This is something I've been pondering myself recently, the leading scientific opinion is that jomosexuality is based on biology rather than being a choice, but I still wonder. I think Nature vs Nuture comes into play. Just wondering what others thoughts are.

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Yes it does. In fact, same sex sexual contact has been observed in nearly all, if not all, species that science has observed. There are many proposed mechanisms by which homosexual behavior may offer an evolutionary advantage to a population. This is an important point to make because homosexuals are less likely to sexually reproduce.

The most closely related example that I can think of is the bonobo. These apes regularly engage in non-reproductive sexual contact with each other in a manner which does not discriminate based on biological sex. They seem to use sex as a means to avoid conflict. When feeling aggressive, they resort to sex to diffuse the tension. In this instance, all this superfluous sexual contact seems to increase peace and social cohesion. At the very least, this makes a good case for sexual contact having potential non-reproductive evolutionary advantages. That is, if sexual behavior can be beneficial in a non-reproductive context, then this traits which increase the liklihood of this behavior (genetic or social) then those traits can experience positive selection because they offer an evolutionary advantage. In this way, sexual contact need not be purely reproductive as it appears that evolution can, and does, hijack many functions for other purpose. In humans, we see sexual contact increasing the strength of the emotional attachments between mates, which is beneficial because it increases the liklihood that the pair will stay together to raise children. Human children being very weak and defenseless for a large portion of their lives, do much better with this extra support and therefore such traits would be positively selected for. Of course, there's also positive selection for promiscuity, but that's just a different positively selected reproductive strategy. We don't have to pick just one within a species.

Moving along, the next species I would like to highlight is penguins. It has been shown that male-male pair bonded penguins will still build nests. These penguins, unable to lay eggs of their own will steal the eggs of other pairs. It sounds pretty terrible, but they actually take just as good care of the eggs and resulting offspring as male-female pairs. The advantage here is that it is MUCH easier to steal from a nest where the parents are absent, either because they are neglecting their eggs or because they have been eaten by a predator or otherwise died. These homosexual penguins are then essentially caring for and raising the orphans of the penguin world. While they themselves do not pass on their traits, the traits which are responsible for producing homosexual penguins could still be positively selected for within the population. That is, if a population benefits from having non-reproducing homosexual members, then those traits will be indirectly selected for within the population. It's a trade off really. Eventually a dynamic equilibrium will be reached where the frequency of the factors which produce these traits will exist at the perfect point to produce the ideal statistical liklihood of producing the right ratio of hetero/homosexual penguins.

This same mechanism has actually been suggested as one of the many possible ways that homosexuality might be positively selected for in humans. I believe it's called the generous uncle hypothesis or something of the like. The theory being that non-reproductive members of a family will devote their efforts towards assisting in the raising of other family members which increases the livelihood of those who are closely related and thus potentially increasing the frequency of the traits responsible for producing their homosexuality. This has not been proven, but it is one of the hypotheses that is currently floating around.

There's another which suggests that homosexuality may be a consequence of the fact that many feminine traits are positively selected for in males. For instance, kindness, sensitivity, attractiveness (pretty boys), and appreciation for things like art seem to be more commonly associated with females than their counterparts of cruelty, the lack of empathy, homeliness, and the appreciation of ESPN. This has been termed the "Johnny Depp Effect". It has been suggested that feminine traits could be positively selected for in men and that if the scale is tipped too far, then mate selection gets caught in the crossfire. In this case, homosexuality is merely a consequence of having too much of a good thing. These feminine traits, in the right amounts, increase the attractiveness of a male and thus his reproductive success. However, when they possess too many of these traits, it could result in lower reproductive success because they are now effeminate or otherwise homosexual. In this case, it seems like there would be a "sweet spot" for such traits and sometimes there are going to be those that lay on the outskirts of the bell curve, with hyper-males on one side and effeminate males on the other. So while homosexuality itself might not be positively selected for in this instance, it could be that the traits which can contribute to homosexuality may be positively selected for.

There are many more hypotheses for the evolutionary underpinnings of homosexuality but I think I've managed to prove my point with these two. Interestingly, we have not proven that a single one of them appears to be the case in humans. The difficulty with this sort of thing is that there may be many different evolutionary underpinnings for human homosexuality. For instance, both of the above could be true and therefore it would be difficult to determine which is the case in any given instance because they are both playing a role. It may be that there are ten or twenty different reasons why homosexuality could be directly or indirectly selected for within human populations... and these reasons may change from one culture to another as such individuals/populations would face different social selective pressures.

Imagine a culture which considers homosexuals gender-transcendent and thus closer to god. In this hypothetical culture homosexuals would be revered as holy people. A family which produces many homosexuals will have greater influence in their community and perhaps even have greater resources as people would want to support these holy people. Of course, if they produced 100% homosexuals, they wouldn't make for a very large family, so once again, it's all about that sweet spot. Obviously, this is a purely hypothetical, but not unreasonable, scenario. However, it does illustrate at least one possible example for how homosexuality could be positively selected for due to cultural/religious reasons.

