Seed has an interview with Joan Roughgarden, somewhat controversial evolutionary biologist and author of Evolution's Rainbow : Diversity, Gender, and Sexuality in Nature and People(amzn/b&n/abe/pwll). Here's the short summary of her basic thesis:
Joan Roughgarden thinks Charles Darwin made a terrible mistake. Not about natural selection--she's no bible-toting creationist—but about his other great theory of evolution: sexual selection. According to Roughgarden, sexual selection can't explain the homosexuality that's been documented in over 450 different vertebrate species. This means that same-sex sexuality—long disparaged as a quirk of human culture—is a normal, and probably necessary, fact of life. By neglecting all those gay animals, she says, Darwin misunderstood the basic nature of heterosexuality.
Roughgarden is an awkward case that provokes a difficult split in people's opinions. She is 100% right that homosexuality is common and that its prevalence ought to be regarded more seriously as an indication of an interesting and enlightening phenomenon in evolution. However, she's completely wrong in rejecting sexual selection: in rejecting a simplistically heterosexual view of nature she swings too far the other way, adopting a simplistically homosexual view instead of a messy, complex, and almost certainly more correct mixed view. She's rather superficial in her treatment of Darwin. And most annoyingly, she has a bad habit of playing the transgender card and accusing her critics of disagreeing with her because of some LGBT bias.
Let's consider Darwin and his view of sexual selection first. In chapter 4 of the Origin, he summarizes the case for sexual selection in this way:
Thus it is, as I believe, that when the males and females of any animal have the same general habits of life, but differ in structure, colour, or ornament, such differences have been mainly caused by sexual selection: that is, by individual males having had, in successive generations, some slight advantage over other males, in their weapons, means of defence, or charms, which they have transmitted to their male offspring alone. Yet, I would not wish to attribute all sexual differences to this agency: for we see in our domestic animals peculiarities arising and becoming attached to the male sex, which apparently have not been augmented through selection by man. The tuft of hair on the breast of the wild turkey-cock cannot be of any use, and it is doubtful whether it can be ornamental in the eyes of the female bird; indeed, had the tuft appeared under domestication, it would have been called a monstrosity.
Of course, in his typical fashion, he also recounts examples of the phenomenon. He also has the biases of his time, and he emphasizes that the product of this mechanism is that it makes males more beautiful; he does not discuss homosexuality, and I'm sure he would have recoiled in distaste (for cultural reasons) at the very idea. However, Darwin is also a pluralist. Note how careful he is to avoid attributing all sexual differences to sexual selection. That he is documenting and supporting one novel mechanism does not mean that he is arguing that it is the sole mechanism; if he were alive today and were able to overcome a certain Victorian squeamishness about the subject, there's nothing in his writing to suggest that he wouldn't welcome Roughgarden's catalog of homosexual natural history as a worthwhile addition to the field. Finding other mechanisms does not negate his mechanism, however; we could have a productive argument about relative contributions of each.
For instance, I can think of quite a few hypothetical mechanisms that would drive the prevalence of homosexuality. They could every one be true, and just postulating or even providing conclusive evidence for a mechanism doesn't mean all the other mechanisms are false. I'll list a few ideas: none are contrary to evolutionary thinking.
Homosexuality is selectively neutral. This is an idea I favor, and Roughgarden herself notes that it is counterintuitive.
Roughgarden's first order of business was proving that homosexuality isn't a maladaptive trait. At first glance, this seems like a futile endeavor. Being gay clearly makes individuals less likely to pass on their genes, a major biological faux pas. From the perspective of evolution, homosexual behavior has always been a genetic dead end, something that has to be explained away.
(I really dislike that sweeping comment, "From the perspective of evolution…" I consider myself to be writing from the perspective of evolution, and I have long disagreed with that oversimplified view.)
Unless you are a very strict religious fundamentalist, which most biologists are not, it's obvious that most sexual activity does not have a procreative purpose. We human beings, to pick an obvious example, will typically have between 0 and a dozen babies over our lifetimes; we have sex rather more often than that, and engage in a host of other sex related behaviors, from girl-watching and flirting and dating to masturbation and sexual relations other than vaginal intercourse. I guarantee you that virtually all the heterosexual teenagers watching submarine races at the Point are not interested in reproduction. Sure, it's a direct genetic dead-end, but it's a bit unfair to claim that biologists universally dismiss it, or that they all think teenagers petting represent a loss of reproductive potential.
The key point, though, is that heterosexuality is not a guarantee that an individual will have children, nor is homosexuality a guarantee that an individual will not. Many heterosexual couples elect not to have children, and many homosexuals elect to have them. This shouldn't be a surprise; all it takes to start a baby is a few pokes and a spurt, and it really doesn't take much effort to overcome an inclination for such a brief event. We are sex-obsessed animals, so redirecting an ejaculation to a particular orifice isn't that astonishing.
Unfortunately, Roughgarden decides that homosexuality matters for all the wrong reasons.
But Roughgarden believes that biologists have it backwards. Given the pervasive presence of homosexuality throughout the animal kingdom, same-sex partnering must be an adaptive trait that's been carefully preserved by natural selection. As Roughgarden points out, "a 'common genetic disease' is a contradiction in terms, and homosexuality is three to four orders of magnitude more common than true genetic diseases such as Huntington's disease."
Homosexuality, if it is a "disease", is one that doesn't kill you, that doesn't diminish your reproductive ability (even if it does reduce your interest in a specific set of procreative sexual acts), and that may not reduce your effective rates of reproduction relative to heterosexuals. Roughgarden is an evolutionary biologist, so she should know full well that even deleterious alleles can rise in frequency in a population, and that arguing from frequency to a necessary phenotypic advantage is an error…especially when the "disease" is so innocuous. For all of her complaints about Darwin, Roughgarden is falling into the fallacious ultra-Darwinian trap here of assuming an advantage from simple existence.
Homosexuality promotes community bonding. This is the idea that Roughgarden favors: that some degree of homosexuality confers a direct advantage to individuals living in a community, because it facilitates bonding between same-sex individuals. It's a tool for avoiding expensive, wasteful conflicts.
Go ahead and read the article; I think Roughgarden makes a good case that this has considerable utility in social groups, and she's done some modeling that shows that this is, theoretically, a valid path to stable communities. There are objections that this requires group selection, which always puts an idea on shaky ground, but it seems to me that a willingness to settle problems erotically rather than in risky combat would also have possibilities of direct advantage to the individual.
