It is estimated that between 20 and 40 percent of Europeans have blue eyes, but the exact reason for blue eyes is not yet known. Scientists believe that it is a genetic mutation and that the gene survived because people with that eye color were considered more physically attractive, so they had more opportunities to reproduce.
Eye color is determined by the amount of pigment in the iris of the eye. A lot of pigment means brown eyes, less pigment means green eyes, and little or no pigment means blue eyes.
As many as 16 genes determine eye color, but the two main ones are “HERC2” and “OCA2”, with “HERC2” acting as a switch that activates “OCA2”, which then activates the proteins that produce pigments.
If one of these two genes mutates and stops performing its function, the chain of reactions is interrupted and the proteins do not create pigments. And the result is blue eyes.
Everyone has two of each type of gene in their body, one from their father and one from their mother. If one parent has the mutated “OCA2” gene, and the other all “normal”, the child will also have brown eyes.
If both parents have mutated “OCA2”, there is a 25 percent chance that the child will have blue eyes. In theory, a hidden mutated “OCA2” could be passed down through the family for generations without anyone having blue eyes.
Research conducted at the University of Copenhagen looked at the DNA of blue-eyed people and found that 99.9 of them had a mutation in the “OCA2” gene.
Because of this, scientists believe that all blue-eyed people come from a common ancestor, which means that they are, in fact, relatives.
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