Sloths weren’t always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge — up to 4 tons (3.6 metric tons ...

Sloths weren’t always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge — up to 4 tons — and when ...

And because the fossil record shows the widespread decline of American megafauna starting around the same time — with North America losing 70% of its large mammals, and South America losing more ...