Why Did The Mammals of The Ice Age Die Off?

Ever since we started finding their fossils in the ground, humans have been fascinated by the strange and interesting-looking animals of the past. We now know that humans coexisted with several large, hairy animals, well-adapted to the cold weather of the last ice age. Where did they all go, anyway?

What’s an ice age?

Technically, we’re still in what is known as the Quaternary Glaciation period, or ice age! However, for the last 10,000 years or so, the ice age has been in remission — what’s technically known as an “interglacial” period. Still, we have ice caps at both poles, and ice sheets in places like Greenland. Climatologists say glaciers define an ice age (as opposed to a “greenhouse period”, where there are no glaciers anywhere on the planet.)

Famous animals of the last ice age

The last glacial period is famous today for some very photogenic mammals. Most of us are familiar with “megafauna”, or very large herbivores, such as the wooly mammoth and mastodons, and the giant sloths. There were also fearsome predators such as saber-toothed tigers, giant hyaenas, cave lions, and a kind of wolf called Andrewsarchus. Lesser-known megafauna like the wooly rhino Elasmotherium, Glyptodon (a giant armadillo), and the elephant-like Gomphotherium were also quite striking in appearance.

Possible extinction reasons

So, why don’t we see all these cool animals running around today? About 10,000 years ago, something called the Quaternary extinction event took place, and most of these mammals died out. The exact reasons aren’t clear, but we have some ideas:

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  • Climate change: As the ice age ended and the temperature rose, it may have just been too warm for these shaggy critters to compete with other animals. Smaller and shorter-haired mammals probably didn’t mind the heat so much.
  • Overkill: Humans may have quite simply hunted a lot of the megafauna to death. Extinction evidence almost always coincides directly with the introduction of early humans to those areas of the world, and fossils often show arrowheads and spear points embedded in the bones of fallen mammoths and other herbivores.
  • Competition with humans: Carnivores like the smilodons, cave lions, and wolf-like predators had to hunt more successfully than humans if they were to survive — and humans turned out to be very, very good at hunting. We may have driven some of these animals out of the picture by eating their food supplies ourselves.
  • Hyperdisease: A less common theory is that as humans spread around the world (and brought their livestock and pets with them), they may have spread new, strange diseases into areas that had never seen those germs before, and infected animals whose immune systems were not prepared to adapt.
  • Dwarfism: Humans may have “selected” for smaller forms of all of these animals. It’s only natural for us to go after the biggest sources of meat first — if early humans were always targeting the largest animals for dinner, the smaller ones would evolve to become more common and eventually become new species.

There have been a lot of ideas about the Quaternary extinction, but some of them aren’t popular anymore — for instance, scientists used to believe that saber-toothed tigers just weren’t very good at hunting compared to faster lions and tigers. Today we’ve decided the most likely causes are the high temperatures and the introduction of human beings around the world, but there’s still room for more evidence to change our minds again.