In addition to genetics, the anatomic structure of the iris can also affect eye color to some degree. Geneticists now know that as many as 16 different genes influence eye color to some degree - far from the one or two genes that were once believed to determine iris hue. Common knowledge said that you could predict a child's eye color if you knew the color of their parents' eyes, and possibly the color of their grandparents' eyes. You can't predict if a child will have blue eyesĪt one time, it was believed that eye color, blue eyes included, was a simple genetic trait. SEE RELATED: Is blue the rarest eye color? 3. Eyes only appear to be these colors because of the way light strikes the layers of the iris and reflects back toward the viewer. Brown eyes have the highest amount of melanin in the iris, and blue eyes have the least.īrown melanin is the only pigment that exists in the eye there is no pigment for hazel or green - or blue. The color of our eyes depends on how much melanin is present in the iris. Blue eyes aren't actually blueīlue eye color is determined by melanin, and melanin is actually brown by nature.
"They have all inherited the same switch at exactly the same spot in their DNA." 2. "From this we can conclude that all blue-eyed individuals are linked to the same ancestor," said Eiberg. In addition to having significantly less melanin in their iris than people with brown eyes, hazel eyes or green eyes, blue-eyed individuals don't have very much variation in the part of their DNA responsible for melanin production.īrown-eyed individuals, on the other hand, have a lot more variation. This genetic switch limits how much melanin is produced in the iris - effectively "diluting" brown eyes to a shade of blue. Melanin is also responsible for the color of our skin, eyes and hair. "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."Įye color depends on how much of a pigment called melanin lives in the iris of the eye. "Originally, we all had brown eyes," said Hans Eiberg, associate professor in the Department of Cellular and Molecular Medicine at the university. That little DNA blip was blue eye color, according to researchers at the University of Copenhagen.Īs far as researchers can tell, this was the first person with blue eyes, and everyone who has blue eyes today is a (very) distant relative of this ancient human. Everyone with blue eyes is relatedīetween 6,000 and 10,000 years ago, a baby was born in Europe with a harmless genetic mutation. Rather than including a blue pigment, they actually just lack the pigment that makes eyes brown. Worldwide, fewer than 9% of people have blue eyes. About half as many Americans have blue eyes as brown eyes.
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