tag:theconversation.com,2011:/us/topics/dinaledi-20659/articles
Dinaledi – The Conversation
2021-11-04T15:51:34Z
tag:theconversation.com,2011:article/171153
2021-11-04T15:51:34Z
2021-11-04T15:51:34Z
I was part of the team that found the Homo naledi child’s skull: how we did it
<figure><img src="https://images.theconversation.com/files/430224/original/file-20211104-27-h990j7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A reconstruction of the skull of Leti, the first _Homo naledi_ child whose remains were found in the Rising Star cave in Johannesburg</span> <span class="attribution"><span class="source">© Wits University</span></span></figcaption></figure><p><em>In 2015 a new member was introduced to the family tree of humans. Fossil hominins from the Rising Star cave system outside Johannesburg, South Africa, <a href="https://elifesciences.org/articles/09560">were found</a> to belong to a previously unidentified hominin species, which was then named Homo naledi. Now an international team of researchers, led by Professor Lee Berger, a palaeoanthropologist from South Africa’s University of the Witwatersrand, has revealed the first partial skull of a Homo naledi child, also from the Rising Star cave. In two <a href="https://paleoanthropology.org/ojs/index.php/paleo/article/view/64">journal</a> <a href="https://paleoanthropology.org/ojs/index.php/paleo/article/view/68">articles</a> researchers estimate that the child died almost 250,000 years ago, at the age between four and six years old. Given that this is the first partial skull of a child of Homo naledi ever recovered, it can offer important insights into the species’ different life stages.</em> </p>
<p><em>The child has been named “Leti” after the Setswana word “letimela”, meaning “the lost one”. The Conversation Africa’s Natasha Joseph spoke with Dr Marina Elliott, lead author of <a href="https://paleoanthropology.org/ojs/index.php/paleo/article/view/68">the paper</a> describing how and where the skull was discovered, about the painstaking and physically demanding work involved in bringing Leti to the surface.</em></p>
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<h2>Seven years ago, you became an “Underground Astronaut”. What does that entail?</h2>
<p>The “Underground Astronauts” is a nickname for the group of six scientists and excavators from the original Rising Star expedition. We got the name, I think, because working in the Dinaledi Chamber was a little bit like a space mission: a journey through the darkness, working remotely with only video and voice connection to a “command centre” on the surface, and matching overalls and helmets. </p>
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<figcaption><span class="caption">The original “Underground Astronauts” at work.</span></figcaption>
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<p>All of us ended up on the project after responding to a Facebook ad that Lee Berger posted, asking for excavators who were able (and willing!) to dash off to South Africa on a month’s notice to work in a cave system, in cramped quarters, in a small team to excavate some fossil material. We didn’t really know at the time what we would end up with, or how important it would be. </p>
<h2>Can you describe the Rising Star system?</h2>
<p>The Rising Star cave system is located in the <a href="https://www.maropeng.co.za/content/page/introduction-to-your-visit-to-the-cradle-of-humankind-world-heritage-site">Cradle of Humankind</a>, just outside Johannesburg. It’s a large area that has many caves, cave systems and underground rivers, and it has been famous for important fossil finds since the 1920s. The Rising Star cave system isn’t just one big cave: it’s a complex network of tunnels, passages, squeezes and chambers, some of which interconnect. It’s more of a maze or labyrinth than a single “cave”. </p>
<p>The Dinaledi Chamber is just one in a sub-system of chambers and passages within the larger Rising Star system. The new fossil area, U.W.110, where the child’s remains were recovered, is in a very small passage in the Dinaledi Chamber, about 12 metres away from where we originally excavated adult <em>Homo naledi</em> fossils. </p>
<h2>Do you remember the first time you went into Rising Star?</h2>
<p>Shortly after we arrived on site, some of the cavers took us into Rising Star to give us a sense of the route and the spaces. It was very interesting at first, walking along the passages with the musty smells of the cave all around us. But we quickly had to crawl through a squeeze, then climbed up a knife-ridge of rock (called the Dragon’s Back) using harnesses, and arrived at an area called the top of the Chute. </p>
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<img alt="" src="https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430226/original/file-20211104-13-wlu5m0.jpeg?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">The author exploring the Rising Star system.</span>
<span class="attribution"><span class="source">© Wits University</span></span>
