Is there an evolutionary advantage to Male Pattern Baldness?

Discussion in 'Biology & Genetics' started by etherometer, Jul 10, 2014.

  1. etherometer Banned Banned

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    Most theories regard it as resulting from sexual selection. A number of other primate species also experience hair loss following puberty, and some primate species clearly use an enlarged forehead, created both anatomically and through strategies such as frontal balding, to convey increased status and maturity. The assertion that MPB is intended to convey a social message is supported by the fact that the distribution of androgen receptors in the scalp differs between men and women, and older women or women with high androgen levels often exhibit diffuse thinning of hair as opposed to male pattern baldness.

    Previous research had determined that male pattern baldness, also known as androgenic alopecia, has a highly genetic origin. It is estimated that 80% of baldness in a population is influenced by genetic factors.

    "The strong genetic basis of hair loss is odd, as any evolutionary advantage is unclear," says Spector.

    From the American Hair Loss Asociation:

    Androgenic alopecia in women is due to the action of androgens, male hormones that are typically present in only small amounts. Androgenic alopecia can be caused by a variety of factors tied to the actions of hormones, including, ovarian cysts, the taking of high androgen index birth control pills, pregnancy, and menopause. Just like in men the hormone DHT appears to be at least partially to blame for the miniaturization of hair follicles in women suffering with female pattern baldness. Heredity plays a major factor in the disease.
     
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  3. sculptor Valued Senior Member

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    swimming comes to mind
    no head lice?
     
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  5. sideshowbob Sorry, wrong number. Valued Senior Member

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    Evolution doesn't have "intentions". It's about what did work, not anticipating what will work.

    A more appropriate question would be: Why is male pattern baldness preserved?
     
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  7. etherometer Banned Banned

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    Scissors and razors comes to my mind. In the same way warm clothing was supplanting the need for us to produce body hair.
     
  8. etherometer Banned Banned

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    I agree. Sexual selection can't explain why genetics is a major factor on androgenic alopecia in women.
    There are very few mature sex symbols exhibiting baldness: Bruce Willis, Michael Stipe, Michael Jordan, Jason Statham.
     
  9. sideshowbob Sorry, wrong number. Valued Senior Member

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    I would rephrase that as "quite a few". Baldness doesn't seem to be a great obstacle to either getting the chicks or getting the big bucks.

    A related question would be about shaving: Why is it that men who shave their faces (to look more like women) can contribute to the gene pool?
     
  10. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member

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    Sir Patrick Stewart and Sir Ian McKellen comes to mind (older, balding, and still damn amazing people... I know several women that swoon over em hehe)
     
  11. Arne Saknussemm trying to figure it all out Valued Senior Member

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    Maybe the evolutionary advantage is that females find male baldness attractive. Did you ever think of that?
     
  12. etherometer Banned Banned

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    Try to imagine Bruce Willis, Michael Stipe and Patrick Stewart with hair grown on the sides. Would they still looking attractive to women? A slightly more hippie style would resemble the Krosty hairstyle.
     
  13. wellwisher Banned Banned

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    Baldness usually occurs later in life, and therefore does not always impact early breeding/selection decisions. Most bald men had hair at 16 years old, so baldness would not be a factor in early breeding selection. It can slide under the radar during an early selection process. It is like saying why would young men select young women, who will have early menopause twenty years down the line, if she is fertile now? It will slide under the radar.

    I heard that male baldness is connected to too much testosterone, combined with not enough enzymes in the hair follicles to deal with it. The result leads to boldness. Women would be naturally attracted to males with high natural testosterone, with the baldness coming after the selection attraction. The lack of the enzyme will be passed forward since it remains hidden during early selection.

    This brings up an angle of evolution, that point out a conceptual problem with the one size fits all theory of natural selective and selective advantage. Baldness suggests many things are carried forward, beneath the radar of selection, due to genetic timing, for example. For example, many people divorce because the mate selection process did not anticipate the future well enough. They marry due to selection, but then things change and the selection becomes different. If these same people knew the other person had this hidden capacity to change in ways less optimize to them, they may not have been selected, initially. But this was not clear early, so the breeding is done and the under the radar genes persist via the children of divorce.

