Uncovering Mammoth Ice Age Extinctions (Full Episode) | Lost Beasts Unearthed | Nat Geo Animals

[narrator] In South Dakota, USA, investigators dig deep into a 200,000-year-old pit, filled with the bones of an Ice Age titan. The mammoth. Mammoths are one of the most famous megafauna that ever existed. Their familiar furry form is what comes to mind as iconic when you think of the Ice Age. ♪♪ A towering colossus, the mammoth roamed the globe for more than a million years. [growls] We knew them. Our species, Homo sapiens, encountered mammoths, saw mammoths. They are a part of our evolutionary story as well. What happened to these once-mighty beasts? And why do they no longer walk among us? Now, new discoveries from a unique site could solve the mystery of why the mammoths disappeared. [Jim Mead] There's so much here. I feel like, after 45 years, I'm just now beginning to know what to study. Did the planet become too hot for these Ice Age titans? Or did our ancestors drive them to extinction? [muffled roar] To solve the secrets of the mighty mammoth's reign, we will see this lost beast like never before, flying inside skin and bone. We'll resurrect its vanished world and reveal the final days of this iconic giant. [♪ curious music playing] The Blacks Hills of South Dakota are one of America's greatest natural wonders. An immense mountain range of rugged beauty, home to acres of forest, and even a national monument, Mount Rushmore. The little town of Hot Springs lies at the foot of this vast wilderness. This frontier settlement is known as the southern gateway to the Black Hills, but it also harbors an extraordinary secret. A prehistoric sinkhole, filled with thousands of fossils. Among them, the bones of one of the largest mammals that ever walked the Earth: the mammoth. Mammoths, to me, are, in many ways, more than exciting. They're iconic. They're big. They're massive. [trumpeting] One has to like mammoths! In charge of the excavation is Dr. Jim Mead, a specialist in mammoth paleontology. Jim was part of a team that came here to Hot Springs when a construction worker's digger pulled an enormous tusk out of the ground. [Mead] We've been excavating in this bone bed for four and a half decades. A long time. I'm paid to do my passion. I love this. And it's neat to be able to look down there and realize when we excavated that mammoth, it hadn't seen light in 140,000 years. It's truly amazing. Jim and his team have found the remains of more than 60 mammoths here. There are now so many, they have had to build a special protective building around the bones to safeguard and investigate them. -[wind blowing] -[♪ somber music playing] Mammoths are an extinct kind of prehistoric elephant. The woolly mammoth, with its large shaggy coat and huge curved tusks, is one of the most iconic lost beasts of all time. But, like the elephants of Africa and India today, mammoths didn't all belong to the same species. From a careful examination of the bones at Hot Springs, Jim can tell that most of the mammoths here are true giants. Here we are clearly at the rear end of the mammoth. This is the femur. That's this bone right here. What this allows us to do is make these measurements, compare them to other measurements and say, "Well, this animal was 12 feet tall." Piecing together the bones at Hot Springs reveals a colossal type of mammoth, carrying a long sloping spine and a huge head. From its jaws, enormous curved tusks stretch to nearly five meters long. Thick skin once covered the flesh and bones. But, unlike the iconic woolly mammoth, this animal was comparatively hairless. This was a Columbian mammoth, a species unique to the Americas. Why are so many of these magnificent animals buried here? And why do they no longer roam the Earth today? -[♪ curious music playing] -[mammoth trumpets] The Columbian mammoth is one of the last mammoth species. Paleontologists think it evolved from an elephant that crossed into North America from Asia millions of years ago when sea levels were lower. This disappearance of these prehistoric beasts is one of the great unsolved mysteries of paleontology. [Mead] We know that mammoths, whether they were in Europe, Asia, or here, are really just a form of elephant, if you will. How come then mammoths are extinct? Not just say here in the Black Hills, but all over North America at pretty much the same time. That's one of many questions we have. Skeletons, like the ones at Hot Springs, could help solve this mystery. The sheer number of mammoths here is exceptional. It's one of the largest concentrations of these animals in the world. The Hot Springs mammoths lived during what scientists call the Ice Age. 200,000 years ago, when the first of these animals died, huge ice sheets blanketed large parts of North America. In some parts, the glaciers were more than three kilometers thick. But, in the south, the climate was very different. The Black Hills were cold, but ice-free, making them the perfect stomping ground for the Columbian mammoths. These