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 ...

Sloths appear defenseless, slow, and vulnerable in ecosystems filled with predators. Yet despite these disadvantages, they persist in environments where speed usually determines survival. Scientists ...