Group Selection (and homosexuality)

You can imagine situations in which natural selection would favor an increase in frequency for a trait that aided group survival while hurting individual reproductive success – but it’s not all that easy. Here’s the problem: imagine a situation in which some individuals in the group have an allele that causes them to fight in a way that saves the collective – the catch is that some get killed in the process. Members of the tribe that don’t have this allele are saved as well, but they don’t pay the price. At the end of this fight, the frequency of the self-sacrificing allele has gone down, not up. So how can the altruistic allele hang around? How would it ever have become common in the first place?

If the altruistic act (defined as one that increases the fitness of another individuals while reducing personal fitness) is aimed at close relatives, an altruistic allele can succeed. As Haldane once said, “I would lay down my life for two brothers or eight cousins”. It’s called kin selection. Close relatives are more likely to carry a copy of that same altruistic allele than the average bear, so altruistic acts focused on close relatives can pay off – can cause the causal alleles to increase in frequency. This is particularly so if circumstances allow very big payoff from altruistic acts, for example, species that nest in cavities. Successful defense of a breach in the nest is tactically easy, rather like Horatius at the bridge, and greatly increases the fitness of many relatives.

You also see a kind of altruism among some infectious organisms. Some bacteria make a toxin that furthers the infection process. Each individual bacterium would be better off if he stopped making that toxin and relied on all the other bacteria to do it – it would save energy – but if the infection starts with a single organism, the descendants are all closely related and kin selection can favor expensive cooperation. In some cases, like cholera or diphtheria, phages carry genes that code for the production of toxins. You can think of this as a method of forcing high relatedness.

Some people have suggested that human homosexuality is an adaptation produced by group selection. I can’t see how this could possibly work. They would have to do stuff for close relatives – lots of stuff. This is a quantitative question: if they concentrated on the closest possible relatives, nephews and nieces, they’d have to cause four more to survive than would otherwise. We’re talking a behavior stronger and more effective than mother love. It doesn’t exist. And how would being homosexual help?

In some other loony scenarios, homosexuality was favored by benefits to the group as a whole. Disregarding the fact that this kind of selection is almost impossible in the first place, and that we don’t even find homosexuality in most hunter-gatherer populations, what is it they are supposed to have done to save or aid the tribe?

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119 Responses to Group Selection (and homosexuality)

  1. dantae says:

    “we don’t even find homosexuality in most hunter-gatherer populations”

    What’s your basis for saying this? Has this been looked at with methods which you consider reliable?

    • Anonymous says:

      I expect he means ‘stable, publicly validated homosexual relationships’ rather than ‘men having sex with men’ or ‘men wanting to have sex with men’

      • gcochran9 says:

        I have inside information – he means no such thing.

      • dantae says:

        I suspect so as well–and my guess would be that ‘stable, publicly validated homosexual relationships’ are much less common than ‘men having sex with men’ or ‘men wanting to have sex with men’. In either definition of the term, it’s an empirical question and one which I suspect is not trivial to answer. Perhaps it has been well studied and there is a clear answer–but based on my knowledge of the literature I would guess not.

      • jaroto says:

        Inside information? I can’t tell if you’re serious. What valid “insider information” could lead one to conclude, with confidence, that individuals in a group have a covert trait?

      • MikeP says:

        @jaroto – Cochran’s “inside information” refers to what he, Greg Cochran, meant.

      • RS' says:

        Cochran has said the hunters have no notions at all of anal sex and/or(?) gay cupidity and it has to be explained to them as a totally novel concept. Or so all the informants and workers claim.

  2. Greying Wanderer says:

    “At the end of this fight, the frequency of the self-sacrificing allele has gone down, not up. So how can the altruistic allele hang around? How would it ever have become common in the first place?”

    I can’t figure the sums but if you reduce the severity and add probability does it not work out?

    Say your group is involved in endemic close quarters clan warfare where if someone stumbles and falls to the ground their chance of getting killed goes up say 50% but if one of their comrades helps them up instead that comrade’s chance of getting killed increases by 25% instead. Now say the group has ten fighters then your chance of being the closest to someone who stumbles and the one who gets that extra risk is 1 in 9 but if *you* stumble then there’s a 100% chance one of your comrades will be the closest. So if everyone does it then everyone has on balance a better chance of survival – so in reality it’s not altruistic in that sense – it increases everyone’s fitness (if the probabilities work out).

    That doesn’t explain how it could have arisen but it might explain why it wouldn’t neccessarily decline once it had arisen.

    If the biological mechanism for helping a fallen comrade up is some kind of chemical coercion and the strength of the effect is on some kind of bell curve then if the centre-point of the curve i.e. the average level of chemically coercive faux-altruism in the group, hovers at the rational point i.e. where probabilistically speaking it increases everyone’s fitness so it’s really a faux-altruistic trait then it’s adaptive for everyone. If so then there would be heroic outliers who go above and beyond that and get killed a lot but as they are outliers (and as free riders on the other end of the curve don’t get helped up when they stumble) it evens out.

    (For example if the faux-altruistic urge counteracts fear and in a situation where the fallen comrade is facing one enemy having an urge strong enough to outweigh that fear is probabilistically adaptive but having an urge strong enough to outweigh the fear in a situation where they stumbled in the face of two enemies is maladaptive as the balance of probabilities there is you almost always die.)

    The reason for having a coercive mechanism that is probabalistically rational is it could initially develop for something else and then spread for this unrelated reason. The obvious candidate for the evolution of a *mechanism* for altruism is the mother-child relationship where free-riding is unavoidable. If this mechanism is chemically coercive i.e. it creates a compulsion similar to a mother wanting to pick up their crying child, and adaptive for mothers then the genes for that compulsion could spread around the whole group and then find a secondary and unintended purpose in war / hunting etc.

    I’m not sure this is really group evolution though. It’s more individual selection in the context of the potential benefits of being in a group requiring
    – a dangerous environment
    – an imbalance of risk where the extra risk each individual takes on is less than the risk they reduce

    It’s basically a genetic insurance policy – and crucially not technically altruistic. It appears altruistic but is only genuinely so among outliers as it increases individual fitness but only in the *context* of a group.

    Anyway, after all that the main point i wanted to make was if the above model is viable then perhaps if adaptive mother-child altruism could accidentally lead to maladaptive war altruism among outliers on the faux-altruism curve then in the same way homosexuality might be the outlier region at one extreme of another bell curve for some trait or other where the outliers at the opposite end of the spectrum are equally handicapped in reproductive terms but where the middle portions of the curve are adaptive – so the curve stays in balance.

    • misdreavus says:

      Well, let me put it to you this way.

