tag:theconversation.com,2011:/uk/topics/megafaunal-extinction-6284/articlesMegafaunal extinction – The Conversation2023-11-16T19:03:39Ztag:theconversation.com,2011:article/2163582023-11-16T19:03:39Z2023-11-16T19:03:39ZGiant eagles and scavenging vultures shared the skies of ancient Australia<figure><img src="https://images.theconversation.com/files/555992/original/file-20231026-21-xbm5tb.jpg?ixlib=rb-1.1.0&rect=11%2C0%2C7507%2C3686&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A flock of vultures (_Cryptogyps lacertosus_) and Australian ravens watch and wait (left), as an adult eagle _Dynatoaetus pachyosteus_ feeds on the carcass of a dead _Diprotodon_ (centre), while a younger bird seeks to join in. In the nearby treetops, a second adult _D. pachyosteus_ feeds its hungry chick (right).</span> <span class="attribution"><span class="source">John Barrie</span></span></figcaption></figure><p>Today, Australia is home to 17 species of hawks and eagles. But the fossil record shows some other, rather special raptors were present in the relatively recent past. </p>
<p>Tens of thousands of years ago, Australia was home to species such as <a href="https://theconversation.com/australias-extinct-giant-eagle-was-big-enough-to-snatch-koalas-from-trees-200341"><em>Dynatoaetus gaffae</em>, the largest eagle ever to have lived in Australia</a>, and <a href="https://theconversation.com/it-was-long-thought-these-fossils-came-from-an-eagle-turns-out-they-belong-to-the-only-known-vulture-species-from-australia-187017"><em>Cryptogyps lacertosus</em>, our only known vulture</a>. </p>
<p>Now, we have discovered another ancient eagle shared the skies with these prehistoric predators. In a <a href="https://doi.org/10.1080/03115518.2023.2268780">new paper in the journal Alcheringa</a>, we describe the formidable <em>Dynatoaetus pachyosteus</em>, based on fossils found in the Naracoorte Caves in South Australia.</p>
<h2>A new eagle unearthed</h2>
<p><em>Dynatoaetus pachyosteus</em> (the name means “powerful eagle with thick bones”) lived during the Pleistocene (a time period spanning from 2.5 million to 11,700 years ago). It had a wingspan similar to that of a wedge-tailed eagle, but with much more robust and powerful wings and legs. It was slightly smaller than its cousin, the massive <em>Dynatoaetus gaffae</em>. </p>
<p>This formidable predator would most likely have preyed on medium to large marsupials and birds. It may even have attacked juveniles and weakened individuals of huge megafaunal species like the <a href="https://theconversation.com/fossil-find-reveals-giant-prehistoric-thunder-birds-were-riddled-with-bone-disease-173745">giant flightless bird</a> <em>Genyornis</em>.</p>
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<a href="https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration of an eagle feeding a chick, together with photos of four bones." src="https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556402/original/file-20231028-30-aal6zi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&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">The large extinct eagle <em>Dynatoaetus pachyosteus</em> (left) and comparison of its humerus or upper arm/wing bone (centre) to that of a modern female wedge-tailed eagle (right). Scale bar = 10mm.</span>
<span class="attribution"><span class="source">John Barrie (reconstruction) / Ellen Mather (photos)</span></span>
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<p><em>Dynatoaetus pachyosteus</em> shared the Pleistocene landscape with at least two other large eagles, the huge <em>Dynatoaetus gaffae</em> and the wedge-tailed eagle we know today. For these species to coexist, they would have likely needed to have slightly different ecological roles to avoid outright competition. </p>
<p>“Niche separation” typically occurs by <a href="https://www.nature.com/scitable/knowledge/library/resource-partitioning-and-why-it-matters-17362658/">exploiting different kinds of food or habitats</a>. These three eagles most likely coexisted by specialising in hunting different prey and nesting in different places.</p>
<p>The occurrence of both species of the <em>Dynatoaetus</em> genus in Australia (and nowhere else) has implications for the evolution of eagles. <em>Dynatoaetus gaffae</em> and <em>D. pachyosteus</em> presumably evolved from a common ancestor in Australia that diverged into two species, a process that typically takes a very long time. </p>
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Read more:
<a href="https://theconversation.com/australias-extinct-giant-eagle-was-big-enough-to-snatch-koalas-from-trees-200341">Australia's extinct giant eagle was big enough to snatch koalas from trees</a>
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<p>This suggests the ancestor of this genus was already ensconced on our continent millions of years before the two Pleistocene species arose. <em>Dynatoaetus pachyosteus</em> and <em>D. gaffae</em> together form a rare example of a raptor genus diversifying into multiple species entirely on the Australian continent (what scientists call “endemic evolutionary radiation”). </p>
<p>There are only two raptor genera today restricted to Australia, and both consist of only a single species: <em>Hamirostra</em> (the black-breasted buzzard) and <em>Lophoictinia</em> (the square-tailed kite).</p>
<h2>Primitive vultures of ancient Australia</h2>
<p>Our research has also revealed intriguing new information about another extinct raptor, the vulture <em>Cryptogyps lacertosus</em>. </p>
<p>Fossils from the Green Waterhole (also known as Fossil Cave), in the Tantanoola district near Mt Gambier, give us a more complete picture of this species. We found several paired wing bones, two shoulder bones, a vertebra and a toe bone, all probably from a single individual. </p>
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Read more:
<a href="https://theconversation.com/it-was-long-thought-these-fossils-came-from-an-eagle-turns-out-they-belong-to-the-only-known-vulture-species-from-australia-187017">It was long thought these fossils came from an eagle. Turns out they belong to the only known vulture species from Australia</a>
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<p>The additional bones of <em>Cryptogyps</em> indicate it was a rather primitive vulture, less adapted for the long periods of soaring flight characteristic of modern vultures.</p>
<p>Thanks to the sediment around the fossils, we also have a very precise date of when <em>Cryptogyps</em> was alive. Many of the Green Waterhole fossils were buried in a deposit of calcite rafts – crystals that form on the surface of still bodies of water in caves. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photos of several bones and an illustration of a vulture-like bird" src="https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=689&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=689&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=689&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=866&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=866&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556401/original/file-20231028-24-5h6thl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=866&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">Fossil bones from the wing and shoulder of the extinct vulture <em>Cryptogyps lacertosus</em>, recovered from Green Waterhole, South Australia. Scale bar = 50mm. Life reconstruction top right.</span>
<span class="attribution"><span class="source">Ellen Mather (photos) / John Barrie (reconstruction)</span></span>
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<p>Today, most of the cave is submerged because of a high water table, but in the past, it was mostly dry. A pool of water deeper in the cave was where these calcite rafts formed. </p>
<p>The water was likely what attracted animals into the cave in the first place. These animals then died, and their bones sank to the bottom of the pool along with the calcite rafts. Our team dated these calcite rafts – and thus the entombed <em>Cryptogyps</em> fossils – at approximately 60,000 years old.</p>
<h2>Mammal extinctions affect birds of prey</h2>
<p>When we think of the <a href="https://theconversation.com/did-people-or-climate-kill-off-the-megafauna-actually-it-was-both-127803">mass extinction</a> of Australian megafauna, we tend to think about the demise of large mammals, such as the “giant wombat” <em>Diprotodon optatum</em>, the “marsupial lion” <em>Thylacoleo carnifex</em>, and the giant short-faced kangaroo <em>Procoptodon goliah</em>. Some large reptiles are also commonly recognised as victims: the giant goanna (Megalania) <em>Varanus priscus</em>, the constricting snake <em>Wonambi naracoortensis</em>, and <a href="https://theconversation.com/meet-the-biggest-and-most-bizarre-skink-ever-found-in-australia-it-became-extinct-47-000-years-ago-206764">even a giant armoured skink</a> <em>Tiliqua frangens</em>.</p>
<p>But as we can see from the case of our large eagles and vultures, other groups of animals were also affected. Birds of prey, especially large and scavenging species, <a href="https://www.semanticscholar.org/paper/The-Late-Pleistocene-Continental-Avian-extinction-Tyrberg/6cfc6bfea30c8b5635d5250eede1556c4d654402">went extinct around the world during the Late Pleistocene</a>, their food supply likely affected by the loss of large mammalian species. Australia appears to have been no exception to the rule.</p>
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<a href="https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two photos of eagles in flight, one with a white belly and the other with dark, patterned wings." src="https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556394/original/file-20231028-27-4hz9e1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&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">The wedge-tailed eagle (<em>Aquila audax</em>) and the white-bellied sea eagle (<em>Icthyophaga leucogaster</em>) are the largest birds of prey found in modern Australia.</span>
<span class="attribution"><span class="source">Michael Lee</span></span>
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<p>The new fossils reveal many of Australia’s large birds of prey did not survive the megafaunal extinction event in the Late Pleistocene, roughly 50,000 years ago. The two largest species that managed to persist to the present are the wedge-tailed eagle, which is a generalist hunter found throughout the continent, and the white-bellied sea eagle, which targets fish and has a coastal distribution. </p>
<p>It is likely our three extinct large raptors – two giant eagles and a vulture – were too specialised as hunters and scavengers of megafauna to adapt to a rapidly changing world. Their extinction likely caused a further cascade of effects through the ecosytem: in Asia, for instance, more recent loss of vultures has led to increased populations of scavenging feral dogs and higher prevalance of <a href="https://www.sciencedaily.com/releases/2022/02/220214095744.htm">diseases such as rabies</a>.</p><img src="https://counter.theconversation.com/content/216358/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ellen K. Mather received funding from BirdLife Australia Raptor Group.</span></em></p><p class="fine-print"><em><span>Michael Lee receives funding from the Australian Research Council, Flinders University and the Royal Society of South Australia</span></em></p><p class="fine-print"><em><span>Trevor H. Worthy has received funding from The Australian Research Council for research on fossil birds. He has previously worked for Flinders University and now has an adjunct status there.</span></em></p>New fossils reveal Australia was once home to a much greater diversity of huge eagles and vultures, which died off alongside ‘giant wombats’ and ‘marsupial lions’.Ellen K. Mather, Adjunct Associate Lecturer in Palaeontology, Flinders UniversityMike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders UniversityTrevor H. Worthy, Associate Professor, Vertebrate Palaeontology Group, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2055562023-06-14T12:35:28Z2023-06-14T12:35:28ZForensic evidence suggests Paleo-Americans hunted mastodons, mammoths and other megafauna in eastern North America 13,000 years ago<figure><img src="https://images.theconversation.com/files/528316/original/file-20230525-21-no8djo.jpg?ixlib=rb-1.1.0&rect=556%2C160%2C3570%2C2456&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Animals that shared the landscape with humans disappeared as the ice age ended.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ice_age_fauna_of_northern_Spain_-_Mauricio_Antón.jpg">Mauricio Antón/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The earliest people who lived in North America shared the landscape with huge animals. On any day these hunter-gatherers might encounter a giant, snarling saber-toothed cat ready to pounce, or a group of elephantlike mammoths stripping tree branches. Maybe a herd of giant bison would stampede past.</p>
<p>Obviously, you can’t see any of these ice age megafauna now. They’ve all been extinct for about 12,800 years. Mammoths, mastodons, huge bison, horses, camels, very large ground sloths and giant short-faced bears all died out as the huge continental ice sheets disappeared at the end of the ice age. What happened to them?</p>
<p>Scientists have pointed to various potential causes for the extinctions. Some suggest <a href="https://doi.org/10.1038/s41467-021-21201-8">environmental changes happened faster</a> than the animals could adapt to them. Others posit a <a href="https://doi.org/10.1073/pnas.0706977104">catastrophic impact of a fragmented comet</a>. Maybe it was <a href="https://doi.org/10.1073/pnas.0501947102">overhunting on the part of humans</a>, or <a href="https://doi.org/10.1146/annurev.ecolsys.34.011802.132415">some combination of all these factors</a>.</p>
<p><a href="https://sc.edu/study/colleges_schools/artsandsciences/sc_institute_archeology_and_anthropology/faculty-staff/moore_christopher.php">One of my major interests as an archaeologist</a> has been to understand how the earliest Paleo-Americans lived and interacted with megafauna species. Just how implicated should humans be in the extinction of these ice age animals? In a new study, my colleagues and I used a forensic technique more commonly used to identify blood on objects at crime scenes <a href="https://doi.org/10.1038/s41598-023-36617-z">to investigate this question</a>.</p>
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<a href="https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Artist's rendition of Paleoamerican Clovis encampment with people sitting around campfire under night sky" src="https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528320/original/file-20230525-19-5p0no3.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"></a>
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<span class="caption">Clovis hunter-gatherers lived in small, mobile groups, likely following animal migrations over long distances.</span>
<span class="attribution"><span class="source">Martin Pate/Southeast Archeological Center, National Park Service</span></span>
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<h2>Testing stone tools like murder weapons</h2>
<p>Archaeologists have uncovered a sparse scattering of stone tools left at the campsites of Paleo-American Clovis hunter-gatherers who lived around the time of the megafauna extinctions. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="line drawing of two stone points" src="https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=682&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=682&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=682&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=857&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=857&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531835/original/file-20230614-25-wuuy96.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=857&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">Early Paleo-American Clovis points (left) and Middle Paleo-American redstone points (right) have a distinct fluted shape, highlighted in yellow, likely designed to facilitate hafting onto a spear or knife handle for use in hunting and butchery.</span>
<span class="attribution"><span class="source">Darby Erd</span></span>
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<p>These include iconic <a href="https://www.britannica.com/topic/Clovis-complex">Clovis spearpoints</a> with their distinctive flutes – concave areas left behind by removed stone flakes that extend from the base to the middle of the point. People most likely made the points this way so they could easily affix them to a spear shaft.</p>
<p>Based on <a href="https://www.heritagedaily.com/2016/02/an-afternoon-walk-and-a-mammoth-find-second-clovis-people-kill-site-found-in-new-mexico/109750">sites excavated in the western United States</a>, archaeologists know Paleo-American Clovis hunter-gatherers who lived around the time of the extinctions at least occasionally killed or scavenged ice age megafauna such as mammoths. There they’ve found preserved bones of megafauna together with the stone tools used for killing and butchering these animals. These sites are crucial for understanding the possible role that early Paleo-Americans played in the extinction event.</p>
<p>Unfortunately, many areas in the Southeastern United States lack sites with preserved bone and associated stone tools that might indicate whether megafauna were hunted there by Clovis or other Paleo-American cultures. Without evidence of preserved bones of megafauna, archaeologists have to find other ways to examine this question.</p>
<p>Forensic scientists have used an <a href="https://www.ojp.gov/ncjrs/virtual-library/abstracts/use-crossover-immunoelectrophoresis-detect-human-blood-protein-soil">immunological blood residue analysis</a> technique called <a href="https://doi.org/10.1016/0379-0738(78)90025-7">immunoelectrophoresis</a> for over 50 years to identify blood residue sticking to objects found at crime scenes. In recent years, researchers have applied this method to identify <a href="https://doi.org/10.1016/j.jasrep.2022.103785">animal blood proteins preserved within ancient stone tools</a>. They compare aspects of the ancient blood with blood antigens derived from modern relatives of extinct animals.</p>
<p>Residue analysis does not rely on the presence of nuclear DNA, but rather on preserved, identifiable proteins that sometimes survive <a href="https://doi.org/10.1006/jasc.2000.0628">within the microscopic fractures and flaws of stone tools</a> created during their manufacture and use. Typically, only a small percentage of artifacts produce <a href="https://library-archives.canada.ca/eng/services/services-libraries/theses/Pages/item.aspx?idNumber=27681369">positive blood residue results</a>, indicating a match between the ancient residue and antiserum molecules from modern animals.</p>
<p><a href="https://www.postandcourier.com/aikenstandard/news/a-lot-of-unknowns/article_95d93585-8455-5af6-b9e1-536b629f49ee.html">A previous blood residue study</a> of a small number of Paleo-American artifacts in South Carolina and Georgia failed to provide evidence that these people had hunted or scavenged extinct megafauna. The researchers found evidence of bison and other animals such as deer, bear and rabbit, but no evidence of Proboscidean (mammoth or mastodon) or of an extinct species of North American horse.</p>
<h2>Identifying ancient prey of human hunters</h2>
<p>My colleagues and I realized we needed a much larger sample of Paleo-American stone tools for testing. Since Clovis points and other Paleo-American artifacts are rare, I relied heavily on local museums, private collectors, collections housed at state universities and even military installations to amass a sample of 120 Paleo-American stone tools from all over North Carolina and South Carolina.</p>
<p>Because these artifacts are irreplaceable, I personally carried all 120 Clovis spearpoints and tools inside a protective case on a flight from South Carolina to the blood residue lab in Portland, Oregon. I coordinated in advance with the Transportation Security Administration so my collection of 13,000-year-old weaponry would make it through the screening process.</p>
<p>The blood residue analysis provided unambiguous proof that the tools had had contact with ancient animal blood proteins. The results included the first direct evidence on ancient stone tools of the blood of extinct mammoth or mastodon (Proboscidean) and the extinct North American horse (Equidae) on Paleo-American artifacts in eastern North America. This evidence is significant because it proves that these animals were present in the Carolinas, and they were hunted or scavenged by early Paleo-Americans.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="artist's rendition of prehistoric people hitting a mastodon with spears" src="https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528323/original/file-20230525-23-9vbnei.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">It likely would have taken a group of hunters to take down a mastodon.</span>
<span class="attribution"><a class="source" href="https://georgiainfo.galileo.usg.edu/gastudiesimages/Mastodon%20Hunt%201.htm">Ed Jackson</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>In addition to Proboscidean and horse, bison (Bovidae) blood residues were most common, adding to earlier blood residue research <a href="https://doi.org/10.7183/0002-7316.81.1.132">suggesting a focus on bison hunting</a> by Clovis and other Paleo-American cultures. Bison in North America did not go extinct but <a href="https://en.wikipedia.org/wiki/Bison_antiquus">instead became smaller</a>, most likely as a result of climate change as the last ice age ended and the climate warmed.</p>
<p>So, what do these results suggest for the extinction debate? While this study does not prove humans were responsible for the extinctions, it does show that early Paleo-Americans across the continent likely hunted or scavenged these animals, at least occasionally. The results also indicate that Proboscideans and horses were around when Clovis people were here – only a few hundred years before their eventual extinction in North America.</p>
<p>Another interesting finding is that while Proboscidean blood residues are found on Clovis artifacts, blood residues for horses (Equidae) are found on both Clovis and Paleo-American points that are slightly more recent younger than Clovis. This may suggest the extinction of Proboscidean was complete in the Carolinas by the end of the Clovis period, and the extinction of ice age horse species took longer.</p>
<p>Testing an even larger sample of Paleo-American stone tools from different regions of North America could help pin down the timing and geographic variability in the extinction of megafauna species and provide more clues about why these animals disappeared when they did.</p><img src="https://counter.theconversation.com/content/205556/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher R. Moore is affiliated with the the non-profit Comet Research Group (CRG).</span></em></p>A forensic technique more often used at modern crime scenes identified blood residue from large extinct animals on spearpoints and stone tools used by people who lived in the Carolinas millennia ago.Christopher R. Moore, Research Professor and Director of the Southeastern Paleoamerican Survey (SEPAS) at the South Carolina Institute for Archaeology and Anthropology, University of South CarolinaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2003412023-03-16T01:56:28Z2023-03-16T01:56:28ZAustralia’s extinct giant eagle was big enough to snatch koalas from trees<figure><img src="https://images.theconversation.com/files/515681/original/file-20230316-26-3p03fx.png?ixlib=rb-1.1.0&rect=0%2C0%2C3994%2C2000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dynatoaetus gaffae was twice the size of the wedge-tailed eagle we know today.</span> <span class="attribution"><span class="source">Mike Lee</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The year is 1959. Speleologists descend a 17-metre shaft to explore the depths of Mairs Cave in the southern Flinders Ranges. Some 55 metres into the main chamber, they find fossils scattered throughout a boulder pile. Among these fossils are a claw and part of a wing bone that appear to have come from a large eagle.</p>
<p>Over a decade passes. An expedition to the cave, led by naturalist Hans Mincham and palaeontologist and geologist Brian Daily, now arrives with the purpose of retrieving more fossils. Among the many mammal fossils they recover are another talon and most of a large bird breastbone – from the same large eagle.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/512331/original/file-20230227-5330-7jtilj.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">Exploring the depths of Mairs Cave, the place where the fossils were found.</span>
<span class="attribution"><span class="source">Aaron Camens</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>No more fossils of this animal are found until more than 50 years later. It is December of 2021, and a team of Flinders University palaeontologists and speleologists have travelled to the cave for a single purpose – to find more of this enigmatic bird. As they descend into the cave’s depths, they hope to find a few more bones. Instead, they find a partial skeleton, including leg and wing bones, and a skull. With this last discovery, <a href="https://link.springer.com/article/10.1007/s10336-023-02055-x">we were finally able to name and describe this gigantic eagle</a> in the Journal of Ornithology.</p>
<h2>History’s third-largest eagle</h2>
<p><em>Dynatoaetus gaffae</em> (Gaff’s powerful eagle) lived during the Pleistocene epoch, perhaps between 700,000 and 50,000 years ago. At twice the size of a wedge-tailed eagle (which it coexisted with) and with a potential wingspan of up to 3m, this species is the largest known eagle to have lived in Australia, and one of the largest continental raptors in the world.</p>
<p>Only two larger eagles ever existed anywhere: <a href="https://a-dinosaur-a-day.com/post/181728989600/gigantohierax-suarezi"><em>Gigantohierax suarezi</em></a>, which hunted giant rodents in Cuba, and the giant Haasts eagle, <a href="https://nzbirdsonline.org.nz/species/haasts-eagle"><em>Hieraaetus moorei</em></a> that hunted large moa in New Zealand. </p>
<p>Thanks to the relatively complete skeleton from Mairs Cave, we were able to identify other fossils of <em>Dynatoaetus</em> from the Naracoorte caves in South Australia and the Wellington caves in New South Wales. It appears this species was widespread across most of southern Australia.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=998&fit=crop&dpr=1 600w, https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=998&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=998&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1254&fit=crop&dpr=1 754w, https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1254&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/512313/original/file-20230226-4657-upvii2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1254&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A comparison of the tarsometatarsus (foot bone) of Dynatoaetus and a female Wedge-tailed eagle, with scaled silhouettes of the entire animals.</span>
<span class="attribution"><span class="source">Ellen Mather</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>A surprising family tree</h2>
<p>After discovering the fossils, we investigated how <em>Dynatoaetus</em> was related to other eagles, with surprising results. </p>
<p><em>Dynatoaetus</em> was not closely related to any modern Australian eagle. Instead, these birds (and another fossil Australian raptor <em><a href="https://theconversation.com/it-was-long-thought-these-fossils-came-from-an-eagle-turns-out-they-belong-to-the-only-known-vulture-species-from-australia-187017">Cryptogyps lacertosus</a></em>) were related to the old-world vultures and to the serpent-eagles of south Asia and Africa. </p>
<p><em>Dynatoaetus</em> was clearly not a vulture-like scavenger, as indicated by its large and powerful leg bones and talons, so to infer how it lived, we looked to the serpent-eagles.</p>
<p>Serpent-eagles, as their common name suggests, primarily hunt snakes and other reptiles. Most are small to medium-sized raptors and would have been dwarfed by <em>Dynatoaetus</em>. </p>
<p>However, there is one species in this subfamily that is an exception: the Philippine eagle. This raptor is one of the largest eagles alive today, and unlike its reptile-eating relatives, it prefers to prey on monkeys, flying lemurs, bats, birds, and occasionally young pigs or deer.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/512317/original/file-20230227-4216-nrztn1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Philippine eagle, depicted above, is a close relative of the extinct Dynatoaetus and one of the largest living eagles.</span>
<span class="attribution"><span class="source">Sinisa Djordje Majetic</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Strong feet for large prey</h2>
<p>Much like the Philippine eagle and other very large raptors, the legs and feet of <em>Dynatoaetus</em> were quite robust. This strongly suggests it was suited for killing large prey, perhaps much heavier than itself. </p>