Where I have reservations, though, is that it is a conclusion drawn from the premise that a common feature must have a genetic component. I don't see that. Show me that homosexuality is genetically heritable, and then this will be a more likely hypothesis.
Still, I generally agree with the idea that sexual activity is about far more than just reproduction. I think you'd be very hard pressed to find any biologist who finds that in the least controversial.
Homosexuality is coupled to other advantageous traits. We could call this one the "boy, there sure are a lot of gay people on Broadway" hypothesis. It also assumes that homosexuality has a genetic component, and further, that there are other higher-level properties of the organism that are associated with it. In this case, it is assumed that while homosexuality may reduce fecundity in one way (diminished preference for the opposite sex), it is compensated by other correlated features that are linked to or induced by homosexuality, such as greater creativity or sociability…and success breeds greater opportunities for breeding, or better ability to care for any offspring.
This is a common explanation, but it compounds the weakness of the previous mechanism: now we not only need evidence for a genetic component to homosexuality, but we must also have a genetic component to something like "creativity" or "musical ability" or "extroversion", and we need some kind of biological mechanism tying them all together. None of this is in evidence. In principle, though, it's a perfectly reasonable explanation.
It's not one I favor in practice. In theory, though, it's compatible with ordinary evolutionary biology.
Homosexuality is a product of weak genetic specification. I like this one better. I don't believe in the idea that we contain a lot of detailed, hardwired preferences in our brains—some, maybe, but there is a tendency in a lot of grossly reductionist science to blithely postulate genetic triggers for all kinds of semi-random activities. Even something as fundamental as an urge to have sex, while biological and nearly universal, isn't reducible to something as simple as a few genes dedicated to the function. It's a product of anatomy and neural and vascular physiology, it's tied in to the structure of the hypothalamus, it's a response to endocrine function, it's basically an emergent property of a great many genes interacting during development. And even at that, it's capable of being overridden by exposing someone to just the right weird doctrine at an impressionable age. The totality of the organism biases it in a particular way.
Similarly, I don't think any predisposition towards a particular sex is simply defined, and any hardwiring is very broadly based and relatively easily redirected. We have brains that impel us to have sex (but not irresistibly), and our brains also focus that interest in a general way towards a particular sex (but again, not irresistibly). I tend to think of nature as dictating that we will have a preference by providing a neural substrate that supports the selection of a preference…but that that preference, whatever it may be, is shaped by experience and training and culture.
Brains are plastic. Whatever hardwiring is present is weaker than many people assume, and is easily sculpted in different and unspecified directions by developmental events. That doesn't mean it can't become strong: I think my sexual interests are rather strongly fixated on the female form now, even if I don't think it's because I have genes that somehow programmed in a fascination with breasts and hips and softer features.
Homosexuality is a byproduct. This is my favorite explanation, because ultimately it's about development. Why do men have nipples? Because women need them. Both men and women have the same set of genes (more or less), and follow very similar developmental pathways, and the nipple represents a developmental constraint or byproduct: mutations that knock out the male nipple might also knock out the female nipple, so the structure is retained in both sexes. Male nipples are a byproduct of a function needed by the other sex.
We might also ask, why do some men love other men? The answer: because women need to love men. (We could also propose the complement, that lesbians exist because men need to love women.) If there are pathways that can predispose an individual to find males sexually attractive, the base structure is present in both men and women, and what we have are additional mechanisms to modulate the expression of the trait in men vs. women. Just as we guys have an echo of a female attribute in our nipples, why not assume that we also bear echoes of female mate preferences in our brains—echoes that can't be expunged without also eliminating women's desire for men (and oh, no, we mustn't have that, I know)?
Some people are prone to argue that the byproduct explanation diminishes the importance of a phenomenon—Roughgarden seems to do that, herself—but really, it's a mistaken notion. Pleiotropy and polygenic interactions are the rules in genetics, so everything is a byproduct of something else, and it doesn't diminish their importance to the whole in the slightest. I rather like my nipples, and I'm sure women are as attached to their clitorises as I am to my penis—if we all carry some trace of a homoerotic impulse as a consequence of the common humanity of men and women, that's no detriment.
It's a weird thing. I actually like Roughgarden's general ideas, and I think a lot of what she says has this nice, clean core of correctness…but then she goes off in some strange direction that ignores biology. For instance, here's a perfect example:
Being gay or straight seems to be an intrinsic and implacable part of our identity. Roughgarden disagrees. "In our culture, we assume that there is a straight-gay binary, and that you are either one or the other. But if you look at vertebrates, that just isn't the case. You will almost never find animals or primates that are exclusively gay. Other human cultures show the same thing." Since Roughgarden believes that the hetero/homo distinction is a purely cultural creation, and not a fact of biology, she thinks it is only a matter of time before we return to the standard primate model. "I'm convinced that in 50 years, the gay-straight dichotomy will dissolve. I think it just takes too much social energy to preserve. All this campy, flamboyant behavior: It's just such hard work."
I think she's right that sexuality is much more fluid than the usual gay/straight stereotype, that there's a continuum, that all of us contain the potential for a range of sexual behaviors. But then those last few sentences…they don't make sense. All sexual behaviors consume a substantial amount of an organism's effort. Even heterosexuality is a major drain—just think of all the wasted calories burned by high heels alone, or all the dead boys determined to prove their machismo by doing stupid stunts. I also think it's a mistake to pretend there is some standard primate, and that we're currently drifting towards an imaginary mean. Human primates have been spending millennia slowly shifting around various diverse patterns of sexual behavior; I think she's indulging in wishful thinking to believe that we're going towards some mysterious low-cost gender paradise where human beings don't sit around dreaming up ways to accentuate their sexuality.
Lastly, I've got to mention one thing about Roughgarden that annoys me and many other people: her assumption of victimhood.
"I think many scientists discount me because of who I am. They assume that I can't be objective, that I've got some bias or hidden LGBT agenda.
I simply don't think this is true, although I'm sure there are some few reactionary scientists whose knees jerk at the thought of a transgendered person. But look, my biases run the other way: I tend to be for greater gay rights, I am untroubled by documentation of homosexual behavior in nature, and I also stray far from Darwinian orthodoxy in science. If my opposition to some of her ideas has any basis in bias, it's not against her "hidden LGBT agenda"; I find her doctrinaire panadaptationism more bothersome.
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PZ ended with:
"... I find her doctrinaire panadaptationism more bothersome."
