It has been suggested that the variation in skin, hair, and eye color seen in European populations is related to sexual selection and is driven by high latitude females' need for more paternal investment from their male mates, so they have diversified more into eye-catching differences.

One might be able to test this with other populations to see what kinds of looks correlate with a need for strong paternal investment.

One negative test can be seen in "March of the Penguins." The Emperor penguin ladies need extraordinary levels of devotion from their males, but, at least to my eye, I couldn't tell any of the penguins apart, including not being able to see the difference between males and females. The movie claims that they can recognize each other by sound.

The abstract is available, full text + links costs $30.

steve,

yes, i've heard of this. i wouldn't necessarily discount the hypothesis because of the penguins though, how do you know that their voices aren't extremely diverse? runaway sexual selection is obviously almost capricious, and i don't think anyone assumes that was going on in europe, but, beauty as a fitness indicator might random walk to all sorts of fitness peaks. as regards humans, it seems that not all circumpolar peoples hit on the strategy of color differentiation, the inuit and the peoples are siberia are relatively dark compared to europeans.