# Evolutionary advantage to beards and mustaches **URL:** \ **Category:** Factual Questions\ **Created:** [March 25, 2007, 6:21pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439 "2007-03-25T18:21:18Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [March 26, 2007, 12:15am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/21 "2007-03-26T00:15:51Z")
[QUOTE=Thudlow Boink] Maybe the question is why we have so little hair elsewhere on our bodies, or why women have less facial/body hair than men? [/QUOTE] Let me introduce you to [the Aquatic Ape hypothesis](http://en.wikipedia.org/wiki/Aquatic_ape), which postulates that our simian ancestors spent an extended period of evolution spending a great deal of time in shallow waters. ---
**Author:** ![Enter\_the\_Flagon](https://avatars.discourse-cdn.com/v4/letter/e/b9bd4f/32.png) [@Enter\_the\_Flagon](https://boards.straightdope.com/u/Enter_the_Flagon)\ **Post date:** [March 26, 2007, 12:33am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/22 "2007-03-26T00:33:09Z")
Darwin thought that male beards were an example of [sexual selection](http://en.wikipedia.org/wiki/Sexual_selection). “Charles Darwin conjectured that the male beard, as well as the relative hairlessness of humans compared to nearly all other mammals, are results of sexual selection. He reasoned that since, compared to males, the bodies of females are more nearly hairless, hairlessness is one of the atypical cases due to its selection by males at a remote prehistoric time, when males had overwhelming selective power, and that it nonetheless affected males due to genetic correlation between the sexes.” ---
**Author:** ![Carnick](https://avatars.discourse-cdn.com/v4/letter/c/6a8cbe/32.png) [@Carnick](https://boards.straightdope.com/u/Carnick)\ **Post date:** [March 26, 2007, 1:18am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/23 "2007-03-26T01:18:31Z")
[QUOTE=Colibri] There are various speculations, but no definite answer. My own best guess is that they evolved as a behavioral signal used in competitive conflicts with other males, serving to making an individual look larger, fiercer, and more intimidating. They may thus be similar to the mane of male lions. The moustache may also to some extent serve to disguise the mouth and conceal emotional state, which could be of benefit in inter-male conflict. [/QUOTE] I think this is important. Conjure up an image of a “warrior” in your mind and he’ll probably have a beard or at least long messy hair. ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [March 26, 2007, 1:43am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/24 "2007-03-26T01:43:05Z")
[QUOTE=Colibri] I’m not sure I’m getting what you are proposing. Humans in general have facial hair so that men can tell that women with an abnormal amount of testosterone are relatively infertile? [/QUOTE] To be honest, I posted this idea because I wanted to recast the notion that beards need some sort of ‘reason’ to exist. The OP could have been framed in the following way: what purpose does it serve our species for women to _not_ have beards? Men and women have common areas of body hair that are responsive to levels of circulating sex hormones. The different hormonal environments of men and women lead to different patterns of hair growth in these areas. You could think of a smooth female face as ‘female pattern facial baldness’; a signal to prospective mates that this female does not have a relatively common endocrine condition that would tend to make her less fertile. The woman is ‘switching off’ her beard by having normally functioning ovaries. So, to recast your summary a bit: Humans in general have _hormonally sensitive_ facial (and to a lesser extent, other body) hair so that women can display their fertility by keeping said hair thin and/or colorless. Note that a women doesn’t need an abnormally high level of testosterone to start becoming hirsute: in menopause the testosterone level doesn’t climb, but the estrogen levels fall, and it is the change in ratio that leads to hirsutism. Even in women with PCOS, testosterone levels can be high-normal. Now, do I take this seriously as an evolutionary explanation for beards? About as seriously as any other. Bear in mind that many, if not most, human males are from racial/ethnic groups that do not grow heavy facial hair. ---
**Author:** ![Don\_t\_fight\_the\_hypothetical](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)\ **Post date:** [March 26, 2007, 1:43am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/25 "2007-03-26T01:43:58Z")
[QUOTE=Carnick] I think this is important. Conjure up an image of a “warrior” in your mind and he’ll probably have a beard or at least long messy hair. [/QUOTE] -To our 21st aesthetic mind, but in a primal hair-pulling way this doesn’t seem to be an advantage. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 26, 2007, 2:13am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/26 "2007-03-26T02:13:26Z")
