Peter Frost claims that around the end of the last major ice age (Young Dryas which ended around 8000-7000 bc), male population was an extremely small portion of the population. men to women ratio at around 8000 bc was estimated to be 1:17 in europe and northern asia. so for every man there were 17 women.

This period led to an extreme selection pressure for women. He claims that blonde hair blue eyes are so much more common among women than in man because man find women with lighter features to be more attractive while women find men with darker features more attractive. Due to the fact that there were so few men around, only women with lighter hair and eyes would successfully breed, leading to large differences in colours between men and women in northern european population.

Also he claims that in pretty much all human socieites, people with lighter skin occupy higher strata while darker people occupy lower strata because men with higher status choose to marry women with lighter features, and men with lower status marry darker women.

According to templer (2006) skin lightness and iq correlates at 0.92. Also according to Woodley, IQ correlates weakly with hair brightness and eye colour brightness.