None Blue-eyed Ancestry
By tony leather, 8th Apr 2012 | Follow this author
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Posted in WikinutNewsScience
The genetic mutation affecting our chromosomes resulted in creating a switch to turn off the brown eye production in some humans.
None Blue-eyed Ancestry
Blue-eyed people have a single, common ancestor, new research reveals, as a team of scientists has tracked down a genetic mutation that leads to the coloration. It seems a mutation occurred 6 to 10,000 years ago, before which blue eyes were unknown.
In those ancient times every human was brown-eyes, and the mutation concerned affected the OCA2 gene, involved in the production of the pigment that gives colour to hair, skin and eyes, dubbed melanin. The genetic mutation affecting our chromosomes resulted in creating a switch to turn off the brown eye production in some humans.
This switch is found in the gene adjacent to OCA2, not actually turning off the gene completely but instead limiting its action, thus reducng the level of melanin production in the iris, diluting brown eyes to the colour blue, because a complete OCA2 gene shutdown would make the person concerned an albino.
DNA from the energy-making structures of cells - the mitochondria - of blue-eyed people in middle-eastern in countries, genetic material coming from females, meaning that maternal lineages can be traced through it.
Over many generations, ancestral DNA segments get shuffled, individuals thus having varying sequences.
Non-reshuffled DNA segments are called haplotypes, and if any group shares long haplotypes, they must have arisen relatively recently in human ancestry. This means that blue-eyed people all have this same haplotype, so also exactly the same genetic mutation that makes eyes blue.
In a survey of 800 persons, only one person did not fit with the findings, though his eye colour was blue with a single brown spot, so it can becan concluded that all blue-eyed individuals are linked to the same ancestor, and have all inherited the same switch at exactly the same spot in their DNA.
Why humanity took the leap from a situation where nobody on Earth 10,000 years ago had blue eyes, to the modern statistic of 20 - 40% Europeans having blue eyes is a mystery, though some feel that the eye-colour influences the number of offspring born, while this supposition remains to be proved.
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