titans were the heavyweight champions of the Americas. Weighing in at nine tons and standing over four meters tall, these giants traversed grasslands in search of food. The Columbian mammoths thrived in these milder conditions. It was a highly successful species found as far south as Mexico. So, why did so many die in this one place? A clue could lie in the site's unusual geology. The Hot Springs sinkhole that contains these mammoths formed hundreds of thousands of years ago when the ground surface fell into an underground cavern. Sinkholes are deadly and can open up suddenly without warning. Trapping anyone or anything above them. But researchers discover that when these mammoths died, Hot Springs was the site of a sprawling warm water lake. It means that many of the fossils here lay submerged in water, making them unusually delicate. The warm water here has leached out all the collagen, all the, all the, all the material that gives our body strength, that's leached out, leaving behind basically a shell. So these are actually very delicate at this point. It looks very sturdy and so forth, but it is not. [narrator] Jim works with paleontologist Kelly Lubbers who removes some of the more fragile bones for preservation. Few of the bones show signs of serious injury or trauma. It seems that many of these mammoths drowned. This is a mass grave, but close analysis of the bones reveals that these mammoths didn't all die at the same time, during the original sinkhole collapse. We can see that our sediments are being deposited over an extended period of time, and that also correlates with what we see within our bones. So, that all can tell us that this was not one massive event that killed off the mammoths. We're seeing that these mammoths came in and slowly accumulated over time. Hot Springs was a watery grave. A death pit that claimed the lives of dozens of Ice Age titans again and again. From where I'm standing is about 200,000 years ago to behind me, at the top of the excavation, is about 100,000 years ago. So, you're looking at 100,000 years of deposition of mammoths and sediments and water. It is unique. This is a community of animals that came in here. There is a big story here of the interaction of climate, environment, and these mammoths. It's phenomenal. The Hot Springs bone bed is an extraordinary time capsule. [growling] A 100,000-year chapter in the story of the mammoths. One that could help explain more about their lives at the height of the Ice Age and perhaps why these animals disappeared. But there's a mystery. Why did so many mammoths drown in this seemingly ordinary lake? What drew them here in the first place? The Columbian mammoths were one of the largest They required enormous quantities of plant matter to survive. Preserved plant pollen from the site indicates that the surrounding habitat could have supported a variety of vegetation. And the warm waters of the lake would have provided a fertile ground. Were mammoths coming here to feed? We know that looking at elephants today, these mammoths are probably gulping down three, four, or 500 pounds of vegetation a day. And we know that they're taking in a lot of water. So is there enough here to sustain a herd? [narrator] To support such a large appetite, the Columbian mammoths would have to travel miles in search of suitable food. To understand if these ones were gathering at Hot Springs to feed, the researchers must find out what sort of vegetation they were capable of eating. In New York, Dr. Joy Reidenberg is a comparative anatomist at the Icahn School of Medicine at Mount Sinai. At her laboratory, she studies the tooth of a mammoth to investigate what these giants ate. [Joy Reidenberg] If we look at the mammoth tooth and a modern elephant tooth, we see a lot of similarities. They're both massive structures, comprised of many plates put together. The enamel on these teeth is very thick, but if it were thin, it probably would've cracked because these teeth were under a lot of pressure as they were grinding them together. Mammoths developed a clever adaptation to overcome extensive tooth wear. These beasts had teeth thicker than bricks, but also strong jaws. Their powerful chewing action would've ground down the teeth over time. [grinding] But before the animal risked starvation, a new set of teeth grew in from the back of the jaw... [rumbling] ...and pushed the worn ones out of the front, like a conveyor belt. In a lifetime of about 60 years, mammoths could go through six sets of new teeth, an evolutionary superpower that allowed them to make the most of the poor-quality food -in their environment. -[growls] In the laboratory Jim and his team hunt for further clues to find out if the mammoths were coming here to feed. The best way to understand what the animal's eating is to look at its dung. These unusual specimens provide invaluable information. Visible evidence of what the Columbian mammoths ate. So it tells us about climate, local environment, biotic community, and what was on its