tag:theconversation.com,2011:/africa/topics/radiocarbon-dating-1839/articles
Radiocarbon dating – The Conversation
2023-10-05T19:16:35Z
tag:theconversation.com,2011:article/213714
2023-10-05T19:16:35Z
2023-10-05T19:16:35Z
Humans got to America 7,000 years earlier than thought, new research confirms
<figure><img src="https://images.theconversation.com/files/551046/original/file-20230928-19-398dat.jpg?ixlib=rb-1.1.0&rect=2%2C5%2C1726%2C806&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The footprints come from a group of people of different ages.</span> <span class="attribution"><span class="source">National Park Service</span></span></figcaption></figure><p>When and how humans first settled in the Americas is a subject of considerable controversy. In the 20th century, archaeologists believed that humans <a href="https://www.smithsonianmag.com/history/the-clovis-point-and-the-discovery-of-americas-first-culture-3825828/">reached the North American interior</a> no earlier than around 14,000 years ago. </p>
<p>But our new research found something different. Our latest <a href="http://www.science.org/doi/10.1126/science.adh5007">study</a> supports the view that people were in America about 23,000 years ago.</p>
<p>The 20th century experts thought the appearance of humans had coincided with the formation of an ice-free corridor between two immense ice sheets straddling what’s now Canada and the northern US. According to this idea, the corridor, caused by melting at the end of the last Ice Age, <a href="https://pubmed.ncbi.nlm.nih.gov/17838701/">allowed humans to trek from Alaska</a> into the heart of North America. </p>
<p>Gradually, this orthodoxy crumbled. In recent decades, dates for the earliest evidence of people have crept back from 14,000 years ago to 16,000 years ago. This is still consistent with humans only reaching the Americas as the last Ice Age was ending.</p>
<p>In September 2021, we <a href="https://www.science.org/doi/10.1126/science.abg7586">published a paper in Science</a> that dated fossil footprints uncovered in New Mexico to around 23,000 years ago – the height of the last Ice Age. They were made by a group of people passing by an ancient lake near what’s now White Sands. The discovery added 7,000 years to the record of humans on the continent, rewriting American prehistory. </p>
<p>If humans were in America at the height of the last Ice Age, either the ice posed few barriers to their passage, or humans had been there for much longer. Perhaps they had reached the continent during an earlier period of melting. </p>
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Read more:
<a href="https://theconversation.com/fossil-footprints-prove-humans-populated-the-americas-thousands-of-years-earlier-than-we-thought-168426">Fossil footprints prove humans populated the Americas thousands of years earlier than we thought</a>
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<p>Our conclusions were criticised, however we have now published evidence confirming the early dates.</p>
<h2>Dating the pollen</h2>
<p>For many people, the word pollen conjures up a summer of allergies, sneezing and misery. But fossilised pollen can be a powerful scientific tool. </p>
<p>In our 2021 study, we carried out radiocarbon dating on common ditch grass seeds found in sediment layers above and below where the footprints were found. Radiocarbon dating is based on how a particular form – called an isotope – of carbon (carbon-14) undergoes radioactive decay in organisms that have died within the last 50,000 years.</p>
<p>Some researchers claimed that the radiocarbon dates in our 2021 research were too old because they were subject to <a href="https://heritagesciencejournal.springeropen.com/articles/10.1186/2050-7445-1-24">something called the “hard water” effect</a>. Water contains carbonate salts and therefore carbon. Hard water is groundwater that has been isolated from the atmosphere for some period of time, meaning that some of its carbon-14 has already undergone radioactive decay. </p>
<p>Common ditch grass is an aquatic plant and the critics said seeds from this plant could have consumed old water, scrambling the dates in a way that made them seem older than they were.</p>
<p>It’s quite right that they raised this issue. This is the way that science should proceed, with claim and counter-claim.</p>
<h2>How did we test our claim?</h2>
<p>Radiocarbon dating is robust and well understood. You can date any type of organic matter in this way as long as you have enough of it. So two members of our team, Kathleen Springer and Jeff Pigati of the United States Geological Survey set out to date the pollen grains. However, pollen grains are really small, typically about 0.005 millimetres in diameter, so you need lots of them.</p>
<p>This posed a formidable challenge: you need thousands of them to get enough carbon to date something. In fact, you need 70,000 grains or more.</p>
<p>Medical science provided a remarkable solution to our conundrum. We used a technique called flow cytometry, which is more commonly used for counting and sampling individual human cells, to count and isolate fossil pollen for radiocarbon dating. </p>
<p>Flow cytometry uses the fluorescent properties of cells, stimulated by a laser. These cells move through a stream of liquid. Fluorescence causes a gate to open, allowing individual cells in the flow of liquid to be diverted, sampled, and concentrated.</p>
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<img alt="Illustration of pollen grains." src="https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551051/original/file-20230928-25-iu74im.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">
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<span class="caption">Pollen can be a useful tool for dating evidence of human settlement.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/pollen-grains-different-plants-3d-illustration-1479353525">Kateryna Kon / Shutterstock</a></span>
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<p>We have pollen grains in all sediment layers between the footprints at White Sands, which allows us to date them. The key advantage of having so much pollen is that you can pick plants like pine trees that are not affected by old water. Our samples were processed to concentrate the pollen within them using flow cytometry. </p>
<p>After a year or more of labour intensive and expensive laboratory work, we were rewarded with dates based on pine pollen that validated the original chronology of the footprints. They also showed that old water effects were absent at this site. </p>
<p>The pollen also allowed us to reconstruct vegetation that was growing when people made the footprints. We got exactly the kinds of plants we would expect to have been there during the Ice Age in New Mexico. </p>
<p>We also used a different dating technique <a href="https://www.nature.com/articles/s43586-021-00068-5">called optically stimulated luminescence</a> (OSL) as an independent check. OSL relies on the accumulation of energy within buried grains of quartz over time. This energy comes from the background radiation that’s all around us.</p>
<p>The more energy we find, the older we can assume the quartz grains are. This energy is released when the quartz is exposed to light, so what you are dating is the last time the quartz grains saw sunlight.</p>
<p>To sample the buried quartz, you drive metal tubes into the sediment and remove them carefully to avoid exposing them to light. Taking quartz grains from the centre of the tube, you expose them to light in the lab and measure the light emitted by grains. This reveals their age. The dates from OSL supported those we got using other techniques.</p>
<p>The humble pollen grain and some marvellous medical technology helped us confirm the dates the footprints were made, and when people reached the Americas.</p><img src="https://counter.theconversation.com/content/213714/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Robert Bennett receives funding from UK Arts and Humanities Research Council. </span></em></p><p class="fine-print"><em><span>Sally Christine Reynolds receives funding from Arts and Humanities Research Council (AHRC)</span></em></p>
The early settlement of the Americas is hugely contested area of archaeology.
Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University
Sally Christine Reynolds, Associate Professor in Hominin Palaeoecology, Bournemouth University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/205558
2023-05-12T06:05:38Z
2023-05-12T06:05:38Z
A new source of fire records, hidden in the sands, gives us a bigger picture of the risks
<figure><img src="https://images.theconversation.com/files/525761/original/file-20230512-45337-n0e6sy.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1024%2C685&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">James Shulmeister</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Sand dunes are not an obvious place to find high-quality fire records. For a start, anyone who walks on the forested sand dunes of South-East Queensland will be impressed by the intensity of ant activity at their feet. The ant nests extend at least 2 metres below the surface. As the ants move materials around their nests, any charcoal from past fires that’s preserved in the sand would be severely disturbed.</p>
<p>Somewhat surprisingly, though, soil pits dug at the bottom of the slope of dune front walls (the leading edge of a dune) revealed different sediment layers are preserved there. This shows ant activity is not intense on the foot slopes. It’s possible for undisturbed charcoal records to be recovered from this part of the dune.</p>
<p>Our newly published <a href="https://www.cambridge.org/core/journals/quaternary-research/article/reconstructing-holocene-fire-records-using-dune-footslope-deposits-at-the-cooloola-sand-mass-australia/18C3D72D859E958E85900B0F456EF7B0">research</a> focuses on four well-dated sand dunes. Unlike previous studies that extracted fire histories from sediment cores from lakes, bogs and other organic sediments, we extracted fire records from these dunes. We believe this is a breakthrough that will greatly expand the areas for which we can extract fire histories. </p>
<p>Swamps and lakes are typically found in more humid areas and near the coast, whereas sand dunes occur widely across drier areas of Australia, including desert regions. This new source of fire histories can help us broaden our understanding of fire in Australia.</p>
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<img alt="" src="https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525831/original/file-20230512-24-p8iehb.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">
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<span class="caption">Collecting charcoal samples from the soil profile of a 10,000-year dune for radiocarbon dating.</span>
<span class="attribution"><span class="source">Nick Patton</span>, <span class="license">Author provided</span></span>
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Read more:
<a href="https://theconversation.com/in-a-bad-fire-year-australia-records-over-450-000-hotspots-these-maps-show-where-the-risks-have-increased-over-20-years-204679">In a bad fire year, Australia records over 450,000 hotspots. These maps show where the risks have increased over 20 years</a>
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<h2>Why does a new source of fire records matter?</h2>
<p>Fire is important in the Australian landscape. Many ecosystems are designed not only to survive fire but need burns to survive and thrive. </p>
<p>In recent years, however, the scale and intensity of bushfires in Australia have increased, culminating in the <a href="https://theconversation.com/200-experts-dissected-the-black-summer-bushfires-in-unprecedented-detail-here-are-6-lessons-to-heed-198989">Black Summer</a> of 2019-20. During that summer, areas that did not normally burn severely were intensely burned. The fires caused long-lasting damage to vegetation and significant loss of both human and animal life and buildings. </p>
<p>There are concerns that if the climate patterns associated with the Black Summer fires become more established, Australia’s ecology could be permanently altered and human activities severely impacted in many regions.</p>
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Read more:
<a href="https://theconversation.com/200-experts-dissected-the-black-summer-bushfires-in-unprecedented-detail-here-are-6-lessons-to-heed-198989">200 experts dissected the Black Summer bushfires in unprecedented detail. Here are 6 lessons to heed</a>
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<p>There is an urgent need to better understand the role of fire in the Australian landscape, prompting a surge in research on both modern fire behaviour and extracting fire histories from the landscape. These histories are crucial, because they can help us to identify and quantify the risk of fires. These studies can also highlight where climate and ecological changes have created new fire risk. </p>
<p>Scientists have until now relied on cores from lakes, bogs and other sources of organic sediments to extract fire histories. The gradual accumulation of these sediments preserves charcoal from past fires in layers. The layers can be dated, revealing the age of the charcoal and hence when the fire occurred. This means we can extract continuous records of past fire regimes from these sediments. </p>
<p>However, because of the focus on organic-rich sediments, these fire histories have been limited to humid areas, where swamps and lakes are present. Sediments like these are mostly close to the coast. Fire hazard is much more widely spread in Australia.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="maps of Australia and the world showing dryland distribution and paleofire records, as well as coastal and continental dunes in Australia" src="https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=724&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=724&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=724&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=909&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=909&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525767/original/file-20230512-31-vya9zw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=909&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) Orange areas show world dryland distribution (Sorensen, 2007) and white dots show published paleofire records from the Global Paleofire Database (Harrison et al., 2022). (b) View of Australia and the general locations of coastal (yellow) and continental (orange) dunes (Lees, 2006; Hesse, 2016). Much of Australia and the world is both covered in drylands and lacking fire histories.</span>
<span class="attribution"><a class="source" href="https://www.cambridge.org/core/journals/quaternary-research/article/reconstructing-holocene-fire-records-using-dune-footslope-deposits-at-the-cooloola-sand-mass-australia/18C3D72D859E958E85900B0F456EF7B0#figures">From Patton et al 2023/Quaternary Research</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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Read more:
<a href="https://theconversation.com/1-600-years-ago-climate-change-hit-the-australian-alps-we-studied-ancient-lake-mud-to-learn-what-happened-166825">1,600 years ago, climate change hit the Australian Alps. We studied ancient lake mud to learn what happened</a>
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<h2>So what did the dune study find?</h2>
<p>Our <a href="https://www.cambridge.org/core/journals/quaternary-research/article/reconstructing-holocene-fire-records-using-dune-footslope-deposits-at-the-cooloola-sand-mass-australia/18C3D72D859E958E85900B0F456EF7B0">study</a> focuses on the fire history of the Cooloola Sand Mass between Noosa and Tin Can Bay in South-East Queensland. We examined four well-dated sand dunes ranging from 500 to 10,000 years old. </p>
<p>In a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0012821X2200084X">2022 study</a>, we showed there are two distinct phases in the sediment records. These match a historic change in slope processes on the dunes. </p>
<p>For the first 1,000 years after the dunes stabilised, frequent but minor flows of sand grains down the front face of the dune slowly built up sediments at the foot of the dune. The sand deposited at the base includes the remnants of charcoal from local fires that deposited on the dune’s surface. This sediment builds up over time, preserving layers of charcoal from fires. </p>
<p>The distinct layers of charcoal in the sand represent individual fire events. These charcoal layers can be reliably identified using radiocarbon dating.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="graphic showing deposition at the bottom of dune of layers of charcoal from fires" src="https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525764/original/file-20230512-13703-7vug76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&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">Charcoal deposited on the dune surface by past fires collects in sediment layers at the base of the dune.</span>
<span class="attribution"><a class="source" href="https://www.cambridge.org/core/journals/quaternary-research/article/reconstructing-holocene-fire-records-using-dune-footslope-deposits-at-the-cooloola-sand-mass-australia/18C3D72D859E958E85900B0F456EF7B0">Patton et al 2023/Quaternary Research</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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Read more:
<a href="https://theconversation.com/a-dive-into-the-deep-past-reveals-indigenous-burning-helped-suppress-bushfires-10-000-years-ago-203754">A dive into the deep past reveals Indigenous burning helped suppress bushfires 10,000 years ago</a>
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<p>After about 1,000 years, the dune slopes became less steep. Slow soil creep, which is the gradual grain-by-grain movement of sand through the ground under gravity, became the dominant process. Charcoal is dispersed through the sediments. This means individual fires cannot be recognised but overall fire activity is still well recorded.</p>
<p>We compared the fire records from the sand dunes to local and regional fire histories. The records from the dunes matched the other records. Our records show a relationship between fire and stronger <a href="http://www.bom.gov.au/climate/about/?bookmark=enso">El Niño Southern Oscillation</a> (ENSO) periods – associated with more frequent drought conditions – in South-East Queensland.</p>
<p>There are very few fire histories from dryland regions worldwide. And, like Australia, extreme fires are increasing in these regions, which include California and Mediterranean Europe. We should now be able to better define natural fire hazard in these arid zones.</p><img src="https://counter.theconversation.com/content/205558/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R Patton has previously received funding from the Australian Research Council and from the National Science Foundation (USA).</span></em></p><p class="fine-print"><em><span>James Shulmeister receives funding from the Australian Research Council and from the Marsden Fund in New Zealand. The work discussed here is from an ARC Discovery grant. He has also previously received support through the National Science Foundation (USA) and the National Science Foundation of China and many other grant providers.</span></em></p>
Until now, a limitation of records of past fires is that these have come from sediments laid down in lakes and bogs. Records for dryland regions have been lacking, but dune deposits can fill the gap.
Nicholas R Patton, Postdoctoral Researcher, Integrated Terrain Analysis Program, Desert Research Institute
James Shulmeister, Adjunct Professor, University of Queensland, and Professor and Head of School of Earth and Environment, University of Canterbury
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/195523
2023-03-02T06:07:09Z
2023-03-02T06:07:09Z
Five discoveries that changed our understanding of how the ancient Egyptians created mummies
<figure><img src="https://images.theconversation.com/files/504886/original/file-20230117-26-38hfhw.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5607%2C3724&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/stone-pharaoh-tutankhamen-mask-on-dark-1092093353">Merydolla/Shutterstock</a></span></figcaption></figure><p>Centuries after the first golden coffins were taken to Europe, ancient Egyptian mummies still vividly capture people’s imaginations. Perhaps we’re awed by the grandeur of their rituals and tradition. But new discoveries keep challenging scientists’ perception of these ancient rites. </p>
<p>As a biomedical Egyptologist, I study mummies to learn about life in ancient populations. Over the last 10 years, I have seen a big change in our understanding of how, why and when mummies were created. This has mostly been driven by new scientific discoveries. Here are five of the most important ones that have changed what we know about this ancient process.</p>
<h2>1. Mummification is older than archaeologists imagined</h2>
<p>For decades, the oldest known mummies came from the Old Kingdom era (c.2500-2100BC) around the time Egyptians started using coffins more. These mummies are rare, but they show signs of being specially prepared by embalmers. Mummies from before the Old Kingdom period were thought to have been created naturally by burying bodies in graves cut into the hot, dry sand. Scientists thought embalming was developed to keep bodies preserved inside coffins. </p>
<p>But chemical tests published in <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103608">2014</a> and <a href="https://doi.org/10.1016/j.jas.2018.07.011">2018</a> showed that resins and perfumes were already being used to help preserve the skin of the dead over 6,000 years ago, before coffins were common and long before the Old Kingdom era. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-MQ5dL9cQX0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>2. The ‘recipe’ varied across Egypt</h2>
<p>Recent scientific studies of mummies and <a href="https://www.nature.com/articles/s41586-022-05663-4">pots used in mummification</a> revealed how methods differed from place to place and weren’t standardised, as previously thought. </p>
<p>Each region had its own <a href="https://www.smithsonianmag.com/smart-news/ancient-egyptian-funeral-home-reveals-embalmers-had-knack-business-180974823/">embalming workshops</a> where mummies were produced in a complicated and closely guarded ritual. This secrecy means very few records survived. </p>
<p>Embalmers living in politically important areas such as <a href="https://static1.squarespace.com/static/5398fa85e4b07784a2762d33/t/59b1d781a8b2b050d1c1ec73/1504827301089/Changing_Burial_Practices_at_the_End_of.pdf">Thebes</a> (modern-day Luxor) had access to the latest mummification materials, as part of an extensive trade network. In more remote areas such as oases, embalmers had to make do. <a href="https://pubmed.ncbi.nlm.nih.gov/11625036/#:%7E:text=Natron%20or%20native%20soda%2C%20a,and%20to%20dehydrate%20egyptian%20mummies.">Natron salt</a>, used to dry the body, was heavy and difficult to transport. Resins and perfumes could be expensive as they were <a href="https://www.thetimes.co.uk/article/mummies-unravel-trade-links-of-the-ancient-world-7m0jmw6r8">traded over long distances</a> in exchange for other luxury goods. </p>
<p>Instead, the embalmers in these remote areas developed <a href="https://www.academia.edu/58456672/Mummification_practices_at_Kellis_site_in_Egypts_Dakhleh_Oasis">creative techniques</a>. For instance, they used sticks to make mummy bundles more rigid or to attach body parts that fell off during mummification. They also created composite mummies, made up of the parts of several people.</p>
<p>We don’t fully understand how experimentation in mummification emerged in different areas or time periods. There was probably an element of trial and error though.</p>
<h2>3. Ancient accounts were not always reliable</h2>
<p>The information we have about mummification comes mostly from two ancient Greek writers, <a href="https://www.livius.org/sources/content/herodotus/mummification/">Herodotus</a> and <a href="https://www.livius.org/sources/content/diodorus/">Diodorus Siculus</a>. They describe the steps of mummification such as using a hook to remove the brain through the nose. They also tell us the heart was left in the body because it was thought to be important for the afterlife. </p>
<p><a href="https://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1002&context=anthropres">Scientific studies</a> using CT scanning have now shown the rules of mummification were less rigid than Herodotus and Diodorus Siculus thought. Only around a quarter of known mummies have their heart left in the body. And many mummies <a href="https://ir.lib.uwo.ca/etd/453/">still have their brain</a>. If the embalmers did take the brain out, they sometimes used <a href="https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.24828">different methods</a> to avoid damaging the face. Holes have been found in the bottom of the skull and through different routes into the nose. </p>
<figure class="align-center ">
<img alt="Egyptian mummy close up detail with hieroglyphs background" src="https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504887/original/file-20230117-24-azo53o.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">Not everyone could afford new linens or coffins for their dead loved one.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/egyptian-mummy-close-detail-hieroglyphs-background-422842150">Andrea Izzotti/Shutterstock</a></span>
</figcaption>
</figure>
<h2>4. Egyptians upcycled coffins</h2>
<p>In ancient Egypt, wood for coffins was scarce and <a href="https://www.ibaes.de/ibaes7/publikation/cooney_ibaes7.pdf">expensive</a>. Not everyone could afford a new coffin or linen wrappings. A good coffin – but not a luxurious one – in the New Kingdom would <a href="https://static1.squarespace.com/static/5398fa85e4b07784a2762d33/t/59b599262278e7557eca6160/1505073457922/Cooney+offprint+-+To+Live+Forever_color_Bleiberg.pdf">cost about five goats</a> or 250 loaves of bread. </p>
<p>Upcycling and recycling are not modern concepts. To save money, embalmers would often <a href="https://kar.zcu.cz/studium/materialy/egy/texty-pro-studenty-2012/Baines_Lacovara2002.pdf">take coffins from tombs</a> already in use. These could be repainted to include the name of the new owner or the parts were sometimes used to fashion a new coffin. Tombs were often raided by robbers looking for valuables, and afterwards they were often left open. This made it easy for others to search the tomb for coffins and wrappings to reuse. </p>
<p>Household linens were also often used as mummy wrappings once they outlived their usefulness. Modern research techniques such as <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">radiocarbon dating</a> are showing this practice was widespread. Coffin materials, linen wrappings and other materials are sometimes dated <a href="https://doi.org/10.1016/j.jasrep.2022.103784">several hundred years older</a> than the person they were buried with.</p>
<h2>5. The tourist trade scrambled history</h2>
<p>We now know mummies in museums outside of Egypt are <a href="https://www.sciencedirect.com/science/article/pii/S2352409X21003989#b0210">not always in the coffins they were discovered in</a>. Many mummies are given a historical date based on their coffin style and decoration. The shape, decoration and religious texts on them changed over time. </p>
<p>But in the 19th and early 20th centuries, mummies were sold to tourists, scientists or collectors. Sellers put well-wrapped mummies into coffins from different tombs to encourage people to buy them. The mismatch only comes to light when a mummy is <a href="https://doi.org/10.1017/S0033822200056502">studied scientifically</a>. </p>
<p>It is now illegal to take mummies or any other ancient artefact from Egypt. There are still a lot of mummies left in private houses though, bought more than a century ago and sometimes forgotten about. </p>
<p>Instead of one unwavering tradition, Egyptian mummification was variable. The funerary rituals available to someone demonstrated how important they and their family were. Being mummified using the most up-to-date techniques and materials not only helped secured a person’s position in the afterlife, it was an important sign of status.</p>
<p>It is impossible to know what the next archaeological or scientific find will show us. But one thing is clear: even ancient embalmers had to improvise sometimes.</p><img src="https://counter.theconversation.com/content/195523/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenefer Metcalfe works for The University of Manchester, UK.</span></em></p>
Several studies have upended what we thought we knew about mummification using scientific dating techniques to reveal some fascinating – and surprising – insights.
