Today, it's undeniable that humanity holds a profound influence over Earth's climate and its biodiversity. However, contrary to modern media sensationalism, this relationship is not a recent revelation but a saga as ancient as time itself. Human impact on our planet's intricate web of life stretches back tens of thousands of years — possibly even since they first sauntered into the picture.<br /><br />Recent <a href="https://www.cambridge.org/core/journals/cambridge-prisms-extinction/article/latequaternary-megafauna-extinctions-patterns-causes-ecological-consequences-and-implications-for-ecosystem-management-in-the-anthropocene/E885D8C5C90424254C1C75A61DE9D087">studies</a> have spotlighted the extinction or rapid decline of large mammals over the past 50,000 years. While <keyword id="19907392" type="General" weightage="20" keywordseo="climate-change" source="keywords">climate change</keyword> was once a convenient scapegoat, it has proven insufficient to explain these phenomena. Instead, mounting evidence implicates human activity as the primary driver.<br /><br />This phenomenon, known as the <keyword id="22261268" type="General" weightage="20" keywordseo="late-Quaternary-megafauna-extinction" source="Orion">late-Quaternary megafauna extinction</keyword>, marks a significant departure from previous extinction events in Earth's history, with distinct characteristics that set it apart. Unlike earlier extinction events that were often localised, the late-Quaternary extinctions were global in scope and severe in impact. They disproportionately affected larger-bodied species, with megaherbivores weighing over 1,000 kg particularly vulnerable. Shockingly, of the 57 known megaherbivore species from this period, only 11 survived beyond 1,000 AD, highlighting the scale of loss.<br /><br /><h2>Tale as old as time<br /></h2>The narrative begins roughly 100,000 years ago, a time when mammoths roamed icy plains, sabre-toothed tigers prowled lush jungles, and giant ground sloths navigated primaeval forests. Despite the formidable odds, <em>Homo sapiens</em>, armed with finely crafted spears, ascended to the top of the food chain. However, their ascent left behind a trail of dwindling populations and silent extinctions.<br /><br />Previous periods of dramatic climate shifts, like ice ages, didn't cause such widespread extinction of large animals. New research highlights key points that point towards human intervention:<br /><br /><ul><li>Timing: Megafauna extinctions coincided with the arrival of modern humans in different regions around the globe.</li><li>Targeted hunting: Evidence from archaeological digs, like traps and spear points, suggests humans actively hunted these large animals. Isotope analysis even reveals that these giants were a major food source for our ancestors.</li><li>Vulnerability of megafauna: Large animals with slow reproduction rates were particularly susceptible to overhunting by humans.</li></ul>Yet, the impact wasn't limited to extinctions. Even species that survived, like elephants, bears, kangaroos, and antelopes, bore lasting scars from humanity's rise. A 2023 study analysing the DNA of 139 surviving megafauna species reveals a troubling decline in their populations over the last 50,000 years.<br /><br />Further, challenging prevailing theories that blame climate change for extinctions, study author Jens-Christian Svenning emphasised that many extinct megafauna inhabited temperate or tropical climates, undermining climate as the sole explanation.<br /><br /><h2>Looking ahead<br /></h2>The loss of so many large animal species has had profound ecological consequences worldwide. These include disruptions to trophic processes, alterations in physical environmental engineering such as landscape modification, and changes in the transport of energy and matter within ecosystems. The repercussions of these extinctions continue to reverberate through modern ecosystems.<br /><br />In response to these ecological shifts, efforts in megafauna-based trophic rewilding have gained traction as a potential strategy for ecosystem restoration under current global change scenarios. By reintroducing large herbivores into landscapes, researchers and conservationists aim to re-establish ecological processes and enhance biodiversity.<br /><br />Furthermore, the interplay between megafauna and human-driven biotic globalisation underscores the complex relationships between species and ecosystems. Domesticated megafauna, such as livestock, present both ecological challenges and opportunities in managing modern landscapes.<br /><br />As debates continue among scholars — whether to blame climate change or human migration — the echoes of history resound clearly. Standing on the brink of a new era where our technological prowess imperils ecosystems and countless species, the story of these giants serves as a stark warning. What remains to be seen is if we heed the lessons from their decline and the enduring impact humanity has etched into the fabric of evolution, or if we will repeat the errors of our ancestors, leaving only silence in our wake?<br />

Over 80% of prehistoric megaherbivores went extinct due to human activity and not climate change: Study

It is readily evident that humanity holds a tight grip on the <keyword id="6359982" type="General" weightage="80" keywordseo="earth" source="Orion">Earth</keyword>'s climate and its diverse species today. But this might also have been true for tens of thousands of years, our species has been disrupting the delicate web of life on this planet, as revealed by recent research.<br /><br />While past studies often attributed the extinction of large mammals to <keyword id="6361617" type="General" weightage="20" keywordseo="climate-change" source="Orion">climate change</keyword>, a new investigation points fingers at humans. Around 100,000 years ago, as mammoths roamed icy plains and sabre-toothed tigers prowled jungles, Homo sapiens, armed with razor-sharp spears, ascended the food chain, leaving a trail of declines and extinctions.<br /><br />Venturing out of <keyword id="12925" type="General" weightage="20" keywordseo="africa" source="Orion">Africa</keyword>, our adaptable ancestors conquered deserts, mountains, and icy taigas. Masterful hunters, they turned Earth, once resonating with roars and stomps, into an unsettling silence. Yet, the impact extended beyond extinction; survivors like elephants and kangaroos have also faced an alarming decline in their populations, as revealed by a recent <keyword id="25384" type="General" weightage="20" keywordseo="dna" source="Orion">DNA</keyword> study of 139 living megafauna.<br /><br />Lead researcher Juraj Bergman underscores the study's significance, relying on DNA sequencing to estimate historical population sizes by analysing genetic mutations. The selected species offer a diverse perspective on population trends, with a focus on neutral genetic areas less influenced by environmental factors.<br /><br />Challenging climate-driven extinction theories, Jens-Christian Svenning notes that most extinct megafauna inhabited temperate or tropical climates, discrediting climate as the sole explanatory model. The ongoing academic debate between climate change and human migration theories echoes through history, marking Earth as a testament to humanity's dominance.<br />

Ancient giant mammals such as mammoths might’ve gone extinct due to human activity, not climate change

