Why do I have blue eyes?

The answers lies in the Mesolithic period...

A baby with blue eyes (WestEnd61/REX Shutterstock)

If you have ever wondered why, like Cameron Diaz, Leonard Di Caprio and Frank Sinatra, you have blue eyes it is because you share a gene mutation first seen in a Stone Age man who lived around 7,000 years ago.

Scientists pinpointed the first person believed to have had blue eyes after discovering his well-preserved remains in a cave system in north-west Spain, in 2006.

Tests later showed that the man had the dark-skinned genes found in Africa, but was more closely related to modern-day Scandinavians than other Europeans, and had lived in the middle of the Mesolithic period.

Scientists were lead to their discovery published in the journal Nature by sequencing fragments of DNA extracted from the man’s tooth.

“The biggest surprise was to discover that this individual possessed African versions of the genes that determine the light pigmentation of the current Europeans, which indicates that he had dark skin,” said Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona when the study was published in 2014.

Baby Monkey born with piercing blue eyes at London Zoo

“Even more surprising was to find that he possessed the genetic variations that produce blue eyes in current Europeans, resulting in a unique phenotype [physical type] in a genome that is otherwise clearly northern European,” Dr Lalueza-Fox said.

“Blue eyes in modern humans are related to the same mutation in a gene called HERC2. If you have this mutation in both copies of the chromosome, you will have blue eyes for sure. This was the case with this man, who is so far the oldest known individual with blue eyes,” he said.

A previous study in 2008 found that the earliest blue eye-colour gene mutations which led to the evolution of blue eyes likely happened around 10,000 years ago in individuals who lived around the Black Sea.