Not Final!

In mathematics we often prove that some proposition is true by showing that  the alternative is false.  The principle can sometimes work in other disciplines, but it’s tricky.  You have to have a very good understanding  to know that some things are impossible (or close enough to impossible).   You can do it fairly often in physics, less often in biology.

Sometimes you can make progress on a problem just by realizing that other people are calling something impossible, but don’t understand it well enough. For example,  there were people who were sure that Neanderthals and anatomically modern humans couldn’t have interbred successfully because paleontologists had  (often) said that Neanderthals were a different species. The problem was that the paleontologists meant that  Neanderthals were a morphological species, a group whose skeletons could be distinguished pretty easily from those of AMH, but those talking about the nonexistence of gene flow took it to mean that they were a different biological species, one with which gene flow was impossible.  There was no evidence for that, and it was bloody unlikely, considering that the two groups were only separated for a half a million years or so.  Others, of course, said that humans would never have done the nasty with anything so repulsive.  I’m not supposed to call those people stupid – so I guess it’s thesaurus time:  dense, dim, doltish, dopey, dull, dumb.  Take your pick.

Back in Lord Kelvin’s day, paleontologists were pretty sure, from sedimentation rates and the geological record, that the world was at least hundreds of millions of years old.  Kelvin knew they were wrong, since he was much smarter than them (almost certainly true) and he couldn’t imagine how gravitational contraction could keep the sun going more than ten million years or so.   This was before radioactivity, mass-energy, fusion, and all that. Kelvin didn’t have a good enough understanding of the Sun’s energy production to call impossible.  He made a mistake – but he wasn’t stupid.  Arrogant, maybe.

Peter Duesberg made a fool of himself  by saying that retroviruses must be harmless to survive , since they need viable cells to replicate.  Only viruses that kill cells in the process of replication should cause disease.  However, as it turns out , the universe was not limited by his imagination.  HIV does kill cells, but infected cells are also killed by lymphocytes.

There are many other viral diseases with non-Duesbergian mechanisms.  LCM [lymphocytic choriomeningitis] only seems to cause severe effects, such as paralysis, in mice that bother to fight it (except for long-term kidney damage).   You can successfully treat those mice with immunosuppressive therapy, although I can’t see why anyone would bother, other than Hugh Laurie and Geena Davis.  You can get high levels of immune complexes (an antibody bound to an antigen)  from some viral infections [such as Hepatitis C] , and those complexes can precipitate in many organs and cause damage, most notably causing kidney failure. Although with any luck you would already died of liver cancer, another non-Duesbergian pathological mechanism. The cancer doesn’t really help the virus, obviously, but it is an accidental long-term effect of actions that do aid the virus in the short term.

For that matter, there are a bunch of retroviruses related to HIV (lentiviruses) that trash various species, usually long after infection: feline immunodeficiency virus, Visna virus in sheep, etc.

So you have to keep this in mind when you’re trying to show that genetic mechanisms, at least as the main cause of homosexuality, don’t work – biology is complicated.  Quite likely you’d have to put more than five minutes in on it: I did.  You would wonder about heterozygote advantage, something like sickle-cell.  But you would learn that you need a big advantage in order to generate a high frequency of a trait that reduced fitness so much – and big advantages are hard to find.  The only known cases of such strong heterozygote advantage in humans  are all defenses against falciparum malaria, which is a hell of a disease.  And those defenses are limited to populations that spent a long time exposed to falciparum malaria – tropical and subtropical regions of the Old World. Moreover, any such gene would have an easily recognizable Mendelian family pattern , even if it had partial penetrance for some  reason – and homosexuality does not.  You might consider sexually antagonistic genes, or alleles that cheat at meiosis like the t-allele in mice (although they are rare) – but recent GWAS studies rule them out.  Indeed, there is no gene that explains more than a tiny smidgen of the story: you know that, if you keep track of the literature.  That fact pretty much rules out all the genetic scenarios.  Which is not to say that genetics does not have some influence, but hell, that’s true of everything.  I’m sure that there were heritable factors that influenced the probability that you’d die on Omaha Beach (ones that affected height, for example) but the true causal explanation is what we usually call the German  theory.   You can land there today and, without Germans, your chance of having your head removed by an 88 millimeter shell is practically zero.

