A team of scientists has tracked down a genetic mutation that leads to blue eyes. The mutation occurred between 6,000 and 10,000 years ago. Before then ,there were no blue eyes. The mutation affected the so-called OCA2 gene, which is involved in the production of melanin, the pigment that gives color to our hair, eyes and skin.

"From this we can conclude that all blue-eyed individuals are linked to the same ancestor," said Hans Eiberg, who is from the Department of Cellular and Molecular Medicine at the University of Copenhagen. "They have all inherited the same switch at exactly the same spot in their DNA." Eiberg and his colleagues detailed their study in the Jan. 3 online edition of the Human Genetics.

That genetic switch somehow spread throughout Europe and now other parts of the world. "The question really is, why did we go from having nobody on Earth with blue eyes 10,000 years ago to having 20 or 40 percent of Europeans having blue eyes now?" said John Hawks from the University of Wisconsin-Madison. "The gene does something good for people. It makes them have more kids."

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