Hominids diverged from the chimp branch of the family tree roughly six million years ago, producing a series of evolutionary dead-ends before the ultimately successful genus Homo emerged. H. neanderthalensis and H. sapiens grew out of the same line at different times.

The Neanderthals' ancestors diverged first, and they left Africa a couple of hundred thousand years ahead of ours. Homo sapiens arrived in Europe about 50,000 years ago. The two species overlapped for perhaps 20,000 years before the Neanderthals went extinct. Scientists still aren't sure why.