<ul class="summary-list"><li>North America used to be crawling with giant mammals, from dire wolves to big cats.</li><li>Horses and camels evolved on the continent while others, like bison, crossed over from Asia.</li></ul><p>Towering 13 feet tall and weighing a hefty 7 tons, the African elephant is the biggest land mammal on Earth. But that wasn't always the case.</p><p>Tens of millions of years ago, shortly after the dinosaurs went extinct, mammals grew to epic proportions, dwarfing the animals we see today.</p><p>"There used to be cow-sized wombats in Australia, and there were armadillos the size of cars in South America," Emily Lindsey, an assistant curator at the La Brea Tar Pits and Museum, told Insider.</p><p>Some evolved on these continents while others crossed the Bering Land Bridge, which once connected Asia and Alaska.</p><div type="image" title="A map in shades of brown and blue showing the Bering Land Bridge connecting Asia and Alaska." height="650" width="1300" msid="105218368" hostid="261" sizebytes="46194"></div><p>North and South America were home to woolly mammoths, mastodons, giant sloths, and much more.</p><h2>Columbian and woolly mammoths</h2><div type="image" title="People gather around the fossilized skeleton of a woolly mammoth at the QUADRAT museum in Germany" height="1500" width="2250" msid="105218370" hostid="261" sizebytes="275752"></div><p><strong>Height: </strong>12 to 13 <a target="_blank" href="https://ucmp.berkeley.edu/mammal/mesaxonia/elephantidae.php"><u>feet tall</u></a> (Columbian mammoths); 9 to 11 feet tall (woolly mammoths)</p><p><strong>Weight: </strong>10 tons (Columbian mammoths); 4 to 6 tons (woolly mammoths)</p><p><strong>When did they go extinct?</strong> 13,000 to 10,000 <a target="_blank" href="https://www.nps.gov/whsa/learn/nature/mammoth.htm"><u>years ago</u></a> (Columbian mammoths); 4,000 years ago (woolly mammoths)</p><p>Two types of <a target="_blank" href="https://www.businessinsider.com/russia-pleistocene-park-mammoths-2016-3">mammoths</a> roamed North America. Both are members of the proboscidean family, which also includes modern elephants, and stem from a species that evolved in Africa 5 million years ago.</p><p>The Columbian mammoth arrived in North America about 1.5 million years ago, traveling over the <a target="_blank" href="https://www.businessinsider.com/eighteen-thousand-year-old-stone-tools-among-oldest-found-us-2023-9">Bering Strait</a>, which once connected Asia and Alaska. They fanned out at least as far south as Mexico, <a target="_blank" href="https://www.tandfonline.com/doi/abs/10.1080/02724634.1997.10010985"><u>possibly all the way</u></a> to Costa Rica.</p><p>In North America, "you only get the woolly mammoths up in the north, starting around the Great Lakes," Lindsey said. They arrived later, roughly 100,000 years ago, and didn't venture as far south.</p><p>One of the woolly mammoth's most distinctive features is its thick fur. The Columbian mammoth was far less shaggy.</p><h2>American mastodons</h2><div type="image" title="People look at the fossilized skeleton of an American Mastodon at the Natural History Museum" height="1500" width="2250" msid="105218373" hostid="261" sizebytes="309920"></div><p><strong>Height:</strong> 8 to 10 feet tall</p><p><strong>Weight:</strong> 4 to 5 tons</p><p><strong>When did they go extinct?</strong> Around 11,000 years ago</p><p>A tad smaller than their woolly mammoth relatives, American mastodons were also more widely spread. Their fossils <a target="_blank" href="https://www.sdnhm.org/exhibitions/fossil-mysteries/fossil-field-guide-a-z/mastodon/"><u>have been found</u></a> all over the continent, from Alaska to central Mexico.</p><p>Some <a target="_blank" href="https://www.businessinsider.com/r-bachelor-party-finds-rare-mastodon-fossil-in-new-mexico-2014-12"><u>mastodon fossils</u></a> show them living in North America as far back as 16 million years ago. The forest dwellers likely fed on trees and shrubs.</p><p>In addition to their smaller stature, mastodons had shorter, straighter <a target="_blank" href="https://www.businessinsider.com/mammoth-tusk-found-ocean-deep-sea-2021-11">tusks than mammoths</a>. But paleontologists mainly distinguish them by their teeth. <a target="_blank" href="https://www.insider.com/boy-found-ancient-mammoth-tooth-grandmas-backyard-2023-5">Mammoth molars</a> are fairly flat. American mastodons have bumpier molars.</p><h2>Camels</h2><div type="image" title="Camelops and Hemiauchenia are shown next to each other in an artist's rendering" height="1500" width="2568" msid="105218377" hostid="261" sizebytes="71476"></div><p><strong>Height:</strong> <a target="_blank" href="https://www.nps.gov/articles/000/the-camels.htm"><u>7 feet tall</u></a></p><p><strong>Weight:</strong> 1,800 pounds</p><p><strong>When did they go extinct? </strong>10,000 years ago</p><p>"We think of camels as this very exotic creature that we associated with very different places, with sand dunes, but <a target="_blank" href="https://www.businessinsider.com/fossil-discovery-california-ancient-elephants-camels-dogs-2021-5">camels actually are native</a> to North America," Lindsey said.</p><p>Its relatives evolved 44 million years ago during the Eocene period. Over time, Camelops made its way to the Canadian Yukon and Mexico, making its home in woodlands, grasslands, and wetlands.</p><p>The Camelops was about a foot taller than modern camels, but it's difficult to tell from their fossils if they had a hump.</p><p>These animals crossed the Bering land bridge into Asia 7 million years ago and gave rise to modern camels. More recently, they arrived in South America via the Isthmus of Panama, another land bridge that formed between North and South America<strong> </strong>3 million years ago.</p><p>Some of Camelops' ancestors went extinct, Lindsey said. Others continued to evolve. "Those are the llamas and guanacos that you see in South America today," she said.</p><h2>Horses</h2><div type="image" title="Several skeletons of ancient horses are lined up in glass cases at the Field Museum in Chicago" height="1500" width="2175" msid="105218378" hostid="261" sizebytes="281496"></div><p><strong>Height:</strong> <a target="_blank" href="https://www.nps.gov/articles/000/ancient-horse.htm"><u>4.5 feet tall</u></a> (Equus scotti)</p><p><strong>Weight:</strong> 1,100 pounds (Equus scotti)</p><p><strong>When did they go extinct? </strong>About 10,000 years ago</p><p>Over 50 million years ago, horses started evolving in North America. There were many species, all different from today's versions.</p><p>"When they start out, they're very small," Lindsey said, comparable to small dogs. Instead of hooves, they had five toes<strong> </strong>on their feet.</p><p>Then, 15 million years ago, the landscape and climate started changing. It was drier. Grasslands emerged.</p><p>Horses became larger, with longer legs and fewer toes. Some migrated to Eurasia, <a target="_blank" href="https://www.businessinsider.com/ancient-horses-stripes-like-zebras-until-human-domestication-2016-1">becoming zebras</a> and wild Asian horses.</p><p>"Then they get wiped out in the Americas and brought back about 12,000 years later when the Spanish come," Lindsey said.</p><h2>Short-faced bears</h2><div type="image" title="A saber-tooth cat and a short-faced bear roar at each other in an artist's rendering" height="1500" width="2000" msid="105218381" hostid="261" sizebytes="471100"></div><p><strong>Height:</strong> 11 feet tall when standing on their hind legs</p><p><strong>Weight:</strong> 1,500 to 2,200 pounds</p><p><strong>When did they go extinct? </strong>Between 12,7000 and 11,000 years ago</p><p>Hundreds of thousands of years ago, the Arctodus simus cast a looming shadow over boreal forests, plains, tundra, grasslands, and subtropical woodlands. Known as the short-faced bear, it ranged across the US and Canada, into Florida.</p><p>"The short-faced bears were huge," Lindsey said. They were far larger than 8-foot-tall grizzly bears and "would've been terrifying."</p><p>Studies have shown that its muzzle was perhaps not as short as its name suggests. Some researchers <a target="_blank" href="https://iceage.museum.state.il.us/mammals/short-faced-bear-0"><u>also think</u></a> the bear may have been an omnivore instead of solely a meat eater.</p><h2>Dire wolves</h2><div type="image" title="A reconstuction of a dire wolf with another dire wolf in the background at the La Brea Tar Pits and Museum" height="810" width="1440" msid="105218383" hostid="261" sizebytes="90070"></div><p><strong>Height:</strong> 3 feet tall at the shoulder</p><p><strong>Weight:</strong> 130 to 150 pounds</p><p><strong>When did they go extinct?</strong> An estimated 10,000 years ago</p><p>Dire wolves were big. "But they're not as big as they're shown <a target="_blank" href="https://www.insider.com/game-of-thrones-direwolves-original-plans-meaning-cut-2020-10"><u>in 'Game of Thrones</u></a>,' I'm sorry to say," Lindsey said. She calls them the linebacker version of wolves, about 20% larger than gray wolves.</p><p>Once <a target="_blank" href="https://tarpits.org/stories/our-evolving-understanding-dire-wolves"><u>thought to be</u></a> the cousins of gray wolves, dire wolves evolved separately over 5 million years ago in North America. The finding came courtesy of ancient DNA.</p><p>Lindsey said the news was surprising because they're so similar behaviorally and morphologically. For example, they likely lived in packs like modern dogs, wolves, and coyotes.</p><p>Researchers know quite a bit about how dire wolves hunted, too. "Scientists have looked at <a target="_blank" href="https://www.businessinsider.com/dire-wolf-and-sabre-tooth-cat-bones-show-what-prehistoric-hunts-were-like-2017-5"><u>injuries in dire wolves</u></a>, as well as saber-tooth cats, that were found in the tar pits," Lindsey said.</p><p>They found injuries to the fossils' paws and skulls. "That's consistent with the type of injuries we see in, say, wolves today that are chasing down animals on the landscape," Lindsey said. A wolf's prey might trample its toes or kick it in the head.</p><h2>Saber-tooth cats</h2><div type="image" title="A child crouches under a replica of a saber-tooth cat at the National Museum of Scotland in Edinburgh" height="1500" width="2185" msid="105218387" hostid="261" sizebytes="219738"></div><p><strong>Height:</strong> 3 feet at the shoulder (smilodon and scimitar)</p><p><strong>Weight:</strong> 300 to 500 pounds (scimitar cat); up to 750 pounds (smilodon)</p><p><strong>When did they go extinct? </strong>Roughly 10,000 years ago (smilodon); between 10,000 and 28,000 years ago (scimitar)</p><p>You may have grown up calling them saber-toothed tigers, but the smilodon isn't a close relative of tigers. Their common name comes from their impressive canine teeth, which could be up to 7 inches long.</p><p>Another genus of <a target="_blank" href="https://www.businessinsider.com/dire-wolf-and-sabre-tooth-cat-bones-show-what-prehistoric-hunts-were-like-2017-5">saber-tooth cats</a>, Homotherium, is known as scimitar cats. Their teeth weren't as long as smilodon and were serrated like a steak knife. Like the smilodon, they lived in North America during the Pleistocene. The two cats were similarly widespread, from the Yukon to Florida.</p><p>But these two predators had different prey, according to <a target="_blank" href="https://www.cell.com/current-biology/fulltext/S0960-9822(21)00434-6"><u>a study</u></a> from a few years ago. While the smilodon went after tapirs (pig-like animals with trunks)<strong> </strong>and deer, scimitars preferred baby mammoths.</p><p>"Saber-tooth cats tend to get a lot of injuries in their lower back, which is consistent with this idea that they were ambush predators," Lindsey said. The smilodons would sit and wait before leaping onto a large animal and wrestling it to the ground.</p><p>"It's very easy to torque your back that way," Lindsey said. "And so they get a lot of lower back arthritis type of injuries."</p><p>Lindsey was also part of <a target="_blank" href="https://affiliate.insider.com?h=42246614699244699707dd7c242788d80d4a91432fafa7103792e8fe2d509dd0&amp;postID=654c1e6cb0b368bea7429e8a&amp;postSlug=extinct-giant-mammals-pleistocene-megafauna-ice-age-north-america&amp;site=bi&amp;u=https%3A%2F%2Fwww.nature.com%2Farticles%2Fs41598-021-99853-1"><u>a study</u></a> that diagnosed a smilodon with hip dysplasia based on a CT scan of a fossil. "It's an animal that probably couldn't have survived to adulthood as it did without other animals taking care of it," she said. "So that indicates that these are probably social creatures. There's all kinds of amazing, fun things you can learn from bones."</p><h2>Giant sloths</h2><div type="image" title="Visitors look at a large skeleton of a giant ground sloth in a museum in Florida" height="1500" width="2250" msid="105218389" hostid="261" sizebytes="462358"></div><p><strong>Height:</strong> 19.6 feet when upright</p><p><strong>Weight:</strong> Up to 3 tons</p><p><strong>When did they go extinct? </strong>10,000 years ago or into the Late Holocene</p><p>For most extinct Pleistocene megafauna — animals <a target="_blank" href="https://royalsocietypublishing.org/doi/10.1098/rspb.2019.2643"><u>weighing more</u></a> than 100 pounds — there are still living analogs. Instead of mammoths, there are elephants. Camelops has its camel and llama relatives.</p><p>"But you don't have anything in the world that is even kind of like a 3,000-pound sloth," Lindsey said. "That's just something that is completely gone."</p><p>Unlike their modern counterparts, these behemoths spent most of their time on the ground instead of in trees.</p><p>North America had several species of <a target="_blank" href="https://www.businessinsider.com/giant-sloths-hunted-by-humans-bones-2019-3">giant sloths</a>. Among the largest were the Eremotherium, which have mostly been found in the southeast along Florida and the Gulf Coast, as well as in Central and South America.</p><p>"They like sort of the wetter, more tropical regions," Lindsey said. "They got to be about the size of elephants." While very large, the Eremotherium wasn't as big as the Megatherium <strong>— </strong>another species of giant sloth — which lived throughout South America.</p><p>The <a target="_blank" href="https://www.businessinsider.com/fossils-of-giant-sloth-found-in-sinkhole-2019-3">giant sloths</a> had a diverse diet, including being able to reach higher into the trees thanks to their stature and ability to stand on their hind legs. Exactly when they went extinct is disputed, but their adaptability may have helped them survive a bit longer than many other mammals they lived alongside.</p><h2>American lion</h2><div type="image" title="Three lions crouch drinking from a pond in an artist's rendering" height="480" width="960" msid="105218391" hostid="261" sizebytes="46584"></div><p><strong>Height:</strong> 4 feet at the shoulder</p><p><strong>Weight:</strong> Up to 770 pounds</p><p><strong>When did they go extinct? </strong>Between 10,000 and 12,000 years ago</p><p>Saber-tooths weren't the only big cats that made their home in North America. Panthera atrox was one of the largest<strong> </strong>members of the cat family<strong> </strong>ever.</p><p>"The <a target="_blank" href="https://www.businessinsider.com/ancient-american-lion-fossil-found-in-dried-up-mississippi-river-2022-11">American lions</a> were huge," Lindsey said. "They're much, much bigger than modern lions."</p><p>While fairly rare in the fossil record, there's evidence the big cats did make their way throughout North America. Scientists have found their bones and teeth from Canada to Mexico.</p><p>Researchers <a target="_blank" href="https://phys.org/news/2010-05-scientists-american-lion.html"><u>have debated</u></a> about whether these gigantic cats are more closely related to modern lions or jaguars. Its skull shares similarities with lions', but its jaw resembles those of jaguars and tigers.</p><p>Due to its enormous size, the American lion was able to make meals out of bison and wild horses.</p><h2>Ancient bison</h2><div type="image" title="The mummified skull of an extinct bison behind a glass case at the Smithsonian Institution's National Museum of Natural History" height="1500" width="2218" msid="105218393" hostid="261" sizebytes="191042"></div><p><strong>Height:</strong> 7.5 feet tall</p><p><strong>Weight:</strong> 3,500 pounds</p><p><strong>When did they go extinct? </strong>Roughly 10,000 years ago</p><p>Unlike the Camelops and horses that evolved in North America, other big beasts migrated in. That includes ancient bison.</p><p>"They are the most recent arrivals into North America of all the Pleistocene megafauna," Lindsey said.</p><p>The first bison species appeared around 3 million years ago in South Asia and China. Eventually, some crossed the Bering Land Bridge. They start showing up in the North American fossil record between 300,000 and 130,000 years ago.</p><p>The ancient bison, Bison antiquus, was 25% larger than those living today. Their territories included grasslands, woodlands, and wetlands from Canada to Mexico.</p><p>Another species of bison on the continent was the Bison priscus or steppe bison. A <a target="_blank" href="https://www.sciencedirect.com/science/article/abs/pii/S1040618221002421"><u>recent study</u></a> suggested modern bison — Bison biso — evolved from this species.</p><h2>Why did they go extinct?</h2><p>Was it the changing climate, human interactions, or a combination that caused so many large mammals to go extinct around 10,000 years ago?</p><p>"That is something that scientists have been debating for about 70 years," Lindsey said. The climate was changing at the <a target="_blank" href="https://www.businessinsider.com/what-earth-looks-like-during-an-ice-age-2014-5">end of the Ice Age</a> on a global scale. Humans were also spreading throughout the world.</p><p>"These two things are so closely tied in time, the climate changes and the <a target="_blank" href="https://www.businessinsider.com/eighteen-thousand-year-old-stone-tools-among-oldest-found-us-2023-9">spread of human populations</a>, it's been really hard to say to what degree each of those factors was involved in the extinctions," Lindsey said.</p><p>Humans may have more of an impact than just hunting, too. A 2023 paper tied <a target="_blank" href="https://www.businessinsider.com/fires-may-have-caused-la-brea-tar-pit-extinctions-thousands-of-years-ago-2023-8"><u>fires started by humans</u></a> to some of the extinctions in what is now California.</p><p>If that did have an impact on the animals in that region, the causes might vary for others. "Different ecosystems are going to have different parameters of what pushes them to the brink," Lindsey said. "But there is something about the combination of humans and an unstable climate or a rapidly changing environment that pushes ecosystems again and again towards tipping points."</p>

