# What is the Evolutionary Significance of Homosexuality? **URL:** \ **Category:** Great Debates\ **Created:** [April 29, 2010, 2:06am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702 "2010-04-29T02:06:19Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\ **Post date:** [April 29, 2010, 2:06am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/1 "2010-04-29T02:06:19Z")
Okay, right off I have to tell you, for the sake of this thread, you have to assume homosexuality came about because of _evolution_ (I realize not everybody believes that–even those who support gays). That having been said, I think I will get the discussion started with my thoughts on the matter… Yeah, I have been thinking about this alot lately. And here is what I have come up with: (a) Perhaps homosexuality is _“recessive”_ gene. Alot of genetic aberrations (notice I avoid the term “disease”) are. Or…(b) Who says homosexuals **don’t** have children!!! In fact in the some ancient cultures like ancient Greece, women were just property and for making babies. Now of course women in the U.S. etc. are not property. But there is the possibility homosexuals do in fact want to have natural children of their own. And then they just have to find a willing (and hopefully not unsuspecting) woman. My next point is a little more complicated… I have been thinking, who says homosexuals only get an advantage by mating? There are many _“other”_ ways for homosexuals/gays to influence a gene pool. For example, many (probable) gays like Leonardo Da Vinci and Michelangelo influence society by their contributions to art and science. Indeed, they in many ways set the standards for male beauty at times. Maybe (and I realize I am going out on a limb here), they are subconsciously _“directing”_ women to men with that (hypothetical) recessive gene I talked about above. And yes, everything I just wrote applies to lesbians too:). Those are my thoughts on the matter. What do the rest of **you** think? And thank you in advance to all who reply:) ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [April 29, 2010, 2:41am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/2 "2010-04-29T02:41:42Z")
Weellll . . . Most bees and ants are sterile workers who never reproduce. But, as they’re all the queen’s sisters or daughters, they still serve the differential reproductive success of their genome. ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [April 29, 2010, 2:52am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/3 "2010-04-29T02:52:50Z")
For thousands of years most same sex oriented people _did_ have children. And of course just a handfull of them a few thousand years ago would have dissembled those genes throughout the world. Assuming there is only one cause of homosexuality and it’s genetic and it’s beneficial- there’s the “Good Uncle/Favorite Aunt” theory, which is that a segment of the population less inclined to reproduce provides more teachers who don’t mind working hours later than others or adult children who serve as full-time caregiver to their elderly parents or provide assistance (financial or otherwise) to siblings raising kids or whatever. Of course there are many exceptions to this- there are gays who couldn’t care less about helping others and there are plenty of straight people who have kids and still do fulltime caregiving to others and the like- BUT it is a potential advantage of gays to society. (Personally I’m more of the “It’s just a quirk” like left-handedness or one blue/one brown eye theory.) ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [April 29, 2010, 5:41am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/4 "2010-04-29T05:41:31Z")
Since homosexuality only affects 1-5% of the population, it may not be a major evolutionary benefit. I have heard the same argument about mental illness. Some illnesses like bipolar or schizophrenia only affect 1-2% of the population. But depression affects closer to 10-20%. So the first 2 diseases can basically be explained as side effects of biology, whereas the depression may serve some biological function otherwise it wouldn’t be so common (then again, type II diabetes is common and it doesn’t serve a constructive function, however it is a byproduct of constructive functions like insulin resistance or the desire to eat high calorie foods and not exercise, which help avoid famine). So I don’t know if there is an evolutionary reason for homosexuality, or if it is just a trait we humans have. The point is, if homosexuality served a good evolutionary function, it might affect more than 2-3% of people and be closer to 10%+. If there is an evolutionary reason, the explanation I’ve heard is that homosexuals do not have kids, so they can devote more time to their nieces and nephews, who share some of their genes and have higher survival odds. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [April 29, 2010, 11:14am UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/5 "2010-04-29T11:14:23Z")
As I keep pointing out whenever this topic comes up, to an evolutionary biologist, this really isn’t a big issue. There are zillions of ways in which alleles which don’t contribute to reproductive success can persist in a population. Just yesterday, I sat through a talk about sexual conflict in fruit fly evolution during which yet another explanatory idea was proposed. In a nutshell, it was about how really high fitness females tend to produce very successful daughters and less successful sons. Similarly, very high fitness males have great sons and not so great daughters (fertility-wise speaking). According to the speaker, there’s evidence that females relatives of gay men tend to be more fertile than average. Not much beyond speculation, of course, but the point is it’s really not difficult to think of ways in which homosexuality can arise and persist in a naturally evolving species. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 29, 2010, 12:37pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/6 "2010-04-29T12:37:17Z")
