Richard Prum explains homosexuality as the evolutionary result of selection for female autonomy

October 23, 2018 • 12:15 pm

I’ve talked a few times about Richard Prum’s new book The Evolution of Beauty, which asserts that female choice drives the evolution of male sexually dimorphic traits in nature, like fancy plumage and mating dances. That’s not in doubt, but Prum’s big claim is that what females are seeking in mates are arbitrary “aesthetic” features of males not connected with their vigor or genetic endowment. He calls this the “Beauty Happens” model, and it’s a version of the “runaway model” of sexual selection proposed by Ronald Fisher, Russ Lande, and Mark Kirkpatrick.

While Prum’s book has its good bits, it’s pretty misleading about the evolution of sexual behavior, as I pointed out on a review on this site.  As I wrote,

The book’s problem is that it is tendentious. Prum doesn’t describe the issues with his favored runaway model; he mistakenly regards it as a “null model” against which other models must be tested since, he wrongly claims, it makes no assumptions (he also claims that his null model can neither be proven nor disproven, which makes it non-scientific); he neglects other forms of sexual selection; he does not recognize that various models can work together and likely do work together; he ties “good genes” models to eugenics and even Nazi eugenics, unfairly tarring sexual selection theory with the residue of an unsavory past; and he claims that female choice of mates, which he calls “sexual autonomy”, somehow vindicates feminism in our own species.

Not only does Prum take a very one-sided view of how female mate choice evolves, but lards his book thickly with the idea that female choice in animals (mostly birds) is somehow a vindication of feminism in humans. This is, of course, known as the Naturalistic Fallacy. Not all female animals have sexual autonomy, and one could draw very different lessons from observing deer or other species in which males compete with each other, and the female gets the winner. Alternatively, there are animals like bedbugs, in which female “sexual autonomy” is obliterated by “traumatic insemination”, in which males inject sperm directly into the female body cavity, sometimes injuring or even killing her. Equal rights and opportunity for women should come from moral contemplation, not from observing what animals do. If you tie your biology so closely to your ideology or morality, you risk having to alter your ideology when we learn new facts that aren’t relevant. Should a student of bedbugs be opposed to women’s rights?

Prum also ties “good genes” models (those models in which females choose males because they have ‘good genes’ that will improve the fitness of their offspring) with Nazi eugenics. As Prum says on pp. 328-329:

“To permanently disconnect evolutionary biology from our eugenic roots, we need to embrace Darwin’s aesthetic view of life and fully incorporate the possibility of nonadaptive, arbitrary aesthetic evolution by sexual selection. . . Accordingly, evolutionary biology should adopt the nonadaptive, Beauty Happens null model of the evolution of mating preferences and display traits by sexual selection”.

That’s just ridiculous. We reject scientific theories not because they have antecedents in politically unsavory views and behavior, but because they’re not supported by the data. Connecting the good genes models with Nazi eugenics is a sleazy and musteline tactic. But it’s this connection between Prum’s theory and politics on the one hand and feminism on the other that has made his book quite popular—in my view, way too popular given its problems. I’ll have more to say about this at a future date.

Throughout the book, Prum suffers from what I call The Big Idea Syndrome (TBIS): the view that his idea has nearly universal explanatory power. (A similar victim of TBIS was Lynn Margulis, who thought that endosymbiosis explained nearly everything about biology, including the formation of new species).

One of the things that Prum proposes, toward the end of The Evolution of Beauty, is that homosexuality in humans also evolved as a result of females seeking to exercise sexual autonomy—their evolutionary “need” to have free mate choice. Prum explains this in a short  Big Think talk (transcript here):

Here’s a bit of the transcript, with my comments:

So individuals that are attracted to the same sex are frequently imagined to evolve because they provide help to their kin, that is, if there are some people in any social group that are non-reproductive because of their sexual preferences then they will be helping with raising of their nieces and nephews. This is sort of the “helpful uncle” hypothesis. The problem with that idea is that it should actually lead to a kind of asexual phenotype or an asexual behavior; it doesn’t actually describe the evolution of sexual attraction itself.

