My ideas about skin color & diet aren't original. I am pretty sure that I originally read them in Great Human Diasporas by L.L. Cavalli-Sforza. Here's the extract:
In Europe the development of agriculture has lead to the spread of cereals as the primary foodstuff over the last ten thousand years. Unlike meat, particular fish liver, cereals contain no vitamin D. They do, however, contain a precursor taht becomes vitamin D if exposed to the ultraviolet light from the sun's rays absorbed through the skin. Cereal eaters can produce enough vitamin D to survive and grow normally if they are fair-skinned. Therefore, people can inhabit northerly regions where there is less sunlight, and continue to eat coreal products because a fair skin color has been less selected during evolution. In certain northerly regions, however, an even in the far north, some peoples such as the Eskimoes, have always eaten enough vitamin D from fish or meat to make fair skin unnecessary....
Does it really say "Therefore, people can inhabit northerly regions where there is less sunlight, and continue to eat coreal products because a fair skin color has been less selected during evolution" ? Shouldn't that be "more selected" or even ""selected" ?
The first place where I encountered the idea that very white skin (not merely "light" skin) was very recent and caused by a ceral based diet (in the order of 6000 years or so) was Frank W . Sweet's backintyme forum . He located the origin of "very white" skin pretty much where european lactose tolerance arose : More or less around the Baltic .
His argument was that the areas around the baltic are relatively warm for their latitude, thus making agriculture very much viable . That same very high latitude means that , combined with a ceral based diet, it's pretty much impossible for a dark skinned people to live there . Very light skin would be very strongly selected in those particular circumstances .
yeah, i think the wording was clumsy there. i don't really know if vitamin D was the reason, i'm open to other rationales such as sexual selection, though there are prior reasons i'm a bit skeptical of that last idea being the primary driver.
re: frank sweet, yeah, that was where i first saw it too. or so i thought. i read 'human diasporas' and i probably read it there, cavalli-sforza has long had these sort of ideas from what i have heard so i suspect sweet wasn't familiar with cavalli-sforza's theories. i just thought we should give props were they're due.