I would view homosexuality for this a desire to have sex with a particular gender, which is a useful trait to ensure children, also a totally normal human characteristic, so the desire is within lines for human and for that matter animal behavior. But in this case the desire just somehow ended up in the opposite gender then what would produce the favorable outcome that it usually does. This happens quite often where normally a desirable trait occasionally shows up in a undesirably way. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [April 29, 2010, 1:17pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/7 "2010-04-29T13:17:04Z")
[One take on it](http://www.economist.com/science-technology/displaystory.cfm?story_id=12465295&source=login_payBarrier) (sorry, behind _The Economist_’s pay wall) > [@](#): > > THE evidence suggests that homosexual behaviour is partly genetic. Studies of identical twins, for example, show that if one of a pair (regardless of sex) is homosexual, the other has a 50% chance of being so, too. That observation, though, raises a worrying evolutionary question: how could a trait so at odds with reproductive success survive the ruthless imperatives of natural selection? > > Various answers have been suggested. However, they all boil down to the idea that the relatives of those who are gay gain some advantage that allows genes predisposing people to homosexual behaviour to be passed on collaterally. … > > … Brendan Zietsch of the Queensland Institute of Medical Research in Brisbane, Australia, and his colleagues have, however, come up with a twist on this idea. … They think that genes which cause men to be more feminine in appearance, outlook and behaviour and those that make women more masculine in those attributes, confer reproductive advantages as long as they do not push the individual possessing them all the way to homosexuality. … > > … the number of sexual partners an individual claimed did correlate with that individual’s “gender identity”. The more feminine a man, the more masculine a woman, the higher the hit rate with the opposite sex—though women of all gender identities reported fewer partners than men did. (This paradox is normal in such studies. It probably reflects either male boasting or female bashfulness, but though it affects totals it does not seem to affect trends.) > > When the relationships between twins were included in the statistical analysis (all genes in common for identical twins; a 50% overlap for the non-identical) the team was able to show that both atypical gender identity and its influence on the number of people of the opposite sex an individual claimed to have seduced were under a significant amount of genetic control. More directly, the study showed that heterosexuals with a homosexual twin tend to have more sexual partners than heterosexuals with a heterosexual twin. > > According to the final crunching of the numbers, genes explain 27% of an individual’s gender identity and 59% of the variation in the number of sexual partners that people have. The team also measured the genetic component of sexual orientation and came up with a figure of 47%—more or less the same, therefore, as that from previous studies. The idea that it is having fecund relatives that sustains homosexuality thus looks quite plausible. ---
**Author:** ![Shodan](https://avatars.discourse-cdn.com/v4/letter/s/9f8e36/32.png) [@Shodan](https://boards.straightdope.com/u/Shodan)\ **Post date:** [April 29, 2010, 1:38pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/8 "2010-04-29T13:38:59Z")
> [@Iim B.](#): > > who says homosexuals only get an advantage by mating? Evolutionary biology. But as mentioned, there are lots of things that persist that don’t convey an evolutionary advantage. Homosexuality may be one of them. Maybe it’s a common mutation like Downs syndrome. Maybe it has had little effect on reproductive success because it is culturally suppressed. Maybe there’s some truth to the Favorite Uncle idea posted earlier, althoug I have never seen much evidence of it in humans. It’s funny how people start sounding like intelligent design proponents when the discussion turns to genetic influences on homosex. Regards, Shodan ---
**Author:** ![Icarus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/icarus/32/72_2.png) [@Icarus](https://boards.straightdope.com/u/Icarus)\ **Post date:** [April 29, 2010, 2:25pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/9 "2010-04-29T14:25:23Z")
> [@Shodan](#): > > there are lots of things that persist that don’t convey an evolutionary advantage. Evolutionary divergence happen all the time and repeatedly - they are mostly essentially neutral. The ones that propagate broadly are considered evolutionary successes. Just because a divergence exists, and occurs repeatedly, does not equal evolutionary success (or significance). ---