You might note the obvious similarity between gay men and worker bees, and think about kin selection, except that there is no such similarity.   Gay men are not super-avuncular.  Talking about all their special help to kin is exactly like talking about the many fitness benefits of male lactation in humans –  a fascinating story, except for the fact that it never happened.  What would you call a biologist who publicly advocated a theory whose key mechanism was based on guy milk?

If you knew the MZ twin concordance, which is around 25%, you’d already know that some environmental factor had to be the main cause.  If you knew history, let alone microbiology, you’d wonder about pathogens, because they have caused most of the common fitness-reducing syndromes.  As for the notion that hosts would surely evolve resistance  –  microorganisms typically evolve a bit faster than we do.   A bacterium can go through thousands of generations in a year.

You need to do a fair amount of spadework to make the case against a genetic cause.  Even then, you can’t perfectly sure.  It’s not like math. There’s always the possibility that there’s an undiscovered genetic phenomena that doesn’t have a name yet, not yet even a twinkle in someone’s mind’s eye.  As Haldane would have said, things may be queerer than we can suppose.  But that’s not the way to bet.







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70 Responses to Not Final!

  1. misha says:

    what’s the actual different rate in reproduction in homosexuals? I get the impression a lot of them go out of their way to have children despite not being able to with their partner. Obviously it’s way lower than hetero folks but certainly amounts greater than zero make the genetic theorem a lot more plausible.

    • gcochran9 says:

      If it’s way lower than breakeven, which it is, it’s impossible.

      If you get the impression that a lot of them go out of their way to have children – well, I’ll let misdreavus speak on that…

      • Leonard says:

        It’s clear that it’s way lower than breakeven now. And probably has been ever since the sixties. However, before that, I’d suggest that the rate was far higher. We read of unhappy marriages in Victorian times; I bet that one or the other spouse being homosexual was among the causes. Or consider arranged marriages, where procreation and familial alliance are the primary goals, not the happiness of the individual.

        Of course, what we’re talking about here is not the causation of homosexuality, which still must be largely environmental — just 25% similarity of identical twins is strong evidence. What is at issue is the nature of the environmental cause. If homosexuality has always been terrifically injurious to fitness, the cause must be modern. If not, it can be more ancient, possibly including genes to a minor degree.

      • misdreavus says:

        Leonard, do the math. In the very long run, what’s the difference between a 5% average loss of fitness, and an 80% loss of fitness? Not very much. Under such circumstances, the odds of any number of “gay genes” even drifting towards a moderately low frequency in a population with an effective size above ten thousand is zero.

        And you don’t have to appeal to higher fitness in the past to explain why homosexuality is heritable at all – heredity influences just about *every* behavioral outcome, including the color of the necktie you chose to wear this morning, yet I know the distinction between proximate and distal causes.

    • misreavus says:

      I assure you, this instinct does not exist. If you are young, attractive, (white), and gay in your twenties and thirties, you can either spend night after night meeting similarly attractive men at bars and nightclubs, party until your feet have erupted in blisters, and wake up a weekend a month in a stranger’s bed, one whose face you hardly remember from the night before.

      Or, alternatively, you can change dirty diapers and be woken several times before dawn by the ear-splitting screams of an inconsolable creature with colic. I dunno, man, it’s a hard choice.

      • gcochran9 says:

        Ginny wasn’t content with just being held when she was a baby. When it was my turn to soothe her, I’d put on a CD and dance around the living room with her (the practical side of hardwood floors), usually playing the Four Tops. One of her first words was “tops”, for music. Purest happiness.

      • greg kai says:

        This is a lifestyle not only available to gays, hetero males having enough of free time , and either extremely attractive or with quite a lot of extra cash, this lifestyle is also possible. This may be why the average age of fatherhood increased a lot in modern societies, at least for those who can have a lot of casual (or paid) sex 😉

      • Gerard Mason says:

        @greg kai:
        Ah, but you are forgetting the possibility that it may be a metrosexuobacter infection that has caused those men to behave in that way (metrosexuobacter is related to the camp-o-bacter brilliantly posited by Prof. Cochrane as the cause of homosexuality). And don’t forget geekobacter: geekobacter mathematicae infection in adolescent males has been known to result in a crippling loss of reproductive fitness that can never be cured.

