Blue eyes are another recent-evolved trait and scientists have determined it cam

Question

Blue eyes are another recent-evolved trait and scientists have determined it came from a mutation in a single ancestor 6,000-10,000 years ago.

The mutation affected the OCA2 gene, which codes the protein necessary for producing melanin, which gives our skin, hair and eyes their color. This essentially "switched off" the ability to have brown eyes by limiting the melanin produced in the iris, and "diluting" the eye color from brown to blue.

Having lighter eyes didn't give anyone a particular survival advantage, but because the gene for blue eyes operates similarly to a recessive trait (though it's a little more complicated), blue-eyed fathers could better guarantee that their children were, in fact, their own.

discuss this evolutionary change in modern human. which evolutionary concept/mechanism led to this evolution?

Explanation / Answer

The gene which controls eye colour OCA2 is closely related to the genes that give colour to skin and hair. Earlier it is believed that all the human ancestors had dark brown or nearly black eyes. Dark colour of the skin and eyes were naturally favoured for protection against the harmful ultraviolet rays and warm temperatures. Brown was a default colour for human eyes due to the pigment melanin. As people began to migrate to various places around the world, different seasons and temperatures were encountered which did not exert selection pressure for dark eyes and skin. A mutation arose in the gene OCA2 (on chromosome 15) which disrupted the melanin production in the iris and changed the eye colour to blue. The trait was deemed advantageous in terms of sexual selection and thus was favoured.

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