What he means at the end is “same-sex sexual attraction”. And yes, it’s possible to become nonreproductive if by so doing you actually gain fitness by taking care of your relatives (this is possible if your own sacrifice of your genes by not reproducing is more than compensated by the passing of your genes through the relatives you tend). This in fact is one explanation for the sterility of worker bees. But  Prum’s right that becoming nonreproductive doesn’t necessarily explain why the “gay uncle” is gay. He could just be asexual. And I don’t accept this hypothesis, but I’m not sure there is an evolutionary explanation for homosexuality. Nevertheless, Prum ignores evidence that is in favor of the “gay uncle hypothesis“, including some surveys in which gay men seem more willing than straight men to help relatives. (That’s only weak evidence, of course, but it’s evidence.)

Here’s his theory about how homosexuality (including lesbianism) evolves by the “Beauty happens” theory (my emphasis):

Well the aesthetic view of evolution proposes that we should put subjective experience—that is, the nature of animal and human desire—at the center of our scientific explanation. So in order to explain same sex attraction in people we need to actually ask: how could same sex attraction actually evolve?

Well, in the book I propose that human same sex attraction evolved specifically because it contributed to female sexual autonomy or to the freedom of choice. What I mean by that is that in the case of female/female sexual relationships they could contribute to female alliances that could protect females from sexual coercion by male hierarchical groups.

At the same time I propose that male/male sexual attraction could have evolved because any social situation in which males have multiple sexual outlets would have contributed to female freedom to move among individuals in that social system and to avoid coercion and sexual violence. This is a new aesthetic theory of the evolution of same-sex behavior in people, and I think it’s one that deserves really serious consideration as we move forward.You can read the book for a fuller explication.  The first paragraph explains lesbian relationships: they evolve because genes for lesbian same-sex attraction would help females bond and thus gain them female autonomy.  The problems with this are several. Why would male genes become unable to overcome the female “love bonding”? Why wouldn’t females just form coalitions without necessarily having it be a coalition based on sex? Bonobo females may show same-sex behavior, but female lions in prides don’t.

Further, if these genes are adaptive in our species, which is what Prum wants to explain, why haven’t they spread to fixation? That is, same-sex attraction in human females is not universal. (In fact, I think the evidence that it has a significant genetic component is not strong, though there is some evidence for a genetic basis of male homosexuality.) Yet it should be ubiquitous if Prum is right. So Prum’s explanation doesn’t explain why fewer than 100% of women are attracted to other women.

I suppose one could claim that the genetic influences have been overridden by culture, but that’s special pleading. Or one could claim that lesbian same-sex behavior is simply a side effect of selection for female “prosociality”, and when females are prosocial and bonding, a certain tail of that distribution will show lesbian behavior. But that’s not what Prum says: in the bolded bit above, he says that same-sex attraction was selected because it contributed to female sexual autonomy, not that same-sex attraction is a side effect of genes selected for sexual autonomy.

His argument for male/male sexual attraction is even weaker. Again, it fails to explain why fewer than 100% of males have homosexual tendencies; if the genes were useful (like the genes for female preference themselves, or for the male traits, like lion manes, which female favor), then why aren’t they seen acting in all individuals, just as Prum sees female preference and male traits? Again, given what Prum says, saying that some gay behavior is simply a side effect of females selecting for “nicer, gentler, and kinder males” who are noncoercive doesn’t fly.  Further, why wouldn’t male attraction to other males be at some disadvantage because males are wasting their reproductive effort in a way that doesn’t spread their genes? Prum may respond that females prefer to mate with homosexual males because they’re “noncoercive”, and that preference can outweigh the reproductive cost of gay males courting other males. But how this would get off the ground in an evolutionary sense defies me.

Until there are data supporting all of these ideas, Prum should do the responsible thing and keep his yap closed, or at the very least point out the problems with his own theories. That, in fact, is a recurring issue with the book: Prum doesn’t mention at all the problems with the “Beauty happens theory.”

But of course if he did that he wouldn’t get attention and book sales. In the process, however, he’s lost some of his credibility as a scientist. He’s not only in love with his Big Idea, but, like many scientists, appears to be enamored as well with the attention he gets. Take The Evolution of Beauty with a huge grain—nay, a big hill—of salt.

h/t: Tom

91 thoughts on “Richard Prum explains homosexuality as the evolutionary result of selection for female autonomy

  1. I’m sure the author has never heard of female praying mantises decapitating males during sexual intercourse. Yay for feminism?

    1. Even the website’s favored animal, the cat. Barbed penis. What’s the naturalistic fallacy we should draw from THAT? That BDSM is an evolutionary adaptation?

  2. Do lion manes and peacock tails serve any function other than attracting females? There must be other examples that would raise the same questions.

