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

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 ...

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.) Imagine a sloth. You probably picture a medium-size, tree-dwelling creature hanging ...