse ancient DNA from the teeth and bones of multiple Neanderthals who lived at around the same time. The fossils came from archaeological excavations of Okladnikov Cave in the mid-1980s and Chagyrskaya Cave since 2007.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map showing locations of the caves and a photo of one of them" src="https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=343&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=343&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=343&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=431&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=431&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489936/original/file-20221017-12-8falkc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=431&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Neanderthal DNA was sequenced from fossil remains found at Chagyrskaya Cave (photo) and Okladnikov Cave in southern Siberia.</span>
<span class="attribution"><span class="source">Maciej Krajcarz (map) and Richard Roberts (photo)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These caves were used by Neanderthals as hunting camps. The remains of animals such as bison and horses are abundant, and more than 80 Neanderthal fossils were also found in Chagyrskaya Cave – one of the largest such collections anywhere in the world.</p>
<p>Both sites also contain <a href="https://www.pnas.org/doi/10.1073/pnas.1918047117">distinctive stone tools</a> that bear a striking resemblance to artefacts found at Neanderthal sites in central and eastern Europe.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/stone-tools-reveal-epic-trek-of-nomadic-neanderthals-129886">Stone tools reveal epic trek of nomadic Neanderthals</a>
</strong>
</em>
</p>
<hr>
<h2>Family ties</h2>
<p>To paint a detailed picture of the genetic makeup and relatedness of these Neanderthals, we analysed mitochondrial DNA (which is passed down the female line), Y-chromosomes (passed from father to son) and genome-wide data (inherited from both parents) for 17 Neanderthal fossils – the most ever sequenced in a single study.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A range of bones and teeth on a dark background" src="https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=278&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=278&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=278&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=350&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=350&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489916/original/file-20221017-25-a1wd6b.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=350&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Neanderthal teeth and bones from Chagyrskaya Cave (A, B) and Okladnikov Cave (C) included in our study. The white bar in each panel is 1 cm in length.</span>
<span class="attribution"><span class="source">Bence Viola</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The teeth and bones came from 13 individuals: 11 from Chagyrskaya Cave and two from Okladnikov Cave. Seven of the Neanderthals were male and six were female. Eight were adults and five were children or adolescents.</p>
<p>Among them were the remains of a Neanderthal father and his teenage daughter, as well as a pair of second-degree relatives – a young boy and an adult female, perhaps his cousin, aunt or grandmother.</p>
<p>Although the nearby site of <a href="https://theconversation.com/fresh-clues-to-the-life-and-times-of-the-denisovans-a-little-known-ancient-group-of-humans-110504">Denisova Cave</a> was inhabited by Neanderthals from as early as 200,000 years ago, the Chagyrskaya and Okladnikov Neanderthals are more closely related to European Neanderthals than to the earlier ones at Denisova Cave.</p>
<p>This finding is consistent with a <a href="https://www.pnas.org/doi/10.1073/pnas.2004944117">previous genomic study</a> of a Chagyrskaya Neanderthal and the presence of distinctive stone tools at Chagyrskaya and Okladnikov Caves that closely resemble those found at Neanderthal sites in Europe.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph showing relations among the various species" src="https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=643&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=643&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=643&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=808&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=808&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490089/original/file-20221017-7429-yw50nu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=808&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Phylogenetic tree of mitochondrial DNA sequences showing the evolutionary relationships among the Chagyrskaya (blue) and Okladnikov (orange) Neanderthals included in our study, Neanderthals from Denisova Cave and Europe, and present-day humans from Africa, East Asia and Europe.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We also found the Chagyrskaya Neanderthals share several heteroplasmies – a special kind of mitochondrial DNA variant that typically persists for less than three generations.</p>
<p>Taken together with the evidence for their close family connections, these indicate the Chagyrskaya Neanderthals must have lived – and died – at around the same time.</p>
<h2>On the brink of extinction</h2>
<p>Our analyses also revealed this Neanderthal community had extremely low genetic diversity – consistent with a group size of just 10 to 20 people.</p>
<p>This is much smaller than the genetic diversity recorded for any ancient or present-day human community, and is more like that found among endangered species at risk of extinction, such as <a href="https://www.worldwildlife.org/species/mountain-gorilla">mountain gorillas</a>.</p>
<p>The Chagyrskaya Neanderthals were not a community of hermits, however. We discovered their mitochondrial DNA diversity was much higher than their Y-chromosome diversity, which can be explained by the predominance of female (rather than male) migration between Neanderthal communities.</p>
<p>Did these migrations involve Denisovans, who occupied Denisova Cave repeatedly from at least 250,000 years ago to around 50,000 years ago?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/dirty-secrets-sediment-dna-reveals-a-300-000-year-timeline-of-ancient-and-modern-humans-living-in-siberia-161585">Dirty secrets: sediment DNA reveals a 300,000-year timeline of ancient and modern humans living in Siberia</a>
</strong>
</em>
</p>
<hr>
<p>Denisovans are a sister group to Neanderthals and they interbred at least once. This happened around 100,000 years ago, <a href="https://www.nature.com/articles/d41586-018-06004-0">producing a daughter</a> from a Neanderthal mother and a Denisovan father.</p>
<p>Yet even though Denisovans were present at Denisova Cave at around the same time as the Neanderthals living at Chagyrskaya and Okladnikov Caves, we found no evidence for Denisovan gene flow into these Neanderthals in the 20,000 years leading up to their demise.</p>
<h2>Kindred spirits</h2>
<p>In recent years, multiple lines of evidence have shown Neanderthals possessed <a href="https://theconversation.com/neanderthals-were-no-brutes-research-reveals-they-may-have-been-precision-workers-103858">technical skills</a>, <a href="https://theconversation.com/how-we-discovered-that-neanderthals-could-make-art-92127">cognitive capabilities</a> and <a href="https://www.nature.com/articles/s41559-021-01487-z">symbolic behaviours</a> as impressive as those of our ancient <em>Homo sapiens</em> ancestors.</p>
<p>Our genetic insights add a new social dimension to this picture. They provide a rare glimpse into the close-knit family structure of a Neanderthal community eking out an existence on the eastern frontier of their geographic range, close to the time when their species finally died out.</p><img src="https://counter.theconversation.com/content/192595/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard 'Bert' Roberts receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Laurits Skov does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Ancient DNA from Neanderthal fossils in southern Siberia reveals a small community with close family ties – including a father and his teenage daughter.
Laurits Skov, Postdoctoral research associate, Max Planck Institute for Evolutionary Anthropology
Richard 'Bert' Roberts, Director, ARC Centre of Excellence for Australian Biodiversity and Heritage (CABAH), University of Wollongong
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/175436
2022-02-23T16:03:13Z
2022-02-23T16:03:13Z
Ancient DNA helps reveal social changes in Africa 50,000 years ago that shaped the human story
<figure><img src="https://images.theconversation.com/files/446822/original/file-20220216-3870-1o2qb6l.jpg?ixlib=rb-1.1.0&rect=186%2C0%2C3661%2C2475&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Together with artifacts from the past, ancient DNA can fill in details about our ancient ancestors.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Kondoa_Irangi_Rock_Paintings_(51507918388).jpg">Nina R/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Every person alive on the planet today is descended from people who lived as hunter-gatherers in Africa. </p>
<p>The continent is the cradle of <a href="https://theconversation.com/how-a-handful-of-prehistoric-geniuses-launched-humanitys-technological-revolution-171511">human origins and ingenuity</a>, and <a href="https://theconversation.com/archaeological-discoveries-are-happening-faster-than-ever-before-helping-refine-the-human-story-128743">with each new fossil and archaeological discovery</a>, we learn more about our shared African past. Such research tends to focus on when our species, <em>Homo sapiens</em>, <a href="https://www.scientificamerican.com/article/how-homo-sapiens-became-the-ultimate-invasive-species/">spread out to other landmasses 80,000-60,000 years ago</a>. But what happened in Africa after that, and why don’t we know more about the people who remained?</p>
<p>Our 2022 study, conducted by an interdisciplinary team of 44 researchers based in 12 countries, <a href="https://www.nature.com/articles/s41586-022-04430-9">helps answer these questions</a>. By sequencing and analyzing ancient DNA (aDNA) from people who lived as long ago as 18,000 years, we roughly doubled the age of sequenced aDNA from sub-Saharan Africa. And this genetic information helps <a href="https://scholar.google.com/citations?user=GlrnQDgAAAAJ&hl=en&oi=ao">anthropologists</a> <a href="https://scholar.google.com/citations?user=MQkcYDYAAAAJ&hl=en&oi=ao">like</a> <a href="https://scholar.google.com/citations?user=3QKcZMoAAAAJ&hl=en&oi=ao">us</a> understand more about how modern humans were moving and mingling in Africa long ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="View from above of archaeological excavation" src="https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441914/original/file-20220121-8326-sxvlib.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People took shelter in natural rock overhangs, leaving behind an archaeological record of their daily activities – and sometimes their graves. By digging carefully, archaeologists can connect information from aDNA to information about the social lives of these people.</span>
<span class="attribution"><span class="source">Jacob Davis</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Tracing our human past in Africa</h2>
<p><a href="https://theconversation.com/new-moroccan-fossils-suggest-humans-lived-and-evolved-across-africa-100-000-years-earlier-than-we-thought-78826">Beginning about 300,000 years ago</a>, people in Africa who looked like us – the earliest anatomically modern humans – also started behaving in ways that seem very human. They made <a href="https://www.smithsonianmag.com/science-nature/how-drastic-ecological-change-led-leap-forward-behavior-weapons-and-tools-180976101/">new kinds of stone tools and began transporting raw materials</a> up to 250 miles (400 kilometers), likely through trade networks. By 140,000-120,000 years ago, people made <a href="https://scitechdaily.com/early-humans-used-bone-tools-to-produce-clothing-in-morocco-120000-years-ago/">clothing from animal skins</a> and began to <a href="https://www.smithsonianmag.com/smart-news/worlds-oldest-jewelry-discovered-in-moroccan-cave-180978766/">decorate themselves with pierced marine shell beads</a>. </p>
<p>While early innovations appeared in a patchwork fashion, a more widespread shift happened around 50,000 years ago – around the same time that people started <a href="https://www.nationalgeographic.com/history/article/australia-aboriginal-early-human-evolution-spd">moving into places as distant as Australia</a>. New types of stone and bone tools became common, and people began <a href="https://theconversation.com/the-tiny-ostrich-eggshell-beads-that-tell-the-story-of-africas-past-128577">fashioning and exchanging ostrich eggshell beads</a>. And while most <a href="https://theconversation.com/an-ancient-san-rock-art-mural-in-south-africa-reveals-new-meaning-157177">rock art in Africa</a> is undated and badly weathered, an increase in <a href="https://theconversation.com/what-the-use-of-ochre-tells-us-about-the-capabilities-of-our-african-ancestry-47081">ochre pigment at archaeological sites</a> hints at an explosion of art. </p>
<p>What caused this shift, known as the <a href="https://en.wikipedia.org/wiki/Late_Stone_Age">Later Stone Age</a> transition, has been a longstanding archaeological mystery. Why would certain tools and behaviors, which up until that point had appeared in a piecemeal way across Africa, suddenly become widespread? Did it have something to do with changes in the number of people, or how they interacted? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Nine disc-shaped beads" src="https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441913/original/file-20220121-9541-bx79fs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Beads made from ostrich eggshell were hot trade items and can show the extent of ancient social networks.</span>
<span class="attribution"><span class="source">Jennifer Miller</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>The challenge of accessing the deep past</h2>
<p>Archaeologists reconstruct human behavior in the past mainly through things people left behind – remains of their meals, tools, ornaments and <a href="https://theconversation.com/how-we-discovered-the-oldest-human-burial-in-africa-and-what-it-tells-us-about-our-ancestors-160122">sometimes even their bodies</a>. These records may accumulate over thousands of years, creating views of daily livelihoods that are really averages over long periods of time. However, it’s hard to study ancient demography, or how populations changed, from the archaeological record alone. </p>
<p>This is where DNA can help. When combined with evidence from archaeology, linguistics and oral and written history, scientists can piece together how people moved and interacted based on which groups share genetic similarities.</p>
<p>But DNA from living people can’t tell the whole story. African populations have been transformed over the past 5,000 years by the <a href="https://theconversation.com/ancient-dna-is-revealing-the-origins-of-livestock-herding-in-africa-114387">spread of herding and farming</a>, the <a href="https://theconversation.com/how-we-recreated-a-lost-african-city-with-laser-technology-92852">development of cities</a>, <a href="https://theconversation.com/archaeology-shows-how-ancient-african-societies-managed-pandemics-138217">ancient pandemics</a> and the ravages of <a href="https://theconversation.com/a-digital-archive-of-slave-voyages-details-the-largest-forced-migration-in-history-74902">colonialism and slavery</a>. These processes caused <a href="https://www.nytimes.com/2020/02/12/science/west-africa-ancient-humans.html">some lineages to vanish</a> and <a href="https://theconversation.com/mitochondrial-dna-reveals-unexpected-ancestral-connections-122053">brought others together</a>, forming new populations. </p>
<p>Using present-day DNA to reconstruct ancient genetic landscapes is like reading a letter that was left out in the rain: some words are there but blurred, and some are gone completely. Researchers need ancient DNA from archaeological human remains to explore human diversity in different places and times and to understand what factors shaped it.</p>
<p>Unfortunately, aDNA from Africa is particularly hard to recover because the continent straddles the equator and heat and humidity degrade DNA. While the <a href="https://www.scientificamerican.com/article/oldest-ancient-human-dna-details-dawn-of-neandertals/">oldest aDNA from Eurasia is roughly 400,000 years old</a>, all sequences from sub-Saharan Africa to date have been younger than around 9,000 years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map with markers showing distribution of ancient DNA data in Africa, and the world." src="https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=625&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=625&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=625&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=785&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=785&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444879/original/file-20220207-47158-11n9ym1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=785&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map of all published ancient genomes, with black dots scaled to the number of individuals’ genomes. Blue dots indicate Later Stone Age foragers comparable to those in our study. Red stars indicate individuals reported for the first time in our study. Inset map underscores the gap between Africa and other parts of the world in terms of published ancient genomes. Ancient DNA preserved between the Tropics of Cancer and Capricorn is rare.</span>
<span class="attribution"><span class="source">Mary Prendergast; basemaps by Natural Earth</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Breaking the ‘tropical ceiling’</h2>
<p>Because each person carries genetic legacies inherited from generations of their ancestors, our team was able to use DNA from individuals who lived between 18,000-400 years ago to explore how people interacted as far back as the last 80,000-50,000 years. This allowed us, for the first time, to test whether demographic change played a role in the Later Stone Age transition. </p>
<p><a href="https://www.nature.com/articles/s41586-022-04430-9">Our team sequenced aDNA</a> from six individuals buried in what are now Tanzania, Malawi and Zambia. We compared these sequences to previously studied aDNA from 28 individuals buried at sites stretching from Cameroon to Ethiopia and down to South Africa. We also generated new and improved DNA data for 15 of these people, trying to extract as much information as possible from the small handful of ancient African individuals whose DNA is preserved well enough to study.</p>
<p>This created the largest genetic dataset so far for studying the population history of ancient African foragers – people who hunted, gathered or fished. We used it to explore population structures that existed prior to the sweeping changes of the past few thousand years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Museum building, palm trees" src="https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444614/original/file-20220205-23-d1055k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">National Museum of Tanzania in Dar es Salaam. Ancient DNA studies in Africa are made possible by the efforts of curators to protect and preserve remains in tropical conditions.</span>
<span class="attribution"><span class="source">Mary Prendergast</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>DNA weighs in on a longstanding debate</h2>
<p>We found that people did in fact change how they moved and interacted around the Later Stone Age transition.</p>
<p>Despite being separated by thousands of miles and years, all the ancient individuals in this study were descended from the same three populations related to ancient and present-day eastern, southern and central Africans. The presence of eastern African ancestry as far south as Zambia, and southern African ancestry as far north as Kenya, indicates that people were moving long distances and having children with people located far away from where they were born. The only way this population structure could have emerged is if people were moving long distances over many millennia. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Lush African landscape" src="https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446008/original/file-20220211-21-gafkub.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Genetic data now suggests that people moved and mingled across the eastern African Rift Valley during the Ice Ages.</span>
<span class="attribution"><span class="source">Elizabeth Sawchuk</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Additionally, our research showed that almost all ancient eastern Africans shared an unexpectedly high number of genetic variations with hunter-gatherers who today live in central African rainforests, making ancient eastern Africa truly a genetic melting pot. We could tell that this mixing and moving happened after about 50,000 years ago, when there was a major split in central African forager populations.</p>
<p>We also noted that the individuals in our study were genetically most like only their closest geographic neighbors. This tells us that after around 20,000 years ago, the foragers in some African regions were almost exclusively finding their partners locally. This practice must have been extremely strong and persisted for a very long time, as our results show that some groups remained genetically independent of their neighbors over several thousand years. It was especially clear in Malawi and Zambia, where the only close relationships we detected were between people buried around the same time at the same sites. </p>
<p>We don’t know why people began “living locally” again. Changing environments as the last Ice Age peaked and waned between about 26,000-11,500 years ago may have made it more economical to forage closer to home, or perhaps elaborate exchange networks reduced the need for people to travel with objects.</p>
<p>Alternatively, new group identities may have emerged, restructuring marriage rules. If so, we would expect to see artifacts and other traditions like rock art diversify, with specific types clumped into different regions. Indeed, <a href="https://www.theguardian.com/science/2022/jan/16/trail-of-african-bling-reveals-50000-year-old-social-network">this is exactly what archaeologists find</a> – a trend known as regionalization. Now we know that this phenomenon not only affected cultural traditions, but also the flow of genes. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="workers at a table sort tiny items by hand" src="https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446872/original/file-20220216-20-cuzc12.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Recovering and sorting archaeological remains is a slow and laborious process, where even small fragments can tell big stories.</span>
<span class="attribution"><span class="source">Chelsea Smith</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>New data, new questions</h2>
<p>As always, <a href="https://theconversation.com/ancient-dna-is-a-powerful-tool-for-studying-the-past-when-archaeologists-and-geneticists-work-together-111127">aDNA research raises as many questions as answers</a>. Finding central African ancestry throughout eastern and southern Africa prompts anthropologists to reconsider how interconnected these regions were in the distant past. This is important because central Africa has remained archaeologically understudied, in part because of political, economic and logistical challenges that make research there difficult. </p>
<p>Additionally, while genetic evidence supports a major demographic transition in Africa after 50,000 years ago, we still don’t know the key drivers. Determining what triggered the Later Stone Age transition will require closer examination of regional environmental, archaeological and genetic records to understand how this process unfolded across sub-Saharan Africa.</p>
<p>Finally, this study is a stark reminder that researchers still have <a href="https://theconversation.com/lesson-from-brazil-museums-are-not-forever-102692">much to learn from ancient individuals and artifacts</a> held in African museums, and highlights the <a href="https://theconversation.com/what-its-like-curating-ancient-fossils-a-palaeontologist-shares-her-story-96555">critical role of the curators</a> who steward these collections. While some human remains in this study were recovered within the past decade, others have been in museums for a half-century.</p>
<p>Even though technological advances are pushing back the time limits for aDNA, it is important to remember that scientists have only just begun to understand human diversity in Africa, past and present.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/GUau26szdzA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/175436/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth Sawchuk receives funding from the Social Sciences and Humanities Research Council of Canada. </span></em></p><p class="fine-print"><em><span>Jessica Thompson has received funding from the Leakey Foundation, National Geographic Society, Wenner-Gren Foundation, Australian Research Council, National Science Foundation, and Hyde Family Foundation. </span></em></p><p class="fine-print"><em><span>Mary Prendergast does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
A new study doubles the age of ancient DNA in sub-Saharan Africa, revealing how people moved, mingled and had children together over the last 50,000 years.
