Pierre Andrieu—AFP/Getty ImagesA model representing a Neanderthal man on display at the National Museum of Prehistory in Dordogne, France in 2008.

They don't have any descendants still living

Neanderthals and humans may be different species, but that doesn’t mean they didn’t occasionally mate. New research shows that Neanderthals and modern humans may have interbred tens of thousands of years earlier than previously thought.