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<p>We didn’t go down the Chute that day, but knew we would be heading into it the next day to begin the excavations. I remember peering into it, knowing that it was a 12 metre long vertical fissure in the rock, but not being able to see the route for the narrowness of the gap and the spikes of rock all the way down. I remember thinking perhaps I’d been too hasty in signing up for such a project! </p>
<p>But the excitement of the fossils overcame that feeling and the next day Becca Peixotto, Hannah Morris and I were the first excavators to go in. The chute took a long time to negotiate, but then we dropped into a small chamber that led into the Dinaledi Chamber proper. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/more-secrets-of-human-ancestry-emerge-from-south-african-caves-77352">More secrets of human ancestry emerge from South African caves</a>
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</em>
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<p>I was the first of the group to step into the Dinaledi Chamber and it was pretty amazing. With only my headlamp for light, I had to sweep back and forth to see what was there; immediately, I could see that there were fragments of bone all over the floor. Even without knowing there was so much more below the surface, it was exhilarating to stand there, thinking about how we were going to get all the material out, how it got there and what it all meant. </p>
<h2>How did you find the skull, and then bring it out?</h2>
<p>The discovery of the U.W.110 location came out of explorations that we conducted in 2017, trying to understand more about the physical spaces in the Dinaledi sub-system; how they might have formed and how the fossil material might have arrived in the area. The exploration team was tasked with systematically exploring and mapping as many of the interconnected passages as possible, for as far as they could physically work their way in. </p>
<p>The U.W.110 location is just over 12 metres from the Dinaledi Chamber excavation area. To get there from the Dinaledi Chamber, you have to go through a short squeeze and into another small chamber called Chaos. From there, you have to climb over some fallen boulders and drop into a narrow crawl space. The Leti material was recovered from the surface of a tight, narrow passage a bit further in, that can only be accessed with difficulty by one person at a time. </p>
<p>Becca Peixotto recovered the fragments, but had to do so bent around a corner and almost upside down. Even taking photos of the material in place was difficult because of the small, awkward spaces and Becca had to pass each piece through a little window of rock out to me. Before we removed anything, it was documented – photographs, drawings etc – and given a field number and label. We wrapped each fragment in bubble wrap, placed it in a plastic container and then put it in a dry bag to be carried up to the surface. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/ancient-dna-increases-the-genetic-time-depth-of-modern-humans-84716">Ancient DNA increases the genetic time depth of modern humans</a>
</strong>
</em>
</p>
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<h2>Do you think the Rising Star system holds more secrets?</h2>
<p>I think there is likely a lot more to find in the cave system. There may be other locations of <em>H. naledi</em> material, but there is also a lot of work that still needs to be done in the Dinaledi and Lesedi Chambers (and elsewhere in the system) to understand the geology and context of the fossils, and so many questions remain to be answered.</p><img src="https://counter.theconversation.com/content/171153/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marina Elliott 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>
The fossil material was recovered from the surface of a tight, narrow passage that can only be accessed with difficulty by one person at a time.
Marina Elliott, Researcher, Physical and Biological Anthropology, Simon Fraser University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/77352
2017-05-09T09:21:02Z
2017-05-09T09:21:02Z
More secrets of human ancestry emerge from South African caves
<figure><img src="https://images.theconversation.com/files/168384/original/file-20170508-20740-sdijm5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">"Neo" skull of Homo naledi from the Lesedi Chamber.</span> <span class="attribution"><span class="source">John Hawks/Wits University</span></span></figcaption></figure><p><em>Africa’s richest fossil hominin site has revealed more of its treasure. It’s been a year and a half since scientists announced that a new hominin species, which they called Homo naledi, had been discovered in the Rising Star Cave outside Johannesburg.</em></p>
<p><em>Now they say they have <a href="https://elife.elifesciences.org/">established and published</a> the age of the original naledi fossils that garnered global headlines in 2015. Homo naledi lived sometime between 335 and 236 thousand years ago, making it relatively young.</em></p>
