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How one ancestor helped turn our brown eyes BLUE ?

Everyone with blue eyes alive today – from Angelina Jolie to Wayne Rooney – can trace their ancestry back to one person who probably lived about 10,000 years ago in the Black Sea region, a study has found.

Scientists studying the genetics of eye colour 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 OCA2 that disrupted melanin production in the iris and caused the eye colour to become blue.

This indicates that the mutation originated in just one person who became the ancestor of all subsequent people in the world with blue eyes, according to a study by Professor Hans Eiberg and colleagues at the University of Copenhagen.

The scientists are not sure when the mutation occurred but other evidence suggested it probably arose about 10,000 years ago when there was a rapid expansion of the human population in Europe as a result of the spread of agriculture from the Middle East.
"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.

"Originally, we all had brown eyes," said Professor Eiberg. "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."

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, he 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," said Professor Eiberg.

Professor Eiberg said he has analysed the DNA of about 800 people with blue eyes, ranging from fair-skinned, blond-haired Scandinavians to dark-skinned, blue-eyed people living in Turkey and Jordan.

"All of them, apart from possibly one exception, had exactly the same DNA sequence in the region of the OCA2 gene. This to me indicates very strongly that there must have been a single, common ancestor of all these people," he said.

It is not known why blue eyes spread among the population of northern Europe and southern Russia. Explanations include the suggestions that the blue eye colour either offered some advantage in the long hours of daylight in the summer, or short hours of daylight in winter, or that the trait was deemed attractive and therefore advantageous in terms of sexual selection.

SEX TRAP

Sex could be the latest weapon in mankind’s unrelenting fight against mosquitoes.

Researchers at a fledgling UK firm are laying a “copulation trap” for mosquitoes which will eventually drive down the population of these pesky insects.

The technique that the five-year-old Oxitec or Oxford Insect Technologies — a spin-off from the University of Oxford — is developing is based on an interesting strategy: release a swarm of genetically engineered male mosquitoes whose mating with the female insects in the wild will yield progeny that are doomed to die as larvae or pupae. Sustained release of such healthy but reproductively-compromised mosquitoes will eventually lead to a crash in their population.