Sunday, September 30, 2012
When did the ancestors of modern Europeans lose their dark skin?
Researchers studied three genes associated with lighter skin pigmentation. Although the genes are found in all human populations, they are far more common in Europe than in Africa, and explain a significant portion of the skin-color differences between European and west African populations. By analyzing the genomes of 50 people with European ancestry and 70 people with sub-Saharan African ancestry, the scientists could estimate when the three genes – and pale skin – first became widespread in European populations. The result suggested that the three genes associated with paler skin swept through the European population only 11,000 to 19,000 years ago. An earlier analysis of ancient DNA in 40,000 and 50,000-year-old Neanderthal bones, respectively from Spain and Italy, suggested that our extinct cousins had light-coloured skin and reddish hair in their European heartland. But the Neanderthals went extinct around 28,000 years ago – long before modern humans in Europe gained a pale skin. Evidently Neanderthals did not pass these useful local adaptations on to modern humans, despite genetic evidence that the two species interbred. That might seem unusual given that the two species lived cheek-by-jowl in Europe for several thousand years. But it makes sense if the interbreeding evident in the genes occurred in the Middle East, where modern humans and Neanderthals first met, says Chris Stringer at the Natural History Museum, London. In that region, Neanderthals may have had darker skins, explaining why our species did not gain a pale skin after interbreeding with them. Indeed, a study earlier in 2012 of ancient DNA suggested that Neanderthals living in what is now Croatia had dark skin and brown hair.