As for being descended from the same person, the evidence for this is because every blue eyed person alive today has this same mutation.
Scientists reckon only 8 to 10 per cent of the population have blue eyes and eyes don't fully develop in childhood meaning the brown pigment can kick in later, causing blue eyed children to end up with brown eyes in adulthood.
So if you have blue eyes, now you know - your family is a lot bigger than you might have thought previously.
A team at the University of Copenhagen released research on the subject.
Professor Hans Eiberg from the Department of Cellular and Molecular Medicine said: "Originally, we all had brown eyes. But 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."
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