Dire wolves, camels, and other extinct giant mammals that used to live in North America

<ul class="summary-list"><li>The La Brea tar pits captured dire wolves, sabertooth cats, and other megafaunal for millennia.</li><li>Their fossils may show an extinction event 13,000 years ago.</li></ul><p>From about <a href="https://tarpits.org/research-collections/tar-pits-our-research" target="_blank" rel="noopener">50,000 years ago</a>, animals, vegetation, and other debris managed to get stuck in the sticky substance of the Rancho La Brea tar pits in present-day Los Angeles.</p><p>The millions of fossils found in the pits give scientists a time machine into the ancient past and reveal a mysterious mass extinction about 13,000 years ago. </p><p>Species including dire wolves, sabertooth cats, and camels simply vanished from the local archeological record. </p><p>Scientists have various theories about what caused so many megafauna — large animals that weigh at least 97 pounds as adults —  to go extinct at around the same time, from the warming climate to human hunters to disease. </p><p>A <a href="http://www.science.org/doi/10.1126/science.abo3594" target="_blank" rel="noopener">new paper</a> says that, at least in this region of Southern California, human-made fires may be to blame. <strong><br /></strong></p><p>About 13,000 years ago, there was a huge spike in the amount of carbon found in a nearby lake. Fires likely caused the increase, lead author <a href="http://www.science.marshall.edu/okeefef/" target="_blank" rel="noopener">F. Robin O'Keefe</a> said, and humans could've set those fires. </p><p>"Humans have a direct effect in lighting fires, but they also have an indirect effect by killing off the herbivores," O'Keefe said. "And then while all that's happening, it's also getting a lot warmer and a lot drier." </p><h2>Missing dire wolves and constant coyotes </h2><p>There are over 100 pits in Rancho La Brea's 23-acre park, <a href="https://nhm.org/person/dunn-regan" target="_blank" rel="noopener">Regan Dunn</a>, assistant curator at the La Brea Tar Pits and Museum and a co-author on the paper, said.</p><p>The tar is actually naturally occurring asphalt, a low-grade crude oil bubbling up from the oil field below through. Eventually, water or leaves covered the muck. Unwitting animals stopped for a drink or tried to cross, becoming trapped. </p><p>But if too much water flooded a tar pit, it no longer captured animals. So, each pit is its own snapshot of an era, some 50,000 years old, some more recent. "They're kind of these discreet little tornadoes of fossil bone concentrations," Dunn said. </p><div type="image" title="A man in a bright orange vest stands near Lake Pit at the La Brea Tar Pits with a model of a mastodon nearby" height="1500" width="2000" msid="102843345" hostid="261" sizebytes="391200"></div><p>Pit 61/67 is where the majority of the animals in the study came from. Researchers excavated it between 1913 and 1915, finding a trove of fossils. </p><p>The study's radiocarbon dating of the pit's bones showed an interesting trend. "There's lots and lots of megafauna, dire wolves, saber tooth cats, horses, bison, and coyotes," O'Keefe said. "And then suddenly that just stops and it's just coyotes."</p><p>By around 13,000 years ago, they were all gone. The pit had captured not just the animals, but evidence of an extinction event that the researchers think was due to human-made fires. But other experts are skeptical that humans were the cause.</p><p>For this paper, the authors wanted to study anything in the environment that may have contributed to the megafaunal extinction, including temperature, precipitation, vegetation changes, and fire events.</p><p>To get a fuller picture of the megafauna's landscape, they looked at a nearby lake — Lake Elsinore. Elsinore is the name of the castle in "Hamlet," a play where nearly every character dies. There's something poetic about using a lake with the same name in extinction research.</p><p>Around 13,200 years ago, charcoal accumulation rates at Lake Elsinore increased by 30 times earlier amounts. The spike lasted about 300 years. There may have been catastrophic fires or lots of smaller fires, O'Keefe said. During heavy rainfall, runoff thick with charcoal found its way to the lake. </p><p>The paper connects the dots between the elevated levels of carbon, increased fire activity, and humans<em>.</em> But paleontologist <a href="https://www.amnh.org/research/staff-directory/ross-macphee" target="_blank" rel="noopener">Ross MacPhee</a>, who wasn't involved in the study, said there isn't direct proof to make such a claim. "I'm very cautious, very skeptical that the evidence is sufficient in any way to implicate humans," he said.</p><p>But if humans were starting fires in Southern California, there should be examples of that behavior in other areas, too. "If it was a good idea to cook all the meat that you possibly could by starting these fires, then you'd expect to see the same phenomenon repeated" in places like Northern Canada, which had large numbers of megafauna, MacPhee said.</p><p>In addition to the lake's charcoal levels, the researchers used its sedimentary, geochemistry, and pollen data to learn about the region's temperature and precipitation. Based on the pollen and sedimentology records, a severe drought was affecting the area 200 years before the megafauna disappeared, Dunn said. Changing climate also played a role in their dwindling numbers and the severity of the fires.</p><p>Around 14,700 years ago, the woodland began transitioning into shrubland. The leaves that the camels and the giant slots ate disappeared, and then so did those animals. Grass, flowering plants, and shrubs cropped up, all more suitable for horses and other grazing animals than camels.</p><p>The result was a less tree-filled, more open landscape than before. Several studies <a href="https://www.science.org/doi/10.1126/science.1179504" target="_blank" rel="noopener">have shown</a> an <a href="https://www.eurekalert.org/news-releases/987076" target="_blank" rel="noopener">increase in wildfires</a> after <a href="https://www.science.org/doi/10.1126/science.1214261" target="_blank" rel="noopener">megafauna went extinct</a> in certain regions. The loss of herbivores at La Brea could've contributed to a feedback loop, making fires — however, they started — more intense, the paper's authors say<em>.<strong style="background-color: #ffff00;"><br /></strong></em></p><h2><strong style="background-color: #ffffff;">A decades-long debate among the scientific community</strong></h2><p>Since the 1960s, experts have debated the role of humans in wiping out mammoths, mastodons, and other large mammals thousands of years ago.</p><p>A <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.4393" target="_blank" rel="noopener">2018 study</a> found that archaeologists often cite a combination of factors for Pleistocene megafaunal extinctions, while ecologists more often say humans were the tipping point or driving force behind it, a theory known as overkill.</p><p>Paelongotolist MacPhee cautions that there could be other explanations for why these animals in the 61/67 tar pits stopped appearing. "It's entirely reliant on whether you have grounds for believing that these really are first appearances or last appearances, as opposed to just the ones that you were lucky enough to find," he said. </p><p>Whatever was happening in Southern California may not have been occurring elsewhere, either. "You can't use conditions at one site to generalize to the entire continent," MacPhee said. For example, some of the mammals that disappeared from Rancho La Brea, like wild horses, were still found in the Yukon until <a href="https://www.cbc.ca/news/canada/hamilton/mammoths-and-north-american-horses-vanished-later-than-previously-thought-researchers-1.6278399" target="_blank" rel="noopener">about 6,000 years ago</a>.</p><p>This isn't the first time researchers have linked humans' use of fire to an area's megafaunal extinction. A <a href="https://www.jstor.org/stable/4539101" target="_blank" rel="noopener">2005 paper</a> by biologist Guy Robinson and his colleagues found an up-to-10-fold increase in charcoal levels from 12,300-year-old sediments near Orange County, New York. The authors concluded that a combination of fire and changing climate were culpable in the local animals' demises. </p><p>It was a tough sell for some experts at the time. "Indeed, some paleontologists accuse Robinson of reading too much into ancient remnants of charred grass," Sharon Levy <a href="https://global.oup.com/academic/product/once-and-future-giants-9780199931163?cc=us&amp;lang=en&amp;" target="_blank" rel="noopener">wrote</a> in her book "Once and Future Giants: What Ice Age Extinctions Tell Us about the Fate of Earth's Largest Animals."</p><h2><strong>Humans on the move</strong><strong style="background-color: #ffff00;"><em><br /></em></strong></h2><p>Whether there was a sufficient number of people to do substantial damage to the ecosystem is MacPhee's question with any overkill theory. "So far, it's extremely difficult to estimate human density many thousands of years ago, especially in North America," <a href="https://anthropology.uark.edu/directory/?uid=avillase" target="_blank" rel="noopener">Amelia Villaseñor</a>, an assistant professor in the Univesity of Arkansas's anthropology department, said in an email.</p><p>"The human record in Southern California is really terrible," O'Keefe said. The only contemporary fossilized human from the area is the 13,0000-year-old <a href="https://www.nps.gov/chis/learn/historyculture/arlington.htm" target="_blank" rel="noopener">Arlington Springs Man</a>. His co-authors estimate there was a sharp increase in population around 13,200 years ago, enough to have a devastating impact on the ecosystem with the fires they set. </p><div type="image" title="Ashely Farrell pulls a drawer filled with fossils in a long corridor of sample shelves at the paleontological lab at the George C. Page Museum at the La Brea Tar Pits" height="1500" width="1999" msid="102843346" hostid="261" sizebytes="176846"></div><p>While she agrees the loss of camels, horses, and megafauna had an effect on Southern California's environment 13,000 years ago, Villaseñor said she wouldn't draw the same parallels the paper does with fires in the past with those affecting the region today. "The controlled fires set by people [about] 13,000 years ago and even less than 10,000 years ago, at low population densities, are very different than the high density, fire-suppression caused fires of today," she said.</p>