<p><em>Dynatoaetus</em> shared ancient Australia with giant kangaroos and flightless birds, the young and sickly of which would have been suitable prey. Koalas and possums would have been plentiful in the treetops, and <em>Dynatoaetus</em> was certainly large enough to snatch them up. </p>
<p>This giant eagle was most likely one of Australia’s top predators during the Pleistocene.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/it-was-long-thought-these-fossils-came-from-an-eagle-turns-out-they-belong-to-the-only-known-vulture-species-from-australia-187017">It was long thought these fossils came from an eagle. Turns out they belong to the only known vulture species from Australia</a>
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<p>We can also find clues to potential prey via fossils found alongside <em>Dynatoaetus</em>. <a href="https://www.publish.csiro.au/AM/AM17035">Small mammals have previously been collected from Mairs Cave</a>, but the 2021 trip also recovered bones of short-faced kangaroos, wombats, bettongs, bandicoots, possums and even koalas (the only record of koalas inhabiting the Flinders Ranges), many of which were potential prey for the giant eagle. </p>
<p>We further found fossils of thylacines, Tasmanian devils and <a href="http://www.naturalworlds.org/thylacoleo/index.htm"><em>Thylacoleo</em></a> (the marsupial “lion”), indicating <em>Dynatoaetus</em> competed for prey with a cohort of marsupial carnivores. No one has yet identified beak and talon marks left on fossil bones from this giant raptor – but this may simply reflect that, until now, no-one was looking.</p>
<h2>The end of Australia’s megafauna</h2>
<p>So why did <em>Dynatoaetus</em> become extinct? It appears to have died out around the same time as much of the Australian <a href="https://ecoevocommunity.nature.com/posts/61740-megafauna-extinction">megafauna</a>, around 50,000 years ago. Perhaps it was specialised to hunt certain large species, and when this preferred prey went extinct it was unable to adapt. </p>
<p>With the demise of specialist raptors like <em>Dynatoaetus</em> and <em>Cryptogyps</em>, the generalist <a href="https://australian.museum/learn/animals/birds/wedge-tailed-eagle/">wedge-tailed eagle</a> was left as the sole survivor of the large inland raptors.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/meet-the-prehistoric-eagle-that-ruled-australian-forests-25-million-years-ago-168249">Meet the prehistoric eagle that ruled Australian forests 25 million years ago</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/200341/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Lee has a joint appointment at the South Australian Museum and Flinders University, and receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Trevor H. Worthy has received funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Aaron Camens and Ellen K. Mather 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>At twice the size of a wedge-tailed eagle, the newly discovered Dynatoaetus gaffae would have competed with thylacines and Tasmanian devils for prey.Ellen K. Mather, Adjunct associate lecturer, Flinders UniversityAaron Camens, Lecturer in Palaeontology, Flinders UniversityMike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders UniversityTrevor H. Worthy, Associate Professor, Vertebrate Palaeontology Group, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1769522023-01-24T06:16:06Z2023-01-24T06:16:06ZHow we cracked the mystery of Australia’s prehistoric giant eggs<figure><img src="https://images.theconversation.com/files/505414/original/file-20230119-20-rbmop2.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1488%2C927&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The giant bird Genyornis went extinct in Australia around 50,000 years ago.</span> <span class="attribution"><span class="source">Peter Trusler</span>, <span class="license">Author provided</span></span></figcaption></figure><p>It’s a long-running Australian detective story. From the 1980s onwards, researchers found eggshell fragments, and on rare occasions whole eggs, exposed in eroding sand dunes within the country’s arid zone (which covers most of Australia’s landmass).</p>
<p>A proportion of shells matched eggs laid by emus, but the rest belonged to a mystery species. Researchers initially identified the eggshells as belonging to a giant, extinct bird called <em>Genyornis</em>. But more recently, a group of scientists challenged this view.</p>
<p>With the help of artificial intelligence software, our team has now resolved this scientific controversy, showing that <em>Genyornis</em> was indeed the bird that laid these eggs. With colleagues based around the world, we have published the findings in <a href="https://www.pnas.org/doi/full/10.1073/pnas.2109326119">Proceedings of the National Academy of Sciences</a>. </p>
<p><em>Genyornis</em> was a flightless bird between two metres and 2.5 metres tall that once roamed the Australian landmass. The eggshell fragments are an important line of evidence about this extinct creature, so being certain about the identity of the bird that laid them is vital.</p>
<p>Some of the shell fragments are 400,000 years old, while the youngest are about 50,000 years old. <a href="https://www.nature.com/articles/ncomms10496">Previous work</a> showed that some of the youngest eggshells had been burned, but not in the way a wildfire would. Instead, scientific tests point to humans cooking the eggs for food.</p>
<p>The time period where <em>Genyornis</em> shells disappear (50,000 years ago) coincides with what’s thought to be the first arrival of humans in Australia. The discovery therefore raises the possibility that our species contributed to its extinction.</p>
<h2>Narrowing the candidates</h2>
<p>The eggshell fragments were first recognised by Dom Williams, a geologist and vertebrate palaeontologist from Flinders University in Adelaide, in 1981. He made the case that the fragments <a href="https://www.tandfonline.com/doi/abs/10.1080/03115518108565426">came from <em>Genyornis</em></a>, which belonged to a group of extinct creatures known as thunderbirds.</p>
<p>In the 1990s, a team including John Magee, at Australian National University, and Gifford Miller, one of the authors of this article, <a href="https://www.science.org/doi/abs/10.1126/science.283.5399.205">provided firm dates</a> for similar shell fragments collected at thousands of arid zone sites. <em>Genyornis</em> was one of many large animals – known as “megafauna” – that once roamed Australia and vanished at around the same time. The work by Miller, Magee and others pinned a clear date of 50,000 years ago on this extinction event.</p>
<p>The association of the eggshells with <em>Genyornis</em> was widely accepted from the 1980s until recently, when it was <a href="https://www.sciencedirect.com/science/article/pii/S027737911530192X">challenged by a team of scientists</a> from Flinders University in Australia. Based upon the size and structure of the eggshells, they argued for a different parent. Their favoured candidate was <em>Progura</em>, a 10kg extinct relative of modern birds such as the brush turkey and malleefowl. </p>
<p>Living birds belonging to this group - known as megapodes – build earthen mounds to incubate their eggs. <a href="https://theconversation.com/a-case-of-mistaken-identity-for-australias-extinct-big-bird-52856">The scientific debate</a> was fought out in academic journals, with neither side conceding.</p>
<h2>Chasing a solution</h2>
<p>Attempting to find a resolution, scientists who thought the eggs belonged to Genyornis turned to DNA. Despite <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2009.2019">the successful extraction</a> of genetic information from eggs of New Zealand’s extinct Moa bird, state-of-the-art DNA sequencing technology drew a blank in this case. The molecules were too degraded after 50,000 years under the hot Australian sun.</p>
<p>However, proteins – the molecular building blocks of cells – can provide similar information and can last for longer than DNA. In our study, we used a technique called amino acid racemisation to identify the shell fragments with the best-preserved proteins.</p>
<p>As part of the work, our team was able to retrieve partial protein sequences from the Australian eggshells. We then used software called AlphaFold, from the Google-owned AI lab DeepMind, to generate predicted structures for the molecules – the first time this has been done for ancient proteins.</p>
<p>Two of us, Matthew Collins and Beatrice Demarchi, contacted the <a href="https://b10k.genomics.cn">Bird 10,000 Genomes (B10K) Project</a>. This has set itself the ambitious goal of sequencing the genomes of all bird species.</p>
<p>B10K project member Josefin Stiller took the reconstructed protein sequences and <a href="https://unfolded.deepmind.com/stories/unlocking-the-mystery-of-the-demon-duck-of-doom">placed them within a “family tree”</a> showing how proteins differ between bird species. The proteins were complete enough to resolve the position of the mystery eggs within the deep branches of this tree of protein sequences, but not sufficiently diagnostic to uniquely identify what the parent bird was.</p>
<p>However, as <a href="https://www.pnas.org/doi/full/10.1073/pnas.2109326119">detailed in our latest paper</a>, the protein sequences were able to conclusively rule out that the parent was a megapode. As there are no other candidate birds, we concluded – as Williams had first proposed in the 1980s – that the eggshells belonged to <em>Genyornis</em>.</p>
<p>This means we can confidently interpret other evidence locked in the shells with implications for how <em>Genyornis</em> went extinct and why the emus that lived alongside it survived. </p>
<h2>Picky eater</h2>
<p>Isotopes are different forms of chemical elements that can record information about factors such as diet and climate. Carbon isotopes within the eggshell fragments provide information on the birds’ diets and show that <em>Genyornis</em> was a pickier eater than the emu. Oxygen isotopes can be used to track aridity and show that conditions were increasingly dry around the time <em>Genyornis</em> eggshells disappear.</p>
<p>In previous work, Miller and his colleagues <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379116302815">analysed the same isotopes in emu eggshells</a> across the time window of <em>Genyornis’</em> extinction and found that summer-season grasses abruptly disappear from the birds’ diets. This is consistent with a dramatic reduction in monsoon rains.</p>
<p>These findings suggest that <em>Genyornis</em> was already somewhat vulnerable to a changing environment, but another factor may have proved important to its ultimate fate. </p>
<p>When coupled with the lack of evidence from <em>Genyornis</em> skeletons for direct predation, the burnt eggshells suggest that – as is so common elsewhere in the world – human pressure was likely to have been a factor that finally drove these impressive birds to extinction.</p><img src="https://counter.theconversation.com/content/176952/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew James Collins receives funding from The Danish National Research Foundation. He is affiliated with The University of Copenhagen. </span></em></p><p class="fine-print"><em><span>Beatrice Demarchi receives funding from the Italian Ministry of University and Research </span></em></p><p class="fine-print"><em><span>Gifford Miller receives funding from the US National Science Foundation. </span></em></p>A puzzle over the identity of an extinct bird that laid eggs across Australia has been solved.Matthew James Collins, Professor of Palaeoproteomics, University of CambridgeBeatrice Demarchi, Associate professor, Università di TorinoGifford Miller, Distinguished Professor of Geological Sciences, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1906882022-09-26T20:03:09Z2022-09-26T20:03:09ZStudy finds famous Australian caves are up to 500,000 years older than we thought - and it could help explain a megafauna mystery<figure><img src="https://images.theconversation.com/files/486454/original/file-20220926-26-wzmem4.jpg?ixlib=rb-1.1.0&rect=130%2C7%2C2429%2C1598&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Steve Bourne, Author provided</span>, <span class="license">Author provided</span></span></figcaption></figure><p>South Australia’s <a href="https://www.naracoortecaves.sa.gov.au/world-heritage/why-are-these-caves-so-special">Naracoorte Caves</a> is one of the world’s best fossil sites, containing a record spanning more than half a million years. Among the remains preserved in layers of sand are the <a href="https://theconversation.com/naracoorte-where-half-a-million-years-of-biodiversity-and-climate-history-are-trapped-in-caves-78603">bones</a> of many iconic Australian megafauna species that became <a href="https://www.nature.com/articles/ncomms10511">extinct</a> between 48,000 and 37,000 years ago.</p>
<p>The reasons for the demise of these megafauna species are intensely debated. But the older the fossils we can find, the better we can understand the species’ evolution and extinction. </p>
<p>To date, determining the precise age of the caves has been difficult. However our research demonstrates, for the first time, how old Naracoorte’s caves really are – and the answer is up to 500,000 years older than previously thought.</p>
<p>Our findings shed new light on the antiquity of this important place. We hope this will aid understanding of how biodiversity responds to a changing climate over time.</p>
<figure class="align-center ">
<img alt="illustration of megafauna running and sitting" src="https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485286/original/file-20220919-24-wboteo.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">
<figcaption>
<span class="caption">Artist’s impression of extinct Pleistocene megafauna in Australia by Julian Hume. Lower left: enormous short-faced kangaroos. Lower right: <em>Thylacoleo carnifex</em> and <em>Wonambi naracoortensis</em>. Centre left and right: <em>Diprotodon optatum</em> and <em>Zygomaturus trilobus</em>.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>A moment in geologic time</h2>
<p>Caves can be extraordinary time capsules, often preserving the remains of long extinct plants and animals in exquisite detail. The Naracoorte Caves in South Australia is one such example.</p>
<p>The cave complex is South Australia’s only World Heritage site. Among the remarkably diverse and complete fossil record are the remains of iconic megafauna such as:</p>
<ul>
<li><em>Thylacoleo carnifex</em> (marsupial predator)</li>
<li><em>Zygomaturus tribolus</em> (huge herbivore)</li>
<li><em>Wonambi naracoortensis</em> (giant constrictor snake)</li>
<li><em>Procoptodon goliah</em> (browsing sthenurine kangaroo). </li>
</ul>
<p>Palaeontologists have excavated and dated many of these fossil deposits and reconstructed the skeletons of a number of megafauna species.</p>
<p>The caves formed when groundwater percolated through cracks in limestone rocks, dissolving them and forming cavities. They were previously dated at between <a href="https://www.sciencedirect.com/science/article/abs/pii/S0169555X14004620?via%3Dihub">0.8 and 1.1 million years old</a> – an estimate generated by dating a fossil dune ridge that lies over the cave complex.</p>
<p>But the methods used to date the dune ridge were <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1502-3885.2008.00052.x?casa_token=V35G_uz7Z4QAAAAA%3A_6xXw2802oskY-l5TxOwJyq_y-tFdLattENDcMHT9K_AWELvB2HuUqVMYUR2sp28D7B1dde_Bjbw27v2">not</a> <a href="https://linkinghub.elsevier.com/retrieve/pii/B9780444536433000546">entirely</a> suitable for the task. As such, a precise age of the caves had not been obtained, until now.</p>
<p>This intricate work involved in our study has taken five years, but it was worth the wait.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/did-people-or-climate-kill-off-the-megafauna-actually-it-was-both-127803">Did people or climate kill off the megafauna? Actually, it was both</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="fossilised bone in rock" src="https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=277&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=277&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=277&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=348&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=348&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486423/original/file-20220926-388-res0uz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=348&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Layers of flowstones overlying sandy layers with fossil bone material in Specimen Cave, Naracoorte.</span>
<span class="attribution"><span class="source">Jon Woodhead, Author provided</span></span>
</figcaption>
</figure>
<h2>What we did</h2>
<p>The dating method <a href="https://www.nature.com/articles/s43247-022-00538-y">we used</a> involved examining the beautiful calcite formations inside the caves. Collectively, these are called “speleothems” and they include stalagmites, stalactites and flowstones. </p>
<p>When speleothems form, tiny amounts of uranium – a radioactive element – are locked inside them. Over time, uranium slowly decays into the element lead. This occurs at a known, constant rate – which means we can use uranium in speleothems as a natural clock to date them. </p>
<p>Doing so involved extracting uranium and lead from the speleothem in a laboratory. We then measured each element and calculate the sample’s age very precisely.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486379/original/file-20220925-5293-pu8e4v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Whale Bone Cave, one of the oldest caves at Naracoorte.</span>
<span class="attribution"><span class="source">Steve Bourne, Author provided</span></span>
</figcaption>
</figure>
<p>Because speleothems only start to grow once a subterranean cavity is formed and above the groundwater table, the oldest speleothem age reveals the minimum age of the cave itself.</p>
<p>From this, we found the caves began to form at least 1.34 million years ago – making them 250,000 to 500,000 years older than previous estimates.</p>
<p>The second part of our study sought to determine when the caves first opened to the surface, allowing both air and animals in. We did this by examining microscopic particles of charcoal and pollen captured in the calcite formations as they grew. </p>
<p>We found charcoal and pollen first appeared in the caves around 600,000 years ago. This suggests the caves may harbour exciting new vertebrate fossil material up to 600,000 years old – more than 100,000 years older than the oldest known <a href="https://www.sciencedirect.com/science/article/abs/pii/S1871101422000188">fossil deposits</a> at the complex.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/naracoorte-where-half-a-million-years-of-biodiversity-and-climate-history-are-trapped-in-caves-78603">Naracoorte, where half a million years of biodiversity and climate history are trapped in caves</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="woman smiles as she descends into cave" src="https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=483&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=483&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=483&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=607&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=607&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485292/original/file-20220919-24-rz0g00.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=607&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Lead author Rieneke Weij descending into a cave at Naracoorte.</span>
<span class="attribution"><span class="source">Liz Reed, Author provided</span></span>
</figcaption>
</figure>
<h2>Why this matters</h2>
<p>There’s heated <a href="https://theconversation.com/did-people-or-climate-kill-off-the-megafauna-actually-it-was-both-127803">debate</a> about whether the extinction of Australia’s megafauna was the result of humans or the climate. </p>
<p>A good chronology is key to understanding when and how quickly natural processes occurred over time. Without precise ages, we cannot know the rate of change to landscapes, climate or biodiversity.</p>
<p>So while the Naracoorte Caves formed at least 1.34 million years ago, they did not open to the surface until 600,000 years ago. This sheds new light on the vast separation in time between landforms evolving and fossils accumulating. </p>
<p>Our findings will also help palaeontologists target new excavation sites to find older fossils – hopefully providing valuable further evidence of how our continent’s unique biodiversity has changed.</p>
<p>Our new approach can help to unravel how old fossil deposits at other cave complexes <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379108001650">in Australia</a> and <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/jqs.3110">around</a> the <a href="https://www.pnas.org/doi/full/10.1073/pnas.0402592101">world</a> where both speleothems and vertebrate fossils are found.</p>
<p>Australia’s richness of plant and animal species faces an uncertain future, due to climate change and other human impacts. Studying important sites such as the Naracoorte Caves helps us understand not just how climate change influenced biodiversity in the past, but what might happen in future.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/aboriginal-australians-co-existed-with-the-megafauna-for-at-least-17-000-years-70589">Aboriginal Australians co-existed with the megafauna for at least 17,000 years</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/190688/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rieneke Weij receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Jon Woodhead receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Kale Sniderman receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Liz Reed receives funding from the Australian Research Council. </span></em></p>The findings will help us better understand how biodiversity responds to a changing climate over time.Rieneke Weij, Postdoctoral researcher in Geochemistry/Palaeoclimatology, University of Cape TownJon Woodhead, Professor emeritus, The University of MelbourneKale Sniderman, Senior Research Fellow, The University of MelbourneLiz Reed, Research Fellow, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1793602022-06-27T12:25:01Z2022-06-27T12:25:01ZHow many ice ages has the Earth had, and could humans live through one?<figure><img src="https://images.theconversation.com/files/468859/original/file-20220614-17290-2cjvwa.jpg?ixlib=rb-1.1.0&rect=25%2C12%2C8601%2C5729&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">During ice ages, ice sheets like the one in Greenland have covered much of Earth's surface. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-greenland-ice-sheet-is-the-largest-ice-sheet-in-the-news-photo/1399203109">Thor Wegner/DeFodi Images via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How many ice ages has the Earth had, and could humans live through one? – Mason C., age 8, Hobbs, New Mexico</strong></p>
</blockquote>
<p>First, what is an <a href="https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/ice-ages-what-are-they-and-what-causes-them/">ice age</a>? It’s when the Earth has cold temperatures for a long time – millions to tens of millions of years – that lead to ice sheets and glaciers covering large areas of its surface. </p>
<p>We know that the Earth has had <a href="http://iceage.museum.state.il.us/content/when-have-ice-ages-occurred">at least five major ice ages</a>. The first one happened about 2 billion years ago and lasted about 300 million years. The most recent one started about 2.6 million years ago, and in fact, we are still technically in it. </p>
<p>So why isn’t the Earth covered in ice right now? It’s because we are in a period known as an “interglacial.” In an ice age, temperatures will fluctuate between colder and warmer levels. Ice sheets and glaciers melt during warmer phases, which are called interglacials, and expand during colder phases, which are called glacials.</p>
<p>Right now we are in the most recent ice age’s warm interglacial period, which began about 11,000 years ago.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/I4EZCy14te0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Earth’s climate goes through warming and cooling cycles that are influenced by gases in its atmosphere and variations in its orbit around the sun.</span></figcaption>
</figure>
<h2>What was it like during the ice age?</h2>
<p>When most people talk about the “ice age,” they are usually referring to the last glacial period, which began about 115,000 years ago and ended about 11,000 years ago with the start of the current interglacial period. </p>
<p>During that time, the planet was much cooler than it is now. At its peak, when ice sheets covered most of North America, the average global temperature was about <a href="https://www.smithsonianmag.com/smart-news/ice-age-temperature-science-how-cold-180975674/">46 degrees Fahrenheit</a> (8 degrees Celsius). That’s 11 degrees F (6 degrees C) cooler than the global annual average today.</p>
<p>That difference might not sound like a lot, but it resulted in most of North America and Eurasia being covered in ice sheets. Earth was also much drier, and <a href="https://www.usgs.gov/media/images/coastline-eastern-us-changesslowly">sea level was much lower</a>, since most of the Earth’s water was trapped in the ice sheets. <a href="https://education.nationalgeographic.org/resource/steppe">Steppes</a>, or dry grassy plains, were common. So were <a href="http://kids.nceas.ucsb.edu/biomes/savanna.html">savannas</a>, or warmer grassy plains, and deserts.</p>
<p>Many <a href="https://ucmp.berkeley.edu/quaternary/ple.html">animals present during the ice age</a> would be familiar to you, including brown bears, caribou and wolves. But there were also megafauna that went extinct at the end of the ice age, like <a href="https://uwaterloo.ca/earth-sciences-museum/resources/ice-age-mammals">mammoths, mastodons, saber-toothed cats</a> and <a href="https://www.livescience.com/56762-giant-ground-sloth.html">giant ground sloths</a>. </p>
<p>There are different ideas about <a href="https://samnoblemuseum.ou.edu/understanding-extinction/extinctions-in-the-recent-past-and-the-present-day/pleistocene-extinctions/">why these animals went extinct</a>. One is that humans hunted them into extinction when they came in contact with the megafauna.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientist and workers gather around a jawbone and horns protruding out of the ground." src="https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468864/original/file-20220614-2525-72v0y4.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">Excavating a mastodon skeleton at Burning Tree Golf Course in Heath, Ohio, December 1989. The skeleton, found by workers who were digging a pond, was 90% to 95% complete and more than 11,000 years old.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/mF53eR">James St. John/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Wait, there were humans during the ice age?!</h2>
<p>Yes, people just like us lived through the ice age. Since our species, <em>Homo sapiens</em>, <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-sapiens">emerged about 300,000 years ago in Africa</a>, we have spread around the world. </p>
<p>During the ice age, some populations remained in Africa and did not experience the full effects of the cold. Others moved into other parts of the world, including the cold, glacial environments of Europe. </p>
<p>And they weren’t alone. At the beginning of the ice age, there were other species of hominins – a group that includes our immediate ancestors and our closest relatives – throughout Eurasia, like the <a href="https://humanorigins.si.edu/evidence/human-fossils/species/homo-neanderthalensis">Neanderthals</a> in Europe and the mysterious <a href="https://www.newscientist.com/definition/denisovans/">Denisovans</a> in Asia. Both of these groups seem to have gone extinct before the end of the ice age. </p>
<p>There are lots of ideas about how our species survived the ice age when our hominin cousins did not. Some think that it has to do with how adaptable we are, and how we <a href="https://www.discovermagazine.com/planet-earth/how-humans-survived-the-ice-age">used our social and communication skills and tools</a>. And it appears that humans didn’t hunker down during the ice age. Instead they moved into new areas. </p>
<p>For a long time it was thought that humans did not enter North America until after the ice sheets started to melt. But <a href="https://www.nps.gov/whsa/learn/nature/fossilized-footprints.htm">fossilized footprints</a> found at <a href="https://www.nps.gov/whsa/index.htm">White Sands National Park</a> in New Mexico show that humans have been in North America since at least 23,000 years ago – close to the peak of the last ice age.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