      • greg kai says:

        Bummer. I may have double infection, geekobacter for sure. Metrosexbacter, not so sure. The manpurse syndrom is absent, and this is, afaik, the main symptom. A lot of (paid, but cheap) sex, on the other hand, has certainly decreased my reproductive fitness. Probably an environmental effect, although there is an epidemic-like effect among my (male) friends 😉

        More seriously, it is true that this make the lifestyle of gays not so special, but it does not mean that their fitness reduction is not huge, even compared to hetero males that are completely satisfied with the non-reproductive sex we can now have.

        However, it means that for hetero, desire for sex and desire for child will not be equivalent for fitness anymore, this may have interesting (and quick) evolutionary implications.

      • anonymous says:

        …geekobacter mathematicae infection in adolescent males has been known to result in a crippling loss of reproductive fitness that can never be cured…

        Au contraire. Geekobacter increases success in STEM fields, leading to high income, which translates toi resource provisioning capability, leading to reproduction the mid 30s through early 40s. Most geeks I know are STRONGLY heterosexual, highly sexually driven, and will work like maniacs for decades to attract a mate.

        In my social circle, geeks are MORE fertile than average… but…. admittedly, small sample size..

  2. misreavus says:

    Speaking of Duesberg, this asshole has probably contributed to the deaths of thousands, perhaps hundreds of thousands of people who were ignorant enough to heed his pseudoscience. The Thabo Mbeki administration in South Africa took him very seriously, and with disastrous consequences. (Sorry, baas, I’m afraid it’s not just a Western conspiracy. And no, you cannot cure a critically low T-cell count with magic herbs and lemon juice.)

    Am I supposed believe that Ryan White, and 50-70% of the hemophiliacs who grew up during the early ’90s all perished because of the regular inhalation of amyl nitrates? Is there some sort of party drug popular among prepubescent boys who receive regular transfusions of blood, and one that has not yet been intercepted by the DEA?

    Oh hell I see it as a form of natural selection. If you are lucky enough to live in a country where antiretrovirals are readily affordable, and you choose to forgo them just because, well, enjoy the Kaposi’s sarcoma, as well as the inevitable picket by a certain church from Topeka, KS.

  3. misreavus says:

    A few years back I had a bunch of hostile exchanges with a not-entirely-obscure blogger who was absolutely convinced that HIV was not the culprit behind AIDS. I didn’t know that much immunology at the time (and my knowledge is still a work in progress), but I knew far more than the other idiot did, and that the only thing that counts.

    Every time I read a comment on one of these pages, ostensibly by a gay male, to the effect of “THANK you for opening my eyes to the dangers of big pharma! I cut off all communications with my doctor, and tomorrow I plan to flush all my meds down the toilet”, etc. my heart sinks a little. But unlike with HIV, I am afraid there is no remedy for this variety of stupid.

    • Anon says:

      It is impossible to know everything about everything, so at some point you have to delegate your decision making to an authority. Deferring to scientific consensus is usually a good way to do this, like in case of HIV. Unfortunately with any soft science consensus is very prone to echo-chamber and self-reinforcement. At this point you are stuck with a dilemma – you can still subscribe to consensus knowing that doing so is not fundamentally different from tossing a coin or you can invest time to become an expert in the field and form an educated opinion. Combination of these approaches, where you balance effort and time also obviously works. Problem with combination approach is that your personal preconceived notions come heavily into play – I don’t think most people could help but select things they find agreeable and go from there.

      So you have someone like your “not-entirely-obscure blogger” attempting to do a combination approach, only his or her natural tendency toward conspiracy theories lead to reaching wrong conclusions.

