The Frontal Cortex

Gay Animals

Jon Mooallem had a really interesting article in the Times Magazine yesterday. It reviewed some recent research on animal “homosexuality,” with an emphasis on scientists who argue that same-sex behavior is not a single adaptation or mutation, but rather reflects a panoply of different instincts, spandrels, and evolutionary accidents:

Something similar may be happening with what we perceive to be homosexual sex in an array of animal species: we may be grouping together a big grab bag of behaviors based on only a superficial similarity. Within the logic of each species, or group of species, many of these behaviors appear to have their own causes and consequences — their own evolutionary meanings, so to speak.

It’s also possible that some homosexual behaviors don’t provide a conventional evolutionary advantage; but neither do they upend everything we know about biology. For the last 15 years, for example, Paul Vasey has been studying Japanese macaques, a species of two-and-a-half-foot-tall, pink-faced monkey. He has looked almost exclusively at why female macaques mount one another during the mating season. Vasey now says he is on to the answer: “It isn’t functional,” he told me; the behavior has no discernible purpose, adaptationally speaking. Instead, it’s a byproduct of a behavior that does, and the supposedly streamlining force of evolution just never flushed that byproduct from the gene pool. Female macaques regularly mount males too, Vasey explained, probably to focus their attention and reinforce their bond as mates. The females are physically capable of mounting any gender of macaque. They’ve just never developed an instinct to limit themselves to one. “Evolution doesn’t create perfect adaptations,” Vasey said. As Zuk put it, “There’s a lot of slop in the system — which,” she was sure to add, “is not the same as saying homosexuality is a mistake.”

My favorite line in the piece: “One primatologist speculated that the real reason two male orangutans were fellating each other was nutritional.” We’re so good at explaining away what we don’t want to believe.

A few years ago, I wrote about the controversial theories of Stanford evolutionary biologist Joan Roughgarden, who has a somewhat different take on homosexuality in the animal kingdom. She argues that homosexuality evolved in tandem with vertebrate societies, in which a motley group of individuals has to either live together or die alone. In fact, Roughgarden even argues that homosexuality is a defining feature of advanced animal communities, which require communal bonds in order to function. “The more complex and sophisticated a social system is,” she writes, “the more likely it is to have homosexuality intermixed with heterosexuality.”

Male big horn sheep live in what are often called “homosexual societies.” They bond through genital licking and anal intercourse, which often ends in ejaculation. If a male sheep chooses to not have gay sex, it becomes a social outcast. Ironically, scientists call such straight-laced males “effeminate.”

Giraffes have all-male orgies. So do bottlenose dolphins, killer whales, gray whales, and West Indian manatees. Japanese macaques, on the other hand, are ardent lesbians; the females enthusiastically mount each other. Bonobos, one of our closest primate relatives, are similar, except that their lesbian sexual encounters occur every two hours. Male bonobos engage in “penis fencing,” which leads, surprisingly enough, to ejaculation. They also give each other genital massages.

As this list of activities suggests, having homosexual sex is the biological equivalent of apple pie: Everybody likes it. At last count, over 450 different vertebrate species could be beheaded in Saudi Arabia. You name it, there’s a vertebrate out there that does it. Nevertheless, most biologists continue to regard homosexuality as a sexual outlier. According to evolutionary theory, being gay is little more than a maladaptive behavior.

Joan Roughgarden, a professor of biology at Stanford University, wants to change that perception. After cataloging the wealth of homosexual behavior in the animal kingdom two years ago in her controversial book Evolution’s Rainbow–and weathering critiques that, she says, stemmed largely from her being transgendered–Roughgarden has set about replacing Darwinian sexual selection with a new explanation of sex. For too long, she says, biology has neglected evidence that mating isn’t only about multiplying.

Comments

  1. #1 commenter
    April 5, 2010

    I think one reason for ‘gay’ animals might be that animals are horny and stupid.

    A bored dog will have a bash at humping a cat*. A dog humping another male dog is not that much different. I’ve seen a few human-leg-osexual dogs in my time too.

