Everyone with blue eyes is related

All in the family

Danish geneticist, Hans Eiberg, concluded in 2008, after extensive research into the heredity of eye colour, that all humans with blue eyes are related to each other. The relation stems back all the way to the first person with blue eyes. Once upon a time everyone had brown eyes but around 10,000 years ago a genetic mutation gave someone in Europe blue eyes. Now there are about 150 million people (2.2% of the world population) with blue eyes in the world. They are all descendants from that one European and inherited his genetic mutation.

But how does it work?

A gene called OCA2 gives people naturally brown eyes. Whether your eyes are light or dark brown depends on the melanin pigment, OCA2 determines how much melanin is present in your eyes. Until Eiberg’s discovery, scientists always thought that this gene also held the answer to the mystery of blue eyed people. Instead it is the gene HERC2 that is the cause of blue eyes. This gene blocks the part of the OCA2 gene that puts melanin in eyes, thus giving people blue eyes.

Blue eyes are attractive

The HERC2 gene likely first appeared in someone who belonged to the first group of people who moved from Africa to Europe, one of the first Europeans. This explains why only people of European descent have blue eyes. Such a genetic mutation can be triggered by different factors, such as natural selection or a survival method. Another, less scientific, notion states that people with blue eyes are more attractive to future partners and therefore produce more offspring.

The heredity of eye colour

Research shows that everyone with blue eyes has the HERC2 gene, this is caused by the heredity of eye colour. This means that part of the DNA of these people matches, which is a sign of a familiar relationship and proofs the theory that everyone with blue eyes is a descendent of the first person with blue eyes. But who was this person? A skeleton, found in northern Spain and dating back 7000 years, has the genetic markers for blue eyes but it is impossible to tell if this was the first person with blue eyes.