Elizabeth Sawchuk, Banting Postdoctoral Fellow and Adjunct Professor of Anthropology, University of Alberta
Jessica Thompson, Assistant Professor of Anthropology, Yale University
Mary Prendergast, Associate Professor of Anthropology, Rice University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/176648
2022-02-09T19:02:36Z
2022-02-09T19:02:36Z
New research suggests modern humans lived in Europe 10,000 years earlier than previously thought, in Neanderthal territories
<figure><img src="https://images.theconversation.com/files/445221/original/file-20220208-14-hacfd6.jpg?ixlib=rb-1.1.0&rect=4%2C649%2C3302%2C2290&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Grotte Mandrin rock shelter saw repeated use by Neanderthals and modern humans over millennia.</span> <span class="attribution"><span class="source">Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Perched about 325 feet (100 meters) up the slopes of the Prealps in southern France, a humble rock shelter looks out over the Rhône River Valley. It’s a strategic point on the landscape, as here the Rhône flows through a narrows between two mountain ranges. For millennia, inhabitants of the rock shelter would have had commanding views of herds of animals migrating between the Mediterranean region and the plains of northern Europe, today replaced by TGV trains and up to 180,000 vehicles per day on one of the busiest highways on the continent.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woodsy landscape with rock outcropping against blue sky" src="https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=164&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=164&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=164&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=206&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=206&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445214/original/file-20220208-36884-116o8hb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=206&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Grotte Mandrin is somewhat camouflaged as a rock outcropping when viewed from a distance.</span>
<span class="attribution"><span class="source">Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The site, recognized in the 1960s and named Grotte Mandrin after French folk hero Louis Mandrin, has been a valued location for over 100,000 years. The stone artifacts and animal bones left behind by ancient hunter-gatherers from the <a href="https://www.britannica.com/event/Paleolithic-Period">Paleolithic period</a> were quickly covered by the glacial dust that blew from the north on the famous mistral winds, keeping the remains well preserved. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="people kneeling on ground, working in the dirt" src="https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=785&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=785&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=785&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=986&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=986&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445223/original/file-20220208-13-1ea5wyf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=986&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">View of the excavations at the entrance of Grotte Mandrin.</span>
<span class="attribution"><span class="source">Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><a href="https://scholar.google.com/citations?user=-RkV2cEAAAAJ&hl=en&oi=ao">Since 1990, our</a> <a href="https://scholar.google.com/citations?user=NuaVUcwAAAAJ&hl=en&oi=ao">research</a> <a href="https://scholar.google.com/citations?user=Oj2sSG0AAAAJ&hl=en&oi=ao">team</a> <a href="https://www.researchgate.net/scientific-contributions/Laure-Metz-72173746">has</a> been carefully investigating the uppermost 10 feet (3 meters) of sediment on the cave floor. Based on artifacts and tooth fossils, we believe that Mandrin rewrites the consensus story about when modern humans first made their way to Europe.</p>
<p>Human origins researchers have generally agreed that between 300,000 and 40,000 years ago, Neanderthals and their ancestors occupied Europe. From time to time during that period, they had contact with modern humans in the Levant and parts of Asia. Then around 48,000 to 45,000 years ago, modern humans – essentially us – <a href="https://doi.org/10.1016/j.quascirev.2014.08.011">expanded throughout the rest of the world</a>, and Neanderthals and all other archaic humans disappeared.</p>
<p>In the journal Science Advances, <a href="https://doi.org/10.1126/sciadv.abj9496">we describe our discovery</a> of evidence that modern humans lived 54,000 years ago at Mandrin. That’s some 10 millennia earlier than our species was previously thought to be in Europe and over a thousand miles west (1,700 kilometers) from the <a href="https://doi.org/10.1038/s41586-020-2259-z">next-oldest known site, in Bulgaria</a>. And fascinatingly, Neanderthals appear to have used the cave both before and after the modern human occupation.</p>
<h2>Clues from tiny stone points and a tooth</h2>
<p>The first curious finding to emerge during the initial decade of Grotte Mandrin excavations were 1,500 tiny triangular stone points identified in what we labeled Layer E. Some less than half an inch (1 cm) in length, these points resemble arrowheads. They have no technological precursors or successors in the 11 surrounding archaeological layers of Neanderthal artifacts in the cave.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Triangular stone points against black background." src="https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=563&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=563&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=563&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=708&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=708&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445229/original/file-20220208-21-1y943e2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=708&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These Neronian points have no equivalent technology among the Neanderthal groups that lived before and after the arrival of the first modern humans in Grotte Mandrin.</span>
<span class="attribution"><span class="source">Laure Metz and Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Who made them? A handful of other sites in the middle Rhône Valley also contain these tiny points. But those sites were excavated long ago with pickaxes, making it hard to tell whether the points showed up abruptly or gradually over time, perhaps with Neanderthals having developed the methods to make them. In 2004, one of us, Ludovic Slimak, <a href="https://doi.org/10.1016/j.jas.2008.02.005">named this distinctive tradition “Neronian”</a> after the nearby site where such tiny points were first excavated.</p>
<p>Without more local sites for comparison, two of us, Laure Metz and Slimak, looked to a region where modern humans were definitely living by 54,000 years ago: the Eastern Mediterranean. In particular, <a href="https://doi.org/10.1073/pnas.1501529112">the site of Ksar Akil</a> near Beirut preserves what may be the longest and richest Paleolithic record in all Eurasia. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map of Mediterranean region with sketches of stone points superimposed" src="https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=407&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=407&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=407&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=511&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=511&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445450/original/file-20220209-23-39hgqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=511&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On opposite sides of the Mediterranean, similar stone points were made by <em>Homo sapiens</em> around the same time.</span>
<span class="attribution"><span class="source">Laure Metz and Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our analyses of the stone artifacts from Ksar Akil show a similarly aged sediment layer with tiny points of the same size and made in the same technical traditions as those of Mandrin. This similarity strongly suggested that the Neronian artifacts were made not by Neanderthals, but rather by a group of modern human explorers who entered the region much earlier than we had expected.</p>
<p>The final piece of the puzzle came in 2018, when one of us, <a href="https://www.pacea.u-bordeaux.fr/zanolli-clament/">Clément Zanolli</a>, analyzed the nine hominin teeth we’d found throughout the different layers during excavation. <a href="https://doi.org/10.1126/sciadv.abj9496">Through painstaking analyses</a> using CT scans and comparisons with hundreds of other fossils, we were able to determine that the Mandrin E tooth, a single baby tooth from a child between 2 and 6 years of age, came from an early modern human and cannot be from a Neanderthal.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="fossil teeth and stone tools found in the same layer are side by side" src="https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445239/original/file-20220208-23-1r0tzuu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cultural and anthropological evidence in Grotte Mandrin show the arrival of <em>Homo sapiens</em> in the heart of Neanderthal territories.</span>
<span class="attribution"><span class="source">Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Based on the stone point technologies and their contexts in other sites, along with this fossil evidence, we conclude that the makers of the Neronian points in Grotte Mandrin were modern humans.</p>
<h2>Reading campfire soot layers like treerings</h2>
<p>But the discoveries from Mandrin don’t stop there. Throughout the site’s layers there are fragments of the shelter walls and roof that have fallen off and been buried with the fossils and artifacts.</p>
<p>When Neanderthals and modern humans made fires in the site, the smoke would leave a layer of soot on those surfaces. Then the following season a thin layer of calcium carbonate called speleothem would cover it over. This cycle was repeated over and over.</p>
<p>[<em>Like what you’ve read? Want more?</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-likethis">Sign up for The Conversation’s daily newsletter</a>.]</p>
<p>We first discovered these sooted vault fragments in 2006, and the team recovered thousands, year after year, in every archaeological layer of Mandrin. <a href="https://halshs.archives-ouvertes.fr/halshs-01610057/document">A decade of work</a> by team member <a href="https://theconversation.com/profiles/segolene-vandevelde-475892">Ségolène Vandevelde</a> has shown that these patterns can be read like tree rings to tell us with what frequency and duration the groups visited the site, demonstrating that human groups came to Mandrin some 500 times over 80,000 years. </p>
<p>Vandevelde was then able to determine how much time separated the last Neanderthal fire from the first modern human fire in the cave, showing that it was only a maximum of a year between Neanderthals using Grotte Mandrin and modern humans moving in.</p>
<p>After the modern humans occupied Mandrin annually for some 40 years, one or two generations, they disappeared just as quickly and mysteriously as they had appeared. Neanderthals then regularly reoccupied Mandrin over the following 12,000 years. </p>
<h2>Multiple human species sharing the landscape</h2>
<p>How did these modern humans arrive so early in Western Europe?</p>
<p><a href="https://doi.org/10.1038/nature22968">Archaeological evidence from Australia</a> shows that modern humans reached that continent by as early as 65,000 years ago. Of course they would have needed a boat to cross the open ocean to get there. It therefore isn’t a stretch to assume that people in the Mediterranean had access to boat technologies 54,000 years ago and used them to explore along the coastlines of this contained sea.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="thin stone against dirt ground" src="https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=653&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=653&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=653&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=820&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=820&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445244/original/file-20220208-25317-1toppl8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=820&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">View of a long flint blade emerging from the sediment of Grotte Mandrin.</span>
<span class="attribution"><span class="source">Ludovic Slimak</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We know from the source locations of the flint used to make the artifacts in Grotte Mandrin that both Neanderthals and modern humans roamed widely, <a href="https://doi.org/10.1016/j.quascirev.2018.12.019">about 60 miles (100 km) in all directions</a> around the site.</p>
<p>How did the modern humans learn about all these stone resources over such a large, varied landscape in such a short time? Did they have relationships with the Neanderthals, who could have exchanged information or acted as guides? Was this a moment when the two groups interbred?</p>
<p>Our ongoing work at Mandrin will shed light on these and other questions about our earliest ancestors in Europe.</p><img src="https://counter.theconversation.com/content/176648/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Stone artifacts and a fossil tooth point to Homo sapiens living at Grotte Mandrin 54,000 years ago, at a time when Neanderthals were still living in Europe.
Ludovic Slimak, CNRS Permanent Member, Université Toulouse – Jean Jaurès
Clément Zanolli, Paleoanthropologist, Université de Bordeaux
Jason E. Lewis, Lecturer of Anthropology and Assistant Director of the Turkana Basin Institute, Stony Brook University (The State University of New York)
Laure Metz, Archaeologist at Aix-Marseille Université and Affiliated Researcher in Anthropology, University of Connecticut
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/165516
2021-11-01T12:25:40Z
2021-11-01T12:25:40Z
When and how was walking invented?
<figure><img src="https://images.theconversation.com/files/425087/original/file-20211006-27-14gw1jh.jpeg?ixlib=rb-1.1.0&rect=9%2C9%2C2113%2C1712&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Three upright walkers, including Lucy (center) and two specimens of *Australopithecus sediba*, a human ancestor from South Africa dating back nearly 2 million years.</span> <span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/6/6e/Australopithecus_sediba_and_Lucy.jpg">Image compiled by Peter Schmid and courtesy of Lee R. Berger/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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<p><em>Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>When and how was walking invented? — Rayssa, 11, Newark, New Jersey</strong></p>
</blockquote>
<hr>
<p>This is an important question because many anthropologists see bipedalism – which means walking on two legs – as one of the defining characteristics of “hominins,” or modern humans, and their ancestors. It is difficult to give a simple answer, though, because bipedalism did not just appear one day. It went through a gradual evolution that began <a href="https://www.smithsonianmag.com/science-nature/becoming-human-the-evolution-of-walking-upright-13837658/">many millions of years ago</a>. </p>
<p>Of course there are no video clips of the first person ever walking upright. So how do scientists try to answer questions about how people moved in the very ancient past? Luckily, the shape of a creature’s bones and the way they fit together can tell the story of how that body moved when it was alive. And anthropologists can find other evidence in the landscape that indicates how ancient people walked.</p>
<p>In 1994, the first fossils of an unknown hominin were found in Ethiopia. The anthropologists who found the remains called the new discovery, an adult female individual, <em>Ardipithecus ramidus</em>, nicknamed “Ardi.” Over the next 10 years, more than 100 fossils from Ardi’s species were found and dated to between <a href="https://humanorigins.si.edu/evidence/human-fossils/species/ardipithecus-ramidus">4.2 million and 4.4 million years old</a>.</p>
<p>When scientists examined this collection of bones, they identified certain characteristics that indicated bipedalism. The foot, for example, had a structure that allowed the kind of toe push-off that we have today, which four-legged apes do not have. The shape of the pelvic bones, how the legs were positioned under the pelvis and how the leg bones fit together all suggested upright walking too. It may be that Ardi did not walk exactly as we do today, but bipedalism as the normal way of movement does seem to be characteristic of these fossils from <a href="https://doi.org/10.1073/pnas.1403659111">as early as 4.4 million years ago</a>. </p>
<p>Anthropologists had already found the nearly 40%-complete skeleton of a hominin species that lived about <a href="https://www.nationalgeographic.org/thisday/nov24/lucy-discovered-africa/">a million years after Ardi</a>, also in Ethiopia. Because of its similarity to other fossils found in southern and eastern Africa, they called it <em>Australopithecus afarensis</em>, which in Latin means “southern ape from the afar region.” This individual was female, so they nicknamed it “Lucy” after a song by the Beatles that was popular at the time. </p>
<p>Many more fossils from this species – more than 300 individuals – have been added to the group, and today researchers know quite a lot about Lucy and her relatives. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up image of face of a model based on Lucy and other _A. afarensis_ fossils" src="https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=655&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=655&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=655&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=823&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=823&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425079/original/file-20211006-13-cagg43.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=823&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An image of a model based on Lucy and other <em>Australopithecus afarensis</em> skeleton fossils found in East Africa in 1974.</span>
<span class="attribution"><a class="source" href="https://media.nationalgeographic.org/assets/photos/000/346/34648_r646x705.jpg?3b599dbcd9a917b42bcb750283a52c57221d8012">Smithsonian</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Lucy had a partial but well-preserved pelvis, which was how anthropologists knew she was female. The pelvis and upper leg bones fit together in a way that showed <a href="https://www.nhm.ac.uk/discover/australopithecus-afarensis-lucy-species.html">she walked upright on two legs</a>. No feet bones were preserved, but later discoveries of <em>A. afarensis</em> do include feet and indicate bipedal walking as well.</p>
<p>In addition to fossil remains, scientists found <a href="https://doi.org/10.7554/eLife.19568">other remarkable evidence</a> for how Lucy’s species moved at the Laetoli site in Tanzania. Beneath a layer of volcanic ash dating to 3.6 million years ago, anthropologists found fossilized footprints in what had once been a wet surface of volcanic ash. The tracks go along for almost 100 feet, and 70 individual prints indicate the presence of at least three individuals walking upright on two feet. Given the presumed age, the makers were likely <em>Australopithecus afarensis</em>. </p>
<p>The tracks prove that these hominins walked on two legs, but the gait seems to be a bit different from ours today. Still, Laetoli provides <a href="https://humanorigins.si.edu/evidence/behavior/footprints/laetoli-footprint-trails">solid evidence for bipedalism</a> 3.5 million years ago.</p>
<p>A hominin whose anatomy was so like our own that we can say it walked as we do did not appear in Africa until 1.8 million years ago. <em>Homo erectus</em> was the first to have the long legs and shorter arms that would have made it possible to walk, run and <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-erectus">move about Earth’s landscapes as we do today</a>. <em>Homo erectus</em> also had a much larger brain than did earlier bipedal hominins and made and used stone tools <a href="https://www.thoughtco.com/acheulean-tradition-169924">called Acheulean implements</a>. Anthropologists consider <em>Homo erectus</em> our close relative and an early member of our own genus, <em>Homo</em>.</p>
<p>So, as you can see, human walking took a very long time to develop. It appeared in Africa more than 4.4 million years ago, long before tool-making appeared.</p>
<p>Why did hominins walk upright? Perhaps it allowed them to see predators more easily, or to run faster, or maybe the environment changed and there were fewer trees to climb as earlier hominins did. </p>
<p>In any case, humans and their ancestors began to walk very early in their evolutionary history. Even though bipedalism came before tool-making, an upright posture freed the hands to make and use tools, which ultimately became one of the hallmarks of humans like us.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/165516/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jan Simek has received funding from the LSB Leakey Foundation, the NSF, the Wenner-Gren Foundation and the National Geographic Society.</span></em></p>
Walking has taken a very long time to develop, with evidence of bipedalism among early humans in Africa roughly 4.4 million years ago.
Jan Simek, Professor of Anthropology, University of Tennessee
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/163338
2021-07-07T19:51:10Z
2021-07-07T19:51:10Z
Ancient skulls show Anglo-Saxon identity was more cultural than genetic
<figure><img src="https://images.theconversation.com/files/409737/original/file-20210705-21-fuxj7s.jpg?ixlib=rb-1.1.0&rect=0%2C34%2C4601%2C2552&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An Anglo-Saxon burial mound in Taplow Court, England.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Scholars have long been fascinated by <a href="https://www.britannica.com/place/United-Kingdom/Anglo-Saxon-England">the Anglo-Saxon period of British history</a>, which spans approximately 600 years, from the end of Roman rule in around AD 410 to the start of the Norman conquest in 1066. Unfortunately, because very few contemporary documents are available, a number of important questions about the early part of the period remain unanswered. One of these is: “Who were the Anglo-Saxons?”</p>
<p>There is general agreement that their origins can be traced to a migration of Germanic-speaking people from mainland northwest Europe that began in the early fifth century. But the number of individuals who settled in the British Isles and the nature of their relationship with the pre-existing inhabitants, especially the Romano-British, <a href="https://www.simonandschuster.com/books/The-Anglo-Saxons/Marc-Morris/9781643133126">is still unclear</a>.</p>
<h2>Conflicting evidence</h2>
<p>Uncertainty persists because two of the main lines of evidence contradict each other. Historical documents such as Gildas’ <a href="https://www.bl.uk/collection-items/gildas-the-ruin-of-britain#"><em>The Ruin of Britain</em></a>, Bede’s <a href="https://www.britannica.com/topic/Ecclesiastical-History-of-the-English-People"><em>The Ecclesiastical History of the English People</em></a> and <a href="http://www.bl.uk/learning/timeline/item126532.html"><em>The Anglo-Saxon Chronicle</em></a> suggest not only that the incomers were numerous, but also that they more or less completely replaced the Romano-British, killing some and pushing the rest to the peripheries.</p>
<p>This picture is not supported by the results of isotopic analyses. Isotopes are different forms of a chemical element that can be distinguished by their atomic masses and physical properties. Isotopic analysis can help determine where an individual grew up.</p>
<p>When isotopes of strontium and oxygen extracted from Anglo-Saxon skeletons have been compared, <a href="https://doi.org/10.1016/j.jas.2013.10.025">they have pointed to only a few of the individuals having grown up in mainland Europe</a>. This has been interpreted as evidence that the Romano-British were not replaced. Rather, they adopted a new language and set of values, beliefs and cultural practices from a relatively small number of incomers.</p>
<p>Frustratingly, genetic studies have not been able to clarify the debate. They have returned such a wide range of estimates of the percentage of mainland European ancestry in England that they can support either hypothesis.</p>
<h2>A new line of evidence</h2>
<p>Recently, we published a study in which we used a new line of evidence to investigate the issue: <a href="https://doi.org/10.1371/journal.pone.0252477">the three-dimensional (3D) shape of the base of the skull, which bioarchaeologists usually call the cranial base or basicranium</a>.</p>
<p><a href="https://doi.org/10.1002/ar.a.20395">Previous research</a> has shown that when the basicranium is analysed in 3D, its shape can be used to track relationships among human populations in a similar way to DNA. We reasoned that collecting such data from Anglo-Saxon skulls and comparing them to similar data from the two potential source regions might shed light on the composition of the Anglo-Saxon population.</p>
<p>Our Anglo-Saxon sample comprised 89 individuals from five cemeteries in the English counties of Cambridgeshire, Suffolk and Kent. Three of the cemeteries date to the Early Anglo-Saxon Period (AD 410-660), while the other two date to the Middle Anglo-Saxon Period (AD 660-889). We also collected data on 101 pre-Medieval skeletons from two sites in southern England and 46 individuals from various sites in Denmark that date to the Iron Age (800 BC-AD 399).</p>
<p>To obtain the landmark data, we employed a technique called photogrammetry. We imported 200 photos of each of the 236 skulls (minus the lower jaw) into a software program to create a high-resolution 3D model of each skull. We then used another software program to collect the 3D coordinates of a series of landmarks on the cranial base of each individual.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three images of a skull from different perspectives" src="https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=330&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=330&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409739/original/file-20210705-126484-xcr73h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=330&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Location of the landmarks used in the present study.</span>
<span class="attribution"><span class="source">(Kimberly Plomp)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Indications of mixed ancestry</h2>
<p>Once we had collected the data, we used a set of statistical techniques called geometric morphometrics (GM) to identify similarities and differences in shape among the four groups: Early Anglo-Saxons, Middle Anglo-Saxons, Pre-Medieval British and Pre-Medieval Danish. </p>
<p>Developed in the 1980s, GM has long been an important tool in the study of human evolution, but it has only recently been embraced by bioarchaeologists. GM allows patterns of shape variation to be investigated within a well-understood statistical framework and yields easily interpreted numerical and visual results. In our GM analyses, Anglo-Saxon skulls that shared more similarities with the pre-Medieval British skeletons were considered to have local ancestry, while those that were more similar to the Danish skeletons were deemed to have mainland European ancestry.</p>
<p>The results we obtained suggested a substantial difference between the Early Anglo-Saxon Period sample and the Middle Anglo-Saxon Period. We found that between 66 and 75 per cent of the Early Anglo-Saxon individuals were of mainland European ancestry, while between 25 and 30 per cent were of local ancestry. In contrast, we found that 50 to 70 per cent of the Middle Anglo-Saxon Period individuals were of local ancestry, while 30 to 50 per cent were of mainland European ancestry.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A researcher holding a camera takes a photo of a skull — a skeleton and a bookcase in the background" src="https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=803&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=803&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=803&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1009&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1009&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409738/original/file-20210705-126293-y4pmep.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1009&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the authors, Kimberly Plomp, photographing a skull to demonstrate the initial stage of photogrammetry.</span>
<span class="attribution"><span class="source">(Kimberly Plomp)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While our estimates of the percentage of Anglo-Saxons who had mainland European ancestry fall comfortably within the range of estimates derived from genetic data, they contradict the picture painted by both the historical documents and the isotopic evidence. Specifically, our estimates suggest that there was greater persistence of the Romano-British population than the historical documents claim, and a larger number of immigrants than the isotope evidence has been taken to indicate.</p>
<p>We think these discrepancies can be explained relatively easily. It seems likely that the mismatch between our results and the historical documents relates to the fact that the documents were written long after — in some cases, several hundred years after — the migration, and therefore are of questionable accuracy, <a href="https://doi.org/10.1098/rspb.2006.3627">which a number of scholars have argued</a>.</p>
<p>We suspect the difference between our results and the isotopes may be the consequence of a misunderstanding. While strontium and oxygen isotopes are informative about where an individual grew up, they don’t tell us about a person’s ancestry. Hence, it is feasible that some, if not all, of the individuals with local isotopic signatures were second-generation immigrants — that is, their parents originated in mainland Europe but they themselves were born and raised in the British Isles.</p>
<h2>Language and culture, not genetics</h2>
<p>There are several potential explanations for the change in composition of the Anglo-Saxon population between the Early Anglo-Saxon Period and the Middle Anglo-Saxon Period, but we think the most likely is that there was an increase in the number of local people adopting an Anglo-Saxon identity through time.</p>
<p>This could have been because being Anglo-Saxon was perceived as higher status than being Romano-British. Alternatively, it could simply have been a consequence of people randomly copying one another. This process, which is known as “cultural drift,” has been <a href="https://doi.org/10.1098/rsbl.2003.0045">shown to be able to account for a number of cultural patterns in recent history</a>.</p>
<p>Regardless of the cause of the change in composition, it is clear from our results that being an Anglo-Saxon was more a matter of language and culture than genetics. </p>
<p>Interestingly, this echoes results obtained in <a href="https://doi.org/10.1038/s41586-020-2688-8">the largest ancient DNA study of Vikings published to date</a>. In this study, a number of individuals who were buried as Vikings were found to be of local ancestry, which suggests that being a Viking was also a linguistic and cultural phenomenon rather than a genetic one.</p>
<p>The Anglo-Saxons and Vikings are often viewed in racial terms, with common biological descent deemed to be a key aspect of both groups. However, the results of our study and the Viking DNA one indicate that shared descent was not a requirement for membership of either group. </p>
<p>Instead, it appears that the Anglo-Saxons were a group of individuals of diverse ancestries who shared a common language and culture. The same holds for the Vikings. The Anglo-Saxons and Vikings were, in other words, strikingly similar to the multiracial societies of contemporary northern Europe.</p><img src="https://counter.theconversation.com/content/163338/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Collard receives funding from the Social Sciences and Humanities Research Council of Canada, the Canada Research Chairs Program, the Canada Foundation for Innovation, the British Columbia Knowledge Development Fund, and Simon Fraser University.
