Posted: Jun 12, 2013 3:48 am
The variability of human eye colors expanded a lot with one drastic event within the last 10 millennia. Although there are at least a half-dozen genes that affect eye color, the one with the biggest effect is HERC2, the lightening allele of which is single-handedly responsible for most of the blues and greens out there. (I believe it's the only one of the eye-color genes with a drastic enough effect on its own to make eyes blue/green instead of brown/black regardless of which allele is present for any of the other relevant genes, although the others will affect the exact shade and probably could add up to blue/green on their own if they occurred in the right combination of alleles.)
10 millennia is a lot more recent than most of the major human migration events that established populations in different parts of the world, so the allele is still mostly found in the descendants of the population in which it originated, decreasing in frequency the farther you get away from the Baltic Sea. Whether the "new" mutant allele could be useful in farther-away parts of the world or not, it just hasn't had the chance.
I've heard that lighter-eyed people are more irritated by bright light and prone to being blinded by bright light including afternoon sunlight, but but also have better night vision. The sources I've heard this from were not scientific.
Mine have a blue background and enough of a starburst pattern of amber specks around the pupils to make them seem green on average, at least under some light conditions (blue under others), and I hate bright sunlight and love cloudy weather and the deep shade of a thick leafy forest... but I have reason to believe my preferences are based less on the physical nature of my eyes and more on the experiences stored in my brain.
10 millennia is a lot more recent than most of the major human migration events that established populations in different parts of the world, so the allele is still mostly found in the descendants of the population in which it originated, decreasing in frequency the farther you get away from the Baltic Sea. Whether the "new" mutant allele could be useful in farther-away parts of the world or not, it just hasn't had the chance.
I've heard that lighter-eyed people are more irritated by bright light and prone to being blinded by bright light including afternoon sunlight, but but also have better night vision. The sources I've heard this from were not scientific.
Mine have a blue background and enough of a starburst pattern of amber specks around the pupils to make them seem green on average, at least under some light conditions (blue under others), and I hate bright sunlight and love cloudy weather and the deep shade of a thick leafy forest... but I have reason to believe my preferences are based less on the physical nature of my eyes and more on the experiences stored in my brain.