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<p class="fine-print"><em><span>Denise Su 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>The Earth has had at least five major ice ages, and humans showed up in time for the most recent one. In fact, we’re still in it.Denise Su, Associate Professor, Arizona State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1460732022-01-23T13:44:19Z2022-01-23T13:44:19ZAncient DNA suggests woolly mammoths roamed the Earth more recently than previously thought<figure><img src="https://images.theconversation.com/files/442067/original/file-20220123-17253-1q5eenk.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6607%2C2106&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Genetic material found in permafrost sediments from the Yukon contains rich information about ancient ecosystems.</span> <span class="attribution"><span class="source">(Julius Csotonyi/Government of Yukon)</span>, <span class="license">Author provided</span></span></figcaption></figure><iframe style="width: 100%; height: 175px; border: none; position: relative; z-index: 1;" allowtransparency="" src="https://narrations.ad-auris.com/widget/the-conversation-canada/ancient-dna-suggests-woolly-mammoths-roamed-the-earth-more-recently-than-previously-thought" width="100%" height="400"></iframe>
<p>In 2010, small cores of permafrost sediments were collected by a team at the <a href="https://cms.eas.ualberta.ca/froeselab/">University of Alberta</a> from <a href="https://www.nps.gov/yuch/learn/historyculture/placer-mining.htm">gold mines</a> in the Klondike region of central Yukon. They had remained in cold storage until paleogeneticists at the <a href="https://socialsciences.mcmaster.ca/mcmaster-ancient-dna-centre">McMaster Ancient DNA Centre</a> applied new genomics techniques to better understand the <a href="https://doi.org/10.1002/gj.2633">global extinction of megafauna that had culminated in North America some 12,700 years ago</a>.</p>
<p>These tiny sediment samples contain an immense wealth of ancient environmental DNA from innumerable plants and animals that lived in those environments over millennia. These genetic microfossils originate from all components of an ecosystem — including bacteria, fungi, plants and animals — and serve as a time capsule of long-lost ecosystems, such as the <a href="https://pleistocenepark.ru/science/">mammoth-steppe</a>, which disappeared around 13,000 years ago.</p>
<p>How exactly these ecosystems restructured so significantly, and why large animals seem to have been the most impacted by this shift has been an <a href="https://doi.org/10.2307/1005126">active area of scientific debate since the 18th century</a>. </p>
<p>We can now use environmental DNA to help fill the gaps that have driven this debate.</p>
<h2>Ancient DNA, cutting-edge technologies</h2>
<p>Bacterial, fungal and unidentifiable DNA make up over 99.99 per cent of an environmental sample. In our case, we wanted a way to selectively recover the much smaller fraction of ancient plant and animal DNA that would help us better understand the collapse of the mammoth-steppe ecosystem.</p>
<p>For my <a href="http://hdl.handle.net/11375/26197">doctoral research</a>, I was part of a team that developed a <a href="https://doi.org/10.1017/qua.2020.59">a new technique to extract, isolate, sequence and identify tiny fragments of ancient DNA from sediment</a>.</p>
<p>We analyzed these DNA fragments to track the shifting cast of plants and animals that lived in central Yukon over the past 30,000 years. <a href="https://doi.org/10.1017/qua.2020.59">We found evidence</a> for the late survival of woolly mammoths and horses in the Klondike region, some 3,000 years later than expected.</p>
<p>We then <a href="https://doi.org/10.1038/s41467-021-27439-6">expanded our analysis</a> to include 21 previously collected permafrost cores from four sites in the Klondike region that date between 4,000 to 30,000 years ago.</p>
<p>With current technologies, we not only could identify which organisms a set of genetic microfossils came from. But we <a href="https://doi.org/10.1016/j.cub.2021.12.023">were also able to reassemble</a> those fragments into genomes to study their evolutionary histories — solely from sediment.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Synthesis of genetic and fossil evidence" src="https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=496&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=496&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=496&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=624&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=624&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442016/original/file-20220121-17-1wtpnht.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=624&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Synthesis of dated bones, ancient environmental DNA and archaeological sites in Yukon and Alaska.</span>
<span class="attribution"><span class="source">(Tyler J. Murchie)</span></span>
</figcaption>
</figure>
<h2>Tremendous environmental change</h2>
<p>The <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pleistocene-holocene-boundary">Pleistocene-Holocene transition, which occurred about 11,700 years ago,</a> was a period of tremendous change across the globe. In <a href="https://www.beringia.com/exhibits/beringia">eastern Beringia (the former Eurasian land bridge and unglaciated regions of Yukon and Alaska)</a>, this period saw the collapse of the <a href="https://doi.org/10.1016/j.quascirev.2012.10.005">mammoth-steppe biome</a> and its gradual replacement with the <a href="https://www.nrcan.gc.ca/our-natural-resources/forests/sustainable-forest-management/boreal-forest/13071">boreal forest</a> as we know it today. </p>
<p>This brought about the loss of iconic ice age megaherbivores like the <a href="https://www.beringia.com/exhibit/ice-age-animals/woolly-mammoth">woolly mammoth</a>, <a href="https://www.beringia.com/exhibit/ice-age-animals/yukon-horse">Yukon horse,</a> and <a href="https://www.beringia.com/exhibit/ice-age-animals/steppe-bison">steppe bison</a>, along with predators such as the <a href="https://www.beringia.com/exhibit/ice-age-animals/american-scimitar-cat">American scimitar cat</a> and <a href="https://www.beringia.com/exhibit/ice-age-animals/beringian-lion">Beringian lion</a>, among many others.</p>
<p>We found ancient environmental DNA from a diverse spectrum of ancient fauna, <a href="https://doi.org/10.1038/s41467-021-27439-6">including woolly mammoths, horses, steppe bison, caribou, rodents, birds and many other animals</a>.</p>
<p>We were also able to observe how ecosystems shifted with the rise of woody shrubs around 13,500 years ago, and how that correlated with a decline of DNA from woolly mammoths, horses and steppe bison. With this remarkably rich dataset, we observed four main findings.</p>
<ol>
<li><p>There was a surprising consistency in the signal between sites, suggesting our data was representative of ecological trends in the region.</p></li>
<li><p>Woolly mammoth DNA declines prior to the <a href="https://doi.org/10.1029/2005JD006079">Bølling–Allerød warming</a>, a warm period at the end of the last ice age, suggesting that megafaunal losses may have been staggered. </p></li>
<li><p><a href="https://albertaplantid.ca/forb-species/">Forbs (herbaceous flowering plants)</a> make up a substantial component of the mammoth-steppe ecosystem alongside grasses. </p></li>
<li><p>There is a consistent signal of woolly mammoth and Yukon horse persistence into the Holocene, as much as 7,000 years after their disappearance from fossil records.</p></li>
</ol>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Comparing equid genomes reconstructed from sediments and bone" src="https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=698&fit=crop&dpr=1 600w, https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=698&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=698&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=877&fit=crop&dpr=1 754w, https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=877&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/439574/original/file-20220105-27-1e1pnkn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=877&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 showing the location and relationship of horses and their relatives with genomes reconstructed from bones and sediment.</span>
<span class="attribution"><span class="source">(Tyler J.Murchie)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>When paired with other records, our genetic reconstructions suggest that the transition out of the last glacial period may have been more drawn out than dated bones alone would suggest.</p>
<p>Mammoths, for example, may have declined in local population abundance thousands of years earlier than other megafauna, which is potentially correlated with the first <a href="https://doi.org/10.1371/journal.pone.0169486">controversial evidence</a> of humans in the area. Further, <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/refugium">grassland grazing animals may have persisted for thousands of years in refugia (habitats that support the existence of an isolated population)</a>, despite the environmental shift.</p>
<h2>Woolly mammoths alongside humans</h2>
<p>Our data suggest that horses and woolly mammoths may have persisted in the Klondike until approximately 9,000 years ago and perhaps as recently as 5,700 years ago, outliving their supposed disappearance from <a href="https://doi.org/10.1073/pnas.2107977118">local fossil records by 7,000 years</a>. However, it is possible for <a href="https://doi.org/10.1111/j.1502-3885.2010.00181.x">ancient environmental DNA to survive erosion and re-deposition</a>, which could mix the genetic signals of different time periods, necessitating a degree of caution in our interpretations. </p>
<p>Until recently, there was no evidence of mammoth survival into the mid-Holocene. But studies have now shown that mammoths survived until <a href="https://doi.org/10.1073/pnas.1604903113">5,500</a> and <a href="https://doi.org/10.1016/j.yqres.2008.03.005">4,000</a> years ago on Arctic islands.</p>
<p>Researchers at the <a href="https://globe.ku.dk/research/geogenetics/">Centre for GeoGenetics in Copenhagen</a> found evidence for the late survival of horses and mammoths in Alaska until as recently as as <a href="https://doi.org/10.1038/s41586-021-04016-x">7,900 years ago</a>. They also found evidence of mammoths surviving as recently as 3,900 years ago in Siberia, alongside <a href="https://globe.ku.dk/newslist/2021/geneticists-map-the-rhinoceros-family-tree/">woolly rhinoceros</a> to at least 9,800 years ago. </p>
<p>Steppe bison, which were thought to have disappeared and been replaced by the <a href="https://www.hww.ca/en/wildlife/mammals/north-american-bison.html">American bison</a> during the Pleistocene, have likewise been found to have survived even as recently as perhaps just <a href="https://doi.org/10.1073/pnas.1601077113">400 years ago</a>. We were able to observe <a href="https://doi.org/10.1016/j.cub.2021.12.023">the presence of distinct genetic lineages of both woolly mammoths and steppe bison</a> in the same sediment samples, which suggests that there were likely distinct populations of these animals living in the same area.</p>
<p>There is a growing body of evidence that many ice age megafauna probably survived well into recorded human history, roaming the north during the <a href="https://www.britannica.com/event/Bronze-Age">Bronze Age</a> and while builders worked on the <a href="https://www.worldhistory.org/Old_Kingdom_of_Egypt/">pyramids of Egypt</a>.</p>
<figure class="align-center ">
<img alt="illustration of a woolly rhinoceros" src="https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441832/original/file-20220120-9089-elhtg.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">Researchers in Denmark found evidence of woolly rhinoceroses surviving in Siberia at least 9,800 years ago.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Genetic archives of our ecological past</h2>
<p>The growing sophistication of environmental DNA methods to study ancient genetic microfossils highlights just how much information is buried in sediments. </p>
<p>Permafrost is ideal for preserving ancient DNA, but as this <a href="https://www.canadiangeographic.ca/article/arctic-permafrost-thawing-heres-what-means-canadas-north-and-world">perennially frozen ground thaws and degrades with a warming Arctic</a>, so too will the genetic material preserved within, and the evolutionary mysteries they once held. </p>
<p>Advances in paleogenetics continues to push the boundaries of what was once relegated to science fiction. Who knows what undiscovered evolutionary information remains frozen in ordinary sediments, hidden in microfossils of ancient DNA?</p><img src="https://counter.theconversation.com/content/146073/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tyler J. Murchie currently receives funding from the CANA Foundation, a non-profit organization with horse rewilding initiatives.</span></em></p>Permafrost in the Yukon is a treasure trove of ancient environmental DNA, but climate change threatens these rich historical archives.Tyler J. Murchie, Postdoctoral fellow, Anthropology, McMaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1532232021-01-13T16:59:31Z2021-01-13T16:59:31ZDire wolves went extinct 13,000 years ago but thanks to new genetic analysis their true story can now be told<figure><img src="https://images.theconversation.com/files/378570/original/file-20210113-19-q0p0db.jpg?ixlib=rb-1.1.0&rect=5%2C33%2C3709%2C2510&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">North America during the late Pleistocene: a pack of dire wolves (red hair) are feeding bison while a pair of grey wolves approach in the hopes of scavenging.</span> <span class="attribution"><span class="source">Mauricio Antón</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Thanks to the hit television series Game of Thrones, the dire wolf has gained a near-mythical status. But it was a real animal that roamed the Americas for at least 250,000 years, until it became extinct towards the end of the last ice age around 13,000 years ago. While in popular culture the dire wolf is portrayed as a giant predator hunting in snow-covered, northern landscapes, most scientists instead agree that the dire wolf was <a href="http://digitallibrary.amnh.org/handle/2246/5999">a very close cousin of the grey wolf</a> – the living species from which the dog was domesticated.</p>
<p>Our research published in the journal <a href="https://www.nature.com/articles/s41586-020-03082-x">Nature</a> shows that both of these characterisations are mistaken. For the first time, we were able to sequence ancient DNA from remains of the now-extinct dire wolf, providing surprising new insights into its origins and biology.</p>
<p>In addition to the grey wolf there are eight related wolf-like species alive today, including the coyote, African wild dog, and three species of jackal. We originally expected our genetic data to confirm what was already known based on looking at the size and shape of their bones: the dire wolf was just a large grey wolf or a very close relative.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Jon Snow from Game of Thrones with his dire wolf." src="https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378577/original/file-20210113-23-14k5jll.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sorry, Game of Thrones fans: dire wolves probably weren’t white.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/101832432@N04/24689714842">Ed's Toy Box / flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>Instead, by comparing dire wolf DNA to that of living species we found that the dire wolf belonged to an unknown 6 million year-old lineage, which was no more closely related to grey wolves than to jackals or the African wild dog. This suggests that the resemblance between dire and grey wolves may have only been skin deep – or bone deep, strictly speaking.</p>
<h2>Evolving depictions of the dire wolf</h2>
<p>In contrast to its depiction in Game of Thrones, the fossil record of the dire wolf shows it actually lived in temperate or tropical areas of the Americas. The grey wolf on the other hand is often found in the Arctic or other high-latitude areas, and all those in North America today descend from a single colonisation <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/jbi.12765">around 20,000 years ago</a>. In evolutionary terms, this means the two species may have only encountered each other relatively recently.</p>
<p>Though dire and grey wolves then shared the same environment for thousands of years, our new genetic data revealed that they did not interbreed. This was surprising, given that <a href="https://theconversation.com/yes-eastern-coyotes-are-hybrids-but-the-coywolf-is-not-a-thing-50368">interbreeding between wolf-like species</a> tends to be a rule rather than the exception. We concluded that the dire wolf must have been geographically isolated for a long time to build up such a pronounced biological difference that it could no longer interbreed with the grey wolf when they met again in North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A wolf-like animal" src="https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378575/original/file-20210113-23-i9je8d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The eastern coyote, or ‘coywolf’ is a hybrid of coyote, wolf and domestic dog.</span>
<span class="attribution"><span class="source">Paul Tessier / shutterstock</span></span>
</figcaption>
</figure>
<p>The science suggests we should imagine the dire wolf as a very different animal to the grey wolf. When the two species did finally meet, they are likely to have already evolved very different behaviours, diets and appearances. Although we have no evidence about soft tissues or hair colour, palaeoartist <a href="https://mauricioanton.wordpress.com/">Mauricio Antón</a> represented them in the picture at the top of this article as more like a giant dhole (a wolf-like animal found in Asia), with short, reddish hair and larger ears for improved thermoregulation.</p>
<h2>Fate of a unique lineage</h2>
<p>So why did the dire wolf disappear, but not the grey wolf or other wolf-like species?</p>
<p>Most scientists agree that the dire wolf specialised in hunting large herbivores, many of which – including horses, bison and camels – became extinct or drastically declined in North America around 13,000 years ago. The disappearance of their prey almost certainly drove the dire wolf extinct. In contrast, the more flexible and adaptable grey wolf can survive on a greater variety of food sources.</p>
<p>Our new results help to explain these observations by showing that dire wolves probably evolved to become specialised over millions of years, meaning it was likely to have been very hard for them to adapt to rapid changes in their environment and prey. Plus, while some animal species – like the grey wolf – can sometimes evolve new adaptations <a href="https://doi.org/10.1093/molbev/msy031">after interbreeding with related species</a>, this apparently wasn’t possible for the dire wolf.</p>
<p>In the end, our results highlight just how much biological diversity has been lost in the recent past, as no living members of the dire wolf lineage now survive. The dire wolf thus represents yet another cautionary tale about how vulnerable specialised species are to rapid environmental changes, such as those driven by climate change or invasive species.</p><img src="https://counter.theconversation.com/content/153223/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kieren Mitchell receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Alice Mouton received funding from a NSF (National Science Foundation) grant and the QCB Collaboratory Postdoctoral Fellowship (UCLA).</span></em></p><p class="fine-print"><em><span>Angela Perri receives funding from European Union's Horizon 2020 Marie Curie Actions COFUND. </span></em></p><p class="fine-print"><em><span>Laurent Frantz receives funding from the Natural Environment Research Council (NERC), the Wellcome Trust, the Global Challenges Research Fund (GCRF), and the European Research Council (ERC).</span></em></p>Our research shows dire wolves lived in the tropics not the Arctic, and were not especially close relatives of the grey wolf.Kieren Mitchell, Lecturer, Australian Centre for Ancient DNA (ACAD) & Centre for Australian Biodiversity and Heritage (CABAH), University of AdelaideAlice Mouton, Postdoctoral Researcher, Conservation and Evolutionary Genomics, Université de LiègeAngela Perri, Research Fellow, Archaeology, Durham UniversityLaurent Frantz, Professor of Palaeogenomics, Ludwig Maximilian University of MunichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1476562020-10-07T19:10:21Z2020-10-07T19:10:21ZIt was growing rainforests, not humans, that killed off Southeast Asia’s giant hyenas and other megafauna<figure><img src="https://images.theconversation.com/files/362096/original/file-20201007-14-1ciu27.jpeg?ixlib=rb-1.1.0&rect=56%2C56%2C4159%2C3148&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Peter Schouten</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Thinking of Southeast Asia today may conjure up images of dense tropical rainforests teeming with iconic jungle animals such as orangutans, tigers and monkeys.</p>
<p>Perhaps less well known, but just as important to these ecosystems, are a host of other large-bodied creatures: the goat-like <a href="https://en.wikipedia.org/wiki/Serow">serows</a> and <a href="https://en.wikipedia.org/wiki/Goral">gorals</a>, <a href="https://www.wwf.org.uk/learn/wildlife/asian-rhinos">three species of Asian rhino</a> and the only species of <a href="https://en.wikipedia.org/wiki/Malayan_tapir">tapir</a> still living in the “Old World”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tapir sitting in a green forest." src="https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/362098/original/file-20201007-16-10up6pm.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 endangered Malayan tapir is the largest of four widely-recognized tapir species and the only one native to Asia.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Together, these creatures comprise Southeast Asia’s megafauna, second only to Africa’s in diversity. These two continental ecosystems are the last vestiges of a world largely lost – one where giants roamed the Earth. But what caused so many megafauna species to go extinct?</p>
<p>Several theories have suggested either humans, climate change, or both drove Southeast Asia’s megafauna to extinction. However, our newest research published today in <a href="https://www.nature.com/articles/s41586-020-2810-y">Nature</a> indicates it was actually the rise and fall of savannah environments that drove this extinction event.</p>
<h2>Southeast Asia’s megafauna extinctions</h2>
<p>Southeast Asia has lost many large mammal species over the Quaternary period, the past 2.6 million years. They included the world’s largest ever ape, <em><a href="https://en.wikipedia.org/wiki/Gigantopithecus">Gigantopithecus</a></em>, elephant-like creatures known as <a href="https://en.wikipedia.org/wiki/Stegodon">stegodons</a> and large water buffaloes.</p>
<p>These extinctions also include one of our closest relatives, <em>Homo erectus</em>, and two island offshoots of the human family tree – <em>Homo floresiensis</em> (the “Hobbit”) and <em>Homo luzonensis</em>. One final human species is also recorded in the genes of Southeast Asians today: the Denisovans, who were once <a href="https://cosmosmagazine.com/palaeontology/southeast-asia-was-crowded-long-before-we-turned-up/">likely widespread throughout the region</a>.</p>
<p>According to <a href="https://theconversation.com/new-analysis-finds-no-evidence-that-climate-wiped-out-australias-megafauna-53821">previous research</a>, the lead antagonist in the megafauna extinction story is humans. Some have suggested the arrival of people to new lands over the past 60,000 years or more – who then overhunted and altered this new habitat – is what led to the loss of giant mammals. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-analysis-finds-no-evidence-that-climate-wiped-out-australias-megafauna-53821">New analysis finds no evidence that climate wiped out Australia's megafauna</a>
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<p>Others researchers have contended <a href="https://theconversation.com/humans-coexisted-with-three-tonne-marsupials-and-lizards-as-long-as-cars-in-ancient-australia-138534">changes in climate</a> resulted in the extinction of the megafauna. While others suggest a <a href="https://theconversation.com/did-people-or-climate-kill-off-the-megafauna-actually-it-was-both-127803">combination</a> of both human and climate influences. </p>
<h2>Toothy insights into past environments</h2>
<p>For our research, we examined environmental changes in Southeast Asia over the <a href="https://www.nationalgeographic.com/science/prehistoric-world/quaternary/">past 2.6 million years</a>, to determine how they may have impacted extinctions. </p>
<p>We analysed the <a href="https://www.futurelearn.com/courses/archaeology/0/steps/15267">stable isotopes</a> of the teeth of mammals found in the region today, as well as those from available published fossil records.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/meet-the-giant-wombat-relative-that-scratched-out-a-living-in-australia-25-million-years-ago-141296">Meet the giant wombat relative that scratched out a living in Australia 25 million years ago</a>
</strong>
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<p>Stable isotopes are the non-radioactive forms of many elements. Stable isotopes of carbon and oxygen preserved in mammal teeth record important information on what kinds of plants those animals ate, and how wet their environments were, respectively. </p>
<p>Stable carbon isotopes are particularly helpful in recording whether animals predominantly ate leaves and fruits in shaded forests, or grasses in more open settings. This insight lets us identify shifts in environments over time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Ancient tooth fossils." src="https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/362110/original/file-20201007-14-1ux7jsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These fossil teeth from extinct Southeast Asian elephants are one example of the various teeth available in the fossil record.</span>
<span class="attribution"><span class="source">Julien Louys</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The fluctuating presence of forests</h2>
<p>During the first 1.5 million years or so of the Pleistocene (the geological epoch that lasted from about 2,580,000 to 11,700 years ago), the northern parts of Southeast Asia were largely forest, while the southern parts were woodlands or grasslands. </p>
<p>Later, from about one million years ago, forests retreated everywhere in the region and grasslands dominated. Coincident with these changes, large forest-adapted animals including <em>Gigantopithecus</em> and a giant panda relative disappeared from Southeast Asia’s northern parts.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Model recreation of Gigantopithecus blacki." src="https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=831&fit=crop&dpr=1 600w, https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=831&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=831&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1045&fit=crop&dpr=1 754w, https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1045&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/362105/original/file-20201007-20-1wpzz47.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1045&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Gigantopithecus blacki</em> was a large extinct ape that lived during the Pleistocene in what is now Southern China. It’s believed to have gone extinct about 300,000 years ago.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/22077805@N07/5484933159/in/photostream/">Greg Williams/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Later still, around 400,000 years ago, the Southeast Asian Sunda Shelf began to submerge and climate cycles changed. Because of this, forest conditions returned.</p>
<p>At the same time, grassland-adapted creatures that had filled the region, including giant hyenas, <a href="http://www.eartharchives.org/articles/stegodon-the-elephant-with-sideways-trunk/">stegodons</a>, <a href="https://www.britannica.com/animal/bovid">bovids</a> and <em>Homo erectus</em> began to disappear – and largely went extinct by the end of the Pleistocene. The remainder were driven into the rainforests. </p>
<p>By the last few tens of thousands of years, we see the first evidence of <a href="https://en.wikipedia.org/wiki/Stratification_(vegetation)">stratified</a>, closed-canopy rainforests in Southeast Asia. These have dominated the region for the past 20,000 years or so.</p>
<p>Rainforest-adapted species should have been advantaged by the return of the rainforests, but one interloper changed that. <em>Homo sapiens</em> appears to be the only species in our family tree that was able to successfully adapt to and exploit rainforest environments. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/old-teeth-from-a-rediscovered-cave-show-humans-were-in-indonesia-more-than-63-000-years-ago-82075">Old teeth from a rediscovered cave show humans were in Indonesia more than 63,000 years ago</a>
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<p>And although humans lived in Southeast Asian rainforests as early as 73,000 years ago, it was probably only <a href="https://advances.sciencemag.org/content/4/6/e1701422">in the last 10,000 years</a> that <em>Homo sapiens</em> began to fundamentally alter these habitats and exploit the mammals within. </p>
<h2>A vanishing world</h2>
