tag:theconversation.com,2011:/es/topics/quaternary-extinction-event-71441/articlesQuaternary extinction event – The Conversation2020-04-29T15:48:10Ztag: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>
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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>
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<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>
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<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">
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<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>
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<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>
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<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">
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<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>
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<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>
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Read more:
<a href="https://theconversation.com/could-resurrecting-mammoths-help-stop-arctic-emissions-95956">Could resurrecting mammoths help stop Arctic emissions?</a>
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<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>
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<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">
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<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>
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<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>
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<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">
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<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>
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<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>
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<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">
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<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>
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<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>
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<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">
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<span class="caption">Rye, one of the first crops.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
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<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/1172342019-05-29T21:03:12Z2019-05-29T21:03:12ZWhy giant human-sized beavers died out 10,000 years ago<figure><img src="https://images.theconversation.com/files/276420/original/file-20190524-187165-x3te7f.jpg?ixlib=rb-1.1.0&rect=17%2C20%2C1979%2C1077&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The now-extinct giant beaver once lived from Florida to Alaska. It weighed as much as 100 kilograms, roughly the same as a small black bear.</span> <span class="attribution"><span class="source">Illustrated by Luke Dickey/Western University</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Giant beavers the size of black bears once roamed the lakes and wetlands of North America. Fortunately for cottage-goers, these mega-rodents died out at the end of the last ice age. </p>
<p>Now extinct, the giant beaver was once a highly successful species. Scientists have found its <a href="https://www.researchgate.net/profile/Richard_Hulbert/publication/268035498_Taxonomy_of_the_Pleistocene_giant_beaver_Castoroides_Rodentia_Castoridae_from_the_southeastern_United_States/links/545fd7b50cf27487b450ab66/Taxonomy-of-the-Pleistocene-giant-beaver-Castoroides-Rodentia-Castoridae-from-the-southeastern-United-States.pdf">fossil remains at sites from Florida</a> to <a href="http://www.beringia.com/exhibit/ice-age-animals/giant-beaver">Alaska and the Yukon</a>. </p>
<p>A super-sized version of the modern beaver in appearance, the giant beaver tipped the scales at 100 kilograms. But it had two crucial differences. </p>
<p>The giant beaver lacked the iconic paddle-shaped tail we see on today’s modern beavers. Instead it had a long skinny tail like a muskrat. </p>
<p>The teeth also looked different. Modern beaver incisors (front teeth) are sharp and chisel-like; giant beaver incisors were bulkier and curved, and lacked a sharp cutting edge. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276422/original/file-20190524-187182-18co5m1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A side-by-side comparison of the modern beaver, Justin Bieber and the giant beaver, all part of Canada’s history.</span>
<span class="attribution"><span class="source">Illustration by Scott Woods/Western University</span></span>
</figcaption>
</figure>
<p>The species suddenly became extinct 10,000 years ago. The disappearance of the giant beaver coincides with that of many other large-bodied ice age animals, including the iconic woolly mammoth. But until now scientists didn’t know for certain why the giant rodent had died out. </p>
<h2>You are what you eat</h2>
<p>We need to understand how the giant beaver lived in order to explain how and why it died out. For example, did it run out of food? Did it get too cold or too hot for it to survive?</p>
<p>Other studies found the giant beaver thrived when the <a href="https://www.researchgate.net/publication/223266220_Oxygen_isotopic_determination_of_climatic_variation_using_phosphate_from_beaver_bone_tooth_enamel_and_dentine">climate was warmer and wetter</a>. They also noticed that giant beaver fossils were most commonly found in sediments that come from <a href="https://journals.iupui.edu/index.php/ias/article/view/7219">ancient wetlands</a>. But no one knew if the giant beaver behaved like the modern beaver. Did it also cut down trees? Or did it eat something completely different? </p>
<p>From an chemical perspective, you are what you eat! The food an animal consumes contains chemical signatures called <a href="https://www.futurelearn.com/courses/archaeology/0/steps/15267">stable isotopes</a> that are incorporated into body tissues such as bone. </p>
<p>These isotopic signatures remain stable over time, for tens of thousands of years, and provide a window into the past. No other studies have used stable isotopes to figure out the giant beaver’s diet. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=896&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=896&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=896&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1126&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1126&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276421/original/file-20190524-187189-xqw6d0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1126&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Giant beaver skull.</span>
<span class="attribution"><span class="source">Florida Museum of Natural History</span></span>
</figcaption>
</figure>
<p>We studied fossil bones from giant beavers that lived in the Yukon and Ohio between 50,000 and 10,000 years ago. We looked at the stable isotope signatures of the ancient bone tissues. </p>
<p>The isotopic signatures linked to woody plants are different from those associated with aquatic plants. We discovered that the giant beaver was not cutting down and eating trees. Instead, <a href="https://doi.org/10.1038/s41598-019-43710-9">it was eating aquatic plants</a>. </p>
<p>This strongly suggests that the giant beaver was not an “ecosystem engineer” like the modern beaver. It was not cutting down trees for food or building giant lodges and dams across the ice age landscape. </p>
<p>Instead, this diet of aquatic plants made the giant beaver highly dependent on wetland habitat for both food and shelter from predators. It also made it vulnerable to climate change.</p>
<h2>Warm and dry climate</h2>
<p>Towards the end of the last ice age 10,000 years ago, the climate became increasingly warm and dry and wetland habitats began to dry up. Although the <a href="https://doi.org/10.1016/j.quascirev.2011.05.020">modern beavers and the giant beaver co-existed on the landscape for tens of thousands of years</a>, only one species survived. </p>
<p>The ability to build dams and lodges may have given the modern beaver a competitive advantage over the giant beaver. With its sharp teeth, the modern beaver could alter the landscape to create suitable wetland habitat where it needed it. The giant beaver couldn’t. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=295&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=295&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=295&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=371&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=371&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276418/original/file-20190524-187182-ksw3mb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=371&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A giant beaver skeleton.</span>
<span class="attribution"><span class="source">Tessa Plint</span></span>
</figcaption>
</figure>
<p>This all fits into the puzzle that many research groups have been working on for decades: we all want to know what caused the <a href="http://www.nhm.ac.uk/our-science/our-work/origins-evolution-and-futures/extinction-large-mammals-late-quaternary.html">global megafauna extinction event</a> that occurred at the end of the last ice age and why so many species of large-bodied animals — woolly mammoths, mastodons and giant ground sloths — disappeared at roughly the same time. </p>
<p>Current evidence indicates that <a href="https://doi.org/10.1038/s41467-018-07897-1">a combination of climate change and human impact were the driving causes behind these extinctions</a>. </p>
<p>Studying the ecological vulnerabilities of long-extinct animals certainly poses its own unique challenges, but it is important to understand the impact of climate change on all species, past or present.</p><img src="https://counter.theconversation.com/content/117234/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tessa Plint received funding from NSERC, Faculty of Science (The University of Western Ontario), and the Arcangelo Rea Foundation. </span></em></p>Scientists studied the fossilized bones of giant beavers to understand what they ate and whether the species could keep up with environmental change.Tessa Plint, PhD researcher, Heriot-Watt University, and former graduate student, Western UniversityLicensed as Creative Commons – attribution, no derivatives.