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Zidbits – Learn something new everyday! | October 24, 2014

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Where Do Blue Eyes Come From?

Where Do Blue Eyes Come From?

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

Comments

  1. Well, this isn’t so mindblowing to me. All evolutionary traits start with a single mutation in one being. I can’t imagine it being any other way.

    • Well, not every trait can be traced back to beginning in the last 10000 years! Thats evolution in action.

  2. Lord Zed

    What about green eyes?

    • Jill

      I read that green and hazel eyes are a dilution of brown pigment, so green eyes have always been with us, I guess!

  3. People with green eyes are descended from gods and immortal heroes.

  4. brown eyes

    So that means I can make my eyes turn blue just by switching off a gene?

    • TiagoTiago

      Hmm, I don’t think it works that way; your eye is already formed. Though I guess it might gradually lighten up over many years as the cells renew…

  5. Charles P. Johnson

    I have blues eyes and my left has a brown spot too.

  6. grummbunger

    lol “Everyone had brown eyes up till that point” and about other colors like hazel that are not blue? is this a real study?

  7. Bill

    The adaptation of blue eyes no doubt is due to people living in the darkness of caves. No need for melanin in a cave. This is the same for lighter skin.

  8. steve schulte

    So was the ‘single person’ with the mutation a man or woman? I would guess it was a man that got the mutation as a woman could only pass the mutation on to her own limited number of children and none of those would express the blue eyed trait– whereas a man (having this unusual attractive? sexually desirable?) eye color might find himself in demand for a lot of free love and disseminate this gene in a great number of offspring – all of which would not show the blue eyes – but if they matched up with a fellow descendant of person zero at a later date who also carried the recessive, then POW! We get blue eyes. Also, to have this mutation become so prevalent so quickly means that it was a probable Casanova who lucked out in the beginning. Two cheers for cosmic radiation bombarding our poor guys swimmers!

  9. LadyBelle

    There are only blue eyes and brown eyes. Green, hazel, and violet are all variations based on a series of 3 switches that control tint. That is why in grade school biology you learn BB, Bb, and bb. In Bio 101 at college, you get more in-depth about the various switches and controls.

    The more interesting fact is that the blue gene is so prevalent. This would mean that the original mutation wasn’t so bizarre that it limited mating potential or even caused shunning from the family group as an infant. Not only was the first mutation accepted, but future mutants were accepted and bred freely.

  10. Tyler

    So the movie 10,000 BC is fake? I knew it because she has blue eyes and that was 12,000 years ago…

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