**Author:** ![Simplicio](https://avatars.discourse-cdn.com/v4/letter/s/c37758/32.png) [@Simplicio](https://boards.straightdope.com/u/Simplicio)\ **Post date:** [April 29, 2010, 2:44pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/10 "2010-04-29T14:44:07Z")
I think a lot of human sexuality is based on using sex as a tool for socialization and bonding rather then for reproduction. Similarly, human females don’t “advertise” their fertility in the same manner other largish mammals do, they have orgasms similar to males and both genders engage in a lot of non-reproductive forms of sex. So homosexuality is just another form of this, it allows same-gender pairs to experience sexual bonding in larger social groups, divorced from the original (and obviously still important) purpose. Obviously, like most evolutionary psychology, thats more or less a guess, but I think there’s some evidence that suggests it. Most obviously, Bonobo chimps, who engage in homosexual (or at least bi-sexual) behavior and for whom sexuality in general pretty obviously serves as a social mechanism way beyond its reproductive function. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 29, 2010, 6:51pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/11 "2010-04-29T18:51:53Z")
Couple things: 1. We’ve done this at least half a dozen times in threads in GD and GQ, so I would suggest a search and reading what’s already been posted on the subject. 2. Not everything has to give a reproductive advantage to survive as a trait-- it just has to not be too damaging to reproductive success. And behavior that is biologically determined does not have to be (directly) genetic. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 29, 2010, 7:12pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/12 "2010-04-29T19:12:04Z")
Even with many homosexuals being culturally pushed towards having children with members of the opposite sex, and even assuming it’s a recessive gene, if that were all there was to it, one would still expect it to be a serious enough penalty to an individual’s reproductive success that it would be much, much rarer in the gene pool, if not completely eliminated. On the other hand, there are many different phenomena which might potentially be associated with homosexuality which could weigh against that. The difficulty isn’t in coming up with possible explanations, but in determining which of those possible explanations (which may be more than one of them) actually applies to humans. ---
**Author:** ![Trepa\_Mayfield](https://avatars.discourse-cdn.com/v4/letter/t/edb3f5/32.png) [@Trepa\_Mayfield](https://boards.straightdope.com/u/Trepa_Mayfield)\ **Post date:** [April 29, 2010, 9:37pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/13 "2010-04-29T21:37:11Z")
> [@Shodan](#): > > It’s funny how people start sounding like intelligent design proponents when the discussion turns to genetic influences on homosex. > > Regards, > Shodan Um…what? ---
**Author:** ![ITR\_champion](https://avatars.discourse-cdn.com/v4/letter/i/c67d28/32.png) [@ITR\_champion](https://boards.straightdope.com/u/ITR_champion)\ **Post date:** [April 29, 2010, 9:58pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/14 "2010-04-29T21:58:35Z")
While I think he could have phrased it better, **Shodan’s** point is clear. Evolutionary psychologists usually seem to assume that once they’ve proposed a possible competitive advantage for a certain gene, they’ve proved that the gene exists. Evolution, however, works by process of random genetic mutation. New genes are created by random mutations and then natural selection culls the harmful ones and propagates the useful ones. However, just because a certain theoretical gene is advantageous doesn’t mean that a mutation to produce that gene will ever arise. So, in short, those who think that genes must come into existence because they’re advantageous seem to be assuming that there’s an intelligent designer out there who’s guaranteed to create any imaginable gene that is advantageous. Personally I don’t believe that homosexuality has a genetic basis or came about through evolution and I think the evolutionary advantages proposed in this thread are mostly pretty silly. But that’s just my opinion. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [April 29, 2010, 10:07pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/15 "2010-04-29T22:07:12Z")
What evolutionary significance is myopia, sterility, baldness, a laughably small penis, autism, or any other seemingly less than optimal trait? Evolution is the product of randomness. It’s not intelligent, it just tries random combinations of possible traits and hopes that one of them is an improvement. At least half of all people will be _worse_, in terms of survival fitness, than what the average level was of the previous generation – though ideally those ones will get killed off before they can breed. There isn’t a Mother Nature who is carefully guiding the process along. Instead there’s a drunk redneck with a sawed-off shotgun splattering buckshot randomly all over the hell and hoping that one of the grains hits the target. The grand majority of everything, however, goes way off mark. ---
