Scientists have analyzed ancient DNA and compared more than 400 fossils from 17 natural history museums to figure out how and why extinct sloths got so big.

A cooling, drying climate turned sloths into giants – before humans potentially drove the huge animals to extinction. Today’s sloths are small, famously sluggish herbivores that move through ...

Ancient sloths ranged in size from tiny climbers to ground-dwelling giants. Now, researchers report this body size diversity was largely shaped by sloths’ habitats, and that these animals ...

This evidence of an interaction between human and extinct giant sloth is "unique in the world," Belvedere said. The tracks led the scientists to a site that suggests confrontation.

Sloth in prison -- The Great Basin now and then -- A zoologically impoverished world -- Dating an ass -- A stable of ground sloths -- Extinct mammals, dangerous plants, and the early peoples of the ...

A fossil of the extinct ground sloth, Megalonyx jeffersonii, was found in Ellis County, Kansas, offering new insight into its presence in the Great Plains.

A fossil of the extinct ground sloth, Megalonyx jeffersonii, was found in Ellis County, Kansas, offering new insight into its presence in the Great Plains.

Sloths have a reputation for being sluggish and slow, spending most of their lives dozing in trees, but a new study suggests this is one of the enduring secrets of their success.

A fossil of the extinct ground sloth, Megalonyx jeffersonii, was found in Ellis County, Kansas, offering new insight into its presence in the Great Plains.

A fossil of the extinct ground sloth, Megalonyx jeffersonii, was found in Ellis County, Kansas, offering new insight into its presence in the Great Plains.

A fossil of the extinct ground sloth, Megalonyx jeffersonii, was found in Ellis County, Kansas, offering new insight into its presence in the Great Plains.