      The coefficient of relatedness between you and your sibling is 0.5. (An altruistic gene that results in self-sacrifice would have to save the lives of at least TWO siblings in order increase in frequency throughout the gene pool — well, provided that you aren’t the only one in your family who has it.)

      The coefficient of relatedness between you and your cousin is even smaller — 0.125. You need to save the lives of at least eight cousins in order for the gene to be worth it.

      The coefficient of relatedness between you and your second cousin is even smaller — 0.00313. That’s a hell of a lot of second cousins that need saving!

      As for people in your tribe who are even less related to you than that — fuhgeddabouddit. To be fair, because all people everywhere are inbred to some degree, these coefficients might underestimate the actual degree of consanguinity between two people selected at random from a given tribe, but so what? How is that going to increase the frequency of a de novo mutation that benefits the collective?

      • gcochran9 says:

        coefficient of relatedness for 2nd cousins is 0.0313.

      • misdreavus says:

        Typo on my part. Thanks for the correction.

      • Greying Wanderer says:

        Yes but that’s the point i’m making.

        “If the altruistic act (defined as one that increases the fitness of another individual while reducing personal fitness)”

        When you pay into an insurance policy you’re not being altruistic. You’re paying a small cost to protect yourself from the consequences of a bigger cost. If enough people do it they’re all better off regardless of relatedness as long as the probabilities work out. At a particular moment in time – when you pay the premium or help up a comrade in combat – you may be being technically altruistic but it (faux-altruism) works if over time the payback – the insurance payout or being helped up when you fall in combat – is greater. As long as the extra risk you take on from helping up a fallen comrade multiplied by the number of times it happens during your main reproductive years is less than the risk of stumbling yourself and not being helped up then everyone wins.

        So what i’m saying is some of what is seen as altruism, isn’t – it’s insurance that works on the basis of probability.

        That doesn’t explain how it could evolve initially however hence the other point. I think actual altruism comes in the form of chemically coercive distress at distress and probably evolved originally for the mother-child relationship but once a *mechanism* has evolved and spreads among the population simply because it’s adaptive for mothers it might then apply to situations it wasn’t evolved for.

        So i’m not saying this is group selection. It’s individual selection (mother-child) creating a chemically coercive (distress at distress) mechanism which *in the context of a group* can provide the mechanism for a faux-altruistic group insurance policy. So the “altruism” gene bell curve that would arise isn’t in reality an altruism bell curve at all it’s a faux-altruism bell curve. It only works if the level of chemically coerced faux-altruism creates behaviour which is *below* the threshold of actual altruism. Only the *outliers* are genuinely altruistic in the technical sense (and they will die out a lot – at least in violent environments but maybe not so much in less violent environments).

        It’s really two topics at once but the related point is homosexuality maybe being the rare outlier section of some other bell curve like the very low IQ segment (and for most of history possibly the very high IQ segment as well being the maladaptive segment of the IQ bell curve. So in the same way IQ isn’t maladaptive, only the outlying segments, homosexuality may be the maladaptive outlier segment of something useful.

    • misdreavus says:

      “Anyway, after all that the main point i wanted to make was if the above model is viable then perhaps if adaptive mother-child altruism could accidentally lead to maladaptive war altruism among outliers on the faux-altruism curve then in the same way homosexuality might be the outlier region at one extreme of another bell curve for some trait or other where the outliers at the opposite end of the spectrum are equally handicapped in reproductive terms but where the middle portions of the curve are adaptive – so the curve stays in balance.”

      That’s a hell of a lot of wasted altruism.

      • Greying Wanderer says:

        An example of what i mean about homosexuality possibly being the maladaptive segment of an otherwise useful trait or set of traits.

        Say the trait bundle in question comprises
        – high sex drive
        – low discrimination (will have sex with anyone)
        – low threshold for bisexuality (really a function of the above and more a function of being anysexual rather than specifically bisexual i.e. they’re more likely to have sex with anything)

        and that bundle exists over a bell curve. The centre portion may be adaptive: high sex drive, will have sex with wife even when she has the flu and is sneezing all over them etc, whereas part of the outlying segment of the curve is where the low level of discrimination jumped to a low threshhold for bisexuality which then jumped to exlusive homosexuality.

        In other words (male) homosexuality as an outlier of high sex drive / promiscuity which is partially adaptive especially in some cultures.

        (The reason i think it’s related to promiscuity somehow – whether by bug or by gene – is there is such a strong similarity between homosexual behaviour and the heterosexual behaviour of west african descended populations.)

  3. Greying Wanderer says:

    If it is a bug then the H-G thing makes domesticated animals jump out.

  4. teageegeepea says:

    I’ve heard it claimed that there was a long tradition of homosexual sages among some plains indians. They were hunter-gatherers, so is the claim just bogus or are they an exception?

    • erica says:

      Could these have been intersexed individuals, people like the Olympic runner from South Africa, Caster Semenya? Of course, OTOH, a “long tradition” wouldn’t be likely since intersexed births would be expected to be few and far between. However, I surely do wonder if a lot of the transsexuals/transgenders (I can’t keep the two terms straight–whoops, ha ha) in a place like Bangkok aren’t intersexed, and if they are, what might that say about dense living conditions/animals and sexual atypicalities?

    • misdreavus says:

      “They were hunter-gatherers”

      I don’t know where you heard that. Seasonal cultivation of corn and squash was a mainstay of life among the Mandans, as far north as southern Canada.

      Also some plains indian tribes, curiously enough, reverted back to such an existence after the introduction of the horse by the Spaniards. I believe the Cheyenne abandoned agriculture completely to adopt a nomadic hunting lifestyle — sometime within the past three hundred years or so. (But this, too, is an artifact of the Columbian exchange. American bison were, in all probability, nowhere near as numerous as they were before the decimation of their human predators from European diseases.)

      Then again, if you are in charge of domesticated animals, you aren’t really a hunter-gatherer to begin with, are you? In the same mold, a lot of things we take for granted about American Indian societies are recent artifacts. I don’t know if the “Two-Spirit” tradition happens to be one of these.

  5. Himler says:

    “the frequency of the self-sacrificing allele has gone down, not up”

    Allele? Homosexuality is epigenetic.