I guess I was influenced early by Lewontin and Gould - I find panadaptationism bothersome in general. Indeed, I believe that it's the basis for much of the misunderstanding between IDers and evolutionary biologists, both of which groups tend toward panadaptationism.
As you yourself have alluded to in the past, it's just plain wrong to consider any genetic or phenotypic character in isolation, as if it were a single, isolated effect with a single, isolated cause. If we've learned anything from the evo-devo revolution or the neutral theory it's that everything is a by-product of everything else (except maybe Mendel's seven pea phenotypes), with lots of neutral/accidental (i.e. non-adaptive) stuff thrown in. The monomaniacal focus on adaptation by both IDers and many (but thankfully not all) evolutionary biologists has blinded many of us to the really interesting and potentially more important interactions between genetic and phenotypic characters in most organisms (and especially in eukaryotes).
This means, of course, that the heyday of the "classical" modern synthesis, as Will Provine has forcefully pointed out, is long past. I find it a very salutory exercise to give up on "adaptationist thinking" entirely at times - it lets you see things you would otherwise miss.
For more on this, see my post on this subject at http://evolutionlist.blogspot.com/2006/06/are-adaptations-real.html
Worthy of note:
"A lot of people in Kansas are feeling lost right now," said Parkinson, 48, who was invited onto the ticket by popular Democratic incumbent Gov. Kathleen Sebelius. "I decided I'd rather spend time building great universities than wondering if Charles Darwin was right."
Are these animals really homosexual, or just sexual. The way I read her research, it wasn't that these animals weren't having hetrosexual sex, it was more of "any port in a storm". Some of the traits/activities she described sound like they could build togetherness in social animals.
Whats the difference? It's still a homosexual act.
I recall studies that showed increased homosexual behavior in mice living in crowded conditions. The inference was that homosexuality served the purpose of dealing with over-population, under-resources, etc. Don't know where that stands now.
In any case, as the evidence seems to be mounting (no pun) that homosexuality is, for the most part, inborn, I look forward to the day when the proof is undeniable. It might (one would hope) force a reconsideration of the opposition to gay marriage and, more hopeful still, some introspection on the part of those who see the argument only in religious terms. Yeah, like that'll happen.
A question from a non-scientist: could kin selection be another possible hypothetical mechanism driving homosexual prevalence?
I can't remember where I read it, but I think someone once proposed a kind of "benevolent uncle" theory -- that having a persistent but recessive trait for homosexuality in a family could be advantageous for that family, and would therefore spread through generations and populations. The idea was that "uncles" without families of their own would be able to devote more time and energy to gathering wealth, becoming warriors, or gaining status in other ways -- and this would benefit the reproductive fitness of their genetically-related kin.
Would this make sense?
My point was that this isn't showing preference for homosexual sex, it is showing a desire to have any sex/sexual activity. They are doing sexual things that are convenient, but given the chance, they still have reproductive sex, and that still may be because they enjoy it.
Could you also argue that homosexuality is a biological mechanism to control population growth?
Also, are we in effect reifying the concept of homosexuality, as No One of Consequence suggests? Animals, after all, don't differentiate between homosexuality and heterosexuality, as humans do. There is a range of behaviors between purely homosexual ones and purely heterosexual ones, so perhaps "sexual" is a better descriptor.
It was definately an interesting read. I hope I don't sound too much like a suck-up to say that I agreed with your assessment, both of the ability to fit with existing sexual selection theory, and the mantle of victimhood assumed in the article.
By the way, has there been any work done in the area of "instinct" versus "culture" in the social organization of mammals? I remember an experiment illustrated in one of my old zoology texts back involving the crossbreeding of lovebirds and the heritability of instictual behaviours, and a discussion of culturally learned behaviours in various primate groups. It would be interesting to see if animal cultural practices are subject to the same selective pressures as genes and development.
How apropos that the "random quote" that popped up with my viewing of this page should be:
Yet some people still don't believe in Micromanaging Higher Powers...
Relevant human genetic weirdness:
Green R, Keverne EB. 2000 The disparate maternal aunt-uncle ratio in male transsexuals: an explanation invoking genomic imprinting. J. Theor. Biol. 202: 55-63
Camperio-Ciani A, Corna F, Capiluppi C. 2004. Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity. Proc. R. Soc. Lond. B. 271: 2217-2221.
The first paper tries to explain an observation - homosexual men tend to have fewer maternal uncles than maternal aunts (ie, their mothers have many sisters but few brothers) - using X-linked loci, X-inactivation, and genomic imprinting. Weird weird weird, I read the abstract and couldn't really follow. Perhaps I need more coffee today.
The second paper addresses this discussion a little more directly - they talk about potential fitness effects (benefits and kin-selection) of male homosexuality in humans. Their major finding was that "female maternal relatives of homosexuals have higher fecundity than female maternal relatives of heterosexuals and that this difference is not found in female paternal relatives."
So if you want to make the argument that homosexuality (in humans) is somehow adaptive - there it is. Apparently, homosexual men have lots of maternal aunts who have lots of children, and probably have lots of siblings too. Given the high degree of relatedness between any individual and their siblings, aunts, and cousins, there could be a pretty strong kin-selection genetic-byproduct argument here.
My first thought on reading the second paper was "Wow, there's some genetic thing that promotes female fecundity and results in male homosexuality too!" and the second thought was "could it be just increased attraction to males - women who had higher male-focussed libidos could have higher fecundity as a result, and their brothers might just get pushed towards attraction to males as well".
Or I might be a horrible knee-jerk bigot, it's hard to tell sometimes.
Great analysis, PZ. Very illuminating.
Some years back, I sidestepped the simplistic gay/straight dichotomy by figuring that humans (at least) are really MONOsexual. Sex really happens within the individual ... and the outward manifestations of it, including choice of partner (the girl next door, Playboy magazine pic, inflatable doll, free-range livestock, you get the idea) are peripheral and secondary.
Owing to the fact that orgasm is VERY reinforcing, it's easy for me to imagine that someone who starts with a infinitesimal "bend" in some direction -- a stir of attraction to Betty Sue in sixth grade or, alternately, to a same-sex gym teacher in junior high -- can end up being reinforced into a fairly permanent (and possibly inalterable) lifestyle.
The details of that initial bend matters beyond gender - a mild attraction can be reinforced into an extremely specific attraction to Betty Sue's (and later women's) breasts, or legs, or even her squeaky giggle or, alternately, extreme attraction to the coach's (or other men's) hairy legs, or uniformed authority, or even (no euphemism intended) his whistle.
