Not long ago, the story was simple. A vanguard of modern humans left their African birthplace 50,000–60,000 years ago and quickly conquered Asia. They turned left into Europe some 40,000 years ago, later crossing the Bering Strait and marching southward into the Americas. With their advance, Neanderthals and other earlier peoples dwindled and vanished.
But in the past five years, the picture has grown more complex — and more interesting.