Jenefer Metcalfe, Lecturer in Biomedical Egyptology, University of Manchester
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/197204
2023-01-18T16:34:49Z
2023-01-18T16:34:49Z
Red Lady of Paviland: the story of a 33,000 year-old-skeleton – and the calls for it to return to Wales
<figure><img src="https://images.theconversation.com/files/505135/original/file-20230118-7884-mtwnjq.jpg?ixlib=rb-1.1.0&rect=123%2C8%2C1787%2C1060&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Human remains dating back more than 30,000 years were found at Paviland cave in Gower. </span> <span class="attribution"><span class="source">Left: Leighton Collins/Shutterstock; right: Ethan Doyle White CC BY-SA 3.0. </span></span></figcaption></figure><p>When William Buckland from the University of Oxford grabbed his trusty collecting bag and headed for the Gower peninsula in south Wales in January 1823, he ended up discovering more than he had bargained for.</p>
<p>It is 200 years to the day since the geology professor happened upon one of the oldest human burial sites in western Europe, kicking off an archaeological debate that would last for the next two centuries. The anniversary of his discovery has once again sparked a debate about whether the human remains should now be repatriated from Oxford to Wales.</p>
<p>In December 1822, Buckland had received a package containing an elephant tusk and skull (which was really a mammoth), along with a basket full of animal bones. The finds from Paviland cave had been sent by Lady Mary Cole, who lived in Penrice Castle, Gower. The package was so intriguing to Buckland he decided he needed to visit the location in person. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large rocky mound with a small cave entrance." src="https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504922/original/file-20230117-11-jm1g8h.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Paviland cave on the Gower peninsula, where a human skeleton covered in red ochre was discovered by William Buckland in January 1823.</span>
<span class="attribution"><span class="source">Ffion Reynolds</span></span>
</figcaption>
</figure>
<p>Buckland, an Anglican priest, was operating at an important juncture in the study of human and geological time. He was about to publish his seminal work, <a href="https://wellcomecollection.org/works/k7twatkd">Reliquiae Diluvianae</a>, in which religion and science were thrust together as one.</p>
<p>At the time, our account of human history was still largely dictated by the chronology of the Bible. This meant Buckland clung to the idea of a cataclysmic biblical “deluge”. </p>
<p>He was adamant any extinct animals found during his explorations had been washed into the caves by the great flood. This idea became his biggest problem when trying to decipher the depth of time presented at Paviland. </p>
<h2>A skeleton story</h2>
<p><a href="https://heritagerecords.nationaltrust.org.uk/HBSMR/MonRecord.aspx?uid=MNA132642">Paviland, or Goat’s Hole cave</a>, is a limestone cave between Rhossili and Port Eynon on the Gower coast. Today, as at the time of Buckland, the cave is cut off by the tide for most of the year. Buckland visited during winter when tides are at their lowest, meaning he was able to enter and start his excavations immediately. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504925/original/file-20230117-12-l20ajb.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&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 limestone cave of Paviland, with its distinctive tear drop-shaped entrance. Ffion Reynolds.</span>
</figcaption>
</figure>
<p>It wasn’t long before he found an undisturbed burial of human bones and objects, all stained red with ochre. The remains lacked a skull, but on excavation were found to be surrounded by ivory objects (including rods and rings), a clutch of periwinkle shells, and worked flints. Buckland took them back with him to Oxford.</p>
<p>At first he thought <a href="https://www.jstor.org/stable/4028256">the human bones were those of a man</a>, and joked that they belonged to a tax collector who had been murdered by smugglers, for which this coastal area was notorious. </p>
<p>Next, Buckland suggested the remains belonged to a witch, due to the presence of a “<a href="https://www.jstor.org/stable/531750">blade bone of mutton</a>”. Based on his knowledge of Welsh customs, he imagined this was used as some kind of conjuring tool. </p>
<p>Finally, he argued the skeleton was that of a painted <a href="https://www.geolsoc.org.uk/Library-and-Information-Services/Collection-Highlights/Brixham-Cave-and-the-Antiquity-of-Man/William-Buckland-and-the-Red-Lady-of-Paviland">female prostitute</a>, which made the shell beads implements of gambling, while the rings were jewellery made from Roman elephant ivory. This was the story he stuck to, and the one which best fitted his biblical flood theory. </p>
<p>The real issue is that Buckland did not seem to have studied the human bones in detail. Perhaps even if he had, he wanted to suppress what he found. Had he examined the bones properly, he would have noticed the individual wasn’t female but a young male, aged 25–30, who stood about 173cm (5ft 7in) in height.</p>
<p>Buckland’s theories had buckled.</p>
<h2>Who was really buried here?</h2>
<p>In 2008, <a href="https://pubmed.ncbi.nlm.nih.gov/18929395/">radiocarbon-dating techniques</a> conclusively showed these bones belonged to an individual buried around 33,000 years ago.</p>
<p>Paviland, at this time, would have been located at least 60 miles inland, on a cliff above a grassy plain. The landscape would have been teeming with prey such as mammoths, woolly rhinos, giant deer, bison and reindeer.</p>
<figure class="align-center ">
<img alt="Person standing inside a cave" src="https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504927/original/file-20230117-12-frkc0u.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ffion Reynolds at Paviland cave, taken during the low spring tides of March 2016 when the cave was accessible for a few hours.</span>
<span class="attribution"><span class="source">Ffion Reynolds</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Buckland was spinning a yarn, however, and wanted to largely ignore the human burial as it did not fit his theories. As a result, Wales lost its opportunity to be at the forefront of Palaeolithic studies, which shifted instead to a European focus.</p>
<p>Between their discovery and the present day, the Paviland bones have been on a journey from tax man, witch, prostitute and Palaeolithic hunter to the more recent suggestions of shaman or spiritual figure. People now visit the cave as a form of pilgrimage. But there have also been <a href="https://www.walesonline.co.uk/news/wales-news/welsh-am-demands-return-one-6334745">calls for the skeleton to take another journey</a> – back to Wales.</p>
<h2>Repatriation</h2>
<p>Buckland did return some of his finds from Oxford to Wales. The hyena jaw bones are displayed at Swansea Museum, while an ivory staff is stored at St Fagans National Museum of History in Cardiff. </p>
<p>But the remarkable human remains are still <a href="https://oumnh.ox.ac.uk/learn-red-lady-of-paviland-0#listing_536071_0">on display at the University of Oxford’s Museum of Natural History</a>. Some have called these bones the <a href="https://twitter.com/matthewmcsmith/status/1612126154445529089?s=46&t=LJl0--vgrh7V1GIzfmYXUA">“Welsh Elgin marbles”</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1614659433237299201"}"></div></p>
<p>With the real Elgin marbles now <a href="https://www.nytimes.com/2023/01/17/arts/design/parthenon-sculptures-elgin-marbles-negotiations.html">poised to make their way back to Greece</a> from the British Museum, is it time for the human remains from Paviland to <a href="https://www.bbc.co.uk/news/uk-wales-64264413">come back to Wales?</a></p>
<p>Repatriation is a complex issue. From the <a href="https://www.bbc.co.uk/news/uk-wales-61082954">Mold Gold Cape</a> to the <a href="https://www.theguardian.com/world/2022/dec/20/germany-returns-21-benin-bronzes-to-nigeria-amid-frustration-at-britain">Benin Bronzes</a>, returning materials to nations or regions attracts controversy. </p>
<p>The Paviland remains are well cared for where they are, so there’s a question as to whether they should “come home” at all. A further debate is whether they should be returned as an ancestor or an exhibit.</p>
<p>However, the importance of this individual to European and global histories means their return would certainly enhance the Welsh national collection – and shine a spotlight on the unique archaeology and caves of Wales.</p><img src="https://counter.theconversation.com/content/197204/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ffion Reynolds is affiliated with Cadw, the historic environment service for the Welsh Government. </span></em></p><p class="fine-print"><em><span>Jacqui Mulville 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>
It’s been 200 years since the discovery of one of the oldest human burial sites in western Europe on the Gower peninsula in south Wales.
Ffion Reynolds, Honorary Research Fellow, Cardiff University
Jacqui Mulville, Professor in Bioarchaeology, Head of Archaeology and Conservation, Cardiff University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/194155
2022-11-08T22:48:37Z
2022-11-08T22:48:37Z
New research shows ancestral Māori adapted quickly in the face of rapid climate change
<figure><img src="https://images.theconversation.com/files/494262/original/file-20221108-12-k5dfp3.jpg?ixlib=rb-1.1.0&rect=131%2C1077%2C7856%2C2802&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock/Anton Balazh</span></span></figcaption></figure><p>When the ancestors of Māori made landfall in Aotearoa some 750 years ago, it marked the final stop of the greatest expansion of human migration in prehistory. </p>
<p>Much of their story – exactly when they arrived and where they initially settled, how quickly the population grew, and how they sustained themselves and adapted during rapidly changing climate conditions – has remained elusive until now.</p>
<p>Our <a href="http://doi.org/10.1073/pnas.2207609119">research</a> traces the first 250 years of settlement, including changes in resource availability and population growth. It provides a more precise timeline for arrival and settlement, beginning as early as 1250-1270. </p>
<p>We also demonstrate for the first time a difference in the age of settlements in the North and South islands. The research shows that Māori adapted quickly to their new environment and again during later periods when temperature and rainfall changed significantly.</p>
<figure class="align-center ">
<img alt="A map of the earliest settlement of Aotearoa." src="https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494090/original/file-20221108-16-qgk6rf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The changing distribution of archaeological sites across Aotearoa. The red ellipse marks the distribution of the volcanic deposits from the Kaharoa eruption around 1314.</span>
<span class="attribution"><span class="source">Authors provided</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>A more precise timeline of arrival</h2>
<p>People travelled from tropical islands in East Polynesia at a time when a warm climate <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1408918111">facilitated travel across the world’s largest ocean</a>. </p>
<p>Researchers have long debated the exact timing of their first settlement, with estimates varying between the 12th and 14th centuries, depending on the material selected for radiocarbon dating.</p>
<p>We show that early settlers reached the North Island first, between 1250 and 1270, a decade before the South Island became more popular. </p>
<p>At the time of settlement, the south had <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1314972111">colonies of the large flightless moa</a>. The early settlers rapidly adapted to this temperate climate, living on a diet of moa, seafood and vegetables grown in their garden plots.</p>
<figure class="align-center ">
<img alt="A landscape image of Wairau Bar, a coastal site of early settlemnt in the South Island." src="https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494276/original/file-20221108-11-48fhal.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">Wairau Bar in Marlborough is thought to be one of the earliest sites of settlement in the South Island.</span>
<span class="attribution"><span class="source">Fiona Petchey</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>But then the <a href="https://www.science.org/doi/10.1126/science.1177303">Little Ice Age</a> interfered with this lifestyle. After 1350, conditions became significantly colder in the south. By around 1400-1420, moa hunting became uneconomic and put these fledgling communities under immense pressure. Once again, people had to adapt quickly.</p>
<p>Models developed from radiocarbon dates and the distribution of archaeological sites indicate the population shifted back to the north and grew between 1350 and 1450. In the north, soils were ideal for agriculture and temperatures were warmer.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-aotearoa-new-zealands-early-polynesian-settlement-should-be-recognised-with-world-heritage-site-status-149981">Why Aotearoa New Zealand's early Polynesian settlement should be recognised with World Heritage Site status</a>
</strong>
</em>
</p>
<hr>
<h2>New scientific approach</h2>
<p>Estimates of arrival and settlement in earlier studies and models vary depending on the material they used. For example, <a href="https://journals.sagepub.com/doi/10.1191/0959683604hl760ft">radiocarbon dates of the Pacific rat</a> (<em>Rattus exulans</em> or kiore) tell a story about the spread of rats following the introduction by Māori ancestors. This study documents an explosion in the rat population but not information on the earliest human settlement date. </p>
<p>Likewise, radiocarbon dates on <a href="https://www.sciencedirect.com/science/article/abs/pii/S0305440314002015">moa eggshell and bone</a> tell us about the timing of moa-hunting activities but little about activities elsewhere. </p>
<p>This piecemeal approach has blurred the settlement chronology and contributed to the notion of a “<a href="https://link.springer.com/article/10.1007/s10963-017-9110-y">mass migration</a>” event. These studies also ignored dates on <a href="https://www.nature.com/articles/s41598-020-70227-3">marine materials</a>, one of the most commonly dated sample types.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/linguistics-locates-the-beginnings-of-the-austronesian-expansion-with-indigenous-seafaring-people-in-eastern-taiwan-186547">Linguistics locates the beginnings of the Austronesian expansion – with Indigenous seafaring people in eastern Taiwan</a>
</strong>
</em>
</p>
<hr>
<p>In a previous <a href="http://www.nature.com/articles/s41598-020-70227-3">study</a>, we demonstrated that dates of midden shells could increase the accuracy of models if we had a better understanding of how radiocarbon in the ocean changed over time. </p>
<p>The development of a regional marine calibration curve that mapped this change allowed us to include more than 800 shell radiocarbon dates in the current study. This curve doubled the number of dates available for analysis.</p>
<figure class="align-center ">
<img alt="An image showing the edge of a shell" src="https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494253/original/file-20221108-18-qbilcn.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">Toitoi (<em>Cookia sulcata</em>) shell from an early archaeological site.</span>
<span class="attribution"><span class="source">Fiona Petchey</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>It was also necessary to develop a new approach to modelling that combined terrestrial and marine radiocarbon data sets. The increased precision and accuracy of these new models enabled us to draw links between the number and distribution of archaeological sites, climate, resources and deforestation trends.</p>
<h2>Why our results are more precise</h2>
<p>We scoured journal papers and books to assemble more than 2,250 dates, the largest radiocarbon data set from any island context. We carefully evaluated the archaeological context and scientific reliability of each date and removed almost 700 problematic dates before modelling began.</p>
<p>Differences between the terrestrial and marine calibration curves used to convert radiocarbon measurements into calendar ages enabled us to refine “<a href="https://researchcommons.waikato.ac.nz/handle/10289/5248">wiggles</a>” that result in multiple ranges for some early settlement events.</p>
<p>This research goes only a small way to providing a time baseline for understanding the complexity of ancestral Māori society. <a href="https://www.royalsociety.org.nz/what-we-do/funds-and-opportunities/marsden/awarded-grants/marsden-fund-highlights/2021-marsden-fund-highlights/using-marine-shells-to-accurately-locate-early-maori-settlers-in-time">Future work</a> aims to achieve the precision needed to establish more links between people, climate and time.</p>
<hr>
<p><em>We would like to acknowledge the contribution to this research by Simon Bickler, director of Bickler Consultants.</em></p><img src="https://counter.theconversation.com/content/194155/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Magdalena Bunbury receives funding from Australian Research Council (ARC) and previously from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)</span></em></p><p class="fine-print"><em><span>Fiona Petchey's work is supported by a University of Waikato Marsden Support Grant</span></em></p>
A more precise timeline now shows Polynesian ancestors of Māori first settled in the North Island before expanding south and then retreating again when the climate changed.
Magdalena Bunbury, Postdoctoral research fellow, James Cook University
Fiona Petchey, Associate Professor and Director, Radiocarbon Dating Laboratory, Te Aka Mātuatua - School of Science, University of Waikato
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/193080
2022-10-25T23:04:46Z
2022-10-25T23:04:46Z
Radioactive traces in tree rings reveal Earth’s history of unexplained ‘radiation storms’
<figure><img src="https://images.theconversation.com/files/491154/original/file-20221023-40716-6xlwd2.jpg?ixlib=rb-1.1.0&rect=52%2C37%2C4940%2C3952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">University of Queensland</span></span></figcaption></figure><p>In searching for planets and studying their stars, I’ve had the privilege to use some of the world’s great telescopes. However, our team has recently turned to an even larger system to study the cosmos: Earth’s forests. </p>
<p>We analysed radioactive signatures left in tree rings around the world to study mysterious “radiation storms” that have swept over Earth half a dozen times in the past 10,000 years or so.</p>
<p>Our results, published today in <a href="https://doi.org/10.1098/rspa.2022.0497">Proceedings of the Royal Society A</a>, rule out “solar superflares” as the culprit – but the true cause remains unknown.</p>
<h2>A history written in tree rings</h2>
<p>When high-energy radiation strikes the upper atmosphere it turns nitrogen atoms into radioactive carbon-14, or radiocarbon. The radiocarbon then filters through the air and the oceans, into sediments and bogs, into you and me, into animals and plants - including hardwoods with their yearly tree rings. </p>
<p>To archaeologists, radiocarbon is a godsend. After it is created, carbon-14 slowly and steadily decays back into nitrogen – which means it can be used as a clock to measure the age of organic samples, in what is called <a href="https://www.nature.com/articles/s43586-021-00058-7">radiocarbon dating</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">Explainer: what is radiocarbon dating and how does it work?</a>
</strong>
</em>
</p>
<hr>
<p>To astronomers, this is equally valuable. Tree rings give a year-by-year record of high-energy particles called “cosmic rays” <a href="https://www.nature.com/articles/s41561-020-00674-0">going back millennia</a>. </p>
<p>The magnetic fields of Earth and the Sun shield us from cosmic rays shooting through the Galaxy. More cosmic rays reach Earth when these magnetic fields are weaker, and fewer when the fields are stronger.</p>
<p>This means the rise and fall of carbon-14 levels in tree rings encodes a history of <a href="https://sci-hub.se/10.1126/science.207.4426.11">the 11-year cycle of the solar dynamo</a> (which creates the Sun’s magnetic field) and the reversals of <a href="https://www.science.org/doi/full/10.1126/science.abb8677">Earth’s magnetic field</a>. </p>
<h2>Miyake events</h2>
<p>But tree rings also record events we cannot presently explain. In 2012, Japanese physicist Fusa Miyake <a href="https://ui.adsabs.harvard.edu/abs/2012Natur.486..240M/abstract">discovered a spike</a> in the radiocarbon content of tree rings from 774 AD. It was so big that several ordinary years’ worth of cosmic rays must have arrived all at once. </p>
<p>As more teams have joined the search, tree ring evidence has been uncovered of further “Miyake events”: from <a href="https://ui.adsabs.harvard.edu/abs/2013NatCo...4.1748M/abstract">993 AD</a> and <a href="https://www.cambridge.org/core/journals/radiocarbon/article/relationship-between-solar-activity-and-14c-peaks-in-ad-775-ad-994-and-660-bc/EFBDD78DEFAAA02B1CB9C3A24933B912">663 BC</a>, and prehistoric events in <a href="https://www.nature.com/articles/s41467-022-28804-9">5259 BC</a>, <a href="https://ui.adsabs.harvard.edu/abs/2021GeoRL..4893419M/abstract">5410 BC</a>, and <a href="https://www.nature.com/articles/s41467-021-27891-4">7176 BC</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-large-solar-storm-could-knock-out-the-power-grid-and-the-internet-an-electrical-engineer-explains-how-177982">A large solar storm could knock out the power grid and the internet – an electrical engineer explains how</a>
</strong>
</em>
</p>
<hr>
<p>These have already led to a revolution in archaeology. Finding one of these short, sharp spikes in an ancient sample <a href="https://royalsocietypublishing.org/doi/10.1098/rspa.2016.0263">pins its date down to a single year</a>, instead of the decades or centuries of uncertainty from ordinary radiocarbon dating. </p>
<p>Among other things, our colleagues have used the 993 AD event <a href="https://www.nature.com/articles/s41586-021-03972-8">to reveal the exact year</a> of the first European settlement in the Americas, the Viking village at L'Anse aux Meadows in Newfoundland: 1021 AD. </p>
<h2>Could huge radiation pulses happen again?</h2>
<p>In physics and astronomy, these Miyake events remain a mystery. </p>
<p>How do you get such a huge pulse of radiation? A flurry of papers have blamed supernovae, <a href="https://ui.adsabs.harvard.edu/abs/2013MNRAS.430...32H">gamma-ray bursts</a>, <a href="https://ui.adsabs.harvard.edu/abs/2019ApJ...887..202W/abstract">explosions from magnetised neutron stars</a>, and even <a href="https://www.nature.com/articles/srep03728">comets</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photograph of solar flares emanating from the Sun." src="https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=491&fit=crop&dpr=1 600w, https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=491&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=491&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=617&fit=crop&dpr=1 754w, https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=617&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/491521/original/file-20221025-18-a2bs48.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=617&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Could ‘solar superflares’ be responsible for radiocarbon spikes in tree rings?</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia21958-major-solar-flare">NASA / GSFC / Solar Dynamics Observatory</a></span>
</figcaption>
</figure>
<p>However, the <a href="https://ui.adsabs.harvard.edu/abs/2013A%26A...552L...3U/abstract">most widely accepted explanation</a> is that Miyake events are “solar superflares”. These hypothetical eruptions from the Sun would be perhaps 50–100 times more energetic than the biggest recorded in the modern era, the <a href="https://en.wikipedia.org/wiki/Carrington_Event">Carrington Event</a> of 1859. </p>
<p>If an event like this occurred today, it would <a href="https://astronomy.com/news/2021/09/understanding-just-how-big-solar-flares-can-get">devastate power grids, telecommunications, and satellites</a>. If these occur randomly, around once every thousand years, that is a 1% chance per decade – a serious risk. </p>
<h2>Noisy data</h2>
<p>Our team at UQ set out to sift through all the available tree ring data and pull out the intensity, timing, and duration of Miyake events. </p>
<p>To do this we had to develop software to solve a <a href="https://johncarlosbaez.wordpress.com/2012/07/24/carbon-cycle-box-models/">system of equations</a> that model how radiocarbon filters through the entire <a href="https://en.wikipedia.org/wiki/Carbon_cycle">global carbon cycle</a>, to work out what fraction ends up in trees in what years, as opposed to the oceans, bogs, or you and me. </p>
<p>Working with archaeologists, we have just released the first reproducible, systematic study of <a href="https://github.com/qingyuanzhang3/radiocarbon_workflow/tree/main/data">all 98 trees of published data</a> on Miyake events. We have also released <a href="https://sharmallama.github.io/ticktack">open source modelling software</a> as a platform for future work.</p>
<h2>Storms of solar flares</h2>
<p>Our results confirm each event delivers between one and four ordinary years’ worth of radiation in one go. <a href="https://www.nature.com/articles/s41467-018-05883-1">Earlier research</a> suggested trees closer to Earth’s poles recorded a bigger spike – which is what we would expect if solar superflares are responsible – but our work, looking at a larger sample of trees, shows this is not the case.</p>
<p>We also found these events can arrive at any point in the Sun’s 11-year activity cycle. Solar flares, on the other hand, <a href="https://link.springer.com/article/10.1007/s11207-021-01831-3">tend to happen</a> around <a href="https://arxiv.org/abs/2207.12787v2">the peak of the cycle</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-is-the-sun-going-quiet-22155">Why is the sun going quiet?</a>
</strong>
</em>
</p>
<hr>
<p>Most puzzling, a couple of the spikes seem to take longer than can be explained by the slow creep of new radiocarbon through the carbon cycle. This suggests that either the events can sometimes take longer than a year, which is not expected for a giant solar flare, or the growing seasons of the trees are not as even as previously thought.</p>
<p>For my money, the Sun is still the most likely culprit for Miyake events. However, our results suggest we’re seeing something more like a storm of solar flares rather than one huge superflare. </p>
<p>To pin down what exactly happens in these events, we will need more data to give us a better picture of the events we already know about. To obtain this data, we will need more tree rings – and also other sources such as <a href="https://ui.adsabs.harvard.edu/abs/2015NatCo...6.8611M/abstract">ice cores from the Arctic and Antarctic</a>.</p>
<p>This is truly interdisciplinary science. Normally I think about beautifully clean, precise telescopes: it is much harder to understand the complex, interconnected Earth.</p><img src="https://counter.theconversation.com/content/193080/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Benjamin Pope receives funding from the Australian Research Council and the Big Questions Institute. </span></em></p>
Half a dozen times in the past 10,000 years, enigmatic ‘Miyake events’ have showered Earth with cosmic rays.