**Author:** ![Superfluous\_Parentheses](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@Superfluous\_Parentheses](https://boards.straightdope.com/u/Superfluous_Parentheses)\ **Post date:** [April 29, 2010, 10:19pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/16 "2010-04-29T22:19:55Z")
> [@BrainGlutton](#): > > Weellll . . . Most bees and ants are sterile workers who never reproduce. But, as they’re all the queen’s sisters or daughters, they still serve the differential reproductive success of their genome. [for bees at least, the matter is a bit more complex than that in that the genetic link between them can be even _stronger_ than the “usual” parent/sibling bonds](http://www.youtube.com/watch?v=2644rCrYlCA) (link to video) > [@ITR\_champion](#): > > Personally I don’t believe that homosexuality has a genetic basis or came about through evolution and I think the evolutionary advantages proposed in this thread are mostly pretty silly. But that’s just my opinion. A genetic base, if strong enough (compared to whatever else may be “causing” homosexuality), is something that should be detectable. I’m not sure the evidence is conclusive in that regard, but I’m not ruling out the possibility. In general though, I’d think that being _exclusively_ homosexual puts the individual in an obvious evolutionary disadvantage. That, and the apparent fact that homosexual behavior (exclusive or not) isn’t all that uncommon amongst other animals may suggest that genetically determined homosexuality (if it exists at all) is a by-product of (a combination of) generally advantageous traits. Just to make the point: occasional bum sex does not give individuals of our species a significant evolutionary disadvantage. We only need a few kids, but we like LOTS of sex. ---
**Author:** ![marshmallow](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@marshmallow](https://boards.straightdope.com/u/marshmallow)\ **Post date:** [April 29, 2010, 10:21pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/17 "2010-04-29T22:21:34Z")
There’s a whole host of things which can survive while being extremely disadvantageous to the individual. The easiest way to do that is to not even be genetic at all. Like many other problems, it could arise under certain conditions in the womb. Putting an embryo together is an incredibly complicated endeavor. Homosexuality could be a glitch in the translation or construction process. And since it would appear to be a not all too uncommon feature in many animal species, it’s probably a very persistent bug that would cost too much to rid from the ancient animal body plan (assuming it doesn’t turn out to have some hitherto undiscovered advantage). ---
**Author:** ![Cat\_Fight](https://avatars.discourse-cdn.com/v4/letter/c/90ced4/32.png) [@Cat\_Fight](https://boards.straightdope.com/u/Cat_Fight)\ **Post date:** [April 29, 2010, 10:49pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/18 "2010-04-29T22:49:19Z")
I recently read an [interesting piece in the NY Times magazine](http://www.nytimes.com/2010/04/04/magazine/04animals-t.html) on gay animals (though the scientists quoted all stress that it would be unwise to apply some of their theories to humans, see quoted bit below). > [@](#): > > IN THE LAST DECADE, however, Paul Vasey and others have begun developing new hypotheses based on actual, prolonged observation of different animals, deciphering the ways given homosexual behaviors may have evolved and the evolutionary role they might play within the context of individual species. Different ideas are emerging about how these behaviors could fit within that traditional Darwinian framework, including seeing them as conferring reproductive advantages in roundabout ways. Male dung flies, for example, appear to mount other males to tire them out, knocking them out of competition for available females. Researchers speculate that young male bottlenose dolphins mount one another simply to establish trust and form bonds — but those bonds actually turn out to be critical to reproduction, since when males mature, they work in groups to cooperatively gain access to females. > > […] > > The point of heterosexual sex, Vasey said, no matter what kind of animal is doing it, is primarily reproduction. But that shouldn’t trick us into thinking that homosexual behavior has some equivalent, organizing purpose — that the two are tidy opposites. “All this homosexual behavior isn’t tied together by that sort of primary function,” Vasey said. Even what the same-sex animals are doing varies tremendously from species to species. But we’re quick to conceive of that great range of activities in the way it most handily tracks to our anthropomorphic point of view: put crassly, all those different animals just seem to be doing gay sex stuff with one another. As the biologist Marlene Zuk explains, we are hard-wired to read all animal behavior as “some version of the way people do things” and animals as “blurred, imperfect copies of humans.” ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [April 29, 2010, 10:49pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/19 "2010-04-29T22:49:49Z")
The best evidence at the moment is that sexuality, like most complex traits, is a result of multiple genetic components as well as environmental factors. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 29, 2010, 10:58pm UTC](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702/20 "2010-04-29T22:58:24Z")
> [@](#): > > There’s a whole host of things which can survive while being extremely disadvantageous to the individual. The easiest way to do that is to not even be genetic at all. Like many other problems, it could arise under certain conditions in the womb. That just moves the question up a level, though: If homosexuality is evolutionarily disadvantageous, then shouldn’t women evolve to not have those uterine conditions that lead to it? [Next page](https://boards.straightdope.com/t/what-is-the-evolutionary-significance-of-homosexuality/537702.md?page=2)