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Monday, October 13, 2008
Two genes cause baldness among Caucasoids
There's a lot of talk about founder effects for blond hair, blue eyes or lactose tolerance... but what about baldness? Actually that is also largely in the genes: an X chromosome gene was already known and now another alelle in chromosme 20 has been discovered. These two are much more common apparently among Caucasoids (or Western Eurasians) than among other populations, causing that one male out of seven (14%) has severe problems of baldness.
The research paper by J.B. Richards et al. has been published in Nature (behind paywall) and mentioned in Science Daily.
What I wonder is, in the field of population genetics, who were the founders of these dynasties of bald people. They were pretty succesful founding parents certainly, in spite of their aesthetic disadvantage (certainly not any major adaptative problem, specially if you know of hats).
An interesting note is that Magdalenian people already depicted some of them as bald. This is something I had not thought about before but one of the series of Magdalenian portraits from La Marche is clearly missing hair:
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Maju - I think the Magdalenian pictures you refer to are on the floor at La Marche cave - check this link...
http://news.bbc.co.uk/2/hi/science/nature/2012385.stm
Yes, thanks very much. I knew the La Marche site name but could not find the images in several searches, so I gave up. Precisely the bald guy is shown in that article, so I'll link that image, which was what I wanted to do originally.
The bald man looks far older than I would have expected to be common in the Magdelalenian.
I have read that to the average person baldness is associated with lack of assertiveness and that thick hair is associated with aggression. For what it is worth ( according to Stephen J. Gould not much) Lombroso thought a total lack of baldness was a characteristic that was more common among criminals
I've known dangerous criminals that were bald and calm men with full hair. Can't say much more though it does seem to be partly associated with hormonal imbalances.
I think that we tend to have a rather extreme view of life expectancy and, specially, of actual individual life span in prehistoric societies. While life expectancy in general was surely much lower than today (but not necesarily much lower than in, say, Neolithic times or even early Modern Age, when life expectancy was hardly over 40, something that still stands true for some underdeveloped nations), it's clear that some people must have reached old age anyhow. And this you can see in any account of historical hunter-gatherers or primitive farmers.
Life expectancy does not put an a ge limit to what individual people can live, it just expresses the odds. So, if life expectancy is 40, half of the people would die before that age... but the other half would live longer, maybe much longer in some cases.
95% of individuals who suffer from hair loss are known to have androgenetic alopecia (AGA). Studies published in the scientific journal Nature Genetics demonstrated that the presence of two genetic variants multiplied by seven shows the risk of baldness.
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