    • erica says:

      You do understand that this claim of epigenetic origin is based on a model? However, at least the researchers are anxious for their model/hypotheses to be tested, which is what science should do:

      * ” ‘We’ve found a story that looks really good,’ he says. ‘There’s more verification needed,
      but we point out how we can easily do epigenetic profiles genome-wide. We predict where the epi-marks occur, we just need other studies to look at it empirically. This can be tested and proven within six months. It’s easy to test. If it’s a bad idea, we can throw it away in short order.’ ”

      *http://www.usnews.com/news/articles/2012/12/11/scientists-may-have-finally-unlocked-puzzle-of-why-people-are-gay

  6. Anon1 says:

    I brought this up in the last post about homosexuality and it was ignored. While not a specialist in the study of sexuality, I am under the impression that homosexuality is primarily the result of improper amounts of testosterone on a developing fetal brain. When a child is conceived, it automatically begins to develop a female patterned brain. If they child has received the chromosome that is required for male hood, the brain undergoes several unique development stages. Stages that primarily explain why men and woman are different. If at any point this male developing brain receives too little testosterone, if adapts female characterizes, such as a high voice, being physically unintimidating, “effeminate” in mannerism, and possibility homosexuality.

    The same rings true for women. If their developing brains get an usually high dosage of testosterone, their brain may undergo one or more of the unique developmental stages reserved for men, thus imparting male characteristics which could lead to same sex attraction.

    • gcochran9 says:

      There is not much evidence that this is the case.

      • Anon1 says:

        Hmm, I read it in a book entitled “Brain Sex,” so I can only parrot their arguments. But if there is little evidence to support it, why do homosexual men have so many female characteristics? Why do their brain scans resemble that of a strait woman?

      • Anon1 says:

        What about Turner’s syndrome? Women afflicted by it receive virtually no testosterone during fetal development and thus characterize every stereotype we have about women.

      • Himler says:

        There is actually an abundance of evidence that this is the case:

        https://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_orientation#References

        Eusocial insects also determine phenotypes via “juvenile hormone” exposure during the larval stage.

        • gcochran9 says:

          No, there is not. You’d expect other consequences from unusual hormone levels in utero and they are not seen. Moreover, it’s hard to see how you’d get MZ twins discordant for homosexuality, since they’re genetically identical and are exposed to the same hormone levels. Yet they’re discordant > 75% of the time. While on most traits, MZ twins are extremely similar.

      • Himler says:

        “You’d expect other consequences from unusual hormone levels in utero and they are not seen.”
        Autism.

        “they’re genetically identical and are exposed to the same hormone levels”
        They usually differ in copy number and methylation patterns. It’s also not hard to see why it would make evolutionary sense for one twin to be gay. Think about it.

        • gcochran9 says:

          Autism does not co-associate with homosexuality. I don’t think there’s any evidence that it’s influenced by prenatal hormonal levels, either.

          Next, I can point out a simple evolutionary strategy that works even better than one twin being homosexual: neither being homosexual.

      • Himler says:

        “I don’t think there’s any evidence that it’s influenced by prenatal hormonal levels, either.”
        Simon Baron-Cohen’s entire theory is based on fetal androgen exposure:

        “I can point out a simple evolutionary strategy that works even better than one twin being homosexual: neither being homosexual.”
        Only if we’re talking about non-eusocial species.

      • Himler says:

        “homosexuals don’t make any special contributions to the group”

        That’s just, like, your opinion, man.

        No, seriously. You’re basing that claim on very, very limited knowledge of our ancestral environment(s).

        • gcochran9 says:

          Well, in many hunter-gatherer populations – like the Aka pygmies, like the Bushmen – it doesn’t even exist. Anthropologists who have spent decades there yet see no sign of it. The locals have never heard of it and don’t even have a word for it. You have to explain it to them, and then they’re incredulous. Rightly so.

          And if you’re going to say that I don’t ‘get’ group selection, you’d better explain the mystery. Put up or be shut up. I have this cynical alternate theory that I actually know hundreds of times as much about it as you do.

    • Philippe Borin says:

      Bullshit.Why Sexual dimorphic nucleus and INAH 3 in homosexuals have same number of neurons like heterosexuals for reference: The Interstitial Nuclei of the Human Anterior
      Hypothalamus: An Investigation of Variation
      with Sex, Sexual Orientation, and HIV Status
      William Byne,and An enlarged suprachiasmatic nucleus in homosexual men D.F Swaab.
      And if these nuclei are not affected from prenatal testosterone,what this fucking prenatal testosterone DOING dude.Prenatal testosterone theory is IMPOSSIBLE.Suprachiasmatic nucleus is not sexual dimorphic in humans and in rats.The problem is from wrong interpretation of the Phoenix (1959) research.Phoenix receives INTERSEXUAL (strait female)brain.What he does is impossible outside from laboratory.Prenatal testosterone role is the regulation of APOPTOSIS(programmed cell death).Why number of the neurons in this nuclei is the same between hetero and homo?Testosterone has done its work in critical period of brain masculinisation.Please explain me which reduce prenatal testosterone?Why prenatal stress no effect on heterosexual twin?I hate pseudoscience and prenatal testosterone theory is PSEUDOSCIENCE.

  7. jaysumallah says:

    Horatius at the bridge? I think you mean Gandalf.

  8. D McAllister says:

    Greg,
    You have written about the complexity of the brain and how you think random mutations affect brain function as measured by IQ. Why can’t that also work for homosexuality? Sexual preference is obviously a brain function. What if sexual orientation, like IQ, has a normal distribution and it is affected by many different genes. Someone below a certain threshold with the right environmental factors will become a homosexual. In societies where those environmental factors don’t exist, no one becomes a homosexual.

    • misdreavus says:

      Well, sexual orientation in men doesn’t follow a Gaussian distribution. Who the hell told you this.

    • gcochran9 says:

      Too common, too deleterious. Among other things.

      • Compare:
        phenotype = exclusive preference for dick, no kids.
        To:
        phenotype = highly warlike, dies early in combat, no kids.

        In the phenotype of warlikeness, it’s self-explanatory that although the phenotype of kids/no kids is binary, the underlying neurologies are gaussian and probabilistic.

        We see lots of tail-end men who put themselves to death in war, without having kids, even though opportunities for having kids abound. This is no big fucking mystery. In all wars, particularly modern ones, the fraction of soldiers who die without procreating is vast. Yet no one struggles to explain males shunning procreation in favor of war, even though few are dumb enough to argue that a starry-eyed teenager volunteering for the WWII theatre is somehow in rational service to his genes. It’s a tail-end of a phenotype. The tails of almost all quantitative traits tend to be culled.

        It’s no big mystery either that males who are more towards the center of the bell curve on both traits procreate successfully. Males balanced between warlikeness vs cowardice, and bromance vs homophobia, are common and reproductively successful. Where’s the mystery?

      • jaroto says:

        I don’t understand this argument. If we’re looking for a common, deleterious phenotype, how about schizophrenia. Considering the lack of markers for schizophrenia identified by GWAS and other methods, the natural assumption is that there are many markers for schizophrenia with very small effects (each with odds ratios likely under 1.10).