<p><em>They’ve also <a href="https://elife.elifesciences.org/">announced</a> the discovery of a second chamber in the Rising Star cave system, which contained additional Homo naledi specimens. These include a child and the partial skeleton of an adult male with a well-preserved skull. They have named the skeleton “Neo” – a Sesotho word meaning “a gift”.</em></p>
<p><em>The Conversation Africa’s Science Editor Natasha Joseph asked Professor John Hawks, a member of the team, to explain the story behind these finds.</em></p>
<p><strong>To an ordinary person, 236 000 years is a very long time ago. Why does the team suggest that in fact, <em>Homo naledi</em> is a “young” species?</strong></p>
<p>The course of <a href="http://humanorigins.si.edu/education/introduction-human-evolution">human evolution</a> has taken the last seven million years since our ancestors diverged from those of chimpanzees and bonobos. The first two-thirds of that long history, called <em><a href="http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensis">australopiths</a></em>, were apelike creatures who developed the trick of walking upright on two legs. </p>
<p>Around two million years ago some varieties of hominins took the first real steps in a human direction. They’re the earliest clear members of our genus, <em>Homo</em>, and belong to species like <em>Homo habilis</em>, <em>Homo erectus</em> and <em>Homo rudolfensis.</em></p>
<p><em>Homo naledi</em> looks in many ways like these first members of <em>Homo</em>. It’s even more primitive than these species in many ways, and has a smaller brain than any of them. People outside our team who have studied the fossils mostly thought they should be around the same age. A few had the radical idea that <em>H. naledi</em> might have lived more recently, maybe around <a href="https://www.sciencenews.org/article/new-dating-suggests-younger-age-homo-naledi">900,000 years ago</a>. </p>
<p>Nobody thought that these fossils could actually have come from the same recent time interval when modern humans were evolving, a mere 236 to 335 thousand years ago. </p>
<p><strong>How do you figure out a fossil’s age?</strong></p>
<p>We applied six different methods. The most valuable of these were <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/molecule/esr.html">electron spin resonance</a> (ESR) dating, and <a href="http://www.geo.arizona.edu/Antevs/ecol438/uthdating.html">uranium-thorium</a> (U-Th) dating. ESR relies on the fact that teeth contain tiny crystals, and the electron energy in these crystals is affected by natural radiation in the ground over long periods of time after fossils are buried. </p>
<p>U-Th relies on the fact that water drips into caves and forms layers of calcite, which contain traces of uranium. The radioactive fraction of uranium decays into thorium slowly over time. So the proportion of thorium compared to uranium gives an estimate of the time since the calcite layers formed. One of these calcite deposits, called a flowstone, formed above the <em>H. naledi</em> fossils in the Dinaledi Chamber. That flowstone helps to establish the minimum age: the fossils must be older than the flowstone above them. </p>
<p>For these two methods, our team engaged two separate labs and asked them to process and analyse samples without talking to each other. Their processes produced the same results. This gives us great confidence that the results are reliable. </p>
<p><strong>What does the discovery of <em>Homo naledi’s</em> age mean for our understanding of human history and evolution?</strong></p>
<p>For at least the past 100 years, anthropologists have assumed that most of the evolution of <em>Homo</em> was a story of progress: brains got bigger over time, technology became more sophisticated and teeth got smaller as people relied more upon cleverness to get better food and prepare it by cooking. </p>
<p>We thought that once culture really got started, our evolution was driven by a feedback loop – better food allowed bigger brains, more clever adaptations, more sophisticated communication. That enabled better technology, which yielded more food, and so on like a snowball rolling downhill.</p>
<p>No other hominin species could compete with this human juggernaut. You would never see more than one form of human in a single part of the world, because the competition would be too intense. Other forms, like Neanderthals, existed within regions of the world apart from the mainstream leading to modern humans in Africa. But even they were basically human with large brains. </p>
<p>That thinking was wrong. </p>
<p>Africa south of the equator is the core of human evolutionary history. That’s where today’s human populations were most genetically diverse, and that diversity is just a small part of what once existed there. Different lineages of archaic humans once lived in this region. Anthropologists have found a few fossil remnants of these archaic populations. They’ve tried to connect those remnants in a straight line. But the genetic evidence suggests that they were much more complex, with deep divisions that occasionally intertwined. </p>
