In part 2 of our special series on human ancestry, we ask why we are the only surviving branch on the human evolutionary tree. Just 50,000-100,000 years ago, Earth was home to three or four separate human species, including our most famous cousins: the Neanderthals. New research has shown that Neanderthals were not the brutish, unintelligent cavemen that cartoons make them out to be. They were creative, smart, social, and perhaps even had complex language. So why did they go extinct as soon as Homo sapiens moved into their territory? Does any trace of them live on today? Why don’t we have Neanderthal neighbors?