        Would you expect the effect size of genetic markers for homosexuality to exceed that of schizophrenia? If so, any guesses as to why we haven’t identified genetic markers for homosexuality?

      • J says:

        “the natural assumption is that there are many markers for schizophrenia with very small effects ”
        jaroto,
        I’d not put too much confidence in “natural assumptions”. There are other theories out there: http://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/?single_page=true

  9. Steve Sailer says:

    In “1,000,000 B.C.,” maybe Raquel Welch’s fur miniskirt was designed for her by her gay uncle?

  10. misdreavus says:

    And heeeeere come the crazies. I think redzenegoists was the funniest so far.

  11. Andrew says:

    Let me be the chucklehead’s advocate,

    Suppose there is a tribe of paleos that consists of:
    10 females ( no feminists )
    8 males
    2 girly-guys

    In this situation there are only 8 males competing for 10 females. There is plenty to go around and if the birth of girly-guys was consistently small but enough to ensure future male-female ratios are <1, then perhaps this would somehow enable this tribe to be more cohesive and grow larger than rival tribes. I understand that larger armies tend to beat smaller ones. The trait would be group adaptive, but not individually adaptive. Perhaps the responsible gene is x-linked making females the carriers. But I thought this was not heritable.

    • Homosexuality appears in animals with no strong group rivalry dynamic. Deer and buffalo, dragonflies and fruit flies. Most arguments for homosexuality being adaptive must rest on group dynamic arguments like the above, but it’s difficult to stretch these to the vast majority of observed animal cases, outside of tribalistic niches like sapiens and bonobos. Yet, no one feels reluctant to concede that gay fruit flies aren’t acting in their genetic self-interest. This imperative for justification emerges only with cute mammals.

      Deleterious developmental misfires are commonplace in biology. But no one is searching for the survival advantage of downs syndrome.

      (well, somebody out there probably is, but there I think it’s so transparent how barren this quest must be that nobody cares)

  12. observer says:

    Does anyone even have anecdotal evidence of a homosexual man saving eight cousins? I’ve known plenty and none claimed to have saved a single one. I would wager that the median number of cousins saved across the whole population of homosexuals is zero, and that we all know this to be so. Furthermore, the average number of surviving first cousins under Malthusian conditions is so low that every homosexual would have to rescue all of them, as well as his sibling, from certain doom in every generation just in order to break even, and do so without, apparently, anyone noticing. I have trouble counting above ten, but it sure looks like the math doesn’t add up for group selection unless there is a gay Genghis out there rescuing prodigious numbers of distant cousins in absolute secret.

    There’s another problem that I haven’t heard anyone bring up. If homosexuals are so beneficial to the group, then ‘homophobia’ becomes evolutionarily inexplicable. That is, if homosexuals have been selected for because of their super-altruism, then we should all want them guarding our little nephews. Which is clearly not the case. Therefore, if there isn’t a ‘gay germ,’ there has to be a ‘homophobia germ’ that causes an unnatural aversion to these super-altruists, thwarting our evolved homophilia and reducing the fitness of the infected.

    No doubt the idea of a ‘homophobic germ’ would go over quite well in public, although my guess is that homophobia is more heritable than homosexuality (has anyone checked?). All we would need to do is apply Cochran’s ‘gay germ’ logic to postulate the existence of a ‘homophobic germ,’ and we would get an instant clamor to identify the pathogen and search for the cure.

    This also suggests an interesting public relations approach for what will amount to a reductio ad absurdum proof against the idea of group selection for homosexuality. Propose instead a search for the ‘homophobia germ'; explain why it ‘must’ exist. Then intensify the clamor by claiming that not enough research money is being directed toward identifying this germ, and we desperately need to find it lest people begin to believe a pathogen is the cause of homosexuailty. You might even get a Guardian headline out of that.

  13. observer says:

    By the way, have you seen this?

    Mercury causes homosexuality in male ibises

    http://www.nature.com/news/2010/101201/full/news.2010.641.html

    “Exposure to mercury pollution could be hitting some wild birds’ reproductive prospects hard by causing males to pair with other males. American white ibises (Eudocimus albus) from south Florida that consumed methylmercury (MeHg), the most toxic and easily absorbed form of mercury found in the environment, were more likely to engage in same-sex pairings — a phenomenon unknown in wild populations of this species with no exposure to the pollutant.”

  14. Bob says:

    My gay uncle was never around when I was growing up so I don’t think he contributed a lot to my or any of my cousins, with the exception of his three daughters. Not that he was around them all that much either, as he and their mother were divorced before the oldest of them was seven. I am inclined to think it is the recent notion of exclusive gayness that is the aberration. Is there any reliable data on the reproductive success of gay men?

    • Greying Wanderer says:

      “I am inclined to think it is the recent notion of exclusive gayness that is the aberration.”

      I wonder that too. If the initial drive is promiscuity then in a promiscuous heterosexual culture that drive can be satisfied heterosexually. In a monogamous heterosexual culture where homosexuality is taboo or mostly taboo then men with that drive can’t satisfy it with one wife so either use prostitutes or other men with the same drive. In a culture with monagamous heterosexuality but where homosexuality is accepted then men with that drive could become exclusively homosexual?

      I think that would imply fewer exclusive homosexuals and more bisexuals among promiscuous heterosexual sub-populations within a culture where homosexuality was accepted.

      • misdreavus says:

        Well, for starters, you could consult the twin studies and find out if genetics contributes a lot to human variation in the Kinsey scale. It doesn’t. H^2 < 0.25, acccording to a robust study from the Australian twin registry.

        Second, you could do a five second Google search and discover if male bisexuals are common enough to support your hypothesis — or if sexual orientation exists on a continuous distribution that diminishes monotonically with deviation from heterosexuality. Neither of these are true.

    • Thomas says:

      There was a MIDUS study that looked at mean number of offspring for straights, bisexuals, and gays. However, the study counted stepkids, adopted kids, and foster kids in addition to biological kids. Straight men had about 6 times more children than gay men according to the study:

      http://inductivist.blogspot.com/2010/05/how-much-does-homosexuality-reduce.html

      • Bob says:

        Thank you Thomas, clearly my gay uncle was the exception not the rule. Much more useful than the knowledgeable telling me what a dumbass I am.

  15. Himler says:

    “close relatives”

    I really don’t think you get group selection…

  16. erica says:

    To the pathogen idea for a moment…
    There is, Dr. C, as you and Ewald pointed out years ago, some “familial clustering” to homosexuality. Reading these last two threads, I remembered what you said, and was reminded of one family to which we are close in which a gay male has a great uncle who was gay and of a family in which a mother has three sons: the first gay, the second straight, the third gay (many would call him “bi” as he was married with a couple of kids before taking off to be gay for good). The first and second born have the same father, but the third, a different father, and the third is over a decade younger than the other two.