<p><em>H. naledi</em> shows a lineage that existed for probably more than a million years, maybe two million years, from the time it branched from our family tree up to the last 300,000 years. During all this time, it lived in Africa with archaic lineages of humans, with the ancestors of modern humans, maybe with early modern humans themselves. It’s strikingly different from any of these other human forms, so primitive in many aspects. It represents a lost hominin community within which our species evolved. </p>
<p>I think we have to reexamine much of what we thought we knew about our shared evolutionary past in Africa. We know a lot of information from a few very tiny geographic areas. But the largest parts of the continent are unknown – they have no fossil record at all. </p>
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<a href="https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168540/original/file-20170509-10997-1xlntft.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>
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<span class="caption">Explorers Mathabela Tsikoane, Maropeng Ramalepa, Dirk van Rooyen, Steven Tucker (seated), and Rick Hunter (seated) inside the Rising Star cave system.</span>
<span class="attribution"><span class="source">Wits University/Marina Elliott</span></span>
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<p>We’re working to change that, and as our team and others make new discoveries, I’m pretty sure we are going to find more lineages that have been hidden to us. <em>H. naledi</em> will not be the last. </p>
<p><strong>The first <em>Homo naledi</em> discoveries were made in the Dinaledi Chamber. What led researchers to the second chamber? And what did you find there?</strong></p>
<p>The Dinaledi Chamber is one of the most significant fossil finds in history. After excavating only a very tiny part of this chamber, the sample of hominin specimens is already larger than any other single assemblage in Africa.</p>
<p>The explorers who first found these bones, Rick Hunter and Steven Tucker, saw what the team was doing when they were excavating in the chamber. The pair realised that they might have seen a similar occurrence in another part of the cave system. The Rising Star system has more than two kilometres of mapped passages underground. In another deep chamber, accessed again through very tight underground squeezes, there were hominin bones exposed on the surface. </p>
<p>Our team first began systematic survey of this chamber, which we named the Lesedi Chamber, in 2014. For two years Marina Elliott led excavations, joined at times by most of the team’s other experienced underground excavators. They were working in a situation where bones are jammed into a tight blind tunnel. Only one excavator can fit at a time, belly-down, feet sticking out. It is an incredibly challenging excavation circumstance. </p>
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<a href="https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168534/original/file-20170509-20725-1o5t500.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">Geologist Dr Hannah Hilbert-Wolf studying difficult to reach flowstones in a small side passage in the Dinaledi Chamber.</span>
<span class="attribution"><span class="source">Wits University</span></span>
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</figure>
<p>The most significant discovery is a partial skeleton of <em>H. naledi</em>, with parts of the arms, legs, a lot of the spine and many other pieces, as well as a beautifully complete skull and jaw. We named this skeleton “Neo”. We also recovered fragments of at least one other adult individual, and one child, although we suspect these bones may come from one or two more individuals. </p>
<p><strong>Is there a way for people to view these discoveries in person?</strong></p>
<p>On May 25 – <a href="http://www.sahistory.org.za/dated-event/organisation-african-unity-formed-and-africa-day-declared">Africa Day</a> – <a href="http://www.maropeng.co.za/">Maropeng</a> at the Cradle of Humankind World Heritage Site outside Johannesburg will open a new exhibit with the discoveries from the Lesedi Chamber and the Dinaledi Chamber together for the first time. </p>
<p>For people outside South Africa, the data from our three-dimensional scans of the new Lesedi fossils are available <a href="http://www.morphosource.org">online</a>.</p>
<p>Anyone can download the 3D models, and people with access to a 3D printer can print their own physical copies of the new fossils, as well as the fossils from the Dinaledi Chamber. It’s a great way for people to see the evidence for themselves.</p><img src="https://counter.theconversation.com/content/77352/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Hawks receives funding from National Geographic, the Fulbright Scholar Program and the National Research Foundation</span></em></p>
Evidence of Homo naledi’s age suggests we need to rethink our understanding of human history and evolution.