[QUOTE=ElvisL1ves] Let me introduce you to [the Aquatic Ape hypothesis](http://en.wikipedia.org/wiki/Aquatic_ape), which postulates that our simian ancestors spent an extended period of evolution spending a great deal of time in shallow waters. [/QUOTE] The aquatic ape hypothesis has pretty well been discredited these days, as per this Staff Report by bibiliophage: [Did humans descend from aquatic apes?](http://www.straightdope.com/mailbag/maquaticape.html) As the report indicates, most of the points used to support a supposed aquatic period in human evolution are highly questionable at best. In addition, most gaps in the fossil record for humans have been sufficiently filled in so as to virtually preclude an extended aquatic stage having existed. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 26, 2007, 3:33am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/27 "2007-03-26T03:33:35Z")
[QUOTE=brossa] To be honest, I posted this idea because I wanted to recast the notion that beards need some sort of ‘reason’ to exist. The OP could have been framed in the following way: what purpose does it serve our species for women to _not_ have beards? Men and women have common areas of body hair that are responsive to levels of circulating sex hormones. The different hormonal environments of men and women lead to different patterns of hair growth in these areas. You could think of a smooth female face as ‘female pattern facial baldness’; a signal to prospective mates that this female does not have a relatively common endocrine condition that would tend to make her less fertile. The woman is ‘switching off’ her beard by having normally functioning ovaries. [/QUOTE] If you are going to examine the possible evolution of a trait, you have to posit some presumed ancestral condition. Could you sketch out what you presume to be the evolutionary history of the trait? Was the ancestral condition that females had facial hair, or that they did not? Which direction did selection go? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 26, 2007, 3:50am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/28 "2007-03-26T03:50:47Z")
[QUOTE=Enter the Flagon] Darwin thought that male beards were an example of [sexual selection](http://en.wikipedia.org/wiki/Sexual_selection). “Charles Darwin conjectured that the male beard, as well as the relative hairlessness of humans compared to nearly all other mammals, are results of sexual selection. He reasoned that since, compared to males, the bodies of females are more nearly hairless, hairlessness is one of the atypical cases due to its selection by males at a remote prehistoric time, when males had overwhelming selective power, and that it nonetheless affected males due to genetic correlation between the sexes.” [/QUOTE] I am not sure exactly what Darwin said on the matter in _The Descent of Man._ There would seem to be a bit of a contradiction implicit in the way Wiki explains it. The article implies that hairlessness itself was selected for by male choice in preferring hairless females. I assume that Darwin also postulated that the male beard was due to female choice of bearded males. If males chose hairless females, while females chose hairier males (body hairiness tending to be correlated with facial hair), these two tendencies would work against each other. For reasons I mentioned above, I am skeptical that the male beard was selected for by female choice. I think it more probable that the selective force was inter-male competition. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 26, 2007, 3:54am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/29 "2007-03-26T03:54:30Z")
[QUOTE=Don’t fight the hypothetical] -To our 21st aesthetic mind, but in a primal hair-pulling way this doesn’t seem to be an advantage. [/QUOTE] The object of looking intimidating is that you don’t have to come to blows at all. ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [March 26, 2007, 5:09am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/30 "2007-03-26T05:09:05Z")
