The Speculist: The Blue-Eyed Variation

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The Blue-Eyed Variation

I have green eyes, while my parents and all my siblings have blue eyes. I always thought that my eye color was the same as theirs, just tinted slightly differently. But the way I read this story, that is simply not the case:

ALL BLUE-eyed people can be traced back to one ancestor who lived near the Black Sea 10,000 years ago.

Human beings had brown eyes until a single mutation in a gene called OCA2 arose by chance in one individual, Professor Hans Eiberg from the University of Copenhagen said.

The mutation "turned off" the mechanism that produces brown melanin pigment and "diluted" brown eyes to blue.
Most likely occurring in the north-west part of the Black Sea between 6000 and 10,000 years ago, the gene was dispersed in the rapid waves of migration to northern Europe that followed the end of the last ice age.

Professor Eiberg said the finding, published in the journal Human Genetics, helped to explain why Europeans were far more likely to have blue eyes than any other ethnic grouping.

Europeans also had a far greater range of skin tones and hair colours living in the one community than the rest of the world, where people are almost uniformly dark-haired and dark-eyed.

The researchers examined mitochondrial DNA and compared the eye colour of blue-eyed people in countries as diverse as Jordan, Denmark and Turkey.

Variation in the eye colour from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes.

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

So it seems that my green eyes are actually a slight variation on the original human eye color -- brown -- while the rest of my family have this much newer trait that only showed up 500 generations or so ago.

Not that it matters, of course, it's just interesting. It has been established that there is a mitochondrial Eve who is the ancestor of every human being alive on the planet. That is, we all inherited the unique mitochondria that she carried. Variations on that trait have been eliminated from the species.

So maybe there a was blue-eyed Eve? (or Adam?) The mitochondrial Eve lived some 130,000 years before the blue-eyed ancestor. It's possible that that individual, too, is a common ancestor for much of the world's population. But since blue eyes are a recessive gene, many of the blue-eyed ancestor's descendant's (like me) don't have blue eyes.

Comments

You go back a thousand years... any person living at that time who has decendents living today is probably your ancestor.

Muhammed is a good example of this. Most Europeans can, with some basis, argue that they are decended from Muhammed.

I'm not sure why this matters.

But I agree that it is somehow interesting.
I'm just not sure why.

If it has any significance at all, it is as an example of human evolution in action. Blue eyes show up in one individual and 10,000 years later, a significant (if relatively small) percentage of the population is "infected" with the new trait.

One thing I don't get, though. If blue eyes are recessive, how could they have ever spread?

don't worry..this theory is not true

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