    Sorry for lowering the tone :o)

    *check youtube if you dont believe me.

  2. #2 Stan Taylor
    April 5, 2010

    “For too long, she says, biology has neglected evidence that mating isn’t only about multiplying.” Boy, you don’t even have to look at homosexual behavior to find evidence of that!

  3. #3 Katharine
    April 5, 2010

    Realistically, I think what we in science really need to make clear to the rest of society is that there is evidence for sex just being one big social-bonding potentially-reproductive lovefest.

  4. #4 DNLee
    April 5, 2010

    what Katharine said

  5. #5 Matt
    April 5, 2010

    Biologists need to borrow a line from physicists and start thinking in terms of perturbation theory, in which non-linear and back-reaction effects are treated systematically at increasing orders of precision.

    At zeroth order, homosexuality in animals seems pointless for reproduction; after all, a homosexual pair of animals cannot directly produce offspring. That kind of thinking has dominated the thinking all too many ideas in evolutionary biology, including in-group altruism and self-sacrifice.

    But at first order and higher, the reasoning behind these behaviors becomes more and more clear; social-group bonding and better survival odds for one’s close relatives and their offspring are crucial features that only appear at higher orders in perturbation theory.

  6. #6 royniles
    April 5, 2010

    The assumption that all behaviors sprang from an evolutionary purpose is of course flawed.
    Behaviors developed for one purpose can through their own experiences adapt themselves to what are best called acquired purposes. Aberrations in some cases perhaps, welcome diversions in others.

  7. #7 HiC
    April 5, 2010

    Is it possible, and has it ever been studied or considered, that homosexuality is, in fact, a result of evolution, with it serving the purpose of a sort of population control ? That way, sexual urges and behaviour that seem extremely basic still have an outlet without leading to overpopulation of the species and the decline to disappearance of resources necessary to maintain the survival of the species.

    Caveat : I am in no way a scientist, nor do I have any science training. Just a hypothesis I’ve bandied about.

  8. #8 Jon
    April 5, 2010

    @HiC

    The problem with that is that it is Group Selectionist in the worst possible way. There’s no advantage to the individual “sacrificing” his/her reproductive potential to homosexuality other than some vague advancement “to the species”.

    While the continuation of “the species” is appealing to humans, it is not actually something that can be selected for. Fundamentally, any adaptation has to help you produce more children, and homosexuality or homosexual behavior does not do that. Hence many biologists have puzzled over why it is such a widespread behavior pattern.

    The problem, as I see it, is a classic Gould & Lewtonin spandrel situation: strong sex drives are selective, so sometimes homosexual behavours result. When you have complex brains like bonobos, humans and whales, it only gets even more elaborate.

  9. #9 megan
    April 5, 2010

    @Jon
    < >

    The problem with that hypothesis view is the assumption only higher complex animals have a sex drive so strong that it needs diverting if reproduction can’t be achieved in every act. It’s specious, unsupported by biological research and conveniently allows all lower animal same-sex behaviors to be discounted or ignored and not explained. Whereas, @HiC theory which I support, can be used with nearly all animal species or any species dual sexed. By the numbers only low celled/non complex lifeforms can endless reproduce or have nearly ALL individuals successfully do so. With higher complex multicelled animals, the populations, like lemmings quickly outbreed their resources or completely deplete them. For most animal species only asmall percentage is needed to successfully reproduce to maintain the species.

  10. #10 Paul
    April 6, 2010

    When you think about it, having sexual behaviours that are not directly aimed at reproduction is no more odd than males generating millions of sperm and thousands of copulations over a lifetime when only a handful of sperm and a handful of copulations are all that are required for propagating the species. Navigating the complex social structures surrounding reproduction (including bonding and a myriad of group dynamics that are essential for survival of our species) require lots of practice. Just like we require one third of our life in childhood practising to be an adult, we usually require many years of non-reproductive sex to have that one (or maybe even 12?) opportunity(s) of actual reproduction, and many years of non-reproductive sex after we have reproduced to maintain social relationships. Who that non-reproductive sex is with is a moral question, not a biological one. It is no mystery biologically.

