Every blue-eyed person is a descendant of one single human

Everyone in the world with blue eyes can actually trace their lineage back to one person who lived thousands of years ago.

If you go back far enough up your family tree, you'll probably find out that you're related to some pretty interesting people.

Unless your entire family has spent all of eternity living in a cave far removed from civilisation, then there's a pretty good chance that at some point at least one of your ancestors was important enough to have their own Wikipedia article.

No matter who you're related to, it's still you that makes you unique but there's still traits you'll have in common with plenty of people around the world.

Some people are able to find pretty much exact copies of themselves by just wandering around in the big wide world, but for most, it's more just a similarity of characteristic.

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Take eye colour for example, there's a bit of an urban myth going around that when a baby is born they're always blue-eyed.

It's simply not true, though it is true that the eye colour a baby is born with isn't always the one they'll have as they grow up.

However, everyone who keeps their blue eyes shares a common ancestor who lived between 6,000 and 10,000 years ago.

That's a pretty wide window of time to try and pin down one life but, thanks to researchers, it's been worked out that this one person is the common ancestor of millions of people around the world.

And here's the science-y bit, in our eyes there's something called the OCA2 gene, which determines the level of brown pigment in them.

Blue-eyed people have a gene called HERC2 which shuts off the OCA2 and results in a person developing blue eyes.

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Every blue-eyed person in the world has the HERC2 gene, with this exact same mutation being passed down through generations and scientists have concluded that it all came from one original person.

The work was done by a team of researchers from the University of Copenhagen, which identified the initial mutation and realised that it was present in everyone with blue eyes.

So if you've got blue-eyes and know someone else who does, you now know that if you go far back enough you're actually family, though the same could be said for any number of strangers you pass on the street.

Since this common ancestor lived several thousand years ago, it's also probably safe to summarise that you are distantly related enough not to feel obliged to stick between eight and 10 percent of the world's population on the Christmas card list.