<p>Southeast Asia continues to preserve some of the most critically endangered megafauna on the planet. </p>
<p>Megafauna grassland specialists were the greatest loss as a result of disappearing savannahs 400,000 years ago. Today, rainforest megafauna are also at great risk of extinction. </p>
<p>Luckily for us, our own species’ fortunes changed for the better with the emergence of typical Southeast Asian rainforests. But we’re now the very thing threatening to <a href="https://theconversation.com/guns-snares-and-bulldozers-new-map-reveals-hotspots-for-harm-to-wildlife-113361">destroy them forever</a>.</p><img src="https://counter.theconversation.com/content/147656/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julien Louys receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Patrick Roberts receives funding from the Max Planck Society and the European Research Council.</span></em></p>Several theories have suggested either humans, climate change or both drove megafauna extinctions in Southeast Asia. Our newest work suggests otherwise.Julien Louys, ARC Future Fellow, Griffith UniversityPatrick Roberts, Research Group Leader, Max Planck Institute of GeoanthropologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1428102020-07-22T19:51:24Z2020-07-22T19:51:24ZHumans 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>
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<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>
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<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>
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</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>
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<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>
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<em>
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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>
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<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 SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1412962020-06-25T20:14:17Z2020-06-25T20:14:17ZMeet the giant wombat relative that scratched out a living in Australia 25 million years ago<p>Wombats are among the most peculiar of animals. They look like a massively overgrown guinea pig with a boofy head, a waddling gait, squared-off butt, backwards-facing pouch and ever-growing molars. </p>
<p>Indeed, wombats are oddballs and don’t look much like their nearest living relatives, the koala. But koalas and wombats (collectively known as <a href="https://blogs.scientificamerican.com/tetrapod-zoology/vombatiform-radiation-part-i/">“vombatiformes”</a>) are the last survivors of a once far more diverse group of <a href="https://australian.museum/learn/species-identification/ask-an-expert/what-is-a-marsupial/">marsupials</a> whose fossil history stretches back for at least 25 million years.</p>
<p>Working out how this diverse group fizzled out to just wombats and koalas has taken centuries of extraordinary discoveries in the fossil record. We are announcing one of these today in our research <a href="https://www.nature.com/articles/s41598-020-66425-8">published in Scientific Reports</a>.</p>
<p><em>Mukupirna nambensis</em> is one of the oldest discovered Australian marsupials. Its unveiling has deepened our understanding of the relationships and evolutionary history of one of the strangest groups that once ruled this continent.</p>
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Read more:
<a href="https://theconversation.com/aboriginal-australians-co-existed-with-the-megafauna-for-at-least-17-000-years-70589">Aboriginal Australians co-existed with the megafauna for at least 17,000 years</a>
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<h2>Acupuncturing the earth</h2>
<p>In 1973 at Lake Pinpa – a small dry salt lake in South Australia – a multi-institutional expedition <a href="https://books.google.com.au/books?id=LwMkO0M1mPQC&pg=PA23&lpg=PA23&dq=dick+tedford+lake+pinpa&source=bl&ots=GgedFpuV0d&sig=ACfU3U3r3Hheo6D9PGDk6FByRV_RpwUtFA&hl=en&sa=X&ved=2ahUKEwiKs92RgZzqAhU8yjgGHRrPDrYQ6AEwAHoECAoQAQ#v=onepage&q=dick%20tedford%20lake%20pinpa&f=false">led by</a> palaeontologist Dick Tedford from the American Museum of Natural History discovered a host of extinct animals.</p>
<p>A combination of drought and strong winds had blown the sand off the surface of the lake bed, revealing the remains of animals that died after getting stuck in mud 25 million years ago. </p>
<p>One of the discoveries was a skull and partial skeleton of a large, distinctive wombat-like animal that was clearly new to science – <em>Mukupirna</em>. </p>
<p>Its fossils were found by pushing a metal rod into the clay at intervals across the lake surface, a bit like acupuncturing the skin of Mother Earth. If the rod struck something hard, the team excavated down to find what was commonly the fossilised skeleton of an otherwise unseen animal. </p>
<p>Once uncovered, they were encased in plaster shells for transport back to the Museum of Natural History, where they were subjected to years of careful preparation. Although <em>Mukupirna</em> was discovered this way in 1973, it’s only now we can formally announce this discovery to the world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=796&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=796&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=796&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1001&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1001&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343909/original/file-20200625-33557-1bz7zth.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1001&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">This photo shows the skull of the giant wombat relative <em>Mukupirna nambensis</em>. The front of the skull is towards the top of the photograph. The skull is 19.7cm long.</span>
<span class="attribution"><span class="source">Julien Louys, Griffith University and Robin Beck, University of Salford</span>, <span class="license">Author provided</span></span>
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</figure>
<h2>A mammoth find</h2>
<p>One of the most remarkable things about this marsupial is its large size, which we estimate was between 143-171kg, more than four times larger than any living wombat. </p>
<p>Its size inspired the scientific name <em>Mukupirna</em>, from the words <em>muku</em>, meaning “bones” and <em>pirna</em>, meaning “big”, in the Malyangapa and Dieri languages of Aboriginal people from central Australia. </p>
<p>We worked out the earliest vombatiform marsupials probably weighed about 5kg or less (about the size of a modern koala). That said, body weights of about 100kg, such as that of <em>Mukupirna</em>, then evolved independently at least six times in different branches of the family tree.</p>
<p>The biggest of these would be <em><a href="https://australian.museum/learn/australia-over-time/extinct-animals/diprotodon-optatum/">Diprotodon</a></em> at about three tonnes, the world’s largest marsupial.</p>
<h2>Behaviour up to scratch</h2>
<p><em>Mukupirna</em>‘s forearms were powerfully muscled and its hands may have worked like shovels, an attribute shared with modern wombats. Also like wombats, it was probably a good scratch-digger. But unlike today’s wombats, it probably couldn’t burrow. </p>
<p>Although <em>Mukupirna</em> was clearly herbivorous, unlike wombats its cheek teeth were low-crowned with well-developed roots. This indicates it couldn’t have survived on abrasive plant materials such as grasses, which today’s wombats consume without problems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343950/original/file-20200625-33563-19b66g6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Australia has three endemic species of wombat: the common wombat <em>Vombatus ursinus</em> (pictured), the northern hairy-nosed wombat (<em>Lasiorhinus krefftii</em>) and the southern hairy-nosed wombat (<em>Lasiorhinus latifrons</em>).</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>Pollens in the fossil deposit indicate that, unlike today, there were no grasslands in this area of central Australia back then. Instead, it was dominated by scrubby rainforest that was also home to possums, koalas and galloping kangaroos. </p>
<p>But alongside them were much stranger, more primitive animals that have left no living descendants. These included <em><a href="https://blogs.scientificamerican.com/tetrapod-zoology/vombatiforms-part-ii/">Ilaria</a></em>, which was a bit like a gigantic koala, <a href="https://museumsvictoria.com.au/collections-research/journals/memoirs-of-museum-victoria/volume-74-2016/pages-173-187/"><em>Ektopodon</em></a>, an arboreal marsupial with teeth like a cheese-grater and <a href="https://australian.museum/learn/australia-over-time/extinct-animals/wakaleo-vanderleuri/"><em>Wakaleo</em></a>, a leopard-sized marsupial lion with some of the most ferocious butchering teeth ever evolved by a mammal.</p>
<p>These forests were also punctuated by huge inland lakes that were home to lungfish, turtles, crocodiles, flamingos, ducks, stone curlews and even freshwater dolphins.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-new-species-of-marsupial-lion-tells-us-about-australias-past-88633">A new species of marsupial lion tells us about Australia's past</a>
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<h2>A lost land</h2>
<p>By comparing different features of <em>Mukupirna’s</em> teeth and skeleton, we discovered it to be the closest known relative of modern wombats. Yet, it was as different from wombats as wombats are from koalas, which is why it has been placed in a new family of its own: the Mukupirnidae.</p>
<p>Formal recognition of <em>Mukupirna</em> fills yet another fascinating gap in our knowledge of the weird and wonderful evolutionary history of mammals on this continent. </p>
<p>Sadly, it’s likely all mukupirnids vanished when a shift in global climate triggered an environmental change from scrubby rainforests 25 million years ago, to far lusher and more biodiverse rainforests 23 million years ago. </p>
<p>This would have resulted in more intense greenhouse conditions and an environment presumably not suited to mukupirnids.</p>
<p>Hopefully this rings a warning bell about the state of Earth’s climate now. If we can’t slow the global heating we’ve triggered, how many more of Australia’s uniquely endemic living creatures will soon join <em>Mukupirna</em> in the increasingly crowded abyss of extinction?</p><img src="https://counter.theconversation.com/content/141296/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robin Beck has received funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Julien Louys receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Mike Archer receives funding from the Australian Research Council and the Phil Creaser CREATE Fund in UNSW. </span></em></p><p class="fine-print"><em><span>Philippa Brewer works for the Natural History Museum, London</span></em></p>The extinct Mukupirna - which translates to ‘big bones’ - is estimated to have been more than four times larger than any living wombat.Robin Beck, Lecturer in Biology, University of SalfordJulien Louys, ARC Future Fellow, Griffith UniversityMike Archer, Professor, Pangea Research Centre, UNSW SydneyPhilippa Brewer, Senior Curator, Natural History MuseumLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1385342020-05-18T02:44:29Z2020-05-18T02:44:29ZHumans coexisted with three-tonne marsupials and lizards as long as cars in ancient Australia<figure><img src="https://images.theconversation.com/files/335484/original/file-20200516-138620-otfni1.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C2400%2C1353&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Life and death in tropical Australia, 40,000 years ago. Giant reptiles ruled northern Australia during the Pleistocene with mega-marsupials as their prey.
Image Credit: R. Bargiel, V. Konstantinov, A. Atuchin & S. Hocknull (2020). Queensland Museum</span> </figcaption></figure><p>When people first arrived in what is now Queensland, they would have found the land inhabited by massive animals including goannas six metres long and kangaroos twice as tall as a human.</p>
<p>We have studied fossil bones of these animals for the past decade. Our findings, <a href="https://dx.doi.org/10.1038/s41467-020-15785-w">published today in Nature Communications</a>, shed new light on the mystery of what drove these ancient megafauna to extinction. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/aboriginal-australians-co-existed-with-the-megafauna-for-at-least-17-000-years-70589">Aboriginal Australians co-existed with the megafauna for at least 17,000 years</a>
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<p>The first bones were found by the Barada Barna people during cultural heritage surveys on their traditional lands about 100 kilometres west of Mackay, at South Walker Creek Mine. Our study shares the first reliable glimpse of the giants that roamed the Australian tropics between 40,000 and 60,000 years ago. </p>
<p>These megafauna were the largest land animals to live in Australia since the time of the dinosaurs. Understanding the ecological role they played and the environmental impact of their loss remains their most valuable untold story.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335497/original/file-20200516-138624-1q7tpxq.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">Fossils are found eroding out of the ancient flood plains of South Walker Creek.</span>
<span class="attribution"><span class="source">Rochelle Lawrence, Queensland Museum.</span></span>
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<p>While megafauna lived at South Walker Creek, people had arrived on the continent and were spreading across it. Our study adds new evidence to the ongoing megafauna extinction debate, but importantly underscores how much is left to learn from the fossil record. </p>
<h2>The megafauna welcoming party</h2>
<p>We excavated fossils from four sites and made detailed studies of the sites themselves to find the age of the fossils and understand what the environment was like in the past. </p>
<p>Our findings give us an idea of what megafaunal life was like in the tropical Australian savanna over a period of about 20,000 years, from around 60,000 to 40,000 years ago. During this time, the northern megafauna were different to those from the south. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=131&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=131&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=131&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=165&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=165&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335494/original/file-20200516-138629-13zmtq6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=165&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mega-reptiles of Pleistocene tropical Australia.</span>
<span class="attribution"><span class="source">V. Konstantinov, A. Atuchin, R. Allen, S. Hocknull. Queensland Museum.</span></span>
</figcaption>
</figure>
<p>We have found at least 13 extinct species so far at <a href="https://sketchfab.com/queenslandmuseum/collections/tropical-megafauna-of-south-walker-creek">South Walker Creek</a>, with mega-reptiles as apex predators, and mega-mammals their prey. Many of the species discovered are likely new species or northern variations of their southern counterparts. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=148&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=148&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=148&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=186&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=186&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335495/original/file-20200516-138654-1yvfrsl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=186&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mega-mammals from Pleistocene tropical Australia.</span>
<span class="attribution"><span class="source">V. Konstantinov, A. Atuchin, S. Hocknull. Queensland Museum.</span></span>
</figcaption>
</figure>
<p>Some, like the extinct crocodiles, were thought to have gone extinct long before people were on the scene. However, we now know they survived in at least one place 60,000-40,000 years ago.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=761&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=761&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=761&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=957&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=957&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335496/original/file-20200516-138639-10nzxey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=957&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 giant kangaroo of South Walker Creek may be the largest kangaroo ever found. Pictured here next to the previous titleholder, <em>Procoptodon goliah</em>. Scale bar equals 1 m.</span>
<span class="attribution"><span class="source">V. Konstantinov, A. Atuchin, R. Allen, S. Hocknull. Queensland Museum.</span></span>
</figcaption>
</figure>
<p>Imagine first sighting a six-metre goanna and its Komodo Dragon-sized relative, or bumping into a land-dwelling crocodile and its plate-mail armoured aquatic cousin. The mammals were equally bizarre, including a giant bucktoothed wombat, a strange “bear-sloth” marsupial, and enormous kangaroos and wallabies. </p>
<p>A yet-to-be named giant <a href="https://sketchfab.com/queenslandmuseum/collections/giant-kangaroos-from-south-walker-creek">kangaroo</a> is the largest ever found. With an estimated mass of 274 kg, it beats the previous contender, the goliath short-faced kangaroo, <em>Procoptodon goliah</em>. </p>
<p>The biggest of all the mammals was the three-tonne marsupial <em><a href="https://theconversation.com/giant-marsupials-once-migrated-across-an-australian-ice-age-landscape-84762">Diprotodon</a></em>, and the deadliest was the pouched predator <em>Thylacoleo</em>. Living alongside these giants were other megafauna species that still survive today: the emu, the red kangaroo and the saltwater crocodile. </p>
<h2>Whodunnit? The evidence points to environmental change</h2>
<p>Why did these megafauna become extinct? It has been argued that the extinctions were due to <a href="https://science.sciencemag.org/content/292/5523/1888">over-hunting</a> by humans, and occurred shortly after people arrived in Australia. </p>
<p>However, this theory is not supported by our finding that a diverse collection of these ancient giants still survived 40,000 years ago, after humans had spread around the continent.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=496&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=496&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=496&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=623&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=623&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335506/original/file-20200516-138649-1eiche.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=623&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fossil seeds, leaves and insects help palaeontologists reconstruct the megafauna’s environment. Scale bar equals 1 mm.</span>
<span class="attribution"><span class="source">Paul Tierney, Queensland Museum.</span></span>
</figcaption>
</figure>
<p>The extinctions of these tropical megafauna occurred sometime after our youngest fossil site formed, around 40,000 years ago. The timeframe of their disappearance coincided with sustained regional changes in available water and vegetation, as well as increased fire frequency. This combination of factors may have proven fatal to the giant land and aquatic species. </p>
<p>The megafauna extinction debate will no doubt continue for years to come. New discoveries will plug up the key <a href="https://www.nature.com/articles/d41586-018-05330-7">gaps</a> in the record. With the gaps in the north of the continent the greatest yet to fill. </p>
<p>With an overlap between people and megafauna of some 15,000–20,000 years, new questions arise about co-habitation. How did people live with these giants during a period of such drastic environmental change?</p>
<h2>How much more change can Australia bear?</h2>
<p>Major environmental change and extinctions are not an unusual part of our geological past, but this time it’s personal; it involves us. Throughout the Pleistocene (the time that ended with the most recent ice age), Australia has undergone major climatic and environmental change. </p>
<p>Within the same catchment of these new megafauna sites, one <a href="https://doi.org/10.1016/j.epsl.2007.10.004">study</a> shows how major climatic upheaval beginning around 280,000 years ago caused the disappearance of a diverse rainforest fauna. This set in motion a sequence of changes to the ecosystem that culminated in the loss of the megafauna at South Walker Creek around 40,000 years ago.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/did-people-or-climate-kill-off-the-megafauna-actually-it-was-both-127803">Did people or climate kill off the megafauna? Actually, it was both</a>
</strong>
</em>
</p>
<hr>
<p>It’s still unclear what impact these long-term environmental changes and the loss of the megafauna had on the species that survived. </p>
<p>This long-term trend of extinctions has now been given a kick along by the major changes to the environment created by humans which continue today. In the early 21st century in Australia we have seen increases in floods, droughts and bushfires, and we expect these increases to continue. </p>
<p>The fossil record provides us with a window into our past that can help us understand our <a href="https://www.frontiersin.org/articles/10.3389/fevo.2017.00011/full">present</a>. As our study shows, dramatic environmental change takes a heavy toll on species survival especially for those at the top of the food chain. Will we heed the warnings from the past or suffer the consequences?</p><img src="https://counter.theconversation.com/content/138534/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Scott Hocknull receives funding from Queensland Museum and Queensland Museum Foundation.</span></em></p><p class="fine-print"><em><span>Anthony Dosseto receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Gilbert Price receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Lee Arnold receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Patrick Moss receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Renaud Joannes-Boyau receives funding from the Australian Research Council</span></em></p>These megafauna were the largest land animals to live in Australia since the time of the dinosaurs.Scott Hocknull, Senior Curator of Geosciences, Queensland Museum, and Honorary Research Fellow, The University of MelbourneAnthony Dosseto, Professor, University of WollongongGilbert Price, Lecturer in Palaeontology, The University of QueenslandLee Arnold, Associate Professor in Earth Sciences, University of AdelaidePatrick Moss, Professor, The University of QueenslandRenaud Joannes-Boyau, Senior research fellow, Southern Cross UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1326272020-04-29T15:48:10Z2020-04-29T15:48:10ZHow bison, moose and caribou stepped in to do the cleaning work of extinct mammoths<figure><img src="https://images.theconversation.com/files/330714/original/file-20200427-145560-nibdjc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3777%2C2050&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Unlike mammoths, bison survived in Alaska at the end of the last ice age.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/QvCcqTHlLCE">Hans Veth/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The extinction of one species can create ripples that transform an ecosystem. That’s particularly true for so-called “ecosystem engineer” species. Beavers are one example – they dam rivers, creating ponds and channels that <a href="https://theconversation.com/beavers-are-set-to-recolonise-the-uk-heres-how-people-and-the-environment-could-benefit-132116">offer refuge for spawning fish and small mammals</a>.</p>
<p>Large herbivores such as <a href="http://thinkelephants.blogspot.com/2012/10/elephants-ecosystems-engineers.html">elephants, horses and reindeer</a> are engineers too – they break down shrubs and trees to create open grasslands, habitats that benefit a wealth of species.</p>
<p>We know that their ancestors – such as the woolly mammoth – shaped the world around them in a similar way, but what happened to those ancient ecosystems when they died out?</p>
<p>Our <a href="https://www.cambridge.org/core/journals/quaternary-research/article/tracking-latequaternary-extinctions-in-interior-alaska-using-megaherbivore-bone-remains-and-dung-fungal-spores/BD3C13789FBB262EDCA8432CBB47067E">new research published in the journal Quaternary Research</a> studied the extinction of mammoth, wild horse and saiga antelope towards the end of the last ice age in interior Alaska, analysing fossilised <a href="https://methodsblog.com/2016/07/19/european-bison/">dung fungal spores</a> recovered from the bottom of lakes and <a href="https://www.nps.gov/articles/aps-17-1-4.htm">ancient bones recovered from buried</a> sediments.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-effect-did-the-asteroid-that-wiped-out-the-dinosaurs-have-on-plants-and-trees-132386">Curious Kids: What effect did the asteroid that wiped out the dinosaurs have on plants and trees?</a>
</strong>
</em>
</p>
<hr>
<p>We wanted to know how ancient ecosystems responded to these species dying out so that it might teach us more about mass extinctions today. What we discovered could offer hope for modern ecosystems facing biodiversity loss.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=435&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=435&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330716/original/file-20200427-145536-v86bx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=435&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A museum replica of a woolly mammoth. Mammoths helped maintain open habitats by grazing herbs, trees and bushes.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/dvur-kralove-czech-republic-08132013-big-1024532596">Noska Photo/Shutterstock</a></span>
</figcaption>
</figure>
<h2>How ancient ecosystems coped with extinctions</h2>
<p>The late-Quaternary extinctions occurred towards the end of the last ice age. In North America, they saw the loss of large herbivores and carnivores, whose relatives still roam other continents as elephants, wild horses and tigers. This was a period of rapid climate change and growing pressure from humans.</p>
<p><a href="https://www.researchgate.net/publication/269820457_Late_Quaternary_megafaunal_extinctions_on_the_continents_A_short_review">Previous research showed that 69% of large mammals</a> were lost from North America around this time. Similar losses were seen on other continents, <a href="https://www.discovermagazine.com/planet-earth/dung-fungus-reveal-that-humans-not-climate-change-killed-australias-giant-beasts">including Australia</a>. The diversity of mammal species shrank, but more significant was the <a href="https://doc.rero.ch/record/210391/files/PAL_E4398.pdf">crash in numbers of all mammals</a>, including species that survived the extinction event.</p>
<p><a href="https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.12576">Previous research</a> showed that elsewhere in the Americas, the loss of ecosystem engineers like the woolly mammoth led to an explosion in plant growth, as trees and shrubs were no longer grazed and browsed so intensively. In turn, there were larger and more frequent wildfires.</p>
<p>But in Alaska, our results revealed that other species of wild herbivores, including bison, moose, caribou and musk ox, increased in abundance, making up for the loss of mammoths, saiga antelopes and wild horses.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=639&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=639&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330718/original/file-20200427-145499-105esni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=639&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Saiga antelopes used to roam North America, but they are now only found in scattered pockets of Asia.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Saiga_antelope#/media/File:Saiga_antelope_at_the_Stepnoi_Sanctuary.jpg">Andrey Giljov/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>This suggests that as extinctions occurred, other large herbivores were able to fill the gap, partially taking over the lost role of ecosystem engineer. This insight from 13,000 years ago could offer hope for modern conservationists. Substituting an extinct ecosystem engineer with a similar species still living today may work to revive lost ecological processes.</p>
<p>Reintroducing large herbivores in this way is often referred to as “<a href="https://www.esf.edu/efb/parry/Invert_Cons_14_Readings/Seddon_etal_2014.pdf">rewilding</a>”. Today’s landscapes on most continents are <a href="https://www.chrispackham.co.uk/news/what-is-rewilding">empty of large vertebrate animals</a>, largely because of the late Quaternary extinctions we studied. <a href="https://www.researchgate.net/publication/257973653_Rewilding_North_America">One of the key arguments</a> behind rewilding is that bringing some of those species back to landscapes could boost biodiversity more broadly and create more diverse, resilient ecosystems.</p>