Human-caused fires may have contributed to the extinction of saber-toothed cats, dire wolves, and other animals 13,000 years ago

<p><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/55b955dadd089539028b4706-907-680/5899473679_bc16b154e1_b.jpg" alt="woolly mammoth" data-mce-source="Flickr/Mammut" /><p class="source"><span>Flickr/Mammut</span></p></div><p></p></div></div>Dinosaurs went extinct after a single catastrophic event, when a massive asteroid smashed into Earth off the coast of Mexico.</p><p>But not all extinctions are so clearly defined. As Beth Shapiro explains in her recent book, "<a href="http://www.amazon.com/How-Clone-Mammoth-Science-De-Extinction/dp/0691157057">How to Clone a Mammoth: The Science of De-Extinction</a>," <strong>scientists</strong><strong> still don't agree on exactly how mammoths went extinct just thousands of years ago. </strong></p><p>Humans are getting closer to the point that we might actually be able to resurrect some version of a mammoth - or really, much more likely, modify a modern animal so that it's more like one, as Shapiro explains.</p><p>That ability to somehow reverse a single extinction would be an amazing technological achievement, but with a new <a href="http://www.sciencemag.org/content/345/6195/401">wave of mass extinctions currently transforming</a> the world, there's something disturbing about our inability to settle on an answer to what ended the existence of these large mammals, which thrived until humans spread far and wide across the globe.</p><p>We know because of recent research that <a href="http://www.sciencemag.org/content/early/2015/07/22/science.aac4315">abrupt global warming</a> came at the start of the extinction of mammoths and other ice age megafauna, but scientists have yet to agree on how much of a role man played at the end. "The question remains open," Shapiro writes, "perhaps because we are not particularly comfortable with the answer."</p><p>That answer may be particularly relevant as we look at how humans are affecting and changing the world around us today.</p><h2>The last of the mammoths</h2><p>The last of the woolly mammoths died approximately 3,700 years ago, on Wrangel Island, off the coast of Siberia. This was <a href="http://www.britannica.com/biography/Hammurabi">shortly after the death of Hammurabi</a>, the Babylonian king whose code of laws is remembered as one of the first in history. The <a href="http://www.pbs.org/wgbh/nova/pyramid/explore/gizahistory.html">Great Pyramid of Giza was built</a> almost 1,000 years before. The world had warmed enough that humanity probably arrived on this icy island around the same time.</p><p>But by then, mammoth populations had been on the decline for more than 16,000 years, ever since the peak of the last ice age. Most died about 10,000 years ago - only a few isolated island populations lasted longer.</p><p>As Shapiro writes, we have essentially two main theories about their demise: either it got too warm to support the giants that dominated the Arctic, or our human ancestors hunted them to death.</p><p>Likely, it was some combination of factors.</p><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/55b955dadd089539028b4707-2048-1362/19245285254_afb45680c4_k.jpg" alt="Wrangel island" data-mce-source="NOAA PMEL/Flickr" data-mce-caption="Wrangel Island was home to the last of the mammoths." data-link="https://www.flickr.com/photos/noaa-pmel/19245285254/in/photolist-dYMc6a-dYMc6Z-dYSUks-91HnQa-6qsUXw-njBJTG-vjD7P1-vZ7KJA-vjS4H4-vRRVdt-vjH2wQ-weq3eE-vjS3Rp-esiPow-77MQD4-dYMc5k-dYMc8X-dYMc8e-dKyJ8Y-u8U8qq-uNsGLB-5XjrTv-5XjrSR-76cmPA-aD9wbN" /><p class="source"><span><a href="https://www.flickr.com/photos/noaa-pmel/19245285254/in/photolist-dYMc6a-dYMc6Z-dYSUks-91HnQa-6qsUXw-njBJTG-vjD7P1-vZ7KJA-vjS4H4-vRRVdt-vjH2wQ-weq3eE-vjS3Rp-esiPow-77MQD4-dYMc5k-dYMc8X-dYMc8e-dKyJ8Y-u8U8qq-uNsGLB-5XjrTv-5XjrSR-76cmPA-aD9wbN">NOAA PMEL/Flickr</a></span></p><p class="caption">Wrangel Island was home to the last of the mammoths.</p></div><p></p></div></div></p><p>Shapiro writes that it's hard to pin the mammoth's end on warmth alone. While mammoths were the most abundant large mammals in the North American Arctic for almost 100,000 cold years (with two ice ages), they were around for at least 200,000 years total - including at a time when Earth was as warm or warmer than it is today. The fossil record indicates they were much less dominant during warm spells, with creatures like giant sloths, camels, and giant beaver thriving in the heat.</p><p>It was only at the beginning of the Holocene period, about 12,000 years ago, that many of the large species around the world started to disappear. The world got warmer and at the same time, humans spread to almost every continent - which could mean there's some connection.</p><p>And yet, people lived alongside and hunted mammoths in Asia for thousands of years before the Holocene began. In North America, large mammal populations had begun to decline significantly before humans arrived.</p><h2>"The role of humans will become increasingly clear"</h2><p>Shapiro says that in the case of the mammoth, it was the combination of a warming climate, <a href="http://phys.org/news/2014-02-dna-reveals-clues-mammoths-die.html">changing vegetation</a>, and the emergence of human hunters together that finally caused these creatures to disappear from most of the Earth 10,000 years ago.</p><p>"As we learn more about the timing and pattern of these and other recent extinctions, there is little doubt that the role of humans will become increasingly clear," Shapiro writes. If climate change forced mammoths into smaller and smaller cold territories, growing human populations looking for food quite likely took advantage of those fertile hunting grounds.</p><p>This fits into the latest research on what drove mammoths extinct. A recent <a href="http://www.sciencemag.org/content/early/2015/07/22/science.aac4315">study in the journal Science</a> says that the best evidence is that natural climate change was the initial driver of mammoth extinction, shrinking their food supplies and and forcing the dwindling mammoth populations into whatever cold refuges they could find.</p><p>Humans probably came in at the end of the process, making conditions for mammoths increasingly untenable. "The rise of humans applied the coup de grace to a population that was already under stress," Chris Turney, a paleoclimatologist at Australia's University of New South Wales, <a href="http://www.onearth.org/earthwire/rapid-warming-not-hunters-killed-woolly-mammoth">told onEarth</a>. This time, with humans around, mammoth populations didn't recover.</p><h2>Why an old mystery matters today</h2><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/55b955dadd089539028b4708-3072-2304/2908571159_895bf34ddb_o.jpg" alt="extinct extinction dead animals carcasses skulls voodoo creepy" data-mce-source="Adam Cohn / Flickr" /><p class="source"><span>Adam Cohn / Flickr</span></p></div><p></p></div></div>Back then, humans weren't necessarily powerful or dominant enough to be the main cause of an extinction. Now, we might soon be advanced enough to bring mammoths back - though that's still a controversial and uncertain proposition.</p><p>Whatever the role humans played in the end of the mammoth, Shapiro writes that looking at the disappearance of species in general should make us pause when we look at the ways we transform the environment.</p><p>We need to take care with our power to shape the world and even push the climate in a warmer direction. The ecological consequences of changing the world are unpredictable, and the fact that we still don't quite understand our role in a major extinction - mammoths - should trouble us.</p><p>The woolly mammoth <a href="http://ngm.nationalgeographic.com/2009/05/mammoths/mueller-text">first appeared almost 400,000 years ago</a> and disappeared from most of the world just 10,000 years ago. Humans, who <a href="http://humanorigins.si.edu/evidence/human-fossils/species/homo-sapiens">first evolved 200,000 years ago</a>, have not been on this planet nearly as long as mammoths were, but we are changing the world more than any species ever known.</p><p>Today, scientists estimate that <a href="http://www.businessinsider.com/sixth-extinction-elizabeth-kolbert-2015-4">close to half of Earth's living species</a> could go extinct by the end of this century alone. These include not just large charismatic animals, but also tiny reef invertebrates that might hold a cure for cancer or a way to slow aging. Most creatures cannot be brought back, and their <a href="http://www.businessinsider.com/what-planetary-health-really-means-2015-7">disappearance may have a far greater impact</a> than we think or are willing to admit so far.</p><p>As Shapiro writes, "this future could be one in which so many changes have occurred to the terrestrial and marine ecosystems that we, ourselves, are suddenly vulnerable to extinction."</p>    <div class="margin-top">        <h3>NOW WATCH: <a href="http://www.businessinsider.com/horrible-coffee-side-effects-caffeine-addictive-2015-7">8 horrible things excessive coffee drinking can do to you</a></h3>        <div>            <div>    <script src="http://player.ooyala.com/v3/6e12e8b3387a44daacfb73afba25a76e"></script>    <div class="ooyala-video-player" data-video-autoplay="false" data-video-id="Q1NG8zdjo6GHbeTlUYgKSywxSck1X2MC" data-player-variable="ooyalapopvideo" id="ooyalaplayer_popvideo" style="width:1280px;height:720px"></div>    <script>    if (typeof RunFunctions === 'undefined') { var RunFunctions = []; }     RunFunctions.push(function()    {         var ooyalapopvideo = OO.Player.create('ooyalaplayer_popvideo', 'Q1NG8zdjo6GHbeTlUYgKSywxSck1X2MC',{ autoplay: 'false' });     });    </script>    <noscript><div>Please enable Javascript to watch this video</div></noscript></div>        </div>        <script>(function() { function createPlayer() { OO.ready(function() { RunFunctions.forEach(function(ooyalaFunction) { ooyalaFunction(); }); RunFunctions = [];}); } createPlayer(); }()); </script>    </div>

