Long before today’s tree-dwelling sloths, a 4-ton giant roamed South America — and it may have stood and fought like a bear.

Long before modern sloths became slow-moving tree dwellers, their ancestors were enormous ground beasts. These ancient sloths stood as tall as elephants and weighed several tons. Fossil evidence shows ...

Sloths appear to have life figured out, and once the details are revealed, being envious makes sense. These tree-dwelling mammals have survived for millions of years by doing things their own way, and ...