The take away points I want to make are thus:

  1. Human sexuality need not be reproductive. It can, and does, serve many other purposes.
  2. Homosexuality, or the traits which contribute to is, may be positively selected for in an indirect manner.
  3. Many different reasons for homosexuality to be positively selected for could be true at the same time and even vary from one culture to the next.


Now, I must point out that I've specifically chosen to speak entirely in evolutionary terms, not in terms of sexual choice. This was mainly due to the fact that I wanted to stay on topic with the question asked. Obviously any choice to become homosexual would be social, not evolutionary (unless you're talking about the evolution of social norms). Whether or not homosexuality is a choice could be debatable, but I would say that it's a different debate from whether or not there are evolutionary underpinnings to homosexuality in humans. The fact of the matter is, it is entirely possible and even very likely that evolution has played a role in the prevalence of homosexuality in humans.

Thank you to all who posted,

I didn't know this discussion was going to take off, but I'm glad it did, I've learned a lot.

I think that the role of Nature vs Nurture has been somewhat downplayed, yes no one recalls 'choosing' to be gay, but you can't choose your parents.

We are extremely affected by our environment, especially during our early developmental years.

There's a lot of data supporting the correlation between sexual abuse, and homosexuality.

I've done some interesting reading on deviant behavior (not negative, just deviated) referring to the human species,  and instances of sexual abuse could, theoretically, account for every instance of Homosexuality. I don't think it does.

I have 2 cousins, 2, they are sisters (2 of 3), and they have both recently come out of the closet.

I feel bad for their mother, a staunch Catholic, who believes their souls are in jeopardy of eternal punishment. She'll live anyways.

The interesting thing is that their father, my uncle, while not sexually abusive, has been extremely emotionally antagonistic (abusive) to their mother, and them their whole upbringing.

Nothing too extreme, but steadily antagonistic.

Now this interesting data that has recently presented in my own life, could affect my scientific reasoning, but i believe our psyche is a product of our environment, nearly as much as our bodies are products of our parents genetics.

I mean, come on, 2 out of 3 daughters, genetic mistakes? Maybe it's a virus.

Thank you to everyone that has posted so far, I am learning a lot, and am proud to have joined a social network that not only Is Good w/o god, but encourages free and open discussion.

But countless species other than humans engage in homosexual behavior. What of them? Are you implying it's possible most of them were sexually abused? Do we need to put penguins and rams in therapy? lol

For the sake of argument, let's forget that definitions of words like "minor" and "sexual abuse" are fuzzy and have changed quite a few times over the last few thousand years. We certainly see frequent evidence of homosexual behavior in animals with no "sexual abuse" whatsoever during prepubescence. Dogs hump other male dogs all the time, even when raised alone, so this is certainly not a learned behavior or one which presents itself in a majority of cases only when "sexual abuse" was involved, as the article Ryan linked claims.

I agree that a human isolation study, as well as twin separating, could offer interesting insight into nature vs nurture

The site you link to is a politically motivated site run by "Heterosexuals Organized for a Moral Environment" where they discuss the "negative effects of homosexuality" with other articles such as "The Case Against Homosexual Activity" and "On The Unhealthy Homosexual Lifestyle". The papers are very selective and many are out of date, and this is basically a "hate site" papered with a veneer of pseudo-science. There is a rebuttal at and many other places. The argument simply holds no water if you stop and think about it. None of my gay friends have ever been abused, and the overwhelming majority of people who are abused do not become gay.

Haha, sorry about that, I found a more neutral site offering interesting data on the subject


I'm not saying that sexual abuse ALWAYS leads to homosexuality, Nor that ALL homosexuals were sexually abused.

But there does seem to be data supporting a correlation, and this is a case of NURTURE, not NATURE....


Unless they were born to be abused? Maybe they were asking for it...


I disagree. You can't conclude that the abuse is causative in those cases where it is reported. Plus homosexual behaviour is different to being homosexual. If you were to indulge in sex with anotehr man out of curiosity, that would not make you gay. Same sex populations in, say prisons, sometimes do this. It doesn't make them gay. Is your last sentence a joke?

Yes my last sentance was a joke, a bit off color, I apologize.

I haven't concluded anything.

I'm interested, and curious, and that's why I started this thread.

This is a topic I know relatively nothing about,

Again, there is NO reason it would not make evolutionary sense based on our current level of knowledge.  Evolution is not quite as straight-forward and function-focused as people seem to think.  It really comes down to how homosexuality arises, which we don't entirely know.  If it is the product of in utero conditions, genetic factors and epigenetic factors, it does not in any way conflict with 'evolutionary sense'

That doesn't change anything in the slightest.

Why would Down syndrome not make evolutionary sense?


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