</span></em></p><p class="fine-print"><em><span>Kimberly Plomp receives funding from the European Union’s Marie Skłodowska-Curie Actions
program, the Wenner Gren Foundation, and MITACS. </span></em></p><p class="fine-print"><em><span>Keith Dobney does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
New analysis of Anglo-Saxon skulls suggests that being an Anglo-Saxon was a matter of language and culture, and not genetics.
Mark Collard, Canada Research Chair in Human Evolutionary Studies, and Professor of Archaeology, Simon Fraser University
Keith Dobney, Chair professor, Archaeology, University of Sydney
Kimberly Plomp, Postdoctoral Researcher, Human Evolutionary Studies, Simon Fraser University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/158574
2021-05-05T18:06:48Z
2021-05-05T18:06:48Z
Early humans used fire to permanently change the landscape tens of thousands of years ago in Stone Age Africa
<figure><img src="https://images.theconversation.com/files/398430/original/file-20210503-13-nd6j8k.JPG?ixlib=rb-1.1.0&rect=0%2C179%2C4608%2C3269&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Today the shoreline of Lake Malawi is open, not forested the way it was before ancient humans started modifying the landscape.</span> <span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Fields of rust-colored soil, spindly cassava, small farms and villages dot the landscape. Dust and smoke blur the mountains visible beyond massive Lake Malawi. Here in tropical Africa, you can’t escape the signs of human presence.</p>
<p>How far back in time would you need to go in this place to discover an entirely natural environment?</p>
<p>Our work has shown that it would be a very long time indeed – <a href="https://advances.sciencemag.org/content/7/19/eabf9776">at least 85,000 years</a>, eight times earlier than the <a href="https://doi.org/10.1126/science.aax1192">world’s first land transformations via agriculture</a>.</p>
<p><a href="https://scholar.google.com/citations?user=MQkcYDYAAAAJ&hl=en&oi=ao">We</a> <a href="https://scholar.google.com/citations?user=kNBySP0AAAAJ&hl=en&oi=ao">are</a> <a href="https://scholar.google.com/citations?user=ZGB_9bQAAAAJ&hl=en&oi=ao">part</a> of an interdisciplinary collaboration between archaeologists who study past human behavior, geochronologists who study the timing of landscape change and paleoenvironmental scientists who study ancient environments. By combining evidence from these research specialities, we have identified an instance in the very distant past of early humans bending environments to suit their needs. In doing so, they transformed the landscape around them in ways still visible today.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="people excavate stone tools below the ground's surface" src="https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395547/original/file-20210417-17-gv4vry.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Crew members excavate artifacts at a site in Karonga, Malawi, where stone tools are buried more than 3 feet (1 meter) below the modern ground surface.</span>
<span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Digging for behavioral and environmental clues</h2>
<p>The dry season is the best time to do archaeological fieldwork here, and finding sites is easy. Most places we dig in these red soils, we find stone artifacts. They are evidence that someone sat and skillfully broke stones to create edges so sharp they can still draw blood. Many of these stone tools can be fit back together, reconstructing a single action by a single person, from tens of thousands of years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="stone tools paired together" src="https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=520&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=520&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395548/original/file-20210417-13-4zrut7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=520&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Middle Stone Age artifacts, some of which can be fit back together.</span>
<span class="attribution"><a class="source" href="https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.abf4098">Sheila Nightingale</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>So far we’ve recovered more than 45,000 stone artifacts here, buried many feet (1 to 7 meters) below the surface of the ground. The sites we are excavating date to a time ranging from about 315,000 to 30,000 years ago known as the Middle Stone Age. This was also a period in Africa when innovations in human behavior and creativity pop up frequently – and <a href="https://doi.org/10.1038/s41586-021-03419-0">earlier than anywhere else in the world</a>. </p>
<p>How did these artifacts get buried? Why are there so many of them? And what were these ancient hunter-gatherers doing as they made them? To answer these questions, we needed to figure out more about what was happening in this place during their time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="barge with drill floats in the distance on lake water" src="https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395549/original/file-20210417-13-90z5s9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Viphya drill barge on Lake Malawi, where researchers braved waterspouts and lake fly swarms to obtain a long record of past environments.</span>
<span class="attribution"><span class="source">Andy Cohen</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>For a clearer picture of the environments where these early humans lived, we turned to the fossil record preserved in layers of mud at the bottom of Lake Malawi. Over millennia, pollen blown into the water and tiny lake-dwelling organisms became trapped in <a href="http://lrc.geo.umn.edu/laccore/">layers of muck on the lake’s floor</a>. Members of our collaborative team extracted a <a href="https://doi.org/10.1016/j.palaeo.2010.10.030">1,250-foot (380-meter) drill core</a> of mud from a modified barge, then painstakingly tallied the microscopic fossils it contained, layer by layer. They then used them to reconstruct ancient environments across the entire basin.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Malawi landscape with patches of forest high in the hills" src="https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395893/original/file-20210420-21-1rylzf9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=423&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Today, the high plateaus of northern Malawi harbor most of the remaining forests that once extended all the way to the Lake Malawi shoreline.</span>
<span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Today, this region is characterized by bushy, <a href="https://doi.org/10.1016/j.actao.2020.103599">fire-tolerant open woodlands</a> that do not develop a thick and enclosed canopy. Forests that do develop these canopies harbor the richest diversity in vegetation; this ecosystem is now restricted to patches that occur at higher elevations. But these forests once stretched all the way to the lakeshore.</p>
<p>Based on the fossil plant evidence present at various times in the drill cores, we could see that the area around Lake Malawi repeatedly alternated between wet times of forest expansion and dry periods of forest contraction. </p>
<p>As the area underwent cycles of aridity, driven by natural climate change, the lake shrank at times to only 5% of its present volume. When lake levels eventually rose each time, forests <a href="https://doi.org/10.1111/gcb.14150">encroached on the shoreline</a>. This happened time and time again over the last 636,000 years.</p>
<h2>Harnessing fire to manage resources</h2>
<p>The mud in the core also contains a record of fire history, in the form of tiny fragments of charcoal. Those little flecks told us that around 85,000 years ago, something strange happened around Lake Malawi. Charcoal production spiked, erosion increased and, for the first time in more than half a million years, rainfall did not bring forest recovery.</p>
<p>At the same time this charcoal burst appears in the drill core record, our sites began to show up in the archaeological record – eventually becoming so numerous that they formed one continuous landscape littered with stone tools. Another drill core immediately offshore showed that as site numbers increased, more and more charcoal was washing into the lake. Early humans had begun to make their first permanent mark on the landscape.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="people silhouetted against bonfire at night" src="https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=266&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=266&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=266&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=334&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=334&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395891/original/file-20210420-23-1ucsfyb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=334&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many people around the world still rely on fire for warmth, cooking, ritual and socializing – including the research crew when doing fieldwork.</span>
<span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Fire use is a technology that stretches back <a href="https://doi.org/10.1098/rstb.2015.0164">at least a million years</a>. Using it in such a transformative way is human innovation at its most powerful. Modern hunter-gatherers use fire to warm themselves, cook food and socialize, but many also deploy it as an engineering tool. Based on the wide-scale and permanent transformation of vegetation into more fire-tolerant woodlands, we infer that this was what these ancient hunter-gatherers were doing.</p>
<p>By converting the natural seasonal rhythm of wildfire into something more controlled, people can encourage specific areas of vegetation to grow at different stages. This so-called “<a href="https://doi.org/10.1002/evan.21482">pyrodiversity</a>” establishes miniature habitat patches and diversifies opportunities for foraging, kind of like increasing product selection at a supermarket.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="people digging in red earth at an outdoor archaeological site" src="https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395552/original/file-20210417-15-5xlhfa.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The research team exposes ancient stone tools near Karonga, Malawi.</span>
<span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Just like today, changing any part of an ecosystem has consequences everywhere else. With the loss of closed forests in ancient Malawi, the vegetation became dominated by more open woodlands that are resilient to fire – but these did not contain the same species diversity. This combination of rainfall and reduced tree cover also increased opportunities for erosion, which spread sediments into a thick blanket known as an alluvial fan. It sealed away archaeological sites and created the landscape you can see here today.</p>
<h2>Human impacts can be sustainable</h2>
<p>Although the spread of farmers through Africa within the last few thousand years brought about more <a href="https://doi.org/10.1073/pnas.1802172115">landscape and vegetation transformations</a>, we have found that the legacy of human impacts was already in place tens of thousands of years before. This offers a chance to understand how such impacts can be sustained over very long timescales.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="aerial view of an excavation site in Malawi" src="https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395894/original/file-20210420-21-1ysfwud.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Open woodlands have grown over alluvial fans that formed during the Middle Stone Age. Trenches such as this one at an excavation site show multiple layers of discarded artifacts over a period of tens of thousands of years.</span>
<span class="attribution"><span class="source">Jessica Thompson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Most people associate human impacts with a time after the Industrial Revolution, but paleo-scientists have a deeper perspective. With it, researchers like us can see that wherever and whenever humans lived, we must abandon the idea of “<a href="https://www.pnas.org/content/118/17/e2023483118">pristine nature</a>,” untouched by any human imprint. However, we can also see how humans shaped their environments in sustainable ways over very long periods, causing ecosystem transformation without collapse.</p>
<p>Seeing the long arc of human influence therefore gives us much to consider about not only our past, but also our future. By establishing long-term ecological patterns, conservation efforts related to fire control, species protection and human food security can be <a href="https://doi.org/10.1038/s41559-020-01361-4">more targeted and effective</a>. People living in the tropics, such as Malawi today, are especially vulnerable to the economic and social impacts of food insecurity brought about by <a href="https://www.un.org/press/en/2019/gaef3516.doc.htm">climate change</a>. By studying the deep past, we can establish connections between long-term human presence and the biodiversity that sustains it.</p>
<p>With this knowledge, people can be better equipped to do what humans had already innovated nearly 100,000 years ago in Africa: manage the world around us.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/HaO9UPvirQk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Paleoanthropologist Jessica Thompson explains the research.</span></figcaption>
</figure>
<p>[<em>The Conversation’s newsletter explains what’s going on with the coronavirus pandemic. <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=coronavirus-going-on">Subscribe now</a>.</em>]</p><img src="https://counter.theconversation.com/content/158574/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jessica Thompson has received funding for this research from the Australian Research Council, Wenner-Gren Foundation, and National Geographic Society-Waitt Foundation. She is affiliated with Yale University and the Yale Peabody Museum of Natural History, Arizona State University, the Paleoanthropology Society, the Society of Africanist Archaeologists, and the Society for American Archaeology. </span></em></p><p class="fine-print"><em><span>David K. Wright has received funding from the Wenner-Gren Foundation, National Geographic Foundation, Nordforsk (Nordic Council of Ministers) fund and the National Research Foundation of Korea. He is affiliated with the University of Oslo and the State Key Laboratory of Loess and Quaternary Geology at the Chinese Academy of Sciences and is a member of the Society for American Archaeology and the Society of Africanist Archaeologists.</span></em></p><p class="fine-print"><em><span>Sarah Ivory receives funding from the US National Science Foundation and the Belmont Forum. </span></em></p>
Combining evidence from archaeology, geochronology and paleoenvironmental science, researchers identified how ancient humans by Lake Malawi were the first to substantially modify their environment.
Jessica Thompson, Assistant Professor of Anthropology, Yale University
David K. Wright, Professor of Archaeology, Conservation and History, University of Oslo
Sarah Ivory, Assistant Professor of Geosciences, Penn State
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/148381
2020-10-21T18:01:02Z
2020-10-21T18:01:02Z
Turbulent environment set the stage for leaps in human evolution and technology 320,000 years ago
<figure><img src="https://images.theconversation.com/files/364551/original/file-20201020-19-15ycnx4.JPG?ixlib=rb-1.1.0&rect=0%2C535%2C3887%2C2374&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Drilling 139 meters down to volcanic rock provided scientists with a million-year environmental record. </span> <span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span></figcaption></figure><p>People thrive all across the globe, at every temperature, altitude and landscape. How did human beings become so successful at adapting to whatever environment we wind up in? <a href="https://humanorigins.si.edu/about/human-origins-program-team/rick-potts">Human origins researchers like me</a> are interested in how this quintessential human trait, <a href="https://doi.org/10.1016/j.jhevol.2015.06.014">adaptability</a>, evolved.</p>
<p>At a site in Kenya, my colleagues and I have been working on this puzzle for decades. It’s a place where we see big changes happening in the archaeological and fossil records hundreds of thousands of years ago. But what external factors drove the emergence of behaviors that typify how our species, <em>Homo sapiens</em>, interacts with its surroundings?</p>
<p>We wanted to know if we could connect what was happening in the environment at the time to these shifts in technology and the human species that lived there. Based on our analysis, <a href="https://advances.sciencemag.org/content/6/43/eabc8975">published in the journal Science Advances</a>, we conclude that the roots of <em>Homo sapiens</em>‘ evolutionary adaptations stem from our ability to adjust to environmental change.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Aerial view of the Olorgesailie basin today." src="https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364559/original/file-20201020-15-immv6u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aerial view of the Olorgesailie region today.</span>
<span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span>
</figcaption>
</figure>
<h2>Missing time in the archaeological record</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map locates the site in Kenya" src="https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364584/original/file-20201020-15-13t3y9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Olorgesailie is in Kenya, in East Africa.</span>
<span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span>
</figcaption>
</figure>
<p>Famed prehistoric site Olorgesailie is in southern Kenya. It lies within the Rift Valley, a seismically active area where lakes and streams produced sediments that accumulated over time, burying and preserving fossilized bones and ancient stone tools.</p>
<p>At Olorgesailie, our scientific team has found evidence that’s potentially related to the origin of <em>Homo sapiens</em> in the form of a critical transition from one technology to another.</p>
<p>The older technology is typified by large, oval cutting implements called handaxes. Typical of what’s called Acheulean stone technology, nearly two dozen layers of these handaxes and other <a href="https://doi.org/10.1126/science.aao2200">Acheulean tools have been unearthed at Olorgesailie</a>. They span an immense period of about 700,000 years, covering a time when fossil remains show that the hominin species <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-erectus"><em>Homo erectus</em></a> and <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-heidelbergensis"><em>Homo heidelbergensis</em></a> inhabited eastern Africa.</p>
<p>The last Acheulean archeological sites at Olorgesailie are 500,000 years old, at which point there is a frustrating 180,000-year gap in these sediments caused by erosion. The archaeological record starts up again around 320,000 years ago, as sediments began to fill in the landscape.</p>
<p>But the Acheulean was gone. In its place was <a href="https://humanorigins.si.edu/research/east-african-research-projects/evolution-human-innovation">Middle Stone Age technology</a>, consisting typically of smaller, more easily carried implements than the clunky Acheulean handaxes. In other areas of Africa, the Middle Stone Age technology is associated with the earliest African <em>Homo sapiens</em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Acheulean handaxes and Middle Stone Age projectiles and pigments" src="https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364548/original/file-20201020-17-1ab9zg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">After a 180,000-year gap in the record at Olorgesailie, Achulean technologies had been replaced by those of the Middle Stone Age.</span>
<span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span>
</figcaption>
</figure>
<p>These toolmakers often used sharp-edged black obsidian as a raw material. Archaeologists <a href="https://humanorigins.si.edu/about/human-origins-program-team/alison-brooks">Alison Brooks</a>, <a href="https://humanorigins.si.edu/about/human-origins-program-team/john-yellen">John Yellen</a> and others chemically traced the obsidian to distant outcrops in several different directions, up to 95 kilometers away from Olorgesailie. They concluded that the <a href="https://doi.org/10.1126/science.aao2646">far-off obsidian sources</a> provide evidence of resource exchange among groups, a phenomenon unknown in Acheulean times.</p>
<p>Our Middle Stone Age excavations also contained <a href="https://doi.org/10.1126/science.aao2646">black and red coloring materials</a>. Archaeologists view pigments like these as signs of increasingly complex symbolic communication. Think of all the ways people use color – in flags, clothing and the many other ways people visually claim their identity as part of a group.</p>
<p>So here we had the extinction of the Acheulean way of life as well as its replacement by dramatically new behaviors including technological innovations, intergroup exchange of obsidian and the use of pigments. But we had no way to examine what happened in the 180,000-year gap when this transition took place.</p>
<p>We needed to recover that time. We started strategizing how we could unearth sediments from somewhere nearby that would have recorded the environments and survival challenges associated with this shift in early human adaptation.</p>
<h2>Turning to geology for clues about early humans</h2>
<p>Different types of sediment are laid down in lakes, streams and soils, and the sediment layers tell the story of changing environments over time. Geologists <a href="https://naturalhistory.si.edu/staff/kay-behrensmeyer">Kay Behrensmeyer</a> and <a href="http://www.bgc.org/people/each_person/deino_a.html">Alan Deino</a> joined me in the field in southern Kenya to figure out where we might <a href="https://humanorigins.si.edu/research/east-african-research-projects/olorgesailie-drilling-project">drill for sediments</a> that could fill in the Olorgesailie time gap.</p>
<p>We surmised that the key to understanding the big transition would lie beneath a flat, grassy plain about 24 kilometers south of our Olorgesailie excavations. Together with colleagues including <a href="https://scholar.google.com/citations?user=xx3i6sIAAAAJ&hl=en&oi=ao">René Dommain</a> and collaborators from the <a href="http://lrc.geo.umn.edu/laccore/">National Lacustrine Core Facility</a>, we drilled in September 2012 until we reached the volcanic rock floor of the Rift Valley.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="drill team at work at dusk" src="https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364554/original/file-20201020-17-1ttsh.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The drill team extracted a cylinder of earth, just four centimeters in diameter, that turned out to represent 1 million years of environmental history.</span>
<span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span>
</figcaption>
</figure>
<p>The result was a core 139 meters deep containing a sequence of ancient lake and lake margin habitats and soils, all riddled with volcanic layers we could date to yield the most precisely dated East African environmental record for the past 1 million years.</p>
<p>With advice from geologist <a href="https://www.geo.arizona.edu/Cohen">Andy Cohen</a> and other colleagues, I assembled an international team of earth scientists and paleoecologists to sample and analyze the core. We figured out ways to convert many different measures of past environment – microscopic bits of plants, <a href="https://diatoms.org/news/do-diatoms-form-fossils">single-celled diatoms</a> from the ancient lake deposits and various chemical signals – into ecological measures of freshwater availability and vegetation cover. The <a href="https://advances.sciencemag.org/content/6/43/eabc8975">newly published study</a> provides our findings.</p>
<h2>Environments during the time gap</h2>
<p>The sediment record showed that during the era 1 million to 500,000 years ago, when Acheulean toolmakers were busy in the Olorgesailie basin, ecological resources were relatively stable. Fresh water was reliably available. Grazing zebra, rhinoceros, baboons, elephants and pigs altered the regional vegetation of wooded grassland to create short, nutritious grassy plains.</p>
<p>And then what happened in the time gap?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cross-section of part of the core" src="https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=581&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=581&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=581&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=730&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=730&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364556/original/file-20201020-13-1kqu1gv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=730&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Each sediment layer visible in this cross-section of the core provides a clue about the ancient environment.</span>
<span class="attribution"><span class="source">LacCore, University of Minnesota</span></span>
</figcaption>
</figure>
<p>The core is very well preserved in the previously mysterious time interval. We determined that right around 400,000 years ago, a critical environmental transition took place. From a relatively stable setting, we started to see repeated fluctuation in the vegetation, available water and other ecological resources on which our ancestors and other mammals depend. </p>
<p>According to the anthropological literature, <a href="https://doi.org/10.1017/S0959774314000237">hunter-gatherers today and in recent history</a> respond to periods of uncertain resources by investing time and energy to refine their technology. They connect with distant groups to sustain networks of resource and information exchange. And they develop symbolic markers that strengthen these social connections and group identity.</p>
<p>Sound familiar? These behaviors resemble how the ancient Middle Stone Age lifestyle at Olorgesailie differed from the Acheulean way of life.</p>
<p>Equally notable, the large grazing species typical of Acheulean times became extinct after 500,000 years ago. Between 360,000 and 300,000 years ago, ecologically flexible herbivore species smaller in size, less water-dependent and reliant on both short and tall grass and tree leaves, had replaced the specialized grazers such as now-extinct species of zebras and the huge baboon.</p>
<p>These changes in the animal community reflect the advantage of adaptable diets, a parallel to how our Middle Stone Age ancestors adjusted to environmental uncertainty.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="scientists working with a cross-section of a sediment core" src="https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364560/original/file-20201020-19-7zd9xm.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Back in the lab, scientists analyzed the contents of the core’s sediment layers.</span>
<span class="attribution"><span class="source">Human Origins Program, Smithsonian</span></span>
</figcaption>
</figure>
<p>For the past two decades, many human origins researchers have thought of <a href="https://doi.org/10.1126/science.1190683">climate as the primary</a>, if not sole, driver of hominin adaptive evolution. Our new study draws attention, though, to several factors in the Acheulean-Middle Stone Age transition in southern Kenya.</p>
<p>Yes, rainfall varied strongly after the environmental transition 400,000 years ago. But the terrain across the region also became fractured by tectonic activity and blanketed with volcanic ash. And big herbivores exerted different influences on the vegetation before and after this transition.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>The result was an ecological cascade of changes that included the early humans who practiced the Middle Stone Age way of life. We propose that all of these factors together instigated this critical evolutionary change.</p>
<p>The Middle Stone Age might hold a lesson for today. As humanity now confronts an era of environmental uncertainty on a global scale, is our species sufficiently nimble to engage social networks, new technologies, and reliable sources of information to adjust to the environmental disruptions ahead?</p><img src="https://counter.theconversation.com/content/148381/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Potts receives funding from the Smithsonian Institution, and the project reported in the article received funding from the William H. Donner Foundation (all research project funding is reported in the publication on which The Conversation article is based). </span></em></p>
A new environmental record for a prehistoric site in Kenya helped researchers figure out how external conditions influenced which of our ancient ancestors lived there, with what way of life.
