The last Ice Age was home to giant mammals on every continent: woolly mammoths and woolly rhinos in the north, sabertooth cats and dire wolves in North America, giant ground sloths and strange hoofed animals in South America, and huge marsupials in Australia. They lived beside many animals we still know today, such as reindeer, musk oxen, horses, and wolves. Most of the giants vanished between about 50,000 and 10,000 years ago, and exactly why is still argued over.
The Giants of Every Continent
- Northern Europe and Asia: woolly mammoths, woolly rhinos, cave bears, horses, and deer.
- North America: mammoths, mastodons, sabertooth cats, dire wolves, horses, camels, and ground sloths.1PubMed Central. Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: reassessing the age of Wally’s Beach, Canada
- South America: giant ground sloths such as Lestodon, plus Toxodon and Macrauchenia, hoofed animals found nowhere else.2PubMed Central. First 87Sr/86Sr isotope data for the extinct sloth Lestodon armatus: insights into the spatial ecology of South American Late Pleistocene megafauna3PubMed. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates
- Australia: Diprotodon, the largest marsupial that ever lived, along with giant kangaroos and reptiles.4Quaternary International. New ages of the world’s largest-ever marsupial: Diprotodon optatum from Pleistocene Australia
Scientists call animals over about 45 kilograms (100 pounds) megafauna. In Australia every land animal over 100 kilograms died out, along with six of seven groups weighing 45 to 100 kilograms.5PubMed. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago On the northern grasslands, plant-eaters averaged around 500 kilograms, compared with about 180 kilograms for grazers today.6PubMed Central. The large mean body size of mammalian herbivores explains the productivity paradox during the last glacial maximum
Many people picture all of these animals plodding through snow. Ice sheets did cover the far north, but much of the world stayed ice-free, and Australia and South America had warm, dry, or tropical habitats. Diprotodon, for instance, roamed Australia’s northern tropics. The name “Ice Age” describes global cooling, not every animal’s home.
Ice sheets buried Canada and northern Europe, but areas south of them had cold grassland, forest, or desert. Cooling changed rainfall as well as temperature, and in many places the main change was a drier climate rather than snow.
Some of these animals were giant versions of living groups, like sloths and kangaroos. Others, like Toxodon, belonged to lines with no living members. Horses and camels once lived in North America before vanishing there in the Ice Age extinctions.
Woolly Mammoths and the Cold Grassland
Mammoths were built for the cold. They had a double coat of long outer hair and thick underwool that covered even the trunk, ears, and tail, and a thick layer of fat under the skin added insulation.7Academic Press. Paleoecology of Beringia Their ears were small and furry, so they lost less heat than an elephant’s big ears.8Academic Press. Paleoecology of Beringia Even their blood helped: it carried oxygen in a way that kept working in the cold and reduced heat loss.9PubMed. Substitutions in woolly mammoth hemoglobin confer biochemical properties adaptive for cold tolerance That is how an elephant family that began in Africa could spread into the far north.10PubMed. Substitutions in woolly mammoth hemoglobin confer biochemical properties adaptive for cold tolerance
We know all this from several kinds of evidence. Frozen carcasses in Siberia preserve skin and hair, and people drew mammoths in cave art, so their shape is well recorded. Ancient DNA even lets scientists rebuild proteins, such as the one that carried oxygen in mammoth blood, and test how they worked.
Mammoths lived on a cold grassland scientists call the mammoth steppe, meaning dry, grassy plains.11The World of Elephants – International Congress. Reconstructions of Woolly Mammoth Life History It stretched across Europe, Siberia, and Alaska, with flowering plants other than grasses plentiful among the grass. Grazing herds kept the land open by eating and trampling plants. Nothing quite like it exists today.