[QUOTE=Colibri] If you are going to examine the possible evolution of a trait, you have to posit some presumed ancestral condition. Could you sketch out what you presume to be the evolutionary history of the trait? Was the ancestral condition that females had facial hair, or that they did not? Which direction did selection go? [/QUOTE] Sure, what the hey. Presumably the ancestral hominids were covered in terminal hair, like modern gorillas or chimps. As they evolved away from great ape physiology in other respects, like walking upright, they also replaced much of the terminal body hair with villous hair. Both males and females show patterns of terminal hair growth to mark the onset of sexual maturity (pubic and axillary hair). With the switch from doggie-style to front-to-front sexual intercourse that went along with the change in posture, permanently enlarged female breasts evolved to simulate the genital swellings of earlier female hominids. In addition, less terminal hair on the females’ faces, coupled with increased capillary beds in the tissue of the face, allowed the face to visibly flush red, again simulating the red bottom of the ancestor. Males were more attracted to flushing, barefaced females because they resembed the engorged genital swellings of the ancestors. Now there’s a just-so story that took an ugly turn. 😉 Seriously, though, is there or has there been a culture in which female hirsutism is considered a beauty ideal? Male beauty standards have included both bearded and cleanshaven states in various times and places. That makes it seem more likely that hairlessness was selected for in women, rather than hairiness in men. ---
**Author:** ![Omniscient](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omniscient/32/3290_2.png) [@Omniscient](https://boards.straightdope.com/u/Omniscient)\ **Post date:** [March 26, 2007, 5:12am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/31 "2007-03-26T05:12:59Z")
[QUOTE=Colibri] The object of looking intimidating is that you don’t have to come to blows at all. [/QUOTE] I think the whole “threatening” argument has a giant hole in the fact that beardedness doesn’t generally come into play until an age when prehistoric humans would have been well past their competitive primes. I don’t know what the social structure is believed to have been like in the early stages but by the late twenties and early thirties when most modern males are fully able to grow a beard it seems that early man would have settling into comparative old-age. ---
**Author:** ![Don\_t\_fight\_the\_hypothetical](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)\ **Post date:** [March 26, 2007, 5:29am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/32 "2007-03-26T05:29:08Z")
[QUOTE=Colibri] The object of looking intimidating is that you don’t have to come to blows at all. [/QUOTE] -In my experience there is too big of a gap to generalize but big facial air comes later. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [March 26, 2007, 6:39am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/33 "2007-03-26T06:39:35Z")
[QUOTE=brossa] …what purpose does it serve our species for women to _not_ have beards? Men and women have common areas of body hair that are responsive to levels of circulating sex hormones. The different hormonal environments of men and women lead to different patterns of hair growth in these areas. You could think of a smooth female face as ‘female pattern facial baldness’; a signal to prospective mates that this female does not have a relatively common endocrine condition that would tend to make her less fertile. The woman is ‘switching off’ her beard by having normally functioning ovaries. [/QUOTE] This makes no sense though. If all women were originally bearded then having a beard obviously wasn’t a trait that could beccome associated with fertility. All women, fertile and infertile, had beards. A such there is no reproductive advantage to having a beard and your hypothesis fails to explain where beards came from. If women were originally beardless then a woman without abeard isn’t advertising her fertility. Rather women with beards were advertising their infertility. IOW any individual with a beard was reducing her own mate choices and reproductive potential. A such any perosn with the beard gene woudl be rpaidly selected out of the gene pool. So once again your theory fails to explain where beards came from. [QUOTE=Omniscient] I think the whole “threatening” argument has a giant hole in the fact that beardedness doesn’t generally come into play until an age when prehistoric humans would have been well past their competitive primes. I don’t know what the social structure is believed to have been like in the early stages but by the late twenties and early thirties when most modern males are fully able to grow a beard it seems that early man would have settling into comparative old-age. [/QUOTE] Nah. Health levels and adult life expectancies in HG societies were considerably _longer_ than in pre-modern agricutural socities. 30 was by no strecth settling into old age nor past any competitive prime. ---
