Everyone in the world who has blue eyes shares something in common with each other, aside from the obvious detail that they've all got blue eyes.
You might have heard once upon a time that everyone has blue eyes when they're born but this is actually an urban myth.
When you were born your eyes aren't guaranteed to have been blue and in fact as far as eye colours are concerned it's actually quite the newcomer.
According to studies from a team of researchers at the University of Copenhagen the blue eye colour popped up some time in the last 6,000 to 10,000 years, so it's a bit hard to nail down exactly when blue eyes became a thing.
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However, what the researchers found is that this starting point contains something which all blue-eyed people on the planet have in common.
According to the researchers, everyone in the world who has blue eyes shares a common ancestor with the first ever person to have eyes of blue, which means all blue-eyed people are technically related if you can make the family tree stretch back far enough.
Fret not, however, as sharing a common ancestor several thousand years in the past doesn't mean you have to add all of their other descendants to the Christmas card list.
You might be wondering why this is the case and for that we'll defer to the explanation the experts gave after making their discovery.
Here's the science-y bit, as lead researcher Professor Hans Eiberg of the University of Copenhagen's Department of Cellular and Molecular Medicine put it.
He said: "A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch', which literally 'turned off' the ability to produce brown eyes.
"The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin."
"The 'switch', which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris - effectively 'diluting' brown eyes to blue."
If you understood all of that then congratulations, and if you didn't then just take Professor Eiberg's word for it that 'all blue-eyed individuals are linked to the same ancestor' because 'they have all inherited the same switch at exactly the same spot in their DNA'.
Isn't science wonderful?
Joe Harker