    While the previous generation of scientists were some of the first to proclaim acceptance of homosexuality in humans, it has taken the current generation growing up and overwhelmingly accepting it as a societal norm for the scientific community to have confidence to actually see and interpret such behaviour in the animal world. Even though scientists are typically politically and socially liberal, we are very conservative when it comes to making scientific speculations.

  11. #11 commenter
    April 6, 2010

    So basically, the way I read it, we have all settled on my hypothesis, albeit expressed in a less crass fashion. :)

  12. #12 Luna_the_cat
    April 6, 2010

    What happened to the basic, and one would think fairly straightforward, potential explanation of “it FEELS good“? Animals do a lot of things for pleasurable sensations, and full-on heterosexual reproductive mating is not the only thing to, er, stimulate sexual organs in a pleasurable way. It doesn’t seem so far out to me that over billions of years of evolution, the animals which found sex most physically pleasurable tended to reproduce more, which had the effect of making genital stimulation pleasurable in general, which had the side effect of convincing a lot of animals with sensitive genitals to “play” as much as they have a chance to just because it IS pleasurable. You can’t say that the purpose of social bonding caused this, it could have been a side effect of the discovery that mutual sex play itself was just fun.

    After all, in humans, oxytocin release is associated with sexual stimulation, no matter the genders involved, and we already know that oxytocin is associated with social bonding as well as pair-bonding or bonding with offspring. I see it as another spandrel, purpose arising out of an accidental effect.

  13. #13 Mark
    April 6, 2010

    All one has to do is watch bonobos going for it to totally understand what sex means in the animal world. All of the nonsense people attach to sex is purely cultural and religions. It has nothing whatsoever to do with reality.

    Plus, we share nearly all of our genes with bonobos and chimps. Since we’re all hominids, it’s totally and completely obvious what sex is all about.

  14. #14 Milt
    April 6, 2010

    Yep, they figured it out. Animals like sex, and they don’t much care with whom or what.

  15. #15 Joan
    April 6, 2010

    Hey – Jonah, that was you who wrote that SEED article? I had that issue years back and was totally enthralled by that piece – I had shown it to a bunch of friends, etc. Good work!

  16. #16 Jon
    April 6, 2010

    @ Meagan

    “Lower” animals have sex drives, too and they have cognitive processes that reward sex. Arguing that homosexual behavior exists because of some self sacrificing (I won’t breed for the good of the species!) is biological bull. Also it fails to explain low density homosexual behavior.

    Not everything is an adaptation, and next to nothing is an adaptation to altruistically helping others. Kin selection is fine and all, but hen you are talking about population densities you are beyond it. If a trait isn’t selected for, it isn’t an adaptation and there is no mechanism by which such sacrifice for distant relatives could be selected for.

  17. #17 Jon
    April 6, 2010

    @ Meagan

    “Lower” animals have sex drives, too and they have cognitive processes that reward sex. Arguing that homosexual behavior exists because of some self sacrificing (I won’t breed for the good of the species!) is biological bull. Also it fails to explain low density homosexual behavior.

    Not everything is an adaptation, and next to nothing is an adaptation to altruistically helping others. Kin selection is fine and all, but hen you are talking about population densities you are beyond it. If a trait isn’t selected for, it isn’t an adaptation and there is no mechanism by which such sacrifice for distant relatives could be selected for.

    Also lemmings do NOT kill themselves. When competition is too high they try to disperse, and like all dispersals, there is a high death rate especially when crossing bodies of water. They do it to raise their own fitness: lemmings that migrate and survive produce FAR more babies than lemmings that don’t migrate. There is zero evidence to suggest martyrdom.

  18. #18 darwinsdog
    April 6, 2010

    The sisters of male homosexual humans have, on average, more children than do the sisters of heterosexual males, and the difference is statistically significant. Apparently, the same genes that contribute to fecundity in human females contribute to male homosexuality. Thus, male homosexuality, at least in humans, is sexually selected.

