Sloths weren't always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge—up to 4 tons (3.6 metric tons)—and when startled, they brandished immense claws.

For a long time, the common wisdom is that megafauna died out soon after humans arrived in the Americas. If humans have been in the Americas for much longer than thought, and co-existed with megafauna for millennia, then that narrative is wrong. It’s a projection of modern humans’ faults onto ancient humans. Moreover, it shows that there is nothing inevitable about human-caused extinctions. Humans are not a virus, Agent Smith.