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Frank Sinatra, Stephen Hawking, Marie Curie and Stephen
Fry all owe their blue eyes to a genetic mutation that likely occurred
between 6,000 and 10,000 years ago, researchers say.
Scientists
believe they have tracked down the cause of the eye color of all blue-eyed
humans on the planet today.
“Originally, we all had brown eyes”,
said Professor Hans Eiberg from the University of Copenhagen,
who led the team.
Blue eye color most likely originated from the near east
area or northwest part of the Black Sea region, where the great agriculture
migration to the northern part of Europe
took place in the Neolithic periods about six–10,000 years ago.
“That is my best guess,” he said. “It could be the northern part of Afghanistan.”
The mutation affected a gene called OCA2 and
“literally 'turned off' the ability to produce brown eyes”, he says. OCA2
is involved in the production of melanin, the pigment that gives color to
hair, eyes and skin.
The mutation in the adjacent gene does not switch off the OCA gene entirely
but limits its action, reducing the production of melanin in the iris of the
eye – “diluting” brown eyes to blue.
If the OCA2 gene had been completely turned off, those who inherited this
mutation would be without melanin in their hair, eyes or skin color - albino.
For the study, Professor Eiberg’s team examined DNA in blue-eyed individuals
in countries as diverse as Jordan,
India, Denmark and Turkey.
His findings are the latest in a decade of genetic research, which began in
1996, when Professor Eiberg first implicated the OCA2 gene as being one of
those responsible for eye color.
“They have all inherited the same
switch at exactly the same spot in their DNA. From this we can conclude that
all blue-eyed individuals are linked to the same ancestor,” said
Professor Eiberg, who reports the work in The
American Journal of Human Genetics.
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