One of the greatest extinction mysteries in history is still unsolved

<p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/5bc10e3893032c76487e0366-2400/webpnet-resizeimage.jpg" border="0" alt="indri madagascar" data-mce-source="Aarhus University" data-mce-caption="The secretive indri of Madagascar is the largest living lemur. It is also critically endangered and highly evolutionarily distinct with no close relatives, a combination that makes its branch one of most precarious on the mammal evolutionary tree. In the likely event that the indri goes extinct, we will lose 19 million years of unique evolutionary history from the mammal tree of life." /><p class="source"><span>Aarhus University</span></p><p class="caption">The indri of Madagascar - the largest living lemur - is critically endangered and highly evolutionarily distinct. If the indri goes extinct, we will lose 19 million years of unique evolutionary history.</p></div><p></p></div></div></p><ul class="summary-list"><li>The Earth is undergoing a mass extinction, which is caused by human activity that destroys habitats and kills off species.</li><li>In a new study, Danish researchers concluded that so many mammal species will go extinct in the next 50 years that the planet's evolutionary diversity won't recover for at least 3 million years. </li><li>The scientists said their findings could be used to help determine which endangered species are the biggest priorities for conservation efforts.</li></ul><p>Humans will cause so many mammal species to go extinct in the next 50 years that the planet's evolutionary diversity won't recover for 3 to 5 million years, a team of researchers has found.</p><p>The Earth may be entering its sixth mass extinction: an era in which the planet's environments change so much that most animal and plant species die out. The International Union for the Conservation of Nature <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577618/">predicts</a> that 99.9% of critically endangered species and 67% of endangered species will be lost within the next 100 years.</p><p>The five other times a mass extinction has occurred over the past 450 million years, natural disasters were to blame. But now, human activity is killing mammal species.</p><p>In a <a href="http://dx.doi.org/10.1073/pnas.1804906115">study published Monday in the journal PNAS</a>, scientists from Aarhus University in Denmark calculated how fast extinctions are happening, and how long it would take for evolution to bring Earth back to the level of biodiversity it currently has.</p><p>The scientists concluded that in a <span>best-case scenario, nature will need 3-5 million years to get back to the level of biodiversity we have on Earth today. Returning to the state Earth's animal kingdom was in before modern humans evolved would </span>take 5-7 million years.</p><h2>Evolution can't keep up</h2><p>Evolution is the planet's defense mechanism against the loss of biodiversity. As habitats and climates change, species that can't survive die, and new species slowly emerge. But it takes a long time for new species to fill the gaps - and that process is far slower than the rate at which humans are causing mammals to go extinct.</p><p>For their calculations, the Aarhus University researchers used a database containing existing mammal species and mammals that already went extinct as humans spread across the planet. They combined that data with information about extinctions expected to come in the next 50 years, and used advanced simulations of evolution to predict how long recovery would take.</p><p>Their estimates are based on an optimistic assumption that people will eventually stop ruining habitats and causing species to die out, and the extinction rate will go back down. But even in that best-case scenario, the timeline depends on how quickly mammals start recovering. If the extinction rate doesn't start falling for another 20-100 years, more species will likely disappear, causing greater diversity loss, the study said.</p><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/5bc4bf82a4cb621a07162403-1091/182994.jpg" border="0" alt="Litopterns mammal extinction" data-mce-source="Robert Bruce Horsfall via Wikimedia Commons" data-mce-caption="Litopterns, like this one discovered by Charles Darwin, were a strange-looking group of prehistoric South American mammals that were not closely related to any species alive today. When they went extinct at the end of the Ice Age, the mammal Tree of Life lost one of its deepest branches." /><p class="source"><span>Robert Bruce Horsfall via Wikimedia Commons</span></p><p class="caption">Litopterns, like this one discovered by Charles Darwin, were a strange-looking group of prehistoric South American mammals that were not closely related to any species alive today. When they went extinct at the end of the Ice Age, the mammal Tree of Life lost one of its deepest branches.</p></div><p></p></div></div></p><p>The researchers noted that in their model, certain species were given more importance than others. <span>Matt Davis, a paleontologist at Aarhus University who led the study, cited the shrew as an example. </span>There are hundreds of species of shrew, so if one or two go extinct, that would not kill off all shrews on Earth.</p><p>But there were only four species of sabre-toothed tigers on the planet. So when they all went extinct, many years of evolutionary history disappeared with them. </p><p>"Large mammals, or megafauna, such as giant sloths and sabre-toothed tigers, which became extinct about 10,000 years ago, were highly evolutionarily distinct," Davis said in a press release. "Since they had few close relatives, their extinctions meant that entire branches of Earth's evolutionary tree were chopped off."</p><h2>The research could help conservationists  </h2><p>Today, other large animals like the black rhino are facing extinction. Asian elephants' chance of making it to the 22nd century is less than 33%, the study found. These elephants are one of only two remaining species from a group of mammals that once included mastodons and mammoths.</p><p>"We now live in a world that is becoming increasingly impoverished of large wild mammalian species," Jens-Christian Svenning, an Aarhus University professor who researches megafauna, said in the press release. "The few remaining giants, such as rhinos and elephants, are in danger of being wiped out very rapidly."</p><p>He noted that the planet no longer boasts giant beavers, giant deer, or giant armadillos.</p><p>Though the researchers' findings are dire, the scientists said their work could be used to figure out which endangered species are evolutionarily unique, which might help conservationists decide where to focus their efforts to prevent the most devastating extinctions.</p>    <div class="margin-top">        <h3>NOW WATCH: <a href="https://www.businessinsider.com/stem-cell-tech-save-white-rhinos-animals-extinction-endangered-2016-5">Researchers want to try a cutting-edge technique to save rhinos from extinction</a></h3>        <div>            <iframe class="bijwplayerclass" data-player="jwplayer" src="https://content.jwplatform.com/players/SjVFCqk9-CEZHWCBG.html" width="100%" height="100%" frameborder="0" scrolling="auto" style="margin:0px;" allowfullscreen=""></iframe><script>function receiveMessage(event){ console.log(event.data.fullscreen); Android.fullscreen(event.data.fullscreen); }window.addEventListener("message", receiveMessage, false);</script>        </div>    </div>

So many animals will go extinct in the next 50 years that it will take Earth at least 3 million years to recover, a study has found

<p>A world without humans would look a lot more like an African savanna.</p><p>A new <a href="http://biorxiv.org/content/early/2015/04/01/017368">study</a> found that if homo sapiens had never come into existence and spread across the globe, large mammals like giant sloths and ancient horses would roam the Americas, while elephants and rhinos would dominate Northern Europe, as shown in the map below. (The scale depicts the number of large mammal species that would have existed, where red means more species.)</p><p><div class="KonaFilter image-container display-table"><div><div class="image"><img src="https://static-ssl.businessinsider.com/image/55d740eebd86ef19008b4ef3-800-363/world-without-humans.jpg" alt="world without humans" data-mce-source="Soren Faurby" data-link="http://biorxiv.org/content/early/2015/04/01/017368" /><p class="source"><span><a href="http://biorxiv.org/content/early/2015/04/01/017368">Soren Faurby</a></span></p></div><p></p></div></div></p><p>Instead, here's the disturbing reality of what the world's large animal distribution looks like with humans:</p><p><div class="KonaFilter image-container display-table"><div><div class="image"><img src="https://static-ssl.businessinsider.com/image/55d7527d9dd7cc25008b5075-800-363/world-with-humans.jpg" alt="world with humans" data-mce-source="Soren Faurby" data-link="http://biorxiv.org/content/early/2015/04/01/017368" /><p class="source"><span><a href="http://biorxiv.org/content/early/2015/04/01/017368">Soren Faurby</a></span></p></div><p></p></div></div></p><p>The findings show just how big of a role humans have played in the extinction of megafauna around the world, the researchers say.</p><p>"There used to be a remarkably diverse fauna of large mammals in the New World," study co-author Soren Faurby, an evolutionary biologist at Aarhus University in Denmark, told Business Insider.</p><p>But these animals weren't adapted to dealing with anything as cunning as a human hunter, he said. In a previous study that Faurby led, he and his colleagues found the expansion of humans around the world was responsible for the mass extinction of large mammals during the last ice age (about 130,000 years ago) and the period following it, known as the late-Quaternary megafauna extinction.</p><p>Now, they have taken it a step further, and created a model of how these animals would be distributed if humans had never entered the picture.</p><h2>How they did it</h2><p><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/4ef5d7466bb3f70964000017-400-300/steven_strait_in_10,000_b.c._wallpaper_9_800.jpg" alt="caveman" data-mce-source="http://www.10000bcmovie.com/" /><p class="source"><span><a href="http://www.10000bcmovie.com/">www.10000bcmovie.com</a></span></p></div><p></p></div></div>For species that are still alive today, the researchers used historical estimates of animal populations. For extinct species, they estimated the numbers of these animals based on those of other species that were alive at the same time.</p><p>If humans didn't exist, the diversity of animals - especially large mammals - would have been much greater in many parts of the world, the researchers found.</p><p>For example, elephants and their relatives, giant sloths, huge armadillos, horses, and tapirs were once common throughout North America, but most of them disappeared around the time humans first arrived.</p><p>The researchers also looked at how humans impacted the range of things that animals do in their ecosystems. For example, a mouse has a very different role in its environment than an elephant does.</p><p>This range, known as functional diversity, would have been much greater without humans around, but this was true for all land-dwelling animals, not just large mammals (as shown below). The top row shows the functional diversity of large mammals with humans (i) and without us (j); the bottom row shows the diversity of all land animals with (k) and without us (l).<div class="KonaFilter image-container display-table"><div><div class="image"><img src="https://static-ssl.businessinsider.com/image/55d767cbbd86ef13008b5047-1112-391/functional-diversity.png" alt="functional diversity" data-mce-source="Soren Faurby" /><p class="source"><span>Soren Faurby</span></p></div><p></p></div></div></p><p>The landscape might have looked pretty different too. The more large animals you have, the more trees they knock down, resulting in grasslands like the African savanna.</p><p>It's tough to pinpoint the reason for these extinctions. Hunting probably played a big role in the disappearance of herbivores. But many carnivores also went extinct, either because their prey was gone, or because they had to compete with humans for it, Faurby said.</p><p><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/55156e04ecad041f40fe0c0d-1024-680/5899473679_bc16b154e1_b.jpg" alt="woolly mammoth" data-mce-source="Flickr/Mammut" /><p class="source"><span>Flickr/Mammut</span></p></div><p></p></div></div>We often think of Africa as being incredibly rich in species diversity. But in fact, parts of Europe and the New World (like Texas and Argentina) were once just as rich, Faurby said.</p><p>In addition, the bigger diversity of animals we see in mountainous areas may be at least partly due to the fact that mountains provided protection from hunting and habitat destruction.</p><p>The findings not only give us a better understanding of global biodiversity, but could also aid in conservation efforts, by establishing baseline levels of many different species.</p><p>The study only looked at how the presence of humans affected the number of different species, not the size of their populations. That's much harder to do, although it's possible to make crude estimates based on an animal's body size, Faurby said.</p><p>The research was based on historical estimates of animal populations, which are sometimes spotty or nonexistent. And estimating the number of extinct animals based on other animals alive at the time is not always accurate, since they may not have existed at exactly the same time.</p><p>Still, the effects of humans on the diversity of animals is probably an underestimate. "Humans are influencing everything to some extent," Faurby said.</p><p> </p>    <div class="margin-top">        <h3>NOW WATCH: <a href="http://www.businessinsider.com/us-earths-ice-melted-animated-map-climate-change-2015-7">Here's what the US would look like if all the Earth's ice melted</a></h3>        <div>            <div>    <script src="http://player.ooyala.com/v3/6e12e8b3387a44daacfb73afba25a76e"></script>    <div class="ooyala-video-player" data-video-autoplay="false" data-video-id="Z4dGwzdDrnZunZUB10-CqEUToYnAvsHw" data-player-variable="ooyalapopvideo" id="ooyalaplayer_popvideo" style="width:1280px;height:720px"></div>    <script>    if (typeof RunFunctions === 'undefined') { var RunFunctions = []; }     RunFunctions.push(function()    {         var ooyalapopvideo = OO.Player.create('ooyalaplayer_popvideo', 'Z4dGwzdDrnZunZUB10-CqEUToYnAvsHw',{ autoplay: 'false' });     });    </script>    <noscript><div>Please enable Javascript to watch this video</div></noscript></div>        </div>        <script>(function() { function createPlayer() { OO.ready(function() { RunFunctions.forEach(function(ooyalaFunction) { ooyalaFunction(); }); RunFunctions = [];}); } createPlayer(); }()); </script>    </div>