Life there meant constant eating. Mammoths ate mostly thin tufts of grasses, which were nutritious but small per bite.12The World of Elephants – International Congress. Reconstructions of Woolly Mammoth Life History A huge body needed a great deal of food, so they likely grazed for much of the day.13The World of Elephants – International Congress. Reconstructions of Woolly Mammoth Life History As the herd cropped a local patch, it had to move on to fresh ground, so the group’s movement followed the food, especially in winter.14The World of Elephants – International Congress. Reconstructions of Woolly Mammoth Life History In summer, broad feet helped them walk on soggy pastures.15Academic Press. Paleoecology of Beringia
Woolly rhinos shared this world. They ranged from Europe to Siberia and Mongolia, in lowlands and river valleys, but avoided steep mountains and deep snow.16Wikipedia. Woolly rhinoceros One rhino from Hungary ate lichens and possibly moss, and it stayed in one area rather than migrating far.17Journal of Quaternary Science. Multi‐disciplinary study of a late Pleistocene woolly rhinoceros found in the Pannonian Basin and implications for the contemporaneous palaeoenvironment
Sabertooth Cats and Dire Wolves
The sabertooth cat Smilodon had a jaw bite only about one-third as strong as a lion’s.18PubMed Central. Supermodeled sabercat, predatory behavior in Smilodon fatalis revealed by high-resolution 3D computer simulation Its skull could not handle struggling prey, so it likely wrestled prey down with powerful forelimbs, then drove its teeth into the neck using strong neck muscles.19PubMed Central. Supermodeled sabercat, predatory behavior in Smilodon fatalis revealed by high-resolution 3D computer simulation20Paleobiology. Behavioral implications of saber-toothed felid morphology Sabertooth species with longer, thinner teeth had sturdier front legs for holding prey.21Paleobiology. Morphological convergence of the prey-killing arsenal of saberooth predators
The teeth were as much a risk as a weapon. Long, narrow, blade-like canines can snap if they hit bone or twist against a struggling animal, which is why the cat needed prey held firmly first. Smilodon was not a tiger, so “sabertooth tiger” is misleading.
Dire wolves looked like gray wolves but split from living dogs and wolves about 5.7 million years ago.22PubMed. Dire wolves were the last of an ancient New World canid lineage They never interbred with gray wolves or coyotes.23PubMed. Dire wolves were the last of an ancient New World canid lineage Their resemblance to gray wolves came from similar lifestyles, not close family ties.24National Park Service. Dire Wolf Horses were an important food, with sloths, bison, and camels eaten less often.25National Park Service. Dire Wolf
Farther north, Ice Age wolves in Alaska and Yukon were genetically different from any wolves alive today.26PubMed. Megafaunal extinctions and the disappearance of a specialized wolf ecomorph Their skulls and worn teeth show they hunted and scavenged giant prey, so this wolf type died out along with the giants it fed on.27PubMed. Megafaunal extinctions and the disappearance of a specialized wolf ecomorph
Not every meat-eater had fur. Huge birds called teratorns soared over the Americas, and they likely scavenged dead giants as condors do.
Cave Bears, Giant Sloths, and Other Oddities
European cave bears appear to have been mostly vegetarian, eating good-quality green plants.28Boreas. Extinction chronology and palaeobiology of the cave bear (Ursus spelaeus) Before winter sleep, though, some ate a mix including meat, insects, seeds, and fruit.29PubMed Central. Predormancy omnivory in European cave bears evidenced by a dental microwear analysis of Ursus spelaeus from Goyet, Belgium Their reliance on plants may have helped doom them when cooling reduced plant food.30PubMed Central. Fate and preservation of the Late Pleistocene cave bears from Niedźwiedzia Cave in Poland, through taphonomy, pathology, and geochemistry
Scientists can tell all this from the animals’ remains. Scratches on teeth show what an animal chewed, and chemicals in bones reveal whether it ate plants or meat.
In South America, Toxodon and Macrauchenia were hoofed animals Darwin found puzzling.31PubMed. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates Proteins from their bones show their nearest living relatives are horses, tapirs, and rhinos.32PubMed. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates Toxodon ate grasses while Macrauchenia ate leafy plants.33Palaeogeography, Palaeoclimatology, Palaeoecology. South American fossil mammals and carbon isotopes: a 25 million-year sequence from the Bolivian Andes
The giant sloth Lestodon stayed in a home range rather than migrating.34PubMed Central. First 87Sr/86Sr isotope data for the extinct sloth Lestodon armatus: insights into the spatial ecology of South American Late Pleistocene megafauna Ground sloths walked on land, unlike the tree sloths of today, and some reached elephant size. Large fruit-eaters like them spread seeds over long distances.35Ecography. Pleistocene megafaunal extinctions and the functional loss of long‐distance seed‐dispersal services
In Australia, Diprotodon still lived on the Darling Downs around 60,000 years ago.36Quaternary International. New ages of the world’s largest-ever marsupial: Diprotodon optatum from Pleistocene Australia Today’s red kangaroos and wallaroos are Australia’s surviving “megafauna,” able to live on poor grasses.37Alcheringa: An Australasian Journal of Palaeontology. An ecophysiological approach to the extinction of large marsupial herbivores in middle and late Pleistocene Australia
Why the Ice Age Giants Died Out
Neither climate nor humans alone can explain the extinctions, because each species responded differently.38Molecular Ecology, Evolution, and Phylogenetics Laboratory. Climate change and humans caused Ice Age extinctions In Eurasia, rapid warming was the main driver for mammoths and rhinos.39PubMed Central. Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia Humans, though, were the main factor for rhinos and horses in some regions, while deer survived both.40PubMed Central. Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia
On Alaska’s North Slope, where people were rare, animal numbers rose and fell with the climate.41PubMed Central. Life and extinction of megafauna in the ice-age Arctic Arctic giants survived by moving between connected grasslands.42PubMed Central. Life and extinction of megafauna in the ice-age Arctic But at the end of the last Ice Age, spreading bogs and rising seas cut those routes for good.43PubMed Central. Life and extinction of megafauna in the ice-age Arctic
Australia’s giants vanished across the continent about 46,000 years ago.44PubMed. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago That timing rules out extreme dryness at the coldest point of the Ice Age as the cause.45PubMed. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago Their large size, which helped them survive earlier climate swings, made them vulnerable to people.46Alcheringa: An Australasian Journal of Palaeontology. An ecophysiological approach to the extinction of large marsupial herbivores in middle and late Pleistocene Australia Large animals breed slowly, so losses are hard to replace, and they need large areas of food.