My first thought was "It's kin selection, stupid!". Everybody always forgets kin selection.
From the Seed article:
In Roughgarden's Science paper, she uses "cooperative game theory" to elucidate the diverse mating habits of the oystercatcher. Whereas Darwin held that conflict was the natural state of life (we are all Hobbesian bullies at heart), Roughgarden sees cooperation as our default position.
I haven't read any of Roughgarden's work apart from the Science paper, so maybe you're speaking of something else when you say:
I think Roughgarden makes a good case that this has considerable utility in social groups, and she's done some modeling that shows that this is, theoretically, a valid path to stable communities.
However, what I did read in that Science paper is ... well, at the very least, it shows an appalling misunderstanding of cooperative game theory which renders the entire model garbage. The simplest telling of the problem is this: cooperative game theory, as an entire field, relies upon enforceable, binding agreements between players. Without that, you're into noncooperative game theory, and Roughgarden provides no mechanism which would serve to enforce those contracts. If you read the replies to her article in Science (disclosure: one of which was written by my advisor), you can get a feeling for the problems with her approach.
Actually, now that I look back at it, I think one of the letters by Dall, McNamara, Wedell, and Hoskin says it even better (from Science, 312, p.689):
J. ROUGHGARDEN ET AL. (REVIEWS, 17 FEB., P. 965) CLAIM THAT COOPERATIVE GAME THEORY IS an ideal replacement for sexual selection theory. However, their description of cooperative and noncooperative games is misleading. Roughgarden et al. state that "in competitive [noncooperative] games, the players do not communicate" (text in brackets added) and that "in cooperative games, players make threats, promises, and side payments to each other; play together as teams; and form and dissolve coalitions." This contrasts with the textbook definitions: "A game is cooperative if commitments--agreements, promises, threats--are fully binding and enforcing. It is non-cooperative if commitments are not enforceable (note that pre-play communication between players does not imply that any agreements that may have been reached are enforceable)" (1). Thus, contrary to Roughgarden et al., the distinction between cooperative and noncooperative games lies in the assumption of a priori, binding "contracts" between players, and communication between individuals does not necessitate a cooperative game. In fact, signaling theory, a branch of evolutionary game theory [which is fundamentally noncooperative (2)], is devoted to animal communication (3). Furthermore, sexually interacting individuals are unlikely to be bound to any contracts they form without enforcement that is external to the interaction, which is unlikely for the vast majority of sexual (or indeed any biological) interactions; if commitments are not implicitly enforceable, then games are by definition noncooperative. Roughgarden et al. are correct that actions chosen while individuals interact need not be in Nash competitive equilibrium, but this does not mean we need to abandon the Nash competitive equilibrium concept, just apply it at a different level (4). When interactions are possible, it is the negotiation rules that are inherited and subject to selection, rather than the unconditional choice of action. There is no logical reason to apply cooperative game theory to interactions, just the old fashioned Nash competitive equilibrium concept at the correct level (5).
Not much left to say after that....
I'd read this, in light of later literature, as a simple biological response to the stress of the situation. This will drastically change the intrauterine environment, and rodents are sensitive to small changes in the hormone state of the particular uterus they are growing inside. For instance, females to be are more aggressive after birth when they have a male on either side of them. Apparently a leak of a little testosterone indicates to those brains a little maleness.
So with stress you increase the adrenal hormones, likely also androstenedione, which would be picked up by the males and decrease the bolus of testosterone perinatally when the brain is 'being told' it is in a male body.
There were a couple of papers long ago looking at this and humans during WWII and the starved Netherlands (?). Those data are weak. Thankfully, there really won't be a human experiment on this topic....
I agree.
I suspect selective neutrality is the best explanation. I suspect that humans would exhibit little difference in reproductive success between homo and heterosexual individuals. Cases where homosexual behavior is suppressed for cultural reasons would actually tend to accentuate this.
That said, I wouldn't dismiss the "boy, there sure are a lot of gay people on Broadway" hypothesis. It strikes me as really a pleiotropy similar to byproduct hypothesis. If we imagine an allele that confers some advantageous phenotype that also had homosexuality as part of a pleiotropy - possibly with more limited penetrance than the selectively advantageous phenotype - one could easily see that allele being maintained in the population.
The question I would have about that hypothesis is how the coupling is maintained. Presumably, the gene would have to be one that had an impact on brain development, and it is not clear why the pleiotropy might exist. Though I don't think present knowledge of brain development would rule out the general hypothesis.
If you alter the pleiotropy to be an advantage for females and homosexuality in males (or vice versa) the restricted version of the hypothesis becomes the "byproduct hypothesis".
One final aspect - the genetic aspects of homosexual behavior are almost certainly polygenic, so any explanation could involve genes with alleles that confer different phenotypes depending upon the combination present (e.g., two genes, each with two alleles, allele 1 of gene 1 only confers the phenotype when allele 1 of gene 2 is present, etc.)
Clearly, there could be a lot of complexity, and the only way we'll really start to pull things apart would be by cloning of the genes involved in male and female homosexual behavior. For political reasons, I'm actually not sure that it would be a good idea to clone genes with alleles that are associated with a higher probability of being gay. In the worst case scenario, I could imagine folks genotyping their fetus and potentially aborting if the "gay genotype" is present.
John, I vaugely remember something similar, though I recall that stress hormones were implicated. If I remember correctly women that were pregnant during the height of the blitz in London had an increased probability of having a homosexual child. Like you, I recall that the evidence was weak and merely suggestive.
Unfortunately we are doing that experiment repeatedly, though without appropriate controls (just to clarify, I'm against the bombing, not an advocate adding controls to establish the impact of bombing campaigns on human sexual behavior)
PZ:
Here's where this doesn't make sense to me: ALL men have nipples. If men love men because women need to love men for reproductive purposes (and the opposite) in the same way that men have nipples because women need them for reproductive purposes, shouldn't we expect a much higher incidence of sexual practices oriented towards homosexuality?
Is Kinsey's conclusion that 90-95% of the population is "to a certain degree bisexual" generally accepted these days? If it's verifiable, that would go a long way towards buttressing the "by-product" argument.
So, by this same train of logic, hermaphroditic species, like garden snails and earthworms, are genetic dead-ends, too, because, technically speaking, they're all homosexuals because their species have only one gender?