Disturbing maps show how mankind has driven some of the world's largest animals into extinction

<ul class="summary-list"><li>Scientists discovered a host of megafauna remains during the construction of a new town in southwest England.</li><li>They included the <keyword id="13117035" type="UNKNOWN" weightage="60" keywordseo="wooly-mammoth" source="Orion">wooly mammoth</keyword>, a wooly rhinoceros, a wolf, and hyena remains.</li></ul><p>Scientists uncovered the remains of several extinct animals, including a wooly mammoth, wooly rhinoceros, and wolf in Devon, southwest England</p><p>Experts said that the findings, estimated to be from the last Ice Age around 30,000-60,000 years ago, are an "exceptional" discovery that sheds light on the megafauna that roamed early <keyword id="11892697" type="UNKNOWN" weightage="60" keywordseo="britain" source="Orion">Britain</keyword>.</p><p>The well-preserved samples included a tusk, molar tooth, and other bones of a wooly mammoth and the incomplete skull and lower jaw of a wooly rhinoceros, The Sherford Consortium said in a press release.</p><p>Researchers also found a virtually complete wolf skeleton and partial remains of animals including a hyena, horse, and red fox.</p><p>The bones of various small mammals such as bats and shrews were also found. </p><div type="image" title="Woolly mammoth tusk found in Devon, England." height="2592" width="4608" msid="89391455" hostid="261"></div><div type="image" title="Wolf skull found in Devon, Britain." height="2592" width="4608" msid="89391456" hostid="261"></div><p>The team made the discoveries during the construction of new town Sherford, a new 5,500-home community under development on the edge of Plymouth.</p><p>"This is a major discovery of national significance – a once in a lifetime experience for those involved," Rob Bourn, managing director of Orion Heritage and lead archeologist on the project for the Sherford Consortium, said.</p><p>"Construction happening at Sherford is the sole reason these findings have been discovered and it is remarkable that they have laid undisturbed until now."</p><p>Bourn said that it was a "rare and special occurrence" to find artifacts untouched for so long, as well to have so many complete or semi-complete individual animals.</p><p>Researchers said that studying the remains, particularly the herbivores and their food sources, will provide an insight into the plants that may have previously existed in the local environment.</p><p>It is currently unclear whether the animals found at Sherford coexisted around the same time or existed at different points over a more extended time period, researchers said.</p><p>One theory is that some of the creatures fell into a pit and were unable to escape, and carnivorous scavengers followed and were also trapped.</p><p>Another theory is that the animals died elsewhere, and the bones were washed into the area over time.  </p><p>The Sherford Consortium said it would preserve the area where the remains were found.</p>

Remains of a wooly mammoth, a rhino, and a wolf unearthed on a building site

<ul class="summary-list"><li>Anthropologists found 60 fossilized human footprints in New Mexico that date back 23,000 years. </li><li>The finding reveals humans <a href="https://www.businessinsider.com/people-in-north-america-15000-years-earlier-than-archaeologists-thought-2020-7">occupied North America thousands of years earlier</a> than we thought - and thrived on the continent during the last <keyword id="12161803" type="UNKNOWN" weightage="60" keywordseo="ice-age" source="Orion">ice age</keyword>.</li></ul><p>A new discovery offers definitive evidence that humans were in North America far earlier than archaeologists previously thought - a whopping 7,000 years earlier.</p><p>Fossil footprints found on the shore of an ancient lake bed in New Mexico's White Sands National Park date as far back as 23,000 years ago, making them the oldest ever found in North America. That timing means humans occupied southern parts of the continent during the peak of the final ice age, which upends our previous understanding of when and how they moved south.</p><p>The previous idea was that the first people to occupy North America crossed a land bridge that existed between modern-day Siberia and Alaska during the last ice age, between 26,500 and 19,000 ago. According to that theory, they would have had to settle near the Arctic because ice sheets covering Canada made it impossible for them to go south. Then later, once these glaciers melted between 16,000 and 13,500 years ago, the migration toward South America began.  </p><p>This new finding, however, "definitively places humans in North America at time when the ice sheet curtains were very firmly closed," Sally Reynolds, a paleoecologist at Bournemouth University in England and co-author of the new study, told Insider.</p><div type="image" title="white sands footprints" height="2743" width="3435" msid="86467850" hostid="261"></div><p>So most likely, Reynolds said, humans migrated south in multiple waves, and one of those was before the last ice age. Those early people may have even sailed down the Pacific coast. </p><p>"Then more came down after the ice receded," Reynolds said.</p><p>The <a href="https://eurekalert.us12.list-manage.com/track/click?u=394dac0d2e831bfd2ca7fc3b5&amp;id=e78af6d569&amp;e=547fa823dc7fa823dc">finding</a> was published Thursday in the journal <keyword id="11896083" type="UNKNOWN" weightage="100" keywordseo="science" source="Orion">Science</keyword>, and the study also describes nearby tracks found from mammoths, dire wolves, and giant ground sloths - prey for ancient humans.</p><h2>The oldest known footprints in the Americas</h2><div type="image" title="white sands footprints" height="4008" width="2802" msid="86467852" hostid="261"></div><p>Reynolds' team found 60 human footprints between 21,000 and 23,000 years old. The researchers estimated the tracks' age by dating microscopic seeds from an aquatic plant found in layers of lake sediment that sandwiched the prints.</p><p>"It's unequivocal evidence," Reynolds said. "The layers go seeds, footprints, seeds."</p><p>The footprints are now the oldest in the Americas, taking over from <a href="https://www.businessinsider.com/scientists-discover-oldest-human-footprint-in-americas-2019-4">a 15,600-year-old footprint found in Chile</a> a decade ago.</p><p>Most of the tracks belonged to teenagers and children, the team found, possibly indicating the youngsters played in the area while adults hunted and gathered.</p><p>Reynolds said that before this finding, the earliest estimate as to when humans started occupying North America was 16,000 years ago.</p><p>The only clue that people might have arrived earlier is a set of stone tools and artifacts found in remote Mexican cave. Archaeologists estimated that sediment ensconcing those artifacts was 32,000 years old, but that's not a trustworthy measure, Reynolds said. Artifacts can migrate up and down through sediment layers over time.</p><p>"Footprints, by contrast, are fixed on the landscape," Reynolds said. </p><h2>Humans could have traveled south by boat</h2><p><strong> <div type="image" title="white sands footprints" height="3995" width="3000" msid="86467854" hostid="261"></div></strong></p><p>Reynolds said it's not yet clear how, exactly, humans traveled to the White Sands site - though there are several leading theories.</p><p>One suggests they traveled down the west coast via an ice-free corridor of land. Another proposes that they <a href="https://www.businessinsider.com/people-in-north-america-15000-years-earlier-than-archaeologists-thought-2020-7">came by boat</a>, possibly sailing from modern-day Russia or Japan and then expanding south by hugging the Pacific Coast. </p><p>Reynolds said she also thinks it's possible our ancestors might have crossed the continent then sailed down the Atlantic coast, before trekking to New Mexico. </p><p>"There's this hovering question mark over the role of their seafaring skills," she said.</p><h2>Ancient humans in North America hunted giant sloths</h2><h2><strong><div type="image" title="An artist’s reconstruction, based on recently discovered footprints, of prehistoric humans in present-day New Mexico hunting a giant ground sloth." height="575" width="1023" msid="86467856" hostid="261"></div></strong></h2><p>This isn't the first remarkable discovery to come from the White Sands site.</p><p>"Its value goes far, far beyond the date of these new footprints," Reynolds said. </p><p>Three years ago, her team <a href="https://www.science.org/doi/full/10.1126/sciadv.aar7621">uncovered a different set of human and animal tracks</a> at the site dating back to about 15,500 years ago. Those footprints revealed an epic battle between predator and prey: A human was stalking a giant sloth.</p><p>"The human was walking right behind it," Reynolds said, adding, "and the sloth is absolutely not liking it."</p><p><a href="https://www.businessinsider.com/giant-sloths-hunted-by-humans-bones-2019-3">Giant ground sloths</a> went extinct some 12,000 years ago. Around the same time, up to 90% of all large-bodied animals in the world, including mastodons, prehistoric horses, and ancient giant armadillos, also went extinct.</p><p>Many archaeologists think that early humans in the Americas played an outsized role in that mass extinction there, given that it happened within a few millennia of their arrival.</p><p>"Humans show up and megafauna start dying," Reynolds said. "It seems like an obvious cause and effect relationship."</p>

Newly discovered fossil footprints show humans were in North America thousands of years earlier than we thought