dinner plate. Jim has extracted DNA from the dung which confirms that it came from a Columbian Mammoth. With the species established, next he looks at the contents. You can see the texture to it, the fragments. You can see that it's grasses. It's not twigs. It's not leaves. It's not seeds. It's showing that it's a grazer, by all means. So, with this sample and other ones, we know that besides cool season grasses that dominate the diet and warm season grasses, we also get rushes, which are an aquatic plant. good running water. We're also gonna get sagebrush, typical good ol' sagebrush, saltbush, another dry-adapted shrub. The plants identified in the dung would've been very similar to those growing at Hot Springs. It's probably unusual in this part of North America to have that much green vegetation around a pond with warm water. And so, it's an attraction. It's a restaurant out in the middle of nowhere, if you will, for these mammoths. It's highly likely that mammoths were visiting Hot Springs to eat and drink, and perhaps even to bathe. Researchers believe that Columbian mammoths were probably good swimmers, like elephants today. Their huge body mass would've given them natural buoyancy. Why, then, did so many drown in the water? At the deep end of the bone bed, Kelly Lubbers investigates an almost complete skeleton of a huge, sprawled mammoth. Over here, we have Murray, who is one of our more articulated specimens. So articulation essentially just means that the bones are preserved as they would be in place. So, here you can see his whole spine extending down. You can see his rib sticking out. You can see his pelvis over here, that butterfly-shaped bone. Murray's level of preservation is certainly one part that makes him unique. The seemingly shallow lake concealed a hidden danger. The deep sinkhole with steep sides. Mammoths that went too far in to eat or bathe could easily lose their footing. Although mammoths were good swimmers, they were unable to find a foothold and couldn't climb back out. They were doomed to perish in the sinkhole, their bones preserved in the sediment. So, Murray here, since we don't have any sort of indication that he would've been sick or had any sort of injury, would've come in and, likely trying to get out of the sinkhole, died of exhaustion or drowning. This Columbian mammoth is one of 61 individuals discovered so far that wandered into the deep water of Hot Springs. Most of the victims were young males, trapped by the slippery mud on the banks of the lake. But, despite the deaths of these animals, their bones reveal were thriving as recently as 100,000 years ago. So if mammoths did successfully inhabit places like this for millions of years for more than a million years, why did they suddenly disappear? More than 7,000 kilometers from Hot Springs, in France, just east of Paris, is the village of Changis-sur-Marne. It's home to an extraordinary set of mammoth fossils discovered during an excavation at a quarry in 2012. Archeologist Gregory Bayle leads a team here. [Gregory Bayle speaking French] The bones stored here are not like those in Hot Springs. They come from a different [Bayle speaking French] Gregory is able to identify the species thanks to these extraordinarily large teeth. Measuring the distance between the enamel ridges on the surface of the molar reveals that these are the remains of a woolly mammoth. This woolly mammoth from France is very different to those found at Hot Springs. While Columbian mammoths stand nearly four meters tall, the woolly ones in Changis-sur-Marne are nearly a meter shorter, and they had a thick coat of fur to keep their bodies warm. So what was Ice Age life like for these mammoths compared to their cousins on the other side of the world? Complete woolly mammoth skeletons in France are rare. Only three others have ever been found. It makes the discovery at Changis-sur-Marne, an important opportunity to learn more about this elusive creature. The first challenge with a find like this is to sort out all the bones. Over time, the river has moved the remains from their original position, making it difficult to understand how they fit together. Careful analysis reveals a surprise. These bones belong to not just one mammoth, but two. The next step is to build up a more detailed picture about the two mammoths, including their sex and age. Gregory uses the long bones, like the femur, to estimate the height of the Woollies. [speaking French] [♪ gentle music playing] Woolly mammoths evolved from the same common ancestor as their Columbian cousins in America. But they preferred to live in much colder environments. These woollies lived at roughly the same time as the Columbian mammoths in Hot Springs. [growling, trumpeting] But while their American cousins feasted on the tough grasses of South Dakota, in France, blocks of ice would've floated along the rivers that wound through the open plains. The Ice Age was not the single Big Freeze of popular imagination. [rumbling, splashing] Temperatures