Richard Potts, Director of the Human Origins Program, Smithsonian Institution
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/139458
2020-09-15T19:28:35Z
2020-09-15T19:28:35Z
Ancient DNA is revealing the genetic landscape of people who first settled East Asia
<figure><img src="https://images.theconversation.com/files/352993/original/file-20200814-22-dg3488.jpg?ixlib=rb-1.1.0&rect=310%2C222%2C3016%2C2074&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pulverized ancient bone can provide DNA to scientists for analysis.</span> <span class="attribution"><span class="source">Xin Xu Institute of Vertebrate Paleontology and Paleoanthropology</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The very first human beings originally emerged in Africa before <a href="https://doi.org/10.1002/evan.21455">spreading across Eurasia</a> about 60,000 years ago. After that, the story of humankind heads down many different paths, some more well-studied than others.</p>
<p>Eastern regions of Eurasia are home to approximately 2.3 billion people today – roughly 30% of the world’s population. Archaeologists know <a href="https://doi.org/10.1016/j.quaint.2011.02.017">from fossils</a> <a href="https://doi.org/10.1126/science.aat8824">and artifacts</a> that modern humans have occupied <a href="https://doi.org/10.1038/nature23452">Southeast Asia for 60,000 years</a> and East Asia for 40,000 years.</p>
<p>But there’s a lot left to untangle. Who were the people who first came to these regions and eventually developed agriculture? Where did different populations come from? Which groups ended up predominant and which died out?</p>
<p>Ancient DNA is helping to answer some of these questions. By sequencing the genomes of people who lived many millennia ago, <a href="https://scholar.google.com/citations?user=3sRfg2sAAAAJ&hl=en&oi=ao">scientists like me</a>
are starting to fill in the picture of how Asia was populated.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Ancient skull without bottom jaw" src="https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/353009/original/file-20200814-20-otal1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Well-preserved DNA from ancient bones holds clues about how human beings spread into East Asia.</span>
<span class="attribution"><span class="source">Wei Gao, Institute of Vertebrate Paleontology and Paleoanthropology</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Analyzing ancient genomes</h2>
<p>In 2016, I joined Dr. Qiaomei Fu’s Molecular Paleontology Lab at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences in Beijing. Our challenge: Resolve the history of humans in East Asia, with the help of collaborators who were long dead – ancient humans who lived up to tens of thousands of years ago in the region. </p>
<p>Members of the lab extracted and sequenced ancient DNA using human remains from archaeological sites. Then Dr. Fu and I used computational genomic tools to assess how their DNA related to that of previously sequenced ancient and present-day humans.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map where aDNA samples were excavated in Asia" src="https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=444&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=444&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357984/original/file-20200914-24-1frozem.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=444&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tianyuan Man, from near present-day Beijing, and Hòabìnhian people, from present-day Laos and Malaysia, represent two very old lineages that are distinct from today’s East Asians.</span>
<span class="attribution"><span class="source">Map © OpenStreetMap contributors, modified by The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>One of our sequences came from ancient DNA extracted from the <a href="https://www.pnas.org/content/110/6/2223">leg bones</a> of the Tianyuan Man, a <a href="https://doi.org/10.1016/j.cub.2017.09.030">40,000-year-old individual</a> discovered near <a href="https://whc.unesco.org/en/list/449/">a famous paleoanthropological site</a> in western Beijing. One of the earliest modern humans found in East Asia, his genetic sequence marks him as an early ancestor of today’s Asians and Native Americans. That he lived where China’s current capital stands indicates that the ancestors of today’s Asians began placing roots in East Asia as early as 40,000 years ago. </p>
<p>Farther south, <a href="https://doi.org/10.1126/science.aat3628">two 8,000- to 4,000-year-old Southeast Asian hunter-gatherers</a> from Laos and Malaysia associated with the Hòabìnhian culture have DNA that, like the Tianyuan Man, shows they’re early ancestors of Asians and Native Americans. These two came from a completely different lineage than the Tianyuan Man, which suggested that many genetically distinct populations occupied Asia in the past. </p>
<p>But no humans today share the same genetic makeup as either Hòabìnhians or the Tianyuan Man, in both East and Southeast Asia. Why did ancestries that persisted for so long vanish from the gene pool of people alive now? Ancient farmers carry the key to that answer. </p>
<h2>DNA carries marks of ancient migrations</h2>
<p>Based on plant remains found at archaeological sites, scientists know that <a href="https://www.sciencedaily.com/releases/2015/12/151214084754.htm">people domesticated millet</a> in northern China’s Yellow River region about 10,000 years ago. Around the same time, people in southern China’s Yangtze River region <a href="https://doi.org/10.1073/pnas.1308942110">domesticated rice</a>.</p>
<p>Unlike in Europe, plant domestication began locally and was not introduced from elsewhere. The process took thousands of years, and societies in East Asia grew increasingly complex, with the rise of the <a href="https://doi.org/10.1146/annurev-anthro-091908-164513">first dynasties</a> around 4,000 years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map showing migration of ancient people north from Yellow River area and south from Yangtze River area" src="https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=444&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=444&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357986/original/file-20200914-18-z19zh1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=444&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rice farmers, possibly from around the Yangtze River, moved south into Southeast Asia, while millet farmers from around the Yellow River moved north into Siberia.</span>
<span class="attribution"><span class="source">Map © OpenStreetMap contributors, modified by The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>That’s also when rice cultivation appears to have spread from its origins to areas farther south, including lands that are today’s Southeast Asian countries. DNA helps tell the story. When rice farmers from southern China expanded southward, they introduced not only their farming technology but also their genetics to local populations of Southeast Asian hunter-gatherers. </p>
<p>The overpowering influx of their DNA ended up swamping the local gene pool. Today, <a href="https://doi.org/10.1126/science.aat3628">little trace of hunter-gatherer ancestry</a> <a href="https://doi.org/10.1126/science.aat3188">remains in the genes of people</a> who live in Southeast Asia. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Excavation of human skeleton" src="https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/353002/original/file-20200814-24-czv093.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The skeleton of a person who lived about 8,700 years ago in Xiaogao, Shandong, China near the Yellow River. This individual’s northern East Asian ancestry can be found in the remains of people who lived up into the eastern steppes of Siberia.</span>
<span class="attribution"><span class="source">Jianfeng Lang, Shandong University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Farther north, <a href="https://doi.org/10.1038/s41586-019-1279-z">a similar story played out</a>. Ancient Siberian hunter-gatherers show little relationship with East Asians today, but later Siberian farmers are closely related to today’s East Asians. Farmers from northern China moved northward into Siberia bringing their DNA with them, leading to a sharp decrease in prevalence of the previous local hunter-gatherer ancestry.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientist in protective gear pipetting under a hood" src="https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/353000/original/file-20200814-14-1aipm61.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Professor Qiaomei Fu, head of the Molecular Paleontology Lab at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, prepares samples for ancient DNA extraction.</span>
<span class="attribution"><span class="source">Institute of Vertebrate Paleontology and Paleoanthropology</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Past populations were more diverse than today’s</h2>
<p>Genetically speaking, today’s East Asians are not very different from each other. A lot of DNA is needed to start genetically distinguishing between people with different cultural histories.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Folded up ancient skeleton being excavated" src="https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=868&fit=crop&dpr=1 600w, https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=868&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=868&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1091&fit=crop&dpr=1 754w, https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1091&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/353004/original/file-20200814-18-mdsmzw.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1091&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This individual, who lived about 8,300 years ago on Liang island in the Taiwan Strait, has the southern ancestry found in inhabitants of coastal mainland southern China.</span>
<span class="attribution"><span class="source">Hunglin Chiu, Institute of Anthropology, National Tsinghua University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>What surprised Dr. Fu and me was how different the DNA of various ancient populations were in China. <a href="https://doi.org/10.1126/science.aba0909">We</a> <a href="https://doi.org/10.1101/2020.03.25.004606">and</a> <a href="https://doi.org/10.1038/s41467-020-16557-2">others</a> found shared DNA across the Yellow River region, a place important to the development of Chinese civilization. This shared DNA represents a northern East Asian ancestry, distinct from a southern East Asian ancestry <a href="https://doi.org/10.1126/science.aba0909">we found in coastal southern China</a>. </p>
<p>When we analyzed the DNA of people who lived in coastal southern China 9,000-8,500 years ago, we realized that already by then much of China shared a common heritage. Because their <a href="http://www.kaogu.cn/en/Research_work/Excavation_Report/2018/0122/60804.html">archaeology</a> and <a href="https://doi.org/10.1038/s41598-018-35426-z">morphology</a> was different from that of the Yellow River farmers, we had thought these coastal people might come from a lineage not closely related to those first agricultural East Asians. Maybe this group’s ancestry would be similar to the Tianyuan Man or Hòabìnhians.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map showing different ancestral populations in Asia based on aDNA" src="https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=444&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=444&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357988/original/file-20200914-18-160rygb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=444&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People with different lifestyles who lived far apart in northern China near the Yellow River and along the southern China coast as far back as 9,000 years ago both passed their distinct DNA down to present-day East Asians and Southeast Asians. Austronesians are the closest descendants of the ancient population from coastal southern China.</span>
<span class="attribution"><span class="source">Map © OpenStreetMap contributors, modified by The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>But instead, every person we sampled was closely related to present-day East Asians. That means that by 9,000 years ago, DNA common to all present-day East Asians was widespread across China.</p>
<p>Today’s northern and southern Chinese populations share more in common with ancient Yellow River populations than with ancient coastal southern Chinese. Thus, early Yellow River farmers migrated both north and south, contributing to the gene pool of humans across East and Southeast Asia. </p>
<p>The coastal southern Chinese ancestry did not vanish, though. It persisted in small amounts and did increase in <a href="https://doi.org/10.1038/s41467-020-16557-2">northern China’s Yellow River region over time</a>. The influence of ancient southern East Asians is low on the mainland, but they had a huge impact elsewhere. On islands spanning from the Taiwan Strait to Polynesia live the <a href="https://doi.org/10.1007/s00439-015-1620-z">Austronesians</a>, best known for their seafaring. They possess the <a href="https://doi.org/10.1126/science.aba0909">highest amount of southern East Asian ancestry today</a>, highlighting their ancestry’s roots in coastal southern China.</p>
<p><a href="https://doi.org/10.1101/2020.03.25.004606">Other emerging</a> <a href="https://doi.org/10.1126/science.aba0909">genetic patterns</a> show connections between Tibetans and ancient individuals from Mongolia and northern China, raising questions about the peopling of the Tibetan Plateau.</p>
<p>Ancient DNA reveals rapid shifts in ancestry over the last 10,000 years across Asia, likely due to migration and cultural exchange. Until more ancient human DNA is retrieved, scientists can only speculate as to exactly who, genetically speaking, lived in East Asia prior to that.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/139458/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Melinda A. Yang does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
By studying the DNA of people who lived in East Asia thousands of years ago, scientists are starting to untangle how the region was populated.
Melinda A. Yang, Assistant Professor of Biology, University of Richmond
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/138502
2020-05-14T15:01:11Z
2020-05-14T15:01:11Z
Prehistoric human footprints reveal a rare snapshot of ancient human group behavior
<figure><img src="https://images.theconversation.com/files/334730/original/file-20200513-156656-128gm8y.jpg?ixlib=rb-1.1.0&rect=26%2C0%2C1251%2C850&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Footprints, preserved in solidified ash, hint at human behavior from as long as 19,000 years ago.</span> <span class="attribution"><span class="source">Cynthia Liutkus-Pierce</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>When it comes to reconstructing how ancient creatures lived, <a href="https://scholar.google.com/citations?user=s_lTDHAAAAAJ&hl=en&oi=sra">palaeontologists</a> <a href="https://scholar.google.com/citations?user=0fcPp2oAAAAJ&hl=en&oi=ao">like us</a> are as much detectives as we are scientists.</p>
<p>We’re used to partial evidence, dead ends and red herrings. It’s especially hard to reconstruct ancient behaviors, something we are particularly interested in. We must rely on either skeletal remains or the physical things left behind by ancient people to deduce anything about their lives, be it what they ate, how they moved or the origins of complex behaviors like creating tools or communicating with language. </p>
<p>Prehistoric footprints are a remarkable and precious source of evidence for the behavior and biology of ancient organisms, capturing a snapshot of their lives in deep time. In a new paper <a href="https://doi.org/10.1038/s41598-020-64095-0">in Nature Scientific Reports</a>, our research team documented and interpreted an extraordinary site in northern Tanzania called Engare Sero, where hundreds of human footprints were preserved in volcanic ash many thousands of years ago.</p>
<p>It’s the most abundant assemblage of ancient human footprints currently known from Africa and suggests this ancient community had a division of labor between the adult females and males.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334734/original/file-20200513-156637-ftwt4s.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This beautifully preserved print includes mud splashed up along the sides.</span>
<span class="attribution"><span class="source">William Harcourt-Smith</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Footprints fill in the story</h2>
<p>Footprints are unique in that they are a preserved moment in time when an animal moved across a landscape and left traces of its movements imprinted in the ground.</p>
<p>While they cannot tell you too much about how an animal looked, they can be surprisingly useful for reconstructing many other aspects of their biology. Footprints can tell you how fast an animal was running, where it was going and sometimes even if the animal was solitary or moved in herds.</p>
<p>For the human lineage, footprint sites have been especially important in furthering scientists’ understanding of our own evolutionary journey. The iconic 3.66-million-year-old paleontological <a href="http://humanorigins.si.edu/evidence/behavior/footprints/laetoli-footprint-trails">site of Laetoli</a> in Tanzania, for instance, provided some of the earliest definitive evidence of upright walking in our ancient ancestors.</p>
<p>While Engare Sero is much younger than Laetoli, it provides a fascinating snapshot of a time period when our own species, <em>Homo sapiens</em>, was on the rise.</p>
<h2>Ancient tracks in the shadow of Oldoinyo L’engai</h2>
<p>When you walk along wet sand on a beach, your footprints might last for a few minutes, or a few hours, before being washed away by the ocean. But if you were to walk in wet volcanic ash and leave your footprints behind, and the ash then dried nearly as hard as concrete, your footprints could last thousands – or even millions – of years.</p>
<p>That’s exactly what happened thousands of years ago when a group of at least 20 prehistoric modern humans walked through a volcanic mudflow produced by the Oldoinyo L’engai volcano, still active today in what’s now Tanzania.</p>
<p>The local Tanzanian Masai have known about this set of ancient human footprints at Engare Sero for a while. When our research team leader, geologist <a href="https://scholar.google.com/citations?user=S6CMoeoAAAAJ&hl=en&oi=ao">Cynthia Liutkus-Pierce</a>, first visited the site in 2009, only 56 footprints had been exposed by natural surface erosion – but she was still floored by what she saw.</p>
<p>Our research group – including archaeologists, anthropologists, <a href="https://scholar.google.com/citations?user=uI2kqbwAAAAJ&hl=en&oi=ao">biologists</a>, <a href="https://scholar.google.com/citations?user=_g5NusoAAAAJ&hl=en&oi=ao">geologists</a>, <a href="https://scholar.google.com/citations?user=FG-u0pIAAAAJ&hl=en&oi=ao">statisticians</a> <a href="https://scholar.google.com/citations?user=Nm62f5YAAAAJ&hl=en&oi=sra">and other</a> <a href="https://scholar.google.com/citations?user=Ym6w5bAAAAAJ&hl=en&oi=ao">scientists</a> – went on to uncover, document and analyze an astonishing 408 total human footprints. Using two different <a href="https://www.nature.com/scitable/knowledge/library/dating-rocks-and-fossils-using-geologic-methods-107924044/">dating techniques that measure radioactive decay</a> in the material that preserved the footprints, we dated the footprints to between <a href="https://doi.org/10.1016/j.palaeo.2016.09.019">6,000 and 19,000 years ago</a>. In this time period, modern humans were likely the only hominin species left in Africa, and had already spread to many other parts of the globe.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=458&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=458&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=458&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=576&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=576&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334731/original/file-20200513-156629-uywmag.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=576&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Careful analysis revealed the footprints of 17 individual people traveling together, each track depicted in its own color.</span>
<span class="attribution"><span class="source">Hatala et al., 2020</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What the prints describe</h2>
<p>We meticulously traced each footprint trail and analyzed the size, spacings and directions of the footprints. We determined that 17 of the footprint tracks were created by a single group of individuals walking at the same time in a southwesterly direction. Based on a sophisticated statistical analysis using a vast comparative dataset of modern foot dimensions, this group likely consisted of mainly 14 adult females, with two adult males and one younger male.</p>
<p>Modern foragers such as the <a href="https://www.nationalgeographic.org/encyclopedia/hadza/">Hadza in Tanzania</a> and the <a href="http://www.public.asu.edu/%7Ekrhill3/Ache.html">Ache in Paraguay</a> often include groups of adult females cooperatively gathering food together, with occasional visits from or accompaniment by adult males. This scenario seems a plausible fit for the group structure and patterns of movements we inferred at Engare Sero. The footprints may indicate cooperative and sexually divided foraging in this ancient human community.</p>
<p>While we don’t know what the community of people who made these prints was specifically like, we know that hominins in Africa at this time were engaging in complex behaviors, and that they were members of our own species, <em>Homo sapiens</em>. They may have been foraging along a lake shore, looking for plants or shellfish to eat. They may have been carrying bows and arrows to hunt animals like the antelopes, zebra or buffalo who left other footprints nearby. Maybe these people looked up when they heard another rumble of the nearby volcano, which had erupted recently enough that the ash underneath their bare feet was still soft.</p>
<p>There are also six other footprint tracks heading in an almost perfectly opposite direction, to the northeast. Most of the people who made these footprints were walking at different speeds and at least one was running, suggesting that these tracks were not created by a single group traveling together.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334735/original/file-20200513-156679-177vpup.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Preserved for thousands of years, the prints look like what your own foot might squish into wet sand at the beach.</span>
<span class="attribution"><span class="source">William Harcourt-Smith</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Preserving Engare Sero for the future</h2>
<p>Several of the human footprint tracks lead to a nearby sand dune to the north. We’ve purposefully left any footprints preserved under the sand dune unexcavated for now, until we can work with the Tanzanian government to develop a conservation plan to track and limit erosion of the footprints.</p>
<p>The hardened ash is remarkably resilient to erosion from water and wind. Still, thanks to the <a href="https://3d.si.edu/">Smithsonian’s 3D Digitization Program</a>, we have meticulously captured three-dimensional data for each of the footprints so we can trace any natural destruction of the prints over time. You can even <a href="https://3d.si.edu/collections/engareserohumanfootprints">download 3D files</a> of a few of the Engare Sero footprints, in case you want to 3D print your own copies.</p>
<p>[<em>Insight, in your inbox each day.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=insight">You can get it with The Conversation’s email newsletter</a>.]</p><img src="https://counter.theconversation.com/content/138502/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William E.H. Harcourt-Smith receives funding from the Leakey Foundation, the National Science Foundation, and the Wenner-Gren Foundation.</span></em></p><p class="fine-print"><em><span>Briana Pobiner receives funding from the National Science Foundation, the Leakey Foundation, and the Wenner-Gren Foundation. </span></em></p>
The footprints of over 20 different prehistoric people, pressed into volcanic ash thousands of years ago in Tanzania, show possible evidence for sexual division of labor in this ancient community.
William E.H. Harcourt-Smith, Research Associate, Division of Paleontology, American Museum of Natural History, and Associate Professor in Anthropology, Lehman College, CUNY
Briana Pobiner, Research Scientist and Museum Educator, Smithsonian Institution
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/130535
2020-04-01T19:08:55Z
2020-04-01T19:08:55Z
Baby steps: this ancient skull is helping us trace the path that led to modern childhood
<figure><img src="https://images.theconversation.com/files/324205/original/file-20200331-65495-1u437rv.jpg?ixlib=rb-1.1.0&rect=29%2C39%2C3265%2C2356&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The original Dikika child skull (left), a 3D model produced with synchrotron scanning (middle), and a model corrected for distortion during fossilisation (right).</span> <span class="attribution"><span class="source">Gunz et al. (2020) / Science Advances. </span>, <span class="license">Author provided</span></span></figcaption></figure><p>Within our extended primate family consisting of lemurs, monkeys, and apes, humans have the largest brains. Our closest living relatives, chimpanzees, weigh about two-thirds as much as us, yet our brains are about 3.5 times larger.</p>
<p>Ours are also organised differently, and take longer to grow and mature. This extended period of development leads to a particularly long childhood for humans – one that requires extra parental care and protection. </p>
<p>Brains consume a large amount of energy. For a species that has a small brain at birth and a large one in adulthood, growth must either occur rapidly, or over a long time, or through a combination of both.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-smart-were-our-ancestors-turns-out-the-answer-isnt-in-brain-size-but-blood-flow-130387">How smart were our ancestors? Turns out the answer isn't in brain size, but blood flow</a>
</strong>
</em>
</p>
<hr>
<p>Researchers first observed exceptionally large brains in the human fossil record from about 300,000 years ago. However, the slower rate of brain development, which is now unique to humans, began more than three million years ago in the australopithecine lineage. These two-footed hominins from Africa are thought to be ancestral to our genus, <em>Homo</em>. </p>
<p>What triggered the evolutionary brain expansion in hominins, and how this relates to human behaviour, remain hotly debated topics among palaeoanthropologists.</p>
<h2>The Dikika child</h2>
<p>In 2000, an Ethiopian team uncovered an astonishing find in the country’s Dikika region: the skeleton of an ancient baby with a nearly complete skull. </p>
<p>Dated to about 3.3 million years ago, this youngster belonged to the same genus and species as the iconic australopithecine adult female <a href="https://en.wikipedia.org/wiki/Lucy_(Australopithecus)">Lucy</a> – <em>Australopithecus afarensis</em>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324494/original/file-20200401-66115-1kr2msc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Australopithecine skeleton (left) and reconstructions of australopithecines Lucy and the Dikika child.</span>
<span class="attribution"><span class="source">Institute of Human Origins & Zeray Alemseged</span></span>
</figcaption>
</figure>
<p>In a <a href="https://advances.sciencemag.org/content/6/14/eaaz4729">new paper</a> published in Science Advances, we reveal that Lucy’s species shows surprising similarities and differences with both chimpanzees <em>and</em> humans. But in order to make these comparisons, we first needed to work out two critical details: </p>
<ol>
<li>exactly how old was the Dikika child when it died? </li>
<li>how did its brain size compare to adult members of its species, such as Lucy?</li>
</ol>
<h2>X-rays to the rescue</h2>
<p>Brains do not fossilise, but as they grow and expand during childhood, the tissues surrounding them leave their mark inside the skull. </p>
<p>Using three-dimensional virtual models, researchers can measure the space within the brain case as a proxy for brain size. This is accomplished through computed tomography (CT), or synchrotron X-ray imaging. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fKhnaDmVJ98?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This 3D animation shows the skull of the Dikika child.</span></figcaption>
</figure>
<p>A <a href="https://www.esrf.eu/about/synchrotron-science/synchrotron">synchrotron</a> is a machine that accelerates electrons close to the speed of light and directs them around a large ring. By forcing electrons to travel in a circular direction with magnetic fields, extremely bright light is produced that can be filtered and adjusted for research purposes. </p>
<p>A benefit of this approach is that permanent impressions of brain folds on the bone can provide clues about key aspects of the brain’s organisation. Synchrotron imaging can also provide powerful insights into dental development.</p>
<h2>The truth is in the tooth</h2>
<p>A seldom recognised fact about humans and other primates is that our milk (baby) teeth and first molars are marked with a <a href="https://thereader.mitpress.mit.edu/birth-certificate-neonatal-lines/">line formed at birth</a>. Similar to the growth rings of a tree, cross sections of teeth also reveal daily growth lines reflecting the body’s internal rhythms during childhood. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-lengthy-childhood-of-endangered-orangutans-is-written-in-their-teeth-77564">The lengthy childhood of endangered orangutans is written in their teeth</a>
</strong>
</em>
</p>
<hr>
<p>Having access to precise records of the Dikika child’s teeth, we were able to determine how old the child was when it died. Our team’s dental experts calculated an age of 861 days, about 2.4 years. </p>
<p>This means the infant grew its molar teeth rapidly – similar to chimpanzees, and faster than humans. Surprisingly, however, its rate of brain development seemed to have shifted from the fast lane to the slow lane.</p>
<h2>Extending brain growth</h2>
<p>Virtual models of australopithecine brain cases reveal members of Lucy’s species had a chimpanzee-like brain organisation, but grew for a longer period of time.</p>
<p>Our estimates suggest that by 2.4 years old, australopithecine children had brains that were only about 70% as big as adults, while average chimpanzees of the same age would have completed more than 85% of their brain growth. Thus, this species may bridge the gap between the long childhoods humans enjoy today, and the shorter ones of our ape-like ancestors.</p>
<p>Among primates in general, different rates of growth and maturation are associated with varied strategies of caring for infants. Slowing brain development is a way to spread the energetic needs of highly dependent offspring over many years. And this can be linked to a long reliance on caregivers. </p>
<p>Lengthening the period of brain growth also stretches out a species’ highly impressionable learning period. Extended brain growth in Lucy’s species may have provided a basis for the subsequent evolution of the brain and social behaviour in our ancestors. </p>
<p>These baby steps would have been critical for the long childhood that is now often regarded as a keystone of human uniqueness.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-teeth-can-tell-about-the-lives-and-environments-of-ancient-humans-and-neanderthals-104923">What teeth can tell about the lives and environments of ancient humans and Neanderthals</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/130535/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tanya M. Smith receives funding from the Australian Academy of Science and the US National Science Foundation. </span></em></p><p class="fine-print"><em><span>Philipp Gunz receives funding from the Max Planck Society (Germany).</span></em></p><p class="fine-print"><em><span>Zeray Alemseged receives funding from University of Chicago. </span></em></p>
Our findings reveal the slowing down of brain development in our ape-like ancestors began more than three million years ago.
