New theory: Blondes evolved because of sexy high estrogen

Immediately after the last Ice Age 10,000 years ago, Northern Europe had many more women than men, and cavemen preferred blondes for their high estrogen levels, a new study finds.

This study at the University of St. Andews in England is supposed to explain the quick evolution to Nordic blonds, but the logic is muddled.

First question: If blond women have high estrogen levels, why would the high mortality rate among post-Ice Age men (dying while hunting) contribute to the rapid appearance of blonds? I guess the anthropologists are saying the blondes would have attracted men anyway, but because of the male shortage, fewer (theoretically less attractive) brunettes had mates, so blonds reproduced faster yet in proportion to their numbers.

Surprising fact. Blonds today are called a dying breed. Because relatively few humans carry the blond gene, and relatively few of them are having children, the World Health Organization predicts that blonds will be extinct by the year 2202.

I doubt it.

Frank Warner

Update: JJ Mollo says the World Health Organization has denied any knowledge of a theory that blonds are becoming extinct. The extinction story may be a hoax. Those recessive genes just don't go away.

Comments

[Nicholas]

Nit pick: we are currently in an ice age interglacial period. The transition 10 000 years ago you are referring to was from the glacial period to the inter-glacial period.

I believe that, when the planet is not in an ice age, there's virtually no ice at all, even at the poles.

See here for more information.

[jj mollo]

Blondness may well be an adaptation related to fair skin in order to improve access to sunlight in northern latitudes. Humans require vitamin D, which is catalyzed under the skin by sunlight. The hair color may be an accidental co-evolved feature related to fair skin, or it may provide additional solar exposure. Blondness is also an avertisement for youth since it, as well as red hair color, tends to disappear with age. In a male-sparse environment, male preferrences will dominate, giving relative advantage to younger women. The genetic outcome will be that women will tend to remain blond longer (neoteny).

I would bet that the prevalence of genes for blondness are actually increasing in the population, but may not be expressed as often due to the fact that the feature is recessive. At any rate, the article on Wikipedia claims that the disappearance assertion is a myth. The young lady pictured appears to me to have a selective advantage in any environment.

[Stephen Cobb]

To JJ Mollo's excellent comment I will add the clarification that it is unlikely that blondes have more estrogen than non-blondes, but rather that young blondes have more than old blondes.

This is just one of many theories for the purpose of blond hair. The one I like concerns "paternal confidence": men prefer a woman with a combination of dominant and recessive genes such that a child is likely to resemble the father. It has been shown that blue-eyed men prefer blue-eyed women, but no other combination produces a preference.