Giant sloths and mastodons lived with humans for millennia, research suggests

An illustration depicting a person carving an osteoderm from a giant sloth in Brazil about 25,000 to 27,000 years ago (Julia d’Oliveira via AP)

Sloths were not always slow-moving, furry tree-dwellers. Their prehistoric ancestors were huge — up to four tonnes — and when startled, they brandished immense claws.

For a long time, scientists believed the first humans to arrive in the Americas soon killed off these giant ground sloths through hunting, along with many other massive animals such as mastodons, sabre-toothed cats and dire wolves that once roamed North and South America.