Every blue-eyed person on Earth can trace their ancestry back to a single individual who lived between 6,000 and 10,000 years ago.

Scientists have worked out that, long long ago, all humans had brown eyes. Until a specific gene mutation caused them to change.

The mutation comes from a gene called HERC2. Scientists say it switches off OCA2, another gene that regulates the amount of brown pigment that develops in the eye.

It’s believed the first person to have blue eyes lived in Europe up to 10,00 years ago. And every blue-eyed person alive today has that same mutation present in their body.

But it’s a very specific kind of gene mutation, which has meant that while eyes turned blue, hair and skin colour still retained the same levels of pigment.

A full switch off would result in albinism.

In Britain, the majority of people – 48% – have blue eyes, while 30% of us are green eyed and just 22% have brown ones.

Whereas there’s a pretty big variation in iris shades between green and brown, blue eyes have a tiny variation in the amount of melanin present.

And it’s this fact that has led Professor Eiberg, from the University of Copenhagen to suggest that blue-eyed individuals are all linked to the same ancestor.

‘They have an inherited the same switch at exactly the same spot in their DNA,’ he said.

Basically, it’s a wheel of genetic fortune what colour eyes you develop. Although brown is usually thought of as the more dominant gene, two brown-eyed parents won’t necessarily create a brown-eyed child.

It’s actually entirely possible for two brown-eyed parent to have a blue-eyed child, and vise versa.

So if you’re a blue-eyed person, you’ve got a much bigger family than you first thought. Which is kinda nice.

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