  4. Penrosian says:

    Let’s not forget who told the neanderthal experts that it would be impossible to sequence DNA older than a few thousand years. Sounds like some of the arguments people used to give about decoherence time in certain biological structures…

  5. Exposures says:

    “You might note the obvious similarity between gay men and worker bees, and think about kin selection”

    No, I’m thinking larger scales are relevant here. This requires taking a somewhat different view of our species’ recent evolutionary history, but you’ve already helped us throw out the standard narrative. In for a penny…

  6. WT says:

    Here’s my issue with the germ theory of homosexuality: why do lesbians and gay men both look different from each other and different from heterosexuals? Not always, of course, but enough of the time that the following are good guides to gaydar: 1) A gay man may be fairly small and slight, and have rather feminine features; 2) A lesbian woman will be somewhat heavyset, with a strong jaw and squinty eyes (think Rosie O’Donnell).

    How would a germ cause men to look more classically feminine than other men, but women to look more masculine than other women?

    • Exposures says:

      “How would a germ cause men to look more classically feminine than other men, but women to look more masculine than other women?”

      It might if it happened in utero, but that’s basically the current scientific narrative (antenatal immune insult).

    • misdreavus says:

      Judging from experience, I don’t know how true that is. In fact, sometimes I doubt whether there’s any truth to it whatsoever.

      Most of the time, if you had to guess, you would fare little better than random chance – at least not when examine a representative cross section of gay and hetero men. I don’t put much stock in oddities like the 4D:2D ratio and the (purported) larger penis size in gay men – most of which, by the way, comes from self reported data.

      • WT says:

        There is no truth to the stereotype about physiological characteristics? Says who?

      • Exposures says:

        “Most of the time, if you had to guess, you would fare little better than random chance – at least not when examine a representative cross section of gay and hetero men.”

        You’re generalizing from one example (you). Considering the frequency of prosopagnosia in agoraphobes, and the strong correlation between agoraphobia and reading this blog, you’re probably a poor example of the average person, gaydar-wise.

      • misdreavus says:


        Did you even read the study in question? Look at the effect size.


        My beliefs comes from personal interactions the *hundreds* of gay men I have met in the past few years alone – agoraphobia my foot, I am quite socially active, and if there were an easy way to distinguish gay from straight men from physiological characteristics alone, I think I would have discovered it long before you. Experience tells me that men who are unusually waifish are slightly more likely to identify as gay than the average, but you don’t know if that’s a cultural affectation. The lisp certainly is.

      • Matt says:

        I think its interesting that the study upstream, as described in full here , cites fluctuating asymmetry as different in gay men from straight men, as a larger difference than feminization of shape.

        That seems in favor of early developmental disruption really, even if gays aren’t funny looking kids. And immune system function I think has some connections to asymmetry. Sex typicality also has some connections with immune system function, but it seems unlikely this is driving the sex atypical – homosexuality correlations.

        More than facially though, behaviorally, childhood sex atypicality and more feminine interests and patterns of abilities are ubiquitously reported for gays. E.g. they are the most common reported phenotypic correlate by Bailey, and Cochran seems to think he knows what he’s talking about.

        Feminine behavior being cultural makes no sense for male homosexuals (female homosexuals may be slightly different) as the preference for masculine men is massively modal in that community and is strongly reinforced by the wider community (being as feminine as gay men are, at least, is certainly not the “law of the land”). It just must feel good / right or natural to behave in this way for these men.

        misdreavus seems generally skeptical of very localized androgen response differences, in the brain. So you would expect a physical correlate, perhaps without a very strong association, but present.

        Some kind of theory where suspectability towards a gay pathogen is not even related to sex atypicality, that seems really unlikely to be correct, even if the pathogen is the true cause.

        (Feminine males and masculine females would exist because of the normal genetic load business, new mutations, because sex dimorphism is harder to evolve and the genes that make feminine males make them have feminine sisters who are more reproductively successful, and perhaps because sex atypical morphs don’t have huge fitness hits, so long as they target the right sex for reproduction).

      • Carl Lumma says:

        “misdreavus seems generally skeptical of very localized androgen response differences, in the brain.”

        Is that what misdreavus is saying? I’m not quite sure what he’s saying… only that he’s very sure of it. He seems to be aping our host, writing carelessly on topics he has no knowledge of… like the last ten years of genomics.

