by Peter Frost
Most humans have only one hair color and one eye color.Europeans are a big exception: their hair is black but alsobrown, flaxen, golden, or red; their eyes are brown but alsoblue, gray, hazel, or green. This diversity reaches a maximum inan area centered on the East Baltic and covering northern andeastern Europe. If we move outward, to the south and east, we seea rapid return to the human norm: hair becomes uniformly blackand eyes uniformly brown.
Why this color diversity? And why only inEurope? Some believe it to be a side effect of natural selectionfor fairer skin to ensure enough vitamin D at northern latitudes.Yet skin color is weakly influenced by the different alleles forhair color or eye color, apart from the ones for red hair or blueeyes. Some have no effect at all on skin pigmentation (Duffyet al. 2004; Sturm and Frudakis 2004).
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But why do we see more of this color diversity in Europe thanelsewhere? Perhaps because sexual selection was stronger inancestral Europeans, particularly during the long period whenthey lived from hunting and gathering.
Among contemporary hunter-gatherers, the ratio of single mento single women is most unequal in “steppe-tundra”environments where almost all consumable biomass is in the formof highly mobile and spatially concentrated herbivores such ascaribou, reindeer, or muskox. On the one hand, men die youngerbecause of the distances they must cover in search of herds, withno alternate food sources. On the other, men are less polygynousbecause they bear almost the full cost of feeding their familiesin a habitat that offers women little opportunity for foodgathering. With fewer men altogether and even fewer polygynousones, women have to compete for a limited supply of potentialhusbands. They are thus under stronger sexual selection.