**Author:** ![Omniscient](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omniscient/32/3290_2.png) [@Omniscient](https://boards.straightdope.com/u/Omniscient)\ **Post date:** [March 26, 2007, 7:16am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/34 "2007-03-26T07:16:57Z")
[QUOTE=Blake] Nah. Health levels and adult life expectancies in HG societies were considerably _longer_ than in pre-modern agricutural socities. 30 was by no strecth settling into old age nor past any competitive prime. [/QUOTE] Still, the fact that between the ages of 15-30 most males would have been beardless seems to argue against that line of thought. I presume that men entering their teens are in the most need of competitive advantage. This is when they would be selecting mates and positioning their rank in society. If beards were some sort of dominance play it’d probably be too late. Also, I think it presumes that these humans were too daft to know that it’s just a bunch of hair. We’re not talking about lizards or birds here. The argument that humans in competition would be affected but the size of their opponents facial hair really underestimates the reasoning abilities of those ancestors. I’m not sure many lower mammals have any displays which are used for menacing. Lion’s manes aren’t generally thought to be as far as I can tell and are instead indicators of health and fertility. Generally speaking I think most mammals are smart enough to understand that such a display is superficial, humans not excepted. Plus, let’s face it, a beard doesn’t make a human look markedly larger. If this plays a role, I think it’s more likely that it would indicate a high testosterone level which in a manner of thought would be a indicator of a dangerous rival. I don’t buy the whole “long hair and scruffy beard is scary” argument. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [March 26, 2007, 8:22am UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/35 "2007-03-26T08:22:34Z")
[QUOTE=Omniscient] Still, the fact that between the ages of 15-30 most males would have been beardless seems to argue against that line of thought. [/quote] I agree. In fact I said it first, so you agree. 😉 > [@](#): > > Also, I think it presumes that these humans were too daft to know that it’s just a bunch of hair. We’re not talking about lizards or birds here. The argument that humans in competition would be affected but the size of their opponents facial hair really underestimates the reasoning abilities of those ancestors. The big quetsion of course is just who these ancestors were. Remember that our immediate ancestor H. erectus had a brain capacity equivalent to a 6 year old. That doesn’t speak of a whole hepa of reasoning ability. Certainly the average 6 year old is easily bluffed by such things. > [@](#): > > I’m not sure many lower mammals have any displays which are used for menacing. Sure , plenty do. Ever seen a dog snarl, or a chimp bare its teeth? Those are purely menace displays and many [primates](http://lava.nationalgeographic.com/pod/pictures/normal/NGM2002_11p100-1.jpg) have brightly coloured lips, eyebrows and so forth to accentuate that menace display. The idea that humans would accentuate their menace displays really isn’t outside the relam of possibility. > [@](#): > > Generally speaking I think most mammals are smart enough to understand that such a display is superficial, humans not excepted. If that were true no human would ever have run from a goose that simply hissed and spread its wings, no human would ever have been bluffed bya dragon just because it has a frill or a brightly coloured mouth and no human woudl ever have been frightened by a leaping rat. yet all those things happen all the time. That’s why so many animals have bluff displays, it’s not for the benefit of thier own species, it’s because it works on predators. > [@](#): > > Plus, let’s face it, a beard doesn’t make a human look markedly larger. This is true. > [@](#): > > If this plays a role, I think it’s more likely that it would indicate a high testosterone level which in a manner of thought would be a indicator of a dangerous rival. I don’t buy the whole “long hair and scruffy beard is scary” argument. The problem I’m having with this is that it puts the cart before the horse. Some men with higher testosterone levels today have beards, but that’s because beards respond to testosterone levels. However why did the first person to ever grow a beard recieve sufficient advantage for the trait to be passed on? It’s not like the other people he interacted with, who had never seen a a beard before, would know it was an indicator of a dangerous rival. This is like saying that men will eventaully all develop zebra striped faces because zebra stripes corresponfd to high tetsosterone levels. The problem is that zebra stripes don’t correspond to high testosterone level because they don’t exist yet. If you met someone tommorow with striped face how could you know he is more dangerous, even if he is? With absolutely no prior exposure the group as a whole gets no reaction, and hence the possesor gets no advantage. Even if at some point thousands of year hence we have suffcieint evidence to conclude that zebra stripes correlate to danger in the meantime everyone with stripes will just be a freak. ---