    I recall reading Ewald state that there are bugs that stay in families, but that was the extent of his comment. I can understand transmission if there is frequent and/or close contact among extended family members like a great uncle and his great nephew, but what if there isn’t? Would we be talking then about familial susceptibility to a particular bug? Or susceptibility to certain side effects of said bug?

    Could you expand on that? Do we have a model bug of sorts for this kind of clustering over the generations? Any research that suggests that some extended families are hit harder or in a different, novel way to a bug than others? Nuclear family transmission is easy enough to understand, but if we see clustering of this trait in some families over the decades wouldn’t it mean it’s not necessarily transmission of the bug that has occurred but rather genetic susceptibility to the effects of the bug?

  17. Greying Wanderer says:

    “even though few are dumb enough to argue that a starry-eyed teenager volunteering for the WWII theatre is somehow in rational service to his genes”

    Maybe it depends when and where those genes evolved?

    Male mammals fight. They run the risk of getting injured and dying young for the chance to have a lot of offspring so in an environment where that is true it makes sense to want to fight. Male gorillas in a zoo who fight all the time are likely to be culled in favour of the more placid ones so those genes which were adaptive in one time or place becaome maladaptive in another.

    Why make them fight rather than have lots of pretty feathers? Fighting is about the most physically exhausting thing there is so making the males fights select for strength and physical health which as long as the winners father the most children keeps the whole population healthy.

    Same thing with humans. If you make the males war-like then they will effectively cull each other – hence those much bigger, stronger, healther paleo skeletons.

    Along comes farming and now having 90% war-like males becomes maladaptive – still useful in smaller doses but not so high – and the proportion of those genes slowly drops as being a warrior no longer has the same reproductive advantages as it once did. That process of breeding out warrior genes may take a long time though so the starry eyed teenager may have been in service to his genes but not “rational” service because those evolved for a different environment.

    • Surely so.

      I do not mean to argue that middle-of-the-bell-curve, warlike phenotypes are maladaptive, in archaic environments or modern ones. Rather that starry-eyed, childless teenagers getting killed in the WWII arena – which is to say, tail end phenotypes – appear maladaptive.

      My point pertains not to middle-of-the-bell-curve, successfully procreative warlikeness, but specifically to the childless outlier phenotype of warlikeness. This serves as analogy to the childless, exclusively homosexual, outlier phenotype.

      • Anthony says:

        The motivation to volunteer for World War 2 was that one would *remain* childless if one didn’t fight – men who dodged the draft or faked an injury would be seen as cowards, and the quality of wife available to them (if any at all) would be much lower, while the young man who proved himself particularly brave might significantly improve the quality of wife he might get.

        In countries more directly involved in the war, there might be a rational calculation that the odds of having children or grandchildren would be better if all the men fought than if they didn’t.

      • Certainly, warlikeness tends to result in more reproductive success than not. Hence its success.

        However, I’m not talking about that middle-of-the-bell-curve case of success, but specifically about the tail-end case of failure, where the teenager could have stayed and reproduced successfully, yet chose the suboptimal strategy of death by war in stead of having kids, and without protecting his kin.

        Such maladapts abound at the tail-end of the phenotype. Young men are famous for tending to get killed unwisely, and (from a gene-propagation perspective) irrationally.

        The point being, they’re both
        1. uncontroversially maladaptive strategies
        2. no big fucking mystery
        Because they’re tail-ends of an adaptive phenotype.

        • gcochran9 says:

          I need a special typeface to indicate sarcasm. Look, sexual orientation fails a a lot, even though you know it has to be simpler, present a smaller mutational target, than your liver or eyes. It’s anomalous. If you don’t think carefully about this, you generate wrong explanations. For example, once upon a time, when kuru was devastating the Fore tribe in New Guinea, some geneticist suggested that it must be genetic. That was absurd. How the hell was a lethal gene ever supposed to have become that common?

          Look at the selective pressure against homosexuality – multiply the prevalence by the reduction in fitness. It’s comparable to the sum total all known Mendelian diseases. It makes no sense. it’s an anomaly. Do the numbers!

      • You’re replying to my post further below, right?

        In your “The neat thing about your notion is that it explains anything” comment, your sarcasm towards Dan was in no need of typesetting, ;-) I replied on the assumption that you were refuting him.

        The “developmental disorder hypothesis” (DDH) is hard to falsify, yeah. But the same might be said about a DDH for trisomy. Yet in the case of trisomy, DDH is correct.

        The “infectious agent” hypothesis, conversely, is essentially a variant of the DDH. It simply postulates that DDH, in some cases, is catalyzed. It might also be the case that the risk of trisomy or cancer is increased by a disturbance from an infectious agent. But the case remains strong that trisomy and cancer are:

        1. maladaptive
        2. difficult to select into elimination, since they’re systemically inherent
        3. likely to be probabilistic tail-ends of otherwise adaptive traits (senescent fertility, in the case of trisomy, and regenerative capacity, in the case of cancer, to boil it down).

        In both cases, the maladaptive tail-end phenotypes are impossible to eliminate, yet a worthwhile trade for the adaptive majority of phenotypes. One could reduce the incidence of trisomy and cancer by exclusive young-mom fertility, and reduced cell division. But these trade-offs might be more maladaptive than allowing a few tail-end failures.

      • Greying Wanderer says:

        Got you.

      • aisaac says:

        “The motivation to volunteer for World War 2 was that one would *remain* childless if one didn’t fight – men who dodged the draft or faked an injury would be seen as cowards, and the quality of wife available to them (if any at all) would be much lower, while the young man who proved himself particularly brave might significantly improve the quality of wife he might get.”

        Not true. He could lie about it after the war, and it’s questionable how much good war service did you anyway. Anyway, serving in the rear with the gear would be adequate to avoid the coward stamp even if lying wasn’t an option, but we still see people volunteer to be commandos.

        My dad worked at a big bakery in the 50s. He said the guys who had avoided service in the war had advanced their career and become upper management while the guys who served had their careers stagnate.

        • gcochran9 says:

          On average, military service reduced lifetime income. I guess it’s hard to explain why my Dad volunteered, or why his brother Dean worked to get into combat, instead of the gunnery training post where they wanted him to stay (shot down on his first mission over Germany). Or why my uncle Don Bolin paid to have his hernia fixed so that he could get into the infantry and fight in Normandy.

