Not so very long ago, the Americas were home to giant mammals: monstrous-sized beavers, ground sloths weighing over 4,000 pounds, the well-known woolly mammoths and saber-tooth cats, and many more.
These megafauna, which is ancient Greek for “large animals,” thrived in the geological period called the Pleistocene epoch, which spans 1.8 million to 12,000 years ago. (For perspective, most of the dinosaurs went extinct around 65 million years ago.) The Pleistocene era ended with the end of the last ice age, along with the sudden extinction of most of the American megafauna.
Although it’s unclear what’s responsible for the mass extinctions, two main factors are suspected: dramatic climate change at the end of the ice age and arrival of humans.