    • misdreavus says:

      Of course, there are obvious physical markers which can easily pinpoint a likely suspect for the “Athenian vice” – I speak of banalities like choice of apparel, hair styles, an earring in one ear, etc. (although it is becoming increasingly difficult to distinguish between gay and straight men on that basis, for obvious reasons! ) – yet none of these are strictly physiological. Odds are you are yet another sucker for confirmation bias.

    • Discard says:

      WT: Homosexuality is a behavior. If you are a man and want to have sex with men, you’re a homosexual, regardless of the cause of this desire. It stands to reason that there are a number of different reasons for this behavior, just as there are for many other behaviors.
      There was a woman who worked at a local metal supplier. She was pleasant, social able, short-haired, and had a beer belly. If a woman has a body fat distribution like a man, I’d have to guess that she got an extra shot of testosterone in the womb. Other lesbians look perfectly attractive and feminine. Is it not possible that some people are homosexual due to genetic predisposition, others to disease, and still others to cultural or family influences?

    • Anthony says:

      Any theory of homosexuality also has to consider different types of homosexuality. Lesbianism may have a different cause (or set of causes) than male homosexuality. I’m pretty certain that at least some, but not all, lesbianism is chosen, though those women who choose it may be more bisexual than average.

      Child sexual abuse seems to cause/trigger homosexuality in some of its victims, though there are (I think) too many homosexuals for them all to be victims of sexual abuse, and at least some homosexuals I know are not victims of abuse. There may be different rates of this among lesbians and male homosexuals.

      Male homosexuality can be divided at least into tops, bottoms, and versatile; one wonders how different they are. I personally think that gay male exclusive tops are, by and large, opportunistic – they’re not gay in the same way as bottoms. They’re just less picky, and find certain holes are easier for them to get access to. I’m not so sure about “versatile” – if that’s just a subset of bottom, or if there’s a significant difference.

    • Greying Wanderer says:


      “Here’s my issue with the germ theory of homosexuality: why do lesbians and gay men both look different from each other and different from heterosexuals?”

      Personally i think there’s two causes, a < 1% in utero type masculine females and feminine males cause and the rest. If true then even if the feminine faced gay men were only 20% of the total that would still skew the average.

  7. Carl Lumma says:

    Second time you’ve mentioned GWAS ruling out sexually antagonistic selection… Second time I’m asking for citations.

  8. erica says:

    Don’t know if these are the gwas studies to which he’s referring, but I think so.

    1. The 23andme ongoing study. Results first posted a few months ago in a PDF file–try accessing it by Googling genome wide association study of sexual orientation in a large web-based cohort. You’ll see a lot of 23andme hits–look for the PDF file. Sorry I can’t copy and paste the URL for the file from this device.

    2. After the results of the 23andme study, you’ll see a citing of the Sanders’ GWAS study at Northwestern. If I recall, it’s footnote #9. The $anders’ team has been conducting a GWAS of 1000 pairs of gay brothers. It’s been a several years’ study. They’ve not yet written up the results for publication but they gave results in a poster presentation at the genetics convention in SF at the end of 2012. Publication is expected in a few months.

    Neither gwas found associations of significance.

    I can’t copy and paste on this so hope I copied this link correctly–it’s the poster abstract of the Northwestern study— text/f120122263.htm

    • Carl Lumma says:

      Neither of those studies rule out sexually antagonistic selection. Evidence I know about seems consistent with it, e.g.

      • misdreavus says:

        Oh geez. How about another novel idea, that homosexuality hasn’t been selected for whatsoever? I mean if you are going to posit that genetic homosexuality is consistent with a two-locus pattern of inheritance, with one gene on the X-chromosome that confers greater fecundity on female carriers, please have the courtesy to get your facts straight from the beginning. I implore you to look up the twin-studies — the robust ones with representative sample sizes, not twin pairs recruited from gay magazines. Do find out whether or not Dean Hamer’s research has been replicated, or whether a GWAS study has found any alleles of large effect consistent with your model.

        But that’s simply too hard for some people. In either case, if you push for a hereditarian hypothesis, the media will trumpet your findings no matter how silly they are, so why bother with fact checking and evidence?