Some researchers argue for a single “blitzkrieg,” in which humans killed giants quickly after arriving. Australia’s dates can’t yet rule this in or out.47PubMed. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago Most evidence points instead to mixed, local stories.
Did People Hunt Mammoths
At Wally’s Beach in Canada, people butchered seven horses and a camel about 13,300 years ago.48PubMed Central. Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: reassessing the age of Wally’s Beach, Canada Other sites show hunting of mammoths, mastodons, sloths, and elephant relatives, so at least 6 of 36 extinct North American animal groups were hunted.49PubMed Central. Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: reassessing the age of Wally’s Beach, Canada Stone tools in the Carolinas carried blood traces from elephant relatives, horses, and bison.50PubMed Central. Paleoamerican exploitation of extinct megafauna revealed through immunological blood residue and microwear analysis, North and South Carolina, USA
Many of these tools came from the Clovis people, who made distinctive fluted stone spear points and lived across North America about 13,000 years ago. Their tools were used for hunting, butchering, and scraping hides.51PubMed Central. Paleoamerican exploitation of extinct megafauna revealed through immunological blood residue and microwear analysis, North and South Carolina, USA
Clear proof is scarce, because telling hunting from scavenging is hard at most sites.52PaleoAmerica. Sites in the Americas with Possible or Probable Evidence for the Butchering of Proboscideans A site with the bones of one animal and stone tools together is a starting point, but it doesn’t show how the animal died. Cut marks at a few sites show people butchered fresh carcasses before predators did.53PaleoAmerica. Sites in the Americas with Possible or Probable Evidence for the Butchering of Proboscideans Bones with spear tips still embedded are the clearest evidence, and they are very rare.54PaleoAmerica. Sites in the Americas with Possible or Probable Evidence for the Butchering of Proboscideans
Ice Age Animals Still Alive Today
Reindeer and musk oxen still share Arctic lands they roamed with mammoths.55PubMed. Extinction of large herbivore mammals: niche characteristics of musk ox Ovibos moschatus and reindeer Rangifer tarandus coexisting in isolation On Wrangel Island, when musk ox numbers rise, reindeer numbers fall.56PubMed. Extinction of large herbivore mammals: niche characteristics of musk ox Ovibos moschatus and reindeer Rangifer tarandus coexisting in isolation Deer came through both warming and human pressure.57PubMed Central. Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia Arctic seals and whales shifted south during cold periods and survived.58PubMed. The evolution of Arctic marine mammals You can still see Ice Age survivors today: musk oxen in Alaska, Greenland, and northern Canada, bison and pronghorn in North American parks, and red kangaroos across inland Australia.
Mammoths lasted longest on Wrangel Island, an island off Siberia. That small, isolated group built up genetic defects.59PubMed Central. Excess of genomic defects in a woolly mammoth on Wrangel island
How Losing the Giants Changed the Land
Without giant grazers, uneaten plants built up and fires became more frequent in many places.60PubMed Central. Ecological consequences of Late Quaternary extinctions of megafauna Fire in turn changed which plants thrived, and plant communities and whole landscapes shifted.61PubMed. Ecological impacts of the late Quaternary megaherbivore extinctions
Seeds traveled less, too. In South America, long-distance seed spreading shrank by at least two-thirds.62Ecography. Pleistocene megafaunal extinctions and the functional loss of long‐distance seed‐dispersal services About 6% of land mammals died out, but over half of mammal food-web links vanished.63Rice News. Reconstructing ice age diets reveals unraveling web of life