<p>But without resurrecting the woolly mammoth, our research indicates it may be possible to bring back some of the ecosystem engineering benefits of extinct species by reintroducing their living relatives or substitute species, ultimately helping surviving plants and animals to thrive.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/could-resurrecting-mammoths-help-stop-arctic-emissions-95956">Could resurrecting mammoths help stop Arctic emissions?</a>
</strong>
</em>
</p>
<hr>
<p>Our work in Alaska shows that the consequences of engineer extinctions are not always overwhelmingly negative. Studying this rare instance when ecosystems coped better with extinctions can help us design more effective conservation measures for megaherbivores today. </p>
<p>A good example of creative thinking in conservation can be found in Columbia. Here, pet hippos that escaped from Pablo Escobar’s private collection have multiplied in the wild and now appear to be recreating processes that were <a href="https://www.theguardian.com/environment/2020/mar/24/pablo-escobars-cocaine-hippos-show-how-invasive-species-can-restore-a-lost-world-aoe">lost thousands of years ago</a> when native megaherbivores died out. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330721/original/file-20200427-145499-1a33zx6.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">These hippos are technically invasive species in Colombia and are wild descendants of Pablo Escobar’s pets.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hippopotamus-colombia-1351698167">Perla Sofia/Shutterstock</a></span>
</figcaption>
</figure>
<p>This includes the creation of well trodden hippo paths between wetlands and feeding areas on firmer ground, which help deepen water channels, disperse seeds and fertilise wetlands. Over 13,000 years ago, these processes would have been carried out by the now extinct <a href="https://prehistoric-fauna.com/Macrauchenia-patagonica">giant llama</a>, and semi-aquatic <a href="https://dcpaleo.org/notoungulata/">notoungulata</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=358&fit=crop&dpr=1 600w, https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=358&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=358&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=450&fit=crop&dpr=1 754w, https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=450&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/330738/original/file-20200427-145544-1ud4ur2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=450&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Notoungulata were hoofed, sometimes heavy-bodied grazing mammals that inhabited South America from 57 million years to 11,000 years ago.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Notoungulata#/media/File:Toxodon.jpg">ArthurWeasley/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Although it may seem an eternity since mammoths walked the Earth, our research suggests that some of the effects they had on the world around them can be resurrected without a Jurassic Park-style breakthrough in <a href="https://www.thoughtco.com/the-resurrection-of-extinct-animals-1091999">de-extinction</a>.</p><img src="https://counter.theconversation.com/content/132627/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Maarten van Hardenbroek van Ammerstol receives funding from UKRI/NERC. </span></em></p><p class="fine-print"><em><span>Ambroise Baker 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 historical record is full of surprises – and it could encourage conservationists to think more creatively.Ambroise Baker, Lecturer in Biology, Teesside UniversityMaarten van Hardenbroek van Ammerstol, Lecturer in Physical Geography, Newcastle UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1287992020-01-03T09:36:46Z2020-01-03T09:36:46ZHow the extinction of ice age mammals may have forced us to invent civilisation<figure><img src="https://images.theconversation.com/files/307690/original/file-20191218-11900-s0uqmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Hunting_Woolly_Mammoth.jpg">Wikimedia Commons/Cloudordinary</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Why did we take so long to invent civilisation? Modern <em>Homo sapiens</em> first evolved roughly <a href="https://theconversation.com/modern-humans-evolved-100-000-years-earlier-than-we-thought-and-not-just-in-east-africa-78875">250,000 to 350,000</a> years ago. But initial steps towards civilisation – harvesting, then domestication of crop plants – began only <a href="https://science.sciencemag.org/content/288/5471/1602?ijkey=3c1b653d8a610f044ce71bd2e41594fe7be12060&keytype2=tf_ipsecsha">around 10,000 years ago</a>, with the first civilisations appearing <a href="https://link.springer.com/article/10.1007/s10814-010-9041-y">6,400 years ago</a>.</p>
<p>For 95% of our species’ history, we didn’t farm, create large settlements or complex political hierarchies. We lived in small, nomadic bands, hunting and gathering. Then, something changed. </p>
<p>We transitioned from hunter-gatherer life to plant harvesting, then cultivation and, finally, cities. Strikingly, this transition happened only after the ice age megafauna – mammoths, giant ground sloths, giant deer and horses – disappeared. The reasons humans began farming still <a href="https://phys.org/news/2019-04-food-thought-farming.html">remain unclear</a>, but the disappearance of the animals we depended on for food may have forced our culture to evolve. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306925/original/file-20191214-85428-1rtscoo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Humans hunted wild cattle, horses, and deer in France 17,000 years ago.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Early humans were smart enough to farm. All groups of modern humans have similar levels of intelligence, suggesting our cognitive capabilities evolved before these populations separated <a href="https://science.sciencemag.org/content/358/6363/652/tab-pdf">around 300,000 years ago</a>, then changed little afterwards. If our ancestors didn’t grow plants, it’s not that they weren’t clever enough. Something in the environment prevented them – or they simply didn’t need to. </p>
<p>Global warming at the end of the last glacial period, 11,700 years ago, probably <a href="https://www.cambridge.org/core/journals/american-antiquity/article/was-agriculture-impossible-during-the-pleistocene-but-mandatory-during-the-holocene-a-climate-change-hypothesis/246B240BFFFBE904B1AC31296AD72949">made farming easier</a>. Warmer temperatures, longer growing seasons, higher rainfall and <a href="https://www.journals.uchicago.edu/doi/pdfplus/10.1086/605359">long-term climate stability</a> made more areas suitable for cultivation. But it’s unlikely farming had been impossible everywhere. And Earth saw <a href="https://science.sciencemag.org/content/292/5517/686">many such warming events</a> – 11,700, 125,000, 200,000 and 325,000 years ago – but earlier warming events didn’t spur experiments in farming. Climate change can’t have been the only driver.</p>
<p>Human migration probably contributed as well. When our species expanded from southern Africa throughout <a href="https://science.sciencemag.org/content/358/6363/652/tab-pdf">the African continent</a>, into <a href="https://www.nature.com/articles/nature22968">Asia</a>, Europe and then <a href="https://science.sciencemag.org/content/365/6456/891">the Americas</a>, we found new environments and <a href="https://nph.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8137.2012.04253.x">new food plants</a>. But people occupied these parts of the world long before farming began. Plant domestication lagged human migration by tens of millennia.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306927/original/file-20191214-85376-sg48bc.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">Rye, one of the first crops.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>If opportunities to invent farming already existed, then the delayed invention of agriculture suggests our ancestors didn’t need, or want, to farm.</p>
<p>Agriculture has significant disadvantages compared to foraging. Farming <a href="https://www.discovermagazine.com/planet-earth/the-worst-mistake-in-the-history-of-the-human-race">takes more effort and offers less leisure time and an inferior diet</a>. If hunters are hungry in the morning, they can have food on the fire at night. Farming requires hard work today to produce food months later – or not at all. It requires storage and management of temporary food surpluses to feed people year round. </p>
<p>A hunter having a bad day can hunt again tomorrow or seek richer hunting grounds elsewhere, but farmers, tied to the land, are at the mercy of nature’s unpredictability. Rains arriving too soon or too late, droughts, frosts, blights or locusts can cause crop failure – and famine. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/307696/original/file-20191218-11900-14xokd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Agriculture has many disadvantages over hunting.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Ancient_Egyptian_agriculture#/media/File:Maler_der_Grabkammer_des_Sennudem_001.jpg">Wikipedia</a></span>
</figcaption>
</figure>
<p>Agriculture has military disadvantages as well. Hunter-gatherers are mobile and can travel long distances to attack or retreat. Constant practice with spears and bows made them <a href="https://theconversation.com/were-other-humans-the-first-victims-of-the-sixth-mass-extinction-126638">deadly fighters</a>. Farmers are rooted to their fields, their schedules dictated by the seasons. They are predictable, stationary targets, whose food stockpiles tempt hungry outsiders.</p>
<p>And having evolved to the lifestyle, humans may simply have loved being nomadic hunters. The Comanche Indians <a href="https://www.amazon.com/dp/B003KN3MDG/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1">fought to the death</a> to preserve their hunting lifestyle. The Kalahari Bushmen of southern Africa <a href="https://www.bbc.co.uk/news/world-africa-24821867">continue to resist</a> being turned into farmers and herders. Strikingly, when Polynesian farmers encountered New Zealand’s abundant flightless birds, they largely abandoned agriculture, creating the Maori <a href="https://teara.govt.nz/en/1966/maori-material-culture">moa-hunter culture</a>.</p>
<h2>Hunting abandoned</h2>
<p>Yet something changed. From 10,000 years ago onward, humans repeatedly abandoned the hunter-gatherer lifestyle for farming. It may be that after the extinction of mammoths and other megafauna from the Pleistocene epoch, and the overhunting of surviving game, the hunter-gatherer lifestyle became less viable, pushing people to harvest and then cultivate plants. Perhaps civilisation wasn’t born out of a drive to progress, <a href="https://www.penguinrandomhouse.com/books/112492/plagues-and-peoples-by-william-h-mcneill/">but disaster</a>, as ecological catastrophe forced people to abandon their traditional lifestyles.</p>
<p>As humans left Africa to colonise new lands, large animals disappeared everywhere we set foot. In Europe and Asia, megafauna like wooly rhinos, mammoths, and Irish Elk vanished <a href="https://www.researchgate.net/profile/Adrian_Lister/publication/264785182_Patterns_of_Late_Quaternary_megafaunal_extinctions_in_Europe_and_northern_Asia/links/53f0e69f0cf2711e0c431517.pdf">around 40,000 to 10,000 years ago</a>. In Australia, giant kangaroos and wombats disappeared <a href="https://science.sciencemag.org/content/292/5523/1888">46,000 years ago</a>. In North America, horses, camels, giant armadillos, mammoths and ground sloths declined and disappeared from <a href="https://science.sciencemag.org/content/326/5956/1100.full">15,000 to 11,500 years ago</a>, followed by extinctions in South America <a href="https://www.sciencedirect.com/science/article/pii/S1040618209004236">14,000 to 8,000 years ago</a>. After people spread to the Caribbean Islands, <a href="https://www.pnas.org/content/100/19/10800.short">Madagascar</a>, <a href="https://www.sciencedirect.com/science/article/pii/S0277379114003734">New Zealand</a> and <a href="https://science.sciencemag.org/content/217/4560/633">Oceania</a>, their megafauna vanished as well. Megafaunal extinctions inevitably followed humans.</p>
<p>Harvesting big game like <a href="https://www.pnas.org/content/112/14/4263.short">horses, camels</a> and <a href="https://science.sciencemag.org/content/334/6054/351">elephants</a> produces <a href="https://www.researchgate.net/publication/24107608_The_Primitive_Hunter_Culture_Pleistocene_Extinction_and_the_Rise_of_Agriculture/link/57dd854f08ae4e6f1849a954/download">a better return</a> than hunting small game like rabbits. But large animals like elephants reproduce slowly, and have few offspring compared to small animals like rabbits, <a href="https://www.researchgate.net/publication/24107608_The_Primitive_Hunter_Culture_Pleistocene_Extinction_and_the_Rise_of_Agriculture/link/57dd854f08ae4e6f1849a954/download">making them vulnerable to overharvesting</a>. And so everywhere we went, our human ingenuity – hunting with spear-throwers, herding animals with fire, stampeding them over cliffs – meant we harvested large animals faster than they could replenish their numbers. It was arguably the first sustainability crisis. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308109/original/file-20191220-11929-1gc4m3g.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">With our hunting prey gone, we were forced to invent civilisation.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/egypt-sakkara-step-pyramid-king-djoser-109821740">WitR/Shutterstock</a></span>
</figcaption>
</figure>
<p>With the old way of life no longer viable, humans would have been forced to innovate, increasingly focusing on <a href="https://www.researchgate.net/publication/24107608_The_Primitive_Hunter_Culture_Pleistocene_Extinction_and_the_Rise_of_Agriculture/link/57dd854f08ae4e6f1849a954/download">gathering, then cultivating plants to survive</a>. This let human populations expand. Eating plants rather than meat is <a href="https://www.google.com/search?q=jared+diamong+third+chimpanzee&rlz=1C5CHFA_enGB841GB841&oq=jared+diamong+third+chimpanzee&aqs=chrome..69i57j35i39l2j0l4j69i60.4797j0j7&sourceid=chrome&ie=UTF-8">a more efficient use of land</a>, so farming can support more people in the same area than hunting. People could settle permanently, build settlements, then civilisations. </p>
<p>The archaeological and fossil records tell us our ancestors could have pursued farming, but did only so after they had little alternative. We probably would have continued hunting horses and mammoths forever, but we were just too good at it, and likely wiped out our own food supply.</p>
<p>Agriculture and civilisation may have been invented not because they were an improvement over our ancestral lifestyle, but because we were left no choice. Agriculture was desperate attempt to fix things when we took more than the ecosystem could sustain. If so, we abandoned the life of ice age hunters to create the modern world, not with foresight and intent, but by accident, because of an ecological catastrophe we created thousands of years ago.</p><img src="https://counter.theconversation.com/content/128799/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R. Longrich 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>Overhunting of megafauna such as mammoths may have force us to take up farming, ultimately leading to modern societyNicholas R. Longrich, Senior Lecturer, Paleontology and Evolutionary Biology, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1278032019-12-03T18:36:08Z2019-12-03T18:36:08ZDid people or climate kill off the megafauna? Actually, it was both<figure><img src="https://images.theconversation.com/files/304383/original/file-20191129-45248-1sspxz7.jpg?ixlib=rb-1.1.0&rect=4%2C9%2C1497%2C1116&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When freshwater dried up, so did many megafauna species.</span> <span class="attribution"><a class="source" href="https://epicaustralia.org.au">Centre of Excellence for Australian Biodiversity and Heritage</a>, <span class="license">Author provided</span></span></figcaption></figure><p>Earth is now firmly in the grips of its sixth “mass extinction event”, and it’s mainly <a href="https://theconversation.com/radical-overhaul-needed-to-halt-earths-sixth-great-extinction-event-68221">our fault</a>. But the modern era is definitely not the first time humans have been implicated in the extinction of a wide range of species.</p>
<p>In fact, starting about 60,000 years ago, many of the world’s largest animals disappeared forever. These “<a href="https://australianmuseum.net.au/learn/australia-over-time/megafauna/">megafauna</a>” were first lost in <a href="http://sahultime.monash.edu.au/explore.html">Sahul</a>, the supercontinent formed by Australia and New Guinea during periods of low sea level. </p>
<p>The causes of these extinctions have been debated for decades. Possible culprits include <a href="https://theconversation.com/climate-change-wiped-out-australias-megafauna-13966">climate change</a>, <a href="https://theconversation.com/new-analysis-finds-no-evidence-that-climate-wiped-out-australias-megafauna-53821">hunting or habitat modification by the ancestors of Aboriginal people</a>, or a <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2015.2399">combination of the two</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-mass-extinction-and-are-we-in-one-now-122535">What is a 'mass extinction' and are we in one now?</a>
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<p>The main way to investigate this question is to build timelines of major events: when species went extinct, when people arrived, and when the climate changed. This approach relies on using <a href="https://theconversation.com/new-analysis-finds-no-evidence-that-climate-wiped-out-australias-megafauna-53821">dated fossils from extinct species</a> to estimate when they went extinct, and archaeological evidence to determine <a href="https://theconversation.com/an-incredible-journey-the-first-people-to-arrive-in-australia-came-in-large-numbers-and-on-purpose-114074">when people arrived</a>. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-incredible-journey-the-first-people-to-arrive-in-australia-came-in-large-numbers-and-on-purpose-114074">An incredible journey: the first people to arrive in Australia came in large numbers, and on purpose</a>
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<p>Comparing these timelines allows us to deduce the likely windows of coexistence between megafauna and people.</p>
<p>We can also compare this window of coexistence to long-term models of climate variation, to see whether the extinctions coincided with or shortly followed abrupt climate shifts.</p>
<h2>Data drought</h2>
<p>One problem with this approach is the scarcity of reliable data due to the extreme rarity of a dead animal being fossilised, and the low probability of archaeological evidence being preserved in Australia’s harsh conditions.</p>
<p>This means many studies are restricted to making conclusions regarding drivers of extinction at the scale of single palaeontological sites or of specific archaeological sites. </p>
<p>Alternatively, timelines can be constructed by including evidence across large spatial scales, such as over the <a href="https://theconversation.com/new-analysis-finds-no-evidence-that-climate-wiped-out-australias-megafauna-53821">entire continent of Australia</a>. </p>
<p>Unfortunately, this “lumping” of the available evidence across many different sites disregards the variation in the relative contribution of different extinction drivers across the landscape.</p>
<h2>Mapping extinction</h2>
<p>In our <a href="https://www.nature.com/articles/s41467-019-13277-0">research published in Nature Communications</a>, we developed advanced mathematical tools to map the regional patterns of the timing of megafauna disappearances and the arrival of Aboriginal ancestors across south-eastern Australia. </p>
<p>Based on these new maps, we can now work out where humans and megafauna coexisted, and where they did not. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=653&fit=crop&dpr=1 600w, https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=653&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=653&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=821&fit=crop&dpr=1 754w, https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=821&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/304225/original/file-20191128-178078-mo80fk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=821&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Areas of coexistence and non-coexistence between humans and megafauna.</span>
<span class="attribution"><span class="source">F. Saltré</span></span>
</figcaption>
</figure>
<p>It turns out humans coexisted with the megafauna over about 80% of south-eastern Sahul for up to 15,000 years, depending on the region in question. </p>
<p>In other regions such as Tasmania, there was no such coexistence. This rules out humans as a likely driver of megafauna extinction in those areas. </p>
<p>We then aligned these windows of coexistence and non-coexistence in each part of the landscape with several environmental measures derived from climate simulations over the past 120,000 years. This gave us an idea about which factors best explained the timing of megafauna extinction in each part of the landscape. </p>
<p>Despite a major effect on extinctions in areas where megafauna and people did not coexist, there was nothing at all to explain the timing of megafauna extinctions in places where megafauna and people coexisted. </p>
<p>This surprising result suggested that we had missed something important in our analyses.</p>
<h2>Connecting the dots</h2>
<p>The major flaw in our approach was to analyse each location independently of its surroundings. Our initial model had failed to take account of the fact that an extinction in one place can affect an extinction in another location nearby. </p>
<p>Once we changed our model to incorporate these effects, the real picture finally emerged. We found that megafauna extinctions in areas were they coexisted with humans were most likely caused by a combination of human pressure and access to water.</p>
<p>In the other 20% of the landscape, where humans and megafauna did not coexist, we found that extinctions likely occurred because of a lack of plants, driven by increasingly dry conditions. This doomed many plant-eating megafauna species to extinction. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/304380/original/file-20191129-45296-yb8dhl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Relative importance (in %) of variables best describing the timing (first row) and the directional gradient (second row) of megafauna extinction in areas of non-coexistence (first column) and coexistence (second column) of people and megafauna.</span>
<span class="attribution"><span class="source">F. Saltré</span></span>
</figcaption>
</figure>
<h2>Space is key</h2>
<p>This is the first evidence that tens of thousands of years ago, the combination of humans and climate change was already making species more likely to disappear. Yet this pattern was invisible if we ignored the interconnectedness of the various regions involved. </p>
<p>This might be just the beginning we need for a new, more nuanced treatment of environmental change in the deep past in other regions of the world.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/11-000-scientists-warn-climate-change-isnt-just-about-temperature-126261">11,000 scientists warn: climate change isn't just about temperature</a>
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<p>More importantly, our results reinforce <a href="https://theconversation.com/11-000-scientists-warn-climate-change-isnt-just-about-temperature-126261">scientists’ stark warning</a> about the immediate future of our planet’s plants and wildlife. Given rising human pressures on the natural world, coupled with an unprecedented pace of global warming, modern species are facing similar ravages.</p><img src="https://counter.theconversation.com/content/127803/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Frédérik Saltré and Katharina J. Peters 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>A drying climate and the arrival of people together finished off Australia’s megafauna.Frédérik Saltré, Research Fellow in Ecology & Associate Investigator for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityCorey J. A. Bradshaw, Matthew Flinders Fellow in Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityKatharina J. Peters, Postdoctoral Fellow, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1251322019-11-20T19:16:38Z2019-11-20T19:16:38ZExtinction of ice age giants likely drove surviving animals apart<figure><img src="https://images.theconversation.com/files/302600/original/file-20191120-524-tbd33d.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4281%2C2843&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Extinction of the woolly mammoth and other megafauna caused surviving animals to go their separate ways.</span> <span class="attribution"><span class="source">Wikimedia </span></span></figcaption></figure><p>As the world grapples with an extinction crisis, our large mammals are among the most endangered. These threatened species – rhinos, pandas, tigers, polar bears and the like – greatly influence their ecosystems. So what will happen to the smaller animals left behind?</p>
<p>Clues from a past megafaunal extinction could give us the answer. Thousands of years ago, many large mammals went extinct including mammoths, saber-toothed cats and Australia’s giant wombat. The extinctions happened at different times, shortly after human colonisation on each continent. </p>
<p>A study I led, <a href="https://science.sciencemag.org/content/365/6459/1305">published in the journal Science</a>, has found after the megafauna disappeared, many surviving mammal species went their separate ways. This weakened connections between species and may have made ecosystems more vulnerable. </p>
<p>As human activity drives modern megafauna towards extinction, our study gives valuable insights into the potential repercussions for smaller survivors.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/302594/original/file-20191120-474-vx0b6l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many large mammals, such as the polar bear, are at risk of extinction.</span>
<span class="attribution"><span class="source">Henry H. Holdsworth/Natural Habi</span></span>
</figcaption>
</figure>
<h2>Surprise results</h2>
<p>Our team analysed the fossil records of 93 mammal species at hundreds of sites in North America, dating back up to 21,000 years, before the extinctions began.</p>
<p>We then determined the extent to which a particular species lived alongside others at each site. We found that after the extinction of large mammals, smaller mammals often distanced themselves from neighbouring species and were found together much less often than expected.</p>
<p>Surprisingly, this separation occurred while many survivors were claiming new habitats after the extinctions - which meant the potential space for co-habitation had actually increased.</p>
<p>The below diagrams show how animal species may have lived alongside each other before and after the megafauna extinctions. In the first, two species occupied the same area while co-habiting (orange sites). In the second, animals occupied the same area but were more segregated (red and yellow sites).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299572/original/file-20191030-17888-d1d512.png?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"></span>
<span class="attribution"><span class="source">Created by Anikó Tóth</span></span>
</figcaption>
</figure>
<p>Such segregation suggests a change in interactions between species after the extinction event. Survivors may have rapidly become more abundant as large mammals disappeared, causing more competitive interactions. This could have prompted them to exclude each another from individual sites.</p>
<p>Our analysis suggests the repercussions of megafauna extinctions are still being felt today - leading to species increasingly segregated across continents, and interacting more opportunistically.</p>
<hr>
<p><strong><em>Hover over an animal silhouette to learn more about it. Notice the size difference between the largest North American fauna 12,000 years ago and today</em></strong></p>
<p><iframe id="tc-infographic-446" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/446/8d436f7689ff8919ba426622354691e5c5fd820a/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
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<h2>Animals need each other</h2>
<p>Connections between species large and small are the lifeblood of a functioning ecosystem, making it stable and resilient. Today’s large mammals are comparatively smaller than the megafauna of the last ice age. However, they still play a vital role in shaping ecosystems. </p>
<p>Just like in the past, modern large mammals may carry out pest control, aid seed dispersal and spread nutrients (by walking long distances and pooping out digested vegetation). This benefits humans and other species. </p>
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<p>
<em>
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Read more:
<a href="https://theconversation.com/why-we-need-to-protect-the-extinct-woolly-mammoth-122256">Why we need to protect the extinct woolly mammoth</a>
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<p>Some large animals also shape and create homes for others. For example, elephants in Africa push over trees to create open grasslands, much like their Pleistocene-era cousin, the Columbian mammoth. This enables other species adapted to grasslands, such as gazelles and zebras, to share the habitat. </p>
<p>If elephants became extinct and no longer pushed over trees, grasslands would change and remaining animals may die or move away. In this way, the loss of interactions may make the ecosystem less stable and more vulnerable. </p>
<p>And animal extinctions have a snowball effect when it comes to species interactions. If half the species in a community go extinct, at least three quarters of the possible interactions in the system die with them.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299794/original/file-20191101-26419-l2ixb5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Thylacoleo carnifex, the extinct marsupial lion.</span>
<span class="attribution"><span class="source">Image credit: Mauricio Antón</span></span>
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</figure>
<h2>Lessons for Australian conservation</h2>
<p>Although our study was restricted to North America, its findings have the potential to inform conservation efforts in Australia and shine a light into the past.</p>
<p>Australia’s fossil record and historical accounts document many species of large mammals which have become extinct. For example, more than 40,000 years ago humans <a href="https://science.sciencemag.org/content/292/5523/1888">wiped out large carnivores</a> such as the marsupial lion and more recently, the Tasmanian tiger. </p>
<p>People also introduced invasive medium-sized carnivores such as foxes and feral cats, the spread of which went unchecked for years. This devastated the unique and diverse suite of smaller Australian marsupials. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-end-to-endings-how-to-stop-more-australian-species-going-extinct-111627">An end to endings: how to stop more Australian species going extinct</a>
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<p>Today, the extermination of feral cats is a major conservation problem in Australia. Had the marsupial lion still been around, feral cats may have been killed and marginalised by these larger animals, slowing their spread.</p>
<p>When planning animal conservation and management, it may be just as important to protect interactions as it is to save individual species. When introducing or eliminating species as part of environmental initiatives, it’s crucial to consider all possible interactions we are adding, as well as those we are taking away.</p><img src="https://counter.theconversation.com/content/125132/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aniko Blanka Toth 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>After the woolly mammoth and other megafauna became extinct, surviving animals mingled less. This has big implications for modern conservation.Aniko Blanka Toth, Postdoctoral Fellow, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1077272019-04-05T17:12:13Z2019-04-05T17:12:13ZHumans are not off the hook for extinctions of large herbivores – then or now<figure><img src="https://images.theconversation.com/files/267823/original/file-20190405-180010-1j7h108.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hippos at Gorongosa National Park.</span> <span class="attribution"><span class="source">Brett Kuxhausen, Author provided</span>, <span class="license">Author provided</span></span></figcaption></figure><p>What triggered the decline and eventual extinction of many megaherbivores, the giant plant-eating mammals that roamed the Earth millions of years ago, has long been a mystery. These animals, which weighed 1,000kg or more and included the ancient relatives of modern elephants, rhinos, hippos and giraffes, reached <a href="https://www.sciencedirect.com/science/article/abs/pii/S0140196306000425?via%3Dihub">a peak of diversity</a> in Africa some 4.5m years ago during the Pliocene epoch (between 5.3m and 2.6m years ago). After this, their numbers slowly declined, in a trend that continued into the Pleistocene (2.6m years ago to roughly 11,000 years ago).</p>
<p>Both the Earth’s climate and hominins – our early <a href="https://www.newscientist.com/article/dn9989-timeline-human-evolution/">human ancestors</a> – have in the past been blamed for this change. However, a <a href="https://www.ncbi.nlm.nih.gov/pubmed/30467167">recent paper</a> argued that the gradual extinction of megaherbivores occurred because of long-term environmental changes and that developments in hominin behaviour – such as wielding tools and using fire – did not impact megaherbivore decline. </p>
<p>While this seems to be true of the early decline in megaherbivore population, we argue that our ancient human ancestors may well still have contributed to more recent megaherbivore extinctions. What’s more, we’re repeating the pattern today.</p>
<h2>Ancient hominins in a land of giants</h2>
<p>The genus <em>Australopithecus</em> is among the best known hominins from the Pliocene. Dating as far back as <a href="https://www.ncbi.nlm.nih.gov/pubmed/28844328">4.2m years</a>, they shared food and water-rich woodland and grassland environments with a dozen species of large herbivores, including <a href="https://www.ncbi.nlm.nih.gov/pubmed/28992952">three giraffids</a>, <a href="https://www.ncbi.nlm.nih.gov/pubmed/28966046">two hippos</a>, <a href="https://www.ncbi.nlm.nih.gov/pubmed/28966048">two species of rhinoceros</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0047248418303919">five species</a> of <a href="https://ucmp.berkeley.edu/mammal/mesaxonia/proboscidea.php">proboscideans</a> – a trunked and tusked group of animals that includes modern elephants and extinct mammoths and mastodons.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267838/original/file-20190405-180041-13thjmh.png?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">Kanapoi, Kenya, where 4.2m year old Australopithecus was found.</span>
<span class="attribution"><span class="source">René Bobe, Author provided</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p><em>Australopithecus</em> were omnivorous – but there is no evidence that they hunted large mammals. In fact, its likely that megaherbivores <a href="https://www.sciencedirect.com/science/article/pii/S0047248418303919">played a beneficial ecological role</a> for these early hominins. Thousands of years of grazing and migration gradually opened up wooded environments, which created the perfect blend of woodland and grassland in which <a href="https://www.ucpress.edu/book/9780520257214/cenozoic-mammals-of-africa">early hominins thrived</a>. In these Pliocene landscapes, our ancestors and the ancestors of modern elephants, rhinos, giraffes and hippos coexisted in relative harmony.</p>
<p>However, major climatic and environmental changes were to separate the fates of hominins and megaherbivores. Starting in the late Miocene epoch (the period just before the Pliocene), and continuing into the Pliocene and subsequent Pleistocene, <a href="http://www.essc.psu.edu/essc_web/seminars/spring2006/jan18/Zachosetal.pdf">ocean waters started cooling</a>, atmospheric CO<sub>2</sub> started decreasing and, in eastern Africa, grasslands <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-earth-060614-105310">began expanding</a>, reducing woodland cover. There is also <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4283521/">evidence of increasingly frequent fires</a>.</p>
<p>Early hominins such as <em>Australopithecus</em>, comfortable in both grassland and woodland environments, were well-adapted to these changing climatic and environmental conditions, as shown by their rich fossil record at several sites in Africa. However, megaherbivore species that were only comfortable in wooded environments struggled to survive.</p>
<h2>Changing behaviour of hominins</h2>
<p>By the time more sophisticated hominins such as <em>Homo erectus</em> emerged 1.8m years ago, megaherbivores had already been in decline for more than two million years, according to the recent study’s authors. But that doesn’t mean that <em>Homo erectus</em> didn’t hammer the final nails into the collective megaherbivore coffin. <a href="http://science.sciencemag.org/content/362/6417/892">We believe</a> that current archaeological records are too poor to document the effects that hominin behavioural innovations such as tool use had on large mammal extinctions in the Pleistocene period.</p>
<p>For example, we don’t know how the <a href="https://www.journals.uchicago.edu/doi/pdfplus/10.1086/692530">early use of fire</a> – likely as much as 1.5m years ago – influenced landscapes and foraging patterns of large herbivores. There is also no clear indication as to when hominins started hunting large herbivores. Could they have hunted large mammals during droughts, as some carnivores do <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.2006.00181.x">today</a>? We believe that the question of what role hominins such as <em>Homo erectus</em> had in the decline of megaherbivores remains open, despite the recent study’s findings.</p>
<p>As we approach more recent periods of Earth history, there’s <a href="http://rspb.royalsocietypublishing.org/content/281/1787/20133254">strong evidence that our species</a>, <em>Homo sapiens</em>, played a major role in the wave of global megaherbivore extinctions that occurred toward the end of the Pleistocene era, between about 50,000 and 10,000 years ago. By this time, hominins were expanding over much of the globe and had become <a href="http://advances.sciencemag.org/content/5/3/eaau4546">sophisticated hunters of large animals</a>. It was during this period that species of mastodons, woolly rhinos and giant ground sloths, among many others, were finally wiped out. </p>
<h2>A new wave of extinction</h2>
<p>Of course, in modern times, humans are responsible for causing such profound biodiversity losses that we may be undergoing a “<a href="http://advances.sciencemag.org/content/1/5/e1400253">sixth mass extinction</a>”, a calamity comparable to the worst biodiversity crises in Earth’s long history of 4.5 billion years. The <a href="http://advances.sciencemag.org/content/1/4/e1400103">current evidence</a> shows that human encroachment and hunting are collapsing the natural environments of large herbivores such as elephants, rhinos, giraffes and hippos, sending their populations spiralling into decline.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=347&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=347&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=347&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=436&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=436&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267837/original/file-20190405-180036-1f89w7f.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=436&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Gorongosa National Park.</span>
<span class="attribution"><span class="source">Brett Kuxhausen, Author provided</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But in the sea of bad news of ongoing extinctions and habitat degradation, there are some islands of hope that all is not lost. At the southern end of East Africa’s Great Rift Valley, Gorongosa National Park in Mozambique is witnessing a <a href="https://www.nytimes.com/2019/02/20/opinion/africa-national-parks.html">renaissance of biodiversity</a>, with <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212864">populations of elephants, hippos and other mammals actually increasing</a>. Gorongosa shows us that with long-term planning and collaboration with local populations it is not too late to allow degraded ecosystems to recover and that – if given the opportunity – nature has an astonishing capacity for resilience. </p>
<p>Understanding the current biodiversity crisis from the perspective of deep time may help guide our efforts to <a href="http://science.sciencemag.org/content/355/6325/eaah4787">conserve and restore the ecosystems</a> we <a href="https://www.theguardian.com/environment/2018/nov/03/stop-biodiversity-loss-or-we-could-face-our-own-extinction-warns-un">need for our own survival</a>. Modern species of elephants, hippopotamuses, giraffes and rhinoceroses are survivors from the deep past. Elephantids appeared in the fossil record of eastern Africa at about the same time as the first hominins and probably helped to shape the landscapes where our hominin ancestors thrived. It is paradoxical that the single surviving hominin species is now driving modern-day megaherbivores, along with many other forms of life, to extinction. We do so at our peril.</p><img src="https://counter.theconversation.com/content/107727/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>René Bobe receives funding from the National Geographic Society. </span></em></p><p class="fine-print"><em><span>Susana Carvalho receives funding from The National Geographic Society, the Leverhulme Trust, UK & St Hugh's College, Oxford. </span></em></p>Long-standing assumption that humans killed large mammals 4.5m years ago has been debunked by researchers – but some experts still think humans played a part in the demise of biodiversityRené Bobe, Research Associate, University of OxfordSusana Carvalho, Associate Professor in Palaeoanthropology, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1126722019-03-29T14:56:28Z2019-03-29T14:56:28ZLast of the giants: What killed off Madagascar’s megafauna a thousand years ago?<figure><img src="https://images.theconversation.com/files/265740/original/file-20190325-36264-n5hk55.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A modern mouse lemur *Microcebus* sits upon the cranium of an extinct *Megaladapis* lemur.</span> <span class="attribution"><a class="source" href="https://www.daovanhoang.com">Dao Van Hoang www.daovanhoang.com</a></span></figcaption></figure><p>Giant 10-foot-tall elephant birds, with eggs eight times larger than an ostrich’s. Sloth lemurs bigger than a panda, weighing in at 350 pounds. A puma-like predator called the giant fosa.</p>
<p>They sound like characters in a child’s fantasy book, but along with dozens of other species, they once really roamed the landscape of Madagascar. Then, after millions of years of evolution in the middle of the Indian Ocean, the populations crashed in just a couple of centuries.</p>
<p>Scientists know that over the past 40,000 years, most of Earth’s megafauna – that is, animals human-size or larger – have gone extinct. Woolly mammoths, sabre tooth tigers and countless others no longer roam the planet.</p>
<p>What’s remarkable about the megafaunal crash in Madagascar is that it occurred not tens of thousands of years ago but just over 1,000 years ago, between A.D. 700 and 1000. And while some small populations survived a while longer, the damage was done in a relatively short amount of time. Why?</p>
<p>Over the last three years, new investigations into climate and land use patterns, human genetic diversity on the island and the dating of hundreds of fossils have fundamentally changed scientists’ understanding of the human and natural history of Madagascar. <a href="https://scholar.google.com/citations?user=M6TfcNkAAAAJ&hl=en&oi=ao">As two</a> <a href="https://scholar.google.com/citations?user=DUkXIeAAAAAJ&hl=en&oi=ao">paleoclimatologists and</a> <a href="https://scholar.google.com/citations?user=wAfh3EYAAAAJ&hl=en&oi=ao">a paleontologist</a>, we brought together this research with new evidence of megafaunal butchery. In doing so we’ve created <a href="https://doi.org/10.1016/j.jhevol.2019.03.002">a new theory</a> of how, why and when these Malagasy megafauna went extinct.</p>
<h2>Climate at the time of the crash</h2>
<p>The first job is to understand exactly when the megafauna died out.</p>
<p>Radiocarbon dating of <a href="https://doi.org/10.1111/ecog.02376">over 400 recent fossils</a> demonstrates that animals under 22 pounds lived on Madagascar throughout the last 10,000 years. For animals over 22 pounds, there are abundant fossils up to 1,000 years ago, but relatively few since. The biggest decline in number of large animals occurred rapidly between A.D. 700 and 1000 – practically instantaneous given the long history of their existence on the island. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=805&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=805&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=805&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1011&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1011&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265741/original/file-20190326-36267-10yh2bt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1011&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Malagasy graduate student and team member Peterson Faina with stalagmites in a cave in Madagascar.</span>
<span class="attribution"><span class="source">Laurie Godfrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>What was the climate doing at that time? One popular theory for the megafaunal extinction has blamed <a href="https://doi.org/10.1111/j.1365-2699.2009.02203.x">island-wide drying</a>. To test this idea, our team has been exploring the caves of Madagascar, collecting and analyzing stalagmites. As stalagmites grow upwards from the cave floor, layer by layer, differences in the chemistry of each layer document changes in the climate outside the cave.</p>
<p>By analyzing chemical composition and comparing ratios of various isotopes in these stalagmites, we created new <a href="https://doi.org/10.1016/j.quascirev.2017.03.017">high-resolution records of changes in the Malagasy ecosystems and climate</a>. We found minor fluctuations in the strength of the summer rains throughout the last 2,000 years, but no significant drying over that period. In fact, A.D. 780-960 was one of the wettest periods of the last 2,000 years. <a href="https://doi.org/10.1111/ecog.02376">Chemical analyses of fossils</a> back up this claim.</p>
<p>So it looks like there was no significant drying around the time the megafauna disappeared.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265742/original/file-20190326-36279-1j4dim6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many of the forests that originally existed on Madagascar are now replaced by more open, human-modified landscapes, like this palm savanna at Anjohibe.</span>
<span class="attribution"><span class="source">Laurie Godfrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Instead, the <a href="https://doi.org/10.1016/j.quascirev.2016.01.007">stalagmite records</a> indicated a rapid and dramatic change in the landscape. Changing ratios of the isotopes carbon-12 to carbon-13 reveal a switch from forests to grassland right around A.D. 900, the same time as the megafaunal population crash. Clearly something big happened around this time.</p>
<h2>Cut marks and evidence of butchery</h2>
<p>With no significant change in the climate, some point to the <a href="https://doi.org/10.1073/pnas.1534700100">arrival of humans</a> on the island as a possible cause of the megafauna population crash. It seems logical that once people arrived on Madagascar, they might have hunted the big animals into extinction. New data suggest that this timing doesn’t add up, though.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=736&fit=crop&dpr=1 600w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=736&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=736&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=924&fit=crop&dpr=1 754w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=924&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/265925/original/file-20190326-36264-1gtfa8j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=924&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of two chop marks on the head of a femur of an extinct lemur, Pachylemur. This individual’s hind limb was removed from the trunk at the hip joint, probably with a machete.</span>
<span class="attribution"><span class="source">Lindsay Meador</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><a href="https://doi.org/10.1126/sciadv.aat6925">According to new dates on fossil bones</a> with cut marks on them, humans arrived on Madagascar 10,500 years ago, much earlier than previously believed. But whoever these early people were, there’s no genetic evidence of them left on the island. <a href="https://doi.org/10.1073/pnas.1704906114">New analysis of the human genetic diversity</a> in modern Madagascar suggests the current population derives primarily from two waves of migration: first from Indonesia 3,000 to 2,000 years ago, and later from mainland Africa 1,500 years ago.</p>
<p>So it seems that people lived alongside the megafauna for thousands of years. How did the humans interact with the large animals?</p>
<p>Our new study found dozens of fossils with butchery marks. Cut and chop marks provide compelling evidence as to which species people were hunting and eating. Evidence of butchery of animals that are now extinct continues right up to the time of the megafaunal crash. Some people on Madagascar hunted and ate the megafauna for millennia without a population crash.</p>
<h2>Evidence for a change in land use</h2>
<p>If there was no obvious climate shift and humans lived alongside and sustainably hunted the megafauna for up to 9,000 years, what could have triggered the population crash?</p>
<p>The abrupt land use change might hold some clues. The transition from a forest-dominated ecosystem to a grassland-dominated ecosystem appears to be widespread. Scientists have identified this switch not only in the chemical signature of stalagmites but also in pollen grains buried in layers of <a href="https://doi.org/10.1016/0033-5894(87)90038-X">mud at the bottom of lakes</a>. Ancient lake sediments reveal two other changes occurred at the same time as the shift to grass species: an increase in charcoal from fires and an increase in the fungus <em>Sporormiella</em>, which is associated with the dung of large herbivores <a href="https://doi.org/10.1073/pnas.1534700100">such as cows</a>.</p>
<p>Evidence for simultaneous increases in grassland, fires, and cows and other domesticated animals points to a sudden change in Malagasy lifestyle: the introduction of cattle husbandry and slash-and-burn agriculture known locally as <a href="https://www.madamagazine.com/en/english-tavy-kahlschlag-einer-insel/">Tavy</a>. Here, forests are cut down to make space for rice paddies, and grassland burned to promote the growth of nutritious seedlings for cow fodder.</p>
<p>This move away from foraging and hunting toward farming meant the land could support more people. The result was a rapid rise in the size of the human population – and that’s what we conclude spelled disaster for the megafauna.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/266562/original/file-20190329-70982-kfun1k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some Malagasy farmers plow agricultural fields in the traditional way.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/malagasy-farmers-plowing-agricultural-field-traditional-266475566">Damian Ryszawy/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Here lies the contradiction of the situation: Hunting megafauna for survival became less important as people could rely on their agriculture and livestock. But cut marks on fossil bones indicate that hunting didn’t altogether stop just because people had other food sources. It turns out that the impact on the megafauna of larger human populations hunting just to supplement their diet was greater than the impact of smaller human populations relying more heavily on the native animals as a vital food source.</p>
<p>Bringing together new data on land use changes, climatic histories, genetics, fossil ages and butchery of the megafauna, we call this change “<a href="https://doi.org/10.1016/j.jhevol.2019.03.002">the subsistence shift hypothesis</a>.” Both the habitat loss and increase in human population arose out of a fundamental change in the way humans lived on Madagascar, from a more nomadic hunter-gatherer lifestyle to an agrarian society. We argue that it was this reorganization on Madagascar around A.D. 700-1000 that led to the crash in the megafaunal population.</p>
<p>Small populations of megafauna lived on in isolated pockets for another few centuries, but their fate was likely already sealed. The majority of the giant birds and animals that were once common across our planet have gone extinct. Many of the remaining giants, such as elephants and rhinos, are threatened or endangered. Will they go the same way as the Malagasy megafauna, casualties of humans’ changing lifestyles?</p><img src="https://counter.theconversation.com/content/112672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nick Scroxton receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Laurie Godfrey receives funding from the National Science Foundation BCS 1750598. </span></em></p><p class="fine-print"><em><span>Stephen Burns receives funding from the US National Science Foundation (grant AGS‐1702891/1702691).</span></em></p>A series of new studies sheds light on the population crash and extinction of the giant birds, lemurs and more that roamed the island until around A.D. 700-1000.Nick Scroxton, Postdoctoral Research Scholar in Paleoclimatology, UMass AmherstLaurie Godfrey, Emeritus Professor of Anthropology, UMass AmherstStephen Burns, Professor of Geosciences, UMass AmherstLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/953442018-04-26T07:59:36Z2018-04-26T07:59:36ZHow to hunt a giant sloth – according to ancient human footprints<figure><img src="https://images.theconversation.com/files/215943/original/file-20180423-133859-v905gz.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">: Alex McClelland, Bournemouth University</span></span></figcaption></figure><p>Rearing on its hind legs, the giant ground sloth would have been a formidable prey for anyone, let alone humans without modern weapons. Tightly muscled, angry and swinging its fore legs tipped with wolverine-like claws, it would have been able to defend itself effectively. Our ancestors used misdirection to gain the upper hand in close-quarter combat with this deadly creature.</p>
<p>What is perhaps even more remarkable is that we can read this story from the 10,000-year-old footprints that these combatants left behind, as revealed by our new research published in <a href="http://advances.sciencemag.org/content/4/4/eaar7621">Science Advances</a>. Numerous large animals such as the giant ground sloth – so-called megafauna – became extinct at the end of the Ice Age. We don’t know if hunting was the cause but the new footprint evidence tells us how human hunters tackled such fearsome animals and clearly shows that they did. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=228&fit=crop&dpr=1 600w, https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=228&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=228&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=286&fit=crop&dpr=1 754w, https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=286&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/215934/original/file-20180423-133853-1wkazfx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=286&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">White Sands National Monument.</span>
<span class="attribution"><span class="source">Matthew Bennett, Bournemouth University</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These footprints were found at <a href="https://www.nps.gov/whsa/index.htm">White Sands National Monument</a> in New Mexico, US, on part of the monument that used by the military. The <a href="http://www.wsmr.army.mil/Pages/home.aspx">White Sands Missile Range</a>, located close to the Trinity nuclear site, is famous as the birth place of the US space programme, of Ronald Reagan’s <a href="https://www.theguardian.com/us-news/2017/aug/18/president-reagan-star-wars-nuclear-weapons-testing-1986">Star Wars initiative</a> and of countless missile tests. It is now a place where long-range rather than close-quarter combat is fine-tuned.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/215935/original/file-20180423-133856-184pa4m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tracking the footprints.</span>
<span class="attribution"><span class="source">Matthew Bennett, Bournemouth University</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It is a beautiful place, home to a huge salt playa (dry lake) known as Alkali Flat and the world’s largest gypsum dune field, made famous by <a href="https://www.nps.gov/whsa/planyourvisit/upload/filming_history_11_18_11.pdf">numerous films</a> including Transformers and the Book of Eli. At the height of the Ice Age it was home to a large lake (palaeo Lake Otero).</p>
<p>As the climate warmed, the lake shrank and its bed was eroded by the wind to create the dunes and leave salt flats that periodically pooled water. The Ice Age megafauna left tracks on these flats, as did the humans that hunted them. The tracks are remarkable in that they are only a few centimetres beneath the surface and yet have been preserved for over 10,000 years. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=268&fit=crop&dpr=1 600w, https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=268&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=268&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=337&fit=crop&dpr=1 754w, https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=337&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/215937/original/file-20180423-133853-1f6iepf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=337&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Footprint comparison.</span>