Benjamin Pope, ARC DECRA Fellow, The University of Queensland
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/189493
2022-09-07T16:20:45Z
2022-09-07T16:20:45Z
Radiocarbon dating only works half the time – we may have found the solution
<figure><img src="https://images.theconversation.com/files/482033/original/file-20220831-23-mdvalg.jpg?ixlib=rb-1.1.0&rect=64%2C40%2C5325%2C3547&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A new DNA method could help making it easier to date skeletons</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/parts-skeleton-folded-together-on-ground-1089714116">Malinka333/Shutterstock</a></span></figcaption></figure><p>Dating is everything in archaeology. Exciting discoveries of ancient burial sites or jewellery might make headlines, but for scientists, this kind of discovery is only meaningful if we can tell how old the artefacts are. </p>
<p>So when chemist Willard Libby developed radiocarbon dating in 1946, it was a breakthrough for archaeology and he was awarded a <a href="https://www.nobelprize.org/prizes/chemistry/1960/libby/biographical/">Nobel prize</a> for his achievement. </p>
<p>Nowadays people take radiocarbon technology for granted and many people think you can use radiocarbon on any human remains. Scientists wish that was true, but in reality, only 50% of corpses can be dated <a href="http://eprints.gla.ac.uk/133493/13/133493.pdf">using this method</a> because in some skeletons there isn’t enough organic material or <a href="https://www.nationalgeographic.com/culture/article/radiocarbon-dating-explained">it is contaminated</a>. </p>
<p>Many exciting finds have been <a href="https://www.nature.com/articles/d41586-020-01499-y">inaccurately dated</a> or not dated at all, meaning the skeletons’ clues from the past are still locked away. But my team may have found the key: <a href="https://www.cell.com/cell-reports-methods/fulltext/S2667-2375(22)00147-3">DNA dating</a>. </p>
<h2>How radiocarbon dating works</h2>
<p>To understand why we need DNA dating, you need to know what radiocarbon dating is. It allows us to date organic material (that is younger than 50,000 years) based on the chemical reactions that the body exchanges with the environment after death. </p>
<p>Carbon is found in all living things and is the backbone of all molecules. We absorb it when we eat food and exhale it into the atmosphere. Radiocarbon dating compares the three different isotopes (a type of atom) of carbon. </p>
<p>The most abundant, <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/carbon-12">carbon-12</a>, remains stable in the atmosphere. It’s a good yardstick to measure the age of skeletons as one of the other isotopes, <a href="https://www.theguardian.com/science/2019/aug/10/most-important-isotope-how-carbon-14-revolutionised-science">carbon-14 </a> is radioactive and decays over time. </p>
<p>Since animals and plants stop absorbing carbon-14 when they decay, the radioactivity of the carbon-14 that’s left behind reveals their age. But there’s a catch. Low amounts of organic material, the diet of the dead person or animal, and contamination with modern samples can skew the calculation.</p>
<p>Variation in dating between labs alone can be up to <a href="https://www.cambridge.org/core/journals/radiocarbon/article/ams-radiocarbon-dating-of-ancient-bone-using-ultrafiltration/14A0C1A38EAE80CB5526110FFDECE70E">1,000 years</a>. It is like dating Queen Elizabeth II to William the Conqueror’s time. </p>
<figure class="align-center ">
<img alt="Queen Elizabeth holds a bouquet" src="https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482778/original/file-20220905-2147-knprbk.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">William the Conqueror lived a thousand years before the UK’s current monarch, Queen Elizabeth II.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/salisbury-wiltshire-uk-may-1st-2012-2185927775">Simon Ward Photography/Shutterstock</a></span>
</figcaption>
</figure>
<p>The alternative to radiocarbon dating is using <a href="https://www.ucl.ac.uk/museums-static/digitalegypt/archaeology/dating.html#:%7E:text=The%20dating%20of%20remains%20is,name%20of%20a%20dated%20individual">archaeological artefacts</a> found alongside human remains. This works if we find a skeleton carrying a coin minted by Julius Caesar, say. But that rarely happens. </p>
<p>The earliest human remains in Afghanistan were found in the <a href="https://www.researchgate.net/publication/316750392_Direct_radiocarbon_dating_and_DNA_analysis_of_the_Darra-i-Kur_Afghanistan_human_temporal_bone">Darra-i-Kur cave</a> in Badakhshan. They were initially assumed to be from the Paleolitihc era (30,000 years before the present), based on radiocarbon dating of charcoal and soil samples. But a later <a href="https://www.sciencedirect.com/science/article/abs/pii/S0047248417301136">study</a> measured skull fragments found in the cave against modern human skulls and realised it was closer to modern human form than Neanderthal. The skull fragment was radiocarbon dated to the Neolithic, some 25,000 years later. The mistake was due to inadequate carbon samples. It was the first ancient human from Afghanistan to have their DNA sequenced.</p>
<h2>A new dating tool</h2>
<p>Scientists already know of DNA mutations that can show where someone was from. My team created a “GPS” tool for genomes that helped us to <a href="https://theconversation.com/uncovering-ancient-ashkenaz-the-birthplace-of-yiddish-speakers-58355">identify Ancient Ashkenaz</a> as the birthplace of Ashkenazi Jews and the Yiddish language. There are also <a href="https://www.cell.com/cell-reports-methods/fulltext/S2667-2375(22)00147-3">DNA mutations</a> that help tell us how long ago someone lived. </p>
<p>One example is the <a href="https://www.ncbi.nlm.nih.gov/gene/3938">LCT gene mutation</a> that allowed our ancestors to process lactose. It has increased rapidly since it first emerged developed in the <a href="https://warwick.ac.uk/fac/arts/classics/warwickclassicsnetwork/romancoventry/resources/prehistoricbritain/neolithic/#:%7E:text=The%20Neolithic%20period%20lasted%20from,called%20the%20New%20Stone%20Age">Neolithic era</a> (10,000-8,000 BC). So we can date ancient genomes without the LCT gene mutation to before the Neolithic era. </p>
<p>My team developed the temporal population structure (TPS) algorithm tool and used it to date 5,000 ancient and modern genomes. There are tens of thousands of mutations that increased or decreased over time. TPS identifies these mutations and the period they are associated with and classifies them into eight broad periods. </p>
<p>Each ancient person is represented by the signatures of these periods. TPS uses a type of artificial intelligence <a href="https://en.wikipedia.org/wiki/Supervised_learning">known as supervised machine learning</a> to match those signatures to the ages of skeletons. </p>
<p>One way to test a dating method is to compare the age gap of skeletons that are related to each other. This can work well if the skeletons are complete enough to <a href="https://www.nature.com/articles/d41586-019-01247-x">estimate their age</a>. You would expect father and son skeletons, for example, to be dated to a period of about 17 to 35 years apart. </p>
<p>In a blind test, the TPS dated the skeletons of close family members within a sensible time span of 17 years apart, compared with 68 years in a non-blind test for other dating methods. (A blind test is when information that can influence the experimenters is withheld until the experiment is complete.) </p>
<p>One of the most controversial sites for ancient dating is the Czechia Brandýsek burial site. The <a href="https://www.nature.com/articles/nature25738">Brandýsek burials</a> dated to the Bell Beaker period were explored between 1955 and 1956. </p>
<p><a href="https://reich.hms.harvard.edu/allen-ancient-dna-resource-aadr-downloadable-genotypes-present-day-and-ancient-dna-data">Archaeologists uncovered graves</a>, half of which were destroyed by mining operations. They found 23 people from 22 graves alongside artefacts such as pottery, a bone pendant and flint arrowheads. </p>
<p>Based on both radiocarbon and archaeological context, the site was dated to the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973796/">Bell Beaker period</a> (4,800- 3,800 years ago). However, the same study radiocarbon dated one of the skeletons to around (5,500 years ago). </p>
<p>Given that only two corpses could be radiocarbon dated, it was difficult to tell whether the dating was wrong or if this was a site that may have had ritualistic importance for thousands of years. <a href="https://www.sciencedirect.com/science/article/pii/S2667237522001473?via%3Dihub">Our DNA study</a> of 12 skeletons from the site confirmed the questionable skeleton was about 1,000 years older than the others. </p>
<p>Our results confirm that this site has been a burial ground since the Neolithic period. This also explains why the site has architectural features not usually associated with Bell Beaker burials, like stone graves.</p>
<p>While TPS performed well, it is not a substitute for radiocarbon dating. Its accuracy depends on a dataset of ancient DNA. TPS can set dates for human and farm animals, for which extensive ancient data is available. But those who want to travel to the past to meet an ancient elephant or a monkey are on their own.</p><img src="https://counter.theconversation.com/content/189493/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This work was partially supported by the EPSRC Doctoral Training Partnership Grant EP/N509735/1 to U.E. and by the MRC (MR/R025126/1), the Crafoord Foundation, the Swedish Research Council (2020-03485), and the Erik Philip-Sorensen Foundation (G2020-011) awards to E.E. The computations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at Lund, partially funded by the Swedish Research Council through grant agreement no. 2018-05973.</span></em></p>
DNA dating could complement radiocarbon technology to help make archaeology more accurate.
Eran Elhaik, Senior Lecturer in Population, Medical and Evolutionary Genomics, Lund University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/184582
2022-06-22T13:00:08Z
2022-06-22T13:00:08Z
Before chickens became food for people, they were regarded as special exotica
<figure><img src="https://images.theconversation.com/files/468976/original/file-20220615-23-j1gma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A modern cockerel with dramatic plumage</span> <span class="attribution"><a class="source" href="https://robertmay.photography/">Robert May, https://robertmay.photography/</a>, <span class="license">Author provided</span></span></figcaption></figure><p>There are more chickens than any other species of bird on the planet. With three chickens for every <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsos.180325">human being</a>, they are a food staple for millions of people around the world. But new research shows chickens were domesticated only <a href="https://www.pnas.org/doi/10.1073/pnas.2121978119">relatively recently</a> and were once <a href="https://doi.org/10.15184/aqy.2021.90">revered</a>. </p>
<p>The question of where chickens come from and how humans have interacted with them over time has eluded us for decades, <a href="https://www.pnas.org/doi/10.1073/pnas.2121978119">until now</a>. For many people it is difficult to think of chickens as anything other than food. But <a href="https://doi.org/10.15184/aqy.2021.90">two new studies</a> are changing our understanding of human-chicken relationships.</p>
<figure class="align-center ">
<img alt="Blue gloved hands hold up chicken bones" src="https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468961/original/file-20220615-13-32g7sz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ancient and modern samples Photo credit.</span>
<span class="attribution"><span class="source">Jonathan Rees/ Cardiff University</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>One of our new studies <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690?fbclid=IwAR27t8VvixTt9a3U7H0U4AoimHpJqWWsbrIAXL0g7UcAOyMuez1eu5WVaoE">radiocarbon dated</a> bones from 23 of the earliest proposed chickens in <a href="https://doi.org/10.15184/aqy.2021.90">Europe and northwest Africa</a>, to test their age. By confirming which chickens are actually ancient we get a clearer insight into when they arrived in these areas and how people interacted with them. <a href="https://twitter.com/Estalwin/status/1534325838816104450">Only five</a> specimens corresponded with the dates that archaeologists had previously assigned to them. The other 18 were much more recent than previously thought, sometimes by thousands of years. </p>
<p>Earlier hypotheses, which based their dates on contextual clues such as where these bones had been located and what other artefacts they were found with, suggested that chickens were present in Europe up to 7,000 years ago. But <a href="https://doi.org/10.15184/aqy.2021.90">our results</a> show they were not introduced until around 800 BC (2,800 years ago). This reveals that chickens are a rather recent arrival to Europe, compared to domestic cattle, pigs and sheep which reached Britain around 6,000 years ago. The new dating also suggests that in many locations there was a <a href="https://doi.org/10.15184/aqy.2021.90">time-lag</a> of several hundred years from when chickens were first introduced to an area, to them really being thought of as food.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=534&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=534&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=534&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=671&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=671&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470296/original/file-20220622-21-isx7zt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=671&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Calibrated radiocarbon results for each specimen, with previous proposed dates in brackets.</span>
<span class="attribution"><a class="source" href="https://www.cambridge.org/core/journals/antiquity/article/redefining-the-timing-and-circumstances-of-the-chickens-introduction-to-europe-and-northwest-africa/0797DAA570D51D988B0514C37C2EC534">Antiquity</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Many of the <a href="https://doi.org/10.15184/aqy.2021.90">early chickens</a> identified by our radiocarbon dating are complete or almost complete skeletons. In Britain none of the most ancient skeletons show evidence they were butchered for human consumption. They were often <a href="https://onlinelibrary.wiley.com/doi/10.1002/oa.2988">older animals</a>, buried alone in pits. One specimen even had a well-healed leg fracture, indicating human care. She was also still able to lay eggs: she had a substance called medullary bone inside her skeleton which is formed during egg production. </p>
<p>These clues suggest that rather than being considered a source of food, these early arrivals to northern Europe were more likely regarded as <a href="https://www.cardiff.ac.uk/news/view/2628884-chickens-for-life-not-just-for-dinner">special exotica</a>, especially given their small population size at the time. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=259&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=259&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=259&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=325&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=325&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470345/original/file-20220622-19-i2kwtv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=325&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Iron Age hen skeleton from Weston Down, England.</span>
<span class="attribution"><span class="source">Julia Best and Grace Clark</span></span>
</figcaption>
</figure>
<p>In some locations shortly after chickens were introduced, we find them buried with humans. A new survey of British Late Iron Age and Roman <a href="https://doi.org/10.15184/aqy.2021.90">burials that contained chickens</a> indicates these burial rites were often gendered: males were buried with cockerels and females with hens. Chickens may have been included in human graves as “psychopomps”, whose role it was to lead human souls to the afterlife. Such a role would have been in keeping with their association with Mercury (the Roman god of communication and travel). Large quantities of cockerels were sacrificed to Mercury at temples such as Uley, Gloucestershire. In other cases, the chickens in graves were a food offering. This is a practice that became more common in Britain through the Roman period. </p>
<p>It is clear that human-chicken relationships were <a href="https://webarchive.nationalarchives.gov.uk/ukgwa/20210802102845/https://ahrc-blog.com/2020/04/10/the-fable-of-britains-easter-animals/">complex</a> and about more than just food for quite some time, <a href="https://fb.watch/dFLKAB2qkT/">even after</a> they started to venture onto the dinner table.</p>
<p>So where did these special birds first come from? </p>
<h2>From the jungle to the fields</h2>
<p>Recent <a href="https://www.nature.com/articles/s41422-020-0349-y">DNA analyses</a> confirmed chickens were domesticated from a subspecies of red jungle fowl called <em>Gallus gallus spadiceus</em> which lived in south or south-east Asia. This would imply chickens were domesticated within this broad region. </p>
<p>Before now, there were three main hypotheses on location and timing. The first places domestication around 4,000 years ago in the <a href="https://agris.fao.org/agris-search/search.do?recordID=US201300589148">Indus Valley</a>. The second argues it happened in <a href="https://www.sciencedirect.com/science/article/abs/pii/0305440388900805">south-east Asia</a> well over 8,000 years ago. The third sees their origins in <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1411882111">northern China</a> 10,000 years ago. </p>
<p>But these theories fail to take into account crucial factors. These include: dating uncertainties, skeletal similarities between chickens and other local wild species, and the broader cultural and environmental context.</p>
<p>In the second new study our team <a href="https://www.pnas.org/doi/epdf/10.1073/pnas.2121978119">reassessed</a> the identification of the species, the domestic status and the dating of the most ancient reported chicken bones from more than 600 archaeological sites across 89 countries, in four continents. We found all three hypotheses are wrong. The oldest bones now confidently assigned to domestic chickens come from the Neolithic site of Ban Non Wat in central Thailand, and date to around 3,500 years ago – much later than previously thought.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468963/original/file-20220615-26-o4evj0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A rooster retracing the footsteps of its ancestor the red jungle fowl.</span>
<span class="attribution"><span class="source">Nikolas Noonan/ Unsplash.com</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While uncertainty remains about why chickens were domesticated, one thing appears to have drawn chickens and people together: rice. The introduction of dry rice farming in central Thailand coincides with the date of the oldest chicken remains. This suggests the new type of farming may have been a catalyst for the domestication process. </p>
<p>The clearing of the jungle for cereal cultivation would have created a <a href="https://thesiamsociety.org/wp-content/uploads/2020/04/NHBSS_022_1-2n_Collias_EcologyOfTheRedJ.pdf">comfortable environment</a> for the red jungle fowl. Simultaneously, the newly grown rice, along with <a href="https://link.springer.com/article/10.1007/s41826-021-00040-y">millet</a>, would have drawn the wild jungle fowl into close contact with humans, sparking the domestication process, after which their chicken descendants were dispersed across the world with human societies.</p><img src="https://counter.theconversation.com/content/184582/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julia Best was supported by the AHRC (AH/L006979/1 and AH/N004558/1), by the NERC Radiocarbon Facility (NF/2015/2/5). The work was conducted when she was employed by both Cardiff University and Bournemouth University. </span></em></p><p class="fine-print"><em><span>Ophélie Lebrasseur is affiliated with the Centre for Anthropobiology and Genomics of Toulouse, UMR 5288, CNRS/Université Toulouse III Paul Sabatier, Toulouse, France, and the Instituto Nacional de Antropología y Pensamiento Latinoamericano, Ministry of Culture, Buenos Aires, Argentina. She receives funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 895107.
Part of the work was conducted when Ophélie Lebrasseur was employed by the University of Oxford, where she was supported by the Arts and HumanitiesResearch Council (grant AH/L006979/1) (2014-2017) and the European Research Council(ERC) starting grant (ERC-2013-StG-337574-UNDEAD) (2017-2018).</span></em></p>
Why did the chicken cross the globe? A new study has revealed how chickens were domesticated.
