Many of us learned in high school that our human ancestors first evolved in Africa before slowly spreading out across the planet. But that may not be the full story.
New research published in Nature in May aimed to shed new light on human origins in Africa and beyond. An international research team using sophisticated computer software and a large set of genomic data — including DNA from many different populations in Africa — tested a variety of models for how human populations arose and diverged, producing the genetic variation we see on the African continent today.
The best-fitting model they found may well force changes in the story taught about human evolution.
The new model begins at the Middle Pleistocene, approximately one million years ago, when there were not one but two main populations of humans. But instead of developing completely separately, gene flow continued between the groups over time. In place of a tree, we see a pattern of diversion from migration and reconnection through interbreeding, a bit like the veins in a leaf. Two distinct veins (or stems 1 and 2) remained weakly genetically connected through tens of thousands of years.