<span class="attribution"><span class="source">David Bustos, National Park Service</span></span>
</figcaption>
</figure>
<p>Here there are tracks of extinct giant ground sloth, of mastodon, mammoth, camel and dire wolf. These tracks are colloquially known as “ghost tracks” as they are only visible at the surface during specific weather conditions, when the salt crusts are not too thick and the ground not too wet. Careful excavation is possible in the right conditions and reveals some amazing features.</p>
<p>Perhaps the coolest of these is a series of human tracks that we found within the sloth prints. In our paper, produced with a <a href="http://advances.sciencemag.org/content/4/4/eaar7621">large number of colleagues</a>, we suggest that the humans stepped into the sloth prints as they stalked them for the kill. We have also identified large “flailing circles” that record the sloth rising up on its hind legs and swinging its fore legs, presumably in a defensive, sweeping motion to keep the hunters at bay. As it overbalanced, it put its knuckles and claws down to steady itself.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=488&fit=crop&dpr=1 600w, https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=488&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=488&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=613&fit=crop&dpr=1 754w, https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=613&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/215939/original/file-20180423-133876-oeq5vs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=613&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Plaster cast footprints.</span>
<span class="attribution"><span class="source">David Bustos, National Park Service</span></span>
</figcaption>
</figure>
<p>These circles are always accompanied by human tracks. Over a wide area, we see that where there are no human tracks, the sloth walk in straight lines. Where human track are present, the sloth trackways show sudden changes in direction suggesting the sloth was trying to evade its hunters.</p>
<p>Piecing together the puzzle, we can see how sloth were kept on the flat playa by a horde of people who left tracks along the its edge. The animals was then distracted by one stalking hunter, while another crept forward and tried to strike the killing blow. It is a story of life and death, written in mud.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=482&fit=crop&dpr=1 600w, https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=482&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=482&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=605&fit=crop&dpr=1 754w, https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=605&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/215938/original/file-20180423-133862-prnqqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=605&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Matthew Bennett, dusting for prints.</span>
<span class="attribution"><span class="source">David Bustos, National Park Service</span></span>
</figcaption>
</figure>
<p>What would convince our ancestors to engage is such a deadly game? Surely the bigger the prey, the greater the risk? Maybe it was because a big kill could fill many stomachs without waste, or maybe it was pure human bravado.</p>
<p>At this time at the end of the last Ice Age, the Americas were being colonised by humans spreading out over the prairie plains. It was also a time of animal extinctions. Many palaeontologists <a href="https://doi.org/10.1073/pnas.1504020112">favour the argument</a> that human over-hunting drove this wave of extinction and for some it has become an emblem of early human impact on the environment. <a href="https://www.newscientist.com/article/dn27952-megafauna-extinction-dna-evidence-pins-blame-on-climate-change">Others argue</a> that climate change was the true cause and our species is innocent. </p>
<p>It is a giant crime scene in which footprints now play a part. Our data confirms that human hunters were attacking megafauna and were practiced at it. Unfortunately, it doesn’t cast light on the impact of that hunting. Whether humans were the ultimate or immediate cause of the extinction is still not clear. There are many variables including rapid environmental change to be considered. But what is clear from tracks at White Sands is that humans were then, as now, “apex predators” at the top of the food chain.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fkY5aWNomUs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/95344/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Robert Bennett receives funding from the UK Natural Environment Research Council. </span></em></p><p class="fine-print"><em><span>Katie Thompson and Sally Christine Reynolds 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>How we discovered ancient footprints of early human hunters and their megafauna prey.Matthew Robert Bennett, Professor of Environmental and Geographical Sciences, Bournemouth UniversityKatie Thompson, Research Associate, Bournemouth UniversitySally Christine Reynolds, Senior Lecturer in Hominin Palaeoecology, Bournemouth UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/889812017-12-12T16:11:51Z2017-12-12T16:11:51ZGiant penguin find: remains suggest huge bird was taller than a human<figure><img src="https://images.theconversation.com/files/198583/original/file-20171211-27686-1icv19e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Present day Emperor penguins like this would have been dwarfed by the giant find.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Scientists <a href="https://theconversation.com/new-zealand-discovery-of-fossilised-monster-bird-bones-reveals-a-colossal-ancient-penguin-89028">have discovered</a> a now-extinct species of giant penguin that was taller than most humans. The remains of the bird, perhaps the tallest penguin species ever discovered, help show how quickly giant penguins developed after the extinction of the dinosaurs around 66m years ago.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=913&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=913&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=913&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1147&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1147&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198590/original/file-20171211-27693-1ih0d1b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1147&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bone comparison.</span>
<span class="attribution"><span class="source">G. Mayr/Senckenberg Research Institute</span></span>
</figcaption>
</figure>
<p>The animal revealed by fossil fragments found in New Zealand was around 1.77m tall and weighed around 101kg. It would have dwarfed the largest penguin alive today, the emperor penguin, which measures <a href="https://www.beautyofbirds.com/penguins.html">1.1m in height and 35kg in weight</a>.</p>
<p>The skeletal remains from a single penguin included parts of the breastbone, shoulders, wings, legs and spine. Its notable features included an unusually thick sternal keel (part of the breast attached to the wings) and an unusually long femur (thigh bone).</p>
<p>These were enough to demonstrate the bird was not only a unique species but also a previously unknown genus (group of species). The species has been named <em>Kumimanu biceae</em>, from the Maori words “kumi”, referring to a large mythical monster, and “manu” meaning bird.</p>
<p>Living penguins all share a set of adaptations such as flipper-like wings, short and smooth feathers that trap air to aid buoyancy, and countershading (a black back and white front) to help avoid predators and increase their own hunting ability through camouflage. While we cannot be certain, it is likely that early penguins such as <em>K. biceae</em> possessed at least some of these adaptations.</p>
<h2>Penguin origins</h2>
<p>There are currently between 17 and 20 species of penguins alive today, depending on the exact classification used, but there have been more species since the group first evolved some time after the dinosaurs went extinct. The earliest species of extinct penguin discovered so far is <a href="https://academic.oup.com/mbe/article/23/6/1144/1055321"><em>Waimanu manneringi</em></a>, which lived in New Zealand around 62m years ago. Although this species more closely resembled modern diver birds (or loons), it was already adapted for life in the water and couldn’t fly. Three of the <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1096-0031.2006.00116.x/abstract;jsessionid=FB81C4E1D36C1CC4144522BE8F3C7903.f03t02">earliest penguin fossils</a> we have originated from southern New Zealand and Byrd Land, Antarctica, suggesting the birds first appeared in the southern hemisphere. </p>
<p>We previously thought that giant penguins took much longer to evolve. For instance, <a href="http://www.polish.polar.pan.pl/ppr23/ppr23-005.pdf"><em>Anthropornis nordenskjoeldi</em> and <em>Pachydyptes ponderosus</em> </a> were for a long time considered to be the largest-ever penguins and lived during the Eocene epoch 56m to 34m years ago. But the discovery of <em>K. biceae</em> suggests this size shift among penguins first occurred much earlier, shortly after the group became flightless during the Paleocene epoch, some 66m to 56m years ago. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=633&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=633&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=633&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=795&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=795&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198585/original/file-20171211-27698-14djc3c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=795&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Who are you calling giant?</span>
<span class="attribution"><span class="source">G. Mayr/Senckenberg Research Institute</span></span>
</figcaption>
</figure>
<p>This followed the mass extinction that wiped an estimated 75% of life on Earth, including the dinosaurs. It is possible that the animals that survived the extinction were able to thrive and develop because their competitors and predators had disappeared. Many of these species evolved to become much larger, a tendency known as <a href="http://palaeo.gly.bris.ac.uk/benton/reprints/2002Copesrule.html">“Cope’s Rule”</a>. Bigger animals are usually better at hunting, attracting a mate, retaining heat and can even be more intelligent.</p>
<p>In the case of penguins, the large reptile predators that dominated the seas during the time of the dinosaurs were wiped out, leaving space for <em>K. biceae</em> and other early penguins to thrive. Once established, they probably grew increasingly large, following Cope’s Rule.</p>
<p>But they would have inevitably faced growing competition from other developing species. As large predatory toothed whales and seals evolved and succeeded, groups such as giant penguins would have no longer been able to compete and ultimately died out, leaving behind only the smaller species of penguins we recognise today.</p><img src="https://counter.theconversation.com/content/88981/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ben Garrod 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>Scientists in New Zealand have discovered an extinct penguin known as Kumimanu biceae that was 1.77m tall.Ben Garrod, Fellow, Animal and Environmental Biology, Anglia Ruskin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/889472017-12-11T19:13:38Z2017-12-11T19:13:38ZTasmanian tigers were going extinct before we pushed them over the edge<figure><img src="https://images.theconversation.com/files/198462/original/file-20171211-27686-lrmoci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Gone since 1936, and ailing since long before that.</span> <span class="attribution"><span class="source">Tasmanian Museum and Art Gallery</span>, <span class="license">Author provided</span></span></figcaption></figure><p>There’s no doubt that humans killed off the <a href="https://australianmuseum.net.au/the-thylacine">Tasmanian tiger</a>. But a new genetic analysis suggests this species had been on the decline for millennia before humans arrived to drive them to extinction.</p>
<p>The Tasmanian tiger, also known as the thylacine, was unique. It was the largest marsupial predator that survived into recent times. Sadly it was hunted to extinction in the wild, and the last known Tasmanian tiger died in captivity in 1936.</p>
<p>In a <a href="http://nature.com/articles/doi:10.1038/s41559-017-0417-y">paper published in Nature Ecology and Evolution today</a>, my colleagues and I piece together its entire genetic sequence for the first time. It tells us that thylacines’ genetic health had been declining for many millennia before they first encountered human hunters.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/will-we-hunt-dingoes-to-the-brink-like-the-tasmanian-tiger-19982">Will we hunt dingoes to the brink like the Tasmanian tiger?</a>
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<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=738&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=738&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=738&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=927&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=927&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198466/original/file-20171211-27693-1jgss5o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=927&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hounded by hunters.</span>
<span class="attribution"><span class="source">Tasmanian Museum and Art Gallery</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our research also offered the chance to study the origins of the similarity in body shape between the thylacine and dogs. The two are almost identical, despite having last shared a common ancestor more than 160 million years ago – a remarkable example of so-called “convergent evolution”. </p>
<p>Decoding the thylacine genome allowed us to ask the question: if two animals develop an identical body shape, do they also show identical changes in their DNA?</p>
<h2>Thylacine secrets</h2>
<p>These questions were previously difficult to answer. The age and storage conditions of existing specimens meant that most thylacine specimens have DNA that is highly fragmented into very short segments, which are not suitable for piecing together the entire genome.</p>
<p>We identified a 109-year-old specimen of a young pouch thylacine in the Museums Victoria collection, which had much more intact DNA than other specimens. This gave us enough pieces to put together the entire jigsaw of its genetic makeup.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=747&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=747&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=747&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=939&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=939&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198463/original/file-20171211-27708-kte384.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=939&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 preserved young, thylacine with enough DNA to reveal its whole genome.</span>
<span class="attribution"><span class="source">Museums Victoria</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Next, we made a detailed comparison of thylacines and dogs to see just how similar they really are. We used digital imaging to compare the thylacine’s skull shape to many other mammals, and found that the thylacine was indeed very similar to various types of dog (especially the wolf and red fox), and quite different from its closest living marsupial relatives such as the numbat, Tasmanian devil, and kangaroos. </p>
<p>Our results confirmed that thylacines and dogs really are the best example of convergent evolution between two distantly related mammal species ever described.</p>
<p>We next asked whether this similarity in body form is reflected by similarity in the genes. To do this, we compared the DNA sequences of thylacine genes with those of dogs and other animals too. </p>
<p>While we found many similarities between thylacines’ and dogs’ genes, they were not significantly more similar than the same genes from other animals with different body shapes, such as Tasmanian devils and cows.</p>
<p>We therefore concluded that whatever the reason why thylacines and dogs’ skulls are so similarly shaped, it is not because evolution is driving their gene sequences to be the same. </p>
<h2>Family ties</h2>
<p>The thylacine genome also allowed us to deduce its precise position in the marsupial family tree, which has been a controversial topic.</p>
<p>Our analyses showed that the thylacine was at the root of a group called the Dasyuromorphia, which also includes the <a href="http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=294">numbat</a> and <a href="http://www.parks.tas.gov.au/?base=387">Tasmanian devil</a>. </p>
<p>By examining the amount of diversity present in the single thylacine genome, we were able to estimate its effective population size during past millennia. This demographic analysis revealed extremely low genetic diversity, suggesting that if we hadn’t hunted them into extinction the population would be in very poor genetic health, just like today’s Tasmanian devils.</p>
<p>The less diversity you have in your genome, the more susceptible you are to disease, which might be why devils have contracted the facial tumour virus, and certainly why it has been so easily spread. The thylacine would have been at a similar risk of contracting devastating diseases.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198465/original/file-20171211-27698-1sg40zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&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 last thylacine alive.</span>
<span class="attribution"><span class="source">Tasmanian Museum and Art Gallery</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This loss in population diversity was previously thought to have occurred as a population of thylacines (and devils) became isolated on Tasmania some 15,000 years ago, when the land bridge closed between it and the mainland. </p>
<p>But our analysis suggests that the process actually began much earlier – between 70,000 and 120,000 years ago. This suggests that both the devil and thylacine populations already had very poor genetic health long before the land bridge closed.</p>
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Read more:
<a href="https://theconversation.com/how-curiosity-can-save-species-from-extinction-52006">How curiosity can save species from extinction</a>
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</em>
</p>
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<p>Now that we know the whole genome of the Tasmanian tiger, we know much more about this extinct animal and the unique place it held in Australia’s marsupial family tree. We are expanding our analyses of the genome to determine how it came to look so similar to the dog, and to continue to learn more about the genetics of this unique marsupial apex predator.</p><img src="https://counter.theconversation.com/content/88947/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Pask receives funding from Australian Research Council (ARC), National Health and Medical Research Council (NHMRC), The University of Melbourne. </span></em></p>The new Tasmanian tiger genome reveals some fascinating facts about this extinct marsupial, including why they were so similar to dogs, and how they were growing more vulnerable to genetic disease.Andrew Pask, Associate Professor, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/847622017-09-27T05:22:35Z2017-09-27T05:22:35ZGiant marsupials once migrated across an Australian Ice Age landscape<figure><img src="https://images.theconversation.com/files/187676/original/file-20170926-17414-ewqc10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An impression of what it could have looked like: a giant lizard, Megalania, stalks a herd of migrating Diprotodon, while a pair of massive megafaunal kangaroos look on.</span> <span class="attribution"><a class="source" href="https://theconversation.com/giant-marsupials-once-migrated-across-an-australian-ice-age-landscape-84762">Laurie Beirne</a></span></figcaption></figure><p>Australia was once home to a giant prehistoric Ice Age marsupial related to wombats and koalas, and that followed an annual seasonal migration.</p>
<p>The three-tonne beast, up to 1.8 metres tall and 3.5 metres long, was the only known marsupial to follow a migration pattern, according to our research <a href="http://rspb.royalsocietypublishing.org/content/284/1863/20170785">published</a> in the journal Proceedings of the Royal Society of London B.</p>
<p>For many years, palaeontologists have marvelled at the fossil deposits of southeast Queensland’s Darling Downs, describing it as a “<a href="http://trove.nla.gov.au/newspaper/article/20342790?searchTerm=a%20complete%20skeleton%20of%20a%20diprotodon">vast graveyard</a>” of the enormous herbivorous and carnivorous animals of the <a href="https://australianmuseum.net.au/the-pleistocene-epoch">Pleistocene</a> (from about 1.6 million to 10,000 years ago).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/187680/original/file-20170926-19342-1tgnxwe.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>
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<span class="caption">An excerpt from an article published in The Queenslander in 1893 by Archibald Meston eloquently describing the fossil deposits of the Darling Downs.</span>
<span class="attribution"><a class="source" href="http://trove.nla.gov.au/newspaper/article/20342790?searchTerm=a%20complete%20skeleton%20of%20a%20diprotodon">Gilbert Price/The Queenslander</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These giant, now extinct animals are commonly dubbed the <a href="http://www.qm.qld.gov.au/Find+out+about/Dinosaurs+and+Ancient+Life+of+Queensland/Megafauna#.WcruEFV96Uk">megafauna</a> and comprised a suite of oversized marsupials, reptiles and birds.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tall-turkeys-and-nuggety-chickens-large-megapode-birds-once-lived-across-australia-79111">Tall turkeys and nuggety chickens: large 'megapode' birds once lived across Australia</a>
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<p>The diversity of the Darling Downs’ Ice Age wildlife was incredible and included some heavy-hitting record breakers such as Megalania (<a href="https://www.uq.edu.au/news/article/2015/09/giant-killer-lizard-fossil-shines-new-light-early-australians"><em>Varanus priscus</em></a>), the biggest venomous lizard ever to exist, the Marsupial “Lion” (<a href="https://australianmuseum.net.au/thylacoleo-carnifex"><em>Thylacoleo carnifex</em></a>), the largest known pouched predator, and the ruler of the Pleistocene, the 3,000kg wombat-like Diprotodon (<a href="https://australianmuseum.net.au/diprotodon-optatum"><em>Diprotodon optatum</em></a>), famous for being the bulkiest marsupial ever to walk the planet.</p>
<p>But what was life like on the Darling Downs during the Ice Age? Our new study focused on reconstructing the palaeobiology and palaeoecology of Diprotodon in an effort to reveal the secrets of “Australia’s Serengeti”.</p>
<h2>A giant among giants</h2>
<p>Diprotodon is one of the first Australian animals described on the basis of fossils, but very little is actually known about it. Its fossil record tells us that it was the most widespread species of megafauna and also one of the last surviving.</p>
<p>Our study concentrated on Diprotodon’s teeth. These can reveal a remarkable amount of information about extinct animals such as their diet and relationships to other species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/187701/original/file-20170927-10403-m9o42g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Drilling a Diprotodon incisor tooth for the study.</span>
<span class="attribution"><span class="source">Gilbert Price</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We selected an upper incisor and drilled numerous samples from the tough, crystalline outer enamel for a geochemical study. (You can see it in 3D detail <a href="https://sketchfab.com/models/2cbeeb704fff41edb560c4179876b218">here</a>.)</p>
<p>The old saying “<a href="http://www.phrases.org.uk/meanings/you-are-what-you-eat.html">you are what you eat</a>” is absolutely true, for the chemical signature of the foods that an organism eats becomes fixed into its teeth when they form.</p>
<p>But it’s also true that “you are where you ate”, especially if you are a plant eater. The geochemistry of the soils where plants grow also becomes incorporated into a herbivore’s teeth. If that particular geochemical signal varies within a given tooth, it would imply that the individual fed across different geological regions when alive.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=283&fit=crop&dpr=1 600w, https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=283&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=283&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=355&fit=crop&dpr=1 754w, https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=355&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/187706/original/file-20170927-23677-g258ia.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=355&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 geochemical signature of rocks become fixed into the teeth of herbivores.</span>
<span class="attribution"><span class="source">Gilbert Price/Museums Victoria</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Like elephant tusks, Diprotodon’s front incisors never stopped growing throughout its life. Thus, our sampling revealed not only seasonal changes in food and water intake of the Diprotodon, but also the various geological provinces where the individual once travelled.</p>
<h2>Migrating megafauna</h2>
<p>Our data clearly show that Diprotodon was a seasonal migrant. It tracked its preferred food source year after year across vast geological regions of the Darling Downs.</p>
<p>It would move roughly north to south and back again, up to 200km per year in massive round-trip journeys, just like many of <a href="https://www.youtube.com/watch?v=HYM6LqDJLiM">East Africa’s mammals</a> do today.</p>
<p>And like those East African cousins, Diprotodon moved in herds or <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2008.00387.x/abstract">mobs</a>.</p>
<p>To date, no other marsupial living or extinct is known to undertake such journeys. This is all the more remarkable considering that Diprotodon’s closest relatives, the metatherians (a mammal group that includes all living marsupials but not placental or egg-laying mammals), have been around for more than 160 million years.</p>
<p>Our data suggest that such migration is an ecological phenomenon that has been extinct in Australia since the Pleistocene. Not only does this have implications for understanding what happened to the megafauna, but there may be many other lessons we can learn from this finding.</p>
<h2>A natural experiment</h2>
<p>The potential collapse of modern ecosystems containing migrating organisms worries ecologists and conservationists the world over, particularly in terms of knock-on effects.</p>
<p>For instance, relatively large-bodied herbivores such as zebra and wildebeest are keystone migrating herbivores of the Serengeti, dramatically influencing and changing environments for other organisms across vast areas.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/187705/original/file-20170927-23618-1oftuah.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Migrating zebra are keystone migrating herbivores of the Serengeti.</span>
<span class="attribution"><span class="source">Gilbert Price</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>What would happen if these animals went extinct and the migratory corridors of the Serengeti broke down? Would it lead to widespread ecosystem collapse and further species loss?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/aboriginal-australians-co-existed-with-the-megafauna-for-at-least-17-000-years-70589">Aboriginal Australians co-existed with the megafauna for at least 17,000 years</a>
</strong>
</em>
</p>
<hr>
<p>Our new finding suggests that Australia could serve as a natural experiment for understanding what might happen. The fossil record provides the before, while the current ecosystem provides the after.</p>
<p>But more research into this area is critically needed. The fossil record between the Ice Age and today remains incredibly patchy. We just don’t know the consequences of the collapse of these prehistoric ecosystems.</p>
