27 April 2009

Gay Animals, Social Sex, and a Misunderstanding of Natural and Sexual Selection

  • Apr 27, 2009

Gay Animals, Social Sex, and a Misunderstanding of Natural and Sexual Selection


At first I was going to comment directly on the article, but couldn't find a place for it.
Then I noticed the article is 3 years old.
Then it occurred to me; that's exactly what my blog is for!  Remember?  Duh.

On to my comments:

This is a fascinating study and long over due research, which deserves far more attention that it's gotten for both social and scientific reasons.
However, I must partially object to the conclusions of this particular article.

It presents a false dichotomy.  None of the observed activities contradict the basic principals of Darwinian evolution, including sexual selection.  They may seem to contradict some assumed extensions of the basic mechanisms of evolution, but those assumptions are the things which must be thrown out, not the entire theory.

Sex serves a social function.  This is true not only in humans, but in a great many other species as well - generally those that are more complex, intelligent, and social.  This much is clear.
This does not mean sex is not also about reproduction.  It is not an either/or question.  To dispute that sex is primarily about reproduction, the survival of one's genes, is just plain silly.

But simply maximizing number of offspring does not necessarily lead to the greatest number of survivors a few generations down.  Increasing the quality of a few offspring, and improving the environment they grow up in can be an alternate and potentially more successful strategy for grandkids (and greatgrandkids, etc).  In a social specie where individuals are dependent on the group, any behavior which increases the cohesiveness of the group has an adaptive advantage.

Because something has a primary function doesn't mean other useful things can't be gained in addition.
By the same line which suggests non-reproductive sex is a "waste" of energy or sex cells, one could just as easily see play and all other forms of recreation, reciprocal grooming, and pretty much any activity besides acquiring food and mates as a "waste" of energy as well.
But without the assumption that non-reproductive sex is "wasteful" from a sexual selection stand-point, the entire argument breaks down.
Especially since, in the majority of cases shown, the animals being referred to as gay are actually bi.
If female macaques mate with other females 93% of the time, then they mate with males 7% of the time, which is enough to occasionally get pregnant and have offspring.  All-male sheep and giraffe orgies are in addition to mating with females, not instead (even if they are more common).  All that is required for the theories of sexual selection to hold is that when individuals do choose to mate with someone of the opposite sex, they choose the sexist partner available, and that what is considered sexy is not always directly adaptive (outside of being sexy) - such as the classic peacock-tail example.
In the last section of the article it is in fact admitted that in all the examples cited of homosexual behavior in the animal kingdom, the activity was in addition to reproductive sex, not instead.  And while that fact lead to the (otherwise baseless) claim that heterosexuality (as well as pure homosexuality) in humans is a purely social construct, what few scientific studies have been done on the subject have found quite the opposite to be indicated: in human males at least, possibly no one is bi.  Researchers have studied groups of individuals who self-report as gay, straight, and bi, and took direct measurements of physiological response to various images.  Turns out guys who claim to be bi actually show a significant (physical) preference for one gender or the other.  I wouldn't go so far as to say they are "lying" - attraction goes beyond mere sex and physiology - but as far as what is "natural" and what is "social", there isn't much evidence to support that all humans are inherently bi (interestingly enough, the same type of study finds that women - regardless of self-reporting - tend to respond to both genders).  I do know of at least one other specie which, like humans, seems to have individuals who are exclusively gay. Penguins. They share another trait with us as well, one which may be even rarer than homosexuality.  Monogamy.  And it would follow that these two go together, because if you are faithful to one partner, being bi becomes meaningless.

(A brief aside: As I was writing, Pandora played a song by Queen.  The bio caught my eye and I read a little more.  Then I took a break to watch a little of them on Youtube.  I realize I wasn't around in the 70s to see what the culture and style was like, but I am baffled that it was a secret that Freddi Mercury was gay.  I mean come on!  Never mind the hair or the leotards - wasn't the name of the band a clue??  But I digress...)

The apparent selfish/altruism conflict disappears when you consider that the unit of evolution is not the specie, not the individual, not even DNA, but the individual gene.  From an evolutionary standpoint, altruism can be seen as an individuals estimation of how many genes they have in common with the recipient of their assistance.  Any member of the same specie shares 99.5% of their DNA.  So while acting selfishly is advantageous (since you share 100% of your genetic code with yourself), as long as the benefit to another slightly outweighs the cost to yourself, altruism can be advantageous from a natural selection standpoint as well.  Someone from the same group/pack/heard is likely to have even more genes in common, a close relative even more so, and willingness to sacrifice reflects this (in humans no less than any other social specie).