**Author:** ![Omniscient](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omniscient/32/3290_2.png) [@Omniscient](https://boards.straightdope.com/u/Omniscient)\ **Post date:** [March 26, 2007, 2:20pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/36 "2007-03-26T14:20:27Z")
[QUOTE=Blake] Sure , plenty do. Ever seen a dog snarl, or a chimp bare its teeth? Those are purely menace displays and many [primates](http://lava.nationalgeographic.com/pod/pictures/normal/NGM2002_11p100-1.jpg) have brightly coloured lips, eyebrows and so forth to accentuate that menace display. The idea that humans would accentuate their menace displays really isn’t outside the relam of possibility. [/QUOTE] I was referring to plumage specifically. That is to say few mammals have hair or other decorative features for that purpose, not that no mammals menace. > [@](#): > > If that were true no human would ever have run from a goose that simply hissed and spread its wings, no human would ever have been bluffed bya dragon just because it has a frill or a brightly coloured mouth and no human woudl ever have been frightened by a leaping rat. yet all those things happen all the time. That’s why so many animals have bluff displays, it’s not for the benefit of thier own species, it’s because it works on predators. All the examples you cite are menacing activities. Plus I wager none of those things would scare a person seeking a meal, comparing the response of a domesticated modern person who certainly isn’t a predator probably misses the point. A beard would be a static feature, not something that can be puffed or accentuated in times of aggression. This makes these examples poor comparisons. If a beard were for a display of dominance it’d probably have just as much negative effect as positive in that social humans need to be able to not appear menacing as often as or more so than they need to. > [@](#): > > The problem I’m having with this is that it puts the cart before the horse. Some men with higher testosterone levels today have beards, but that’s because beards respond to testosterone levels. However why did the first person to ever grow a beard recieve sufficient advantage for the trait to be passed on? It’s not like the other people he interacted with, who had never seen a a beard before, would know it was an indicator of a dangerous rival. I don’t think the likely case is that men were selected to start growing beards. A much more likely scenario is that men stopped growing hair everywhere but their face and head. For whatever reason women and some select populations stopped growing facial hair and others did not. Answering that question is probably the path to the answer. Not semantic discussions of “who was the first guy to grow a beard”. The simplest and most appealing answer to me is that males, who did most of the hunting and adventuring, needed to hair on their face to help stay warm and protected. Since it doesn’t present any competitive disadvantage many populations in warm climates had no reason to select against it. Plus, even in desert settings facial hair can help protect from sun, wind and debris. So it’s probably as simple as that. ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [March 26, 2007, 2:35pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/37 "2007-03-26T14:35:40Z")
[QUOTE=Blake] This makes no sense though. If all women were originally bearded then having a beard obviously wasn’t a trait that could beccome associated with fertility. All women, fertile and infertile, had beards. A such there is no reproductive advantage to having a beard and your hypothesis fails to explain where beards came from. If women were originally beardless then a woman without abeard isn’t advertising her fertility. Rather women with beards were advertising their infertility. IOW any individual with a beard was reducing her own mate choices and reproductive potential. A such any perosn with the beard gene woudl be rpaidly selected out of the gene pool. So once again your theory fails to explain where beards came from. [/QUOTE] When you talk about where beards “come from”, I wonder at what point all humans were known to have hairless faces, after which time men became progressively hairier in response to some evolutionary pressure. I don’t think that such a time existed. I would bet that our ancestral hominids did have hairy faces, male and female both. Beard hair isn’t some magical stuff that is fundamentally different from other hairs. Women and children have the same number of hairs on their face as men do, and their face hair can be stimulated to form a ‘beard’ under the right hormonal conditions. My argument that female hairlessness is selected for is a simple one: in _modern_ humans, female hirsutism is correlated with decreased fertility. Not a 1:1 relationship, certainly; I can’t guess at the correlation coefficient. But significant enough that, on a population