        This is exactly what I am talking about:

        In spite of its relatively low frequency, the stable permanence in all human populations of this apparently detrimental trait [homosexuality] constitutes a puzzling ‘Darwinian paradox’.

        Wrong, wrong, WRONG.

        There is no damn paradox, because it doesn’t exist in all places in all cultures.

        There. That was easy.

  9. n/a says:

    “You might consider sexually antagonistic genes, or alleles that cheat at meiosis like the t-allele in mice (although they are rare) – but recent GWAS studies rule them out. Indeed, there is no gene that explains more than a tiny smidgen of the story: you know that, if you keep track of the literature. That fact pretty much rules out all the genetic scenarios.”

    I don’t think this is true. Figure 1 in “Neurohormonal functioning and sexual orientation: A theory of homosexuality–heterosexuality” (pdf) shows a model that makes sense to me. It’s reasonable to conceive of brain masculinization and defeminization during development as quantitative traits, and like height or IQ these traits might be expected to be influenced by very large numbers of genes.

    The 23andme results certainly rule out “a” gay gene (which I don’t think any serious person would have expected), but until sample sizes are much larger they don’t rule out a role for common genetic variation in genetic susceptibility to brain masculinization/defeminization as concerns “sexual orientation”.

    Anyway, I’d certainly expect sexually antagonistic selection to be a factor — probably not enough to cause male and female distributions on sexual target selection to overlap under normal/ideal conditions, but perhaps keeping the distributions from diverging as far as they could, leaving a small fraction of each sex susceptible to sexual inversion stemming from environmental factors (which certainly could include pathogens, but probably also include things like maternal stress) and/or mutational load.

    • ziel says:

      What puzzles me about the idea of sexual orientation being quantitative in nature is that you’d expect bi-sexuality to be a lot more common. If at one end of the spectrum you see overlap of female/male attraction resulting in a complete inversion (homosexuality), how could there not be many more moving along the sexuality curve away from that total-inversion region who are readily attracted to both sexes before ending up in the pure-heterosexual population. Yet what we find is that bi-sexuality is very rare – rarer than homosexuality.

      • Jason Malloy says:

        “What puzzles me about the idea of sexual orientation being quantitative in nature is that you’d expect bi-sexuality to be a lot more common”

        A quantitative genetic model does not require a gradation in phenotype. There could simply be a threshold effect for its expression.

        I also find some sort of sexually antagonist model most compelling. I found some evidence in the GSS that male and female rates of homosexuality have an inverse relationship over time and across cultures.

        No one has apparently ever bothered to compare the cross-gender correlation of homosexuality within families (i.e. are lesbians more likely to have gay brothers than straight women?). I predict that gay men are less likely to have lesbian sisters than heterosexual men.

      • misdreavus says:

        A quantitative genetic model does not require a gradation in phenotype. There could simply be a threshold effect for its expression.

        Name one example.

      • Jason Malloy says:

        Name one example.

        You’re skeptical that there are threshold effects in the development of phenotypes?

      • misdreavus says:

        @Jason Malloy

        For quantitative traits caused by hundreds or thousands of additive alleles of small effect, where are they? You could have said spina bifida, but from the looks of it, that doesn’t look like an either-or phenotype — there are gradations in the severity of the disease, some of which are not detectable until advanced age. I remember the heritability for _that_ being less than 20%, according to Richard Lynn’s Eugenics.

        Either way, this is crap. The fitness benefit for female carriers of the gene would have be pretty substantial, and if it existed, we would know about it already.

      • Jason Malloy says:

        “The fitness benefit for female carriers of the gene would have be pretty substantial”

        There is no “the gene”. There are some genes.

        Look, there is not going to be a simple answer here. When one identical twin is gay, the other identical twin is frequently straight. This severely limits the relevance of any genetic hypothesis, but it also introduces huge theoretical problems for potential environmental variables, since twins share almost all the same exposures from the womb into childhood.

        There is some empirical evidence for the maternal immune hypothesis, and some evidence that the female relatives of gay men are different (“more feminine”?). I apologize if curious people are making limited conclusions from limited data. But if you’re trying to taking genetics off the table completely, then you’re in the wrong. There is a genetic component to this phenotype.

