The story of human migration from Africa into the rest of the world is the original story of exploration. Those first people who walked out of Africa and into the vast unpopulated world told their story of exploration on rock and cave walls as they went. The timeline for that tale has been refined by looking at the DNA our ancestors left behind (more on that in another post). But that same DNA is also showing that the human migration is not as straightforward as we once believed.
Prevailing evidence is that modern humans expanded out from Africa between 70,000 and 50,000 BP. Our ancestors encountered and replaced dwindling Neanderthal populations in Europe.
However, some Neanderthal lives on in us. With the exception of native Africans, most people have up to 2% Neanderthal DNA.
That story got a bit more muddled this month. A study published in Nature Communications -summarized nicely in the NYT here- suggests that there was a "flow" of genetic material into Neanderthal populations from Africa before 100,000 years ago. That means that humans, or something very similar to us, entered Europe and interbred with Neanderthals leaving a slight genetic trace in Neaderthal DNA.