John Hawks, Paleoanthropologist, University of Wisconsin-Madison
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/62442
2016-07-27T07:56:04Z
2016-07-27T07:56:04Z
How tiny black spots shed light on part of the Homo naledi mystery
<figure><img src="https://images.theconversation.com/files/130564/original/image-20160714-23342-1btij8a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A replica of a Homo naledi skull.</span> <span class="attribution"><span class="source">GCIS/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Many questions have been thrown up by the discovery in South Africa of a previously unidentified human relative, Homo naledi. Perhaps the one that’s grabbed people’s attention the most is how Homo naledi’s bones ended up in the Dinaledi Chamber in the Rising Star cave complex in the Cradle of Humankind near Johannesburg.</p>
<p>The team which found and classified the remains has <a href="http://news.nationalgeographic.com/2015/09/150915-humans-death-burial-anthropology-Homo-naledi/">suggested</a> that the Homo naledi group deliberately deposited carcasses in complete darkness at the very back of the cave system. According to this claim, Homo naledi adopted a relatively “modern” or ritualistic form of behaviour even though the species had smaller brains than today’s humans.</p>
<p>To date, no opening has been found within the Dinaledi Chamber apart from the existing entrance. But might there have been an additional entrance at some time in the past? New research I have conducted and <a href="http://sajs.co.za/possibility-lichen-growth-bones-homo-naledi-were-they-exposed-light/j-francis-thackeray">published in the South African Journal of Science</a> centred on mysterious black spots found on Homo naledi bones from the cave. My findings suggest that the answer to this question may have been “yes” – there very well may have been an entrance.</p>
<p>I strongly believe that there was possibly a temporary entrance into the chamber, in addition to the one used by explorers today. This temporary entrance may been covered up by a rock fall that also trapped the individuals whose bones were found some time later. </p>
<p>Why do I believe that in fact there was this additional opening to the cave? Because those mysterious black spots are manganese dioxide and were probably deposited on the bones by lichen. And lichen need light to grow – so there must have been some light penetrating into the Dinaledi chamber. My scenario is that the Homo naledi family group was trapped in the Dinaledi Chamber after a rockfall – but that there was still, for a time, enough light to penetrate the chamber. This allowed lichen to grow on many of the bones of Homo naledi. </p>
<p>Then, with subsequent rockfalls in a phreatic maze, the Dinaledi Chamber was sealed except for the difficult route whereby explorers can enter the cave at the present time. </p>
<h2>Evidence from elsewhere</h2>
<p>The team which discovered the remains <a href="https://elifesciences.org/content/4/e09561">noted</a> that “some bones and teeth are dotted with black iron-manganese oxy-hydroxide deposits and coatings”.</p>
<p>I examined the remains in question and found that the spots were analogous to the kind of associated with modern lichen which are “symbionts”, including fungi – that disperse in spots – and algae, which require at least some light to grow.</p>
<p>My colleagues and I have previously <a href="http://reference.sabinet.co.za/webx/access/electronic_journals/sajsci/sajsci_v101_n1_a4.pdf">examined</a> instances of lichen in the Cradle of Humankind area. Lichen can grow on certain substrates, including bone or rock, with a dotted or spotted distribution. The spotted distribution of lichen is sometimes associated with dotted distributions of manganese oxy-hydroxide on the same surfaces. </p>
<p>The source of the manganese in the Cradle of Humankind region would include dolomite and <a href="http://geology.com/rocks/chert.shtml">chert</a>. These are rock materials that date back two billion years ago, related to a shallow saline sea that existed at that time.</p>
<p>In the Cradle of Humankind lichen has proved to grow not only on chert, but also on dolomite. It can also grow on bone surfaces.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130933/original/image-20160718-2115-fb2pyb.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">The black markings on these Homo naledi bones are manganese dioxide.</span>
</figcaption>
</figure>
<p>Hominid cranial specimens from the nearby Sterkfontein caves have small dots or spots of manganese oxyhydroxide on surfaces of bone, even within the inner cranial wall of these skulls. It seems likely that these dots or spots of manganese oxyhydroxide may have been areas where lichens were able to grow – in a partially sunlit micro-environment – for a relatively short period of time. Then sand would have covered the crania, blocking out the light and halting the lichen’s ability to keep growing. </p>
<p>So what does such evidence in the Cradle of Humankind tell us about Homo naledi’s mysterious black spots?</p>
<h2>Secrets of the caves</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130570/original/image-20160714-23336-2vu1nx.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">The Sterkfontein Caves in the Cradle of Humankind.</span>