Julia Best, Lecturer in archaeology, Cardiff University
Ophélie Lebrasseur, MSCA Research Fellow, Université de Toulouse III – Paul Sabatier
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/168426
2021-09-23T18:00:41Z
2021-09-23T18:00:41Z
Fossil footprints prove humans populated the Americas thousands of years earlier than we thought
<figure><img src="https://images.theconversation.com/files/422440/original/file-20210921-25-kgjgkh.jpeg?ixlib=rb-1.1.0&rect=0%2C274%2C1004%2C507&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Are these the footprints of the first-known American teen?</span> <span class="attribution"><span class="source">Matthew Robert Bennett</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Our species began migrating out of Africa around <a href="https://www.science.org/doi/10.1126/science.1199113">100,000 years ago</a>. Aside from Antarctica, the Americas were the last continents humans reached, with the early pioneers crossing the now-submerged <a href="https://www.nationalgeographic.org/photo/bering-land-bridge/">Bering land bridge</a> that once connected eastern Siberia to North America. </p>
<p>At times throughout the <a href="https://www.britannica.com/science/Pleistocene-Epoch">Pleistocene ice age</a>, which ended 10,000 years ago, large ice sheets covered much of Europe and North America. The water locked in these ice sheets lowered the sea level, allowing people to walk the bridge from Asia through the Arctic to Alaska. But during the peak of the last glacial cycle, their path south into the Americas was blocked by a continental-wide ice sheet.</p>
<p>Until now, scientists believed humans only travelled south into the Americas when this ice barrier began to melt – at the earliest, <a href="https://www.nature.com/articles/485030a">16,500 years ago</a>. But together with our colleagues, we have <a href="https://www.science.org/doi/10.1126/science.abg7586">discovered</a> a set of fossil footprints that suggest humans first set foot on the continent thousands of years earlier.</p>
<figure class="align-right ">
<img alt="two fossil footprints" src="https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=990&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=990&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=990&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1244&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1244&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422441/original/file-20210921-25-14vvp7y.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1244&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 fossil footprints.</span>
<span class="attribution"><span class="source">Matthew Robert Bennett</span>, <span class="license">Author provided</span></span>
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<p>These footprints, unearthed at White Sands National Park in New Mexico, were made by a group of teenagers, children and the occasional adult, and have been dated to the height of the last glacial maximum, some 23,000 years ago. That makes them potentially the oldest evidence of our species in the Americas. </p>
<p>Our findings support the idea that humans were present in the southern part of North America before the last glacial peak – a theory that has so far been based on disputed and potentially unreliable evidence.</p>
<h2>Step change</h2>
<p>There are literally tens of thousands of fossil footprints at White Sands. Together, they tell <a href="https://theconversation.com/fossil-footprints-the-fascinating-story-behind-the-longest-known-prehistoric-journey-147520">stories</a> of how prehistoric humans interacted with extinct Ice Age megafauna, such as Columbian mammoths and <a href="https://theconversation.com/how-to-hunt-a-giant-sloth-according-to-ancient-human-footprints-95344">giant ground sloths</a>. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-hunt-a-giant-sloth-according-to-ancient-human-footprints-95344">How to hunt a giant sloth – according to ancient human footprints</a>
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<p>The tracks were deposited around the margins of a large wetland – perhaps a lake after the rainy season, but at other times more like a patchwork of water bodies. Until now, the problem had been dating these footprints. We knew they were imprinted before the megafauna became extinct, but not precisely when. </p>
<p>This changed in September 2019 when the team found tracks with undisturbed sediment above and below them. Within that sediment were layers containing hundreds of seeds of the common ditch grass <em>Ruppia cirrhosa</em>. These seeds, when radiocarbon dated, would reveal the age of the footprints themselves. Analysis revealed the seeds range in age from 21,000 to 23,000 years old, suggesting humans made repeated visits to the site over at least two millennia.</p>
<figure class="align-center ">
<img alt="Some dark brown seeds" src="https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422443/original/file-20210921-15-169uoe8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&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">Some of the seeds that we extracted from the footprints.</span>
<span class="attribution"><span class="source">Matthew Robert Bennett</span>, <span class="license">Author provided</span></span>
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<p>The White Sands footprints provide unequivocal evidence that people were in the Americas at the height of the last glacial maximum, rather than some time after, as was previously thought. That’s a big deal for our understanding of the peopling of the Americas and the genetic composition of indigenous Americans. </p>
<p>Using the DNA of modern indigenous Americans, scientists have worked out that their ancestors arrived from Asia in several waves, some of which became genetically isolated. The cause of this isolation is not clear. Now, our new footprint evidence provides an explanation, suggesting that the earliest Americans were isolated south of the North American ice sheet, only to be joined by others when that sheet melted.</p>
<p>Our discovery may also reopen speculation about other archaeological sites in the Americas. One of them is <a href="https://doi.org/10.1038/s41586-020-2509-0">Chiquihuite Cave</a> in Mexico. Archaeologists recently claimed that evidence from this cave suggests humans occupied the Americas around 30,000 years ago – 7,000 years before people left the White Sands footprints.</p>
<p>But the Chiquihuite Cave findings are disputed by some, as stone tools can be difficult to interpret and tool-like stones can form via natural processes. Stone tools can also move between layers of sediment and rock. Fossil footprints can’t. They are fixed on a bedding plane, and so provide more reliable evidence of exactly when humans left them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="modern footprints bordering ancient ones." src="https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422447/original/file-20210921-23-1uj9b7l.jpeg?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">On the left, modern shoeprints; on the right, footprints millennia old.</span>
<span class="attribution"><span class="source">Matthew Robert Bennett</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Teenage kicks</h2>
<p>We tend to picture our ancestors engaged in life-or-death struggles – forced to battle the elements simply to survive. Yet the White Sands evidence is suggestive of a playful, relatively relaxed setting, with teenagers and children spending time together in a group.</p>
<p>This is perhaps not that surprising. Children and teenagers are more energetic and playful than adults and therefore leave more traces. Adults tend to be more economical in their movement, leaving fewer tracks. </p>
<figure class="align-center ">
<img alt="An illustration of prehistoric man and mammoths" src="https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=297&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=297&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=297&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=373&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=373&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422602/original/file-20210922-16-fhamca.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=373&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">What White Sands might have looked like 23,000 years ago.</span>
<span class="attribution"><a class="source" href="http://www.davidebonadonna.it/">Davide Bonadonna</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But another interpretation of this new footprint evidence is that the teenagers were part of the workforce in these early bands of hunter-gatherers. It’s possible that the tracks were left by young people fetching and carrying resources for their prehistoric parents.</p>
<p>In any case, the people that left their tracks on White Sands were some of the earliest known American teens. Set in stone, their footprints pay tribute to their forebears, who we now know walked the long land bridge into the Americas millennia earlier than what was commonly believed.</p><img src="https://counter.theconversation.com/content/168426/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>
The New Mexico findings could rewrite the history of human migration to the Americas.
Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth University
Sally Christine Reynolds, Principal Academic in Hominin Palaeoecology, Bournemouth University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/162084
2021-06-28T04:31:28Z
2021-06-28T04:31:28Z
Breakthrough allows scientists to determine the age of endangered native fish using DNA
<figure><img src="https://images.theconversation.com/files/408568/original/file-20210628-13-xaemas.jpg?ixlib=rb-1.1.0&rect=0%2C479%2C3982%2C2179&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Identifying the age of animals is fundamental to wildlife management. It helps scientists know if a species is at risk of extinction and the rate at which it reproduces, as well as determining what level of fishing is sustainable. </p>
<p>Determining the age of fish has been difficult in the past — primarily involving extracting the inner ear bone, also known as the “otolith”. Layers of growth in the otolith are counted like rings on a tree to reveal an individual’s age. Unless a dead specimen is available, this method requires killing a fish, making it unsuitable for use on endangered populations. </p>
<p>However a non-lethal DNA test developed by the CSIRO enables researchers to determine fish age for three iconic and threatened Australian freshwater species: the Australian lungfish, the Murray cod and the Mary River cod. We outline the technological breakthrough in our <a href="https://onlinelibrary.wiley.com/doi/10.1111/1755-0998.13440">research</a> just published.</p>
<p>Our fast, accurate and cost-effective test can be adapted for other fish species. We now hope to share this method to improve the protection of wild fish populations and help promote sustainable fisheries around the world.</p>
<figure class="align-center ">
<img alt="gloved hands cut open fish with sciessors" src="https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408566/original/file-20210628-25-1n3i312.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&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">Traditionally, age could only be determined on a dead fish. The new method is non-lethal.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>Iconic species at risk</h2>
<p>Human activity has led to the population declines of the three Australian fish species at the centre of our research.</p>
<p>The threatened Australian lungfish is found in rivers and lakes in southeast Queensland. It’s often referred to as a “living fossil” because its extraordinary evolutionary history stretches back more than 100 million years, before all land animals including dinosaurs. </p>
<p>Man-made barriers in rivers reduce the movement of water, which lowers lungfish breeding rates. </p>
<p>Older lungfish do not have hard otolith structures, which makes determining their age difficult. Bomb radiocarbon, which analyses carbon levels in organic matter, has been used to age Australian lungfish, but this method is too expensive to be widely used. </p>
<figure class="align-center ">
<img alt="Australian lungfish" src="https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/405400/original/file-20210609-14804-dxzlxf.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">In the past, determining the age of Australian lungfish has been challenging.</span>
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<p>The threatened <a href="https://www.mdba.gov.au/sites/default/files/archived/mdbc-NFS-reports/2202_factsheet_native_murray_cod.pdf">Murray cod</a> is Australia’s largest freshwater fish. The <a href="https://www.environment.gov.au/biodiversity/threatened/recovery-plans/mary-river-cod-research-and-recovery-plan-1996">Mary River cod</a> is one of Australia’s most endangered fish, found in less than 30% of its former range in Queensland’s Mary River. </p>
<p>Habitat destruction and overfishing are major threats to Murray cod and Mary River cod populations.</p>
<p>Otoliths can be used to determine age for both these cod species, however this has only been done on a population-wide scale for the more prevalent Murray cod. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-smallest-fish-among-22-at-risk-of-extinction-within-two-decades-144115">Australia's smallest fish among 22 at risk of extinction within two decades</a>
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<figure class="align-right ">
<img alt="Mary River cod" src="https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/405403/original/file-20210609-14622-b8aqvx.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">CSIRO estimated the age of Mary River cod.</span>
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<h2>Our DNA breakthrough</h2>
<p>When cells divide to make new cells, DNA is replicated. This can lead to DNA methylation, which involves the addition or the loss of a “methyl group” molecule at places along the DNA strand. </p>
<p>Research has found the level of DNA methylation is a reliable predictor of age, particularly in mammals, <a href="https://genomebiology.biomedcentral.com/articles/10.1186/gb-2013-14-10-r115">including humans</a>. </p>
<p>To develop our test, we first worked with zebrafish. This species is useful when studying fish biology because it has a short lifespan and high reproductive rates. We took zebrafish whose ages were known, then removed a tiny clip of their fin. We then examined DNA methylation levels in the fin sample to identify the fish’s age. </p>
<p>Following this successful step, we transferred the method to Australian lungfish, Murray cod and Mary River cod. Again, we used fish of known ages, as well as bomb radiocarbon dating of scales and ages determined from otoliths.</p>
<p>We found despite the zebrafish and the study fish species being separated by millions of years of evolution, our method worked in all four species. This suggests the test can be used to predict age in many other fish species.</p>
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<p>
<em>
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Read more:
<a href="https://theconversation.com/good-news-from-the-river-murray-these-2-fish-species-have-bounced-back-from-the-millennium-drought-in-record-numbers-148433">Good news from the River Murray: these 2 fish species have bounced back from the Millennium Drought in record numbers</a>
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<hr>
<figure class="align-center ">
<img alt="DNA strand" src="https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=303&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=303&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=303&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=381&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=381&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408567/original/file-20210628-17-h2rxxj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=381&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The test uses co-called DNA methylation to estimate age.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A conservation management boom?</h2>
<p>In the same way human population demographers use census data to understand and model human populations, we now have the tools to do this with animals. </p>
<p>We are looking to expand this DNA-based method to determine the age of the endangered eastern freshwater cod and trout cod. We will also continue to test the method across other species including reptiles and crustaceans. </p>
<p>This work is part of CSIRO’s ongoing efforts to use DNA to measure and monitor the environment. This includes estimating the lifespan of vertebrate species such as long-lived fish and surveying biodiversity in seawater using DNA extracted from the environment.</p>
<p>We envisage that in the not too distant future, these methods may be used by other researchers to better understand and manage wild animal populations. </p>
<p><em><a href="https://onlinelibrary.wiley.com/doi/10.1111/1755-0998.13440">The paper</a> upon which this article was based was published in Molecular Ecology Resources with authors from CSIRO, Seqwater, Queensland Government, NSW Department of Primary Industries, University of Queensland and University of Western Australia.</em></p><img src="https://counter.theconversation.com/content/162084/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Benjamin Mayne 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>
Determining the age of fish has been historically difficult, primarily involving lethal methods. A new DNA test solves this problem.
Benjamin Mayne, Molecular biologist and bioinformatician, CSIRO
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/155390
2021-03-05T17:40:44Z
2021-03-05T17:40:44Z
St James, ‘brother’ of Jesus: it turns out his ancient remains belong to someone else
<figure><img src="https://images.theconversation.com/files/387995/original/file-20210305-23-hkz2ie.jpg?ixlib=rb-1.1.0&rect=113%2C5%2C1077%2C585&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Saint James the Lesser is believed to have been martyred in AD 70.</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/James_the_Less#/media/File:Saint_James_the_Less_(Menologion_of_Basil_II).jpg">Wikicommons</a></span></figcaption></figure><p>Hunched innocuously in the shadow of Rome’s mighty Piazza Venezia, just a stone’s throw from one of the city’s busiest thoroughfares, the Santi Apostoli church might be forgiven for having more respect for the dead than for the living.</p>
<p>That’s because of the treasures that the church protects. As well as having briefly accommodated the tomb of Michelangelo, the church has, since the year 556, housed relics of particular significance to the Holy Catholic Church: the remains of two of Jesus’ contemporaries, Saint Philip and Saint James, the latter of whom is believed to have been Jesus’ brother. </p>
<p>Now, after <a href="https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-021-00481-9">careful extraction and analysis</a>, a bone said to have belonged to Saint James has been radiocarbon-dated – and sadly de-authenticated. Despite being incredibly old, having died at some time between 214 and 340, the individual housed in the Santi Apostoli church for one and a half millennia turns out to have been a few generations off the real deal.</p>
<p>Yet the surprise finding that the wrong person’s remains were likely transported to Rome from the Middle East has prised open a fascinating history: of plundered tombs, holy men’s bones, and the remarkable relocation of saints from one ancient empire to another. </p>
<h2>Moving tombs</h2>
<p>In ancient Rome, families commemorated the birthdays of their ancestors by taking festive meals at their graves. This custom was <a href="https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780198747871.001.0001/oxfordhb-9780198747871">later taken up</a> by early Christians, who came together around the tombs of their saints on their name days.</p>
<p>But there was a problem. As Christianity became more dominant, the tombs of saints became overcrowded. Plus, the tombs were often situated outside the city walls, which made the feasts potentially risky. In an effort to make them safer and more accessible, saints’ remains were exhumed and transferred into churches in a process called translation.</p>
<figure class="align-center ">
<img alt="A coffin is carried into a city in a painting" src="https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/387845/original/file-20210304-13-10s9623.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 translation of saints’ remains into churches became increasingly common in the fourth century.</span>
</figcaption>
</figure>
<p>The practice of translation began in modern-day Turkey. The first known translation was of <a href="https://www.springer.com/gp/book/9783322980229">Saint Babylas in AD 354</a>, who was moved from a cemetery outside the ancient city of Antioch (near the modern-day Turkish city of Antakya) to a purpose-built Byzantine church. There followed a boom in exhumations: Saint Timotheus, Saint Andre and Saint Lukas were all translated to churches in Constantinople (modern-day Istanbul) the following year. </p>
<p>At its peak, the translation trend saw the Christian church <a href="https://www.fourthcentury.com/imperial-laws-364/">issue edicts</a> calling for order amid the energetic violation of sacred tombs. During this period, dozens of bodies were finding their way, by sea and on foot, from tombs into church crypts. The flow of saintly bones was eventually directed from the Middle East, where the saints had died, towards the centre of Rome: the seat of the Roman Catholic church.</p>
<h2>Skeletal relics</h2>
<p>The remains of Saint Philip and Saint James were assumed to have been caught up in this frenzy of translation. Unsurprisingly, their skeletons are far from complete today. Only fragments of a tibia, a femur and a mummified foot remain. </p>
<p>The tibia and foot are attributed to Saint Philip, who was one of the original twelve apostles, and was said to have been present at the miraculous <a href="https://www.biblegateway.com/passage/?search=John%206%3A5-14&version=NIV">feeding of the 5,000</a>.</p>
<p>The femur, meanwhile, was said to belong to Saint James, an altogether more ambiguous figure. Saint Paul calls him “the pillar” of the first Christian church in Jerusalem. This position led to his death, claims the historian Josephus, after the Jewish high priest Ananus <a href="https://lexundria.com/j_aj/20.200/wst%20Antiquities%20of%20the%20Jews,%2020.200">had James stoned to death</a> in AD 70.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An old religious painting of a man hitting another man with a stick" src="https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=523&fit=crop&dpr=1 754w, https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=523&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/387840/original/file-20210304-15-l58hj8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=523&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 manuscript dating from late tenth or early eleventh century depicts the martyrdom of Saint James in Jerusalem.</span>
</figcaption>
</figure>
<p>Paul also describes James as the “Lord’s brother”, something that seems to directly contradict Catholic dogma regarding Mary’s lifelong virginity. This has nonetheless led to speculation that James was either Jesus’ cousin, his half-brother, or <a href="https://www.bloomsbury.com/uk/jude-and-the-relatives-of-jesus-in-the-early-church-9780567082978/">even his brother</a>.</p>
<h2>Feat of chemistry</h2>
<p>To authenticate the bones stored in the Santi Apostoli church, our research team needed to work out when the individuals died. That involved peeling back the layers of history that had accumulated on the bones over the course of their long and well-travelled past.</p>
<p>Doing so, we found mercury embedded deep within the pores and cracks of the bone: a common sign of past mummification. There was evidence of sporadic embalming over the centuries, too. We even found insecticide on the relics, which we dated to the 1950s.</p>
<p>During this process it became clear that only the femur was substantial enough to be radiocarbon dated. But we still couldn’t use its collagen in an Accelerator Mass Spectrometer, as we usually would, because we couldn’t be sure that all the contamination was removed from the sample. </p>
<p>Instead, we had a single amino acid within the collagen, called hydroxyproline, isolated and dated <a href="https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/full/10.1002/rcm.8047">using equipment</a> at the University of Oxford. The unequivocal result was that the individual died sometime between 214 and 340, so the femur could not have belonged to Saint James. It originates from another person some 160 to 240 years younger.</p>
<figure class="align-center ">
<img alt="A ring of bone, hollow in the middle" src="https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/388033/original/file-20210305-15-1xh0jxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A cross-section of the femur attributed to Saint James.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Beyond the grave</h2>
<p>Our international research team also decided to radiocarbon-date some rapeseed oil, which we found, during excavation, at the very bottom of the original altar. The oil dated from between 267 and 539.</p>
<p>As the Santi Apostoli church was likely erected around 556, this oil is older than the church itself and could possibly have followed the relics on their translation from the Middle East to the yet-unbuilt church. </p>
<p>So, we can be sure that the long-protected femur did not belong to Saint James. But our findings have cast an unprecedented flicker of light into the dark period between the death of the apostles around AD 100, and the subsequent storing of Christian relics, centuries later, in the heart of Rome.</p><img src="https://counter.theconversation.com/content/155390/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>
The mix-up might be explained by the rush to remove sacred remains to Rome some 1,700 years ago.
Kaare Lund Rasmussen, Professor of Archaeometry, University of Southern Denmark
Lautaro Roig Lanzillotta, Professor of New Testament and Early Christian Studies, University of Groningen
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/130669
2020-09-29T12:31:30Z
2020-09-29T12:31:30Z
Archaeologists determined the step-by-step path taken by the first people to settle the Caribbean islands
<figure><img src="https://images.theconversation.com/files/360064/original/file-20200925-22-vgu7h0.jpg?ixlib=rb-1.1.0&rect=300%2C84%2C4533%2C3076&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What route did the first settlers to colonize the islands of the Caribbean take?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/caribbean-royalty-free-image/132280669">M.M. Swee/Moment via Getty Images</a></span></figcaption></figure><p>For the millions of people around the world who live on islands today, a plane or boat can easily enough carry them to the mainland or other islands.</p>
<p>But how did people in the ancient past first make it to distant islands they couldn’t even see from home? Many islands around the world can be reached only by traveling hundreds or even thousands of miles across open water, yet nearly all islands that people live on were settled by between 800 to 1,000 years ago.</p>
<p><a href="https://scholar.google.com/citations?user=cVLYtvoAAAAJ&hl=en&oi=ao">Archaeologists</a> <a href="https://scholar.google.com/citations?user=o60SujYAAAAJ&hl=en&oi=ao">like</a> <a href="https://scholar.google.com/citations?user=tTV6YEoAAAAJ&hl=en&oi=ao">us</a> <a href="https://scholar.google.com/citations?hl=en&user=ZMMqNV4AAAAJ">want</a> to understand why people would risk their lives to reach these far-off places, what kinds of boat and navigational methods they used, and what other technologies they invented to make it. Islands are important places to study because they hold clues about human endurance and survival in different kinds of environments.</p>
<p>One of the most interesting places to study these processes is the Caribbean, the only region of the Americas where people settled an archipelago with some islands not visible from surrounding areas. Despite more than a century of research, there are still many questions about the origins of the first Caribbean people, when they migrated and what routes they took. My colleagues and I recently reanalyzed archaeological data collected over 60 years to answer these fundamental questions.</p>
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<h2>Settling the islands one by one</h2>
<p>Based on the discovery of unique stone tools and food remains such as shells and bones, archaeologists have a general understanding that <a href="https://doi.org/10.1179/2055557115Y.0000000010">people first spread throughout the Caribbean</a> in a series of migrations that probably began at least 7,000 years ago and likely originated from northern South America.</p>
<p><a href="http://www.uapress.ua.edu/product/On-Land-and-Sea,1478.aspx">Amerindians paddled between islands</a> in dugout canoes and were remarkably adept at open-water travel. Archaeologists don’t know what inspired people to first colonize the Caribbean islands, but we do know they brought plants and animals from the mainland, like manioc and oppossum, to help ensure their survival. </p>
<p>There are two main ideas about what happened. For decades, the prevailing notion was that people migrated from South America into the Antilles in a south-to-north “stepping-stone” pattern. Because the islands stretch in a gentle arc from Grenada all the way up to Cuba in the northwest – <a href="http://www.uapress.ua.edu/product/Archaeology-and-Geoinformatics,114.aspx">with many largely visible from one to the next</a> – this would seem to provide a convenient path for early settlers.</p>
<p>This hypothesis, however, has been challenged by evidence that <a href="https://doi.org/10.1086/320012">some of the earliest sites are in the northern islands</a>. Analyses of wind and ocean currents suggest that it was actually easier to travel directly between South America and the northern Caribbean before moving in a southerly direction. Researchers call this proposal of a north-to-south migration the “southward route” hypothesis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="archeologists excavating with the sea in the background" src="https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358882/original/file-20200918-14-1487jzo.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">For decades, archaeologists have been excavating artifacts on these islands.</span>
<span class="attribution"><span class="source">Scott Fitzpatrick</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Revisiting previous scientists’ date data</h2>
<p>Figuring out which model for settling the Caribbean best fits the evidence depends on being able to assign accurate dates to human activity preserved in the archaeological record. To do this, researchers need a lot of reliable dates from many different sites throughout the islands to establish how, when and from where people landed.</p>
<p>Archaeologists typically use <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">a technique called radiocarbon dating</a> to figure out how old an artifact is. When an organism dies, it stops producing carbon and its remaining carbon decays at a fixed rate of time – archaeologists say “death starts the clock.” By measuring the amount of carbon left in the organism and then performing a few additional calculations, scientists are left with a probable age range for when that organism died.</p>
<p>Archaeologists often date things like food remains, charcoal from cooking hearths or wood in the building where they are found. If archaeologists date shells found in a trash heap, they can tell, usually within a range of 25 to 50 years or so, when that shellfish was harvested for a meal.</p>
<p>We recently <a href="https://doi.org/10.1126/sciadv.aar7806">reevaluated about 2,500 radiocarbon dates</a> from hundreds of archaeological sites on more than 50 Caribbean islands. </p>
<p>Archaeologists have been radiocarbon dating findings in the Caribbean since the 1950s – when the radiocarbon technique was first discovered. But dating methods and the standards scientists follow have improved dramatically since then. Part of our job was to see if each of the 2,500 radiocarbon dates available would meet today’s standards. Dates that did not meet those standards were thrown out, leaving us with a smaller database of only the most reliable times for human activity.</p>
<h2>Determining where people lived first</h2>
<p>By statistically analyzing these remaining dates, we confirmed that Trinidad was the first Caribbean island settled by humans, at least 7,000 years ago. However, Trinidad is so close to South America that only simple – or even no – boats were needed to get there.</p>
<p>After Trinidad, the oldest settlements occurred between 6,000 and 5,000 years ago in the northern Caribbean on the large islands of the Greater Antilles: Cuba, Puerto Rico and Hispaniola. Reaching them would have required crossing passages of water where no islands were visible to the naked eye, although navigators rely on other wayfinding techniques – like current, cloud patterns, seeing birds fly in a certain direction – to know if land is out there. By around 2,500 years ago, people had spread out to settle other islands in the northern Lesser Antilles, including Antigua and Barbuda.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map of Caribbean showing order in which islands were settled, from north to south" src="https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358878/original/file-20200918-14-619act.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Thousands of years after Trinidad, Cuba, Puerto Rico and Hispaniola were settled, colonists reached islands in the northern Antilles, bypassing islands in the southern Lesser Antilles, depicted with green SRH arrows for ‘southern route hypothesis.’ The stepping-stone model, depicted with SS arrow, is refuted by the new analysis.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1126/sciadv.aar7806">'Reevaluating human colonization of the Caribbean using chronometric hygiene and Bayesian modeling,' M. F. Napolitano et al, Science Advances, Dec. 18, 2019</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Based on these data, the patterns of initial settlement of the Caribbean are most consistent with the southward route hypothesis. </p>
<p>Around 1,800 years ago, a new wave of people also moved from South America into the Lesser Antilles, colonizing many of the remaining uninhabited islands. About 1,000 years later, their descendants moved into the smaller islands of the Greater Antilles and Bahamian archipelago. This is when Jamaica and the Bahamas were settled for the first time.</p>
<p>Our research findings also support the widely held view that environment played a significant role in how and when islands were settled.</p>
<p>Archaeologists know that once people settled islands, they frequently moved between them. Not all islands are the same, and some offered more or better resources than others. For example, in the Bahamas and the Grenadines, the primary <a href="https://doi.org/10.1353/crb.2012.0030">way to access freshwater</a> is by digging wells; there are no streams or springs. Some islands <a href="https://doi.org/10.1016/j.jasrep.2016.08.033">lacked clay for making pottery</a>, which was important for cooking and storing food. People may have also traveled to different islands to access preferred fishing or hunting spots or seek out marriage partners.</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>Strong seasonal winds and currents facilitated travel between islands. That’s also probably one of the reasons why Caribbean people never developed the sail or other seafaring technologies that were used in the Pacific, Mediterranean and North Atlantic around the same time. Dugout canoes crossed between South America and the islands just fine.</p>
<p>Interpretations of past human behavior at archaeological sites are anchored by radiocarbon dates to study change over time. For archaeologists, it’s important to periodically take another look at the data to make sure that the narratives built on those data are reliable. Our review of the radiocarbon record for the Caribbean allowed us to show – with increased accuracy – the ways in which the region was first colonized by people, how they interacted and moved between islands, and how their societies developed following initial colonization.</p><img src="https://counter.theconversation.com/content/130669/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew F Napolitano is a PhD Candidate at the University of Oregon. </span></em></p><p class="fine-print"><em><span>Jessica Stone is an affiliated researcher with the Department of Anthropology at the University of Oregon.</span></em></p><p class="fine-print"><em><span>Robert DiNapoli is a Postdoctoral Research Associate in Harpur College at Binghamton University and an affiliated researcher with the Department of Anthropology at the University of Oregon.</span></em></p><p class="fine-print"><em><span>Scott Fitzpatrick is a Professor of Archaeology and Associate Director of the Museum of Natural and Cultural History at the University of Oregon.</span></em></p>
Did people settle these islands by traveling north from South America, or in the other direction? Reanalyzing data from artifacts discovered decades ago provides a definitive answer.
