Danish geneticists say everyone with blue eyes is not just related, but descended from one person, CBS News correspondent Sheila MacVicar reports.
In the basement of the University of Copenhagen, frozen in vats of liquid nitrogen are thousands of DNA samples.
"This is like our secret, our gold mine," said Prof. Jesper Troelsen, a geneticist. "We dig down and find the samples we are going to use and ask specific questions about genetics."
And this time the question was, "what makes blue eyes blue?"
"All people with blue eye color have a special fingerprint," said gene mapper Hans Eiberg.
Brown, they say, is the default color for human eyes ... produced by melanin.
Blue eyes are caused by a genetic switch, programmed to suppress the melanin. It's a genetic mutation.
And in the DNA of hundreds of blue-eyed people tested by the Danish team, they found exactly the same mutation every time.
"And what would the chances of that coming from more than one person? It has to be from one person?" MacVicar asked.
"Yes, we are very sure," Eiberg said.
The first blue eyed person was probably born near the Black Sea just 10,000 years ago when the entire population of the world was less than 50,000.
Those mutant genes spread on a wave of human migration.
Today, nearly 95 percent of Scandinavians have blue eyes.
What scientists don't know is if having blue eyes was some kind of evolutionary advantage … if blue-eyed people could see better in the low winter light of Northern Europe for example. Or, was it just about downright attractiveness?
Genetics really can turn your brown eyes blue, and now, there is a whole new answer to that question: "Where did ya get those eyes?"