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7th August 2024
03:32pm BST
All blue-eyed people descend from a single human who lived around 6,000 and 10,000 years ago, scientists believe.
While 70-79 per cent of the world's population have brown eyes - the most common colour - just 8 to 10 per cent have the second most common colour, blue.
And everyone on Earth had brown eyes around 10,000 years ago, the American Academy of Ophthalmology (AAO) reports.
It was a research team from the University of Copenhagen who discovered blue-eyed beings all come from the same person. Researchers were trying to find out what caused the change in eye colour all those years ago by studying the OCA2 gene, which determines the level of brown pigment in a person's eye.
The study, published in 2008, discovered that the genetic mutation that creates blue eyes is actually from a completely different gene, HERC2. This gene completely turned off the OCA2 gene, and dilutes brown eyes to blue.
Scientists realised that every single blue-eyed person has the same mutation, which led them to believe that they all descend from the same person. It is thought the mutation could have spread when humans migrated from Africa to Europe - though there is still a lot of research to be done.
Researchers also looked at less common eye colours, such as green, which enabled them to understand why people have this colour eye, and also supported the idea that one person was the origin of the blue-eyed gene.
Author of the study, Professor Hans Eiberg from the Department of Cellular and Molecular Medicine, told Science Daily: "Meanwhile, people who have green eyes can be explained by the fact they have a reduced amount of melanin in the iris, which is very different to those with blue eyes."
"From this, we can conclude that 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," he added.
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