          On the other hand, uncle Frank joined the Navy, but I doubt if he actually asked to be on a DE, fighting the Yamato, in the Battle Off Samar.

      • Perhaps about as hard to explain as why we’re on an internet discussion board with zero probability of getting laid. Almost all sapiens behavior in modern environments is maladaptive.

  18. Greying Wanderer says:

    misdreavus
    “Well, for starters, you could consult the twin studies…Second, you could do a five second Google search and discover if male bisexuals are common enough to support your hypothesis — or if sexual orientation exists on a continuous distribution that diminishes monotonically with deviation from heterosexuality. Neither of these are true.”

    Among which populations? There are dramatic differences in the threshold for male-male relations in prison between different ethnic groups (anecdata on my part but it may have been studied somewhere). It’s not a function of bisexuality imo. It’s a function of promiscuity and a different set of thresholds. Almost none of the men involved will consider themselves bisexual.

    (Also seemingly unconnected but perhaps not there are dramatic differences in the rate of rape of very elderly women.)

    I’m not against the gay bug idea but whether gene or bug i think the critical place to look is the differences between populations with a promiscuous polygamous history compared to populations with a monogamous history. I think averaging populations is muddying the water.

    Secondly, also anecdatally, but maybe you have a view, i don’t think there is just one form of homosexuality. I think there’s at least two, a “female-brained” version (for want of a better word) who will make do with what they can get but who are only really attracted to straight men and the straighter the better, and a larger group who are attracted to other gay men which if true would mean two causes.

  19. Priceeqn says:

    I thought what Barbour was suggesting in his “The Kindness of Strangers” is that homosexuality is a sort of caste trait similar to a sterile cast of helpers at the (social insect) nest. However, the data are conclusive: homosexual men (at least) do not help their relatives out anymore than straight men do. Those studies were done, if I recollect, in Spain primarily.

    • Priceeqn says:

      Kindness in a Cruel World! That was Nigel Barber’s book. Worth a read, but mostly wrong.

    • gcochran9 says:

      Like we didn’t know this already. If homosexual men did worker-bee-like stuff, it could hardly be kept secret.

      • Priceeqn says:

        Exactly! I have no “awesome uncles” or whatever… I like Williams’ “misplaced reproductive effort” much more than lameass group selection arguments. I have never seen a goid candidate trait for group as opposed to individual selection.

  20. Juan Valdez says:

    “Second, you could do a five second Google search and discover if male bisexuals are common enough to support your hypothesis”

    Male bisexuals were pretty common in ancient Greece and they had a lot of children as well.

    If homosexuality is strictly a result of genetics, epigenetics or pathogens, this becomes difficult to explain.

    Partner preference is partially learned, although genes probably play a role as well. Some of the ancient Greeks were probably unable to become aroused by underaged boy thighs. But a significant number of them managed to turn bisexual. What’s up with that.

    Many people have the capacity to enjoy homosexual behaviour. Few of them are drawn to the modern, exclusively homosexual, child free lifestyle. The number drawn to that lifestyle would have been far lower in every environment prior to modern, Western societies, because in those environments children and family were more valued.

    • Juan Valdez says:

      Looking at homosexuality in the modern Western context is misleading, because it’s not just modern Western homosexuals who are refusing to reproduce. Heterosexuals in modern Western societies aren’t reproducing either, at least not at a level that is sufficient to sustain the population. That’s also inexplicable, fitness reducing behaviour.

      Homosexuality in the ancestral environment was like homosexuality in modern Afghanistan or Ancient Greece. A man enjoyed some gay sex on the side, but still had six kids. The ability to enjoy some homosexual activity on the side is probably just a “unintended” side effect of our “consciousness”,”free will” and our sexual mechanics (enjoying sex even when it’s not going to lead to reproduction).

      • Sideways says:

        “That’s also inexplicable, fitness reducing behaviour.”
        Inexplicable? No, rather easy to explain. Give us enough time and we’ll evolve past it.

    • misdreavus says:

      “Many people have the capacity to enjoy homosexual behaviour.”

      You know, I’ve heard this from educated people so often that it now starts to turn my stomach. Usually they tend to be enamored with big wigs in the humanities like Saussure or Foucault.

      To get them to shut up forever, I ask them to prove it. Prove it is true, by letting me perform fellatio on you. For some inexplicable reason, none of them ever seem to accept my offer. I wonder why?

      • JuanValdez says:

        Because they haven’t been conditioned to find you an attractive partner, obviously.

        However, in the future somebody might take you up on that offer. Today’s porn addicted heterosexual males are accidentally conditioning themselves to become aroused by homosexual stimuli.

        http://www.psychologytoday.com/blog/cupids-poisoned-arrow/201212/exposure-therapy-hocd

        “Non-conforming porn violates expectations, releases more dopamine and norepinephrine than earlier porn genres, and furnishes the extra kick that fires up sluggish (addicted) reward circuitry. A user may begin to question why he can get off to fetish porn with transsexual/gay action yet not be attracted to real sex partners who aroused him in the past.

        His brain, however, automatically begins to wire its sexual response to this novel, stimulating genre—in a classic case of sexual conditioning. As explained in an earlier post, sexuality can be conditioned to most anything, even the smell of death, so it’s not surprising that many of today’s porn users report that their porn tastes morph all over the place as their pleasure response declines.

        Now, our user may find that he can only climax to his latest (and therefore most stimulating) genre. If it’s one that he views as inconsistent with his underlying sexual orientation, the shock value is greater…and releases even more stimulating/anxiety-producing neurochemicals. His arousal is heightened, in part, by his own stress. Three guys describe their experience:

        First guy: I seriously thought I was turning gay. My HOCD was so strong at that time, I was contemplating taking a dive off the nearest high-rise. I felt so depressed. I knew I loved girls and I can’t love another dude, but why did I have ED? Why did I need transsexual/gay stuff to jolt me into arousal?

        Second guy: The scary thing is that I’ve been seeing women as crazy attractive, and men or the idea of men pretty nonsexual. As a gay man who’s pretty much exclusively had relations with other men since high school, this is kind of weird. Even when I see “ugly” ladies walking on the street, I can’t help but picture what it’d be like to have crazy sex with them right there. Will it stop? Is it reversible?

        Third guy: The first two days I had serious anxiety, almost wanting to kill myself because I lost all attraction towards any female. These thoughts make me think that I am gay, making me question what I do, what I say, making me sick. I can’t eat. I think intrusive thoughts…making me feel like I’m gay, when I know I’m not.”

        A generation of heterosexual males accidentally developing attraction to homosexual stimuli. Seems like it could be related to the mechanism that allowed the ancient Greeks to make the majority of their free men into active bisexuals.