    Selection is often done with narrow and even shallow criteria, that does not dig very deep below the surface of all the genes. There is much genetic information that is not known based on a quick survey of output coming to the surface. The female bird may choose the male with the biggest feathers, but this is only one gene out of a thousand, many of which may not be optimized in other areas. These other genes will persist, simply due to the narrow and superficial selection process of big feathers. With humans having thousands of genes and selection based on a small percent of these, the majority of genes are not even connected to a direct selection process but slide through again and again.

    When men and women date, total truth would be like showing all your genes on a computer printout. But this is the exception to the rule, with more often than not, many things left hidden if they could have an impact on the selection process between two strangers. These hidden things will often appear after the deal is set if they feel close enough not to let this change the selection process in the future.
     
  14. etherometer Banned Banned

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    How many prominent scientists today are bald? Maybe women associate baldness with intellect?

    I can't find a convincing explanation. Especially for female baldness.

    Some men consider attractive female baldness or thin hair?
     
  15. matthew809 Registered Senior Member

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    When the cavemen are huddled around the fire, those with less hair are less likely to be engulfed in flames due to a random spark. The hair on the top of the head is more likely not to be immediately noticed burning(and subsequently extinguished), compared to hair anywhere else (that is likely to be facing the fire), due to the fact that it can't be seen by one's own eye's, and it may not be felt (until it's too late) due to the fact that heat rises. Voila.

    Sound far-fetched? Welcome to the story of evolution.
     
  16. Arne Saknussemm trying to figure it all out Valued Senior Member

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    I would say, 'Wow! Brilliant! You can't make this stuff up!' But clearly you can.

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    You ought to just admit now that you have no concept of the time frame of human evolution. You're fooling no one but yourself.
     
  17. wellwisher Banned Banned

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    The theory of evolution and natural selection makes one automatically assume that anything which persists, has a selection advantage explanation. But since baldness usually comes later in life, after the age needed for procreation, the balding genes can slide under the radar of conscious selection. Unless something shows outward manifestation early enough, that genetic feature will not be conscious enough to enter a selection decision.

    Although this is a stereo-type if a woman married for money, all other genetic considerations are less important, including baldness. Making money may have its own set of skills that give advantage in culture. But using that criteria for selection ignores other genetic features, thereby perpetuating unselected features. Birds may pick a mate based on feather color, which is a very superficial choice. Everything else under the hood, slides through, with more genes sliding through under the radar, than the feather color genes being selected.

    The idea of more under the radar than actually being selected, suggests diversity within the lion's share of hidden components. The superficial selection allows a species to narrow down into its own niche. All the birds in a species looks and acts the same, but under the hood there is far more diversity thereby making speciation more likely from these majority components.
     
  18. GeoffP Caput gerat lupinum Valued Senior Member

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    That would run a bit counter since women don't generally experience such pattern baldness, and I expect they had as much risk for being near the fire as the men. Or are you 'taking the piss'?

    I can envision a few explanations:

    i) Baldness is immaterial to female mate choice. Women don't care, or didn't early enough that the gene became reasonably common. Now it's here and although there's almost certainly some kind of mate selection against it, if it has any dominant or epistatic components, selection is likely to be slow indeed. It might never be removed from the population. If you have to choose some mate, and the are a high proportion in the population, then that's it - some proportion of all matings must include them. This doesn't prevent selection against it. Theoretically, there could even be a kind of "assortative mating" for those with baldness: women don't generally express it, but perhaps if they come from families with a high proportion of bald males, they might be predisposed to select bald males also. This would be a kind of assortative mating without similarities on an observed, quantitative scale. I don't suppose anyone has ever proposed this before for a binary trait, so maybe I'd better locate a data set quickly. A derivative of this would be no way out, where the existence of good and bad alleles on critical chromosomes - sex chromosomes, for instance - dictates a limited pool from which to draw. Maybe it's your mom's 'fault'.

    ii) Multivariate fitness. Perhaps bald men provide more resources, or are more attentive to their children, or cheat less, or have physical features that are rated as superior than those who are "haired". In such an instance, they might be an overall superior choice. This doesn't require that they have actual physical characteristics that are directly related to "hairedness" - no one is saying that they, say, run faster or something because of some kind of aerodynamic advantage the absence of hair gives them - but that pleiotropy or gene linkage might provide advantages.