Stanton, as someone who's most familiar with reproduction in mammals, I'm going out on a limb talking about invertebrate reproduction, but I *think* in a lot of cases, one individual assumes the male role in fertilization and the other the female role at any given time. So even if they would "average out" to one composite gender apiece in the long run, there still is male and female going on between individuals.
I welcome any refinement or correction from someone who knows more about it than this urso-informaticist does, though.
Could you also argue that homosexuality is a biological mechanism to control population growth?
I don't see how you can do that without falling into an invalid form of group-selectionism. People who take the position that population control is for *other* people will get the benefits of limited population without reducing their own family size; thus, their genes (particularly including the genes that predisposed them to that behavior in the first place) will spread through the population.
Also, are we in effect reifying the concept of homosexuality, as No One of Consequence suggests? Animals, after all, don't differentiate between homosexuality and heterosexuality, as humans do. There is a range of behaviors between purely homosexual ones and purely heterosexual ones, so perhaps "sexual" is a better descriptor.
Yeah, I think this is a good point. Many human cultures haven't attempted to draw a line between homosexuals and heterosexuals and expected to find everyone on exactly one side, either. I think the expectation that you're either one or the other is (a) a product of one particular culture, and (b) groundless essentialism.
And I hadn't heard that particular result of Kinsey's that Dan mentions, but it doesn't surprise me much. I do wonder how he arrived at it, though.
Positions on a continuum can still be genetically influenced, though, so it doesn't make the issue go away - why have such a flexible sexual response when a naive viewpoint would indicate that rigid heterosexuality would result in more reproductive (as distinguished from sexual) activity?
I just read that article yesterday! You already covered most of my thoughts, but I'd just like to emphasize that most of those issues can, and probably do, work in concert.
Notably: "Weak genetic specification": The development of the human brain is an awesomely complicated process, which nevertheless manages to get amazingly reliable results. We should not be surprised that it isn't perfect. The variations which appear can affect pretty much any of the cognitive faculties, and the "byproduct/nipples" logic is entirely consistent with my own (limited) understanding of how neural networks work and respond to disruption.
Likewise, The "bachelor uncle/spinster aunt" scenario allows, in general, for a certain number of "non-breeding workers" to "earn their keep" through kin selection. That includes homosexuality with various other "non-breeder" conditions, under an umbrella of neutral-to-positive selection.
"Homosexuality is coupled to other advantageous traits." Well, sort of. If homosexuality is presumed to be one common result of a generic variability, then it doesn't actually need to depend on particular genetic traits! And that same variability produces all sorts of other "non-standard" types:
Some are just negative -- mental retardation, outright insanity. Some are nearly neutral, like left-handedness. But others have social functions -- the obsession that drives a tycoon, the combination of talents producing a computer programmer, the cornucopia of artistic talent. Of course, changes to brain functions may well disrupt the person's ability to mate, perhaps by twiddling their "targeting systems".... But hey, that's covered by the "allowance" for non-breeding workers! Of course, random variation won't necessarily yield just one functional change, so the variations tend to "flock" together.
Whew! It's a challenge being a gay man (with two young kids, by the way) and having one's sexuality dissected in public like a frog in high school lab.
The most compelling thing to me is that every poster so far implicitly accepts the "curiosity" of homosexuality without an accompanying "curiosity" for heterosexuality. Is not understanding the latter just as important yet elusive?
I appreciate the effort, nevertheless, and I'd like to endorse some version of kin selection. In fact, I think that quite frequently, gay men are sexually selected for compelling social reasons and encouraged to procreate through arranged marriages or by pursuit from women who are attracted to men who are in turn attracted to other men.
The detached clinical nature of discussions like these makes me want to take my straight scientist friends out and buy them drinks in a bar that welcomes both women and gay men. Nothing beats a field observation to breathe life into theory.
I'm not sure I agree with Denny's sense that there's an implicit view of homosexuality as a "curiosity." Or perhaps I'm confused by the switch between both meanings of the word. Homosexuality is a fact, like all forms of sexuality. The need to "explain" it, if that's not also offensive, comes in large measure -- at least to me -- from the relentless attacks on homosexuality from the religious right. To see it, as the posters here seem to do, in scientific/genetic terms is to reject some sort of religious view of homosexuality as deviancy, and is to argue, ultimately, for equality of treatment in all things.
I'd add that heterosexuality is the subject of a boatload of "curiosity," scientific and otherwise. And, in its many forms, is pretty darn curious.
I think you've got a fair critique here. I think if I were analyzing Roughgarden I'd say that most of what you find fault with is coming from her own experience. For example, I have seen a number of commentators on her work who do in fact dismiss it because she's transexual. And anti-gay activists who can't wish away its biological basis have taken to calling it a "disease" and offering or seeking to "cure" it. And while Darwin might have been able to encompass homosexuality in his thinking, the fact is he didn't, and a lot of biologists do think that it's an evolutionary abberation. That attitude gets picked up by Christocrats as a "scientific" justification for condemning homosexuality as "unnatural."
Basically, I think you're mostly on target with your criticisms. I think that Roughgarden is addressing attitudes that are either unspoken by professionals in the sciences or prevalent mainly in the lay audience.
RavenT said:
"Stanton, as someone who's most familiar with reproduction in mammals, I'm going out on a limb talking about invertebrate reproduction, but I *think* in a lot of cases, one individual assumes the male role in fertilization and the other the female role at any given time. So even if they would "average out" to one composite gender apiece in the long run, there still is male and female going on between individuals.
I welcome any refinement or correction from someone who knows more about it than this urso-informaticist does, though."
I was being facetious so as to provide an example where the bottom of Roughgarden's logic falls out...
It depends on the kind of invertebrate hermaphrodite, though, many, such as snails and earthworms, fertilize each other's eggs simultaneously. In fact, copulating garden snails stab each other with calcite "love darts" in order to inject a hormone that constricts the flow of semen, so that the snail that stabs the most lovers fertilizes the most eggs, without having to deal with the burden of producing eggs itself.
So, if the existance of homosexuality is potentially an indication that there is a problem with the theory of evolution, could the Intelligent Design crowd not argue that it is evidence of a "designer?" Wouldn't that be ironic? God proves his existance by creating gay people!
Existence! Existence! Damn, I hate that word.
I vote "Homosexuality is a product of weak genetic specification" with a heavy dollop of selective neutrality and maybe a dash of by-product.
At least that's what it looks like in trans-specific, polysexual ladybugs.
