Blue Eyes

by Dave Weller

According to a Danish researcher, if you have blue eyes, you’re related to a common ancestor. He found that every blue-eyed person descended from one person whose genes mutated some 6,000 to 10,000 years ago. Before that, everyone had brown eyes. Geneticist Hans Eiberg says that blue eyes occur when the human default – brown eyes – is turned off.

Brown eyes are caused by the pigment melanin, which also gives color to hair and skin, and builds up in the eyes. The blue-eye mutation shuts off the gene that produces melanin in the eyes. That one mutation now exists in 300 million people!

Blue Eye

Eiberg says that the mutation is extremely specific: All people with blue eyes have the exact same genetic variation, and anyone with brown or green eyes do not. As a result, the mutation must have been passed down from a single person.