Matthew F. Napolitano, Ph.D. Candidate in Archaeology, University of Oregon
Jessica Stone, Affiliated Researcher in the Department of Anthropology, University of Oregon
Robert DiNapoli, Postdoctoral Research Associate in Archaeology, Binghamton University, State University of New York
Scott Fitzpatrick, Professor of Anthropology + Associate Director, Museum of Natural and Cultural History, University of Oregon
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/143620
2020-08-12T20:13:03Z
2020-08-12T20:13:03Z
From cave art to climate chaos: how a new carbon dating timeline is changing our view of history
<figure><img src="https://images.theconversation.com/files/352428/original/file-20200812-23-cpm0hy.jpg?ixlib=rb-1.1.0&rect=150%2C110%2C6559%2C4355&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Geological and archaeological records offer important insights into what seems to be an increasingly uncertain future. </p>
<p>The better we understand what conditions Earth has already experienced, the better we can predict (and potentially prevent) future threats. </p>
<p>But to do this effectively, we need an accurate way to date what happened in the past. </p>
<p>Our research, published today in the journal <a href="https://www.cambridge.org/core/journals/radiocarbon/calibrations/intcal-20">Radiocarbon</a>, offers a way to do just that, through an updated method of calibrating the <a href="https://c14.arch.ox.ac.uk/dating.html">radiocarbon timescale</a>.</p>
<h2>An amazing tool for perusing the past</h2>
<p>Radiocarbon dating has revolutionised our understanding of the past. It is nearly 80 years since Nobel Prize-winning US chemist Willard Libby <a href="https://www.nature.com/articles/d41586-019-01895-z">first suggested</a> minute amounts of a radioactive form of carbon are created in the upper atmosphere. </p>
<p>Libby correctly argued this newly formed radiocarbon (or C-14) rapidly converts to carbon dioxide, is taken up by plants during photosynthesis, and from there travels up through the food chain. </p>
<p>When organisms interact with their environment while alive, they have the same proportion of C-14 as their environment. Once they die they stop taking in new carbon.</p>
<p>Their level of C-14 then halves every 5,730 years due to <a href="https://www.esrl.noaa.gov/gmd/ccgg/isotopes/decay.html">radioactive decay</a>. An organism that died yesterday will still have a high level of C-14, whereas one that died <a href="https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/radiocarbon-dating.html">tens of thousands of years ago will not</a>. </p>
<p>By measuring the level of C-14 in a specimen, we can deduce how long ago that organism died. Currently, with <a href="https://www.nature.com/articles/d41586-019-01895-z">this method</a>, we can date remains up to 60,000 years old.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">Explainer: what is radiocarbon dating and how does it work?</a>
</strong>
</em>
</p>
<hr>
<h2>A seven-year effort</h2>
<p>If the level of C-14 in the atmosphere had always been constant, radiocarbon dating would be straightforward. But it hasn’t.</p>
<p>Changes in the <a href="https://wserv4.esc.cam.ac.uk/pastclimate/?page_id=19">carbon cycle</a>, impinging <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/cosmic-radiation">cosmic radiation</a>, the <a href="https://www.pnas.org/content/112/31/9542">use of fossil fuels</a> and <a href="https://theconversation.com/anthropocene-began-in-1965-according-to-signs-left-in-the-worlds-loneliest-tree-91993">20th century nuclear testing</a> have all caused large variations over time. Thus, all radiocarbon dates need to be adjusted (or calibrated) to be turned into accurate calendar ages.</p>
<p>Without this adjustment, dates could be out by up to 10-15%. <a href="https://www.cambridge.org/core/journals/radiocarbon/calibrations">This week we report</a> a seven-year international effort to recalculate three radiocarbon calibration curves: </p>
<ul>
<li>IntCal20 (“20” to signify this year) for objects from the northern hemisphere</li>
<li>SHCal20 for samples from the ocean-dominated southern hemisphere</li>
<li>Marine20 for samples from the world’s oceans.</li>
</ul>
<figure class="align-right ">
<img alt="Close-up of bristlecone pine tree rings." src="https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352243/original/file-20200811-20-1ciaghc.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">We dated bristlecone pine tree rings from the second millennium BC.</span>
<span class="attribution"><span class="source">P. Brewer/Uni of Arizona</span></span>
</figcaption>
</figure>
<p>We constructed these updated curves by measuring a plethora of materials that record past radiocarbon levels, but which can also be dated by other methods. </p>
<p>Included in the archives are tree rings from ancient logs preserved in wetlands, cave stalagmites, corals from the continental shelf and sediments drilled from lake and ocean beds. </p>
<figure class="align-center ">
<img alt="An ancient New Zealand kauri tree log." src="https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351532/original/file-20200806-24-1vpdpwj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ancient New Zealand kauri (<em>Agathis australis</em>) logs like this example were used to help construct the calibration curves. This tree is about 40,000 years old and was found buried underground.</span>
<span class="attribution"><span class="source">Nelson Parker</span></span>
</figcaption>
</figure>
<p>In total, the new curves are based on almost 15,000 radiocarbon measurements taken from objects up to 60,000 years old.</p>
<p>Advances in radiocarbon measurement using <a href="https://en.wikipedia.org/wiki/Accelerator_mass_spectrometry">accelerator mass spectrometry</a> mean the updated curves can use very small samples, such as single tree rings from just one year’s growth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up of an ancient stalagmite." src="https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=177&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=177&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=177&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=223&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=223&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352423/original/file-20200812-20-685xzm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=223&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stalagmites from inside the Hulu Cave in China were key to estimating the amount of radiocarbon present in objects between 14,000 and 55,000 years old.</span>
<span class="attribution"><span class="source">Hai Cheng</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Reassessing old beliefs</h2>
<p>The new radiocarbon calibration curves provide previously impossible precision and detail. As a result, they greatly improve our understanding of how Earth has evolved and how these changes impacted its inhabitants.</p>
<p>One example is the rate of environmental change at the end of the most recent ice age. As the world started to warm some 18,000 years ago, vast ice sheets covering Antarctica, North America (including Greenland) and Europe melted – returning huge volumes of fresh water to the oceans.</p>
<p>But the sea level didn’t rise at a consistent rate like the global temperature. Sometimes it was gradual and other times extremely rapid.</p>
<p>A prime location to detect past sea levels is the <a href="https://www.britannica.com/place/Sunda-Shelf">Sunda Shelf</a>, a large platform of land that was once part of continental Southeast Asia.</p>
<p><a href="https://science.sciencemag.org/content/288/5468/1033.full">One study</a> published in 2000 showed mangrove plant remains found on the seabed recorded a catastrophic 16-metre sea level rise over several hundred years (about half a metre each decade). This event, known as <a href="https://www.giss.nasa.gov/research/briefs/gornitz_10/">Meltwater Pulse-1A</a>, flooded the Sunda Shelf. </p>
<p>Our latest work has modified this story considerably. The new calibration curves reveal this extreme phase of sea level rise actually began 14,640 years ago and lasted just 160 years. </p>
<p>This equates to a staggering one-metre rise each decade – a sobering lesson for the future, considering the current much lower <a href="https://www.theguardian.com/environment/2020/may/08/sea-levels-could-rise-more-than-a-metre-by-2100-experts-say">projected changes for the end of this century</a>. </p>
<h2>An extra half a millennium of art</h2>
<p>Going further back in time, we also looked at some of the world’s oldest cave art in France’s <a href="https://archeologie.culture.fr/chauvet/en">Chauvet Cave</a>, first discovered in 1994. </p>
<p>This cave contains hundreds of beautifully preserved paintings. They depict a European menagerie with long-extinct mammoths, cave lions and woolly rhinoceroses, captured in real-life scenes that provide a window into a lost world.</p>
<p>The Chauvet Cave reveals the artistic sophistication of our <a href="http://www.bradshawfoundation.com/chauvet/index.php">early ancestors</a> in phenomenal detail.</p>
<figure class="align-center ">
<img alt="Chauvet cave paintings depicting wild animals including horses." src="https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351623/original/file-20200806-20-11fv1gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=747&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Chauvet Cave contains hundreds of cave paintings created more than 30,000 years ago.</span>
<span class="attribution"><span class="source">Thomas T/flickr</span></span>
</figcaption>
</figure>
<p>With the new IntCal20 curve, our best estimate for the creation of the oldest radiocarbon-dated painting in the cave is now 36,500 years ago. This is almost 450 years older than previously thought.</p>
<p>These are just two of many more examples of the far-reaching impact our latest work will have. </p>
<p>As <a href="https://www.cambridge.org/core/journals/radiocarbon/calibrations">the new calibration curves</a> are used to re-analyse ages of a host of archaeological and geological records, we can expect major shifts in our understanding of the planet’s past – and hopefully, a better forecast into its future. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-that-rock-hashtag-really-the-first-evidence-of-neanderthal-art-31238">Is that rock hashtag really the first evidence of Neanderthal art?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/143620/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Turney receives funding from The Australian Research Council and is a scientific advisor to cleantech graphite company, CarbonScape (<a href="https://www.carbonscape.com">https://www.carbonscape.com</a>).</span></em></p><p class="fine-print"><em><span>Alan Hogg receives funding from the Marsden fund administered by the Royal Society of New Zealand. </span></em></p><p class="fine-print"><em><span>Paula J. Reimer receives funding from the Leverhulme Trust and UK Research and Innovation. </span></em></p><p class="fine-print"><em><span>Tim Heaton receives funding from the Leverhulme Trust via a research fellowship on "Improving the Measurement of Time via Radiocarbon". </span></em></p>
The updated methods are providing a clearer picture of how Earth and its inhabitants evolved over the past 60,000 years - and thus, providing new insight into its future.
Christian Turney, Professor, Earth Science and Climate Change, UNSW Sydney
Alan Hogg, Professor, Director, Carbon Dating Laboratory, University of Waikato
Paula J. Reimer, Chair professor, Queen's University Belfast
Tim Heaton, Lecturer in Statistics, University of Sheffield
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/142810
2020-07-22T19:51:24Z
2020-07-22T19:51:24Z
Humans inhabited North America in the depths of the last Ice Age, but didn’t thrive until the climate warmed
<figure><img src="https://images.theconversation.com/files/348770/original/file-20200722-29-1cgvogd.jpg?ixlib=rb-1.1.0&rect=2%2C8%2C1914%2C1267&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Chiquihuite Cave in Mexico.</span> <span class="attribution"><span class="source">Devlin A. Gandy</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Humans lived in what is now Mexico up to 33,000 years ago and may have settled the Americas by travelling along the Pacific coast, according to two studies by myself and colleagues published today. </p>
<p>It has been commonly believed that the first people to enter the Americas were big-game hunters from Asia, who arrived after the last Ice Age around 13,000 years ago. This narrative is known as the “Clovis first” theory, based on distinctive stone tools produced by a people archaeologists call the Clovis culture.</p>
<p>For most of the 20th century, this theory was widely accepted. However, more recent archaeological evidence has shown humans were present in the Americas before the Clovis people.</p>
<p>Just how much earlier, however, is unclear and a topic of intense academic debate. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ancient-dna-in-lake-mud-sheds-light-on-the-mystery-of-how-humans-first-reached-america-63776">Ancient DNA in lake mud sheds light on the mystery of how humans first reached America</a>
</strong>
</em>
</p>
<hr>
<h2>What we found in Chiquihuite Cave</h2>
<p>Chiquihuite Cave is an archaeological site more than 2,740 metres above sea level in Zacatecas, Mexico. Ciprian Ardelean of the University of Zacatecas has been leading excavations of the site for more than seven years. Nearly 2,000 stone tools and pieces created through their manufacture have been found. </p>
<p>The tools belongs to a type of material culture never before seen in the Americas, with no evident similarities to any other cultural complexes. Importantly, more than 200 specimens were found below an archaeological layer that corresponds to the peak of the last Ice Age. (Archaeologists call this peak the Last Glacial Maximum.) </p>
<p>During this time, between 26,000 and 19,000 years ago, ice sheets were at their greatest extent. Evidence from Chiquihuite Cave, therefore, strongly suggests that humans were present in North America well before Clovis. </p>
<figure class="align-center ">
<img alt="A hand holding a small stone tool." src="https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348775/original/file-20200722-25-1m3rygt.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">A stone tool found below the Last Glacial Maximum layer.</span>
<span class="attribution"><span class="source">Ciprian Ardelean</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Given the significance of the discovery, myself and a team of international researchers joined in the interdisciplinary study of Chiquihuite Cave. Some of us had the opportunity to visit the site following a four-hour long journey by foot, and see the evidence at first hand. Our aims were to reconstruct the environment humans lived in and define exactly when they occupied the site. </p>
<p>My own research at Chiquihuite Cave focused on the latter. I helped to build a chronology of more than 50 radiocarbon and optical dates. </p>
<p>Combined with the archaeological evidence, the <a href="https://www.nature.com/articles/s41586-020-2509-0">results</a> showed humans inhabited Chiquihuite as early as 33,000 years ago, until the cave was sealed off at the end of the Pleistocene period (around 12,000 years ago). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A woman walking into a cave" src="https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348240/original/file-20200719-29-52patm.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">Lorena Becerra-Valdivia inside Chiquihuite Cave in 2019, walking towards the archaeological excavations.</span>
<span class="attribution"><span class="source">Thomas L.C. Gibson</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The pattern of settlement</h2>
<p>In <a href="https://www.nature.com/articles/s41586-020-2491-6">a second paper</a>, I explore the wider pattern of human occupation across North America and Beringia (the ancient land bridge connecting America to Asia). This involved analysing hundreds of dates obtained from 42 archaeological sites in North America and Beringia, including Chiquihuite Cave, using a statistical tool called Bayesian age modelling. </p>
<p>The analysis showed there were humans in North America before, during and immediately after the peak of the last Ice Age. However, it was not until much later that populations expanded significantly across the continent. </p>
<p>This occurred during a period of climate warming at the end of the Ice Age called Greenland Interstadial 1. The warming began suddenly with a pulse of increased global temperature around 14,700 years ago. </p>
<p>We also observed that the three major stone tool traditions in the wider region started around the same time. This coincides with an increase in archaeological sites and radiocarbon dates from those sites, as well as genetic data pointing to marked population growth. </p>
<p>This significant expansion of humans during a warmer period seems to have played a role in the dramatic demise of large megafauna, including types of camels, horses and mammoths. We plotted the dates of the last appearance of the megafauna and found they largely disappeared within this, and a following, colder period. </p>
<p>However, the contribution of climate change in faunal extinctions, represented by abrupt warming and cooling, cannot be fully excluded. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-evidence-that-an-extraterrestrial-collision-12-800-years-ago-triggered-an-abrupt-climate-change-for-earth-118244">New evidence that an extraterrestrial collision 12,800 years ago triggered an abrupt climate change for Earth</a>
</strong>
</em>
</p>
<hr>
<p>The first human arrivals came from eastern Eurasia, yet it looks as though there was a surprisingly early movement of people into the continent. </p>
<p>We think the path of earlier arrivals to these new lands was probably along the coast. Inland travel would have been blocked, either because Beringia was partly underwater or because modern-day Canada was covered by impenetrable ice sheets.</p>
<p>Together, the two studies and their results depart from previously accepted models, and allow us to uncover a new story of the initial peopling of the Americas. This journey, marking one of the major expansions of modern humans across the planet, will continue to mystify and spark debate.</p><img src="https://counter.theconversation.com/content/142810/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lorena Becerra-Valdivia 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>
Stone tools found in a cave in Mexico have archaeologists rewriting the human history of the Americas.
