Got Blue Eyes? Congratulations, You’re Related to Brad Pitt!
Posted Nov 19 2009 10:02pm
…and Frank Sinatra, and Bill Clinton, and (insert your favorite famous blue-eyed person here). The Danish geneticist, Hans Eiberg, who pioneered research into understanding the genetics of eye color, now traces all blue-eyed people back to a common ancestor who lived 6,000 to 10,000 years ago, perhaps around the Black Sea near the Ukraine or Turkey.
About 10 years ago, Eiberg discovered the gene OC2, which helps determine your eye color. Now he’s discovered a mutation that “switches off” this gene, ultimately resulting in blue eyes. Because the mutation is extremely specific, all people with blue eyes have the exact same genetic variation, and anyone with brown or green eyes do not. As a result, says Eiberg said, the mutation must have come from a single ancestor. “It’s not a guess,” he says. “It has to be.”
The mutation limits the OCA2 gene, restricting production of melanin in the eye. The result: The eye’s brown color is diluted, giving people with the mutation pure blue eyes. (Shutting melanin production down entirely would result in albinism, affecting hair and skin color as well.)
People without the off-switch, on the other hand, have eye color ranging from deep brown to blue flecked with brown. (Green-eyed people can thank an entirely different part of the genome for their pretty peepers.)