WASHINGTON – Scientists said Thursday they have found a genetic mutation that largely explains the appearance of white skin in humans tens of thousands of years ago. The finding helps solve one of biology’s most enduring mysteries.
The work suggests that the skin mutation occurred in a single individual after the first human exodus from Africa, when all people had brown skin. That person’s offspring apparently thrived as humans moved northward into what is now Europe, helping to give rise to light-skinned people.
Leaders of the study at Penn State University warned against interpreting the finding as a discovery of “the race gene.” Race is a vaguely defined biological, social and political concept, they noted.
In fact, several scientists said, the new work shows just how tiny a biological difference caused the change in skin color. The newly found mutation involves a change of just one letter of DNA code out of the 3.1 billion letters in the human genome.
“It’s a major finding in a very sensitive area,” said Stephen Oppenheimer, an expert in anthropological genetics at Oxford University who was not involved in the work. “Almost all the differences used to differentiate populations from around the world really are skin deep.”
The work raises new questions, not least of which is why white skin became so prevalent in northern climes. Some scientists suggest that light skin offered a survival advantage for people who migrated out of Africa by boosting their levels of bone-strengthening vitamin D; others have posited that its novelty simply made it more attractive to those seeking mates.
The work also reveals for the first time that Asians owe their relatively light skin to different mutations. That means light skin arose independently at least twice in human evolution, in each case affecting populations with the facial and other traits that today are commonly regarded as the hallmarks of Caucasian and Asian races.
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