    Thinking about why things occur can produce a lot of questions and hypothetical answers that have to be run down, tested and explained.

    1. It seems unlikely for the Peacock, but I could see in the Lion where a larger mane might have an impact on other males. They must fight each other for control of a pride or dominance within male groups. I am not sure how much female choice is important in Lions – the males are very dominant and the females don’t get much choice in who is the male in the pride. But I would bet a zillion dollars that females in a pride are not loyal to the dominant male in the pride and will mate with others, so she may well be selecting large manes.

    2. AIUI the lion’s mane functions as neck armor, making it difficult for another cat to slash or choke the male lion.

      Not sure about the peacock’s tail. My basic education in the subject was that this is just a classic example of ‘runaway arms race’ sexual selection.

      1. Indeed – when the peacock is in “full bloom” (what is the correct term?) he is very susceptible to predation as he cannot easily flee. This indicates very strong sexual selection because the greater risk of getting eaten is worth the advantage to reproductive success his tail brings.

          1. You mean give the hen time to escape if they are interrupted whilst mating? What with gestation and brooding etc, there is a long time between the male’s display and the eggs getting laid.

        1. An interesting peacock fact/adaptation: they make different calls to an interested peahen than when just trying to attract a mate. But some peacock bachelors have learned to make the ‘yeah I’m the object of a peahen’s attention’ call even when they aren’t, because other peahens tend to be attracted and head towards a male that is the object of another peahen’s attention.

          It’s the equivalent of talking about your girlfriend or wearing a fake wedding ring, counting on the peahen thinking ‘if she’s interested in him, he must be a good mate.’ And evidently, it works (…for peacocks…).

        1. Jenny, the fact that manes are no complete defense of the vulnerable (carotids, v. cava, windpipe) neck, does not mean that they did not evolve as neck protection. Only a small advantage needs to be present to go in fixation. And we know that lions do fight, mainly males trying to defend their, or trying to take over a, pride. Females also attack strange males, occasionally with success.
          Human beards, anybody?

          1. I didn’t think a mane would act like a magic charm against an attack at the neck. I was being facetious, which I do a lot, and a lot of people think I’m credulous.

            1. Think I’ll pack it in. When my attempts at levity come across as ignorance so profound that I give the impression that I think a lion’s mane protects it from being wounded at the neck, then I know I have lost my ability to communicate because I don’t know a lot of things, but I sure ain’t that damned dumb.

              1. Don’t flagellate yourself. That link was extremely interesting and very surprising. I just wanted to make clear that a defense mechanism or defense adaptation need not be fullproof. You did not contend that and I’m sorry if it appeared that I did you did 😁.
                What about human beards?

    3. The “detrimental” aspects of the tail of the peacock may be adaptive for the cock’s offspring, especially the female offspring. He gives his daughters the fast muscles necessary for surviving the impediment but minus the impediment. It’s not necessarily good for him but it is good for his offspring and the gene encoding it. And if he is bumped off earlier, it may improve his inclusive fitness by improving the survival of his offspring.
      Homosexuality might be explained as a heterozygous advantage. Two copies are likely disadvantageous, but heterozygotes benefit from having the allele in the family. Though not necessarily a Mendelian inherentance pattern, homosexuality might be incompletely penetrant or advantageous through the actions of multiple genes.

      1. More directly, a successful/beautiful peacock also gives his sons the genes needed to also be successful, and his daughters the genes needed to produce such sons.

      2. More directly, a successful/beautiful peacock also gives his sons the genes needed to also be successful, and his daughters the genes needed to produce such sons.

    4. It can be difficult to distinguish between situations where the sexy son hypothesis and the handicap hypothesis have similar explanatory power.

      1. It seems to me that if the sexy attraction did not also increase lthe chances of reproductive success the trait would not increase. The two have to work together. That does not mean we can easily understand the reproductive value. But it has to be there to increase more than other traits.

        You can’t have sex in a vacuum.
        I think they taught me that in a biology class. Or maybe it was physics. Chemistry?

  3. Not entirely off topic, I seem to recall seeing data confirming that homosexuals (gay and lesbian) are over-represented in creative fields such as art, poetry, music, etc., a point that seems confirmed by casual observation. Could it be that the inability (i.e., based on sexual preference, not biology) to have children triggers a greater need to perpetuate oneself through art—i.e., too produce artistic “offspring” in lieu of children? If so, would this be considered an evolutionary survival strategy at all or am I blowing smoke here?