      • albatross says:

        And yet, quite a number of men in environments with no women, such as prisons, the Royal Navy, and all-male boarding schools, have historically managed to enjoy homosexual behavior under those circumstances. I gather mostly they prefer women when they get back to civilization (defined as where women are), but it’s not like this is some unheard-of phenomenon. That suggests that there’s some flexibility in many mens’ sexual orientation, though I don’t have any numbers to say how much flexibility.

  21. Dan says:

    could it simply be nature of the beast? make 1,000 cars and 10 will have transmission troubles. make 100 humans and 10 will be gay? a byproduct of another valuable gene system going haywire.

    • gcochran9 says:

      The neat thing about your notion is that it explains anything that could ever happen, always the mark of a good theory.

      • It’s not necessarily the mark of a bad theory either, though.

        In the details, it also happens to overlap with vulnerability to the infection you propose. That’s just another route to the same, basic conclusion of maladaptiveness.

        The premise of the Darwin Awards isn’t wrong. Animal behavior is buggy.

    • The fourth doorman of the apocalypse says:

      Unless you are Government Motors, you will work to reduce the cost to you of those transmission troubles. That is, improve manufacturing processes.

      Similarly, any lineage that is susceptible to failure to mate goes out of style pretty quickly.

  22. bruce says:

    >What is it they are supposed to have done to save or aid the tribe?

    Assume most guys are dumb. Assume dumb cocky optimists hump everything, and dumb cockadroop pessimists submit. I see this in dogs. Doesn’t save or aid the tribe, or pack, but I’ve seen cocky boy dogs hump easygoing boy dogs. Dumbth is parsimonious. Maybe gay germs are shared with most mammals (because it’s in the interest of some brand of E coli?). I never saw a boy snake hump another boy snake, but if I did? I’d think: Dumb. Then, maybe, E coli.

    Mary Renault’s ‘The Last of the Wine’ has a more romantic view.

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  24. Abelard Lindsey says:

    What about transgenders/transsexuals (ladyboys, CD’s, etc.)? Would this also be due to an infectious agent? If so, would it be the same infectious agent that causes “regular” homosexuality or would it be a different agent?

  25. Greying Wanderer says:

    “Male bisexuals were pretty common in ancient Greece and they had a lot of children as well.”

    The people i’m thinking of who have a very low threshold for having sex with men (or goats or anything else) if a woman isn’t available don’t consider it to be anything to do with homosexuality or bisexuality. They see not being able to wait as them being *more* heterosexual.

    • erica says:

      I don’t have a problem believing that porn is like any other thrill-seeking experience. What seems exciting at first becomes dull and a new thrill is sought. Same with the drug user or the guy who can’t stop trying to make it to the top of Everest even though he has some little kids.

      I don’t have a problem understanding that in the case of the male sex drive, some males will turn to other males if that is all that is available (boys in a boarding schools during a developmental period of sexual exploration and competition and the absence of girls) or a prison, where most are already highly aggressive and seeking dominance and again, where women are absent.

      That there a males who would screw a hole in a rock or a goat or whatever was at hand isn’t what is puzzling.

      So, Juan Valdez, your story about straight guys accidentally conditioning themselves to an attraction for homosexual acts is not surprising, not puzzling.

      The kind of homosexuality that we are seeking to find the cause of is that demonstrated by the youngster, even at the age of a toddler, who did feel different at a very early age because he WAS different from his male peers (didn’t like rough and tumble stuff, had atypical play interests, likely exhibited some or a great many feminine behaviors, never had the typical schoolboy crush (even before puberty) on a girl or a woman but can recall having such crushes or emotional attachments to older boys or men) and then who goes on after puberty to have strong lifetime physical desires for males, never for females, and further, who bonds with or wants to bond with men emotionally/romantically.

      That type of homosexual is the anomaly, the puzzle.

  26. aisaac says:

    “imagine a situation in which some individuals in the group have an allele that causes them to fight in a way that saves the collective – the catch is that some get killed in the process. Members of the tribe that don’t have this allele are saved as well, but they don’t pay the price. At the end of this fight, the frequency of the self-sacrificing allele has gone down, not up. So how can the altruistic allele hang around? How would it ever have become common in the first place?”

    If you want that allele to hang around, you would need to give it some extra features – you not only need to be heroic, but you need to kill cowards, along with maybe the families of cowards, and those who fail to kill cowards. It would also help if females with that allele would be attracted to heroes.

    How did the Japanese do it?

    • gcochran9 says:

      And those who refuse to stay up all night killing cowards. I have no idea how the Japanese did it. But punishment of slackers was certainly possible (and happened) in tribal societies, and it opens up different possibilities.

  27. RS' says:

    > It’s no big mystery either that males who are more towards the center of the bell curve on both traits procreate successfully. Males balanced between warlikeness vs cowardice, and bromance vs homophobia, are common and reproductively successful. Where’s the mystery?

    Well, what’s the fitness of Genghis Khan? What’s the fitness of a Nebraska boy won’t show up for the draft in 1943? Fitness of a Yanamamo who turns back with a stomach complaint, as many do on any given combat expedition.

  28. RS' says:

    > Such maladapts abound at the tail-end of the phenotype. Young men are famous for tending to get killed unwisely, and (from a gene-propagation perspective) irrationally.

    That’s misleading because they get killed in acts that show mettle, cow other dudes, and impress girls. /Most/ such acts have an /expected/ fitness value above zero. A few of them (say 10%?) are performed by actual maladepts and have negative value.

    > The point being, they’re both
    1. uncontroversially maladaptive strategies
    2. no big fucking mystery
    Because they’re tail-ends of an adaptive phenotype.

    Sure, I definitely don’t deny there is some sense in this, or there seems to be. It’s not trivial to resolve. I think mainly you are just underrating mettle vis-a-vis male fitness — underrating both the fitness-enhancing powers conferred by it (cowing others) and the severity of the cost of being thought weak-willed. These fitness effects are spectacular, but are dry numbers, dry accounting, that fail to excite our imagination the way a narrative of Stalingrad or something would do.

    It also may be an error to think of a given starry-eyed phenotype who winds up dead, since you have of course foredoomed him. He could just as well turn out to have a fitness-enhancing career in mettlesome activities. Now, naturally you aren’t thick and so haven’t explicitly conceived of him as foredoomed, but when you put it the way you have, I think one’s mind can be subtly colored in that direction and away from a feeling of open contingency.

