Every person on the planet born with blue eyes shares the same genetic mutation inherited from a single human ancestor.
Danish researchers concluded a decade-long study which found that all blue-eyed people display a trait given to them by someone who lived 6,000 to 10,000 years ago.
“Originally, we all had brown eyes,” Professor Hans Eiberg of the University of Copenhagen said of his study. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a ‘switch,’ which literally ‘turned off’ the ability to produce brown eyes.”
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The so-called OCA2 gene is responsible for the production of melanin, the pigment that gives colour to our hair, eyes and skin. Eiberg says that blue eyes are not really a color as much as it is a lack of color. More of the mutation and the person is an albino.
Eiberg’s study analysed 155 individuals in a large Danish family, as well as several blue-eyed people born in Turkey and Jordan.
It found all the blue-eyed subjects shared the genetic mutation, with little deviation on genes neighbouring it on the chromosome, meaning the ‘switch’ in the common ancestor is relatively recent by evolutionary standards.
The Danish study makes an educated guess to figure that the mutation took place on the northern of the Black Sea around the Neolithic era. The first blue-eyed humans are thought to be among the proto-Indo-Europeans who spread agriculture into western Europe and eventually rode horses into Iran and India.
When Eiberg announced the findings of his study a few years ago he said that the genetic variation is “neither a positive nor a negative mutation.” Just like hair colour, baldness, freckles and beauty spots, this mutation doesn’t really increase nor reduce a human’s chance of survival.
Blue eyes are a recessive trait so ironically, neither the first person to have the mutation, nor his or her children, would have had blue eyes themselves. The gene would have had to have come from both parents so it would have had to be passed on for a while before a couple met and had a child – but maybe not that long because cousin-cousin relations wasn’t that big of a deal back then.
