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Most animals will only engage in sexual activity that can result in reproduction. There are some exceptions; Bonobos, for instance, engage in a lot of sexual activity that does not involve coitus.

Human beings have a large range of sexual activities and fetishes that do not involves exual intercourse that can result in pregnancy (I am not referring to the use of birth control).

Oral sex, anal sex, and a variety of fetishes that do not involve coitus between a human male and female.

Given that the origin of sexual acts pertained to reproduction, somewhere along the line there has been development in the brain of humans and some animals, to include sexual activity for pleasure and acts that have no possibility of impregnating the female.

It can be argued why and what purpose these acts have, whether they are indeed part of the mating process. I am not interested in this so much as, the development in the brain which has offered this variation in sexual activity to some species.

This is not at all a social-psychological question, but a question focusing on evolution, embryology and the brain. From a macro to microscopic view, if applicable.

What is the difference in the brains for animals capable of these great differences in sexual activity and what part of the brain is responsible for this?


I am not assuming that all sexual activity involves pleasure. Dogs are known to dry mount other dogs in an assertion of power. So there does appear to be a development throughout evolution, as to the use of sexual activity and communicate and purpose. Definitely, human beings have a wide range of pleasurable sexual activity derived from non-vaginal intercourse, that the vast majority of species do not. It could be argues to be counter evolutionary for want of a better term, as, like much human behavior, it serves no purpose in the continuation of the species.. OR maybe it does. Either way, it is an interesting advent of behavior.

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We don't know that "most animals will only engage in sexual activity that can result in reproduction". For most animals we are unable to properly interpret much of their behavior. We don't know how those animals "feel", if what they do causes some kind of sexual arousal or has to do with "sexual" behavior in some other way. For example, there is homosexual mating behavior in bugs. This seems sex related to us, because we don't know how else to interpret it (we assume the bugs made a mistake due to the similarity of the sexes). But how do we know those bugs aren't "gay"? Lots of assumptions. – what Nov 3 '13 at 10:53
@what it's not about feeling it's about activity. the bonobos rub gential with same sex and perform oral sex. MOST animals do not do this. Yr being unnecessarily picky.. If you can prove I am wrong pls do so. It's a valid Q. Which part of the brain is different and may be responsible for this. I know enough about animals to know this. And from study – user3543 Nov 3 '13 at 10:59
But the "feeling" is important in interpreting a behavior as sexual! At night I have non-sexual erections. They serve a physiological purpose (the limp penis has low blood flow and needs the erections to remain functional). Or: I non-sexually caress my son; I sexually caress my wife (with the exact same movements at the exact same body parts: arms, hands). The difference between sex and no sex is not behavior but how that behavior feels to the participants. Ignoring the cognitions and emotions will make it impossible to understand the difference between sexual and non-sexual behavior. – what Nov 3 '13 at 11:41
A good example for this is the discussion surrounding rape. Feminist authors often interpret rape as non-sexual and power related! So what you observe is a non-sexual behavior, if you follow that perspective, although it looks like sex. The same has been theorized about some homosexual behaviors in apes (they may serve the purpose of cementing hierarchy). So they are not sexual in the narrow sense at all, because they are not meant to cause pleasure or bonding. – what Nov 3 '13 at 11:46
Sex for the purpose of pleasure will activate different parts of the brain than the same behavior for other purposes! Because your cognitions and emotions activate your brain! – what Nov 3 '13 at 11:48

3 Answers 3

up vote 5 down vote accepted

The first question is, what is normal human sexual behavior. The answer to this changes over time. For example, a hundred years ago masturbation was thought to cause physical degeneration and be a sin, today it is perceived as healthy, even recommended. Research shows that adolescent girls who masturbate have more and stronger orgasms as adults.

So, if anal sex is normal, then there should not be any basic difference in how the brain processes this from vaginal coitus. The difference between different normal sexual practices should be like that between different words that you hear (as compared to non-verbal sound, which should be processed differently). Maybe anal and oral sex where processed differently a hundred years ago or in different cultures. I don't know of any research into this, but maybe there is.

Paraphilias like fetishes, pedophilia, incest, voyeurism and other "deviant" sexual behavior have not been well researched. There are many psychodynamic and cognitive theories of paraphilias, but since you ask for the brain, I'll focus on biological theories here. The following is taken from the chapter on paraphilias in Davison & Neale, Abnormal Psychology.

  • Since most paraphiliacs are men, it has been theorized that androgen plays a role in the etiology of paraphilias. Research into hormonal differences between paraphiliacs and normal people have had ambiguous results.
  • Sadism and exhibitionism appear to be caused by malfunctions of the temporal lobe (Mason 1997; Murphy, 1997).
  • Life experiences (like childhood abuse) are seen as the most important factor in a complex net of causes.

Besides psychological therapies of paraphilias (that will obviously influence the brain), there are biological therapies:

  • castration: results were highly ambiguous, so this therapy has been largely abandoned
  • medroxyprogesterone acetate lowers the testosterone level in men, cyproterone acetate lowers the androgene level, both reduce sexual appetency: this works in many paraphiliacs, but when they stop taking the medication the symptoms return; also, the substances can cause infertility and diabetes

As you can see, that's not much, and only two articles deal with the difference in brains. There may be more in recent articles.

The sources for the temporal lobe malfunction:

Mason, F. L. (1997). Fetishism: Psychopathology and theoriy. In D. R. Laws & W. O'Donohue (Eds.), Sexual Deviance (pp. 75-91). New York: Guilford.

Murphy, W. D. (1997). Exhibitionism: Psychopathology and theoriy. In D. R. Laws & W. O'Donohue (Eds.), Sexual Deviance (pp. 22-39). New York: Guilford.

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these discuss what is regarded as normal human sexual behavior and how this may be subjective…… – user3543 Nov 3 '13 at 11:33
Maybe you'd like to rephrase your question so it becomes clear that you are interested in the neuronal representation of different sexual behaviors and not the difference between normal (i.e. reproductive and/or healthy) and deviant (i.e. non-reproductive and/or unhealthy) sex? Your question focusses on these aspects and is therfore misleading. – what Nov 3 '13 at 11:38
I like your edit, before I assumed you were voicing your ideas, the citations helped a lot thnx +1 – user3543 Nov 3 '13 at 11:51
along with the comment As you can see, that's not much, and only two articles deal with the difference in brains – user3543 Nov 3 '13 at 11:51

My answer to this question would be pretty straightforward. From a neurobiological standpoint, sex causes the release of various pair-bonding influencing hormones oxytocin, vasopressin and dopamine.

These "feel good" hormones promote bonding and basically encourage the couple to stay together.

The more the pair have sex, the more these hormones get released. Non-functional sex would just increase the pair bond via these hormones. When a couple stays together, their offspring would have a greater chance of reaching adulthood and themselves producing more offspring.

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In my opinion is a matter of creativity and curiosity. Evolved species try to interact with their ambient in unusual ways, testing different approach to the same "problem" not only to satisfy primary needs but also to satisfy secondary needs as the need to try new things, something we call curiosity, and to socialize with the others members of our species. Primitive species interact with instinct-based responses to satisfy primary needs.

So I think you need an evolved frontal lobe capable to mediate divergent thinking, be able to modulate neurotransmitters such as norepinephrine then you will need an evolved anterior cortices and striatum.

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