Scientists track down the genetic mutation that gives humans blue eyes.

Research completed in 2008 showed that every person with blue eyes shares a single ancestor who lived between 6,000 and 10,000 years ago.

“Everyone had brown eyes up till that point”, said Hans Eiberg from the University of Copenhagen. He and his colleagues showed that a mutation in the OCA2 gene reduced melanin production.

Enter Blue-Eyed Eve

They discovered that the mutation arose in a single individual in the Near East 6,000–10,000 years ago during the neolithic period. This genetic mutation resulted in the creation of a switch, which “turned off” the ability to produce brown eyes.

The switch’s effect on OCA2 is quite specific. If the OCA2 gene had been completely destroyed or turned off, humans would not have melanin in their hair, eyes or skin color. Also known as albinism.

“Out of 800 persons we have only found one person which didn’t fit — but his eye color was blue with a single brown spot,” Eiberg said in an interview, referring to the finding that blue-eyed individuals all had the same sequence of DNA linked with melanin production.

“From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” Eiberg said. “They have all inherited the same switch at exactly the same spot in their DNA.”

Image Credit: Foxnews

Reference:

Journal of Human Genetics Vol 123. Ie 2, pg. 177-87