Tanya M. Smith, Professor in the Australian Research Centre for Human Evolution, Griffith University
Philipp Gunz, Group Leader, Max Planck Institute for Evolutionary Anthropology
Zeray Alemseged, Professor, University of Chicago
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/122926
2019-09-04T14:01:36Z
2019-09-04T14:01:36Z
How the skull of humanity’s oldest known ancestor is changing our understanding of evolution
<figure><img src="https://images.theconversation.com/files/290853/original/file-20190904-175678-1wfmd2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">MRD skull.</span> <span class="attribution"><span class="source">Dale Omori, courtesy of the Cleveland Museum of Natural History</span></span></figcaption></figure><p>The <a href="https://www.nature.com/articles/s41586-019-1513-8">recent discovery</a> of a 3.8m-year-old cranium (skull without the lower jaw) is the hottest topic of conversation among palaeoanthropologists right now. But fossils are found all the time, so why is the cranium of this small, old man so important? It turns out the discovery is changing our view of how early hominin species evolved – and how they led to humans. To understand how, let’s start at the beginning. </p>
<p>In 1995, researchers found several partial jaws, isolated teeth and limb bones in Kenya, dated between 4.2m and 3.9m years old, and assigned them to a brand new species: <a href="https://www.nature.com/articles/376565a0"><em>Australopithecus anamensis</em></a>. All these fossils were found in sediments associated with an ancient lake – “anam”, which means lake in the local language. A number of additional specimens were then found in Ethiopia, thought to belong to the same species.</p>
<p>The primitive features of <em>A. anamensis</em> have led to the widespread view that this species is the ancestor of <em>Australopithecus afarensis</em>, a younger hominin from Tanzania, Ethiopia and perhaps Kenya, dated between 3.8m and 3m years old. The most iconic fossil of <em>A. afarensis</em> is probably the partial skeleton <a href="https://iho.asu.edu/about/lucys-story">known as Lucy</a>, which was for a long time viewed as the oldest known human ancestor.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=786&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=786&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=786&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=988&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=988&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290909/original/file-20190904-175668-1ptaud9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=988&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Anagenesis vs cladogenesis.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The newly discovered cranium, nicknamed “MRD” after its collection number MRD-VP-1/1, shows many similarities to the already existing <em>A. anamensis</em> specimens, and was therefore assigned to this species. However, the MRD cranium was intact enough to allow scientists to analyse for the first time the complete face and braincase, and examine parts of the cranium that were still missing in the fossil record of <em>A. anamensis</em>. </p>
<p>The authors discovered several new morphological features in the MRD cranium that are conventionally considered to be characteristic of younger species on the human lineage. The depth of the palate, for example, exceeds that of all known <em>A. anamensis</em> and <em>A. afarensis</em> specimens, and even is among the deepest palates of later <em>Australopithecus</em> species. This challenges the long and widely-held view that Lucy’s species evolved gradually from <em>A. anamensis</em> without branching of the evolutionary line – a process known as <a href="https://en.wikipedia.org/wiki/Anagenesis">anagenesis</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=603&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=603&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=603&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=758&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=758&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290855/original/file-20190904-175710-fn9qtv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=758&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Facial reconstruction of MRD.</span>
<span class="attribution"><span class="source">Matt Crow, courtesy of the Cleveland Museum of Natural History. Facial reconstruction by John Gurche made possible through generous contribution by Susan and George Klein</span></span>
</figcaption>
</figure>
<p>Since these modern features were already present in the older species, the most likely scenario is that Lucy’s species formed by evolutionary divergence from <em>A. anamensis</em> – a process known as cladogenesis. It is not known though exactly when <em>A. afarensis</em> diverged. Further evidence for cladogenesis comes from a 3.9m years old <a href="https://www.sciencedirect.com/science/article/pii/0047248487900169">frontal bone</a> (part of the forehead) from Ethiopia, discovered in 1981. Its shape is different from MRD which suggests this fossil probably belongs to <em>A. afarensis</em>.</p>
<p>If that is the case, then we need to revise the human evolutionary timeline, with <em>A. anamensis</em> existing from 4.2m to 3.8m years ago, and <em>A. afarensis</em> from 3.9m to 3m years ago. This would imply that both species were overlapping for at least 100,000 years, making it impossible for <em>A. afarensis</em> to have evolved gradually from one single ancestral group. In fact, it is becoming increasingly obvious that most species on our evolutionary lineage likely evolved by branching off from existing groups. </p>
<h2>The human line</h2>
<p>The new discovery also challenges the idea of Lucy’s species being the ancestor of all later <em>Australopithecus</em> hominins, which eventually led to humans.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=807&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=807&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=807&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1014&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1014&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290858/original/file-20190904-175673-1smc6ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1014&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">MRD.</span>
<span class="attribution"><span class="source">Jennifer Taylor, courtesy of the Cleveland Museum of Natural History. Photography by Dale Omori and Liz Russell</span></span>
</figcaption>
</figure>
<p>A vertically straight and steeply rising curvature of the cheekbone has traditionally been considered to be a relatively modern feature. It was present in <em>Australopithecus africanus</em> (3.7m-2.1m years ago from southern Africa, considered by some to be a direct ancestor of the <em>Homo</em> lineage) and in <em>Paranthropus</em> (2.7m-1.2m years ago from southern and eastern Africa, not directly on our evolutionary line). </p>
<p>The opposite condition – a low and arched cheekbone – is considered to be primitive, and is shared among <em>A. afarensis</em>, <em>Ardipithecus ramidus</em> (4.3m-4.5m years ago from Ethiopia, a more ape-like primitive hominin) and African apes. </p>
<p>The crest of the MRD cranium, which is surprisingly modern, now challenges this view. It further opens up the possibility that the longstanding idea of <em>A. afarensis</em> as the ancestor of all later <em>Australopithecus</em> groups might have been wrong, and that instead <em>A. anamensis</em> is the ancestor to these younger species. Which early hominin is the direct ancestor of humans still remains an unanswered question.</p>
<p>Clearly this latest discovery has given new insights into our evolutionary past, but also increased the complexity of the relationships between early hominins. The mid Pliocene (5.3m-2.6m years ago) has become crowded with multiple, contemporary and geographically widespread species.</p>
<p>Clarifying the relationships between these species, confidently characterising their morphology, and deciphering the complex and intricate story about hominin evolution is not a simple task. Specimens at each new site capture a different point along the evolutionary trajectory, but it is not easy to convert these findings into stable and reliable branches on an evolutionary tree.</p>
<p>More specimens from time periods and geographical locations that are currently underrepresented in the fossil record could help to settle these questions, but could equally turn everything we know upside down.</p>
<p>Discoveries all over the world <a href="https://theconversation.com/homo-naledi-determining-the-age-of-fossils-is-not-an-exact-science-47840">in the last decade</a> have led to a complete <a href="https://theconversation.com/modern-humans-evolved-100-000-years-earlier-than-we-thought-and-not-just-in-east-africa-78875">rethinking of our evolutionary past</a>. It shows that new fossils do not always support existing hypotheses, and that we must be prepared to change our views and formulate new theories based on the evidence at hand.</p><img src="https://counter.theconversation.com/content/122926/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hester Hanegraef receives funding from the London NERC DTP (NE/L002485/1). </span></em></p>
The hominin known as Lucy may not be the direct ancestor of humans.
Hester Hanegraef, PhD Candidate of Anthropology, Natural History Museum
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/112672
2019-03-29T14:56:28Z
2019-03-29T14:56:28Z
Last of the giants: What killed off Madagascar’s megafauna a thousand years ago?
<figure><img src="https://images.theconversation.com/files/265740/original/file-20190325-36264-n5hk55.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A modern mouse lemur *Microcebus* sits upon the cranium of an extinct *Megaladapis* lemur.</span> <span class="attribution"><a class="source" href="https://www.daovanhoang.com">Dao Van Hoang www.daovanhoang.com</a></span></figcaption></figure><p>Giant 10-foot-tall elephant birds, with eggs eight times larger than an ostrich’s. Sloth lemurs bigger than a panda, weighing in at 350 pounds. A puma-like predator called the giant fosa.</p>
<p>They sound like characters in a child’s fantasy book, but along with dozens of other species, they once really roamed the landscape of Madagascar. Then, after millions of years of evolution in the middle of the Indian Ocean, the populations crashed in just a couple of centuries.</p>
<p>Scientists know that over the past 40,000 years, most of Earth’s megafauna – that is, animals human-size or larger – have gone extinct. Woolly mammoths, sabre tooth tigers and countless others no longer roam the planet.</p>
<p>What’s remarkable about the megafaunal crash in Madagascar is that it occurred not tens of thousands of years ago but just over 1,000 years ago, between A.D. 700 and 1000. And while some small populations survived a while longer, the damage was done in a relatively short amount of time. Why?</p>
<p>Over the last three years, new investigations into climate and land use patterns, human genetic diversity on the island and the dating of hundreds of fossils have fundamentally changed scientists’ understanding of the human and natural history of Madagascar. <a href="https://scholar.google.com/citations?user=M6TfcNkAAAAJ&hl=en&oi=ao">As two</a> <a href="https://scholar.google.com/citations?user=DUkXIeAAAAAJ&hl=en&oi=ao">paleoclimatologists and</a> <a href="https://scholar.google.com/citations?user=wAfh3EYAAAAJ&hl=en&oi=ao">a paleontologist</a>, we brought together this research with new evidence of megafaunal butchery. In doing so we’ve created <a href="https://doi.org/10.1016/j.jhevol.2019.03.002">a new theory</a> of how, why and when these Malagasy megafauna went extinct.</p>
<h2>Climate at the time of the crash</h2>
<p>The first job is to understand exactly when the megafauna died out.</p>
<p>Radiocarbon dating of <a href="https://doi.org/10.1111/ecog.02376">over 400 recent fossils</a> demonstrates that animals under 22 pounds lived on Madagascar throughout the last 10,000 years. For animals over 22 pounds, there are abundant fossils up to 1,000 years ago, but relatively few since. The biggest decline in number of large animals occurred rapidly between A.D. 700 and 1000 – practically instantaneous given the long history of their existence on the island. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1011&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1011&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1011&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Malagasy graduate student and team member Peterson Faina with stalagmites in a cave in Madagascar.</span>
<span class="attribution"><span class="source">Laurie Godfrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>What was the climate doing at that time? One popular theory for the megafaunal extinction has blamed <a href="https://doi.org/10.1111/j.1365-2699.2009.02203.x">island-wide drying</a>. To test this idea, our team has been exploring the caves of Madagascar, collecting and analyzing stalagmites. As stalagmites grow upwards from the cave floor, layer by layer, differences in the chemistry of each layer document changes in the climate outside the cave.</p>
<p>By analyzing chemical composition and comparing ratios of various isotopes in these stalagmites, we created new <a href="https://doi.org/10.1016/j.quascirev.2017.03.017">high-resolution records of changes in the Malagasy ecosystems and climate</a>. We found minor fluctuations in the strength of the summer rains throughout the last 2,000 years, but no significant drying over that period. In fact, A.D. 780-960 was one of the wettest periods of the last 2,000 years. <a href="https://doi.org/10.1111/ecog.02376">Chemical analyses of fossils</a> back up this claim.</p>
<p>So it looks like there was no significant drying around the time the megafauna disappeared.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many of the forests that originally existed on Madagascar are now replaced by more open, human-modified landscapes, like this palm savanna at Anjohibe.</span>
<span class="attribution"><span class="source">Laurie Godfrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Instead, the <a href="https://doi.org/10.1016/j.quascirev.2016.01.007">stalagmite records</a> indicated a rapid and dramatic change in the landscape. Changing ratios of the isotopes carbon-12 to carbon-13 reveal a switch from forests to grassland right around A.D. 900, the same time as the megafaunal population crash. Clearly something big happened around this time.</p>
<h2>Cut marks and evidence of butchery</h2>
<p>With no significant change in the climate, some point to the <a href="https://doi.org/10.1073/pnas.1534700100">arrival of humans</a> on the island as a possible cause of the megafauna population crash. It seems logical that once people arrived on Madagascar, they might have hunted the big animals into extinction. New data suggest that this timing doesn’t add up, though.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=736&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=736&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=736&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=924&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=924&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=924&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of two chop marks on the head of a femur of an extinct lemur, Pachylemur. This individual’s hind limb was removed from the trunk at the hip joint, probably with a machete.</span>
<span class="attribution"><span class="source">Lindsay Meador</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><a href="https://doi.org/10.1126/sciadv.aat6925">According to new dates on fossil bones</a> with cut marks on them, humans arrived on Madagascar 10,500 years ago, much earlier than previously believed. But whoever these early people were, there’s no genetic evidence of them left on the island. <a href="https://doi.org/10.1073/pnas.1704906114">New analysis of the human genetic diversity</a> in modern Madagascar suggests the current population derives primarily from two waves of migration: first from Indonesia 3,000 to 2,000 years ago, and later from mainland Africa 1,500 years ago.</p>
<p>So it seems that people lived alongside the megafauna for thousands of years. How did the humans interact with the large animals?</p>
<p>Our new study found dozens of fossils with butchery marks. Cut and chop marks provide compelling evidence as to which species people were hunting and eating. Evidence of butchery of animals that are now extinct continues right up to the time of the megafaunal crash. Some people on Madagascar hunted and ate the megafauna for millennia without a population crash.</p>
<h2>Evidence for a change in land use</h2>
<p>If there was no obvious climate shift and humans lived alongside and sustainably hunted the megafauna for up to 9,000 years, what could have triggered the population crash?</p>
<p>The abrupt land use change might hold some clues. The transition from a forest-dominated ecosystem to a grassland-dominated ecosystem appears to be widespread. Scientists have identified this switch not only in the chemical signature of stalagmites but also in pollen grains buried in layers of <a href="https://doi.org/10.1016/0033-5894(87)90038-X">mud at the bottom of lakes</a>. Ancient lake sediments reveal two other changes occurred at the same time as the shift to grass species: an increase in charcoal from fires and an increase in the fungus <em>Sporormiella</em>, which is associated with the dung of large herbivores <a href="https://doi.org/10.1073/pnas.1534700100">such as cows</a>.</p>
<p>Evidence for simultaneous increases in grassland, fires, and cows and other domesticated animals points to a sudden change in Malagasy lifestyle: the introduction of cattle husbandry and slash-and-burn agriculture known locally as <a href="https://www.madamagazine.com/en/english-tavy-kahlschlag-einer-insel/">Tavy</a>. Here, forests are cut down to make space for rice paddies, and grassland burned to promote the growth of nutritious seedlings for cow fodder.</p>
<p>This move away from foraging and hunting toward farming meant the land could support more people. The result was a rapid rise in the size of the human population – and that’s what we conclude spelled disaster for the megafauna.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some Malagasy farmers plow agricultural fields in the traditional way.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/malagasy-farmers-plowing-agricultural-field-traditional-266475566">Damian Ryszawy/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Here lies the contradiction of the situation: Hunting megafauna for survival became less important as people could rely on their agriculture and livestock. But cut marks on fossil bones indicate that hunting didn’t altogether stop just because people had other food sources. It turns out that the impact on the megafauna of larger human populations hunting just to supplement their diet was greater than the impact of smaller human populations relying more heavily on the native animals as a vital food source.</p>
<p>Bringing together new data on land use changes, climatic histories, genetics, fossil ages and butchery of the megafauna, we call this change “<a href="https://doi.org/10.1016/j.jhevol.2019.03.002">the subsistence shift hypothesis</a>.” Both the habitat loss and increase in human population arose out of a fundamental change in the way humans lived on Madagascar, from a more nomadic hunter-gatherer lifestyle to an agrarian society. We argue that it was this reorganization on Madagascar around A.D. 700-1000 that led to the crash in the megafaunal population.</p>
<p>Small populations of megafauna lived on in isolated pockets for another few centuries, but their fate was likely already sealed. The majority of the giant birds and animals that were once common across our planet have gone extinct. Many of the remaining giants, such as elephants and rhinos, are threatened or endangered. Will they go the same way as the Malagasy megafauna, casualties of humans’ changing lifestyles?</p><img src="https://counter.theconversation.com/content/112672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nick Scroxton receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Laurie Godfrey receives funding from the National Science Foundation BCS 1750598. </span></em></p><p class="fine-print"><em><span>Stephen Burns receives funding from the US National Science Foundation (grant AGS‐1702891/1702691).</span></em></p>
A series of new studies sheds light on the population crash and extinction of the giant birds, lemurs and more that roamed the island until around A.D. 700-1000.
