Research shows that people who have blue eyes all come from the same single common ancestor. A research team at the University of Copenhagen have tracked down a genetic mutation that occurred around 6-10,000 years ago and resulted in all the blue eyed humans that exist in the world today.

Image courtesy of butler.corey

Professor Eiberg from the Department of Cellular and Molecular Medicine said of the discovery that, “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.” The gene code that is referred to as the switch affecting factor, relates to the P protein which is involved with the production of melanin – the pigment that gives color to our hair, eyes and skin. The mutation that occurred centuries ago didn’t turn off the gene completely but limited its action so that the production of melanin in the iris is reduced, resulting in the diluting of brown eyes to blue. If the OCA2 gene has been utterly destroyed or ‘turned off’, all human beings within this generation line would be without melanin in their hair, eyes or skin colours – a condition we know as albinism.

The variation that is found in the color of the eyes from brown to green can all be explained by the amount of melanin that is in the individual’s iris – but blue eyed people have only a small amount of variation in the amount of melanin in their eyes. And from this evidence it was concluded that all the modern day blue eyed individuals are lined to the same ancestor, as “they have all inherited the same switch at exactly the same spot in their DNA” says Professor Eiberg. The research that led the team to this conclusion was undertaken in countries as diverse as Jordan, Denmark and Turkey, to make sure that each individual studied would be geographically far from other individuals with blue eyes, yet could potentially have similar levels of melanin that would back up Eiberg’s theory. The research took a decade of dedicated genetic study after the Professor first identified the OCA2 gene as potentially being responsible for eye color.

Our genes mutate all the time and often can have neither a negative or positive reaction, it is simply a part of our constant evolution. Although many of these changes will not have an effect on a human’s chance of survival, which is generally why a gene mutates, the discovery of mutations like this allows us to to trace all the way back to a common ancestor who fathered all of the blue eyed humans.

by Ellie Cambridge