    1. One could completely invert that argument and say that maybe it is whatever genetic traits that make them over-represented in creative fields which leads to homosexuality.

      1. Your “leads to homosexuality” would suggest that creativity is genetic (almost certainly true) but that homosexuality is not (almost certainly not true). I guess my question is whether this hypothesis is something that evolutionary biologists such as our host have ever even considered.

        1. That doesn’t follow, mirandanga. Homosexuality can still have genetic causes* if in the presence of these “creativity genes” the trait is more likely.

          *there are few traits whose sole cause is genetic, but all selectable traits have a genetic component. To the extent there may be selection for genes for homosexuality (the question at hand) that contribution can be influenced by the expression of different genes – they co-evolve.

          1. OK,thanks, mikeyc. My question derived from my admitted ignorance about matters genetic and your answer helps. So I guess now my question would be: is there any evidence that the trait of homosexuality is in fact more likely in the presence of “creativity genes”? Or is that question also an oversimplification?

    2. Could be that not carting kids around to music lessons and sports events gives one more time to work on that symphony, too.

      1. Definitely a connection, Ken. I stopped writing poetry when I became a father and subsequently a Little League and basketball coach for my son. Other poets I know (e.g., the late William Stafford) found no conflict between time for art and time for children, and still others (e.g., Donald Hall, who died earlier this year) chose their art over their children and came to regret it. Still, I’m not sure any of this adequately accounts for the phenomenon in question.

    3. “If so, would this be considered an evolutionary survival strategy at all or am I blowing smoke here?”

      If the trait is not inherited by offspring, it isn’t an evolutionary survival strategy per se. Natural selection needs multiple generations to have an effect.

    4. Could it be that the inability (i.e., based on sexual preference, not biology) to have children triggers a greater need to perpetuate oneself through art—i.e., too produce artistic “offspring” in lieu of children?

      What about scientific?

      1. “What about scientific?”

        Interesting question, vampyricon. One difference, I think, is that science relies on good methods and deliberately avoids any emphasis on the personality of the individual engaged in the methods. Art, on the other hand always reflects the personality of the artist, much as children reflect personality traits of their parents. Hence the latter would seem more likely to serve as a “substitute” for parenthood.

        Aside from that, neither observation nor data suggest that homosexuals are over-represented in the sciences—at least I’m not aware of any.

    5. That ( overrepresentation in creative fields) could just as well have a completely social explanation.
      1- Homosexuals are a bit of outcasts, non-conformists, which might predispose to excelling in creative fields (don’t forget jews did just that in former century Europe). This point can be elaborated much further, but I just want to give the jest.
      2- Homosexuals might have ‘easier sexual lives, since there is no problems in trying to understand another sex that has quite different ideas about sex. Leaving more time for really creative activities.
      Note, this is just speculation, but it is certainly the kind of explanation social ‘scientists’ will advance.

  4. He studies birds, so he uses birds to explain human behavior! Look at monkeys and apes and the common “natural situation” is domination of females by males. Not a pretty picture for human apes! Women have gained more freedom and equality thru rationality and the evolution of cultures emphasizing equality. Best not to tie human morality to biological evolution or it’s back to the apes.

      1. No, alcohol is the remedy.

        Everyone looks better after a couple of drinks. After I’ve had a couple of drinks, that is.


    1. I’ll make a stab:

      Sex is a randomising mechanism to mix genes up (in order to make people a “moving target” and so less vulnerable to parasites; “Red Queen hypothesis”).

      If genes are mixed up to randomise which members of the opposite sex you are sexually attracted to, then it’s not that surprising if, some minority of the time, it results in attraction to something else (same sex, children, sheep, whatever) instead.

      1. Thank you Coel. I am really trying to learn and understand what seems to be a very controversial topic. I read recently that there is a theory the female body sees the male fetus as a threat and changes the chemical environment. So the more males born the more chance the next male child will have same sex attraction. Hugs

              1. 😄😃😁🙀😎 I forget people who don’t know me or read my blog do not know the history behind the hugs. I took to signing everything that way back in 2007 for reasons I won’t go into here, and just got into the habbit of doing it. I hope no one gets offened. Some do ask me not to sign off that way to them and I agree, when I can remember. Most just respond with a hug back if they respond at all. Be well. Hugs

          1. Though at one time there were data showing that the more sons a woman has the more likely the youngest one(s) was/were to be homosexual. (I say “at one time” because I haven’t pursued the matter further and that study came out some time ago. At the time I thought it particularly ironic for Catholic families [or families of any other religion that encourages copious reproduction while simultaneously demonizing homosexuality.])