<p>Filling in the gaps, further understanding which other Australian megafauna were migrants, what happened to them in terms of extinction, and the knock-on effects, will be fundamental in yielding conservation lessons for our planet.</p><img src="https://counter.theconversation.com/content/84762/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gilbert Price receives funding from the Australian Research Council and Ian Potter Foundation. </span></em></p>Studies of the fossil teeth of the three-tonne Diprotodon have revealed the now-extinct beast was Australia’s only known seasonally migrating marsupial.Gilbert Price, Lecturer in Palaeontology, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/763072017-04-18T19:49:59Z2017-04-18T19:49:59ZHow English-style drizzle killed the Ice Age’s giants<figure><img src="https://images.theconversation.com/files/165551/original/image-20170418-32703-1mh52ri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Giant sloths: killed by rainy weather?</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3AWLA_hmns_Giant_ground_sloth_2.jpg">Kamraman/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Wet weather at the end of the last ice age appears to have helped drive the ecosystems of large grazing animals, such as mammoths and giant sloths, extinct across vast swathes of Eurasia and the Americas, according to our new research.</p>
<p>The study, <a href="http://nature.com/articles/doi:10.1038/s41559-017-0125">published in Nature Ecology and Evolution today</a>, shows that landscapes in many regions became suddenly wetter between 11,000 and 15,000 years ago, turning grasslands into peat bogs and forest, and ushering in the demise of many megafaunal species.</p>
<p>By examining the bone chemistry of megafauna fossils from Eurasia, North America and South America over the time leading up to the extinction, we found that all three continents experienced the same dramatic increase in moisture. This would have rapidly altered the grassland ecosystems that once covered a third of the globe.</p>
<p>The period after the world thawed from the most recent ice age is already very well studied, thanks largely to the tonnes of animal bones preserved in permafrost. The period is a goldmine for researchers – literally, given that many fossils were first found during gold prospecting operations.</p>
<p>Our work at the <a href="https://www.adelaide.edu.au/acad/">Australian Centre for Ancient DNA</a> usually concerns genetic material from long-dead organisms. As a result, we have accrued a vast collection of bones from around the world during this period. </p>
<p>But we made our latest discovery by shifting our attention away from DNA and towards the nitrogen atoms preserved the fossils’ bone collagen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165559/original/image-20170418-32726-dsbdox.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lead Author Tim Rabanus-Wallace hunts for megafaunal fossils in the Canadian permafrost in 2015.</span>
<span class="attribution"><span class="source">Julien Soubrier</span></span>
</figcaption>
</figure>
<h2>Chemical signatures</h2>
<p>Nitrogen has two stable isotopes (atoms with the same number of protons but differing number of neutrons), called nitrogen-14 and nitrogen-15. Changes in environmental conditions can alter the ratio of these two isotopes in the soil. That, in turn, is reflected in the tissues of growing plants, and ultimately in the bones of the animals that eat those plants. In arid conditions, processes like evaporation preferentially remove the lighter nitrogen-14 from the soil. This contributes to a useful correlation seen in many grassland mammals: less nitrogen-14 in the bones means more moisture in the environment.</p>
<p>We studied 511 accurately dated bones, from species including bison, horses and llamas, and found that a pronounced spike in moisture occurred between 11,000 and 15,000 years ago, affecting grasslands in Europe, Siberia, North America, and South America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165557/original/image-20170418-32705-ya7s1z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Alan Cooper inspects ice age bones from the Yukon Palaeontology Program’s collection, Canada, 2015.</span>
<span class="attribution"><span class="source">Julien Soubrier</span></span>
</figcaption>
</figure>
<p>At the time of this moisture spike, dramatic changes were occurring on the landscapes. Giant, continent-sized ice sheets were collapsing and retreating, leaving lakes and rivers in their wake. Sea levels were rising, and altered wind and water currents were bringing rains to once-dry continental interiors. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=581&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=581&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=581&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=730&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=730&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165562/original/image-20170418-32713-qqnmxv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=730&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The study shows that a peak in moisture occurred between the time of the ice sheets melting, and the invasion of new vegetation types such as peatlands (data shown from Canada and northern United States).</span>
<span class="attribution"><span class="source">http://nature.com/articles/doi:10.1038/s41559-017-0125</span></span>
</figcaption>
</figure>
<p>As a result, forests and peatlands were forming where grass, which specialises in dry environments, once dominated. Grasses are also specially adapted to tolerate grazing – in fact, they depend upon grazers to distribute nutrients and clear dead litter from the ground each season. Forest plants, on the other hand, produce toxic compounds specifically to deter herbivores. For decades, researchers have <a href="http://www.pnas.org/content/112/46/14301.full">discussed the idea</a> that the invading forests drove the grassland communities into collapse. </p>
<p>Our new study provides the crime scene’s smoking gun. Not only was moisture affecting the grassland mammals during the forest invasion and the subsequent extinctions, but this was happening right around the globe.</p>
<h2>Extinction rethink</h2>
<p>This discovery prompts a rethink on some of the key mysteries in the extinction event, such as the curious case of Africa. Many of Africa’s megafauna — elephants, wildebeest, hippopotamus, and so on — escaped the extinction events, and unlike their counterparts on other continents have survived to this day. </p>
<p>It has been argued that this is because African megafauna <a href="http://www.tandfonline.com.proxy.library.adelaide.edu.au/doi/abs/10.1080/03115510408619286">evolved alongside humans</a>, and were naturally wary of human hunters. However, this argument cannot explain the pronounced phase of extinctions in Europe. Neanderthals have existed there for at least 200,000 years, while anatomically modern humans arrive around 43,000 years ago. </p>
<p>We suggest instead that the moisture-driven extinction hypothesis provides a much better explanation. Africa’s position astride the Equator means that its central forested monsoon belt has always been surrounded by continuous stretches of grassland, which graded into the deserts of the north and south. It was the persistence of these grasslands that allowed the local megafauna to survive relatively intact.</p>
<p>Our study may also offers insights into the question of how the current climate change might affect today’s ecosystems. </p>
<p>Understanding how climate changes affected ecosystems in the past is imperative to making informed predictions about how climate changes may influence ecosystems in the future. The consequences of human-induced global warming are often depicted using images of droughts and famines. But our discovery is a reminder that all rapid environmental changes — wet as well as dry — can cause dramatic changes in biological communities and ecosystems.</p>
<p>In this case, warming expressed itself not through parched drought but through centuries of persistent English drizzle, with rain, slush and grey skies. It seems like a rather unpleasant way to go.</p><img src="https://counter.theconversation.com/content/76307/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Cooper receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Matthew Wooller receives funding from US National Science Foundation</span></em></p><p class="fine-print"><em><span>Tim Rabanus-Wallace 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>A burst of wet weather could have helped to kill off mammoths and other large herbivores, by transforming much of the world’s grasslands into bogs and forests and depriving megafauna of food.Alan Cooper, Director, Australian Centre for Ancient DNA, University of AdelaideMatthew Wooller, Professor, University of Alaska FairbanksTim Rabanus-Wallace, PhD candidate, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/705892017-01-11T19:56:51Z2017-01-11T19:56:51ZAboriginal Australians co-existed with the megafauna for at least 17,000 years<figure><img src="https://images.theconversation.com/files/150865/original/image-20161220-26718-7zxlut.jpg?ixlib=rb-1.1.0&rect=0%2C625%2C3368%2C2399&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What it could have looked like when humans and megafauna lived together: a giant macropod _Procoptodon goliah_ in the foreground, while _Thylacinus cynocephalus_ hunts for prey nearby. A herd of _Zygomaturus_ can be see on the lake edge of the ancient Willandra system.</span> <span class="attribution"><span class="source">Illustration by Laurie Beirne </span>, <span class="license">Author provided</span></span></figcaption></figure><p>Australia was once home to giant reptiles, marsupials and birds (and some not so giant), but the extinction of this megafauna has been the subject of a debate that has persisted since the 19th century. </p>
<p>Despite great advances in the available scientific techniques for investigating the problem, answering the key question of how they became extinct has remained elusive. </p>
<p>Indeed, the same questions as those asked in the 19th century by scientists, such as the British comparative anatomist <a href="https://www.britannica.com/biography/Richard-Owen">Sir Richard Owen</a> and the Prussian scientist and explorer <a href="https://www.britannica.com/biography/Ludwig-Leichhardt">Ludwig Leichhardt</a>, remain: were people responsible for their demise or was it climate change?</p>
<p>Our new research, published in the latest <a href="http://www.sciencedirect.com/science/article/pii/S0277379116306011">Quaternary Science Reviews</a> journal, shows that early humans to Australian lived alongside some of the megafauna for many thousands of years before the animals became extinct. </p>
<h2>The First Australians</h2>
<p>Many researchers have previously argued that the megafauna became extinct soon after the arrival of the First Australians.</p>
<p>For example, it has been argued that perhaps <a href="https://www.theguardian.com/world/1999/jan/08/timradford">firing</a> of the landscape dramatically altered ancient Australia’s ecology. One species in particular, the giant flightless bird <a href="http://australianmuseum.net.au/genyornis-newtoni"><em>Genyornis newtoni</em></a> was investigated and shown to have succumbed to significant habitat change and direct <a href="http://www.abc.net.au/news/2016-01-30/genyornis-giant-bird-extinction-mystery-points-to-first-people/7126882">predation</a>.</p>
<p>But the hypothesis for <em>Genyornis</em>‘ extinction has come under significant criticism due to the emergence of counter evidence. Firstly the egg shells thought to be from <em>Genyornis</em> are considered by leading palaeontologists to perhaps be from a much smaller <a href="https://theconversation.com/a-case-of-mistaken-identity-for-australias-extinct-big-bird-52856">megapode</a>.</p>
<p>The evidence for firing of the landscape, as studied through the genomes of fire sensitive plants, shows no record of plants going through genetic bottlenecks as a result of significant <a href="https://theconversation.com/did-fire-kill-off-australias-megafauna-19679">firing events</a>.</p>
<p>It seems that Aboriginal populations may not have been that large until much later in prehistory. Our genomic research has revealed that significant demographic changes did not occur until some <a href="https://theconversation.com/dna-reveals-a-new-history-of-the-first-australians-65344">10,000 years ago</a>. The genomic evidence suggests that for tens of thousands of years, Aboriginal populations were not that large. </p>
<p>More careful analysis of the record often reveals a very different picture.</p>
<h2>A dating game</h2>
<p>Critical to understanding when the megafauna became extinct is dating, and ideally, the application of multiple dating techniques will provide the finest resolution. If two different dating techniques arrive at similar dates, then this is a very good sign for the age of a species.</p>
<p>In recent years it has been suggested there are very few good dates for the extinction of megafauna. Some have argued that it is possible many of the 45 or so megafauna species thought to have become extinct after 50,000 years ago may have in fact slipped into the extinction abyss tens of thousands of years <a href="http://newsroom.unsw.edu.au/news/science/climate-change-not-human-activity-led-megafauna-extinction">before</a> the First Australians arrived. </p>
<p>One way of testing the various extinction models is by looking for megafauna in landscapes that show continuous Aboriginal occupation over the past 50,000 years. These landscapes should ideally also have conditions for the preservation of fossil bones.</p>
<p>There are very few localities like this but one exception in Australia is the <a href="https://www.environment.gov.au/heritage/places/world/willandra">Willandra Lakes</a> World Heritage Area, in New South Wales.</p>
<p>If we can show that megafauna disappear soon after the arrival of the First Australians, then we have support for the rapid extinction model. If we show that megafauna and people co-existed for many years, then we may have to seek other explanations for their demise. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=252&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=252&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=252&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=317&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=317&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150682/original/image-20161219-24289-nge7q5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=317&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Searching for megafauna fossils in the Willandra Lakes World Heritage Area.</span>
<span class="attribution"><span class="source">Michael Westaway</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In theory this sounds quite straightforward, but unfortunately it is far from the case. While there are megafauna fossils found across the Willandra landscape, many of these have eroded out of their original burial contexts.</p>
<p>We can get age estimates on these fossils using uranium series (U-series) dating, but they only represent minimum age estimates. If we can find fossils still encased within their original sediments, then we can date the age of the sand grains using a technique called optically stimulated <a href="http://archaeology.about.com/od/lterms/g/luminescence.htm">luminescence dating</a> (OSL for short).</p>
<p>By dating the fossil directly with U-series we arrive at a minimum age estimate. By dating the sand grains that a fossil is found in we arrive at the maximum age range. </p>
<p>Unfortunately carbon dating does not work within the Willandra for megafauna fossils as there never seems to be enough collagen left in the bone to obtain a carbon date. </p>
<h2>A groundbreaking fossil find – in the museum</h2>
<p>After much field work spread over a number of years we had very little luck in finding <em>in situ</em> fossils. We found numerous specimens, but these were often isolated bones sitting on eroded surfaces.</p>
<p>But one specimen found a few decades before our search did provide an excellent dating opportunity.</p>
<p><em>Zygomaturus trilobus</em> was a large lumbering wombat-like marsupial, the size of a very large bull. We know very little about its ecology, and we know even less about when and how it became extinct. </p>
<p>A specimen of this extraordinary marsupial with its large flaring cheek bones (zygomatics) was excavated on two separate occasions in the 1980s, first by zoologist Jeanette Hope and later by archaeologists Harvey Johnston and Peter Clarke.</p>
<p>The upper jaw (maxilla) of the animal was sent to the Australian Museum in Sydney where it was kept encased in its original sediments. The lower jaw can be seen on display at <a href="http://www.nationalparks.nsw.gov.au/visit-a-park/parks/Mungo-National-Park">Mungo National Park</a>. </p>
<h2>Climate the catalyst for extinction?</h2>
<p>By taking sediment samples for OSL dating and by dating the fossil directly with U-series dating we were able to show that the specimen died sometime around 33,000 years ago.</p>
<p>Aboriginal people arrived in the Willandra <a href="http://www.nature.com/nature/journal/v421/n6925/abs/nature01383.html">some 50,000 years ago</a>. It is always possible that earlier evidence for the First Australians in that landscape will be found in the future. </p>
<p>The <em>Zygomaturus</em> specimen shows that people and megafauna co-existed for at least 17,000 years. Indeed the species seems to have existed up to the period where the climate began to change dramatically, known as the last glacial cycle leading up to the <a href="http://archaeology.about.com/od/lterms/g/last_glacial_ma.htm">Last Glacial Maximum</a>.</p>
<p>Of course our date at 33,000 years ago does not represent the extinction date of <em>Zygomaturus</em>, just the latest dated remains of this iconic species.</p>
<p>Perhaps deteriorating climatic condition saw the Willandra Lakes become a refuge for both megafauna and people, as the surrounding plains held less water. This may have brought species such as <em>Zygomaturus</em> and people into increased contact? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150690/original/image-20161219-24296-1dg0h2k.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">A representation of <em>Zygomaturus</em> with real-life but small <em>Homo sapiens</em>, Mungo National Park.</span>
<span class="attribution"><span class="source">Jane McDonald</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This single fossil has changed the nature of the megafauna extinction debate. We can now abandon the rapid/over kill hypothesis and start to untangle how climate may have played a role, or how changes in Aboriginal population numbers may have impacted on the ecology of the megafauna?</p>
<p>We should start to build an understanding of how these animals played a role in the ecology of ancient Australia. Were they, for example, critical in the management of certain habitats, just as the megafauna of Africa are today?</p>
<p>We know next to nothing of the ecology of most of these species. </p>
<p>It is possible that some species of megafauna co-existed for even longer so much work remains to be done. There is still a great deal to learn about Australia’s ancient megafauna.</p><img src="https://counter.theconversation.com/content/70589/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Westaway receives funding from the Australian Research Council. This research was supported by the Three Tribal Groups of the Willandra Lakes World Heritage Area and staff of Mungo National Park and the Willandra Lakes World Heritage Area.</span></em></p><p class="fine-print"><em><span>Rainer Grun receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Jon Olley 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 extinction of the giant reptiles, marsupials and birds that once called Australia home has been the subject of much debate, including the role early Australians may have had on their fate.Michael Westaway, Senior Research Fellow, Research Centre for Human Evolution, Griffith UniversityJon Olley, Professor of Water Science, Griffith UniversityRainer Grun, Professor of Archaeogeochemistry, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/538212016-01-29T12:04:46Z2016-01-29T12:04:46ZNew analysis finds no evidence that climate wiped out Australia’s megafauna<figure><img src="https://images.theconversation.com/files/109465/original/image-20160128-1064-1ogz79l.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Diprotodon, the largest ever marsupial, probably died out at human hands.</span> <span class="attribution"><span class="source">Peter Murray (courtesy of Chris Johnson)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>During the period from 60,000 to 800 years ago, the world lost most of its big animals, or “megafauna”. The cause of this mass extinction is controversial, nowhere more so than in Australia. </p>
<p>Australia’s megafauna consisted of an amazing variety of bizarre creatures including giant <a href="https://en.wikipedia.org/wiki/Protemnodon">wallabies and kangaroos</a>; great wombat-like beasts such as <a href="http://www.prehistoric-wildlife.com/species/d/diprotodon.html"><em>Diprotodon</em></a>, <a href="http://museumvictoria.com.au/melbournemuseum/discoverycentre/600-million-years/timeline/quaternary/zygomaturus/"><em>Zygomaturus</em></a> and <a href="http://museumvictoria.com.au/melbournemuseum/discoverycentre/600-million-years/timeline/quaternary/palorchestes/"><em>Palorchestes</em></a>; and <a href="http://museumvictoria.com.au/melbournemuseum/discoverycentre/dinosaur-walk/meet-the-skeletons/genyornis/">colossal birds</a> and reptiles.</p>
<p>Did we lose these animals because of <a href="https://theconversation.com/climate-change-wiped-out-australias-megafauna-13966">drastic climate changes</a>? Or was it <a href="https://theconversation.com/hunting-or-climate-change-megafauna-extinction-debate-narrows-10602">overhunting by ancient Aboriginal people</a>, or indirect effects of people changing the vegetation with fire? Or perhaps some combination of these?</p>
<p>Our <a href="http://dx.doi.org/10.1038/ncomms10511">new study</a>, featuring the most accurate dates ever compiled for these extinctions, finds that most species went extinct just a few millennia after humans first appeared in Australia, meaning that the arrival of humans was the decisive event in the megafauna’s demise.</p>
<h2>Finding the cause</h2>
<p>To decide between the possible causes of climate change or human impact we need to compare the timing of extinction with human arrival and climate change. The graphic below shows three possible scenarios that could arise once the dates of these events have been established reliably.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=504&fit=crop&dpr=1 600w, https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=504&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=504&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=633&fit=crop&dpr=1 754w, https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=633&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/109457/original/image-20160128-26788-5ec7pz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=633&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Three possible scenarios: the megafauna could have died out soon after humans arrived in Australia, or long afterwards, or before. Note that the time axis runs from right to left.</span>
<span class="attribution"><span class="source">Frédérik Saltré</span></span>
</figcaption>
</figure>
<p>In the first scenario, most animal extinctions occur soon after humans arrive. If there is no evidence for any large changes in climate at or immediately before this time, we might therefore conclude that humans were responsible.</p>
<p>In the second case, the animals go extinct after a period of coexistence with humans. The longer the coexistence, the more likely that other drivers like climate change could have contributed to the animals’ demise. Alternatively, the slow pace of the eventual extinction could reflect gradual growth of human populations to sizes at which they begin to have impacts. Again, the key is whether the climate changed remarkably during this interval of coexistence.</p>
<p>The final possibility is that the extinctions preceded the arrival of humans, who therefore had nothing to do with it. If the climate changed noticeably when the animals went extinct, we can be confident that climate change was the main cause.</p>
<p>This seems straightforward, but the problem is getting good data to reconstruct these timelines. Dating techniques often give us highly uncertain (or even dodgy) estimates of the ages of fossils and other ancient material. And because of poor preservation in Australia’s harsh climate, we have fewer fossils than in other parts of the world.</p>
<h2>Building a reliable timeline</h2>
<p>In our study, <a href="http://dx.doi.org/10.1038/ncomms10511">published in Nature Communications</a>, we and our colleagues reconstructed the first reliable extinction timelines for 16 megafauna groups in Australia. We then matched these dates against the timing of humans’ arrival in Australia, and against six different measures of prehistoric climate.</p>
<p>Our first challenge was the variable quality of fossil dates. Some published dates are either too uncertain to be useful, or are based on questionable or outdated techniques. We previously developed <a href="http://www.sciencedirect.com/science/article/pii/S1871101415300534">a system to assess the reliability of fossil dates</a>, and we applied this to all published dates on Australia’s megafauna.</p>
<p>The next problem was using the fossil dates to work out when species went extinct. Unfortunately, the youngest fossil almost never indicates the true timing of extinction. Fossilisation is so rare that it’s practically impossible that the last individual of a species will wind up as a fossil. Extinction could be many thousands of years later than the date of the youngest fossil.</p>
<p><a href="http://conservationbytes.com/2015/06/02/an-appeal-to-extinction-chronologists/">Several mathematical techniques</a> can estimate the window of true extinction from a series of dates. We used these methods to infer extinction timing for those megafauna with enough reliable dates for analysis. We also used the same methods to estimate the time of human arrival from archaeological dates.</p>
<p>Last, we aligned these timelines with several climate measures going back to 120,000 years ago – temperature and precipitation variations, ice core data indicating relative temperature, El Niño intensity, and the speed at which a species would need to migrate to track the shifting climate conditions. We then checked to see whether large changes in these climate measures happened around the same time as any of the extinction events. </p>
<p>The result was remarkably clear. We found a peak of extinctions around 42,000 years ago – around 13,000 years after the arrival of humans. There was no correlation between extinction and any of the climate indicators (whether or not we allowed for time lags between climate changes and extinction). </p>
<p>This suggests that if climate did have a role, it was only minor or localised and cannot explain the broad pattern of extinctions over the whole continent.</p>
<p>Extinctions began when humans first arrived, but the peak in extinctions came 13,000 years later. This is an intriguing delay. On one hand, it clearly allows plenty of time for people to have become widespread and affect the continental ecosystem; on the other, it suggests that human impacts emerged only gradually. This may show that human populations in Australia grew very slowly at first, as suggested by other analyses of the <a href="https://theconversation.com/australias-colonisation-was-no-accident-say-the-numbers-13730">archaeological record</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/109491/original/image-20160128-3052-1ceezyn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Distribution of extinction times for all megafauna genera (in blue) and appearance time of first human (in red) estimated by a set of mathematical techniques. The gap between the two highest peaks represents the period of human–megafauna overlap. Note the time axis runs from right to left.</span>
<span class="attribution"><span class="source">Frédérik Saltré</span></span>
</figcaption>
</figure>
<h2>Is it that simple?</h2>
<p>So it looks like humans did it, but we should note that our findings apply at the scale of the entire continent of Australia. Although our data are the best currently available, they do not rule out effects of climate on extinctions on a smaller regional scale. We still have a lot to learn about the details of the disappearance of our megafauna.</p><img src="https://counter.theconversation.com/content/53821/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frédérik Saltré receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Christopher Johnson receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Corey Bradshaw receives funding from the Australian Research Council. </span></em></p>What killed off Australia’s giant wombats and other megafauna? New dating once again points the finger at human hunters, rather than abrupt changes to the climate.Frédérik Saltré, Research Associate in Ecology, University of AdelaideChristopher Johnson, Professor of Wildlife Conservation and ARC Australian Professorial Fellow, University of TasmaniaCorey J. A. Bradshaw, Sir Hubert Wilkins Chair of Climate Change, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.