Overall, the main problem is just that this view of sexuality - much like the one it is hoping to displace - is reductionist and over simplistic.  You don't need to force fit the oystercatcher into a simple theory to explain its behavior: a consistent minority of humans are polygynous too, and in those families most are cooperative with both mother's getting along and helping each other.  But in some cases personalities conflict, or jealousy is an issue. In humans you wouldn't expect anything different. It would be like calling either happy or dysfunctional (monogamous) marriages an anomaly.  They both exist.  People are like that.  Apparently so are oystercatchers. Neither conflict nor cooperation is the "true" default.  Game theory shows many many different combination can be stable.  Different things work for different situations, and for different individuals.  Claiming that conflict is an anomaly, as often as it occurs, presents the exact same problem as calling homosexuality an anomaly does.  It may not be the norm, but it isn't rare either, and if a theory has to explain it away, the theory is more likely to be flawed than reality.  Reality is never flawed.  Reality just is.  It isn't debatable.

I tried that once.  I found a cactus in the middle of a deciduous forest in the mountains on a lonely road in southern Mexico. I told it that cacti should live in desert.  I told it plainly and simply, as a statement of fact.  I told it more firmly: cacti don't grow in the mountains.  I yelled at it.  I got upset, and flung rocks and sticks in its general direction (mind you, I had been bicycling, solo, in a country where I didn't speak the language, for weeks at that point, I had been climbing the same mountain for days, and was many miles from civilization).  And after all my pronouncements of science, for all my certainty, the cactus was still there.  It's probably there now, on that mountain in between Taxco and Mexico City, among the pine trees. 
Whenever the theory diverges from actual reality, reality wins.  That was one of the points of the article, but then it tries to do the same thing with human behavior and intra-species conflict.  In the end it does seem to stray from pure science to trying to push a particular socio/political agenda, which is unfortunate because the information, presented without bias, really is important for its implications for human society, the idea that sex for pleasure is perfectly natural, normal, and acceptable, in all of its various forms.

Sexual selection does not preclude homosexuality, and indeed it can even have an adaptive advantage due to its encouragement of social cohesiveness, so well demonstrated by our closest evolutionary relatives, the bonobos. This would still not explain masturbation, which is also easy to find in the animal kingdom.  It has neither a reproductive nor a social function.
But evolution doesn't work like engineering.  There is no plan set out in advance.  Its just a bunch of stuff that happens, and some of it works.
One thing that works is flexible complex decision making systems (brains) because they can deal with a greater variety of situations than instinct alone can.  With free will an individual can prioritize themselves - not their genes - but genes keep our goals in line with theirs by controlling what feels good.  Things which tend to promote more surviving copies of genes feel good, from eating food to caring for babies to generosity.  But its a pretty imperfect system.  Sugar is a good energy source, but we took advantage of sugar tasting sweet to create things like chocolate cake and Twinkies - even diet soda which has exactly zero nutritive value, but triggers the sensory system in the same way as fruit.  We can experience parenthood through adoption.  We get the thrill of the hunt via sports and games.  None of these increases our chances of having genes survive.  But they are all byproducts of something which does help us survive - a level of intelligence that allows us to create and use technology.  Sometimes an adaption has more than one effect, and one of them is extremely useful.  As long as the other effect isn't destructive, the overall adaptation will be selected for.  Because of that we can safely short-circuit our own pleasure responses with movies and drugs and masturbation and still be fruitful and multiply.  The cost of these pointless activities is negligible.  There doesn't have to be a "why".  It feels good.  The question in this case is actually "why not?"

It shouldn't make one bit of difference what is "natural" and what isn't.  Natural isn't always good.  Getting eaten by a mountain lion is natural.  However, as it turns out all the various "perversions" do happen to be perfectly natural.  So, whatever you are into, stop worrying about it, and enjoy.


  1. Heh, that study about no bisexuality in males has been long debunked, since it had poor methodology. Newer studies managed to find men showing bisexual pattern of arousal (BTW, particular men even in those older studies showed bisexual patterns, some gay men were even a bit more aroused by lesbian porn, and straight men, by gay).
    Interestingly, findings about women have been debunked too, because they measured vaginal reaction in those studies, and newer studies showed that it has nothing to do with clitoral erection (which is homologous to penile erection in men), and it's largely automatic response, not sexual arousal per se.