    • JLikens says:

      If that were true, you would expect to observe gradations of sexual orientation.

      But that’s not the case at all.

      The presentation is clearly discrete. At least among males.

  10. misdreavus says:

    Clarification for Jason Malloy: I meant a phenotype that wasn’t unusually rare (e.g. pyloric stenosis), gradated (often, a purported “threshold effect” is an artifact of the paucity of our vocabulary, or the poor reliability of diagnostic criteria), or itself a goddamn disease.

    (In that last case, we know exactly what that “threshold” is all about. Never confuse proximate and distal causes. Narcolepsy is a famous example — for nonfamilial cases, the vast majority of sufferers have a single HLA haplotype, but having the genotype is no guarantee for the onset of disease.)

    All you have stated is that heritable risk factors for male homosexuality must be polygenic with low penetrance, and that the overwhelming environmental factor (or factors) have to occur more or less at random. Huh. It seems nobody has heard of any cases where one identical twin developed paralytic polio while the other didn’t, or where monozygotic twins were highly dissimilar in their history of contagious illness, all despite growing up in the same household.

    You know what I think has better explanatory power? Disease!

  11. Jason Malloy says:

    A viral or bacterial model isn’t incompatible with heritable variation. Whatever the environmental triggers, it’s not unreasonable to think that alleles relevant in gendered behavior differences probably interact in the creation of the phenotype (e.g., in augmenting prenatal hormonal exposures). Maybe this is wrong. Maybe its just genes involved in immunity.

    Neither one gives us more reason to believe that the existing genetic variation related to homosexuality has to create a behavioral spectrum with various shades of bisexuality.

  12. The fourth doorman of the apocalypse says:

    The issue of the etiology of homosexuality comes up here frequently, and I wonder to what extent it really matters whether homosexuality is caused by a pathogen or genetics.

    I see a parallel with Galileo (although perhaps I am mistaken) in that it seems to me that at the time of Galileo’s persecution it did not really make any difference to the lives of anyone on the planet whether or not the earth went around the sun or what.

    The vehemence of the discussions seems related to fear by one set of authorities that they will be replaced by another set of authorities (scientists), although of late, the state seems to have moved to control science and cloak itself in the mantle of scientific authority as well.

    However, as someone who likes to understand how things work I can appreciate the need by some people to come up with alternative and better explanations.

    • Greying Wanderer says:

      “The issue of the etiology of homosexuality comes up here frequently, and I wonder to what extent it really matters whether homosexuality is caused by a pathogen or genetics.”

      Pushing people into arguing about this is a good way to educate about genetics.

      • The fourth doorman of the apocalypse says:

        It’s also a good way to divert them from what matters, like the state of the economy, the unrestricted importation of people who like to use bombs to kill others, etc.

        I am not saying that that is Greg’s intent. I rather think that the whole Gay Marriage issue is a diversion created by politicians to, hey look over there, disgusting normal people objecting to diverse behavior.

      • frost says:

        Maybe GC’s reason for raising the topic so often is to build blog traffic? That seems to be the usual result, anyway.

      • erica says:

        It’s a good topic for lots of reasons, but especially because it gets people thinking about the causes of illnesses. The tendency for many, including one’s family doctor, the person of science closest to most people, is to cavalierly conclude about many things, “Oh, it (the “it” is a veritable cornucopia of maladies or traits) is genetic” when “it” is likely to be no such thing.

        Not only does my vet, an internist specializing in digestive disorders, seem more up on germ theory than my own doctor, I’m convinced she’s far better educated in evolutionary science as well.

        Germ theory has made headway but my guess is the “genes made them do it crowd” still rules the money roost, yes?

        The other interesting question raised by this issue is how do we or should we define “illness.”

        Homosexuality results in reduced fitness…and so …. just what do we call something that causes that?

    • erica says:

      I probably should have used “disease” rather than “illness.”

  13. Anonymous says:

    With regard to Galileo – The Catholic Church was on the defensive because of Protestant accusations of moral and doctrinal laxity. They felt a need to demonstrate their strict adherence to religious dogma. If the Galileo affair had come up in the Miedeval Age when the religious authority of the Catholic Church was unchallenged they probably would have been more flexible.

