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.

Harlan’s ground sloth fossil skeleton excavated and displayed at the La Brea Tar Pits in Los Angeles. Larisa DeSantis Imagine a sloth. You probably picture a medium-size, tree-dwelling creature ...