    And also, you make significant error when discussing homosexuality in animals. You refer to species in which large groups express homosexual behavior, like Japanese Macaques or bonobos. And of course in their case it's actually addition to heterosexual behavior (BTW, not all bonobos are bisexual).

    But in each species, depending on exclusivety of heterosexual behavior in said species (since some animals are responsive to circulating hormones, which makes it very "un-fixed"), there are some animals that are homosexual, since technically homosexuality is intersex condition (basically, homosexuality is mirror image of heterosexuality).

    Since neuroscience shows it's also truth for humans, it points another question to your suggestions that men are different from women in that matter, considering that gay men have brains (sexuality structures) basically wired like straight women, and vice versa for lesbians and straight men.

    1. You say "that study", but there have been multiple studies that have come to similar conclusions. I'm open to learning the latest, perhaps conflicting data though - it would help if you put in links of where you got your information.

      I'm also not entirely clear on the distinction between "automatic response" and "sexual arousal". Sexual arousal IS an automatic response. But, the more relevant question, assuming the distinction is valid, is whether a similar study which measured clitoral reaction came to conflicting conclusions. Only then would it "debunk" the original.

      The significant error which you are claiming I made: " And of course in their case it's actually addition to heterosexual behavior" - I did not make that error! The article I am responding to did. That was MY point. It was my primary point! The homosexual behavior observed in animal species is almost exclusively in addition to, not instead of, heterosexual behavior.

      As far as research I have seen, the "wiring", or innate masculinity or femininity of the brain, is NOT strictly correlated with sexuality. In other words, it is just as common for a feminine man or masculine woman to be straight as gay. Again, if you have studies to share that say otherwise, by all means, please share

    2. Speaking of male bisexuality, here is article (there's link to study in it too):
      BTW, like I mentioned above I studied more precisely the Bailey's and Chiver's research about women's arousal patterns. There were straight and gay men for group comparisons too, and while on average they showed preferences based on orientation, there were actually quite a lot guys that were significantly aroused by the "wrong" porn (some even more by it, and the only person that was truly equally aroused by lesbian and gay porn was "straight" guy). So I never understood why exactly that older Bailey's study which showed that bisexual identified guys he recruited showed preference for gay porn (in article it is explained why most likely it was like that), is supposed to prove that bi guys don't exist, if particular guys, who don't even identify as bisexual, express de facto bisexual arousal pattern.

      Speaking of female arousal, no, the long line of studies that used photoplethysmograph has been debunked since the method that was used is completely invalid. Vaginal response does NOT resemble clitoral erection, and since in men there was measured penile erection, to form any conclusions about female arousal patterns there have to be done another studies, this time measuring clitoral reaction to various kinds of porn.
      I think that's what you have in mind. Since as far as I know there have been still not repeated studies in the same manner that measured clitoral erection, it still could be that women (or actually, majority of women, especially straight, since even in those vaginal response studies as how Bailey noted, some lesbians actually expressed clear category specific response) don't have arousal preferences.
      But that's completely different, new premise, we basically start from scrap, since conclusions from those old studies mean nothing now.

      Oh, and here's Alice Dreger article about this topic (with link to studies):

      In that article there were noted species in which majority express homosexual (so, in fact bisexual) behavior, but for example in domesticated sheep about 8% of males are homosexual, and in black headed gulls about 20% of females are homosexual (yet they still get pregnant - but not because they initiate sex with males, but because average intercourse in that species lasts for less than 3 seconds).
      There were neuroscientific studies regarding those rams and they found that their Ovine Sexually Dymorphic Nucleus is build like in females. There were also experiments which showed that administrating testosterone during second half of pregnancy to female fetuses results in typically male oSDN. Meanwhile, studies on those female Japanese Macaques didn't show any difference between them and female Rhesus Macaques in terms of wiring of their sexuality brain structures, but since Japanese Macaques are bisexual, not homosexual (and experiments on Rhesus Macaques gave female homosexuals with masculinized hypothalamic structures), it rather suggests that bisexuality is distinct from homosexuality, and also some human studies suggest that on average bisexuals are in fact closer to heterosexuals of the same sex.

    3. And referring to brain "wiring", it's not exactly about brain in general but specific structures, and it is known from animal experiments that, first of all, there are hypothalamic structures that are responsible for orientation of sexual behavior (to males or/and females), that in mammals it's dependent on gonadal hormones (interestingly, genes from sex chromosomes have nothing to do with it - at least that's what experiments with "four core phenotypes" of mice suggest - scientists created XX males and XY females and compared their phenotypes to normal males and females and it turned out that sexual orientation and behavior, in mice at least, is completely dependent on hormones).

