There's another school of thought that attributes the variety of hair, skin, and eye color in Europe to sexual selection rather than the brightness of the sun. In brief, Europe during the last glacial period offered very little food for women to gather, so women were almost completely dependent upon men for hunted meat. As a result of this imbalance, women developed striking looks to attract men.
For an example of this line of thinking in the evolutionary literature see: "European hair and eye color: A case of frequency-dependent sexual selection?" (Frost 2006) [1]
Human hair and eye color is unusually diverse in northern and eastern Europe. The many alleles involved (at least seven for hair color) and their independent origin over a short span of evolutionary time indicate some kind of selection. Sexual selection is particularly indicated because it is known to favor color traits and color polymorphisms. In addition, hair and eye color is most diverse in what used to be, when first peopled by hunter-gatherers, a unique ecozone of low-latitude continental tundra. This type of environment skews the operational sex ratio (OSR) of hunter-gatherers toward a male shortage in two ways: (1) men have to hunt highly mobile and spatially concentrated herbivores over longer distances, with no alternate food sources in case of failure, the result being more deaths among young men; (2) women have fewer opportunities for food gathering and thus require more male provisioning, the result being less polygyny. These two factors combine to leave more women than men unmated at any one time. Such an OSR imbalance would have increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of color traits: hair- and eye-color diversity and, possibly, extreme skin depigmentation.
[1]: http://www.ehbonline.org/article/S1090-5138(05)00059-0/abstr...