Though I do love that dandy little "Bachelor uncle on Broadway with an Ecstasy hook-up" theory!
And if the "gay-straight dichotomy" is largely an illusion, how would its dissolution change anything. What has been happening for millenia (i.e. anything and everything) will simply continue happen, if perhaps with less discretion.
D'oh! That *was* clever, Stanton; I'm just obtuse today :).
Interesting about the invertebrate strategies, though--by comparison, mammals are so vanilla...
Very nice essay, PZ. It sounds very plausible me (not having really studied it), while the idea that there is a gene specifically for homosexuality seems implausible.
Something that has always struck me is that with humans, correctly identifying the sex of another person can be quite a subtle activity, depending on tiny clues that we can barely describe in words. (Sometimes it's obvious, of course, such as when the person has large amounts of facial hair, as you do, PZ.) However, once we have someone pegged as a male or a female, this characterization is extremely robust. If we try to remember somebody that we once knew years ago, we may forget the person's eye color, hair color, height, etc. But we never forget whether the person was male or female.
Creationists blame anything they don't like, including homosexuality, on sin. Its not God's fault that people can be gay, its all Adam and Eve's fault. Even if incontrovertable evidence appeared that homosexuality is genetic they'd just claim it was the result of the degeneration of the human genome by A&E's sinning in the Garden of Eden.
No One of Consequences writes: It was more of "any port in a storm".
Actually, it seems to me that the notions of homosexuality or heterosexuality mean very different things in species with and without pair bonding.
I read this once before, myself.... And I also recall a newspaper article describing that a person is more likely to be gay the more elder siblings they have. It seemed that the more births a woman had--or maybe it was just as she got older, the two are definitely related--her reproductive system had various 'glitches'; different hormone levels or something. And this, along with a certain genetic predisposition, might cause homosexuality. This would also mean that homosexuality wasn't itself necessarily an evolutionary adaptation, but rather its byproduct--people with fecundity have more children (and are more "successful" at passing on their genes), but some of them turn out gay for it.
Then again, I'm no biologist--I'm in fact a dreaded computer science major--so what do I know?
I think kin-selection is a great canididate for a potential component of selection for homosexuality or other types of non-breeding. Non-breeding males and females are common in many animals. As a non-breeding heterosexual male, I can tell you I spoil the shit out of my nieces and nephews.
As for the victimhood...it's an ugly card to play in a debate. However, I think PZ has way minimized the effect her sexuality has on the perception of her work by peers. Everything about a person affects the way their work is perceived, scientists are social beings and nowhere near as rationally detached in evaluating ideas as most like to think. It does not take much effort at a conference, class, or seminar to observe differences in the kinds of attention and response given to people of different ages, colors, acccents, genders, body types, sartorial skills etc, etc. I'm not saying everyone does it, but it's common.
I never really noticed this until I lived somewhere where being a white male made me a tiny minority. I don't know how many times I have been at dinner or in discussion with a white north american scientist who, I'm absolutely certain unconsciously, has focused all of their attention on me rather than my Chinese and Indian colleagues.
It's a well-described phenomenon that men and women are both less likely to contradict or challenge a statement made by a man than the same one made by a woman. Compounding this phenomenon with other factors such as sexuality and race must also have effects.
Perhaps homosexuality evolved as a disguise strategy. In some species, smaller males adopt feminine attributes to get past the guard of alpha males and access the females. What better disguise than to imitate the sexual behavior of fe females. Until opportunity knocks?
I don't think we have defined the basic terms here. Not everyone agrees what sex is. Something that may look like sex to a martian may in fact not be. For instance: rape.
Also, if homosexuality is genetic, then why is it far more prevalent in jail than in the free population?
Obviously, homosexuality has a strong cultural meaning. Animals do not have human culture.
So I'm not buying any of it.
Here's another spanner in the mechanism: what makes one think that female-female and male-male homosexuality (either primary orientation or behaviour or whatever else) is produced by analogous mechanism(s)?
Correct, but humans don't have dolphin society either.
And?
Good topic PZ,
Having just finished Joan's book, Evolution's Rainbow, just a couple points. First, I am not convinced by her arguments against sexual selection especially in the light of recent literature. With respect to homosexuality, what she is referring to is homosexual behavior and I think she is right about the role of this behavior in a social setting; there need not be any contradiction about there being a genetic component to homosexual behavior and it's facultative nature among many males.
Joan cites some interesting statistics in her book, pointing out that the average individual fitness of homosexuals is not zero, where this has been examined, and may not be that different from heterosexuals.
As she points out, homosexual identity as we have in our culture is a recent invention but homosexual behavior is not and is not restricted to humans.
By the way I agree with miko's point about victimhood. PZ you write that:
...I'm sure there are some few reactionary scientists whose knees jerk at the thought of a transgendered person. But look, my biases run the other way: I tend to be for greater gay rights, I am untroubled by documentation of homosexual behavior in nature, and I also stray far from Darwinian orthodoxy in science....
First of all someone who is transgendered is not necessarily gay. Second of all my experience suggests that TG people and other sorts of gender queer folk are badly misunderstood. For instance, my school was perfectly willing to include sexual orientation in a diversity statement but chose to leave out gender expression. I guess crossing gender boundaries made otherwise well meaning people too uncomfortable.
It's *conceivable* that homosexuality has no function whatsoever, and innate orientations towards one's own gender are just the sexual equivalent of a birth defect.
I don't think it's at all likely, but I don't think there's currently a strong case to be made for any available explanation. Presuming that it's adaptive is premature.
I think this cuts to the core of what's wrong with Roughgarden's reasoning. Homosexuality is what a particular species and social structure makes of it. Even over the last few thousand years, homosexuality in human society has varied widely between maladaptive and adaptive depending on environmental conditions and social structures.
A good analog may be nails - many vertibrates have them, many don't, some use the for hunting, some for locomotion, some for hunting and locomotion, some as a sexual display, some still have them despite being relatively useless compared to the resources that go into maintaining them. Should we expect the underpinings of our sexual behavior to be less flexible than a chunk of keratin?
Sexual birth defect? Disguise strategy? Good grief! Take a queer to lunch and learn something!
I very much appreciate Sid Schwab's point--some posters here are asking good questions. But perusing this thread again, however, I'm still feeling that most of the posters have very stunted understanding of gayness. In spite of PZ's well-written essay, I think the discussion got launched off-kilter.
