Blue eyes are necessary for the iris to synthesize vitamin D3 and folate at latitudes where the sun's UVA and UVB rays' angle of incidence is larger. Blue eyes are basically just white skin in eye form. The LACK of pigment is just a feature fitted to the extreme environment where Cac's emerged from between the Black and Caspian seas and then in the direction of the Baltic sea. If you remove melanin from black people's eyes...their color would appear blue, surprise, surprise. This is why old blck people have white hair and their eyes turn a milky blueish color. They have lost their melanin. Melanin is a shield that allows us to live in the more desireable areas of the earth without worrying about skin cancer. On average it takes a black person two hours to burn in the sun while it takes a white person 15 minutes or so. And
is just 
Come on man...
That's a good theory, but it doesn't make sense now that we know that dark skin makes a good amount of vitamin D as well as lighter skin. The theory of white skin developing to manufacture vitamin D, because dark skin isn't that good at it unless in certain climates, doesn't have legs to me, being that we now know it was the type of testing to determine vitamin D levels, that showed blacks had low vitamin D levels.
My theory is it was the blue eyes themselves that caused the skin to eventually become almost white. Blue eyes make it hard for your brain to make melatonin. From serotonin comes melatonin, and melatonin is what's needed to make melanocyte stimulating hormones(msh). Then the msh goes to the skin, and from there, melatonin causes the melanin to build up in the skin which gives color.
Diet plays a part as well. If a blue eyed person doesn't eat a lot of carbohydrate rich foods, and just mainly protein, they won't have much serotonin being made in their brain, and that ultimately means low melanin.
Here's an article on blue eyes, and light skin, but because they can't let their vitamin D theory go, they still come up with theories based on vitamin D. The picture they drew also is another thing they can't except, that black people are the original explorers of Ancient Europe. They say he was dark skin, and blue eyes, but they drew a regular looking white person!
Influence of eye colors of Caucasians and Asians on suppression of melatonin secretion by light. - PubMed - NCBI
DNA Of Ancient Human Spawns New Theory Of Why Europeans Became White
How A Vitamin D Test Misdiagnosed African-Americans
In a hypothetical black dominated world,would there be an obsession with kinky hair given its rarity/exclusivity to blacks?