Nick Scroxton, Postdoctoral Research Scholar in Paleoclimatology, UMass Amherst
Laurie Godfrey, Emeritus Professor of Anthropology, UMass Amherst
Stephen Burns, Professor of Geosciences, UMass Amherst
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/95572
2018-04-26T10:38:41Z
2018-04-26T10:38:41Z
Mother’s milk holds the key to unlocking an evolutionary mystery from the last ice age
<figure><img src="https://images.theconversation.com/files/216345/original/file-20180425-175050-1rnqanl.jpg?ixlib=rb-1.1.0&rect=550%2C202%2C3315%2C2231&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sunrise at noon in the Arctic. Little exposure to sun was a piece of the genetic puzzle.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Winter_Solstice_noon_sunrise_on_the_Bering_Sea_(8433692952).jpg">Bering Land Bridge National Preserve</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>As biologists explore the variation across the genomes of living people, they’ve found evidence of evolution at work. Particular variants of genes increase or decrease in populations through time. Sometimes this happens by chance. Other times these changes in frequency result from the gene’s helping or hindering individuals’ survival, a <a href="https://www.amnh.org/exhibitions/darwin/evolution-today/how-does-natural-selection-work">phenomenon known as selection</a>. If a gene conferred a survival advantage, people with the mutation would have more offspring and the mutation would become more common in subsequent generations.</p>
<p>Most of those past <a href="https://evolution.berkeley.edu/evolibrary/article/evo_25">episodes of selection</a> make sense, as they worked on genes involved with things like <a href="https://www.nature.com/scitable/topicpage/natural-selection-uncovering-mechanisms-of-evolutionary-adaptation-34539">resisting disease</a>, <a href="https://news.nationalgeographic.com/news/2004/02/0224_040225_evolution.html">blood oxygen levels at high altitudes</a>, and having <a href="https://www.nature.com/scitable/topicpage/evolutionary-adaptation-in-the-human-lineage-12397">paler skin at northern latitudes</a>.</p>
<p>However, researchers have also identified an episode of strong selection that doesn’t have such an obvious logic. It’s a mutation on a gene involved with the development of a suite of traits that don’t seem very similar at first glance: hair, teeth, sweat glands and breasts. This one was a mystery — what could have been the adaptive value of this mutation that led to it being common in northeastern Asia but nowhere else?</p>
<p><a href="https://scholar.google.com/citations?user=2B6GhHoAAAAJ&hl=en&oi=ao">My research</a> usually focuses on teeth, specifically genetic influences on their development. I came to this particular evolution puzzle when my colleagues and I gathered in Boston at the AAAS meeting last year to discuss the latest evidence of how people first migrated into the Western Hemisphere. We put together the clues about this episode of selection on human genetic variation – and found an example of <a href="https://doi.org/10.1073/pnas.1711788115">adaptation to life at high latitude during the last ice age</a>.</p>
<h2>Natural selection … of what?</h2>
<p>We were trying to understand selection for a mutation in the gene called EDAR – it encodes the ectodysplasin A receptor that plays a role in how tightly cells adhere to each other during the development of hair, teeth, sweat glands and breasts. All of these anatomical structures form via a very similar developmental process that happens while you’re still in your mother’s womb. Slight changes to the developmental mechanism results in the final differences between hair and teeth and sweat and mammary glands. But there is a fundamental similarity that, among other things, includes the activity of EDAR. </p>
<p>This shared development is especially obvious when things go wrong. For example, 1 in 10,000 newborns have a disorder called <a href="https://www.nfed.org/learn/">ectodermal dysplasia</a>, which causes disruption to the development of their hair, teeth, skin, sweat glands and breasts.</p>
<p>The V370A mutation that we focused on, the one that experienced strong selection, doesn’t disrupt development of these structures; rather, it augments them. People with V370A have thicker and straighter hair shafts, and their incisors have extra buttressing on the tongue side – a feature biologists call “shoveling.”</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216342/original/file-20180425-175035-1jkd39w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Human upper incisors with significant ‘shoveling’ on the tongue side.</span>
<span class="attribution"><span class="source">Christy G. Turner, II, courtesy G. Richard Scott</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>So why did this mutation provide such an advantage to people who carried it? Mice that have been experimentally induced to have the V370A mutation have thicker fur shafts and increased density of sweat glands. A previous study of modern human genomic variation <a href="https://doi.org/10.1016/j.cell.2013.01.016">interpreted the selection</a> to have occurred in northern China during the last ice age and focused on the sweat glands. The researchers suggested that the selection was for improved sweating that could help with regulating body temperature. But to my colleagues and me, that just didn’t feel like a convincing adaptive scenario given that this took place during the (cold) ice age. </p>
<p>Instead of the sweat glands, our attention was drawn to another trait. Mice with the V370A mutation also have an increase in the branching of their mammary ducts – the tiny tubes that intertwine with breast tissue and extract nutrients to make milk. Maybe it was this change in the breast tissue that was so valuable to people with this mutation?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216356/original/file-20180425-175058-ebxo40.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Christy G. Turner II, shown working in 1975, and his students assessed variation in incisor shoveling in over 30,000 people around the world. The current study relied on a subset of these data collected by co-author G. Richard Scott.</span>
<span class="attribution"><span class="source">G. Richard Scott and Joshua P. Carlson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Rather than trying to sample DNA from thousands of ancient people’s remains to see if they carried the mutation, we took advantage of the effect V370A has on human incisors. Relying on data collected over many years by my colleague <a href="https://scholar.google.com/citations?user=vtkFh8kAAAAJ&hl=en&oi=ao">G. Richard Scott</a> from the University of Nevada, Reno, our group looked at the dental variation of over 5,000 skeletons from archaeological sites in Europe, Asia and the Americas to get a sense of how this mutation varied through time.</p>
<p><a href="https://doi.org/10.1073/pnas.1711788115">We found that</a> all of the indigenous people living in the Western Hemisphere prior to European colonization had shovel-shaped incisors, which means they all likely had the V370A mutation. In contrast, only about 40 percent of the people in Asia had shovel-shaped incisors, and essentially no one in Europe did.</p>
<p>This pattern suggests that a population ancestral to Native Americans experienced the strong selection for V370A, an interpretation that differed from what my colleagues found when they only looked at genomic variation in living people. Using these ancient teeth, we were able to figure out when and where the selection happened. The next question we needed to address was why this selection occurred. What was going on to make this mutation so helpful and thus so much more prevalent?</p>
<h2>An ice age advantage</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216339/original/file-20180425-175047-1aqtxmn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Beringia outlined over today’s Siberia and Alaska.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:BeringiaMap-NPSgov.jpg">U.S. National Park Service</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><a href="https://doi.org/10.1371/journal.pone.0000829">Previous genetic work</a> found that Native Americans descend from a common ancestral population that lived in Beringia, the region that links Siberia and Alaska. During the dramatic climate change associated with the last ice age 28,000 to 18,000 years ago, plants and animals that had previously lived in Siberia took refuge in a circumscribed area called the Beringian Refugium. For about 5,000 years, they were genetically isolated from other populations because of a vast dry tundra to the west and a lot of ice to the east. <a href="https://doi.org/10.1002/evan.21478">The people who found haven there too</a> are referred to as the Beringian Standstill population.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216343/original/file-20180425-175050-1gs4hbz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Modern-day mesic shrub tundra near the northwestern Alaskan town of Kotzebue is similar to what the environment would have been like in Beringia during the ice age.</span>
<span class="attribution"><span class="source">Scott Elias</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>It’s not easy to live that far north. Sure, it’s cold. But more importantly, at high latitudes the sun is lower in the sky so sunlight must travel through more atmosphere to reach Earth’s surface. This journey through the atmosphere mostly filters out the Sun’s ultraviolet radiation. Most life forms need sun exposure to be healthy, in large part <a href="https://doi.org/10.1016/j.pbiomolbio.2006.02.016">because UV exposure induces</a> the <a href="https://www.mayoclinic.org/drugs-supplements-vitamin-d/art-20363792">body to make vitamin D</a>.</p>
<p><a href="https://doi.org/10.1073/pnas.0914628107">Lighter skin tones let in more UV</a> and have been selected for multiple times in human history. But once you get to the Arctic, skin depigmentation alone won’t suffice. In order to live with so little UV, people have culturally innovated, <a href="http://scienceline.org/2007/06/ask-dricoll-inuiteskimos/">eating diets rich in vitamin D</a>, such as oily fish. But nursing infants don’t eat these foods. Babies get their nutrients through their mother’s milk.</p>
<p>This is where our EDAR gene comes back into the picture. The V370A mutation in mice increases the branching density of the mammary ducts, and very likely does the same exact thing in human breasts. Scientists know that vitamin D deficient conditions <a href="https://doi.org/10.1016/j.jsbmb.2015.09.035">induce more ductal branching</a> during the breast development that happens with pregnancy. All of the evidence suggests that the increased ductal branching associated with V370A helped transfer nutrients from mother to infant through breast milk in a population that was extremely vitamin D deficient. </p>
<p>So the selection wasn’t for thicker hair or shovel-shaped incisors – instead, it was much more likely to have been on mammary ducts. The thicker hair and tooth variation just went along for the ride because they are created by the same basic developmental pathway. Selection on genetic variation in EDAR is probably related to health consequences for nursing infants rather than its effects on hair, teeth or sweat glands.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/216350/original/file-20180425-175061-1dkjjzs.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Excavation of a site occupied in Beringia 32,000 years ago.</span>
<span class="attribution"><span class="source">V. V. Pitul'ko & E. Yu. Pavlova</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Still traceable genetic inheritance</h2>
<p>Once the Earth started warming up at the end of the last ice age, those ice sheets started to melt, sea level rose and global climate became more humid. The people living in Beringia needed to move again. Some went east, populating the Western Hemisphere rapidly and extensively. Some went west, merging back into populations that were living in northern and eastern Asia. Scientists see traces of this migration today. The occurrence of incisor shoveling <a href="https://doi.org/10.1002/ajpa.1330740316">decreases as you move away from the Arctic</a>, there is <a href="https://doi.org/10.1371/journal.pone.0091722">evidence of a long-lost language</a>, and some of those Beringian Standstill mitochondrial DNA mutations <a href="https://doi.org/10.1371/journal.pone.0000829">can be found in Asian populations</a>.</p>
<p>Today, everyone with shovel-shaped incisors carries a little remnant of this ephemeral population with them and a reminder of the importance of the maternal-infant bond to human survival.</p>
<p>But they also have the other effects of the V370A mutation. The increase in mammary ductal branching seems likely to influence the transfer of nutrients from breast tissue into milk. It may also play a role in susceptibility to breast cancer, given that <a href="https://doi.org/10.2214/AJR.06.0619">breast density differs</a> between Asian and non-Asian women as does the <a href="https://doi.org/10.1093/jnci/djv048">occurrence of breast cancer</a>, a relationship that matches the distribution of V370A around the world today.</p>
<p>These ideas present exciting hypotheses to test in future studies. For now, our research shows that the bones of our ancestors can provide evidence of human adaptation, evidence that shifts our understanding of how genes work.</p><img src="https://counter.theconversation.com/content/95572/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Leslea Hlusko does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Why was one gene mutation that affects hair, teeth, sweat glands and breasts ubiquitous among ice age Arctic people? New research points to the advantage it provided for ancestors of Native Americans.
Leslea Hlusko, Associate Professor of Integrative Biology, University of California, Berkeley
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/79380
2017-06-20T12:56:56Z
2017-06-20T12:56:56Z
Decorated snail shell in a cave in Iraq could be evidence of Paleolithic bling
<figure><img src="https://images.theconversation.com/files/174754/original/file-20170620-32326-1t88mwq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Lost Mountain Studio via Shutterstock</span></span></figcaption></figure><p>Our excavations at <a href="http://www.smithsonianmag.com/arts-culture/the-skeletons-of-shanidar-cave-7028477/">Shanidar Cave</a> in north-eastern Iraq have produced a tiny shell plaque which was made by the first modern people in the region. This little object seems to have been made to ornament something showy, suggesting a very modern enjoyment of a bit of bling – but it also shows unexpected complexity. </p>
<p>Shanidar Cave in the Zagros Mountains is an important Neanderthal site. It was there in the 1950s that Ralph Solecki, an anthropologist from the Smithsonian Institution, unearthed the remains of ten Neanderthals – eight adult and two infant, thought to be between 65,000 and 35,000-years-old. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173676/original/file-20170613-30093-1p6snp7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shanidar Cave in summer.</span>
<span class="attribution"><span class="source">Chris Hunt</span></span>
</figcaption>
</figure>
<p>Some were complete skeletons but others were only a few bones. He thought most had been purposely buried because of their completeness. One became famous as the “<a href="http://science.sciencemag.org/content/190/4214/562">Shanidar flower burial</a>” – after pollen analyst <a href="https://www.scientificamerican.com/author/arlette-leroi-gourhan/">Arlette Leroi-Gourhan</a> found clumps of pollen from plants with medicinal properties in samples taken close to the skeleton. </p>
<p>Since 2014 a joint UK-Kurdish team, led by <a href="http://www.arch.cam.ac.uk/directory/gb314">Graeme Barker</a>, <a href="http://www.bbk.ac.uk/history/our-staff/academic-staff/dr-tim-reynolds">Tim Reynolds</a> and me, with members from Cambridge, Liverpool John Moores, Birkbeck, Queen’s Belfast and the Kurdish Antiquities Department, have been <a href="http://antiquity.ac.uk/projgall/barker348">re-investigating the cave</a>. We aim to clarify the sequence of deposits, work out the age of the Neanderthal remains, establish whether they were indeed buried and <a href="http://www.sciencedirect.com/science/article/pii/S0034666715001724">whether flowers were involved</a>. During this work, our small but careful excavations have yielded large quantities of cultural debris as well as new Neanderthal <a href="http://eprints.bbk.ac.uk/18915/">remains</a>. </p>
<h2>The Baradostian</h2>
<p>One of our more important finds is a shell plaque from Upper Palaeolithic layers. The local Upper Palaeolithic stone tool industry is <a href="https://www.britannica.com/topic/Baradostian-industry">called the Baradostian</a>, dating from about 36,000BC – and elsewhere in the region this industry is associated with the remains of anatomically modern humans. </p>
<p>In 2009, American anthropologists <a href="https://www.ncbi.nlm.nih.gov/pubmed/19660782">Jeremiah Scott and Curtis Marean</a> reported the discovery of butchered and burnt partial remains of two adults and two juveniles at <a href="http://www.sciencedirect.com/science/article/pii/S0047248409001080">Eshkaft-e Gavi</a>, a cave in the southern Zagros Mountains, in levels containing Baradostian artefacts. Tsenka Tsanova – a Bulgarian stone tool specialist – found a modern human molar in basal Baradostian layers at <a href="http://www.sciencedirect.com/science/article/pii/S0047248413001152">Warwasi</a> in western Iran. The tooth was in the lowest Baradostian level, so Tsanova concluded that it confirmed the association between modern humans and the Baradostian. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174696/original/file-20170620-24901-gzbn6y.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Excavations at Shanidar Cave showing the location of artefacts.</span>
<span class="attribution"><span class="source">Chris Hunt</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>At Shanidar, the Baradostian layers are a couple of metres thick and contain enormous quantities of cultural material, including stone tools, animal bones and land snail shells. </p>
<p>They overlie thick layers containing Middle Palaeolithic <a href="https://www.britannica.com/topic/Mousterian-industry">Mousterian</a> stone tools (typically made using <a href="http://www.anth.ucsb.edu/faculty/stsmith/classes/anth3/courseware/LithicTech/8_Middle_Paleolithic_Tool.html">Levallois</a> removal methods rather than the <a href="http://news.bbc.co.uk/1/hi/sci/tech/7582912.stm">blade technology</a> of the Upper Palaeolithic) and the now-famous Neanderthals.</p>
<h2>The shell plaque</h2>
<p>The plaque we found is very small and made of the shell of the land snail <em>Assyriella</em>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=386&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=386&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=386&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173677/original/file-20170613-11089-1wom32z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Assyriella</em></span>
<span class="attribution"><span class="source">Evan Hill</span></span>
</figcaption>
</figure>
<p>The plaque is nearly rectangular and measures 9.2mm x 4.6mm. Both sides of this object bear incisions which are unlikely to be natural. On the inner side of the shell, they were made in a rectangular pattern using a sharp stone point with a triangular tip. Three of the edges appear to have been snapped off along incisions. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173678/original/file-20170613-30089-4xh93k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The inner side of the plaque showing incisions (1000 microns = 1 mm).</span>
<span class="attribution"><span class="source">Chris Hunt</span></span>
</figcaption>
</figure>
<p>On the outer side of the shell, the incisions cut across the natural striations, but this side shows pitting from contact with a corrosive substance.</p>
<p>Piercing or the removal of the apex of the shell is typical of damage made while <a href="http://www.sciencedirect.com/science/article/pii/S2352409X15301085">eating land snails</a> which were a regular part of the prehistoric <a href="http://www.gugumuck.at/wp-content/uploads/2016/07/Prehistoric-edible-land-snails-in-the-Prehistoric-edible-land-snails-in-the-circum-Mediterranean-the-archaeological-evidence-David-LUBELL-2004.pdf">diet</a> in this area. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=351&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=351&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=351&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=441&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=441&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173679/original/file-20170613-17566-1e9u7xm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=441&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Outside of the plaque showing incisions across striations. Scale in microns.</span>
<span class="attribution"><span class="source">Chris Hunt</span></span>
</figcaption>
</figure>
<p>The shell of the land snail is too soft and the object too small for the incisions to have been made while the plaque was being used as an anvil for cutting other material as was <a href="http://www.sciencedirect.com/science/article/pii/S004724849790141X">suggested for other larger and stronger incised pieces</a>. </p>
<p>We conclude that the piece was produced purposely as part of the making of an object for display. </p>
<p>The shiny, bright white interior of the snail shell would have been conspicuous and we guess that little pieces of shell were snapped off and applied to an item of clothing or a wooden object. This might have given an effect rather like that achieved by the cockney Pearly Kings and Queens – a traditional, largely ageing group of working-class Londoners who take to the streets in clothes highly decorated with mother of pearl buttons. </p>
<h2>Highly visual culture</h2>
<p>The Upper Palaeolithic in Europe and west Asia is well known for composite technology, using stone set in wooden or bone hafts to make complex tools and weapons. It is marked also by the use of personal ornament, including <a href="https://www.researchgate.net/publication/303837076_Systems_of_personal_ornamentation_in_the_Early_Upper_Palaeolithic_Methodological_challenges_and_new_observations">pierced teeth and shells</a> worn strung or perhaps sewn to clothing. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=433&fit=crop&dpr=1 754w, https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=433&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/173680/original/file-20170613-30067-e412e8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=433&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Coat of a Pearly King.</span>
<span class="attribution"><a class="source" href="http://www.horniman.ac.uk/visit/past-exhibitions/object-in-focus-pearly-king#image-0">Horniman Museum</a></span>
</figcaption>
</figure>
<p>It is also notable for other visual expressions such as <a href="http://iopscience.iop.org/article/10.1088/0957-0233/14/9/301/meta">cave paintings</a> for instance at Chauvet Cave in France, <a href="https://www.nature.com/nature/journal/v459/n7244/full/nature07995.html">statuettes</a> including the <a href="https://www.google.com/culturalinstitute/beta/asset/-/FQFjN-ceyNAg3w?hl=en-GB&ms=%7B%22x%22%3A0.5%2C%22y%22%3A0.5%2C%22z%22%3A8.719043686168943%2C%22size%22%3A%7B%22width%22%3A3.216634615384617%2C%22height%22%3A1.2375000000000007%7D%7D">Venus of Willendorf</a>, carvings and the use of <a href="https://www.nature.com/nature/journal/v444/n7117/full/444285a.html">ochre in burials</a> for instance at Krems-Wachtberg in Lower Austria, and in the UK the so-called <a href="http://www.bradshawfoundation.com/british_isles_prehistory_archive/red_lady_paviland/index.php">Red Lady of Paviland</a> found in Wales and thought to be the oldest remains recovered in the UK. But while the tools and weapons of the period were the result of complex manufacturing processes, the ornamental items so far found have been made from single objects.</p>
<p>We suspect that this little shell plaque is another, highly unusual, manifestation of this tradition of visual display. This may be one of the first cases of Upper Palaeolithic people using composite technology to make ornamental items to make themselves look good.</p><img src="https://counter.theconversation.com/content/79380/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris O Hunt receives funding from Leverhulme Trust under RPG-2013-105. </span></em></p>
The early human ‘Cockney pearly kings and queens’.
Chris Hunt, Professor of Cultural Palaeoecology, Liverpool John Moores University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/77231
2017-05-08T15:27:44Z
2017-05-08T15:27:44Z
Brain-imaging modern people making Stone Age tools hints at evolution of human intelligence
<figure><img src="https://images.theconversation.com/files/168412/original/file-20170508-20729-j1gfbg.jpg?ixlib=rb-1.1.0&rect=0%2C349%2C4330%2C3096&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The stone flakes are flying, but what brain regions are firing?</span> <span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>How did humans get to be so smart, and when did this happen? To untangle this question, we need to know more about the intelligence of our human ancestors who lived 1.8 million years ago. It was at this point in time that a new type of stone tool hit the scene and the human brain nearly doubled in size. </p>
<p>Some researchers have suggested that this more advanced technology, coupled with a bigger brain, implies a higher degree of intelligence and perhaps even the first signs of language. But all that remains from these ancient humans are fossils and stone tools. Without access to a time machine, it’s difficult to know just what cognitive features these early humans possessed, or if they were capable of language. Difficult – but not impossible.</p>
<p>Now, thanks to cutting-edge brain imaging technology, my interdisciplinary research team is learning just how intelligent our early tool-making ancestors were. By scanning the brains of modern humans today as they make the same kinds of tools that our very distant ancestors did, we are <a href="http://nature.com/articles/doi:10.1038/s41562-017-0102">zeroing in on what kind of brainpower is necessary</a> to complete these tool-making tasks.</p>
<h2>A leap forward in stone tool technology</h2>
<p>The stone tools that have survived in the archaeological record can tell us something about the intelligence of the people who made them. Even our earliest human ancestors were no dummies; there is evidence for stone tools as early as <a href="https://doi.org/10.1038/nature14464">3.3 million years ago</a>, though they were probably making tools from perishable items even earlier. </p>
<p>As early as <a href="https://doi.org/10.1038/385333a0">2.6 million years ago</a>, some small-bodied and small-brained human ancestors chipped small flakes off of larger stones to use their sharp cutting edges. These types of stone tools belong to what is known as the <a href="http://www.stoneageinstitute.org/pdfs/oldowan-ch1-schick-toth.pdf">Oldowan industry</a>, named after <a href="http://www.olduvai-gorge.org/aboutus.html">Olduvai Gorge</a> in Tanzania, where remains of some of the earliest humans and their stone implements have been found.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=530&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=530&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=530&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=666&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=666&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168149/original/file-20170505-19124-13y70ao.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=666&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The more basic Oldowan chopper (left) and the more advanced Acheulian handaxe (right).</span>
<span class="attribution"><span class="source">Shelby S. Putt, courtesy of the Stone Age Institute</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Around 1.8 million years ago, also in East Africa, a new type of human emerged, one with a larger body, a larger brain and a new toolkit. This toolkit, called the <a href="https://doi.org/10.1073/pnas.1221285110">Acheulian industry</a>, consisted of shaped core tools that were made by removing flakes from stones in a more systematic manner, leading to a flat handaxe with sharp edges all the way around the tool.</p>
<p>Why was this novel Acheulian technology so important for our ancestors? At a time <a href="https://doi.org/10.1126/science.1236828">when the environment and food resources were somewhat unpredictable</a>, early humans probably began to rely on technology more often to access food items that were more difficult to obtain than, say, low-hanging fruits. Meat, underground tubers, grubs and nuts may all have been on the menu. Those individuals with the better tools gained access to these energy-dense foods, and they and their offspring reaped the benefits. </p>
<p><a href="https://doi.org/10.1098/rstb.2011.0099">One group of researchers</a> has suggested that human language may have evolved by piggybacking on a preexisting brain network that was already being used for this kind of complex tool manufacture.</p>
<p>So were the Acheulian toolmakers smarter than any human relative that lived prior to 1.8 million years ago, and is this potentially the point in human evolution when language emerged? We used a neuroarchaeological approach to answer these questions.</p>
<h2>Imaging brain activity now to reconstruct brain activity in the past</h2>
<p>My research team, which consists of paleoanthropologists at the <a href="http://www.stoneageinstitute.org/staff.html">Stone Age Institute</a> and the <a href="https://clas.uiowa.edu/anthropology/people/robert-g-franciscus">University of Iowa</a> and <a href="https://www.uea.ac.uk/psychology/people/profile/s-wijeakumar">neuroscientists</a> at the <a href="https://www.uea.ac.uk/psychology/people/profile/j-spencer">University of East Anglia</a>, recruited modern human beings – all we have at our disposal these days – whose brains we could image while they made Oldowan and Acheulian stone tools. Our volunteers were recreating the behaviors of early humans to make the same types of tools they made so long ago; we can assume that the areas of their modern human brains that light up when making these tools are the same areas that were activated in the distant past.</p>
<p>We used a brain imaging technology called <a href="http://www.sciencedirect.com/science/journal/10538119/85/part/P1">functional near-infrared spectroscopy</a> (fNIRS). It is unique among brain imaging techniques because it allows the person whose brain is being imaged to sit up and move her arms, unlike other techniques that do not allow any movement at all.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168414/original/file-20170508-20740-iavw90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Participants in the study made stone tools while their brain activity was measured with fNIRS.</span>
<span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Each of the subjects who participated in this study attended multiple training sessions to learn how to make Oldowan and Acheulian tools before going in for the final test – making tools while hooked up to the fNIRS system. </p>
<p>We needed to control for language in the design of our experiment to test the idea that language and tool-making share a common circuit in the brain. So we divided the participants into two groups: One learned to make stone tools via video with language instructions; the other group learned via the same videos, but with the audio muted, so without language.</p>
<p>If language and tool-making truly share a co-evolutionary relationship, then even those participants who were placed in the nonverbal group should still use language areas of the brain while making a stone tool. This is the result we should expect if language processing and stone tool production require the same neural circuitry in the brain. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7W_iR1T2r6I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Training video shown to participants. The verbal group heard the instructor’s voiced instructions, while the nonverbal group watched a muted version.</span></figcaption>
</figure>
<p>During the neuroimaging session, we had the participants complete three tasks: a motor baseline task during which they struck two round stones together without attempting to make flakes; an Oldowan task that involved making simple flakes without trying to shape the core; and an Acheulian task where they attempted to shape the core into a handaxe through a more advanced flake removal procedure.</p>
<h2>The evolution of human-like cognition</h2>
<p><a href="http://nature.com/articles/doi:10.1038/s41562-017-0102">What we found</a> was that only the participants who learned to make stone tools with language instruction used language processing areas of the brain. This probably means that they were recalling verbal instructions they’d heard during their training sessions. That explains why <a href="https://doi.org/10.1098/rstb.2008.0001">earlier studies</a> that did not control for language instruction in their experiment design found that stone tool production activates language processing areas of the brain. Those language areas lit up not because of anything intrinsic to making stone tools, but because while participants worked on the tools they also were likely playing back in their minds the language-based instruction they’d received.</p>
<p>Our study showed that people could make stone tools without activating language-related brain circuits. That means, then, that we can’t confidently state at this point that stone tool manufacture played a major role in the evolution of language. When exactly language made its appearance is therefore still a mystery to be solved. </p>
<p>We also discovered that Oldowan tool-making mainly activates brain areas involved in visual inspection and hand movement. More advanced Acheulian tool-making recruits a higher-order cognitive network that spans across a large portion of the cerebral cortex. This Acheulian cognitive network is involved in higher-level motor planning and holding in mind multi-sensory information using <a href="https://www.simplypsychology.org/working%20memory.html">working memory</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=194&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=194&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=194&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=243&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=243&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168416/original/file-20170508-20761-1n0jopz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=243&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Areas of the brain that form the Acheulian cognitive network that are also active when trained pianists play the piano.</span>
<span class="attribution"><span class="source">Shelby S. Putt</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>It turns out that this Acheulian cognitive network is the same one that comes online <a href="https://doi.org/10.1016/j.neuroimage.2005.10.044">when a trained pianist plays the piano</a>. This does not necessarily mean that early humans could play Chopin. But our result may mean that the brain networks we rely on today to complete complex tasks involving multiple forms of information, such as playing a musical instrument, were likely evolving around 1.8 million years ago so that our ancestors could make relatively complex tools to exploit energy-dense foods.</p><img src="https://counter.theconversation.com/content/77231/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shelby Putt received funding from the Leakey Foundation, the Wenner-Gren Foundation, and Sigma Xi, the Scientific Research Society, and the American Association of University Women. </span></em></p>
We can’t observe the brain activity of extinct human species. But we can observe modern brains doing the things that our distant ancestors did, looking for clues about how ancient brains worked.
