Everyone knows that humans came out of Africa, but until recently nobody knew that they came in at least two major waves of migration, about 600,000 and 95,000 years ago. The finding comes from a major analysis of newly derived human genetic trees, published today in Nature.
More than that, the analysis, by Alan Templeton, of Washington University in St Louis, Mo., suggests that the migrations were not bloodthirsty "replacement events," when a new population wipes out an existing one and results in its complete genetic extinction. Instead, the early migrant humans interbred with the populations they encountered, almost as if they followed a principle of "make love, not war."
In his efforts to reconstruct the movement and history of the early human migrants, Templeton gathered evidence from many different populations and many different genes. This was a thoroughly modern study of human origins and history -- relying on DNA rather than the shape of old bones.