<span class="attribution"><span class="source">MaropengSA/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The circumstances in the Wonder Cave – which is within 10kms of the Rising Star cave complex – offer some important clues to what might have happened to create spots on the Homo naledi remains.</p>
<p>When one walks from the entrance of the cavern into the darkness of the dolomitic solution cavity, the following becomes obvious: </p>
<p>Where there is intense light and heat on dry exposed surfaces outside the cave, there is little or no lichen growth at all. But, in the moister and slightly darker regions of the cave, there is an area where light and moisture appear to be optimal for the present lichen colonists.</p>
<p>Then, in the darkness at the back of the cave where very little light penetrates, there’s a decrease in the mean size of lichens, until there is no lichen growth at all – although there may be some moisture because of water dripping through the phreatic maze of the dolomitic cave system.</p>
<p>All of this suggests that, for the Homo naledi bones in the Rising Star cave to have become spotted with manganese dioxide, they had to have some exposure to light. That could only have happened if light got into the cave. And this was only possible if there was some sort of entrance that has, in the distant past, been covered over. If correct, this would contradict the original team’s proposal that, in prehistory, the Dinaledi Chamber could only be accessed by means of very narrow and circuitous passages, in complete darkness.</p>
<h2>Time to reassess?</h2>
<p>Based on my findings I believe that there was, at some time, a second entrance to the Dinaledi Chamber. This allowed at least some light to penetrate into the cave and to facilitate the growth of lichen and the subsequent deposition of manganese oxyhydroxide on the Homo naledi bones. </p>
<p>I’d further hypothesise that such an entrance, if it existed at all, was temporary. A rockfall in the maze cave system may have subsequently sealed the entrance at some stage in the dolomitic solution cavity. The darkness that settled over the cave would have terminated any lichen growth.</p>
<p>If there was more than one entrance into the Dinaledi Chamber, as suggested by my work and <a href="http://www.sciencedirect.com/science/article/pii/S0047248416000282">research</a> conducted by Dr Aurore Val, the “intentional depositional model” will need to be reassessed. It would seem unlikely that the Homo naledi group deliberately deposited or buried its dead.</p>
<p><em>Author’s note: I would like to acknowledge the support of the National Research Foundation, the Andrew Mellon Foundation, and the Centre of Excellence for the Palaeosciences.</em></p><img src="https://counter.theconversation.com/content/62442/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Francis Thackeray receives funding from the Mellon Foundation and the National Research Foundation</span></em></p>
New evidence suggests that Homo naledi didn’t deliberately deposit their dead in a hidden chamber.
Francis Thackeray, Phillip Tobias Chair in Palaeoanthropology, Evolutionary Studies Institute, University of the Witwatersrand
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/47840
2015-09-25T04:31:27Z
2015-09-25T04:31:27Z
Homo naledi: determining the age of fossils is not an exact science
<figure><img src="https://images.theconversation.com/files/95463/original/image-20150920-11714-78ktva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The skull of Homo naledi is built like those of early Homo species but its brain was just more than half the size of the average ancestor from 2 million years ago. </span> <span class="attribution"><span class="source">SUPPLIED</span></span></figcaption></figure><p>Age is nothing but a number when it comes to unravelling the relationships of species from our past. We do not know the actual geological age of the <a href="http://www.wits.ac.za/homonaledi/">Dinaledi fossils</a>, the single largest fossil hominin find in Africa, but the discovery of <a href="http://voices.nationalgeographic.com/blog/rising-star-expedition/">Homo naledi</a> still provides insight into how our ancestors evolved. </p>
<p>The Dinaledi fossil collection is one of the most complete ever discovered, representing nearly the entire anatomy of a previously unknown species. Yet our team made no statement or conclusion about the fossils’ geological age. I reviewed with Ed Yong some of the <a href="http://www.theatlantic.com/science/archive/2015/09/why-dont-we-know-the-age-of-the-new-human-ancestor-homo-naledi/405148/">reasons</a> why it is difficult to determine the age of the fossils. </p>
<p>The bottom line is that, for now, we have little idea how old the fossils may be. </p>
<p>Most fossil hominins are found in association with extinct animals, which give us at least a general indication of their age. Famous fossil discoveries from more than a century ago, such as the Spy Neanderthal skeletons from Belgium and the first Homo erectus from Java, were found together with long-extinct creatures that indicated they were of great antiquity. This won’t work for Homo naledi because we have found no other animals in association with the hominin bones. </p>
<p>Even today, with methods that rely upon radioactive isotopes to determine the absolute ages of rock layers, geologists often have to revise their initial ideas of the ages of fossils. </p>