Shelby Putt, Postdoctoral Research Fellow, The Stone Age Institute and The Center for Research into the Anthropological Foundations of Technology, Indiana University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/76967
2017-05-04T22:18:47Z
2017-05-04T22:18:47Z
Behind closed doors: What the Piltdown Man hoax from 1912 can teach science today
<figure><img src="https://images.theconversation.com/files/167589/original/file-20170502-17267-1pa48wd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When new discoveries are jealously guarded under lock and key, science suffers.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/rightee/260028769">Andy Wright</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>In 1912, Charles Dawson, an amateur archaeologist in England, claimed he’d made one of the most important fossil discoveries ever. Ultimately, however, his “Piltdown Man” proved to be a hoax. By cleverly pairing a human skull with an orangutan’s jaw – stained to match and give the appearance of age – a mysterious forger duped the scientific world.</p>
<p>In the decades between the find’s unearthing and the revelation it was fraudulent, people in the United States and around the world learned about Piltdown Man as a “missing link” connecting ape and man. Newspaper articles, scientific publications <a href="http://www.hup.harvard.edu/catalog.php?isbn=9780674660410">and museum exhibitions</a> all presented Piltdown Man as a legitimate scientific discovery supporting a particular vision of human evolution.</p>
<p>Historians, science writers and others have <a href="https://www.amazon.com/Piltdown-Scientific-Forgery-Frank-Spencer/dp/0198585225">investigated the Piltdown Man controversy</a> over the years, shedding <a href="https://global.oup.com/academic/product/the-piltdown-forgery-9780198607809?q=Piltdown&lang=en&cc=us">new light on the fraud</a>. As we reconsider the nature of “<a href="http://www.cnn.com/2017/01/22/politics/kellyanne-conway-alternative-facts/">facts</a>,” “<a href="https://www.theguardian.com/media/2016/dec/18/what-is-fake-news-pizzagate">fake news</a>” and knowledge production, it’s worthwhile to revisit the Piltdown Man episode.</p>
<p>At issue was not just the deliberate hoax, but also the incomplete flow of information about the purported human ancestor. Soon after the discovery, access to the original materials in England was cut off by a few gatekeepers. Science is suffocated when researchers are unable to reliably corroborate claims made by others. The same issues arise today, with the research community grappling with what’s been called a <a href="http://www.nature.com/news/reproducibility-1.17552">reproducibility crisis</a>; scientists need access to evidence and data in order to replicate (or not) research results. The Piltdown Man controversy lends support to the modern <a href="https://osf.io/preprints/psyarxiv/ak6jr">open science movement</a>, with its call for transparency at every step of the scientific process. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=438&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=438&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=438&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167586/original/file-20170502-17285-1pjrddd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Piltdown Man believers kept tight control over who could get an up-close look at the fossils. Arthur Keith is pictured in the white coat, Charles Dawson over his left shoulder.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Piltdown_gang_(dark).jpg">John Cooke</a></span>
</figcaption>
</figure>
<h2>Limited firsthand access</h2>
<p>Experts immediately cited the discovery of a large human-like cranium with a primitive-looking, ape-like jaw as a major breakthrough. Influential anatomists such as Sir Arthur Keith hailed Piltdown Man as authentic. The popular press on both sides of the Atlantic described prehistoric archaeology as a dramatic hunt for a missing link and came to embrace Piltdown Man within an oversimplified framework of human evolution.</p>
<p>But there were some scientists – notably British Museum curator Reginald A. Smith – who were skeptical from the outset. Doubters noted the major find was attributed to a previously little-known archaeologist.</p>
<p>Curators in the United States impatiently hoped to learn more. But transatlantic requests were denied by their counterparts in Britain who controlled access to the cranium and jaw, moving the bones to a secure vault at the Museum of Natural History in London. Rumors swirled. </p>
<p>Controversial Smithsonian curator <a href="http://anthropology.si.edu/naa/fa/Hrdlicka_Ales.pdf">Aleš Hrdlička describes in an annual report</a> traveling to England himself:</p>
<blockquote>
<p>“Regrettably… the specimen was not yet available for examination by outsiders, and so no original opinion can be given concerning its status. It represents doubtless one of the most interesting finds relating to man’s antiquity, though seemingly the last word had not yet been said as to its date and especially as to the physical characteristics of the being it stands for.”</p>
</blockquote>
<p>Early in the 20th century, provocative claims about discoveries commonly circulated through letters, rumors and splashy newspaper articles suggesting major new finds. American museums were simultaneously intrigued and frustrated by word of significant finds like Piltdown Man. Some claims proved to be genuine, while many others were found to be falsified or misleading. With limited information, it was especially difficult to determine the validity of claims made by scientists abroad.</p>
<p>News about major discoveries might change planned exhibitions about human evolution or prehistory at museums in New York or Chicago, or influence what students were taught about human history. Uncertainty plagued museums in this regard, as their scientists tried to view skeletons firsthand on visits to European museums and to secure good casts or copies for their own collections. Even amid growing doubts, a major exhibition in San Diego that opened in 1915 <a href="http://www.hup.harvard.edu/catalog.php?isbn=9780674660410">prominently featured a Piltdown Man sculpture</a>.</p>
<h2>What’s the damage done?</h2>
<p>This lack of transparency resulted in an absence of accurate information in the scientific community.</p>
<p>It ultimately took until the later decades of the 20th century for the Piltdown bones to be fully discredited. The hoax was <a href="https://theconversation.com/solving-the-piltdown-man-crime-how-we-worked-out-there-was-only-one-forger-63615">likely created by Dawson himself</a>, though <a href="https://www.amazon.com/Piltdown-Men-Ronald-William-Millar/dp/057500536X">who exactly concocted the scam is still debated</a> – “Sherlock Holmes” author <a href="http://www.telegraph.co.uk/science/2016/08/10/sir-arthur-conan-doyle-cleared-of-piltdown-man-hoax/">Arthur Conan Doyle’s name has even been mentioned</a> as a <a href="https://theconversation.com/a-new-twist-to-whodunnit-in-sciences-famous-piltdown-man-hoax-64470">possible perpetrator</a>.</p>
<p>As Berkeley anthropologist <a href="http://anthropology.si.edu/naa/fa/spencer.pdf">Sherwood Washburn offered in a letter</a>, “My opinion is that if more people had seen the originals sooner the fake would have been recognized.” Confusion had arisen because <a href="https://www.youtube.com/watch?v=2LtOkhpR3hY">so few scholars were granted access</a> to the original evidence.</p>
<p>Part of what finally put Piltdown Man to rest was the nature of new discoveries emerging. They informed researchers’ developing understanding of the human past and began turning much scientific attention away from Europe toward Asia and Africa.</p>
<p>While it is impossible to know with certainty, the Piltdown Man episode likely slowed scientific progress in the global search for human ancestors. What is clear is that the claims worked to muddle popular knowledge about human evolution.</p>
<h2>Piltdown Man’s lessons for today</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=587&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=587&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=587&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=738&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=738&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167590/original/file-20170502-17267-1l3115g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=738&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Museums still display Piltdown Man replicas, not as science but as cautionary reminder.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Sterkfontein_Piltdown_man.jpg">Anrie</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The unknown forger behind Piltdown Man intentionally misled the world about human evolution. The false claims rippled through the news media and museum exhibitions. Without access to reliable sources, in this case the original bones, the fraudulent story of Piltdown Man spread like a slowly building wildfire. </p>
<p>The Piltdown Man controversy hints at the dangers of drawing conclusions based on limited or emerging information, for both the public and scientists. In some ways, the whole episode foreshadowed threats we face now <a href="http://www.slate.com/blogs/future_tense/2017/04/13/facebook_s_latest_attempt_to_fight_fake_news_makes_it_seem_more_helpless.html">from fake news</a> and the spread of misinformation about science and many other topics. It is hard to get to the truth – whether about a news story or scientific theory – without access to the evidence supporting it.</p>
<p>Certainly new information flows much more rapidly today – thanks to the internet and social media – potentially a partial corrective to the problems connected to misleading claims. However, scientists and others still need access to accurate and reliable information from original sources. With the Piltdown Man remains locked away in a secure museum vault, speculation and misinformation flourished.</p>
<p>Support is now building for an <a href="http://www.digital-scholarship.org/cwb/WhatIsOA.htm">open access</a> research model: When possible and appropriate, original materials, data and preliminary findings should be made available to others in the field. Scientists also work to balance <a href="https://www.theguardian.com/science/2015/oct/25/discovery-human-species-accused-of-rushing-errors">how quickly they publish new research</a>: It takes time to do careful work, but keeping finds hidden away for too long also impedes progress and understanding. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167785/original/file-20170503-21649-1x026xi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Excavations continue in the hobbit cave in Indonesia.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/12394349@N06/14748473277">Bryn Pinzgauer</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Consider a 2003 find from Indonesia that was as shocking as the discovery of Piltdown Man: a nearly complete female skeleton researchers suggested was from a tiny human ancestor they called <a href="http://humanorigins.si.edu/evidence/human-fossils/species/homo-floresiensis">Homo floresiensis</a> (commonly nicknamed “hobbit”). Media speculation ran wild early on about this new species added to our family tree, but paleoanthropology has evolved a great deal since Piltdown Man.</p>
<p>Scientists from several different groups worked to <a href="http://www.livescience.com/29100-homo-floresiensis-hobbit-facts.html">understand the discovery</a> – seeking related finds and going back to the original fossils to systematically assess the claim. Soon additional <a href="https://dx.doi.org/10.1038/nature02999">detailed scientific publications began to emerge</a>, allowing the scientific community to continue <a href="https://dx.doi.org/10.1038/nature04022">to add to the evidence</a> and better <a href="https://dx.doi.org/10.1038/4311029a">scrutinize the discovery</a>. To date, the teeth of at many as 12 individuals have been found.</p>
<p>Homo floresiensis are likely a genuinely groundbreaking discovery – hopefully the more transparent way the research unfolded makes this easier to untangle than Dawson’s claims a century ago. Thoughtful collaboration, making data available openly, more effective <a href="https://www.theguardian.com/science/political-science/2016/may/10/what-has-science-communication-ever-done-for-us">popular science communication</a> and multiple channels of accurate information may help us better respond to the next Piltdown Man.</p><img src="https://counter.theconversation.com/content/76967/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samuel Redman does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
A century-old case of scientific fraud illustrates how hard it is to untangle the truth when access to new discoveries is limited.
Samuel Redman, Assistant Professor of History, UMass Amherst
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/69662
2017-01-08T07:15:20Z
2017-01-08T07:15:20Z
How forensic science can unlock the mysteries of human evolution
<figure><img src="https://images.theconversation.com/files/384828/original/file-20210217-19-1n30rlo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rock art.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/handprints-time-694438030">Zach Snavely/Shutterstock</a></span></figcaption></figure><p>People are fascinated by the use of forensic science to solve crimes. Any science can be forensic when used in the criminal and civil justice system – biology, genetics and chemistry have been applied in this way. Now something rather special is happening: the scientific skill sets developed while investigating crime scenes, homicides and mass fatalities are being put to use outside the courtroom. Forensic anthropology is one field where this is happening.</p>
<p>Loosely defined, forensic anthropology is the analysis of human remains for the purpose of establishing identity in both living and dead individuals. In the case of the dead this often focuses on analyses of the skeleton. But any and all parts of the physical body can be analysed. The forensic anthropologist is an expert at assessing biological sex, age at death, living height and ancestral affinity from the skeleton. </p>
<p>Our newest research has extended forensic science’s reach from the present into prehistory. In the study, <a href="http://www.sciencedirect.com/science/article/pii/S0305440316301649">published</a> in the <em>Journal of Archaeological Science</em>, we applied common forensic anthropology techniques to investigate the biological sex of artists who lived long before the invention of the written word.</p>
<p>We specifically focused on those who produced a type of art known as a hand stencil. We applied forensic biometrics to produce statistically robust results which, we hope, will offset some of the problems archaeological researchers have encountered in dealing with this ancient art form. </p>
<h2>Rock art</h2>
<p>Ancient hand stencils were made by blowing, spitting or stippling pigment onto a hand while it was held against a rock surface. This left a negative impression on the rock in the shape of the hand.</p>
<p>These stencils are frequently found alongside pictorial cave art created during a period known as the <a href="http://archaeology.about.com/od/upperpaleolithic/qt/Upper-Paleolithic.htm">Upper Palaeolithic</a>, which started roughly 40 000 years ago.</p>
<p>Archaeologists have long been interested in such art. The presence of a human hand creates a direct, physical connection with an artist who lived millennia ago. Archaeologists have often focused on who made the art – not the individual’s identity, but whether the artist was male or female. </p>
<p>Until now, researchers have focused on studying hand size and finger length to address the artist’s sex. The size and shape of the hand is influenced by biological sex as sex hormones determine the relative length of fingers during development, known as <a href="https://www.researchgate.net/publication/38060397_Heritability_of_digit_ratio_2D4D_in_rhesus_macaques_Macaca_mulatta">2D:4D ratios</a>. </p>
<p>But many ratio-based studies applied to rock art have generally been difficult to replicate. They’ve often produced conflicting results. The problem with focusing on hand size and finger length is that two differently shaped hands can have identical linear dimensions and ratios.</p>
<p>To overcome this we adopted an approach based on forensic biometric principles. This promises to be both more statistically robust and more open to replication between researchers in different parts of the world.</p>
<p>The study used a branch of statistics called <a href="http://www.virtual-anthropology.com/">Geometric Morphometric Methods</a>. The underpinnings of this discipline date back to the <a href="http://www.darcythompson.org/about.html">early 20th century</a>. More recently computing and digital technology have allowed scientists to capture objects in 2D and 3D before extracting shape and size differences within a common spatial framework. </p>
<p>In our study we used experimentally produced stencils from 132 volunteers. The stencils were digitised and 19 anatomical landmarks were applied to each image. These correspond to features on the fingers and palms which are the same between individuals, as depicted in figure 2. This produced a matrix of x-y coordinates of each hand, which represented the shape of each hand as the equivalent of a map reference system. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=778&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=778&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=778&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=978&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=978&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150987/original/image-20161220-26710-1umes6m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=978&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Figure 2. Geometric morphometric landmarks applied to an experimentally produced hand stencil. This shows the 19 geometric landmarks applied to a hand.</span>
<span class="attribution"><span class="source">Emma Nelson, University of Liverpool</span></span>
</figcaption>
</figure>
<p>We used a technique called <a href="http://www.virtual-anthropology.com/virtual-anthropology/geometric-morphometrics/procrustes-superimposition">Procrustes superimposition</a> to move and translate each hand outline into the same spatial framework and scale them against each other. This made the difference between individuals and sexes objectively apparent. </p>
<p>Procrustes also allowed us to treat shape and size as discrete entities, analysing them either independently or together. Then we applied discriminant statistics to investigate which component of hand form could best be used to assess whether an outline was from a male or a female. After discrimination we were able to predict the sex of the hand in 83% of cases using a size proxy, but with over 90% accuracy when size and shape of the hand were combined. </p>
<p>An analysis called Partial Least Squares was used to treat the hand as discrete anatomical units; that is, palm and fingers independently. Rather surprisingly the shape of the palm was a much better indicator of the sex of the hand than the fingers. This goes counter to received wisdom. </p>
<p>This would allow us to predict sex in hand stencils which have missing digits - a common issue in Palaeolithic rock art - where whole or part fingers are often missing or obscured.</p>
<h2>Palaeo-forensics</h2>
<p>This study adds to the body of research that has already used forensic science to understand prehistory. Beyond rock art, forensic anthropology is helping to develop the emergent field of palaeo-forensics: the application of forensic analyses into the deep past. </p>
<p>For instance, we have been able to understand <a href="http://www.nature.com/articles/srep15120">fatal falls</a> in <em>Australopithecus sediba</em> from Malapa and <a href="http://sajs.co.za/mournful-ape-conflating-expression-and-meaning-mortuary-behaviour-homo-naledi/patrick-s-randolph-quinney">primitive mortuary practices</a> in the species <em>Homo naledi</em> from <a href="https://elifesciences.org/content/4/e09561">Rising Star Cave</a>, both in South Africa.</p>
<p>All of this shows the synergy that arises when the palaeo, archaeological and forensic sciences are brought together to advance humans’ understanding of the past.</p><img src="https://counter.theconversation.com/content/69662/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
New ways of using forensic science in anthropology have been developed to advance our understanding of the past.