      In some animals those hypothalamic sexuality structures which run orientation are "set up" during prenatal period (that's how it is in Rhesus Macaques, and probably in humans as well - sex hormones in first half of pregnancy shape phenotypic sex, in second when brain develops - brain structures of sexuality), in some neonatal period is important too, while in others it's dependent on circulating hormones.

      There are really not much questions when it comes to mammalian animals anymore, since there were done excessive studies (especially on rodents). When it comes to humans, many assumptions are taken from experiments on Rhesus Macaques, since we can't experiment on humans or apes, and as for those INAH-3 studies, it was done on few, highly re-used bodies. But everything suggest that at least one of geneses of homosexuality is simply prenatal androgen exposition or lack of it. Indirect evidences for it are also in form of various intersex conditions.


    4. Very interesting, thank you much for the follow up!

      I just finished the first link you posted. The standard explanation of self-identified bi men (social acceptance) was never satisfying, given that a significant minority (up to 25%) showed mostly hetero response patterns. This does a better job explaining those results (even if not explicitly)
      Towards the end, where it suggests many (most? all?) bi males "may" have shifting preferences over time, which could also explain prior studies finding significantly stronger preference for only one gender - they were only testing them at one point in time. It also uses the phrase "...his arousal to his less arousing sex..." suggesting that all of the bi men - ones that had passed their "stringent inclusion criteria" - still had a distinct preference. That indicates that a major reason for the difference in the conclusions of past studies and this one may be a different interpretation of the meaning of bi on the Kinsey scale. The term "bi" can mean anything from 3 only, to everything between 1 and 5. The criteria of anything above 0 and below 6 will give you far more bi people (of any gender) than a criteria of 3 only (neither sex is "less arousing").

      Another thing that I would find interesting would be an estimate of what percentage of the population meet this more strict criteria for being bi. One thing that makes (strict) homosexuality interesting is that it obviously runs counter to the basic biological / evolutionary imperative of reproduction, yet at 1-10% of the population, its too prevalent to write off as random anomaly. On the other hand, if (hypothetically) the percentage of bi men was only (for example) 0.01%, then, though still interesting, it wouldn't have the same evolutionary significance.

      "Vaginal response does NOT resemble clitoral erection" I'm not sure what you mean by "resemble". It seems as though you are implying that there is no correlation between sexual arousal and vaginal lubrication. My best guess is you mean that there isn't a strict one-to-one correlation, because, well, the correlation obviously does exist. Its not apparent to me why the measure for female arousal should have to (physiologically) mirror the measure for male arousal (does the existence of non-sexual erection invalidate that measure of male arousal?). Its true there is poor correlation between VPG readings and /self-reported/ arousal, but it remains an open question if this is because the test is flawed, or because a large percentage of women are out-of-touch with their own sexuality - though, again, I agree it would be interesting to see if other measures tended to reinforce or conflict with the previous studies. Nothing in the new CBV study actually conflicts with prior research - the editorial in the link you provided simply suggests that it is possible that it could with future research. Significant difference. The clitoral photoplethysmograph study found that "VPA and CBV increased when sexually explicit material was presented", which seems to validate, rather than conflict with, past findings.

    5. In the Black Headed Gulls example, the length of time intercourse lasts is not relevant. Are the females always the initiators in the other 80%? Maybe what differs isn't gender preference, but proactive sexual behavior. Unless there is clear behavior to indicate that the supposedly homosexual females are actively resisting mating with males, than I would say getting pregnant is indeed an sign of bisexuality. Among spiders mating is very brief too - in fact the male generally sneaks up on the female, deposits sperm, and then runs like hell. Given your logic we might assume all female spiders are gay and not consenting to heterosexual contact, but it turns out the real reason for the male's sneakiness is that the female will eat the male if she catches him. Always got to be careful not to anthropomorphize animal behavior.

      As far as brain wiring - I didn't realize your first comments were regarding animal behavior. My response was about humans. Those findings about animals all make sense - they are what we might intuitively think about human sexuality, but (as far as I know) the research (so far) says differently. If anything, genetic gender that differs from phenotypic gender may correlate more with being trans than with being gay; incidentally, the two, trans and gay, don't seem to have any particular correlation with each other.

      I don't know that anything either of us is saying particularly supports or refutes the original point of this blog post, but it is all certainly very interesting. Thanks for catching me up on some of the latest.


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