Why hasn't baldness been selected out of the human gene pool?

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Why hasn’t baldness been selected out of the human gene pool?

Many men, at some point in their adult lives, have to deal with losing their hair, but if it’s such an undesirable trait, why has it been part of the human genome for a hundred thousand years? Why have we not self-selected against it by now?

The hair on our heads may protect us from the noonday sun, maintain body heat when it is cold, and even attract a mate. If so, men who lose their hair are at a disadvantage, and you would expect natural and sexual selection to have weeded them out. So why haven’t bald men like me, or at least our versions of genes, gone extinct?

One early stab at answering this question rested on the idea that a man’s genetic predisposition to baldness is found in genes he inherited from his mother. Since she would not have suffered baldness and its concomitant ill effects, natural selection would have no cause to remove these genetic variants. But think about it carefully and the logic fails - mothers are just as likely to have sons as daughters and every time they do, if these males are less likely to procreate, these variants should become rarer. In any case, science has shown that this mother-based hypothesis is wrong.

Instead, scientists have recently been positing many theories about why baldies aren’t dying out—and most revolve around making some attempt to argue that baldness offers some kind of evolutionary advantage. Some researchers suggests, for instance, that it signals dominance and status, while others suggest that it shows people that they offer maturity, wisdom and nurturance.

There are also other goofy theories about how allowing more sun to reach the scalp can reduce the chances of prostate cancer in older men, which is not only completely unproven, but completely stupid.

The social aversion that some people feel towards baldness has really only been happening in the last hundred years, and it’s generally a much bigger deal to the person to whom it’s happening to and normal to everyone else. The guy in the photo above may be upset about losing his hair, but no one else gives a shit.

Before the 20th century, for thousands of years, going bald was a sign of maturity, respect and wisdom in cultures around the world. Hell, for a long time in Japan, younger men would shave the tops of their heads to mimic male baldness patterns so they would appear more mature.

Also, without looking at the genome, you can’t select for traits that happen when you’re an older adult. Things that we may consciously or unconsciously select in a mate, we do so in the teenage years or early 20s when we’re most sexually active. And at that point, if someone is attractive and healthy and can do the deed, they’re good enough.

Via