Why giant sloths got so big—and went extinct

Today, just six species of sloth remain, split between two families: two-toed and three-toed. But in prehistoric times, sloths were far more diverse—and some were massive compared to the tree-dwellers we know now. If you’ve been to the Natural History Museum in London, you might have seen the striking replica skeleton* of Megatherium americanum , one of these ancient giants. New research from a team of scientists from the Americas sheds light on how these now-extinct sloths reached such impressive sizes—and why they eventually vanished. Bigger sloths, grounded lives Unlike modern sloths, which live exclusively in trees, the largest prehistoric species were ground-dwellers. Some were tall enough to pull leaves from treetops while standing upright. Megatherium , for example, lived in the grasslands of South America until about 10,000 years ago. Fossil footprints from Argentina suggest it walked on hind legs, using its tail for balance. The scientists analyzed ancient DNA and more th...