across the world fluctuated with warmer periods and times of extreme cold. The unstable climate had a direct impact on mammoth numbers and where the different species could be found. Woolly mammoths first emerged in East Asia during a cold period 800,000 years ago. They spread across the steppe that ran all the way through Europe. But around 130,000 years ago, temperatures suddenly rose, wreaking havoc with mammoth populations. In Western Europe, the woolly mammoth almost completely disappeared. The newly dated bones of Changis-Sur-Marne show that it only reappeared on the Continent when temperatures started to drop again. It's an important discovery that could help scientists better understand the movements of the mammoths during the Ice Age and how sensitive they were to change. So what was happening to their American cousins on the other side of the world at the same time? Across the Atlantic, the team in South Dakota have been studying the sediment layers in the pit. They've found evidence for some of these climatic fluctuations. The rising temperatures that drove the woolly mammoths from Western Europe dried up the lake turning it into a muddy quagmire. This is a footprint, and this is a footprint. Think of wandering through a muddy pond, and yet you're in water, but you're making a footprint. You're stepping in it, and you're pulling it out of the mud, and it's making these contortions. [soft growling] Sediment eventually filled the deadly sink hole, making it safe for mammoths and other animals to cross unharmed. The Hot Springs mammoth bones are found below this layer in earlier depths. What we're getting are footprints of a variety of animals. So, they're coming in, doing what they want to, and they can get out. If they couldn't get out, we'd have their fossils. Evidence from both sides of the Atlantic reveals that the constantly changing climate of the Ice Age could affect both species of mammoths in different ways. The Columbians thrived in warmer periods, while the woollies adapted better to cooler conditions. But despite these challenges, both mammoth species were remarkably resilient. They rebounded when temperatures changed back. So, what other pressures did they face in their environment? Mammoths weren't the only species that regularly visited the Hot Springs lake. In the bone bed, paleontologists find the remains of many other animals that died in the thick mud at the bottom of the sink hole. [Olga Potapova] The team is building a complete picture of life at this watering hole. And it seems that water wasn't the only danger faced by the mammoths here. The pit has preserved a host of teeth that belong to animals higher up the food chain, all of them designed to tear into flesh and kill. To defend themselves, mammoths had the mother of all teeth. From birth, their incisors kept growing, reaching up to nearly five meters and weighing in at 45 kilos. These were the mammoths' tusks. So how did these fearsome Ice Age beasts fare alongside each other? [soft growl] Jim's team has uncovered 121 tusks in the sink hole pit. This is one of our larger tusks. The nice thing about it, you can see the whole length. You get an idea of how massive it is at the top. And some tusks, you can tell if the animal is quote "left-handed or right-handed" on how much these tusks are worn. These sharp solid ivory tusks were not only used for fending off predators. Mammoths could clear snow with them to get to the undergrowth during long, cold winters. [breeze blowing] We should look at tusks to be like a multi-tool. It's multiple uses. There's a site, oh, about an hour from here where two mammoths are battling with their tusks. They're getting entwined, and they get stuck. So a tusk like this could easily be used by a female, getting rid of predators. But the team at Hot Springs has also found evidence of another astonishing giant that could give a mammoth a run for its money. [Potapova] The short-faced bear was larger than the modern grizzly or polar bear, and a formidable Ice Age predator. The strong jaw and sharp teeth allowed it to tear through meat. The bears may have become trapped in the sink hole scavenging on unlucky dead mammoths. But they weren't regularly hunting them. The short-faced bear was just one of many supersized creatures that thrived alongside the mammoths. There were saber-toothed tigers with fangs the size of daggers, giant lumbering ground sloths, and a rhinoceros with a woolly coat. But as recently as 4,000 years ago, all of these mega beasts had disappeared. Not just the mammoths. Across the history of our planet, mass extinctions have happened for many different reasons. Natural catastrophes such as volcanic eruptions, meteors, and disease have wiped out huge swathes of animal life, like the dinosaurs. But there's no hard evidence that anything like this happened at the end of the last Ice Age. The extinction that killed off the mammoths is unique, in that it only affected large mammals. Why? Evolution expert Steve Brusatte