The Evolutionary Purpose of Male Homosexuality

A recent show on the science channel alerted me to an interesting new hypothesis about the evolution of homosexuality. Contrary to popular thought, it does not appear to be an accident. (If anyone can find documentation about this new hypothesis... let me know). Particularly interesting is the behavior of primate males in family groups. As is well known, apes (such as chimanzees, bonobos, and gorillas) that live in family groups consist of many females, one dominant male that gets exclusive access to mating with the females, and sometimes one or more submissive males that do not have the right to mate with the females. A new scientific hypothesis suggests that our early ancestors (who may have lived in similar family groups) may have developed homosexuality among these "submissive" males. The sexual behavior of the apes currently being studied suggests that male homosexuality has an important evolutionary advantage in family groups. The submissive males engage in homosexual behavior as a way to satisfy sexual instincts... but the advantage goes further than that. By engaging in homosexuality, the submissive males present themselves as no threat to the dominate male and thus promote group harmony, by discouraging male fighting over mates. Furthermore, these homosexual males provided survival advantages to the family group by helping to protect the females and infants from predators and rival family groups and to find food for the group. In this case, the sacrifice of the genetic survival of one individual gave an enormous advantage to the survival of the group. - Which is something evolution has been known to favor.

Although this particular advantage of homosexuality is obsolete for humans, the homosexual orientation would have survived despite that because our society changes far faster than evolution.

So.. for any homophobes that claim homosexuality is "unnatural" - Au Contraire! It is VERY natural, for some people!

Views: 3994

Tags: Science, biology, evolution, gay rights, homophobia, religion

Comment by Arcus on March 8, 2012 at 12:32pm

Not unreasonable, but a few issues and questions pops to mind. Firstly, there are certainly many animals which engage in homosexual activity, but to my knowledge humans are the only species in which some members are exclusively homosexual. Secondly, knowledge gained from studying other species cannot immediately be translated to humans, especially when it comes to social structures. Third, we cannot really know how social structures functioned in pre-history since it leaves little, if any, evidence behind to study. Lastly, if homosexuality is purely a social construct / behavioral trait, it would seem odd that it would have survived this long.

Comment by Becca on March 8, 2012 at 12:49pm

I heard this hypothesis in a human sexuality class I took in college... I'll have to see if the books I kept from the class say anything about this.

Comment by Danny Sanchez on March 8, 2012 at 1:04pm

There was another discussion/post were someone posted a video of Dawkins explaining a "Sneaky Fucker" theory. I liked that one better.

Comment by kris feenstra on March 8, 2012 at 1:47pm

Firstly, there are certainly many animals which engage in homosexual activity, but to my knowledge humans are the only species in which some members are exclusively homosexual.

There are at lest some species where this is the case.  Some penguins seems to be exclusively homosexual.  Swans can display the same behaviour.  I don't have a comprehensive list off the top of my head, but it has been documented.

Secondly, knowledge gained from studying other species cannot immediately be translated to humans, especially when it comes to social structures.

True, but the hypothesis precedes the observations.  In that scenario, these observations lend credence to the hypothesis.

Third, we cannot really know how social structures functioned in pre-history since it leaves little, if any, evidence behind to study.

That's a mixed bag.  Some of the evidence of how prehistoric cultures lived can be odd and surprising.  Not perfectly related to this topic, but I recall reading an article recently on a burial site where a five-millennia-old male skeleton was buried as if it was female. (first news article to come up in a quick search: dailymail.co.uk)  Granted, 5000 years isn't all that far back in the context of this conversation.

 Lastly, if homosexuality is purely a social construct / behavioral trait, it would seem odd that it would have survived this long.

This hypothesis doesn't suggest that it is.

Comment by Rob Klaers on March 8, 2012 at 3:59pm

Arch... I recall having heard that myself. I think that may be what influenced my idea that it was natural population control. 

Comment by Arcus on March 8, 2012 at 4:07pm

@Kris: Re my first issue raised, do you have any links? The only thing I could find was an abstract from wiki, but it seemed unrelated and about drosophila. The second and third we are pretty much in agreement. As for the last one, I did not find any mentioning in the OP that the theory was biologically driven (outside of course that biology will always have a strong impact on behavior). Where did I misread..?

Comment by kris feenstra on March 8, 2012 at 4:13pm

Sadly, not on hand.  I searched briefly, but it's difficult to target articles on persistent/ exclusive homosexual behaviour in animase.  The wikipedia page on homosexual behaviour in animals lists some details if I recall correctly, and does provide adequate footnotes, but I'm not certain how much of the references provided can be referenced online.

I'll try to see if I can dig up something useful when I get more free time as it's not a claim that should be taken on face value. 

Comment by archaeopteryx on March 8, 2012 at 4:19pm

Rob - I will be the first to grant that homosexuals have been maltreated for eons, and can understand the current trend to define homosexuality as a purely genetic predisposition, but I had a biology instructor who instilled in me that one can never, in explaining any trait, completely separate heredity from environment. I can't help but believe that each plays a part, though not always in equal proportions.

Comment by Unseen on March 8, 2012 at 5:45pm

@archaeopteryx   "Rob - I will be the first to grant that homosexuals have been maltreated for eons, and can understand the current trend to define homosexuality as a purely genetic predisposition, but I had a biology instructor who instilled in me that one can never, in explaining any trait, completely separate heredity from environment. I can't help but believe that each plays a part, though not always in equal proportions."

Perhaps the part that environment plays is the degree to which homosexuality is ignored or scorned in the particular environment. So, while in one permissive environment homosexuality is simply ho-hum and so homosexuals feel free to reveal this train whereas in another one homosexuals live in fear of exposure and so do their best to keep this trait "in the closet."

Comment by Benjamin Cruzat on March 8, 2012 at 6:39pm

Regarding your actual post I don't think being submissive leads to homosexuality and in fact might be the other way around. Homosexual apes simply don't want what the alpha male is trying to protect and so wont challenge him for it.

An example would be a small carnivore and a large herbivore who are trying to eat. Simply because the carnivore isn't eating the local greenery doesn't mean that he is submitting to the herbivore, its just that he can't and wont eat plant life.

As far as close quarters leading to homosexuality I don't think that it is a causation but simply correlated. A guess as to why homosexuality did run rampart could be attributed to pheromones, however its just a guess.

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