<ul class="summary-list"><li>Scientists mapped the genome of a saber-toothed cat species named Homotherium for the first time.</li><li>The ancient cat's genes reveal that it was a highly skilled pack hunter that could pursue its prey over vast distances. </li><li>Homotheriums lived on five continents and roamed for millions of years before it went extinct.</li></ul><p>Before the end of the last Ice Age, fierce saber-toothed cats roamed every continent except Australia and Antarctica.</p><p>Although most people probably picture saber-toothed cats with long fangs, not all had such big teeth. One ancient cat in particular, called Homotherium latidens, had shorter canines, leading scientists to nickname it the "scimitar-toothed cat," after the short sword with a curved blade.</p><p>A<a href="http://dx.doi.org/10.1016/j.cub.2020.09.051"> recent study</a> published in the journal Current <keyword id="6502723" type="UNKNOWN" weightage="60" keywordseo="Biology">Biology</keyword> mapped the entire genome of this cat for the first time.</p><p>Based on the extinct predator's genes, the researchers determined that Homotherium was a highly skilled pack hunter, which literally chased its prey to death across large distances.</p><p>"They had genetic adaptations for strong bones and cardiovascular and respiratory systems, meaning they were well suited for endurance running," Michael Westbury, a co-author of the study and evolutionary genomicist at the University of Copehagen, said <a href="https://www.eurekalert.org/pub_releases/2020-10/uoct-adl101320.php">in a press release</a>. </p><p>The cats "likely had very good daytime vision and displayed complex social behaviors," Westbury added.</p><h2>These cats could pursue their prey until it was exhausted</h2><div type="image" title="homotherium" height="1233" width="2466" msid="78774588" hostid="261"></div><p>Westbury's team pulled the ancient cat's DNA from a thigh bone they found in permafrost (perpetually frozen ground) outside Dawson City in the Canadian Yukon.</p><p>The researchers determined the fossil to be at least 47,500 years old.</p><p>An analysis of the creature's genome showed that Homotherium had at least 31 genes that coded for adaptations to help it hunt successfully during the day. Specifically, its genes suggest that Homotherium had excellent daytime vision, strong bones, and a powerful heart and lungs.</p><p>Such adaptations "may have enabled sustained running necessary for hunting in more open habitats and the pursuit of prey until their point of exhaustion," the study authors wrote.</p><p>What's more, Westbury and his colleagues found that these cats had "well-developed social behavior" and likely lived and hunted in packs similar to the way modern lions do.</p><h2>These ancient cats we more abundant than scientists thought</h2><p>The DNA analysis also revealed that Homotherium was more abundant than its limited fossil record suggests.</p><div type="image" title="homotherium" height="1500" width="2000" msid="78774593" hostid="261"></div><p>Based on the scimitar-toothed cat's DNA, Westbury's team found that the mother and father of the Homotherium that this thigh bone belonged to were genetically quite diverse from one another — more different, they concluded, than any two parents of modern cats like tigers.</p><p>To have that range of genetic diversity, the study authors wrote, there must have been a large population of Homotherium latidens roaming the world. </p><p>"Genetic diversity correlates to how many of a given species that exists," Westbury said, adding, "our best guess is that there were a lot of these big cats around." </p><p>Saber-toothed cats — including Homotherium — and modern cats share a common ancestor. But about 22.5 million years ago, the ancient cats genetically split from all other living cats to become their own group of species, according to the study authors.</p><p>The scimitar-toothed cats then diverged from their longer-toothed brethren, called smilodons, about 18 million years ago, according to <a href="https://www.eurekalert.org/pub_releases/2017-10/cp-ado101217.php">a 2017 study</a>.</p><h2>The cats went extinct alongside other giant creatures at the end of the last Ice Age</h2><p>Previous fossil evidence has revealed that scimitar-toothed cats had longer forelimbs than hind limbs and boasted svelt bodies built for running after prey. They chased mammoths, giant ground sloths, and other large <keyword id="6371668" type="UNKNOWN" weightage="60" keywordseo="animals">animals</keyword> during the Pleistocene era, which started roughly 2.5 million years ago and lasted until the end of the last Ice Age, about 11,700 years ago.</p><p>"This was an extremely successful family of cats. They were present on five continents and roamed the Earth for millions of years before going extinct," Ross Barnett, another co-author of the study, said <a href="https://www.eurekalert.org/pub_releases/2020-10/uoct-adl101320.php">in a press release</a>. </p><div type="image" title="homotherium" height="2663" width="3551" msid="78774596" hostid="261"></div><p>But even these hunters couldn't overcome the environmental changes brought on by a warming world, especially when paired with increased competition with humans for limited prey. </p><p>The <a href="https://www.cell.com/current-biology/pdfExtended/S0960-9822(17)31198-3">2017 discovery</a> of a 28,000-year-old Homotherium jaw bone in the UK's North Sea led researchers to conclude that these saber-toothed cats went extinct at the end of the Pleistocene, part of a <a href="https://www.frontiersin.org/articles/10.3389/fevo.2019.00226/full">planet-wide extinction</a> that hit <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/gj.2633">all the world's megafauna</a>, including <a href="https://www.businessinsider.com/ancient-cave-bear-carcass-siberia-permafrost-intact-organs-nose-2020-9">cave bears</a> and ancient horses.</p>

New analysis of a saber-toothed cat fossil reveals the ancient animals were ruthless, highly skilled hunters

<ul class="summary-list"><li>Researchers discovered thousands of drawings adorning three rock shelters in the Colombian <keyword id="18635" type="CITY" weightage="60" keywordseo="Amazon">Amazon</keyword>.</li><li>The drawings cover more than 2.5 miles of rock and are at least 11,800 years old.</li><li>They depict an ancient hunter-gatherer society that lived at the end of the Ice Age, with scenes of humans hunting mastodons and images of other extinct animals like Ice Age horses.</li></ul><p>More than 12,000 years ago, near the end of the Ice Age, humans hunted mastodons: ancient mammals that resembled a cross between mammoths and elephants. But by around 11,600 BCE, humans had likely killed many of the mastodons off. </p><p>At least, that's the leading theory among many paleontologists. A recent discovery bolsters it: Researchers recently uncovered thousands of drawings from an Ice Age-era tribe, hidden deep in the Amazon rainforest.</p><p>The drawings are spread across three rocky shelters in Colombia's Serranía La Lindosa region. They were first painted between 12,600 and 11,800 years ago. The largest shelter alone, Cerro Azul, has drawings covering more than 2.5 miles of its surface. The images show some of South America's earliest inhabitants and their interactions with Ice Age-era animals, including giant sloths, ancient llamas, and Ice Age horses.</p><p>Some drawings, like the one below, even depict what experts think are <keyword id="1541215" type="PERSON" weightage="60" keywordseo="Mastodon">mastodon</keyword> hunts.</p><div type="image" title="Mastodon hunt" height="1200" width="1600" msid="79534712" hostid="261"></div><h2>Thousands of ancient, remarkably detailed images </h2><p>Many of the images show unusual levels of detail for such ancient art, according to José Iriarte, a professor of archaeology at Exeter University and a leader of the team that made the discovery.</p><p>"The Ice Age horse had a wild, heavy face," Iriarte <a href="https://www.theguardian.com/science/2020/nov/29/sistine-chapel-of-the-ancients-rock-art-discovered-in-remote-amazon-forest">told The Guardian</a>. "It's so detailed, we can even see the horse hair. It's fascinating."</p><p>The researchers published a study about the three sites in April in the journal <a href="https://www.sciencedirect.com/science/article/abs/pii/S1040618220301907">Quaternary International</a>. But on Monday, the University of Exeter <a href="https://www.exeter.ac.uk/news/research/title_829032_en.html">released a statement</a> with information about the discovery to coincide with the sites' coverage in an episode of "Jungle Mystery: Lost Kingdoms of the Amazon," a documentary series set to air in the UK starting Saturday. </p><p>Mark Robinson, an environmental archaeologist at the University of Exeter and coauthor of the April study, said in a statement that the people who produced these paintings likely moved into South America at a time of "extreme climate change." The Ice Age was ending.</p><div type="image" title="ancient horse.JPG" height="1200" width="1600" msid="79534716" hostid="261"></div><p>"The Amazon was still transforming into the tropical forest we recognise today," he said. "The paintings give a vivid and exciting glimpse in to the lives of these communities. It is unbelievable to us today to think they lived among, and hunted, giant herbivores, some which were the size of a small car." </p><p>The paintings are so vast and numerous that they will likely take many years to study fully. Plus, Jeison Lenis Chaparro-Cárdenas, an anthropologist at the National University of Colombia and member of the research team, told Business Insider that "the vast majority" of cliffs in the region have not yet been fully explored.</p><h2><strong>A deeper look into the lives of prehistoric Amazonians</strong></h2><div type="image" title="pictogram amazon colombia .JPG" height="1200" width="1600" msid="79534718" hostid="261"></div><p>In addition to ancient megafauna, the cliff and cave drawings depict alligators, tapirs, monkeys, turtles, serpents, and porcupines. They also include geometric shapes, as well as everyday scenes showing people hunting and interacting with plants and trees. </p><p>"There are many things and moments of excitement and amazement," Chaparro-Cárdena said. He added that most images revolved around a common theme: "the majesty of the nature that surrounded them and with which they interacted in their daily lives."</p><div type="image" title="ochre tablet" height="505" width="646" msid="79534721" hostid="261"></div><p>The team conducted soil excavations around the rock-art sites to find clues about how the inhabitants scraped clay to extract ochre, a pigment they used to make the drawings. </p><p>Those investigations revealed the remains of animals likely eaten by the ancient people, including piranhas, turtles, armadillos, and capybaras, according to Chaparro-Cárdenas. Modern-day inhabitants of the Amazon rainforest still eat many of the animals found at the sites.</p><p>"This shows a great variety of resources that were used by the inhabitants of the Amazon for more than 12,000 years," Chaparro-Cárdenas said.</p><h2>A perilous journey '100% worth it' </h2><p>The team first began studying the region in 2014, two years before the FARC struck a peace treaty with Colombia's government. The Serranía La Lindosa region falls under FARC territory, and entering safely still requires careful negotiations with the guerilla group, <a href="https://www.theguardian.com/science/2020/nov/29/sistine-chapel-of-the-ancients-rock-art-discovered-in-remote-amazon-forest">according to The Guardian</a>.</p><p>The region also has many natural hazards. Poisonous snakes and caimans inhabit the area, which is an hours-long journey from the nearest town. </p><p>At one point, a large, venomous bushmaster snake blocked the research team's path. They had to walk around it, knowing they were far from any hospital, as the Guardian reported.</p><p>"You're in the middle of nowhere," Ella Al-Shamahi, an archaeologist who worked with the team on the forthcoming documentary, told The Guardian. But she added that braving the dangers was "100%" worth it.</p>

More than 2.5 miles of cliff paintings found hidden in the Amazon rainforest show ancient hunter-gatherers killing Ice Age creatures