Patrick Randolph-Quinney, Associate Professor, Northumbria University, Newcastle
Anthony Sinclair, Professor of Archaeological Theory and Method, University of Liverpool
Emma Nelson, Lecturer in Clinical Communication, University of Liverpool
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/65570
2016-09-16T12:39:15Z
2016-09-16T12:39:15Z
Sorry David Attenborough, we didn’t evolve from ‘aquatic apes’ – here’s why
<figure><img src="https://images.theconversation.com/files/138054/original/image-20160916-6332-1t9bve0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Michael Rosskothen / shutterstock</span></span></figcaption></figure><p>Occasionally in science there are theories that refuse to die despite the overwhelming evidence against them. The “aquatic ape hypothesis” is one of these, now championed by Sir David Attenborough in his recent BBC Radio 4 series <a href="http://www.bbc.co.uk/programmes/b07v0hhm">The Waterside Ape</a>. </p>
<p>The hypothesis suggests that everything from walking upright to our lack of hair, from holding our breath to eating shellfish could be because an aquatic phase in our ancestry. Since the theory was first suggested more than 55 years ago, huge advances have been made in the study of human evolution and our story is much more interesting and complicated than suggested by the catch-all aquatic ape hypothesis.</p>
<p>In 1960, marine biologist Alister Hardy published an article in New Scientist, titled: <a href="http://www.riverapes.com/original/AAH/Hardy/Hardy1960.pdf">Was man more aquatic in the past?</a> He re-told the familiar tale of the evolution of land animals from ancient fish, and then considered the return of various groups of reptiles, birds and mammals to an aquatic existence: ichthyosaurs and plesiosaurs, crocodiles, sea-snakes, penguins, whales, dolphins and porpoises, manatees and dugongs, and seals – as well as polar bears, otters and water voles, who hunt in water. Then he suggested that many of the unique characteristics of humans and their ancestors, marking them out as different from the other apes, could be explained as adaptations to spending time in water.</p>
<p>Hardy put forward all sorts of features which could be explained as “aquatic adaptations”: our swimming ability – and our enjoyment of it; loss of body hair, as well as an arrangement of body hair that he supposed may have reduced resistance in the water; curvy bodies; and the layer of fat under our skin. He even suggested that our ability to walk upright may have developed through wading, with the water helping to support body weight. </p>
<p>For Hardy, this aquatic phase would have occupied the gap in the fossil record that then existed – between around 4m and 7m years ago. He sensibly concluded his paper saying that this was all only speculation – a “hypothesis to be discussed and tested against further lines of evidence”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138062/original/image-20160916-6311-akf9m1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A modern day aquatic ape. But there’s no trace of true ‘aquatic apes’ in our ancestry.</span>
<span class="attribution"><span class="source">dotshock/Shutterstock</span></span>
</figcaption>
</figure>
<p>In the 50-odd years since the presentation of this hypothesis, it has enjoyed a certain fame – or perhaps notoriety. The writer Elaine Morgan championed it in her book <a href="http://souvenirpress.co.uk/product/aquatic-ape-hypothesis/">The Aquatic Ape</a>, and developed the hypothesis further, marshalling a seemingly impressive range of characteristics to support it, including breath control and diet. It seems such a tantalising and romantic idea – but a closer look at the evidence reveals it to be little more than that.</p>
<h2>Pouring cold water on it</h2>
<p>All the suggested anatomical and physiological adaptations can be explained by other hypotheses, which fit much better with <a href="https://www.amazon.co.uk/dp/B00JIV9R3I/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1">what we actually know</a> about the ecology of ancient hominins. Hairlessness, for instance, is only a feature of fully aquatic mammals such as whales and dolphins. Semi-aquatic mammals such as otters and water voles are extremely furry. Sexual selection and adaptations to heat loss better explain our pattern of body hair. Sexual selection may also explain our body fat distribution, which differs between the sexes. Voluntary breath control is more likely to be related to speech than to diving. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138064/original/image-20160916-6340-1afo308.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Otters evolved from land animals but never lost their fur.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/slobirdr/15800171602/">Gregory </a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The diet of many of our ancestors certainly included marine resources – where people lived on the shores of lakes or the sea. But this was a relatively late development in human evolution, and humans can also survive and thrive on food obtained entirely on land. Compared with other animals, we are not actually that good at swimming, and our skin leaks as well, letting in water so that our fingers become prune-like after a long bath. </p>
<p>What about walking on two legs? That’s something all apes do a bit of – while wading in water, certainly, but also while reaching for fruit, performing aggressive displays or simply moving around in trees. If we evolved from ancestors who already stood up in trees, we don’t need an extraordinary explanation for why we ended up standing on the ground rather than <a href="http://onlinelibrary.wiley.com/doi/10.1111/jzo.12112/abstract">running around on all fours</a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/138057/original/image-20160916-6323-12629mz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hands up if you can stand on dry land.</span>
<span class="attribution"><span class="source">Sergey Uryadnikov / shutterstock</span></span>
</figcaption>
</figure>
<p>Since Hardy and Morgan’s hypothesis was advanced, many of the gaps in the human fossil record have been filled, with <a href="http://rstb.royalsocietypublishing.org/content/371/1698/20150244">at least 13 new species</a> found since 1987. We have also made great strides in reconstructing <a href="http://dx.doi.org/10.1016/j.quascirev.2014.06.012">the environment in which our ancestors lived</a>. And we know that species as far as part in time as <em>Sahelanthropus tchadensis</em> 7m years ago and <em>Homo erectus</em> 2m years ago all lived in <a href="http://dx.doi.org/10.1016/B978-0-08-095975-7.01213-4">forested or open woodland environments</a>. While some of these woods included wetland, this was just part of the mosaic of habitats that our ancestors learned to survive in, and there is absolutely no trace of a hominin ancestor as aquatic as that described by Hardy and Morgan. </p>
<p>We also have evidence our ancestors had to survive <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076750">periods of extremely dry climate</a> with little or no aquatic resources. Coping with these highly variable, patchwork environments required <a href="https://www.researchgate.net/publication/258810494_Hominin_evolution_in_settings_of_strong_environmental_variability">behavioural flexibility and co-operation</a>, and our large brains and ultra-social nature likely emerged as a result. This flexibility ultimately led to the invention of culture and technology.</p>
<p>Recent proponents of the aquatic ape hypothesis have pointed to much later watery adaptations, including early archaeological sites where humans have been shown to be exploiting coastal resources. But these don’t have much to say about the origins of bipedalism, more than 6m years before – they just demonstrate the behavioural flexibility of later hominins.</p>
<h2>Too extravagant and too simple</h2>
<p>The original idea, and certainly Elaine Morgan’s elaboration of it, became an <a href="http://www.sciencedirect.com/science/article/pii/S0047248497901469">umbrella hypothesis</a> or a “Theory of Everything”; both far too extravagant and too simple an explanation. It attempts to provide a single rationale for a huge range of adaptations - which we know arose at different times in the course of human evolution. Traits such as <a href="https://www.scribd.com/document/216676020/Challenges-to-Human-Uniqueness-Bipedalism-Birth-and-Brains">habitual bipedalism</a>, <a href="http://dx.doi.org/10.1098/rstb.2014.0064">big brains and language</a> didn’t all appear at once – instead, their emergence is spread over millions of years. It’s nonsense to lump them all together as if they require a single explanation.</p>
<p>Despite the evidence stacked up against the theory, it is <a href="http://onlinelibrary.wiley.com/doi/10.1002/evan.21405/abstract">strangely tenacious</a>. It has become very elastic, and its <a href="http://www.ted.com/talks/elaine_morgan_says_we_evolved_from_aquatic_apes?language=en">proponents</a> will seize hold of any mentions of water, fish or shellfish in human evolution, and any archaeological sites found near coasts, rivers and lakes as supporting evidence. But we must always build our hypotheses on, and test them against, the hard evidence: the fossils, comparative anatomy and physiology, and genetics. In that test, the aquatic ape has failed – again and again. </p>
<p>It is a great shame the BBC recently indulged this implausible theory as it distracts from the emerging story of human evolution that is both more complex and more interesting. Because at the end of the day science is about evidence, not wishful thinking.</p>
<hr>
<p><em>Scientist supporters of the waterside ape hypothesis have responded to this article <a href="http://aquatic-human-ancestor.org/evidence/waterside-ape-bbc-r4-response-to-critics.html">here</a>.</em></p><img src="https://counter.theconversation.com/content/65570/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alice Roberts has made several programmes about human evolution for the BBC.</span></em></p><p class="fine-print"><em><span>Mark Maslin is a Professor at University College London, a Royal Society Industrial Fellow, Founding Director of Rezatec Ltd, Director of The London NERC Doctoral Training Partnership and a member of Cheltenham Science Festival Advisory Committee. He is an unpaid member of the Sopra-Steria CSR Board. He has received funding in the past from the NERC, EPSRC, ESRC, Royal Society, DIFD, DECC, BIS, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Leverhulme Trust, WWF, JLT Re, Channel 4, RICS, British Council, and CAFOD.</span></em></p>
David Attenborough’s latest BBC documentary indulges wishful thinking over evidence.
Alice Roberts, Professor of Public Engagement in Science, University of Birmingham
Mark Maslin, Professor of Palaeoclimatology, UCL
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/63627
2016-08-10T22:20:49Z
2016-08-10T22:20:49Z
What can a 1.7-million-year-old hominid fossil teach us about cancer?
<figure><img src="https://images.theconversation.com/files/133391/original/image-20160808-18010-8sjngf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Volume rendered image of the external morphology of the foot bone shows the extent of expansion of the primary bone cancer beyond the surface of the bone.</span> <span class="attribution"><a class="source" href="http://www.eurekalert.org/multimedia/pub/120746.php?from=334527">Patrick Randolph-Quinney (UCLAN)</a></span></figcaption></figure><p>In late July, <a href="http://doi.org/10.17159/sajs.2016/20150471">an international team of researchers</a> announced that they had identified evidence of cancer in the fossilized remains of a biological relative of human beings who lived about 1.7 million years ago.</p>
<p>It is rare to find fossils from the hominid family tree. Finding one with such well-preserved evidence of a tumor is rarer still.</p>
<p>It seems that cancer has been with us for quite some time, and this finding highlights one of the most fascinating questions about it: why cancer exists in the first place.</p>
<p>Cancer is a deadly disease and would have been particularly lethal before the recent development of effective treatments. So why didn’t it – or our susceptibility to it – die out long ago? </p>
<p>To put the question somewhat differently, why should organisms, including human beings, carry within our DNA the instruments of our own destruction – tumor suppressor genes and oncogenes just waiting for environmental insults before they kill their carriers? Shouldn’t organisms with such genes be selected against in the evolutionary competition to survive and reproduce?</p>
<h2>An ancient osteosarcoma</h2>
<p>Before addressing that question, let’s go back to the 1.7-million-year-old tumor.</p>
<p>The researchers found the cancer in a metatarsal, one of the long bones of the foot found just behind the toes. The researchers examined the specimen with high-resolution x-rays, revealing the lesion in greater detail and producing a three-dimensional image, which revealed an “irregular spongy woven bone texture with a cauliflower-like external appearance.” In other words, the cells of the tumor had grown in a disorganized fashion and were ballooning out from the shaft of the bone – features of a malignancy. They concluded that it was a bone cancer, probably an osteosarcoma. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133393/original/image-20160808-18010-hcwokh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A different view of the tumor in the metatarsal bone.</span>
<span class="attribution"><a class="source" href="http://www.eurekalert.org/multimedia/pub/120747.php?from=334527">Edward Odes/University of the Witwatersrand</a></span>
</figcaption>
</figure>
<p>As a radiologist working in a children’s hospital, I regularly see x-ray, CT and MRI scans of patients with osteosarcomas. They account for a fraction of all primary bone cancers, and are most often diagnosed in adolescence and young adulthood. One unusual feature of the South African report is the location of the tumor – the leg and arm are much more common sites than the foot.</p>
<p>Osteosarcomas arise from abnormal bone-producing cells. In fact, the name osteosarcoma comes from Greek roots meaning “bone” and “fleshy growth.” </p>
<p>Osteosarcomas aren’t just found in humans. They represent the most <a href="http://wearethecure.org/learn-more-about-canince-cancer/canine-cancer-library/osteosarcoma/">common bone malignancy found in dogs</a> <a href="http://www.vcahospitals.com/main/pet-health-information/article/animal-health/osteosarcoma-in-cats/316">and cats</a>. In fact, osteosarcomas are <a href="http://dx.doi.org/10.1093/ilar/ilu009">more common in dogs than people</a>, <a href="http://www.vet.upenn.edu/docs/default-source/ryan/oncology-handouts/bone-tumors-in-dogs_ek-ks.pdf?sfvrsn=4">especially in large species</a> such as <a href="http://rrcus.org/rhodesianridgebackhealth/Documents-PDFs/Osteosarcoma.pdf">greyhounds and great danes</a>. </p>
<p>Cancer has been around for much longer than 1.7 million years. In Indianapolis, our <a href="https://www.childrensmuseum.org/blog/meet-the-gorgosaur-v2">Children’s Museum</a> features the fossilized skull of a Gorgosaurus, a relative of Tyrannosaurus rex which lived during the Cretaceous period about 70 million years ago. It shows clear evidence of a golf-ball-sized mass inside the skull cavity. </p>
<h2>Cancer isn’t a single disease</h2>
<p>One challenge in attempting to understand the causes of cancer is the fact that cancer is not a single disease. </p>
<p>There are many different types of cancer, which can be categorized according to the organ in which they originate – lung cancer, colon cancer, breast cancer and so on. Better yet, they can be categorized by the type of tissue they represent. For example, carcinomas arise from epithelial or lining cells, sarcomas from connective cells, and leukemias from blood-forming cells.</p>
<p>What we call cancer really represents a family of disorders, all of which can be lumped together because of a common feature – disrupted regulation of cell growth.</p>
<p>For example, genes that normally suppress cell growth may be damaged, leading to uncontrolled proliferation. An indication that all cancers are not the same is the fact that they have very different prognoses and treatments.</p>
<p>Today evidence suggests that many cancers can be traced to environmental exposures, such as tobacco, dietary carcinogens, infections, and air and water pollution. It seems unlikely that tobacco or air pollution could have caused cancer millions of years ago, but it’s possible that some dietary and infectious agents may have been more common in the remote past. </p>
<h2>Chromosomes and oxygen</h2>
<p>One of the first explanations for how cancer could result from chromosomal damage was provided by a medical school professor of mine at the University of Chicago, <a href="https://news.uchicago.edu/article/2013/12/17/janet-rowley-cancer-genetics-pioneer-1925-2013">Janet Rowley, M.D</a>. In the 1970s, Dr. Rowley showed that in many patients with a type of leukemia, CML, <a href="http://www.nature.com/nature/journal/v243/n5405/abs/243290a0.html">portions of chromosomes 9 and 22 had been exchanged</a>, proving that changes in DNA could lead to cancer.</p>
<p>Part of the blame for cancer may be placed on a rather unexpected culprit, a molecule without which human life would be utterly impossible – oxygen. Oxygen is necessary for our cells to convert food to energy. This is one of the reasons that the human body is equipped with over 60,000 miles of blood vessels, which enable red blood cells to carry oxygen to each of our 75 trillion cells.</p>
<p>But oxygen is not an entirely benign molecule. In fact, it is highly reactive and even toxic in high concentrations. And early in Earth’s history, oxygen levels began to rise dramatically, as plants capable of photosynthesis – a process that produces oxygen – proliferated. More oxygen permitted the development of multicellular organisms capable of transporting oxygen to all of their cells. </p>
<p>Oxygen becomes problematic when <a href="http://dx.doi.org/10.3109/10715761003667554">superreactive forms</a> of it are formed. For example, when ionizing radiation strikes a cell, it can form superoxides that react avidly with nearby molecules. When one of the nearby molecules is DNA, damage to genes occurs, producing mutations that can be carried from one generation of cells to another. In some cases, a transformation to cancer may result. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133385/original/image-20160808-18053-slt6xy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Human malignant osteosarcoma (bone cancer) cells from a leg mass.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Osteosarcoma_(bone_cancer).jpg">National Cancer Institute via Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>Will cancer always be with us?</h2>
<p>Another reason that cancer has persisted is the fact that it tends to be a disease of older organisms. Only <a href="http://www.cancer.org/cancer/cancerinchildren/detailedguide/cancer-in-children-key-statistics">1 percent of the cancers</a> diagnosed each year in the U.S. occur in children. So for most of our biological history, when life expectancy was shorter, hominids reproduced and died of other causes long before cancer had a chance to develop.</p>
<p>In advanced countries today, mortality rates due to other diseases, such as infections, <a href="http://dx.doi.org/10.1001/jama.2015.12319">heart disease and stroke</a>, have fallen so far that many more people are living to advanced ages, by which point the series of mutations necessary to induce cancer have had sufficient time to occur. In effect, rising cancer rates are in part a sign of general good health and longevity.</p>
<p>Can we make cancer disappear? The fundamental problem with cancer cells is that they do not know when to stop growing and die, and as a result, they keep proliferating in an uncontrolled fashion. While this is highly injurious to the organism, the existence of genes that promote cell growth is obviously crucial for organisms to grow and survive in the first place.</p>
<p>Consider an automobile. Just two weeks ago, the brakes on my car failed, a dangerous situation. We might wish that cars were built so that the brakes could never fail, but the only way to eliminate the possibility of brake failure would be to do away with the brake system altogether, a far more hazardous proposition.</p>
<p>The same thing can be said about cancer. We might wish that we were built without genes that can contribute to the development of cancer, but normal growth and development – and yes, even death – might not be possible without them. When it comes to life, we must take the bad as well as the good, though this is not to say that we cannot make strides in preventing and curing cancer.</p>
<p>The finding of cancer in the bone of a 1.7-million-year-old human relative isn’t just a biological oddity – it is a reminder of what it means to be both alive and human. Life is fraught with hazards. Thriving biologically (and biographically) does not mean eliminating all risks but managing the ones we can, both to reduce harm and promote a full life.</p><img src="https://counter.theconversation.com/content/63627/count.gif" alt="The Conversation" width="1" height="1" />
Cancer is a deadly disease and would have been particularly lethal before the recent development of effective treatments. So why didn’t it – or our susceptibility to it – die out long ago?
Richard Gunderman, Chancellor's Professor of Medicine, Liberal Arts, and Philanthropy, Indiana University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/61572
2016-06-28T03:02:29Z
2016-06-28T03:02:29Z
Ancient Deep Skull still holds big surprises 60 years after it was unearthed
<figure><img src="https://images.theconversation.com/files/128438/original/image-20160628-28373-1mi9luh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The 37,000 year old Deep Skull from Niah Cave in Borneo is the oldest modern human skeleton found in island Southeast Asia.</span> <span class="attribution"><span class="source">Darren Curnoe</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Thousands of years ago, the ancestors of modern humans left Africa to embark on a journey that would eventually take them across the globe. Yet we still know precious little about the momentous journeys they undertook.</p>
<p>Now, new research by my team and me significantly recasts how we think about the early peopling of Southeast Asia and the relationship the earliest humans had to the indigenous people of the region today.</p>
<p>Southeast Asia spans some 4.5 million square kilometres and is today home to roughly one tenth of the world’s population. Yet, we still know very little about their origins beyond a few thousand years ago.</p>
<p>This region’s ancient past has much wider importance; the early peopling of New Guinea, Australia and ultimately, the Pacific, was launched from Southeast Asia. </p>
<p>Yet archaeologists have found only six sets of remains dating beyond 25,000 years ago from across the region. This is the closest we’ve come to having skeletons of the first modern humans themselves. </p>
<p>They were scattered far and wide: found at Wadjak in Indonesia, Niah Cave in Malaysian Borneo, Callao Cave and Tabon Cave in the Philippines, Tam Pa Ling in Laos and Moh Khiew Cave in Thailand. </p>
<iframe src="https://www.google.com/maps/d/embed?mid=1CaTdujNNwGAAxbNkk2bNSso150I&hl=en" width="100%" height="480"></iframe>
<p>Strikingly, the Wadjak remains were found in 1888-90, and the Tam Pa Ling bones only uncovered in 2010. This gives a sense of just how rare and valuable early human remains are and how infrequently such discoveries are made.</p>
<h2>First glimpses of the Deep Skull</h2>
<p>It brings me to the famous Deep Skull, which was found by Tom Harrisson and his team almost 60 years ago in Niah Cave in Sarawak. This fossil was the focus research we published today in the journal <a href="http://journal.frontiersin.org/article/10.3389/fevo.2016.00075/full">Frontiers in Ecology and Evolution</a>.</p>
<p>Deep Skull was recovered from the evocatively named “Hell Trench” of the great West Mouth of Niah Cave in Sarawak; the name was given to the trench due to the incredible heat endured by the excavators in the afternoon sun.</p>
<p>Niah Cave itself is a remarkable system of caves set in ancient limestone in northern Borneo that has supported the trade in bird nests for centuries. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128151/original/image-20160626-28382-7j0yso.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The remarkable West Mouth of Niah Cave. The excavation area of the Harrisson’s can be seen in the far distance on the right side.</span>
<span class="attribution"><span class="source">Darren Curnoe</span></span>
</figcaption>
</figure>
<p>The West Mouth is an incredible 244 metres wide, 61 metres high, and covers an area of around 105,000 square metres. It takes my breath away every time I visit.</p>
<p>Its scientific potential was first highlighted by <a href="http://www.britannica.com/biography/Alfred-Russel-Wallace">Alfred Wallace</a>, co-discoverer of natural selection, and frequent resident of Sarawak, who brought it to the attention of Thomas Henry Huxley way back in 1864.</p>
<p>But it wasn’t until the 1950s that Tom Harrisson, and eventually his partner Barbara Harrisson, began meticulous excavations at Niah Cave, lasting until the 1970s.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128172/original/image-20160626-28362-1qh3xyt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The main excavation area of the Harrison’s in the West Mouth of Niah Cave. The ‘Hell Trench’ is located beneath the roofed area.</span>
<span class="attribution"><span class="source">Darren Curnoe</span></span>
</figcaption>
</figure>
<p>In 1958, at the level of 101-110 inches below the surface, the Deep Skull was found in the Hell Trench. Soon after, radiocarbon dating on charcoal gave it an age of around 40,000 years old. </p>
<p>In the early 2000s, Graham Barker from Cambridge University <a href="http://www.sciencedirect.com/science/article/pii/S0047248406001801">reanalysed the site and its age</a>, and through a combination of the dating of charcoal and the Deep Skull itself, they showed the skeleton to be 37,000 years old.</p>
<p>Don Brothwell of Cambridge University studied the Deep Skull in 1960 and concluded it belonged to an adolescent male and might represent a population of early modern humans closely related, or even ancestral, to Indigenous Australians, particularly Tasmanians.</p>
<p>His ideas were contentious even at the time, but have been highly influential ever since.</p>
<h2>A fresh look at old bones</h2>
<p>We wanted to see whether Brothwell’s ideas might be correct after so long, especially given that so few scientists have taken the trouble of going to Borneo to see the Deep Skull for themselves. Our work is the most comprehensive description and analysis done to date. </p>
<p>And in contrast to Brothwell, we found that the remains are most probably from a middle-aged woman rather than an adolescent male.</p>
<p>We also compared Deep Skull with other fossils and recent human populations from around the region and found very few similarities to Indigenous Australians.</p>
<p>Instead, it seems clear that Deep Skull most closely resembles the indigenous people of Borneo today, with their delicate features and small body size.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=732&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=732&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=732&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=920&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=920&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128155/original/image-20160626-28388-1agfkf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=920&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deep Skull (top) compared with an Indigenous Iban cranium collected from a long-house in Sarawak, and with early modern human crania from China (Liujiang) and the Willandra Lakes in Australia (WLH3 and WLH 50).</span>
<span class="attribution"><span class="source">Darren Curnoe</span></span>
</figcaption>
</figure>
<p>The remains have also been a key player in the so-called <a href="https://en.wikipedia.org/wiki/Two_layer_hypothesis">“two-layer” hypothesis</a> for the peopling of Southeast Asia.</p>
<p>This old idea proposes that the very earliest humans in the region were related to Indigenous Australians, but were later replaced by farmers from southern China.</p>
<p>If we’re right that Deep Skull is related to the indigenous people of Borneo, then these people, who are distinct from Australians, have inhabited the region for at least 37,000 years and not 3,000 years as the two-layer hypothesis would imply.</p>
<p>Our work finds support also in genetic studies of recent human populations across Southeast Asia, and together, they pose a serious challenge to the two-layer scenario for Borneo and islands further to the north.</p>
<p>It’s exciting to think that after almost 60 years, fossils such as Deep Skull still have a lot to offer in helping us to reconstruct the early prehistory of Southeast Asia, and help us answer some of the deep mysteries of how early human populations moved across the globe.</p><img src="https://counter.theconversation.com/content/61572/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darren Curnoe receives funding from the Australian Research Council. </span></em></p>
Another look at a skull unearthed in Malaysian Borneo 60 years ago can shed light on the mystery of how early humans moved throughout Southeast Asia thousands of years ago.
Darren Curnoe, ARC Future Fellow and Director of the Palaeontology, Geobiology and Earth Archives Research Centre (PANGEA), UNSW Sydney
Licensed as Creative Commons – attribution, no derivatives.