Researchers at the University of Copenhagen have discovered a single genetic mutation that took place six to ten million years ago and is believed to be responsible for blue irises in human eyes. According to Professor Eiberg from the Department of Cellular and Molecular Medicine at the University of Copenhagen, “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”.
Of course, many people still have brown eyes. It is, in fact, the most common eye color. However, the OCA2 gene code, which is involved in the production of melanin that gives pigment to our eyes, “switched” millennia ago, diluting the color brown to blue in certain individuals.
A Common Ancestor
According to Professor Eiberg, “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.” By contrast, people with brown eyes have innumerable individual variations in the area of DNA which controls the production of melanin.
Beginning the study in 1996, Eiberg and a team of researchers examined mitochondrial DNA from individuals in countries including Denmark, Jordan, and Turkey. They have concluded that this switch has no profound positive or negative effects on vision, but does show “That nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.”
No matter what color your eyes, frequent eye examinations are necessary to ensure optimal vision. Please use our Eye Doctor Directory to find an experienced ophthalmologist in your area.