<ul class="summary-list"><li>Archaeologists have long debated when and how the first people made it to North America from Asia.</li><li>Researchers previously thought early humans crossed the Bering land bridge from Siberia to Canada 13,000 years ago.</li><li>But artifacts discovered in a Mexican cave shift the timeline, revealing people may have been in North America 30,000 years ago.</li><li>The land bridge was impassable at that time, so the research suggests the first Americans arrived by sea.</li></ul><p>New evidence suggests people have been living in North America twice as long as archaeologists previously thought.</p><p>Stone tools and artifacts discovered in a remote cave in Zacatecas, Mexico, offer evidence that humans were on the continent as far back as 32,000 years ago, during the last ice age.</p><p>That upends the idea that the first people arrived in North America between 18,000 and 13,000 years ago after continent-hopping from modern-day Siberia via the Bering land bridge. The new finding, described in <a href="https://www.nature.com/articles/s41586-020-2509-0">a study</a> in the journal Nature on Wednesday, pushes that timeline back at least 15,000 years. It also shatters our previous understanding of how humans arrived in the North America: Since the land bridge was blocked during the last ice age and only opened after the ice started to recede, the new timeline means early people likely made their way on the ocean.</p><p>"We have enough evidence to challenge the existing paradigm," Ciprian Ardelean, the lead author of the new study, told Business Insider.</p><p><div type="image" title="archaeology cave north america" height="683" width="911" msid="77112054" hostid="261"></div></p><h2>A sheltered cave high in the mountains</h2><p>The 200-foot-wide cave in which Ardelean's team found the ancient tools, called Chiquihuite Cave, is nearly 9,000 feet up in the Astirello mountains. Locals in the area first guided him to the site in 2012, and there he found stone tools and traces of ash — evidence of early humans.</p><p>Ardelean returned with a team in 2016 and 2017 for further excavations, which yielded nearly 2,000 artifacts. They'd been buried 9 feet deep in the cave walls and floor. </p><p><div type="image" title="archaeology cave north america" height="1365" width="1820" msid="77112060" hostid="261"></div></p><p>The age of those artifacts suggests early people occupied Chiquihuite Cave on and off over 17,000 years — a period from about 30,000 to 13,000 years ago. Ardelean said it's likely humans used the site as a recurring shelter: a pit stop during seasonal migrations crisscrossing the continent.</p><p>The model this discovery challenges — that the first humans arrived in North America after crossing over land from Siberia — has been around since the 1930s. This line of thought suggests that humans slowly traversed southward, leaving behind distinct, grooved spear tips that became known as Clovis points.</p><p>It's known as the "Clovis-first" model of <keyword id="6360337" type="UNKNOWN" weightage="60" keywordseo="archaeology">archaeology</keyword>.</p><p><div type="image" title="Clovis points" height="565" width="1316" msid="77112066" hostid="261"></div></p><p>But starting in the mid-1970s, researchers began uncovering sites dating back more than 13,000 years. Those discoveries multiplied in subsequent decades. Scientists found fossilized human poop that's <a href="https://science.sciencemag.org/content/320/5877/786.abstract">about 14,000 years old</a> in an Oregon cave. Artifacts from <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0141923">a settlement in southern Chile</a> were dated to be between 14,500 and 19,000 years old. A horse jaw bone that bore human markings suggested humans occupied the Bluefish Caves of Yukon, Canada <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169486">24,000 years ago</a>.</p><p>But none of these discoveries pushed the timeline as far back as Ardelean's study.</p><p><a href="https://www.nature.com/articles/s41586-020-2491-6">A second paper</a> published Wednesday throws even more cold water on the "Clovis-first" model. For that research, two archaeologists looked at artifacts and traces of human occupation from 42 sites across North America. By dating those findings, the researchers modeled how and when people dispersed across the continent. They concluded that humans were "probably present before, during, and immediately after the Last Glacial Maximum" — that's the peak of the last ice age, which occurred between 26,500 and 19,000 years ago.</p><p>"As these older-than-Clovis sites increased in number, most archaeologists came to reject the Clovis-first model," Ruth Gruhn, an archaeologist who was not involved in the study, told Business Insider via email. "These two papers in Nature will finally put an end to it."</p><p><div type="image" title="archaeology stone tool north america" height="2021" width="2695" msid="77112068" hostid="261"></div></p><p>She added, "the evidence now indicates that people have been in the western hemisphere at least twice as long as archaeologists and geneticists believed."</p><h2>The first people in the Americas didn't cross the Bering Land Bridge</h2><p>If humans were on the continent before or during the peak of the last ice age, they could not have come via the Bering Land Bridge, since it would have been partially submerged or blocked by impenetrable ice sheets.</p><p>"Just because the bridge is considered a standard entry doesn't mean it's the only one," Ardelean said, adding, "the panorama of human arrivals during the Last Glacial Maximum is much more complex than we thought."</p><p><div type="image" title="bering land bridge" height="385" width="569" msid="77112073" hostid="261"></div></p><p>Lorena Becerra-Valdivia, an archaeological scientist at the Universities of Oxford and New South Wales and the lead author of the second paper, told Business Insider that "the new findings suggest that humans likely took a coastal route." </p><p>That means they were probably seafarers who <a href="https://www.sciencemag.org/news/2017/08/most-archaeologists-think-first-americans-arrived-boat-now-they-re-beginning-prove-it">arrived by boat</a>, possibly from modern-day Russia or Japan. Then they expanded south by sailing down the Pacific Coast. </p><h2>A migratory people who hunted terrestrial animals to extinction</h2><p>Regardless of early humans' route to North America, both Ardelean and Becerra-Valdivia think they were anatomically modern humans.</p><p>"Neanderthals had already disappeared from the fossil record by the time Chiquihuite Cave was occupied," Becerra-Valdivia said.</p><p>The archaeologists' own experience in the cave suggests its sheltered location helped these early hunter-gatherers survive during the ice age. Ardelean said summers in the area were too wet to do field work, so they conducted research in the winter. Outside, he said, temperatures would be below freezing temperatures and snow would fall.</p><p>"But the cave itself is well insulated, so no matter what happens outside, you could be inside in just your T-shirt. That speaks of the cave's potential as a shelter," he said.</p><p>About 14,000 years ago, when the climate started to warm further, early humans were finally able to thrive and expand across the Americas. They were likely fearsome predators, Becerra-Valdivia said, hunting land mammals like horses, camels, and mammoths to extinction.</p><p><div type="image" title="An artist’s reconstruction, based on recently discovered footprints, of prehistoric humans in present-day New Mexico hunting a giant ground sloth." height="575" width="1023" msid="77112075" hostid="261"></div></p><p>"This expansion likely had a major role in the dramatic decline of megafauna in the region," she said.</p><p><a href="http://advances.sciencemag.org/content/5/3/eaau4546">Some research</a> suggests early humans in South America may have even <a href="https://www.businessinsider.com/giant-sloths-hunted-by-humans-bones-2019-3">butchered giant ground sloths</a>.</p>

Humans arrived in North America at least 15,000 years earlier than we thought, discoveries show — which suggests they came by boat

<p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/5a7dbb5dd0307260008b4b2b-2000/anbeto floating above fossil taking picturesimg9646beto stock.jpg" alt="PBS First Face of America" data-mce-source="Alberto Nava" /><p class="source"><span>Alberto Nava</span></p><p class="caption">Archaeologists have found countless artifacts deep within the Sac Aktun cave - but now it's under threat.</p></div><p></p></div></div></p><ul><li><strong>The Sac Aktun cave system holds artifacts stretching back 15,000 years, including preserved remains of Ice Age megafauna to Mayan artifacts.</strong></li><li><strong>It was recently discovered to be the largest underwater cave system in the world. </strong></li><li><strong>The cave is one of the world's most important underwater archaeological sites, but it's under threat from pollution and development.</strong></li></ul><hr /><p> </p><p>One of the world's largest and most important underwater archaeological sites is under threat from pollution and development.</p><p>The recently mapped Sac Aktun cave system on Mexico's Yucatan Peninsula was recently discovered to be the <a href="https://translate.google.ca/translate?sl=es&amp;tl=en&amp;js=y&amp;prev=_t&amp;hl=en&amp;ie=UTF-8&amp;u=https%3A%2F%2Fwww.gob.mx%2Fcultura%2Fprensa%2Fdan-a-conocer-hallazgos-en-el-sitio-arqueologico-sumergido-sac-actun&amp;edit-text=">largest underwater cave in the world</a> at 216 miles long. It contains some of the oldest human remains ever found in the Americas, as well as countless other artifacts stretching back over 15,000 years.<span></span></p><p><span>"I think it's overwhelming. Without a doubt it's the most important underwater archaeological site in the world," Guillermo de Anda, an archaeologist at Mexico's National Anthropology and History Institute who is leading excavations in the cave <a href="https://www.washingtonpost.com/world/the_americas/experts-vast-underwater-archeology-site-imperiled-in-mexico/2018/02/19/45796d44-15b3-11e8-930c-45838ad0d77a_story.html?utm_term=.3087e957169c">told The Associated Press</a>.</span></p><p><span><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"><img src="https://static-ssl.businessinsider.com/image/5a7dbb86d0307298068b49ff-2000/first facemexicoimg2080.jpg" alt="PBS First Face of America" data-mce-source="Francis Cordero Ramirez" data-mce-caption="The remarkably intact skeleton can help researchers shine a light on how the earliest Americans lived." /><p class="source"><span>Francis Cordero Ramirez</span></p><p class="caption">This remarkably intact skeleton was found in the cave, and it's helping researchers shine a light on how the earliest Americans lived.</p></div><p></p></div></div></span></p><p><span>A <a href="http://www.businessinsider.com/nova-doc-13000-skeleton-found-in-mexico-is-critical-to-human-history-2018-2">remarkably intact, 13,000 year-old skeleton</a> found in the cave in 2007 is one of the oldest examples of human remains in the Americas, and provided a crucial window into how America's earliest inhabitants lived, migrated, and died. The skeleton was recently the subject of a NOVA documentary. </span></p><p><span>Researchers have also identified over 120 sites inside the cave that are filled with Maya-era pottery and bones from over a thousand years ago. They've also discovered bones of long-lost Ice Age megafauna like giant sloths, proto-elephants, and extinct bear species, the AP reports. </span></p><p><span>The cave has undergone periods of flooding and drought throughout history, and has been used for thousands of years by people searching for water and shelter in periods of "great climate stress," de Anda told the AP.</span></p><p><span>Unfortunately, increased pollution and acid runoff from nearby development are threatening the pristine cave.</span></p><p><span>The cave is connected to 248 cenotes, which are used for snorkeling and swimming by an increasing number of tourists. A major highway to the Mexican state of Quintana Roo also runs above the cave system. During periods of intense rainfall, the highway has collapsed into sinkholes, the AP reports.</span></p><p><span>Researchers have also found elevated acidity levels in the cave, likely due to runoff from a nearby dump. That acidity can degrade skeletal remains over time. </span></p>      <div class="margin-top">        <h3>NOW WATCH: <a href="http://www.businessinsider.com/why-are-human-breasts-big-2018-2">The science of why human breasts are so big</a></h3>        <div>            <iframe class="bijwplayerclass" data-player="jwplayer" src="https://content.jwplatform.com/players/6KyrlYzy-CEZHWCBG.html" width="100%" height="100%" frameborder="0" scrolling="auto" style="margin:0px;" allowfullscreen=""></iframe><script>function receiveMessage(event){ console.log(event.data.fullscreen); Android.fullscreen(event.data.fullscreen); }window.addEventListener("message", receiveMessage, false);</script>        </div>    </div>

You Searched For "megafauna extinction" and got 13 results

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One of the greatest extinction mysteries in history is still unsolved

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So many animals will go extinct in the next 50 years that it will take Earth at least 3 million years to recover, a study has found

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Newly discovered fossil footprints show humans were in North America thousands of years earlier than we thought

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New analysis of a saber-toothed cat fossil reveals the ancient animals were ruthless, highly skilled hunters

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More than 2.5 miles of cliff paintings found hidden in the Amazon rainforest show ancient hunter-gatherers killing Ice Age creatures

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Humans arrived in North America at least 15,000 years earlier than we thought, discoveries show — which suggests they came by boat

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The oldest skeleton in the Americas was discovered in the world's biggest underwater cave - but the site is now under threat

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