People With Blue Eyes May All Be Related

[Kor37 9]

People With Blue Eyes May All Be Related

By Elizabeth Weise,USA Today

Posted: 2008-02-06 19:37:14

Filed Under: Science News

 

If you have blue eyes, you may be related to every other blue-eyed person in the world.

 

Researchers in Denmark have found that every person with blue eyes descends from just one "founder," an ancestor whose genes mutated 6,000 to 10,000 years ago. Before then, everyone had brown eyes.

 

Lead scientist Hans Eiberg, a geneticist at Copenhagen University, began in 1973 to study a Danish father with 17 children who carried the gene for both blue and brown eyes. Over time, researchers were able to trace the blue-eyed trait to one specific area near a gene called OCA2. The paper appears in the journal Human Genetics.

 

Eiberg's team then tested 155 blue-eyed people from Scandinavia, Turkey, Jordan and India, looking to see whether they, too, had similar DNA sequences on that gene. To their amazement, they found that each individual had identical DNA sequences in that region of that gene, an indication that the original mutation happened recently enough that it hasn't had time to change.

 

Everyone has two genes for eye color, one from their father and one from their mother. Brown eyes are dominant, so even if someone has one blue and one brown-eye gene, he'll still have brown eyes.

 

That means that the recessive genes for blue eyes can be invisible for generations, with blue-eyed children popping up only when both parents carry at least one blue-eye gene, Eiberg says.

 

Blue eyes are actually what happens when the human default - brown eyes - is turned off. Brown eyes are caused by the pigment melanin, which also gives color to hair and skin, building up in the eyes. It's why many light-skinned babies are born with blue eyes but gradually develop brown eyes as their body produces melanin in their irises. The blue-eye mutation turned off the gene that produces melanin in the eyes.

 

When the original mutation occurred, the person who carried it would still have had brown eyes, says Eiberg. But in the generations that followed, a man and a woman who each had one blue-eye gene mated, producing the world's first blue-eyed baby.

 

Imagine what a surprise that was, Eiberg notes. "If the child was the only one to have blue eye color and everyone else has brown, it could have been very interesting.

 

That one mutation now exists in an estimated 300 million people, Eiberg says. Why it has become so common in some populations is unknown. It has been suggested that blue eyes and the lighter coloring that often accompanies them might have given an advantage to people in colder climates because they could absorb more vitamin D from the sun. Others have suggested it's simply a roll of the historical dice, with the original group that had the blue-eye genes coming through a genetic bottleneck.

 

"Maybe the population almost went extinct. If just a few individuals survived at some point and they were blue-eyed," then it could have happened much more recently, says Klaus Kjaer, a geneticist at the University of Copenhagen who also worked on the paper.

 

Blue eyes, though somewhat rare in the USA, are common in countries near the mutation epicenter, which previous researchers have pinpointed as probably somewhere in the Balkans or near the Black Sea.

 

In Estonia, 99% of people have blue eyes, Eiberg says. In Denmark 30 years ago, only 8% of the population had brown eyes, though through immigration, today that number is about 11%. In Germany, about 75% have blue eyes.

 

Because the research shows that all blue-eyed people are related, Kjaer notes it's "interesting" that his blue-eyed wife is therefore related to Brad Pitt.

 

Wow.......... <_<

Edited February 7, 2008 by Kor37

[RikerChick 5]

My husband and daughter both have bright blue eyes. My son and I both have green eyes. Now I want to know where green eyes came from. Actually, my parents and siblings all have blue or green eyes too. No brown eyes in our family.

[Stephen of Borg 2]

same here, my mom and brother have blue eyes. My dad and I have green

[star_rose 0]

My father has green eyes, my mother has brown eyes. When I was a baby, I had blue eyes, but after one year and half they became brown with a reflex green. Now I have brown eyes, but in certain days my eyes change and assume a greenish reflex...

What am I? An alien?

[Stephen of Borg 2]

my family has been talking about this article all day since we have so many blue eye people in the family, which does have German ancestry. Very interesting <_<

[trekz 7]

This article is fascinating <_< I would like to see the statistics for Ireland and England. I have some German ancestry but most relatives that I recall had brown eyes. I would also like to hear more about the significance of green eyes.

[Theunicornhunter 2]

My eyes switched from blue to green after I was an adult. So, I really don't know where that puts me - other than my irises started producing more melanin.

 

Supposedly green is a rare eye color - I never thought of blue eyes as rare. While I have German ancestors on both sides of the family - there's also some Cherokee on my mother's side of the family but you'd never know it - I was blue-eyed and blonde through early adulthood. This article makes me miss my blue eyes.

[Kor37 9]

This article makes me miss my blue eyes.

 

You just want to be related to Brad Pitt....... <_<

[Wishfire 2]

If all blue eyes are cause by the same gene sequence, how does that account for variations withing the blue-eye population? I mean, I've met people with eyes so blue they make a clear sky at noon look overcast. And on the other hand, my eyes are usually so grey they make an overcast sky look like a clear sky at noon.