<p>Across the last 45 years, the age of the famous KNM-ER 1470 skull of Homo rudolfensis, from Koobi Fora, Kenya, has swung upward and down by more than a half million years as geologists revised age estimates of the famous KBS Tuff. The age of the Sterkfontein Member 4 fossils has been notoriously difficult to determine. Different teams have produced very different ages for the famous Little Foot skeleton from the Silberberg Grotto of Sterkfontein, ranging over more than a million years. </p>
<p>In other words, it pays to be cautious about geology. </p>
<h2>But how old is it?</h2>
<p>Our lack of a geological age for the fossils caught some other experts by surprise. Carol Ward, of the University of Missouri, <a href="http://www.theatlantic.com/science/archive/2015/09/homo-naledi-rising-star-cave-hominin/404362/">commented</a> to The Atlantic:</p>
<blockquote>
<p>“Without dates, the fossils reveal almost nothing about hominin evolution, beyond supporting the growing realisation that there was much more species diversity than previously thought.”</p>
</blockquote>
<p>William Jungers, from Stony Brook University, said in The <a href="http://www.theguardian.com/science/2015/sep/10/new-species-of-ancient-human-discovered-claim-scientist">Guardian</a>. </p>
<blockquote>
<p>“If they are as old as two million years, then they might be early South African versions of Homo erectus, a species already known from that region. If much more recent, they could be a relic species that persisted in isolation. In other words, they are more curiosities than game-changers for now.”</p>
</blockquote>
<p>Whether it turns out to be 20 000 years or 2 million years old, Homo naledi is equally distinct from Homo erectus either way. The age of the fossils is simply not relevant to their relationships with other hominins. In the study of anatomy, we focus on the shared features of different species, not their age. </p>
<p>Indeed, so-called relic species can be among the most important indicators of biological relationships, survivors that carry anatomical features from deep time. The coelacanth is much more than a curiosity: its anatomy provides vital clues that helped scientists understand how early land creatures could evolve from lobe-finned fish ancestors.</p>
<h2>How our ancestors evolved</h2>
<p>No matter its geological age, Homo naledi may provide vital clues about the way our ancestors stepped along a humanlike evolutionary path. This is where the real mystery comes in.</p>
<p>When we look across the skeleton of Homo naledi, we see some puzzling combinations of features. Homo naledi has a foot nearly the same as our own, much more humanlike than any early hominin we’ve discovered so far. Yet its hip and thighbone seem more primitive.</p>
<p>Likewise, Homo naledi had a hand and wrist that were largely humanlike, suitable for manipulating objects and possibly making tools. Yet powerful thumbs, curved finger bones and a shoulder canted upward like an ape’s shoulder suggest that its arms were used for climbing much more than any human today.</p>
<p>The skull of Homo naledi is built like those of early Homo species, especially Homo erectus, but its brain was just more than half the size of the average Homo erectus. Meanwhile, Homo naledi had teeth that were smaller than average for any early Homo species, a trait we have usually linked to eating better, more calorie-rich foods like meat or starchy tubers.</p>
<p>It’s almost as if Homo naledi evolved from the outside in. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=400&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=400&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95560/original/image-20150921-31531-1530wz1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=400&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Homo naledi skull DH3 compared with an example of Homo erectus from East Africa.</span>
<span class="attribution"><span class="source">SUPPLIED</span></span>
</figcaption>
</figure>
<p>The traits in direct contact with its environment, used for walking, handling things, and eating, are the most humanlike. The core of Homo naledi’s body, its brain, ribcage and hips, were more like our very distant relatives, the australopiths.</p>
<p>These combinations make it hard to be sure exactly where Homo naledi fits on our family tree. If we trust the humanlike foot and hand, and the Homo erectus-like cranial form, then Homo naledi looks like it may be closer to us than Homo habilis, the famous handy man. </p>
<p>Whether it is closer or not, Homo naledi’s features show that the key changes leading to our genus may have had nothing to do with a large brain. Testing this will bring us closer to understanding the causes that made us human. </p>
<p><em>John <a href="http://johnhawks.net">Hawks</a> is a core scientist on the Rising Star Expedition team and co-author on the papers describing Homo naledi.</em></p><img src="https://counter.theconversation.com/content/47840/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Hawks 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>
Despite claims about its age, puzzling combinations of features from Homo naledi gives it an uncanny resemblance to human beings.
John Hawks, Paleoanthropologist, University of Wisconsin-Madison
Licensed as Creative Commons – attribution, no derivatives.