    iii) Actual fitness advantage. Hell, maybe the bald do run faster! Or insert an actual direct selective advantage here: ______. It seems unlikely and/or insulting, but perhaps there's some strange selective advantage that occurred in antediluvian time that gave definitive benefits to the bald. A disease? Mites or fleas having fewer perches? Again, it seems a little condescending, but it's conceivable. (I don't think it's campfires, however.)

    iv) Simple drift. Either advantage or no advantage per se. It's closely related to i), above, but in this case simple statistical incidence permits the spread of the gene despite any advantages, disadvantages, or no advantages. Simple drift to common incidence. I'm a selectionist by heart - as some people have probably guessed - but neutral evolution via drift (see Kimura) is as real a system as anything else. Sometimes, stuff just happens.

    v) Mutation. I hate this one. New mutations for the same trait are recurring all the time? No they aren't. And even if they were, they'd be incidental, as a single individual. Some call that evolution, but statistically it's tiny, except as a generative process.

    vi) Environmental masking. Perhaps baldness is shielded by environment at times, so that whatever benefit or detriment it provides to mate choice depends on environmental conditions. Or perhaps you only get it in such conditions. This is related to ii) in a way.

    And lastly:

    vii) Non-genetic. Perhaps baldness is not genetic at all. (That isn't actually the case, but it's possible for any given binomial.)

    There are others. The general impression in the literature so far is that it is genetic. Generally I think it's considered detrimental from the perspective of the "attractive male" hypothesis, where energetically costly structures are maintained for the purposes of impressing mate with being in effect 'so good as a mate that you can afford to build and maintain such a structure'. Bright plumage, long fancy hair, doing an otherwise absurd dance. Birds of paradise are noted for this as I recall. My instructors used to compare this with showing off at the bar or the dance clubs. Various of these have been tested by better geneticists than I.
     
  19. Arne Saknussemm trying to figure it all out Valued Senior Member

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    @GeoffP
    You're onto something here. i read that 97% of women do not care if their man is bald. However, I think you are not quite correct in saying baldness comes late in life. While it is true age 20 to 30 would be rather old in prehistoric times, many men are bald or balding as early as age 20-22. It's a small point I am making, but a true one.
     
  20. GeoffP Caput gerat lupinum Valued Senior Member

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    Some are. I don't think it's that many. I knew two guys that did. Actually that raises another point that I completely missed: if baldness happens at 40+ or whatever, it's reproductively of much less importance ancestrally since ancestrally most people did die at about 40 anyway. So beyond women not caring, it may not even have mattered to earlier human mate choice based on ontogeny and death rate, and then just persisted thereafter.
     
  21. etherometer Banned Banned

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    In addition, why human hair grows endlessly? Is there any evolutionary advantage? Or was entirely a consequence of sexual selection? (rising of aesthetics). Exist any ape specie whose hair grows any few milimeters throughout their lifetimes?
     
  22. GeoffP Caput gerat lupinum Valued Senior Member

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    Presumably hair wears out and gets abraded down. Probably.
     
  23. Arne Saknussemm trying to figure it all out Valued Senior Member

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    Well if your always wearing a wolf's head hat, it certainly would! Caput gerat lupinum indeed!

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    Seriously though (okay, semi-seriously) unless you are vigororously rubbing your scalp against a rock what sort of abrasion are we talking about?

    Don't answer that! Because it's been pointed out that the other apes (the ones who aren't naked apes as we are) just grow a few millimeters of body hair throughout their lives, as do we except for the top of our heads. Also, I suppose what's true of the apes is true of other mammals.

    So why do we grow continuous hair on our heads cascading down our backs, or is some cases go bald, but even then retain the ability to grow long locks?

    I would say because it's sexy! You'll probably agree that long hair often looks good on a woman, and I can see where women might find a strapping young hunter with cascading locks and a big wooly beard appealing (see all the meat he's brought in!). And I can see where the same hunter is clever enough not to survived years and years of dangerous hunts and as a sign of his wisdom his old, bald head now appears respectable and he gets the girls that way!

    The problem is that in our modern decadence and spoiled suburban lives we have forgotten what is appealing. We have decided (probably due to shaving cream and shampoo ads) to like shaved faces and neat, close shorn hair for men, and thin, boyish bodies for women although nature tells us a well rounded woman would be the fertile one, and the dude with the stinking, blood-crusted beard would be the one most likely to sire others like himself who would ensure the clan's survival.

    And the funny old bald guy! He's a survivor, man. You've got to respect that!
     

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