scale, men who are attracted to hirsute women will have fewer children and not pass on their fuzz fetish. In modern humans, female pubic hair development is initiated by a rise in _androgens_ generated by the adrenal glands, usually _years_ before the ovaries mature and begin cycling. I don’t know what hormonal or developmental signals operate in great apes to force the formation of coarse body hair. I don’t know whether apes suffer from ‘body baldness’ as a result of, say, cortisone exess. But let’s suppose that there is some signal, received by the ape hair follicle, that tells it to make coarse terminal hair rather than fine villous hair. From a molecular standpoint, it’s not too hard to destroy that signal pathway and/or substitute another controlling signal. Suppose we have an ancestral hominid population, with hairy faced females. Most are fertile, some are not. Some small subgroup of the females has a random mutation, or set of closely-linked alleles, that makes their facial hair more sensitive to circulating hormone levels, rather than to some other stimulus. It could have been scalp hair, it could have been skin pigment, it could have been saliva proteins, but it was facial hair. This does not affect their fertility or make them inherently more attractive to males. But if you selected 1000 random females from this population (say 900 hairy and 100 less hairy) and did a genetic/fertility analysis, you would find that, say, 90% of the hairy females were fertile while 95% of the less hairy females were fertile, _because the hormone-sensitive but infertile females were hairy, too._ Even given a smaller starting advantage, the baldfaced trait would spread through the population, and males would come to find it attractive. ---
**Author:** ![Omniscient](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omniscient/32/3290_2.png) [@Omniscient](https://boards.straightdope.com/u/Omniscient)\ **Post date:** [March 26, 2007, 2:46pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/38 "2007-03-26T14:46:39Z")
**brossa** , it might be possible that female hairlessness is simply a secondary result. As women evolved to have prominent breasts and similarly feminine qualities it would presumably dictate an increase in estrogen and a decrease in testosterone. It may simply be that the selective forces for those traits were more powerful than those which kept them hairy. The opposite might have been true in men, where the need for beards WAS a strong enough driving factor to maintain them without the pressure for displaying fertility. ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [March 26, 2007, 3:32pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/39 "2007-03-26T15:32:55Z")
[QUOTE=Omniscient] **brossa** , it might be possible that female hairlessness is simply a secondary result. As women evolved to have prominent breasts and similarly feminine qualities it would presumably dictate an increase in estrogen and a decrease in testosterone. It may simply be that the selective forces for those traits were more powerful than those which kept them hairy. The opposite might have been true in men, where the need for beards WAS a strong enough driving factor to maintain them without the pressure for displaying fertility. [/QUOTE] Fair enough. My larger point was that evolutionary ‘explanations’ for observed traits can fall into a number of pitfalls, such as the one in which every trait is assumed to convey some real benefit. Or the one that tries to take the trait of a subgroup (ie European males) and generalize it to other populations that do not share it (say, Native American males). Or the one that sees a ‘positive’ trait (the beard) while missing the ‘negative’ trait (the lack-of-beard). Having said that, though, I’m really starting to like my baldfaced fertility theory. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 26, 2007, 5:29pm UTC](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439/40 "2007-03-26T17:29:38Z")
> [@](#): > > I don’t think the likely case is that men were selected to start growing beards. A much more likely scenario is that men stopped growing hair everywhere but their face and head. I have never seen a non-human ape with a beard. Sure, the other apes are hairier than us, in general, but most of them have less head hair than we, and almost no facial hair at all, regardless of gender. So somewhere along the line, beards had to appear in a population which previously lacked them. Your argument, then, would be that at some point, beards appeared on both men and women, and then dissappeared on the women, which seems more complicated than if they had never appeared on women to begin with. [Previous page](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439.md?page=1) [Next page](https://boards.straightdope.com/t/evolutionary-advantage-to-beards-and-mustaches/397439.md?page=3)