Mick Hartley

Why did Europeans turn white? Here's an interesting essay (via) which suggests, firstly, that the adaptation (the de-pigmentation, as it were) only happened after the agricultural revolution of ten to twelve thousand years ago; that it happened because of the need to synthesise vitamin D from sunlight as a result of a cereal diet which didn't provide another vitamin D from other sources; and that it happened only in Northern Europe because only there (here) was there the combination of high latitude/low sunlight, and a climate sufficiently mild because of the gulf stream, to allow for an agricultural life-style. It also suggests that the genetic mechanism for the change, and the reason why it could happen so rapidly in evolutionary terms, may be neotenous, since a darkening of skin tone is related to maturity, and so the perpetuation of a lighter skin tone could be achieved simply by delaying or stopping maturation. As we know, neoteny has been proposed, by Stephen Jay Gould amongst others, as a key feature in the evolution of humans from apes – hairlessness and so forth.

I don't think any of this is particularly contentious or revolutionary, but I haven't seen it all set down so clearly before. There's a short summary here.