For starters, any approach that resembles "my favorite theory of homosexuality" is redolent of paternalism in science. In such an approach, the specimen under study is always the "other," not the "self," with all of the attendant echoes of phrenology and oddball theories of race. Since we are not talking about Costa Rican butterflies, but rather a core dimension of our shared humanness, why is the question framed as "What causes homosexuality?" Is not the larger, more meaningful question "What mechanisms underlie sexual attraction generally?"
Secondly, as PZ points out, sexuality may include procreation, but is famously larger than that. People of all persausions have lots of sex for lots of reasons. An animal model for human sexuality would seem to be Pan paniscus more than Pan troglodytes, in which case narrowing the discussion to same-sex investigations is very narrow indeed.
Thirdly, this whole thread has been wound around some notion of "aberration" rather than "variation." If we agree that homosexuality is documented across many species and throughout many human cultures, then aberration becomes the language of bias. And in spite of the deliciously liberal political tilt to Pharyngula, I think there is a background bias behind how this particular discussion got framed. The Broadway-loving uncle image, for example, is a little more than a joke among most of the gay men I know, who are just as likely to go bowling or spend Saturday working on their car. More importantly, gay men and lesbians are and always have been robust swimmers in the human gene pool. We are quite capable of cavorting with the opposite sex, and producing our own biological children, under a variety of circumstances. I have two dear ones myself. In fact, proportionately, more of my gay friends have kids than do my straight friends. So if we ARE reproducing, what indeed is the question? How is gayness functionally distinct from left-handedness, or tongue rolling, or variable serotypes, or any other meandering alley humans have wandered from the ancient past to the distant future?
--Denny Smith, a godless, pinko father of two.
Ooh, such radical terminology! I'll bet you say Politically Correct things to all the girls...
At present, there simply isn't enough evidence to draw any serious conclusions about the evolutionary nature and (possible) functions of homosexuality. We can't even rule out the possibility that it IS an aberration.
I suspect this relates to the question of 'at what level' evolution takes place - the genes mutating (a la Dawkins), the individual procreating (Darwin), or the species surviving (Gould).
Making the big assumptions that homosexual orientation is objectively real, and is adaptive - that it is or was useful in some way - we can ask: on what level might it have been useful?
Does it help a strand of DNA if the person it codes for is gay? I don't see how it could be.
Is it useful to an individual if they're homosexual? I suppose it might be correllated with greater creativity or sensitivity - but IMO that's just another pleasant but false stereotype.
Might it offer an advantage to the species if some individuals don't reproduce themselves, but assist in taking care of the children, helping out in group work, and maybe even making other people's lives more enjoyable? Maybe.
Winawer: "A game is cooperative if commitments--agreements, promises, threats--are fully binding and enforcing. It is non-cooperative if commitments are not enforceable ..."
This kept nagging at me, so here goes: Remembering that the real world does not seal its problem boxes very well, consider this:
We don't have a "natural" mechanism to enforce arbitrary agreements in general. We do have "standard" means to enter and enforce one particular committment, namely a committment to the welfare of particular individuals. There are several ways to establish this committment -- by instinctive response to multisensory signals, by situation-specific imprinting, or even by "progressive habituation toward cooperation".
This particular "contract" is heavily supported by instinct, to the point where it can suborn or overrule our "higher rational functions". On the other hand, various societies have a distinctly mixed response to it, largely because it can interfere with social heirarchies, and directly compete with central authority.
Anyone figure it out yet? I've been tossing out lots of fancy phrases here, but most people have a much shorter word for it. I'm talking about "the other four-letter word", the one that runs through all of humanity's recorded history... Love.
Salty C: Obviously, homosexuality has a strong cultural meaning. Animals do not have human culture.
So I'm not buying any of it.
Homosexuality has strong cultural meaning for most higher mammals that are social. Obviously you've never owned a male dog. ;-)
Mounting behaviour between males is pretty prevalent as a means of enforcing hierarchy (which explains the prevalence of prison rape, IMHO) without having anything to do with orientation. "Homosexual behaviour" is more prevalent in prisons, but I doubt that there are more homosexuals in prison, or that they are responsible for more prison rape.
Sexuality is a tricky thing to study in humans, because it is so hard to seperate genes from developmental influences from "nurture" without greviously breaking ethical considerations about human experimentation. Given the random appearance of definitely homosexual humans in my family, I personally lean very heavily away from genes.
As for (Daryl McCulloguh): correctly identifying the sex of another person can be quite a subtle activity, depending on tiny clues that we can barely describe in words. ... However, once we have someone pegged as a male or a female, this characterization is extremely robust.
From personal experience (I know, the plural of anecdote is not data), most gender clues are cultural, judging from the number of times I have been mis-identified. It is also amusing to note that the person making the mis-identification usually gets pretty flustered about it. Note that physically I am in no way androgynous.
"Homosexuality occured after The Fall", says the IDer, being very carefull not to identify the Fallers or what most likely Felled them.
David Harmon wrote: We don't have a "natural" mechanism to enforce arbitrary agreements in general.
You're right - which was exactly the point that anyone who knew game theory at all and wrote into Science about the matter was trying to make. Roughgarden tries to use cooperative game theory, which is a branch of game theory that deals with enforceable commitments, to support her model. Remember that game theory started largely as an economic tool, so cooperative game theory can be most easily conceptualized as dealing with situations involving legal contracts, bargaining, and so on. The problem with her model is that no such mechanism exists in nature - there's no third party that will step in and enforce anything.
This leaves us with noncooperative game theory, which is what most researchers who do game theoretic analyses use to look at questions like the ones Roughgarden is talking about. Note that the name "noncooperative" is a bit of a misnomer. The Wikipedia entry on non-cooperative games has a nicely succinct definition of the difference: "a non-coperative game is one in which players can cooperative, but any cooperation must be self-enforcing. A game in which players can enforce contracts through third parties is a cooperative game".
We do have "standard" means to enter and enforce one particular committment, namely a committment to the welfare of particular individuals. There are several ways to establish this committment -- by instinctive response to multisensory signals, by situation-specific imprinting, or even by "progressive habituation toward cooperation".
[...]
I'm talking about "the other four-letter word", the one that runs through all of humanity's recorded history... Love.