from Edinburgh University is among researchers who believe a new species played a significant role in driving the mammoths and the megafauna to extinction. There is enormous debate among scientists still today about why the mammoths died out. And for me, I think the evidence points in one direction. There is a killer that has been implicated, and that killer, very sadly, is us. Humans. Early humans were hunter-gatherers who migrated from the African continent probably in several waves as early as two million years ago. One possibility is that the arrival of modern human hunters in places like North America may have pushed these animals over the edge as they struggled with fluctuating temperatures. Steve suspects that the mammoth's physiology may have made them particularly vulnerable to these highly intelligent predators. This right here is the skull of a young elephant. It gives us some insight into a bit of a drawback that not just elephants today, but mammoths in the past had. A hindrance that affected them. And that is they're such big animals. Mammoth calves were very big and developed in the womb for long periods. Like elephants today, it probably took about 22 months for the baby to be born. That's a long time for something to go wrong. And if there was a disaster, a fire, a flood, or maybe some human hunters coming through and decimating a population, mammoths couldn't recover very quickly. It would've taken mammoths a long time to regain their numbers. But did early humans really hunt these giants? And if so, in what numbers? [distant roar] At the Changis-Sur-Marne site, the team found evidence that humans were here, too. Near the mammoth bones, they find several small fragments of flint and stone that had been shaped and worked into stone tools. Could these shards be the remains of spear or arrowheads? Evidence that humans here were hunting and killing mammoths. [trumpeting roar] Gregory has a theory of how humans may have created the microscopic marks. It's not necessarily the result of hunting. The flint fragments and bones date to the age of Neanderthals in Europe, an early species of human who lived alongside our ancestors. Gregory isn't convinced that these are hunting tools. The scratch marks are strong evidence that Neanderthals butchered mammoths for their meat. But without the remains of traps or complete spearheads, it's difficult to prove if humans actually killed these two mammoths. Even though Neanderthals were fierce hunters of the Ice Age, hunting mammoths would've been no easy task. Due to their size, fearsome tusks, and the thickness of their flesh, mammoths would've been very difficult to kill. Gregory thinks the impact of hunting by prehistoric humans could only have been a small factor in the overall extinction of the mammoth. Ancient humans would have mostly hunted smaller animals that were easier to kill, like horse, deer, and bison. Our ancestors walked among the mammoths for more than a million years, and it's unlikely that they alone wiped them out. So what happened to the last of the mammoths? And how did their species finally come to an end? The mammoths at Hot Springs in South Dakota and Changis-Sur-Marne in France both managed to adapt to periods of dramatic temperature change. When temperatures became too hot or too cold, they retreated to more suitable areas and returned when conditions improved. But around 15,000 years ago, there was another sudden rise in global temperatures that affected the mammoths' habitat around the world. And this time, neither the Columbian nor the woolly mammoths would ever recover. It's a mystery that continues to puzzle researchers. Adrian Lister is a paleobiologist at the world-famous Natural History Museum in London. Its stores contain an amazing array of fossils from the Ice Age. Adrian and his team have the remains of an almost complete adult male woolly mammoth and at least four younger individuals here. These animals died after falling into pits in the ground left by retreating ice. Radiocarbon dating of the bones has revealed an important result. The mammoths are only 14,000 years old. We only need a very small amount of bone or tooth to do that. If we're lucky, we can also get DNA from that. So, from tiny sample like that, we can learn an awful lot about the animal. Analysis of the bones reveals that these animals were in good health started to rise. Scientists think that at first, mammoths thrived on the lush grasses left behind as the glacial ice retreated. But global warming did more than just melt ice. The open grasslands that mammoths preferred steadily began to change. Over the next few thousand years, trees covered the mammoth steppe, creating a leafy canopy. At the same time, the mammoths disappeared. Why couldn't they survive in the woodlands? A clue lies with remains from frozen Siberia. They reveal how woolly mammoths were very specialized and adapted to thrive in the cold environment and tough grasslands of the mammoth steppe. [Adrian Lister] This is a mammoth