Lorena Becerra-Valdivia, Postdoctoral Research Fellow, UNSW Sydney
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/129422
2020-04-29T12:23:54Z
2020-04-29T12:23:54Z
Archaeologists have a lot of dates wrong for North American indigenous history – but we’re using new techniques to get it right
<figure><img src="https://images.theconversation.com/files/331175/original/file-20200428-110775-ug6wjw.jpg?ixlib=rb-1.1.0&rect=50%2C43%2C1506%2C1140&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">For centuries, indigenous history has been largely told through a European lens.</span> <span class="attribution"><a class="source" href="https://www.britishmuseum.org/collection/image/1613648693">John White, circa 1585-1593, © The Trustees of the British Museum</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>Columbus famously reached the Americas in 1492. Other Europeans had <a href="https://www.sup.org/books/title/?id=2317">made the journey before</a>, but the century from then until 1609 marks the <a href="https://www.nytimes.com/2011/08/21/books/review/1493-uncovering-the-new-world-columbus-created-by-charles-c-mann-book-review.html">creation of the modern globalized world</a>.</p>
<p>This period brought extraordinary riches to Europe, and genocide and disease to indigenous peoples across the Americas.</p>
<p><iframe id="mi0Pd" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/mi0Pd/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The European settlement dates and personalities are known from <a href="https://www.gutenberg.org/files/25645/25645-pdf.pdf">texts</a> and sometimes <a href="https://www.smithsonianmag.com/travel/sketching-the-earliest-views-of-the-new-world-92306407/">illustrations</a>, to use the failed colony on what was then Virginia’s Roanoke Island as an example.</p>
<p>But one thing is missing. What about indigenous history throughout this traumatic era? Until now, the standard timeline has derived, inevitably, from the European conquerors, even when scholars <a href="https://www.mqup.ca/children-of-aataentsic--the-products-9780773506275.php">try to present an indigenous perspective</a>. </p>
<p>This all happened just 400 to 500 years ago – how wrong could the conventional chronology for indigenous settlements be? Quite wrong, it turns out, <a href="https://doi.org/10.1126/sciadv.aav0280">based on radiocarbon dating</a> my collaborators and I have carried out at a number of Iroquoian sites in Ontario and New York state. We’re challenging existing – and rather colonialist – assumptions and mapping out the correct time frames for when indigenous people were active in these places.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330130/original/file-20200423-47815-10i5haa.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">Dating Iroquoia project member Samantha Sanft excavating at White Springs, New York.</span>
<span class="attribution"><span class="source">Samantha Sanft and Kurt Jordan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Refining dates based on European goods</h2>
<p>Archaeologists estimate when a given indigenous settlement was active based on the absence or presence of certain types of European trade goods, such as metal and glass beads. It was always approximate, but became the conventional history.</p>
<p>Since the first known <a href="https://www.jstor.org/stable/j.ctt80szr">commercial fur trading missions were in the 1580s</a>, archaeologists date initial regular appearances of scattered European goods to 1580-1600. They call these two decades Glass Bead Period 1. We know some trade occurred before that, though, since indigenous people Cartier met in the 1530s <a href="https://www.gutenberg.org/files/4077/4077-h/4077-h.htm#chap03">had previously encountered Europeans, and were ready to trade</a> with him.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=736&fit=crop&dpr=1 600w, https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=736&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=736&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=925&fit=crop&dpr=1 754w, https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=925&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/331171/original/file-20200428-110738-1dbr0lp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=925&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">16th-century European copper alloy beads from two sites in the Mohawk Valley.</span>
<span class="attribution"><span class="source">New York State Museum</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Archaeologists set Glass Bead Period 2 from 1600-1630. During this time, new types of glass beads and finished metal goods were introduced, and trade was more frequent.</p>
<p>The logic of dating based on the absence or presence of these goods would make sense if all communities had equal access to, and desire to have, such items. But these key assumptions have not been proven. </p>
<p>That’s why the <a href="https://datingiroquoia.wordpress.com/">Dating Iroquoia Project</a> exists. Made up of researchers here at Cornell University, the University of Georgia and the New York State Museum, we’ve used <a href="http://www.c14dating.com/">radiocarbon dating</a> and statistical modeling to date organic materials directly associated with Iroquoian sites in <a href="https://doi.org/10.1371/journal.pone.0226334">New York’s Mohawk Valley</a> and <a href="https://doi.org/10.1126/sciadv.aav0280">Ontario in Canada</a>.</p>
<p>First we looked at two sites in Ontario: Warminster and Ball. Both are long argued to have had direct connections with Europeans. For instance, <a href="https://en.wikipedia.org/wiki/Samuel_de_Champlain">Samuel de Champlain</a> likely stayed at the <a href="https://doi.org/10.1017/aaq.2019.60">Warminster site</a> in 1615-1616. Archaeologists have found large numbers of trade goods at both sites.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=446&fit=crop&dpr=1 754w, https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=446&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/331174/original/file-20200428-110752-12sautc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=446&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Centuries-old maize sample, ready to be radiocarbon dated.</span>
<span class="attribution"><span class="source">Eva Wild</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When my colleagues and I examined and radiocarbon dated plant remains (maize, bean, plum) and a wooden post, the calendar ages we came up with are entirely consistent with historical estimates and the glass bead chronology. The three dating methods agreed, placing Ball circa 1565-1590 and Warminster circa 1590-1620.</p>
<p>However, the picture was quite different at several other major Iroquois sites that lack such close European connections. Our radiocarbon tests came up with substantially different date ranges compared with previous estimates that were based on the presence or absence of various European goods.</p>
<p>For example, the Jean-Baptiste Lainé, or <a href="https://rowman.com/ISBN/9780759121010/The-Mantle-Site-An-Archaeological-History-of-an-Ancestral-Wendat-Community">Mantle, site</a> northeast of Toronto is currently the largest and most complex Iroquoian village excavated in Ontario. <a href="http://asiheritage.ca/publication/mantle-site/">Excavated between 2003–2005</a>, archaeologists dated the site to 1500–1530 because it lacks most trade goods and had just three European-source metal objects. But our radiocarbon dating now places it <a href="https://doi.org/10.1126/sciadv.aav0280">between about 1586 and 1623, most likely 1599-1614</a>. That means previous dates were off the mark by as much as 50 to 100 years.</p>
<p>Other sites belonging to this same ancestral Wendat community are also more recent than previously assumed. For example, a site called Draper was conventionally dated to the second half of the 1400s, but radiocarbon dating places it at least 50 years later, between 1521 and 1557. Several other Ontario Iroquoian sites lacking large trade good assemblages vary by <a href="https://doi.org/10.1017/aaq.2019.60">several decades to around 50 years or so</a> from conventional dates based on our work.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330138/original/file-20200423-47810-yawh32.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">Sturt Manning examining a sample in the Cornell Tree Ring Laboratory.</span>
<span class="attribution"><span class="source">Chris Kitchen/Cornell University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>My colleagues and I have also investigated a number of sites in the Mohawk Valley, in New York state. During the 16th and early 17th centuries, the Mohawk and Hudson Rivers formed a key transport route from the Atlantic coast inland for Europeans and their trade goods. Again, we found that radiocarbon dating <a href="https://doi.org/10.1371/journal.pone.0226334">casts doubt on the conventional time frame</a> attributed to a number of sites in the area.</p>
<h2>Biases that led to misguided timelines</h2>
<p>Why was some of the previous chronology wrong?</p>
<p>The answer seems to be that scholars viewed the topic through a pervasive colonial lens. Researchers mistakenly assumed that trade goods were equally available, and desired, all over the region, and considered all indigenous groups as the same.</p>
<p><a href="https://www.mqup.ca/children-of-aataentsic--the-products-9780773506275.php">To the contrary</a>, it was Wendat custom, for example, that the lineage whose members <a href="https://www.wyandotte-nation.org/culture/history/published/native-peoples/">first discovered a trade route claimed rights to it</a>. Such “ownership” <a href="https://doi.org/10.4000/palethnologie.482">could be a source of power and status</a>. Thus it would make sense to see uneven distributions of certain trade goods, as mediated by the controlling groups. Some people were “in,” with access, and others may have been “out.”</p>
<p>Ethnohistoric records indicate cases of indigenous groups rejecting contact with Europeans and their goods. For example, Jesuit missionaries described an <a href="http://moses.creighton.edu/kripke/jesuitrelations/relations_15.html">entire village no longer using French kettles</a> because the foreigners and their goods were blamed for disease.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330132/original/file-20200423-47784-y5x5hg.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">Dating Iroquoia Project member Megan Conger excavating at White Springs, New York. Some locations have been under-explored, so far, by archaeologists.</span>
<span class="attribution"><span class="source">Megan Conger, Kurt Jordan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>There are other reasons European goods do or do not show up in the archaeological record. How near or far a place was from transport routes, and local politics, both within and between groups, could play a role. Whether Europeans made direct contact, or there were only indirect links, could affect availability. Objects used and kept in settlements could also vary from those intentionally buried in cemeteries.</p>
<p>Above all, the majority of sites are only partly investigated at best, some are as yet unknown. And sadly the archaeological record is affected by the looting and destruction of sites.</p>
<p>Only a direct dating approach removes the Eurocentric and historical lens, allowing an independent time frame for sites and past narratives.</p>
<h2>Effects of re-dating indigenous history</h2>
<p>Apart from changing the dates for textbooks and museum displays, the re-dating of a number of Iroquoian sites raises major questions about the social, political and economic history of indigenous communities.</p>
<p>For example, conventionally, researchers place the start of a shift to larger and fortified communities, and evidence of increased conflict, in the mid-15th century. </p>
<p>However, our radiocarbon dates find that some of the key sites are from a century later, dating from the mid-16th to start of the 17th centuries. The timing raises questions of whether and how early contacts with Europeans did or did not play a role. This period was also <a href="https://time.com/4946501/colonial-america-climate-change/">during the peak of what’s called the Little Ice Age</a>, perhaps indicating the changes in indigenous settlements have some association with climate challenge.</p>
<p>Our new radiocarbon dates indicate the correct time frame; they pose, but do not answer, many other remaining questions.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/129422/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sturt Manning receives funding from The National Science Foundation and The National Endowment for the Humanities. He is affiliated with Cornell University. </span></em></p>
Modern dating techniques are providing new time frames for indigenous settlements in Northeast North America, free from the Eurocentric bias that previously led to incorrect assumptions.
Sturt Manning, Director of the Cornell Tree Ring Laboratory and Professor of Classical Archaeology, Cornell University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/129429
2020-01-20T16:01:07Z
2020-01-20T16:01:07Z
Native people did not use fire to shape New England’s landscape
<figure><img src="https://images.theconversation.com/files/310034/original/file-20200114-93792-1vahvzb.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C613%2C409&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Old-growth forests prevailed in New England for thousands of years.</span> <span class="attribution"><span class="source">David Foster</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>An interpretive sign stands at the edge of the Montague Plains Wildlife Management Area, a 1,500-acre state conservation property in central Massachusetts. It explains the site’s open land vegetation has been shaped by “millennia of fire” – and that the recent exclusion of fire has led to declines in this habitat and the species that call it home. It goes on to explain that fire is being reintroduced to the site through controlled burns “to reinvigorate fire-adapted species.”</p>
<p>The prescribed burning at Montague Plains and dozens of other conservation areas across New England is based on the belief that, for thousands of years, Native Americans <a href="https://www.tandfonline.com/doi/abs/10.1080/10549811.2014.973608">cleared forests and used fire</a> to improve habitat for the plants and animals they relied upon. The use of fire as a management tool is just one example of a broader shift in how ecologists and conservationists have come to think about the impacts of ancient humans. Increasingly, researchers believe <a href="https://www.penguinrandomhouse.com/books/107178/1491-second-edition-by-charles-c-mann/">Native people controlled ecosystems across much of the globe</a>, from boreal regions to the Amazon, including many areas formerly deemed pristine.</p>
<p>Our new research, published in the journal Nature Sustainability, <a href="https://doi.org/10.1038/s41893-019-0466-0">tests this human-centric view of the past</a> using interdisciplinary, retrospective science. The data we collected suggest, in New England, this assumption is erroneous.</p>
<h2>Sediment tells the story</h2>
<p>In the field of paleo-ecology, researchers take advantage of the fact that, over time, the bottoms of lakes and ponds fill up with mud. Using a hand-driven device, scientists can collect a cylindrical core of the sediment and then use <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">radiocarbon dating</a> to determine the age of the mud at different depths. Over the last century, scientists have collected sediment cores from hundreds of lakes around the world, enabling them to reconstruct past environments and ecosystems. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310031/original/file-20200114-151867-p5gnl9.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"></a>
<figcaption>
<span class="caption">Paleo-ecologist Bryan Shuman collecting a sediment core from Green Pond, central Massachusetts.</span>
<span class="attribution"><span class="source">Wyatt Oswald</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our team of paleo-ecologists and archaeologists collected sediment cores from 23 ponds across southern New England. We analyzed ancient pollen grains, fragments of charcoal and clues about past water depth, all preserved in the mud, allowing us to create a record of vegetation, fire and climate over thousands of years. </p>
<p>We then compared this ecological and environmental history with data from more than 1,800 archaeological sites along the coast from Cape Cod to Long Island, including the islands of Martha’s Vineyard, Nantucket and the Elizabeth Islands. These areas historically <a href="https://pqdtopen.proquest.com/doc/304891312.html?FMT=ABS">supported the greatest densities of Native people in New England</a> and today are home to the <a href="http://sandplaingrassland.net/management/management-overview/">highest concentrations of endangered species and rare open land habitats</a> in the region.</p>
<p>Our study contradicts the theory that people had significant ecological impacts in southern New England before European arrival. Instead, it reveals that old forests, shaped by climate change and natural processes, prevailed across the region for thousands of years.</p>
<p>Native populations in southern New England <a href="https://doi.org/10.1073/pnas.1005764107">peaked at two times during the last several millennia</a>: 5,000-3,000 years ago, during what archaeologists call the Late Archaic Period, and 1,500-500 years ago, a period known as the Middle-Late Woodland. During those times when Native populations were relatively high, we found no evidence for forest clearance, elevated use of fire, or widespread agriculture. Interestingly, fire activity was high only 10,000-8,000 years ago, <a href="https://doi.org/10.1016/j.quascirev.2016.03.009">a period that was substantially drier than today</a>, with low human populations.</p>
<p>Of course, the indigenous people of New England utilized and relied on a wide variety of natural resources: they hunted, fished, foraged, and cultivated some edible plants. <a href="https://uofupress.lib.utah.edu/ancient-complexities/">Pre-Colonial societies were complex, widespread and large</a>, with populations in the tens of thousands. But the evidence suggests they didn’t use fire to open large swaths of the landscape for agriculture. Rather, over more than 10,000 years, these highly adaptable people <a href="https://pqdtopen.proquest.com/doc/304891312.html?FMT=ABS">shifted activities seasonally across the landscape</a>, taking advantage of a wide range of resources and exerting limited, and most likely very localized, ecological impacts overall. </p>
<h2>From dense forests to more open land</h2>
<p>So, if Native Americans didn’t clear forests and create open lands across southern New England, how and when did the grasslands, shrub lands and open forests in existence today originate?</p>
<p>When we analyzed the mud in our study ponds, we found the obvious signature of forest clearance by 17th-century European colonists. Pollen from forest species declined, while pollen from agricultural and weedy species, like ragweed, increased abruptly. This evidence clearly shows New England’s open land habitats owe their existence to Colonial European deforestation and agriculture, especially sheep and cattle grazing, hay production, and orchard and vegetable cultivation in the 18th and 19th centuries.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=728&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=728&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=728&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=914&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=914&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310055/original/file-20200114-151834-meewgo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=914&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sheep grazing on Martha’s Vineyard.</span>
<span class="attribution"><span class="source">David Foster</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>This retrospective research should cause some conservationists to reconsider both their rationale and tools for land management. If the goal is to emulate the conditions that existed prior to the arrival of Europeans, land managers should allow New England forests to mature with minimal human disturbance. If the goal is also to maintain biodiverse open land habitats, like Montague Plains, within the largely forested landscape, managers should apply the Colonial-era agricultural approaches that created them nearly 400 years ago. Those tools would include mowing, grazing and cutting woody vegetation – but not burning.</p>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>. ]</p><img src="https://counter.theconversation.com/content/129429/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wyatt Oswald has received funding from the US National Science Foundation. </span></em></p><p class="fine-print"><em><span>We previously received National Science Foundation support for the research discussed in this article. </span></em></p><p class="fine-print"><em><span>David R. Foster 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>
Evidence shows Native Americans in New England lived lightly on the land for thousands of years. It wasn’t until Europeans arrived that the landscape experienced major human impacts.
Wyatt Oswald, Professor of Environmental Science, Emerson College
David R. Foster, Director, Harvard Forest, Harvard University
Elizabeth Chilton, Dean of the Harpur College of Arts and Sciences and Professor of Anthropology, Binghamton University, State University of New York
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/104480
2018-10-05T09:03:47Z
2018-10-05T09:03:47Z
Explosive lies: how volcanoes can lie about their age, and what it means for us
<figure><img src="https://images.theconversation.com/files/239458/original/file-20181005-72130-nou341.jpg?ixlib=rb-1.1.0&rect=277%2C605%2C5313%2C3068&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lake Taupo, in the North Island of New Zealand, is a globally significant caldera of a supervolcano that formed following a massive eruption more than 20,000 years ago.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Just like a teenager wanting to be older, volcanoes can lie about their age, or at least about their activities. For kids, it might be little white lies, but volcanoes can tell big lies with big consequences.</p>
<p><a href="https://doi.org/10.1038/s41467-018-06357-0">Our research</a>, published today in Nature Communications, uncovers one such volcanic lie.</p>
<p>Accurate dating of prehistoric eruptions is important as it allows scientists to <a href="https://pubs.geoscienceworld.org/gsa/geosphere/article/14/2/572/529016/anticipating-future-volcanic-explosivity-index-vei">correlate them with other records</a>, such as large earthquakes, Antarctic ice cores, historical events like <a href="https://www.cambridge.org/core/journals/antiquity/article/thera-olive-branch-akrotiri-thera-and-palaikastro-crete-comparing-radiocarbon-results-of-the-santorini-eruption/FA98CB27FD0AC28B06AC561083CADC9E">Mediterranean civilisation milestones</a>, and climatic events like the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011GL050168">Little Ice Age</a>. This gives us a better understanding of the links between volcanism and the natural and cultural environment.</p>
<h2>Taupo’s last violent eruption</h2>
<p><a href="https://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/New-Zealand-Volcanoes/Taupo-Volcano">Lake Taupo</a>, in the North Island of New Zealand, is a globally significant caldera <a href="https://www.usgs.gov/faqs/what-a-supervolcano?qt-news_science_products=0#qt-news_science_products">supervolcano</a>. The <a href="https://volcanoes.usgs.gov/vsc/glossary/caldera.html">caldera</a> formed after the collapse of a magma chamber roof following a massive eruption more than 20,000 years ago.</p>
<p>Now it seems that the Taupo eruption that occurred in the early part of the first millennium has been lying about its age. But like many lies, it was eventually found out, and it reveals exciting processes we hadn’t understood before.</p>
<p>The <a href="https://www.sciencedirect.com/science/article/pii/S0377027310001836">eruption of Taupo</a> in the first millennium has been dated many times with radiocarbon, yielding a surprisingly large spread of ages between 36CE and 538CE. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-volcanoes-erupt-98251">Curious Kids: Why do volcanoes erupt?</a>
</strong>
</em>
</p>
<hr>
<h2>Radiocarbon dating of eruptions</h2>
<p><a href="https://en.wikipedia.org/wiki/Radiocarbon_dating">Radiocarbon dating</a> of organic material is based on the concentrations of radioactive carbon-14 in a sample remaining after the organisms’ death. Over the past two decades, the method has been refined greatly by combining it with dendrochronology, the study of the environmental effects on the width of tree rings through time. </p>
<p>Radiocarbon dating of tree ring records has allowed scientists to construct a reliable record of the concentration of carbon-14 in the atmosphere through time.</p>
<p>In principle, this composite record allows eruptions to be dated by matching the wiggly trace of carbon-14 in a tree killed by an eruption to the wiggly trace of atmospheric carbon-14 from the reference curve (“wiggle-match” dating).</p>
<p>Scientists presently use <a href="https://en.wikipedia.org/wiki/Wiggle_matching">wiggle-match dating</a> as the method of choice for eruption dating, but the technique is not valid if carbon dioxide gas from the volcano is affecting a tree’s version of the wiggle.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/balis-agung-using-volcano-forensics-to-map-the-past-and-predict-the-future-88229">Bali's Agung – using 'volcano forensics' to map the past, and predict the future</a>
</strong>
</em>
</p>
<hr>
<h2>The effect of volcanic carbon on eruption ages</h2>
<p>Our <a href="https://doi.org/10.1038/s41467-018-06357-0">study</a> re-analysed the large series of radiocarbon dates for the Taupo eruption and found that the oldest dates were closest to the volcano vent. The dates were progressively younger the farther away they were. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/239451/original/file-20181005-72133-1ontkwh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&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 graph shows all of the ages obtained for the Taupo first millenium eruption, sorted by age, plotted on a digital model of the North Island of New Zealand. Lake Taupo is the caldera from which the eruption occurred. The oldest ages for the eruption are clustered around Lake Taupo, and older ages are located further from the volcano. We interpret this pattern as being caused by contamination of red areas with volcanic carbon dioxide.</span>
<span class="attribution"><span class="source">Provided by authors</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This unusual geographic pattern has been documented very close (i.e. less than a kilometre) to volcanic vents before, but never on the scale of tens of kilometres. <a href="http://journals.sagepub.com/doi/abs/10.1177/0959683611425551?journalCode=hola">Two wiggle match ages</a>, taken from the same forest, located about 30km from the caldera lake, were among the oldest dates from the series of dates.</p>
<p>This enlarged influence of the volcano can be explained by the influence of groundwater beneath the lake and its surroundings. The Taupo wiggle-match tree grew in a dense forest in a swampy valley where volcanic carbon dioxide was seeping out of the ground and was incorporated in the trees.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=576&fit=crop&dpr=1 600w, https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=576&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=576&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=724&fit=crop&dpr=1 754w, https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=724&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/239437/original/file-20181005-52672-zt4dg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=724&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 conceptual image shows how gas from the triggering event, decades before the eruption, works its way into the groundwater system and is eventually incorporated in the wood of the trees that we date.</span>
<span class="attribution"><span class="source">Provided by authors</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The ratio of carbon-13 to carbon-12 (the two stable isotopes of carbon) in the modern water of Lake Taupo and the Waikato River tells us that volcanic carbon dioxide is getting into the groundwater from an underlying magma body.</p>
<h2>Can large eruptions be forecast over decades?</h2>
<p>Our study shows that a large and increasing volume of carbon dioxide gas containing these stable isotopes was emitted from deep below the prehistoric Taupo volcano. It was then redistributed by the region’s huge groundwater system, ultimately becoming incorporated into the wood of the dated trees.</p>
<p>The increase was sufficiently large over several decades to dramatically alter the ratios of different carbon isotopes in the tree wood. The forest was subsequently killed by the last part of the Taupo eruption series. But the dilution of atmospheric carbon-14 by volcanic carbon made the radiocarbon dates for tree material from the Taupo eruption appear somewhere between 40 and 300 years too old.</p>
<p>The precursory change in carbon ratios gives us a way to gain insight into the forecasting of future eruptions, <a href="http://dusk.geo.orst.edu/prosem/PDFs/forecasting_volc.pdf">a central goal in volcanology</a>. We found that the radiocarbon dates and isotope data that underpin the presently accepted “wiggle match” age reached a plateau (that is, stopped evolving normally). This meant that for several decades before the eruption, the outer growth rings of trees had ‘weird’ carbon ratios, forecasting the impending eruption. </p>
<p>We re-analysed data from other major eruptions, including at Rabaul in Papua New Guinea and Baitoushan on the North Korean border with China and found similar patterns. The anomalous chemistry mimics but exceeds the <a href="https://en.wikipedia.org/wiki/Suess_effect">Suess effect</a>, which reversed the carbon isotopic evolution of post-industrial wood. This implies that measurements of carbon isotopes in 200-300 annual rings can track changes in the carbon source used by trees growing near a volcano, providing a potential method of forecasting future large eruptions.</p>
<p>We anticipate that this will provide a significant focus for future research at <a href="https://en.wikipedia.org/wiki/Supervolcano#Known_super_eruptions">supervolcanoes around the globe</a>.</p><img src="https://counter.theconversation.com/content/104480/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ben Kennedy receives funding from the New Zealand Ministry of Business Innovation and Employment Endeavour Fund ECLIPSE project. He is affiliated with University of Canterbury</span></em></p><p class="fine-print"><em><span>Brendan Duffy and Richard N Holdaway 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 research shows that carbon dioxide in groundwater can affect the aging of volcanic eruptions. The findings could help predict future eruptions.
Richard N Holdaway, Adjunct Professor, University of Canterbury
Ben Kennedy, University of Canterbury
Brendan Duffy, Lecturer in Applied Geoscience, The University of Melbourne
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/91319
2018-02-15T17:56:41Z
2018-02-15T17:56:41Z
Essays On Air: When did Australia’s human history begin?
