What 35 million years of evolution reveal about resilience, extinction, and the role of humans.

In the Amazon rainforests in the country of Colombia, there is a place called Serranía La Lindosa, with rock cliffs decorated in ancient drawings. There are thousands of paintings covering 12 kilometers (8 miles) of rock in an area that has been largely inaccessible.

Sloths these days are small, tree-dwelling animals that live high up in the rainforest canopy and do a good imitation of the plants they eat. They’re slow, they’re green, and they can’t jump—but a new study published in the journal Scientific Reports suggests their ancestors weren’t the strict vegetarians their reputation would have us believe.