mandible or lower jawbone from Siberia, and you can see the two huge molar teeth in the jaw. Each one of these is just the lower teeth. And these very thin, finely spaced enamel bands like this are really adapted to grass eating. This is some real mammoth hair from one of the Siberian carcasses preserved in the ice. The hair could be up to a meter long. It's really thick and dense. It also had a fine layer of wool close to the skin. This, again, was one of the specializations of the mammoth for the Ice Age environment. These adaptations evolved over millions of years. These are three fossil teeth showing the evolution of the woolly mammoth. This one is about two million years old, this one's about half a million years old, and this is the classic woolly mammoth of about 50,000 years old. The earliest tooth has very few enamel ridges and is shorter than the woolly mammoth's. Perfect for eating soft leaves from trees and shrubs. As they evolved, the teeth got taller and the ridges more numerous to tackle tough grasses grazed from the ground. By the time the Condover mammoths were roaming the UK, their teeth had become so highly specialized, they couldn't have eaten anything but grass. [Lister] So, we can see an evolutionary succession leading to the very specialized woolly mammoth in its teeth. Rising temperatures increased the number of trees, replacing the grasses that mammoths relied on for food. Trees require a certain warmth to grow. Even today, if you travel northwards through Siberia, you pass through the rich coniferous forest. Eventually, the trees start thinning out, and by the time you get past the Arctic Circle, it's the open tundra. Once the climate started to warm from about 15,000 years ago, their range progressively spread northwards, until we got to the situation we're in today. Adrian thinks that this loss of habitat was devastating for the mammoths. They were so adapted to eating and digesting grass, they couldn't survive on leaves alone as trees took over. [Lister] I think most of the work of reducing the mammoth populations was done by the climate change and the vegetation changes that followed. And it may be that that alone is enough to account for extinction. Human populations thrived in this warming environment, as the remaining Columbian and woolly mammoths struggled. Astonishing fossil discoveries in the far north shed light on the lives of the very last of these Ice Age animals. [Brusatte] There was one group of mammoths that found refuge on an island, an island called Wrangel Island, way up in the Arctic. Around 12,000 years ago, sea levels rose along the Arctic coast of Siberia, trapping a group of woolly mammoths on Wrangel Island. They survived until about 4,000 years ago, when the pharaohs were building the pyramids of Egypt. These mammoths were not well. They were not healthy. Their populations were so small that they became inbred. The islands they lived on were so harsh. They were cold. There wasn't a lot of plants growing there. For the last mammoths on Earth, life in the Arctic was a bleak existence. The populations were so small, the genetic defects piled up, and sometime around 4,000 years ago, the very last mammoth breathed its final breath on Wrangel Island. For more than a million years, these extraordinary giants thrived across multiple continents. They scaled land bridges revealed by lower sea levels and fine-tuned their adaptations to cold climates with specialized teeth and fur. saw mammoths, drew mammoths on cave walls, hunted mammoths. There have been dozens of these cycles of glacial and interglacial periods, of times when the ice grows and the ice melts, but it was only this most recent one when the megafauna died. There is still fierce scientific debate about the death of the mammoths. 10,000 years ago, with the dawn of the end of the glacial period, their world transformed. As temperatures warmed and humans spread, these giants finally disappeared forever. It's one of the best-studied examples of extinction that we have, and yet we're still arguing about whether it was the climate change, the vegetation change, people, or I think probably a combination of all three. Today, work continues at sites like Hot Springs. New discoveries here could yet transform what we know about this majestic beast and the role that climate and our ancestors might have played in its disappearance. There's something critical that is gone. Something created on a knickpoint that they've disappeared. Maybe that story is here or nearby. We have a lot to work on. Today, when we're so concerned about the endangered status and potential extinction of large animals like the elephants, which are so closely related to the mammoth, understanding why the mammoth went extinct can help us to hopefully preserve their living relatives. Discovering the truth behind their disappearance would not only solve one of nature's great mysteries. The answer might help save other species from one day sharing the fate of this magnificent lost beast.