            1. Some homosexuals are oldest sons. There have to be other factors at play. I am not saying there is nothing to the youngest son theory but saying there are other causes as well.

        1. I have read a similar theory. It has more to do with the mother’s immune system begins to react to testosterone after having several male babies. Somehow that affects the brain or other development of the fetus which results in homosexuality.

          I agree that there probably is no evolutionary reason but that there is something in the environment of the womb that changed the development of the fetus to increase homosexual tendencies. A lot more research needs to be done to test out these theories. I think this direction got research us Moreno promising than looking for a evolution theory.

          1. And remember, *females* are also frequently homosexual. Most of these hypotheses just focus on what might be happening with males, and don’t think much about females. As usual.

            1. It is getting a little better now. For years all the heart attack studies only involved men. Symptoms were different for women. Applies to other studies as well.

    2. Scottie, try this for an explanation…
      in ONGOING developments:

      I have been watching this for sometime now, i have never doubted my hetero orientation and subsequently have always thought there was a biological basis with a environmental, that is being human with strong cultural pressures as a complication.
      Other than that, you is what you is.

      If you do read it, take in some of the comments.

    3. The best answer is “I don’t know.” There’s probably a genetic component to it as well as a developmental/environmental one, but as far as its evolutionary significance in humans, I can’t say anything.

      1. I have often wondered whether homosexuality is a “spandrel” without genetic motivation. That is, sexual attraction and sexual reproduction evolved together (making sex pleasurable provides a motivation for organisms to engage in it) but don’t match up 100% – so there’s going to be a mismatch some percentage of the time.

        I’m not quite sure why homoexuality happens in some species but not in others, though. It seems to be more common in social species, so perhaps that is also a factor?

    4. I’m not sure now, since some well informed people on this site, including our host, appear to know or think there is indeed a genetic factor.
      In my innocence, I thought it was somehow established that homosexuality was mainly caused by exposure to particular hormonal environment in the womb at the time the brain centres determining sexual orientation are formed.
      Is that still mainstream or am I missing something?

  5. Thanks, Jerry. These posts are very interesting. The trouble with the Naturalist Fallacy is that it is easy to cherry pick examples that support any position.

  6. Different cultures have varying ideals of beauty. Most people in a culture are un-beautiful. Selection for “aesthetic” features seems to have its work cut out for it, if you get my genetic-drift.

    1. Do not agree as far as facial beauty goes. Studies I have read show more symmetrical faces are seen as more beautiful in all cultures.

      1. Yes, symmetry seems to be important in assessing beauty. I am fortunate in that both sides of my face are equally ugly. So, paradoxically, I am beauteous.

  7. “in the book I propose that human same sex attraction evolved specifically because it contributed to female sexual autonomy or to the freedom of choice.”

    Behaviors don’t evolve because they contribute to autonomy or freedom of choice. They evolve because they correlate with comparatively greater reproductive success.

    How is that supposed to work in this case?

    1. I suppose he’s trying to argue that women selected men who gave them more autonomy and freedom, i.e. men who were less “manly”, and in mating with these men and propagating these genes we got homosexual men as a by-product in some fraction of individuals that got a “super dose” of the phenotype. But this doesn’t seem to correlate with what we observe of actual female behaviour in “nature”, which is women still by and large going for aggressive, testosterone-super-charged types, rugby players, footballers etc. No – I can’t get behind this hypothesis at all. I favour hypotheses that account for *both* male AND female homosexuality with the same explanation.

  8. PCC: Nice review. I only object to your calling Prum’s work ‘musteline’. Mink, stoats, ferrets, weasels are all luvly creatures. Prum, however….

  9. I remember Eliezer Yudkowsky (who had a fantastic blog at said something about people being so enamored with their Big Idea that they think it could explain everything and end up as crackpots. Let’s hope Prum won’t end up as one of them.


  10. Jerry:

    Have you read the explanation of the evolution of homosexuality in “Sperm Wars” by Robin Baker? I’m a doctor, not an evolutionary biologist, so I don’t have your background to analyze his theory. However his explanation makes sense to me.

  11. Seems to be one of those cases where the author is unable to see the difference between “this is logically possible” and “this is likely given the observed evidence”.

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