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

An Ice Age giant was tumbling around North America during the Late Pleistocene. About the size of a bear, it was actually a kind of enormous sloth that had evolved to thrive in freezing conditions.

(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 ...