Blue-eyed Humans Have A Single, Common Ancestor

[xan-i]

— New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.

What is the genetic mutation
“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Medicine. “But 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”. The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue. The switch’s effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour – a condition known as albinism.
Limited genetic variation
Variation in the colour of the eyes 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. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, 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 responsible for eye colour.
Nature shuffles our genes
The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival. As Professor Eiberg says, “it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.”
http://www.sciencedaily.com/releases/200...170343.htm

[Richard]

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

By MICHAEL HANLON

Everyone with blue eyes can be traced back 10,000 years to the Black Sea region
Throughout history they have been the eyes that are prized.

Frank Sinatra's were legendary, Paul Newman's melted a million hearts while Cameron Diaz's dazzle in modern Hollywood.

But how - and why - blue eyes arose has always been something of a genetic mystery. Until now.

According to a team of researchers from Copenhagen University, a single mutation which arose as recently as 6-10,000 years ago was responsible for all the blue-eyed people alive on Earth today.

The team, whose research is published in the journal Human Genetics, identified a single mutation in a gene called OCA2, which arose by chance somewhere around the northwest coasts of the Black Sea in one single individual, about 8,000 years ago.

The gene does not "make" blue in the iris; rather, it turns off the mechanism which produces brown melanin pigment. "Originally, we all had brown eyes," says Dr Hans Eiberg, who led the team.

And most people still do. The finding that a rare mutation, probably dispersed in the rapid wave of colonisation that followed the end of the last ice age, highlights one of the great mysteries of human evolution: the oddness of Europeans.

Those from Europe and the Near-East have many characteristics that set them apart from the rest of the human race.

Not only are Europeans far more likely to have blue eyes (95 per cent in some Scandinavian countries), they also have a far greater range of skin tones and hair colour than any other ethnic grouping.

Blue is the colour: Wayne Rooney and Daniel Craig

Brilliant blue: Uma Thurman and Cate Blanchett

It is only in Europe that you will find large numbers of blondes and redheads, brunettes, pale skins and olive skins, blueeyed and green-eyed people living together in the same communities. Across the rest of the world people are almost uniformly darkhaired and dark-eyed.

Why this should be remains unknown, and in particular how such mutations can have arisen so quickly since Europe was colonised by Africans just a few tens of thousands of years ago.

One theory is that Europe's cold weather and dark skies played a part. Fair skin is better at making Vitamin D from the 8 per cent of the world's population have blue eyes weak sunlight found in northern latitudes.

Another suggestion is that the strange skin, eye and hair colours seen in Europe are down to ancient interbreeding with the Neanderthals, who died out about 25,000 years ago.

Maybe the Neanderthals were blonde or red-haired and it is their genes which we have inherited. The trouble with this theory is that there is no evidence, from the scraps of Neanderthal DNA that have been recovered from bones, that there was any substantial interbreeding between them and Homo sapiens at all.

Perhaps the most plausible theory is that blonde hair and blue eyes arose because of a mechanism called sex selection.

This is where males and females choose as their mates those who have one unusual physical characteristic, not necessarily associated with "fitness" per se but simply something unusual.

The gigantic (and otherwise useless) tail of the peacock is the best example.

Sex selection comes to the fore when there is a lot of competition for mates of one sex or the other. The theory is that in Europe, where men had to spend weeks at a time out on the hunt, males were in very short supply.

In such societies, women who had flaxen locks stood a better chance of standing out and attracting the attention of the few men that would have been available for mating.

Even back then, the blue-eyed blonde was not only in demand, but also definitely would have had more fun.

Ol' Blue Eyes: The late Frank Sinatra, whose nickname was as famous as his songs

http://www.dailymail.co.uk/pages/live/articles/technology/technology.html?in_article_id=511473&in_page_id=1965

[William]

Yep, just saw this heheh.. ok, how many borthers and sisters do i have out there?? ;)

[Sily]

I'm a [color="green"]greeny[/color]. 

You [color="blue"]blues[/color] out there are very nice, but I [color="green"]love being green[/color]!