Eye color is a polygenic trait, i.e., it's determined by more than one gene. SEE RELATED: Computer vision syndrome & digital eye strain: Symptoms & treatment. Eye color is partially affected by light, especially blue eyes, which get their color specifically by light entering and reflecting out of the eye. How eye color develops and why it changes. Lower birth rate. Blue is the second most common and brown tops the list with 45% of the U.S. population and possibly almost 80% worldwide. Neanderthals had a large mental foramen in their mandible for facial blood supply, meaning that their side jaws and cheeks were well supplied with blood. If You Have Blue Eyes, You're Related to More People Than You Thought Blue-eyed humans have a single, common ancestor. Test. Dry Eyes For two parents with brown eyes to have a blue-eyed child, both parents must genetically be Bb. Why do some people have light blue eyes and others have dark blue? Edible Are blue eyes a sign of inbreeding? More likely than the other is the first. However, the gene for blue eyes is recessive so you'll need both of them to get blue eyes. By diluting brown eyes to a shade of blue, this genetic switch restricts how much melanin is produced in the iris. Neanderthals had jaws large enough to comfortably house all of their teeth, even having a gap behind their wisdom teeth. Melanin is a brown pigment that controls the colour of our skin, eyes and hair. All About Vision does not provide medical advice, diagnosis or treatment. It surprises me to say that the majority of Europeans with blue eyes seem to be fairly closely related. A study, headed by Dr David Balding, examined inbreeding in pedigree dogs. In modern times, most people who claim to be of Viking descent have blonde hair and blue eyes, but that doesnt mean that all Vikings shared this appearance. So if blue eyes are the result of a genetic mutation in a single individual, how did the trait spread from just one person to being present in 20 to 40 percent of the populations of some European countries today? A comparison of ingrade and average modern human finger bones shows how much more robust ingrade hands were especially the tips (distal phalanges).