<figure><img src="https://images.theconversation.com/files/205013/original/file-20180206-14093-b6ps9e.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In July 2017, new research was published that pushed the opening chapters of Australian history back to 65,000 years ago. </span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>In July 2017, new research was published that pushed the opening chapters of Australian history back to 65,000 years ago. It is the latest development in a time revolution that has gripped the nation over the past half century.</p>
<p>In today’s episode of <a href="https://theconversation.com/au/topics/essays-on-air-48405">Essays On Air</a> - the audio version of our <a href="https://theconversation.com/au/topics/friday-essay-22955">Friday essay</a> series - we’re reading you Billy Griffiths, Lynette Russell and Richard “Bert” Roberts’ essay <a href="https://theconversation.com/friday-essay-when-did-australias-human-history-begin-87251">When did Australia’s human history begin?</a> </p>
<p>This essay seeks to move beyond the view of ancient Australia as a timeless and traditional foundation story to explore the ways in which scientists and humanists are engaging with the deep past.</p>
<p>Find Essays On Air in <a href="https://itunes.apple.com/au/podcast/essays-on-air/id1333743838?mt=2">Apple Podcasts</a>, in <a href="https://play.pocketcasts.com/">Pocket Casts</a> or wherever you get your podcasts.</p>
<h2>Additional audio</h2>
<p>Snow by <a href="http://freemusicarchive.org/music/David_Szesztay/Cinematic/Snow">David Szesztay</a></p>
<p><a href="https://www.youtube.com/watch?v=oVxfCkWaqOs">Tourism Australia advertisement</a></p>
<p>Didgeridoo <a href="https://www.youtube.com/watch?v=QUGytDzsgew">by Jimmie P Rodgers</a></p>
<p>I am Australian <a href="https://www.youtube.com/watch?v=d6sjKLCrHTE">by The Seekers</a></p>
<p><em>This episode was edited by Jenni Henderson. Illustration by Marcella Cheng.</em></p><img src="https://counter.theconversation.com/content/91319/count.gif" alt="The Conversation" width="1" height="1" />
Today's episode of Essays On Air, the audio version of our Friday essay series, seeks to move beyond the view of ancient Australia as a timeless and traditional foundation story.
Sunanda Creagh, Senior Editor
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/90391
2018-01-23T19:12:29Z
2018-01-23T19:12:29Z
Curious Kids: How do scientists work out how old the Earth is?
<figure><img src="https://images.theconversation.com/files/202744/original/file-20180122-110097-12vj03h.png?ixlib=rb-1.1.0&rect=0%2C0%2C2995%2C1320&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It turns out that the world is about 4,600,000,000 years old. That's 4.6 billion years. That's pretty old!</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>How do scientists work out how old the Earth is? Leo, age 5, Geelong West.</strong></p>
</blockquote>
<p>Well, Leo, the world is actually like a big clock. We just need to know how to read the clock. To do that, we have to think about what the world is made of. </p>
<p>The world, and everything in it, is actually made of something very small called “elements”. These are the tiny, tiny building blocks of everything. You might have heard the names of some elements before. Gold is an element, and so is silver. There are lots of other elements too, with strange names like krypton and selenium and plutonium. There are about 118 different elements on Earth that we know about so far.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">Explainer: what is radiocarbon dating and how does it work?</a>
</strong>
</em>
</p>
<hr>
<p>Most of these elements don’t change and stay the way they are forever. Scientists call these ones “stable” elements. </p>
<p>But there is a second sort of element that actually changes into something else over time. These aren’t as common, but they are in everything. They’re called “unstable” or “radioactive” elements.</p>
<p>Imagine that - some part of you is actually changing into something else! But don’t worry, most of these change over a very, very long time. Some take billions of years to do any really serious changing. </p>
<p>Your teeth have an element called potassium that is one of these changing elements. Your TV, computer, the soil in your garden – everything, really – has some of these changing elements. The changing process is called “radioactive decay”.</p>
<p>As you might have guessed, rocks also have these unstable elements in them. And we’ve measured out how long it takes for one of these elements to change into another one. </p>
<p>For example, if we had some stuff that contained an unstable element called <sup>14</sup>C (to say out loud, this is “carbon 14”), we know it takes about 5,730 years for about half of all the <sup>14</sup>C in our sample to change into another element called <sup>14</sup>N (pronounced as “nitrogen 14”).</p>
<p>Knowing how fast these elements change from one thing into another thing gives us a very big clue about how old the Earth is. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scientists using the same techniques to work out how old fossils are.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/skippy/452231025/in/photolist-FXNwD-brVUa-9TYo4-foH1Sj-7yC3NV-LyGgG-oH9Hbw-7qGxb1-7BTRZe-3VwGHj-6rcG8U-qEwTLj-aH4QYR-6rcMy9-nGUwUy-k6rwa1-xBLms1-VsqnT7-adHvfz-bs4aEL-UkFeMr-7gXqBj-pmVKXa-22s4SY3-TzTWU5-WetkBY-yYbuwy-7gXokN-prE9br-bi7KjT-5qFrF3-9Dggzr-TUNEQ3-5cgiEa-7shDR8-VApJyE-aJcsdV-VstT2X-9keehg-aELxKE-7aU1eK-djmV9Z-4xkaao-VstTMe-2p8Yhx-4xkaty-a8zjJ7-jdzSh5-4n1mdj-4oyRma">Flickr/Scott</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-bees-ever-accidentally-sting-other-bees-82818">Curious Kids: Do bees ever accidentally sting other bees?</a>
</strong>
</em>
</p>
<hr>
<p>So how do we measure how old the Earth is? </p>
<p>Well, first we measure how much of the unstable elements are still left in the rocks of the Earth - these are the elements that haven’t changed yet, but <em>will</em> change over time because we know they’re unstable. </p>
<p>Then we measure the amount of the element they change <em>into</em>. </p>
<p>Once we know this, and we know how long the change takes, we can work out how old the world is! </p>
<p>It turns out that the world is about 4,600,000,000 years old. That’s 4.6 billion years. That’s pretty old!</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
<br>
* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #curiouskids, or
<br>
* Tell us on <a href="http://www.facebook.com/conversationEDU">Facebook</a></em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/90391/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Collins receives funding from the Australian Research Council</span></em></p>
The world is made of tiny building blocks called ‘elements’. Scientists have worked out how fast some elements change into other elements. That gives us a very big clue about how old the Earth is.
Alan Collins, Professor of Geology, University of Adelaide
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/65606
2017-04-07T01:35:28Z
2017-04-07T01:35:28Z
DNA dating: How molecular clocks are refining human evolution’s timeline
<figure><img src="https://images.theconversation.com/files/164196/original/image-20170405-14615-pgkdmv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our cells have a built-in genetic clock, tracking time... but how accurately?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hand-holding-retro-stopwatch-black-white-256422460">Stopwatch image via www.shutterstock.com.</a></span></figcaption></figure><p>DNA holds the story of our ancestry – how we’re related to the familiar faces at family reunions as well as more ancient affairs: how we’re related to our closest nonhuman relatives, chimpanzees; how <em>Homo sapiens</em> mated with Neanderthals; and how people migrated out of Africa, adapting to new environments and lifestyles along the way. And our DNA also holds clues about the timing of these key events in human evolution.</p>
<p>When scientists say that <a href="http://doi.org/10.1038/nature18964">modern humans emerged</a> in Africa about 200,000 years ago and began their global spread about 60,000 years ago, how do they come up with those dates? Traditionally researchers built timelines of human prehistory based on fossils and artifacts, which can be directly dated with methods such as <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">radiocarbon dating</a> and Potassium-argon dating. However, these methods require ancient remains to have certain elements or preservation conditions, and that is not always the case. Moreover, relevant fossils or artifacts have not been discovered for all milestones in human evolution.</p>
<p>Analyzing DNA from present-day and ancient genomes provides a complementary approach for dating evolutionary events. Because certain genetic changes occur at a steady rate per generation, they provide an estimate of the time elapsed. These changes accrue like the ticks on a stopwatch, providing a “molecular clock.” By comparing DNA sequences, geneticists can not only reconstruct relationships between different populations or species but also infer evolutionary history over deep timescales.</p>
<p>Molecular clocks are becoming more sophisticated, thanks to improved DNA sequencing, analytical tools and a better understanding of the biological processes behind genetic changes. By applying these methods to the ever-growing database of DNA from diverse populations (both present-day and ancient), geneticists are helping to build a more refined timeline of human evolution.</p>
<h2>How DNA accumulates changes</h2>
<p>Molecular clocks are based on two key biological processes that are the source of all heritable variation: mutation and recombination. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/164195/original/image-20170405-14612-1cas5ot.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">Mutations are changes to the DNA code, such as when one nucleotide base (A, T, G or C) is incorrectly subbed for another.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/vector-illustration-dna-structure-303407264">DNA image via www.shutterstock.com</a></span>
</figcaption>
</figure>
<p>Mutations are changes to the letters of DNA’s genetic code – for instance, a nucleotide Guanine (G) becomes a Thymine (T). These changes will be inherited by future generations if they occur in eggs, sperm or their cellular precursors (the germline). Most result from mistakes when DNA copies itself during cell division, although other <a href="https://doi.org/10.1146/annurev-genom-031714-125740">types of mutations</a> occur spontaneously or from exposure to hazards like radiation and chemicals.</p>
<p>In a single human genome, there are about <a href="https://doi.org/10.1038/nature11396">70 nucleotide changes per generation</a> – minuscule in a genome made up of six billion letters. But in aggregate, over many generations, these changes lead to substantial evolutionary variation.</p>
<p>Scientists can use mutations to estimate the timing of branches in our evolutionary tree. First they compare the DNA sequences of two individuals or species, counting the neutral differences that don’t alter one’s chances of survival and reproduction. Then, knowing the rate of these changes, they can calculate the time needed to accumulate that many differences. This tells them how long it’s been since the individuals shared ancestors.</p>
<p>Comparison of DNA between you and your sibling would show relatively few mutational differences because you share ancestors – mom and dad – just one generation ago. However, there are millions of differences between <a href="https://doi.org/10.1038/nature04072">humans and chimpanzees</a>; our last common ancestor lived over six million years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=237&fit=crop&dpr=1 600w, https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=237&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=237&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=298&fit=crop&dpr=1 754w, https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=298&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/164351/original/image-20170406-16660-iq0fym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=298&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bits of the chromosomes from your mom and your dad recombine as your DNA prepares to be passed on.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/phases-meiosis-1-172528943">Chromosomes image via www.shutterstock.com.</a></span>
</figcaption>
</figure>
<p><a href="https://doi.org/10.1038/nrg1947">Recombination</a>, also known as crossing-over, is the other main way DNA accumulates changes over time. It leads to shuffling of the two copies of the genome (one from each parent), which are bundled into chromosomes. During recombination, the corresponding (homologous) chromosomes line up and exchange segments, so the genome you pass on to your children is a mosaic of your parents’ DNA.</p>
<p>In humans, <a href="https://doi.org/10.1038/nature09525">about 36 recombination events</a> occur per generation, one or two per chromosome. As this happens every generation, segments inherited from a particular individual get broken into smaller and smaller chunks. Based on the size of these chunks and frequency of crossovers, geneticists can estimate how long ago that individual was your ancestor.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=699&fit=crop&dpr=1 600w, https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=699&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=699&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=879&fit=crop&dpr=1 754w, https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=879&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/164352/original/image-20170406-16665-1ykda9r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=879&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Gene flow between divergent populations leads to chromosomes with mosaic ancestry. As recombination occurs in each generation, the bits of Neanderthal ancestry in modern human genomes becomes smaller and smaller over time.</span>
<span class="attribution"><span class="source">Bridget Alex</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Building timelines based on changes</h2>
<p>Genetic changes from mutation and recombination provide two distinct clocks, each suited for dating different evolutionary events and timescales.</p>
<p>Because mutations accumulate so slowly, this clock works better for very ancient events, like evolutionary splits between species. The recombination clock, on the other hand, ticks at a rate appropriate for dates within the last 100,000 years. These “recent” events (in evolutionary time) include gene flow between distinct human populations, the rise of beneficial adaptations or the emergence of genetic diseases.</p>
<p>The case of Neanderthals illustrates how the mutation and recombination clocks can be used together to help us untangle complicated ancestral relationships. Geneticists estimate that there are 1.5-2 million mutational differences between Neanderthals and modern humans. Applying the mutation clock to this count suggests the groups initially split between <a href="https://doi.org/10.1038/nature12886">750,000 and 550,000 years ago</a>.</p>
<p>At that time, a population – the common ancestors of both human groups – separated geographically and genetically. Some individuals of the group migrated to Eurasia and over time evolved into Neanderthals. Those who stayed in Africa became anatomically modern humans. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/164194/original/image-20170405-14620-3re7gz.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">An evolutionary tree displays the divergence and interbreeding dates that researchers estimated with molecular clock methods for these groups.</span>
<span class="attribution"><span class="source">Bridget Alex</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>However, their interactions were not over: Modern humans eventually spread to Eurasia and mated with Neanderthals. Applying the recombination clock to Neanderthal DNA retained in present-day humans, researchers estimate that the <a href="http://doi.org/10.1073/pnas.1514696113">groups interbred between 54,000 and 40,000 years ago</a>. When scientists analyzed a <em>Homo sapiens</em> fossil, known as Oase 1, who lived around 40,000 years ago, they found large regions of Neanderthal ancestry embedded in the Oase genome, suggesting that Oase had a <a href="http://doi.org/10.1038/nature14558">Neanderthal ancestor just four to six generations ago</a>. In other words, Oase’s great-great-grandparent was a Neanderthal. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=235&fit=crop&dpr=1 600w, https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=235&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=235&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=295&fit=crop&dpr=1 754w, https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=295&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/164193/original/image-20170405-14626-lvvz51.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=295&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Comparing chromosome 6 from the 40,000-year-old Oase fossil to a present-day human. The blue bands represent segments of Neanderthal DNA from past interbreeding. Oase’s segments are longer because he had a Neanderthal ancestor just 4–6 generations before he lived, based on estimates using the recombination clock.</span>
<span class="attribution"><span class="source">Bridget Alex</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>The challenges of unsteady clocks</h2>
<p>Molecular clocks are a mainstay of evolutionary calculations, not just for humans but for all forms of living organisms. But there are some complicating factors.</p>
<p>The main challenge arises from the fact that mutation and recombination rates have not remained constant over human evolution. The rates themselves are evolving, so they vary over time and may differ between species and even across human populations, albeit fairly slowly. It’s like trying to measure time with a clock that ticks at different speeds under different conditions.</p>
<p>One issue relates to a gene called <em>Prdm9</em>, which determines the location of those DNA crossover events. Variation in this gene in humans, chimpanzees and mice has been shown <a href="https://doi.org/10.1126/science.1183439">to alter recombination hotspots</a> – short regions of high recombination rates. Due to the evolution of <em>Prdm9</em> and hotspots, the fine-scale recombination rates <a href="https://doi.org/10.1126/science.1216872">differ between humans and chimps</a>, and <a href="https://doi.org/10.1038/nature10336">possibly also between Africans and Europeans</a>. This implies that over different timescales and across populations, the recombination clock ticks at <a href="http://www.nature.com/nrg/journal/v8/n1/execsumm/nrg1947.html">slightly different rates</a> as hotspots evolve.</p>
<p>Another issue is that mutation rates vary by sex and age. As fathers get older, they transmit <a href="https://doi.org/10.1038/ng.3597">a couple extra mutations to their offspring per year</a>. The sperm of older fathers has undergone more rounds of cell division, so more opportunities for mutations. Mothers, on the other hand, <a href="https://doi.org/10.1038/ng.3597">transmit fewer mutations</a> (about 0.25 per year) as a female’s eggs are mostly formed all at the same time, before her own birth. Mutation rates also <a href="https://doi.org/10.1073/pnas.1600374113">depend on factors like</a> onset of puberty, age at reproduction and rate of sperm production. These life history traits vary across living primates and probably also differed between extinct species of human ancestors.</p>
<p>Consequently, over the course of human evolution, the <a href="https://doi.org/10.1038/nrg3295">average mutation rate seems to have slowed</a> significantly. The average rate over millions of years since the split of humans and chimpanzees has been estimated as <a href="https://doi.org/10.1038/nature04072">about 1x10⁻⁹ mutations per site per year</a> – or roughly six altered DNA letters per year. This rate is determined by dividing the number of nucleotide differences between humans and other apes by the date of their evolutionary splits, as inferred from fossils. It’s like calculating your driving speed by dividing distance traveled by time passed. But when geneticists directly measure nucleotide differences between living parents and children (using human pedigrees), the mutation rate is half the other estimate: <a href="https://doi.org/10.1038/nature11396">about 0.5x10⁻⁹ per site per year</a>, or only about three mutations per year. </p>
<p>For the divergence between Neanderthals and modern humans, the slower rate provides an estimate between 765,000-550,000 years ago. The faster rate, however, would suggest half that age, or 380,000-275,000 years ago: a big difference.</p>
<p>To resolve the question of which rates to use when and on whom, researchers have been developing new molecular clock methods, which address the challenges of evolving mutation and recombination rates.</p>
<h2>New approaches for better dating</h2>
<p>One approach is to focus on mutations that arise at a steady rate regardless of sex, age and species. This may be the case for a special type of mutation that geneticists call <a href="http://www.nature.com/nature/journal/v287/n5782/abs/287560a0.html">CpG transitions</a> by which the C nucelotides spontaneously become T’s. Because CpG transitions mostly do not result from DNA copying errors during cell division, their rates should be mainly independent of life history variables – and presumably more uniform over time. </p>
<p>Focusing on CpG transitions, geneticists recently estimated the split between humans and chimps to have occurred <a href="https://doi.org/10.1073/pnas.1600374113">between 9.3 and 6.5 million years ago</a>, which agrees with the age expected from fossils. While in comparisons across species, these mutations seem to happen more like clockwork than other types, they are still not completely steady.</p>
<p>Another approach is to develop models that adjust molecular clock rates based on sex and other life history traits. Using this method, researchers <a href="https://doi.org/10.1073/pnas.1515798113">calculated a chimp-human divergence</a> consistent with the CpG estimate and fossil dates. The drawback here is that, when it comes to ancestral species, we can’t be sure of life history traits, like age at puberty or generation length, leading to some uncertainty in the estimates.</p>
<p>The most direct solution comes from analyses of ancient DNA recovered from fossils. Because the fossil specimens are independently dated by geologic methods, geneticists can use them to calibrate the molecular clocks for a given time period or population.</p>
<p>This strategy recently resolved the debate over the timing of our divergence with Neanderthals. In 2016, geneticists extracted ancient DNA from <a href="https://doi.org/10.1038/nature17405">430,000-year-old fossils that were Neanderthal ancestors</a>, after their lineage split from <em>Homo sapiens</em>. Knowing where these fossils belong in the evolutionary tree, geneticists could confirm that for this period of human evolution, the slower molecular clock rate of 0.5x10⁻⁹ provides accurate dates. That puts the Neanderthal-modern human split between 765,000 to 550,000 years ago.</p>
<p>As geneticists sort out the intricacies of molecular clocks and sequence more genomes, we’re poised to learn more than ever about human evolution, directly from our DNA.</p><img src="https://counter.theconversation.com/content/65606/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bridget Alex has received research funding from the National Science Foundation (NSF).</span></em></p><p class="fine-print"><em><span>Priya Moorjani is supported by the NIH Ruth L. Kirschstein National Research Service Postdoctoral fellowship (grant number F32 GM115006-02).</span></em></p>
How do scientists figure out when evolutionary events – like species splitting away from a common ancestor – happened? It turns out our DNA is a kind of molecular clock, keeping time via genetic changes.
Bridget Alex, Postdoctoral College Fellow, Department of Human Evolutionary Biology, Harvard University
Priya Moorjani, Postdoctoral Research Fellow in Biological Sciences, Columbia University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/45066
2015-07-22T16:25:25Z
2015-07-22T16:25:25Z
Discovery of ‘oldest’ Qur'an fragments could resolve enigmatic history of holy text
<figure><img src="https://images.theconversation.com/files/89378/original/image-20150722-1426-1b8rpsv.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">Cadbury Research Library, University of Birmingham</span></span></figcaption></figure><p>For the world’s <a href="http://www.pewforum.org/2011/01/27/the-future-of-the-global-muslim-population/">1.6 billion</a> Muslims, the idea that the Qur'an is a seventh century text disseminated by Islam’s founder, the Prophet Muhammad, is neither news, nor particularly controversial. </p>
<p>But in academia the history of this holy text is much more opaque. For researchers in Islamic studies, historical evidence dating the Qur'an back to Islam’s foundational era has proved elusive. This has led to hotly contested academic debates about the early or late canonisation of the Qur'an, with a small handful of scholars claiming that the book is a product of a much later (mid-eighth century and after) age of compilation or even confabulation, when ‘Abbasid-era scholars rationalised and expanded the Muslim religious corpus.</p>
<p>Recent scholarly work on early manuscript fragments of the Qur'an such as those discovered in <a href="http://www.historytoday.com/scott-macmillan/sanaa-city-book">Sana‘a, Yemen in 1972</a> gave us portions of Qur'anic text carbon-dated to a few years after the Qur'an was officially standardised by one of Muhammad’s early successors, the caliph ‘Uthman, in around 650 CE. But there has been little clinching evidence to settle the debate about the dating of the text from a scholarly rather than devotional perspective.</p>
<h2>A new discovery</h2>
<p>But this picture seems to have <a href="http://www.bbc.co.uk/news/business-33436021">changed overnight</a>. Two Qur'an fragments unknowingly held since 1936 in the University of Birmingham’s manuscript collection have been definitively dated to the era of Muhammad’s life or a little later. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/C-HDFiC2boQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The writing of the two folios (with text corresponding to chapters 18-20 in the modern Qur'an) has been placed somewhere between 568 and 645 CE, which is very close to the conventional dating offered for the Prophet’s ministry, 610-632 CE. Given the more than 95% accuracy of the carbon dating involved, carried out at the Oxford University Radiocarbon Accelerator Unit, this discovery indicates that these fragments are in all probability contemporary with the Prophet himself.</p>
<p>No wonder that the University of Birmingham, and the city as a whole, has welcomed the news with excitement and pride. There seems some poetic justice in the fact that a city that is home to one of the most multicultural communities in the world (described without irony on Fox News as a “<a href="http://www.bbc.co.uk/news/uk-england-30773297">no-go area</a>” for non-Muslims) should now, as it surely will, become a veritable Mecca for both non-Muslims and Muslims eager to examine for themselves these almost 1,400 year-old pages, which are offered in a clear, legible, even beautiful hand.</p>
<h2>Handwriting hesitation</h2>
<p>Certainly, the discovery will have its detractors, and no doubt these will be of two kinds. First, from those historians who are cautious, even sceptical about carbon dating as a tool of evidence. </p>
<p>On the whole, palaeography (the study of handwriting) and carbon dating have worked side-by-side to offer a clearer picture than ever of the date-range of various textual materials for ancient and medieval history. But historians schooled in palaeography or philology (the study of historical language) can often find the evidence furnished by carbon dating to be unfeasibly early. There have been clear instances of carbon dating specifying a timeframe which is undermined by a study of language (such as dialect or idiom), of script and of what I will call circumstantial evidence, namely what is known from written histories or from archaeological remains about the spread of texts and of ideas. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/89363/original/image-20150722-1447-qac8gr.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 fragments.</span>
<span class="attribution"><span class="source">Cadbury Research Library, University of Birmingham</span></span>
</figcaption>
</figure>
<p>French scholar François Déroche, for example, <a href="http://www.brill.com/qur-ans-umayyads/">argued in 2014</a> that carbon dating seems to offer too early a time period for the Umayyad-era (661-750 CE) Qur'ans that he has examined. Such discrepancies can usually be attributed to the fact that carbon dating provides a reasonably accurate assessment of the date of the medium of writing – for example, the death date of an animal whose skin is used for writing on – rather than the date when of the writing itself. Yet the widespread use of the method for dating ancient and medieval texts and artifacts bears witness to its importance as a powerful tool for establishing a reasonable range of dates for any given object. </p>
<h2>Hardwired skeptics</h2>
<p>The other group who may find fault with this discovery are those writers for whom “Islam” is a collection of ideas and strictures developed in a much later (post-conquest) era and projected back on to the seventh century. For such hardwired sceptics, it may be that no historical evidence carries the power to shift their convictions. This new discovery may be dismissed by such voices as part of the global conspiracy to give Islam’s self-created narrative more credence than it deserves.</p>
<p>But for academic historians of early Islam, the early stabilisation of Qur'anic text is one of the few areas which a broad spectrum of scholars agree on. In the words of the recently departed historian Patricia Crone, a widely acknowledged expert on early and medieval Islam:</p>
<blockquote>
<p>We can be reasonably sure that the Qur'an is a collection of utterances that [Muhammad] made in the belief that they had been revealed to him by God … [He] is not responsible for the arrangement in which we have them. They were collected after his death – how long after is controversial.</p>
</blockquote>
<p>It is this last point of controversy that the Birmingham discovery illuminates. Clearly, Qur'anic verses with a very close match to the version we have today were being transcribed during or soon after the Prophet’s lifetime. So historians of early Islam have good reason to feel excited, if not gratified, by this discovery.</p><img src="https://counter.theconversation.com/content/45066/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fozia Bora 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>
Hotly-contested debates about the early or late canonisation of the Qur'an may be resolved by a recent discovery.
