Blue-eyed people wouldn't have existed if....

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London, Jan 31 (UNI) Every person on earth would have had brown eyes if that one person wasn't there.

If a study is to be believed, brown is the ''default'' colour for human eyes which results from a build-up of the dark skin pigment, melanin. However, in northern Europe a mutation arose in a gene known as OCA2 that disrupted melanin production in the iris and caused the eye colour to become blue.

''Originally, we all had brown eyes, 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,'' said reseracher Hans Eiberg from the University of Copenhagen.

The researchers found that people with blue eyes all over the world have just one ancestor who probably lived about 10,000 years ago in the Black Sea region, the Independent reported.

After studying the genetics of eye colour, scientists have discovered that more than 99.5 per cent of blue-eyed people who volunteered to have their DNA analysed have the same tiny mutation in the gene that determines the colour of the iris.

This indicates that the mutation originated in just one person who became the ancestor of all subsequent people in the world with blue eyes.

''The mutations responsible for blue eye colour most likely originate from the north-west part of the Black Sea region, where the great agricultural migration of the northern part of Europe took place in the Neolithic periods about 6,000 to 10,000 years ago,'' the researchers report in the journal Human Genetics.

Variations in the colour of people's eyes can 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, Professor Eiberg said.

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

Men and women with blue eyes have almost exactly the same genetic sequence in the part of the DNA responsible for eye colour.

However, brown-eyed people, by contrast, have a considerable amount of individual variation in that area of DNA.

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