OUR direct ancestors may have found their way out of Africa much earlier than we think. As new fossil remains emerge from China and south-east Asia, the traditional story of how we left Africa is being challenged.
The accepted view is that Homo sapiens evolved in Africa 200,000 years ago and stayed there until 60,000 years ago, when they struck out through the Middle East and spread around the world. Any older hominin bones found outside Africa are deemed dead ends. So although the more primitive Homo erectus made it all the way to Indonesia, and probably gave rise to the Neanderthals and the Denisovans, all of these lines eventually died out. Our own species evolved solely in Africa.
The evidence for this comes partly from dating bones to specific periods, but also from genetics. As you move further away from Africa, across Asia and then the Americas, the genetic diversity of indigenous populations drops. This implies that the source population was in Africa and gradually lost diversity as it expanded. The genetics suggest that human genes went through this bottleneck 60,000 years ago.
The "out of Africa at 60,000 years ago" scenario remains the majority view. But the orthodoxy is slowly being challenged as ancient bones are uncovered in the east. As yet, though, they remain few and far between.
newscientist