Fozia Bora, Lecturer in Middle Eastern History and Islamic History, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/23059
2014-02-25T12:52:01Z
2014-02-25T12:52:01Z
What Cold War nuclear weapons can tell us about art fraud
<figure><img src="https://images.theconversation.com/files/42195/original/f78fjbdv-1392984994.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">'Nope, definitely not a Caravaggio.'</span> <span class="attribution"><a class="source" href="http://www.flickr.com/photos/30835738@N03/7936190234/sizes/l/">International Campaign to Abolish Nuclear Weapons</a></span></figcaption></figure><p>The identification of fakes and forgeries is a basic issue that has always raised controversy. This is unsurprising, of course – the enormous sums garnered by top paintings would turn to dust as soon as a question as to their authenticity arose.</p>
<p>To determine whether a painting is original or not, the expertise of critics and art historians is of course central. They are the only ones who know all the details about the technique of a painter, his or her way of drawing, the colours they used and the typical ideas and subjects represented. </p>
<p>But often forgeries are so good that this kind of analysis reaches an insurmountable wall. And here, science plays a major role.</p>
<p>Nuclear techniques such as <a href="http://www.oxford-instruments.com/businesses/industrial-products/industrial-analysis/xrf">X-ray Fluorescence</a> and <a href="http://www.mrsec.harvard.edu/cams/PIXE.html">Particle Induced X-ray Emission</a> allow us to analyse and reconstruct the exact composition of pigments used by the artist. </p>
<p>These methods are non-destructive and non-invasive, and have almost become a routine tool to help art historians and restorers. Analysis of the different pigments used may reveal that one or more are anachronistic to the alleged date of painting. This would suggest that the artwork may be a fake if the investigated areas have not been previously subjected to pictorial retouching. </p>
<p>But often it is necessary to date a painting with much more accuracy, something only possible with <a href="http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm">radiocarbon dating</a>, using an instrument known as <a href="http://www.ph.surrey.ac.uk/partphys/chapter4/ElectroAcc.html">electrostatic accelerator</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/41730/original/ntd6ynwc-1392668130.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Tandem electrostatic accelerator installed at INFN-LABEC, Florence.</span>
</figcaption>
</figure>
<p>The potential of this is maximised if dating something from the past 70 years or so. This is because there has been an enormous variation in carbon concentration in the atmosphere during this time. Since 1955, the <sup>14</sup>C concentration in the atmosphere started to increase dramatically as a consequence of the many nuclear weapon tests performed in air during the Cold War. </p>
<p>The effect was so significant that the concentration of the substance almost doubled in less than ten years, reaching its maximum in 1963-1965. Then, the <a href="http://www.history.com/this-day-in-history/nuclear-test-ban-treaty-signed">Nuclear Ban Treaty</a> signed in 1963 stopped all the nuclear experiments except those performed underground. The <sup>14</sup>C concentration then started to decrease. </p>
<p>Nowadays, the concentration has almost come back to the typical amount seen in the years before 1955. We usually refer to this trend of radiocarbon concentration as the “Bomb Peak”. All living organisms from 1955 time will have had a <sup>14</sup>C content higher than all the organisms that lived before. So a cotton plant that grew in that period will have had a higher <sup>14</sup>C content than one that didn’t.</p>
<p>And so, if we measure the amount of radiocarbon in a canvas made from that cotton plant we can easily conclude that the canvas was manufactured after 1955. At the Istituto Nazionale di Fisica Nucleare (INFN), we exploited this idea to <a href="http://www.infn.it/comunicazione/index.php?option=com_content&view=article&id=388:physicists-at-the-infn-resolve-the-enigma-of-a-painting-by-leger&catid=38&Itemid=862&lang=it">finally solve an enigma</a> that had remained unresolved for more than 30 years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=758&fit=crop&dpr=1 600w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=758&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=758&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=953&fit=crop&dpr=1 754w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=953&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/41729/original/fsbsz2dc-1392667501.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=953&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The painting thought to belong to the series Contrastes de Formes by F. Léger.</span>
<span class="attribution"><span class="source">Guggenheim Venice</span></span>
</figcaption>
</figure>
<p>In the late 1960s, Peggy Guggenheim bought a painting on canvas that was supposed to be part of the series <a href="http://www.guggenheim.org/new-york/collections/collection-online/artwork/2437">Contrastes de Formes</a>, painted in the period 1913-14 by the French artist <a href="http://www.britannica.com/EBchecked/topic/334999/Fernand-Leger">Fernand Léger</a>. But after some years, the art critic Douglas Cooper questioned the authenticity of the painting. So, even though the artwork was still in the <a href="http://www.guggenheim-venice.it/inglese/default.html">Peggy Guggenheim Collection</a> in Venice, it was never shown to the public. </p>
<p>Thanks to the collaboration with the Guggenheim Museum we dated a small canvas sample taken from the excess fabric around the frame. We measured the radiocarbon concentration, comparing it to the Bomb Peak trend. The result was conclusive: the canvas – or, the cotton plants used to make it – had a high radiocarbon concentration and was dated to 1959 or 1962, at least four years after the death of Léger. </p>
<p>So, nuclear physics proved that the painting was not authentic, nor was it a later copy by Léger himself, as some had suggested. The result of the radiocarbon measurement was unquestionable. This was the first time that the Bomb Peak has been used to discover a forgery of a modern artwork. </p><img src="https://counter.theconversation.com/content/23059/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mariaelena Fedi 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 identification of fakes and forgeries is a basic issue that has always raised controversy. This is unsurprising, of course – the enormous sums garnered by top paintings would turn to dust as soon as…
Mariaelena Fedi, Researcher, Italian Institute for Nuclear Physics
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/9690
2012-11-28T03:18:00Z
2012-11-28T03:18:00Z
Explainer: what is radiocarbon dating and how does it work?
<figure><img src="https://images.theconversation.com/files/16003/original/nx8pdx2c-1349052868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Make no bones about it, radiocarbon dating has transformed our understanding of the past.</span> <span class="attribution"><span class="source">Wessex Archaeology</span></span></figcaption></figure><p>Radiocarbon dating has transformed our understanding of the past 50,000 years. <a href="http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1960/libby-bio.html">Professor Willard Libby</a> produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts. </p>
<p>Radiocarbon dating works by comparing the three different <a href="http://www.colorado.edu/physics/2000/isotopes/index.html">isotopes</a> of carbon. Isotopes of a particular element have the same number of <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html#c1">protons</a> in their nucleus, but different numbers of <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html#c3">neutrons</a>. This means that although they are very similar chemically, they have different masses. </p>
<p>The total mass of the isotope is indicated by the numerical superscript. While the lighter isotopes <sup>12</sup>C and <sup>13</sup>C are stable, the heaviest isotope <sup>14</sup>C (radiocarbon) is radioactive. This means its nucleus is so large that it is unstable.</p>
<p>Over time <sup>14</sup>C decays to nitrogen (<sup>14</sup>N). Most <sup>14</sup>C is produced in the upper atmosphere where neutrons, which are produced by <a href="https://theconversation.com/an-extragalactic-mystery-where-do-high-energy-cosmic-rays-come-from-6623">cosmic rays</a>, react with <sup>14</sup>N atoms.</p>
<p>It is then oxidised to create <sup>14</sup>CO<sub>2</sub>, which is dispersed through the atmosphere and mixed with <sup>12</sup>CO<sub>2</sub> and <sup>13</sup>CO<sub>2</sub>. This CO<sub>2</sub> is used in photosynthesis by plants, and from here is passed through the food chain (see figure 1, below).</p>
<p>Every plant and animal in this chain (including us!) will therefore have the same amount of <sup>14</sup>C compared to <sup>12</sup>C as the atmosphere (the <sup>14</sup>C:<sup>12</sup>C ratio). </p>
<h2>Dating history</h2>
<p>When living things die, tissue is no longer being replaced and the radioactive decay of <sup>14</sup>C becomes apparent. Around 55,000 years later, so much <sup>14</sup>C has decayed that what remains can no longer be measured.</p>
<p>Radioactive decay can be used as a “clock” because it is unaffected by physical (e.g. temperature) and chemical (e.g. water content) conditions. In 5,730 years half of the <sup>14</sup>C in a sample will decay (see figure 1, below).</p>
<p>Therefore, if we know the <sup>14</sup>C:<sup>12</sup>C ratio at the time of death and the ratio today, we can calculate how much time has passed. Unfortunately, neither are straightforward to determine.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=734&fit=crop&dpr=1 600w, https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=734&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=734&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=922&fit=crop&dpr=1 754w, https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=922&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/17628/original/pw7f73g3-1352934165.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=922&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Figure 1: Carbon dioxide is used in photosynthesis by plants, and from here is passed through the food chain.</span>
</figcaption>
</figure>
<p>The amount of <sup>14</sup>C in the atmosphere, and therefore in plants and animals, has not always been constant. For instance, the amount varies according to how many cosmic rays reach Earth. This is affected by solar activity and the <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html">earth’s magnetic field</a>. </p>
<p>Luckily, we can measure these fluctuations in samples that are dated by other methods. Tree rings can be counted and their radiocarbon content measured. From these records a “<a href="http://en.wikipedia.org/wiki/Calibration_curve">calibration curve</a>” can be built (see figure 2, below).</p>
<p>A huge amount of work is currently underway to extend and improve the calibration curve. In 2008 we could only calibrate radiocarbon dates until 26,000 years. Now the curve extends (tentatively) to 50,000 years.</p>
<h2>Dating advances</h2>
<p>Radiocarbon dates are presented in two ways because of this complication. The uncalibrated date is given with the unit BP (radiocarbon years before 1950).</p>
<p>The calibrated date is also presented, either in BC or AD or with the unit <a href="http://en.wikipedia.org/wiki/Before_Present">calBP</a> (calibrated before present - before 1950). The calibrated date is our “best estimate” of the sample’s actual age, but we need to be able to return to old dates and recalibrate them because new research is continually used to update the calibration curve.</p>
<p>The second difficulty arises from the extremely low abundance of <sup>14</sup>C. Only 0.0000000001% of the carbon in today’s atmosphere is <sup>14</sup>C, making it incredibly difficult to measure and extremely sensitive to contamination. </p>
<p>In the early years of radiocarbon dating a product’s decay was measured, but this required huge samples (e.g. half a human femur). Many labs now use an <a href="http://www.physics.purdue.edu/primelab/introduction/ams.html">Accelerator Mass Spectrometer</a> (AMS), a machine that can detect and measure the presence of different isotopes, to count the individual <sup>14</sup>C atoms in a sample. </p>
<p>This method requires less than 1g of bone, but few countries can afford more than one or two AMSs, which cost more than A$500,000. Australia has two machines dedicated to radiocarbon analysis, and they are out of reach for much of the developing world. </p>
<p>In addition, samples need to be thoroughly cleaned to remove carbon contamination from glues and soil before dating. This is particularly important for very old samples. If 1% of the carbon in a 50,000 year old sample is from a modern contaminant, the sample will be dated to around 40,000 years. </p>
<p>Because of this, radiocarbon chemists are continually developing new methods to more effectively clean materials. These new techniques can have a dramatic effect on chronologies. With the development of a new method of cleaning charcoal called <a href="http://www.sciencedirect.com/science/article/pii/S1871101412000283">ABOx-SC</a>, <a href="http://www.jcu.edu.au/ees/staff/academic/JCUPRD_048039.html">Michael Bird</a> helped to push back the date of arrival of the <a href="http://www-personal.une.edu.au/%7Epbrown3/Gillespie02.pdf">first humans in Australia</a> by more than 10,000 years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=553&fit=crop&dpr=1 600w, https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=553&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=553&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=695&fit=crop&dpr=1 754w, https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=695&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/17629/original/94dfp9w9-1352934213.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=695&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Figure 2: a calibration curve showing radiocarbon content over time.</span>
</figcaption>
</figure>
<h2>Establishing dates</h2>
<p>Moving away from techniques, the most exciting thing about radiocarbon is what it reveals about our past and the world we live in. Radiocarbon dating was the first method that allowed archaeologists to place what they found in chronological order without the need for written records or coins. </p>
<p>In the 19th and early 20th century incredibly patient and careful archaeologists would link pottery and stone tools in different geographical areas by similarities in shape and patterning. Then, by using the idea that the styles of objects evolve, becoming increasing elaborate over time, they could place them in order relative to each other - a technique called <a href="http://archaeology.about.com/od/dating/ss/seriation.htm">seriation</a>. </p>
<p>In this way large domed tombs (known as tholos or <a href="en.wikipedia.org/wiki/Beehive_tomb">beehive tombs</a>) in Greece were thought to predate <a href="http://www.maeshowe.co.uk/maeshoweabout.html">similar structures</a> in the Scottish Island of Maeshowe. This supported the idea that the classical worlds of Greece and Rome were at the centre of all innovations. </p>
<p>Some of the first radiocarbon dates produced showed that the Scottish tombs were thousands of years older than those in Greece. The barbarians of the north were capable of designing complex structures similar to those in the classical world.</p>
<p>Other high profile projects include the dating of the <a href="http://www.shroud.com/nature.htm">Turin Shroud</a> to the medieval period, the dating of the <a href="http://www.usc.edu/dept/LAS/wsrp/educational_site/dead_sea_scrolls/">Dead Sea Scrolls</a> to around the time of Christ, and the somewhat controversial dating of the spectacular rock art at <a href="http://www.bradshawfoundation.com/chauvet/chauvet_cave_art.php">Chauvet Cave</a> to c.38,000 calBP (c.32,000 BP) – thousands of years earlier than expected. </p>
<p>Radiocarbon dating has also been used to date the extinction of the <a href="http://www.amnh.org/science/biodiversity/extinction/Day1/bytes/StuartPres.html">woolly mammoth</a> and contributed to the debate over whether modern <a href="https://theconversation.com/sex-with-our-evolutionary-cousins-whats-not-to-love-3465">humans and Neanderthals met</a>.</p>
<p>But <sup>14</sup>C is not just used in dating. Using the same techniques to measure <sup>14</sup>C content, we can examine ocean circulation and trace the movement of drugs around the body. But these are topics for separate articles.</p>
<p><em>If you’d like to learn more about radiocarbon dating, <a href="http://www.c14dating.com">www.c14dating.com</a> is an excellent starting point.</em>
<br>
<em>See more <a href="https://theconversation.com/topics/explainer">Explainer articles</a> on The Conversation.</em></p><img src="https://counter.theconversation.com/content/9690/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rachel Wood 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>
Radiocarbon dating has transformed our understanding of the past 50,000 years. Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts…
Rachel Wood, Research Officer, Radiocarbon Facility, Australian National University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/4168
2011-11-08T19:41:31Z
2011-11-08T19:41:31Z
Did climate cause the extinction of the Ice Age megafauna?
<figure><img src="https://images.theconversation.com/files/5270/original/Picture_Beringia_GeorgeTeichmann.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The demise of the woolly mammoth could teach us much about our effect on other species.</span> <span class="attribution"><span class="source">George Teichmann</span></span></figcaption></figure><p>When we think of the last 50,000 years of prehistory, particularly the “Ice Age”, extinct species such as the <a href="http://www.bbc.co.uk/nature/life/Woolly_mammoth">woolly mammoth</a> and <a href="http://www.rhinos-irf.org/woolly/">woolly rhinoceros</a> often spring to mind. </p>
<p>Did humans bring about the extinction of these large animals (megafauna)? Or did they succumb to the impacts of a changing climate? And how did other megafauna, such as the elephant and reindeer, manage to survive?</p>
<p>These questions have troubled biologists for the past two centuries. They have also been the subject of heated debate in Australia, which has lost impressive species such as the <a href="http://australianmuseum.net.au/Diprotodon-optatum">diprotodon</a> (a hippo-sized wombat) and giant versions of modern-day marsupials.</p>
<p>For many of the species that went extinct in the past few hundred years – including the <a href="http://terranature.org/moa.htm">New Zealand moa</a> and the <a href="http://www.bbc.co.uk/nature/life/Elephant_bird">Malagasy elephant birds</a> – there is overwhelming evidence that human activity caused their demise. </p>
<p>In other parts of the world, megafaunal extinctions roughly coincided with the arrival of humans. But coincidence is not proof of causation. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=849&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=849&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=849&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1067&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1067&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5276/original/Moa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1067&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Moa was a large flightless bird endemic to New Zealand.</span>
</figcaption>
</figure>
<p>The disagreement has persisted because researchers have had differing interpretations of scant evidence. Many of the megafaunal species went extinct long ago, leaving few traces in the fossil and archaeological records. </p>
<p>Thanks to the huge progress in methods for genetic analysis, it is now possible to look at populations of extinct animals by studying DNA from ancient specimens. This DNA contains signatures of past changes in population size. These can be used to look at ancient populations and to see how they changed through time.</p>
<h2>Bringing the evidence together</h2>
<p><a href="http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10574.html">In an article recently published in Nature</a>, my colleagues and I studied megafaunal extinctions by focusing on six species. These included the woolly mammoth, woolly rhinoceros, steppe bison, muskox, wild horse, and reindeer.</p>
<p>We chose to look at the Northern Hemisphere, where the permafrost has preserved huge numbers of specimens for us to analyse. </p>
<p>Our team of geneticists, archaeologists, and zoologists assembled the largest data set of its kind. The study involved nearly 10,000 <a href="http://en.wikipedia.org/wiki/Radiocarbon_dating">radiocarbon dates</a> and over 800 DNA sequences. </p>
<p>Apart from reconstructing the populations of the six species, we were able to evaluate the likely effects of humans by estimating their geographical overlap with the megafauna. The interaction between humans and the six species was assessed by the presence of megafaunal remains in archaeological sites.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=354&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=354&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=354&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=445&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=445&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5275/original/diprotodon.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=445&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The three-metre-long Diprotodon went extinct roughly 46,000 years ago.</span>
</figcaption>
</figure> <p></p>
<p>Using estimates of the timing of changes in populations, we were able to examine the impact of changes in climate. For example, the population size of North American bison experienced a drastic decline during the height of the last Ice Age, when their habitat would have been greatly reduced.</p>
<p>We found that the decline of the woolly rhinoceros and musk ox could be explained entirely by changes in climate. It is likely that human expansion contributed to the demise of the steppe bison and wild horse – the two most common megafaunal species found in archaeological sites.</p>
<p>The reindeer has thrived to the modern day, but we could not find a clear cause for the extinction of the woolly mammoth.</p>
<p>Overall, our study shows the six species varied considerably in their responses to human impacts and changing climate. This suggests the causes of extinction can be complex and probably differ among species.</p>
<h2>Megafaunal extinctions in Australia</h2>
<p>It is unlikely we will ever be able to conduct such a comprehensive study on the extinctions in Australia. Good specimens are scarce and DNA degrades quickly in Australian conditions. </p>
<p><figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=799&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=799&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=799&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1004&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1004&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5274/original/elephant_bird.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1004&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Before extinction, the elephant bird lived only in Madagascar.</span>
</figcaption>
</figure>
</p><p>It has been difficult to place reliable dates on the megafaunal extinctions in Australia. This is because human colonisation and many of the extinction events occurred around 50,000 years ago, which is at the upper limit of radiocarbon dating. </p>
<p>The arrival of humans signalled a drastic change in the Australian environment, not just because of hunting, but also because of the extensive use of fire. This would have altered vegetation and the distributions of habitats. </p>
<p>Our chances of determining the causes of these extinctions will improve with progress in dating methods and ancient DNA analysis. Further refinement of the timing of human arrival in Australia will also be helpful.</p>
<h2>Lessons for the future</h2>
<p>Humans are now modifying the environment and the atmosphere at an alarming pace. This raises grave concerns about the future of the planet’s biodiversity. Many of the present-day megafaunal species are under threat and require careful management. </p>
<p>If there are any lessons to be learnt from our study of the megafaunal extinctions, it is that different species respond differently to the pressures of human hunting and encroachment, habitat redistribution, and changing climate.</p>
<p>This presents a challenge for conservation efforts because it can be difficult to predict the course of modern animal populations.</p><img src="https://counter.theconversation.com/content/4168/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Ho receives funding from the Australian Research Council.</span></em></p>
When we think of the last 50,000 years of prehistory, particularly the “Ice Age”, extinct species such as the woolly mammoth and woolly rhinoceros often spring to mind. Did humans bring about the extinction…
Simon Ho, Associate Professor, School of Biological Science, University of Sydney
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