  19. #19 Escuerd
    April 6, 2010

    commenter @ 11:

    So basically, the way I read it, we have all settled on my hypothesis, albeit expressed in a less crass fashion. :)

    No, not really. First, it only addresses the proximate cause and has nothing to do with how homosexuality is evolutionarily maintained.

    Second, it has nothing to say about why some members of some species (e.g. humans and sheep) preferentially mate with their own sex.

    Your hypothesis addresses none of the interesting parts of the topic and simply glosses over them.

  20. #20 Escuerd
    April 6, 2010

    darwinsdog @ 18:

    The sisters of male homosexual humans have, on average, more children than do the sisters of heterosexual males, and the difference is statistically significant. Apparently, the same genes that contribute to fecundity in human females contribute to male homosexuality. Thus, male homosexuality, at least in humans, is sexually selected.

    Now that is interesting. Do you have a reference?

  21. #21 Martha Farag
    April 7, 2010

    But all of this does not explain exclusive homosexuality in humans. All of these animals are bisexual, so to speak. None of them are solely gay or solely lesbian. What makes a man only interested in the male sex and not in the female sex? What makes a women only interested in the female sex and not in the male sex? Is it the psychological aspect of it all, rather than the biological?

  22. #22 Luna_the_cat
    April 7, 2010

    @Martha – actually, there ARE animals which are exclusively homosexual. It’s been seen in elephants and sheep, among others — and though I don’t have a reference for the elephants immediately to hand, here’s a discussion of the sheep study:
    http://www.medicalnewstoday.com/articles/6421.php

  23. #23 darwinsdog
    April 7, 2010

    Escuered: Camperio-Ciani, et al., 2004. Proc R Soc London

  24. #24 darwinsdog
    April 7, 2010

    “Thus, male homosexuality, at least in humans, is sexually selected.”

    I meant to say: “…is KIN selected.”

    Freudian slip?

  25. #25 royniles
    April 7, 2010

    @22, You mean some sheep don’t just wanna have fun?

  26. #26 Escuerd
    April 7, 2010

    darwinsdog @ 23:

    Thanks for the reference. I’ll check it out as soon as I get the chance.

  27. #27 Luna_the_cat
    April 9, 2010

    @25 — oh, beyond a doubt, there is something more to it than JUST having fun/feeling good. There’s obviously something in the brain which controls perception of gender attractiveness, too, which can go to one extreme or the other in some individuals. But why do we need to get fancy about an “adaptive purpose”, especially for the “casual” non-exclusive homosexuality which shows up in so many species and individuals?

    You all need to bear in mind, too, that while many individuals in both humans and other species show a strong preference for their own gender, traditionally this doesn’t stop them from reproducing. In many if not most human societies, no matter who a person turns to for “recreational” sex, they are also expected to marry and have a family, for economic and/or social and political reasons if nothing else. And animals which show almost exclusive same-gender pairing also often mate reproductively on at least one occasion. So to be honest, even if same gender preference were purely genetic and DIDN’T carry any sort of advantage, it would still be persistant in the population.

  28. #28 Waltervee
    April 16, 2010

    Great, now I understand how I am a lesbian trapped in a man’s body.

  29. #29 Bossman
    July 28, 2010

    None of the profferred putative explanations does a whit to explain preferential, obligate homosexuality in mammals. (Sheep and humans being the only examples I know of.) I am not at all surprised that dumb animals of all sorts hump just about anything in site.

    Male homosexuality is in all likelihood the result of a parasitic infection. A bug (the germ theory) is the only causal mechanism without serious logical flaws.

    For fascinating evidence of pathogenic modulation of mammalian sexual behavior: http://www.edge.org/3rd_culture/sapolsky09/sapolsky09_index.html

    Germ theory primer: http://www.theatlantic.com/past/docs/issues/99feb/germs.htm

    Gay Germ theory primer: http://gc.homeunix.net/home/post/42