  14. Jim says:

    Isn’t the saying about the universe being queerer than we can suppose due to Sir james Jeans not Haldane?

  15. Chip Smith says:

    I understand that the MZ concordance is now thought to be around 25% and that earlier studies — confounded by biased participant selection — set it considerably higher. What I wonder about (and this may be addressed in the literature) is the opposite bias stemming from concealed homosexuality, which I would expect to be significant for a trait that is still, albeit to a lessened degree, stigmatized. Shouldn’t the 25% estimate come with an asterisk for this reason, or is the research sophisticated enough to account for liars?

    • misdreavus says:

      Well, think about it carefully. Closeted or not, why would stigma against homosexuality _deflate_ the concordance rate for sexual orientation?

      I know the twins in the australian study were each polled separately (and anonymously), and no such stigma exists in Sweden.

  16. Pingback: linkfest – 04/21/13 | hbd* chick

  17. Is the Manolo the only reader of the West Hunt who got the Stuart Little reference?

  18. Richard Sharpe says:

    Great news. Encouragement can remove those pesky achievement gaps:

  19. Julian O'Dea says:

    I got the Stuart Little reference.

    I don’t understand the false dichotomy evident in this discussion. Genetics vs Disease. Developmental seems most likely to me, as I blogged here with an interesting example from the incidence of paraphilias.

  20. Julian O'Dea says:

    To clarify, by “disease” I meant infectious disease.

  21. Pingback: Greg Cochran’s “Gay Germ” Hypothesis – An Exercise in the Power of Germs | JayMan's Blog

  22. Tommy Young says:

    Andrea Camperio Ciani and Umberto Battaglia’s May, 2014 study in The Journal of Sexual Medicine shows just what one would suspect – self-reports of sexual attraction (i,.e., androphilia) are not reliable.

    On an explicit Kinsey scale, 2.7% of their sample declared themselves to be sexually attracted to men, corresponding to previous explicit samplings of the Italian homosexual male population. However, the sp-IAT (Sexual Preference Impliciat Association Test) identified that 11.3% of self-declared gynephilic heterosexuals showed a moderate to strong androphilia with a significant effect size (D) always below −0.2, and another 5.6% of the heterosexual sample showed no preference for females (D between −0.2 and 0).

    The Italian figure for male homosexuality in the population is consistent with a 1980’s (pre-gay-politicization era) Merck manual I have that says about 2-3 percent of the population is homosexual, Given the social stigma associated with male homosexuality, it’s not surpirising to find that same-sex attraction is underreported when self-report methods are used, It’s also reasonable to assume that “in the closet effect” is stronger in societies that repress homosexuals, regardless of whether the culture is primitive or advanced technologically, If the results of Camperio Ciani et al. can be replicated, we’ll know that at least 11,3 percent of professed heterosexual males get turned on by guys, and another 5.6 percent would just as soon look at guys as gals. I think we have a pretty good idea from this result how gay genes survive – they aren’t necessarily a big deal in reproductive fitness if guys want to buck up and play straight, There are a significant number of men who that the water in the gay pool might suits them, but prudence prohibits their plunge,.

    The “gay germ” theory has the same problem as Pons and Fleischmann’s Cold Fusion – bad measurement,

  23. Frank Holland says:

    What he says sounds plausible.

  24. Douglas Knight says:

    Why does GWAS rule out sexually antagonistic selection?

    GWAS rules out genes of large effect. Does sexually antagonistic selection require one? Why?

  25. Hatshof says:

    Gran trabajo .. Gracias

  26. Cord Shirt says:

    ,,,has no one commented on the fact that the title of this post is an Asimov reference, or are you just deleting such comments as off-topic?

    I imagine he’ll be pleased with the new application. 😉

  27. Thiago Ribeiro says:

    “If you knew history, let alone microbiology, you’d wonder about pathogens, because they have caused most of the common fitness-reducing syndromes.”

    OK, gay bugs, then.

  28. Pingback: Greg Cochran’s “Gay Germ” Hypothesis – An Exercise in the Power of Germs – Saffron Storm Trooper

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