    • I think you get the gist of, and yet somehow misunderstand my argument. How am I “underrating mettle vis-a-vis male fitness — underrating both the fitness-enhancing powers conferred by it (cowing others) and the severity of the cost of being thought weak-willed.”, when I use warlikeness specifically as an example of the (typically) adaptive? Reread the post, there’s nothing in yours which does not agree with it.

      • albatross says:

        A willingness for young men to engage in tribal violence that’s individually irrational strikes me as a pretty good candidate for something group selection might conceivably work on. You certainly see modern-world phenomena driven by this, from gangs to sports fans to kids joining the army. I suspect that has to be paired with a willingness to (as Greg commented) kill anyone who’s not willing to join in with the tribal violence, or there’s a huge fitness advantage to the guys who hear their momma calling every time there’s about to be a really big fight between tribes.

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  30. sconzey says:

    Little late to the party, but why is everyone assuming homosexuals in the ancestral environment didn’t have kids?

    Prefers to have sex with men =/= sterile

    It would be terribly ironic if homosexuality started to disappear here in the developed world, now it’s become socially acceptable to be openly gay and have a relationship with someone of the same sex with no, or no biological children.

    • gcochran9 says:

      Suppose that you had a gene variant that made you have 90% as many kids as average. Suppose that for some unknown reason it had a frequency of 50% in some population 5 thousand years ago – about 200 generations. Go figure out how common it would be today. I’ll give you the formula: 0.5 * (0.9^200).

      Do you really think that someone who just wasn’t interested in women would have 90% as many children as someone who was? When other guys are willing to fight over women?

      • sconzey says:

        I had typed a huge reply here before I dug out your original post on this issue and saw that you’d already responded to most of my arguments, so that saves us some time :P

        For one thing, I hadn’t realised that MZ twins were so discordant with respect to homosexuality, and certainly the Wikipedia article is written to highlight Bailey and Pillard study.

        The thesis of a pathogen, potentially also with a genetic predisposition makes a lot of sense.

        As an entertaining aside, your comment about hunter-gatherer societies reminded me of a conversation I once had with a progressive friend, who asserted to me with a straight face that ‘homo-aversion’ in Africa, and particularly Uganda’s new anti-homosexuality law, was entirely caused by the manipulations of the American Religious Right.

        So some questions:
        1. Do you think that male homosexuality and female sexuality are similar pathologies, potentially with a common cause?
        2. Do you think that homosexuality might be a common symptom of a number of different underlying conditions?
        3. Do you know if any serious scientific research has been done into changes in sexual orientation? This would seem to me to be a bigger clue as to the biological origins of the condition than twin studies.

        • gcochran9 says:

          1. I really don’t know. Similar in being anomalies, although male homosexuality is more of an anomaly, being more common and resulting in lower fertility. Reminds me of a discussion about the possibility of lesbian ewes (compared with the dud rams): since ewes expresses sexual receptivity by just standing there (and not running away) presumably lesbian ewes would have trouble connecting.

          2. Yes, but I suspect that one (non-genetic) cause accounts for the great majority of causes. There could well be rare genetic cases. Or rare cases caused by some kind of brain injury or toxin. Considering that people have been known to lose the whole category of words for large household objects via a stroke (stoves, refrigerators, sofas) and nothing else, many things are possible.

          3. Women often seem to just change their minds. Men, not. I guess I haven’t seen anything that looked like a real, careful study of this. But then, the whole field is a swamp.

          4. “Progressive”. Huh. It has occurred to me that political/ideological movements gain by demanding that their adherents voice spectacularly ridiculous views. You haven’t really tested their loyalty if you force them to say something reasonable. “we have always been at war with Lemuria.”

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  34. Nelson Lynde says:

    Greg, there is an obvious evolutionary advantage to homosexuality you are overlooking, and this error is caused by your misunderstanding of sexual attraction as being binary (i,.e., attraction to males versus attraction to females). There is an evolutionary advantage to the trait of “attraction to male characteristics,” because many fertile females are in fact masculine looking, or at least have some masculine characteristics. This trait of “attraction to masculine characteristics”, in males, like other human traits, can be expected to fall into a normal distribution across a population, If we pick a spot on the normal distribution that’s just slightly below two standard deviations above the mean, we can easily account for the percent of homosexual men consistently identified in surveys – espcially if we consider that some small fraction of homosexual behavior may be “learned,” coercive, or situational, One example of this is heterosexual men who resort to homosexuality as a sexual outlet when imprisoned. While you might counter that the trait of “attraction to masculine characteristics” would modify itself over time so that men would not cross the gender threshold and pursue homosexual relations, this would be disadvantageous in an evolutionary sense. Nature needs the “insurance policy” provided by attraction to masculine characteristics, because warfare, plague, and natural disaster may result in a severe limitation of “feminine” sexual partners, while more hearty “masculine” females survive. If males were to turn up their nose at masculine females, the species might die. However, some men at the upper end of the distribution of this trait can only be aroused by masculine characteristics possessed at the highest possible level, i.e., by real men, The ubiquity of homosexuality across cultures (including aborigines, except where it is repressed by their society) and the consistent percentage of attraction to males exhibited within populatons makes it evident that attraction to masculine characteristics is a useful evolutionary adaptation, not a “condition” caused by microbes.

  35. Noel Giraud says:

    Monsieur Cochran,

    I enjoy your thoughts and writings.

    I have not read anything in all of your blogs about Cianni, Cermelli, and Zanzotto’s 2008 genetic model which posits that male homosexuality is genetically viable because its gene expression is sexually antogonistic, means that it increases femael fitness while decreasing male fitness.

    Here is the abstract:

    Several lines of evidence indicate the existence of genetic factors influencing male homosexuality and bisexuality. In spite of its relatively low frequency, the stable permanence in all human populations of this apparently detrimental trait constitutes a puzzling ‘Darwinian paradox’. Furthermore, several studies have pointed out relevant asymmetries in the distribution of both male homosexuality and of female fecundity in the parental lines of homosexual vs. heterosexual males. A number of hypotheses have attempted to give an evolutionary explanation for the long-standing persistence of this trait, and for its asymmetric distribution in family lines; however a satisfactory understanding of the population genetics of male homosexuality is lacking at present. We perform a systematic mathematical analysis of the propagation and equilibrium of the putative genetic factors for male homosexuality in the population, based on the selection equation for one or two diallelic loci and Bayesian statistics for pedigree investigation. We show that only the two-locus genetic model with at least one locus on the X chromosome, and in which gene expression is sexually antagonistic (increasing female fitness but decreasing male fitness), accounts for all known empirical data. Our results help clarify the basic evolutionary dynamics of male homosexuality, establishing this as a clearly ascertained sexually antagonistic human trait.

    Thank you for your educationally valuable writings.

    Noel Giraud

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