Right. So, individuals comes together through a variety of mechanisms and form attachments that benefit both parties, and in some cases we call this and the emotions that attend it "Love". (I'm trivializing, I know, but there's a reason for it.) If one were to accept that relationships like this were modeled by cooperative game theory as Roughgarden suggests, we would be faced with a world where relationships were valid not because people loved one another, but because a third party was forcing them to be in the relationship! (Catholic church, anyone? ;-) Now, I don't think that that's what Roughgarden had in mind, but that's the problem; she doesn't really understand the tools she's using, so she uses them incorrectly. This is what really astounds me about the whole thing - that such a basic error slipped right through the whole process from writing to publishing. Seriously, who were the reviewers on that one?
Graculus, I do own a male dog. I don't need to, because as pretty much everyone else on Earth I have seen dogs perform mounting behavior. But is it sex? What is sex? That's what hasn't been defined. And for prisons, I wasn't talking aboit rape, but longterm relationships which exist, and which I would call homosexual, though the participants may not be homosexual. The genetic component is murky, I'm sure you agree.
Also, female dogs perform mounting behavior just as frequently as males, not that it matters.
Also, female dogs perform mounting behavior just as frequently as males, not that it matters.
The last paragraph of PZ's essay and some of the comments seem to conflate transgenderism with homosexuality. Homosexuality is a sexual attraction to the same gender. Transexuality is the more extreme form of transgendered behavior and is more complex, starting with gender dysphoria - a dissatisfaction with one's biological gender and varting degrees of self-identification as a member of the other gender. The sexual orientation of transgendered individuals varies, but with a much higher proportion self-identifying as homosexual or bisexual as a member of the adopted gender.
Gender can be looked at in several ways:
Sexual attraction (homo-, hetero-, & bi-)
Self identification (trans- or not or varying degrees)
Karyotype (XX, XY etc.)
Outward phenotye ("normal" or Andorgen Insensitive Syndrome, etc.)
Hormonal
Behavioral ("tomboy", "sissy" etc.)
For more info on successful adaptations to transexuality, see Lynn Conway's homepage.
"Homosexuality occured after The Fall", says the IDer...
But according to my copy of the SuperSecret Real Genesis, heterosexuality occurred before the Fall. You see, the IntelligentDesigner caught Adam playing with himself and had a realization that since the Fall was coming (along with Adam) that it would be a good time to Create Eve, whose fault it would be. So, Eve was created with Adam's baculum [not the rib!!] and the requisite clay, so Adam would have someone to play with. The IntelligentDesigner was also prefiguring an eventual punishment for the post-fall Adam, for, behold, the lack of a baculum would eventually cause erectile dysfinction.
SaltyC: The genetic component is murky, I'm sure you agree.
Oh, I'm not even convinced that there is a genetic component, it's about as clear as mud.
My point, which others have addressed more deftly, is that sexuality/orientation/gender etc are remarkably fluid, and fall along a scale rather than a dichotomy. My point about dogs (I put in a smiley), etc, is that "sexual" behaviours perform functions other than anything strictly to do with gender and sexuality, but such is blended into other social behaviours. To equate these social behaviours which have "co-opted" sexual behaviours with strictly gender/sexual behaviour would, IMHO, be a mistake.
I'm not confusing the T and the G in LGBT. This is about a transgendered individual, Roughgarden, writing about homosexuality.
(cross-posted from Raising Kaine blog)
Recent research has indicated that at least in humans, homosexuality in males is correlated with birth order - that is, the farther down you are in birth order, the more likely you are to be gay.
I wondered when I read this what possible adaptive value this could have, but after reading Richard Dawkins' _The Selfish Gene_, I came up with a hypothesis.
Dawkins argues that any "genetic" characteristic which tends to be more successful in reproducing itself will be favored. He uses this argument to great effect, concluding that protection/assistance to siblings (or other family members) is favored because of the shared genetic inheritance - if my brother survives, (approximately) half of my genes will also survive. I looked at this analysis and wondered if children with more adult resources devoted to them were more likely to survive - especially in the context of perhaps 1,000 or more years ago - obviously, a child with two parents was more likely to prosper than a child with one. Similarly, a child with a larger extended family might be expected to do better. What if some genetic trait, likely in the female and in pregnancy, changed the hormone balance of the fetus towards homosexuality for subsequent children? What does the childless person do with his/her resources? Mightn't this result in more adults caring for the children of the oldest (or older) siblings and therefore positively influence survival and/or reproductive success of those children?
I have absolutely no evidence relating to this hypothesis, it was just something I thought of because otherwise I cannot account for the persistence of homosexuality in a population. While I know many gay people with children, on average they have (many) fewer than heterosexual people - so how does the trait persist? It must somehow positively influence the survival of others with the shared gene(s).
This is a testable hypothesis, given the evidence above. I hope somebody does the research to indicate whether particular family lines with higher than average numbers of homosexuals are more successful (in any species)!
And to Denny, thanks for your comments. You say your gay friends have more children than your straight friends, but my experience is completely opposite. In fact, of my gay friends, biological reproduction is running at less than 10%.
A few specific comments:
Homosexuality is selectively neutral-
NO! If we consider differential fitness as the measure of fitness, then it's really easy to see that homosexuals will leave fewer offspring on average than heterosexuals. Forget inclusive fitness; it will not make up the difference.
Homosexuality promotes community bonding-
So what! Without group selection (which most serious biologists do not consider possible) type arguments, this is a trivial observation.
Please see this post for more arguement.
From Denny: 'The most compelling thing to me is that every poster so far implicitly accepts the "curiosity" of homosexuality without an accompanying "curiosity" for heterosexuality. Is not understanding the latter just as important yet elusive?'
The term is meant purely scientifically and shouldn't convey any judgement. The fundamental characteristics of all life forms (as taught in high schools) are they are born, they eat, they excrete, they reproduce, and they die. Homosexuality seems at face value to go against one of the two only inherent actions of life, reproduction.
So homosexuality being present in so many bisexual (two sex) animals including humans should indicate it does serve a genetic purpose benefitting the species. The most likely is reducing the risk of the species dying out due to overpopulation, and initial studies showing rat populations under resource stress had larger numbers of homosexuals being born support this very basic cause and effect proposition.
Humans are compelled to have sex in the same way they are compelled to eat, for their and their species survival, sex feels good for the same reason nutricious food tastes good - so we'll do it a lot. I agree that in the absence of an other-sex partner a hetrosexual animal will fulfill their need for sexual function whereever they find a method of release. This is different from the kind of homosexuality conferred on an individual during gestation.
Sorry if this sounds simplistic, I'm not a scientist or a behavioural speciast.
I'm also not much of a typist it seems.