People with blue eyes have a single, common ancestor, according to new research.
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.
"Originally, we all had brown eyes," said Hans Eiberg from the Department of Cellular and Molecular Medicine at the University of Copenhagen.


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.
"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," Eiberg said.
The genetic switch is located in the gene adjacent to OCA2 and rather than completely turning off the gene, the switch limits its action, which reduces the production of melanin in the iris. In effect, the turned-down switch diluted brown eyes to blue.
If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism.
"It's exactly what I sort of expected to see from what we know about selection around this area," said John Hawks of the University of Wisconsin-Madison, referring to the study results regarding the OCA2 gene. Hawks was not involved in the current study.
Baby blues
Eiberg and his team examined DNA from mitochondria, the cells' energy-making structures, of blue-eyed individuals in countries including Jordan, Denmark and Turkey. This genetic material comes from females, so it can trace maternal lineages.
They specifically looked at sequences of DNA on the OCA2 gene and the genetic mutation associated with turning down melanin production.
Over the course of several generations, segments of ancestral DNA get shuffled so that individuals have varying sequences. Some of these segments, however, that haven't been reshuffled are called haplotypes. If a group of individuals shares long haplotypes, that means the sequence arose relatively recently in our human ancestors. The DNA sequence didn't have enough time to get mixed up.
"What they were able to show is that the people who have blue eyes in Denmark, as far as Jordan, these people all have this same haplotype, they all have exactly the same gene changes that are all linked to this one mutation that makes eyes blue," Hawks said in a telephone interview.
Melanin switch
The mutation is what regulates the OCA2 switch for melanin production. And depending on the amount of melanin in the iris, a person can end up with eye color ranging from brown to green. Brown-eyed individuals have considerable individual variation in the area of their DNA that controls melanin production. But they found that blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. 
"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 toldLiveScience, 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." Eiberg and his colleagues detailed their study in the Jan. 3 online edition of the journal 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?" Hawks said. "This gene does something good for people. It makes them have more kids."



               Genetic Mutation

10 comments:

  1. So is there any sort of CAUSE behind this mutation? What spurred the human body to act such a way?

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    1. Well, that's what a mutation is; it is a completely random event.

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    2. It wouldn't have had a cause, but it would have become a surviving trait for certain reasons probably. There has been research that show's people with lighter colored eyes are more receptive to light, perhaps this helped in hunting in darker area's or the world? The evidence on the topic though is circumstantial at best and most studies find that eye color has little effect on your ability to see in the end.

      Side note though, this boy in china developed a blue eye mutation which allow's him to see better in the dark, but not night vision as was initially implied by the video.
      http://www.youtube.com/watch?v=Xfs0R-7cS_s

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    3. I wouldnt say more receptive to light, you just get a lot of glare during the day making it difficult to go out without sunnies

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    4. It could be anything. A stray cosmic ray striking that gene; a DNA replication error. The important thing is whether or not the change helped the organism survive and procreate.

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    5. It could be like with blonde hair: a random mutation that has no direct benefit for survival, but helps a person to stick out of the crowd and attract a mate.

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  2. Well, how sexy would the only person with blue eyes have been in a world of brown eyes. They simply would have been more desirable and therefore able to procreate more

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  3. I KNew IT!!!! I'm a Mutant! Time to get the X-Men together

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  4. As a blue eyed individual...I think the first blue eyed baby's were probably killed by the parents or exiled from the tribe .... freakishly different in primitive cultures couldn't be good for their health. ...

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    Replies
    1. I thought almost all children have blue eyes when born. They only turn brown later on.

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