All animals have sex for pleasure

If you don’t understand this, you don’t understand evolution

Ariel Pontes
Nov 22, 2018 · 9 min read

There is a myth I keep hearing that says only humans and dolphins have sex for pleasure. Sometimes bonobos and a few other species are also included in this supposedly select group. Depending on how we interpret this claim, it may have some truth to it. But this wording could not be more unfortunate, and I feel compelled to clarify why.

Everything we do is to obtain pleasure or avoid pain

Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. It is for them alone to point out what we ought to do, as well as to determine what we shall do. On the one hand the standard of right and wrong, on the other the chain of causes and effects, are fastened to their throne. They govern us in all we do, in all we say, in all we think: every effort we can make to throw off our subjection, will serve but to demonstrate and confirm it. In words a man may pretend to abjure their empire: but in reality he will remain subject to it all the while.

– Jeremy Bentham, An Introduction to the Principles of Morals and Legislation

Everything you do intentionally, you do for one of two reasons:

  1. obtaining pleasure, which may be immediate (e.g. playing games, eating tasty food, etc.) or expected (e.g. doing work you don’t like in order to get paid or waging Jihad in the hopes of getting 72 virgins).
  2. avoiding pain/discomfort, which may be immediate (e.g. scratching an itch, moving your hand away from fire) or expected (e.g. paying for health insurance).

If you’re unsure whether you agree or not, I invite you to think of a counter example. I am yet to hear a compelling one.

It’s the same with all animals

You may ask yourself: how could we possibly know that the experience of animals is similar to ours? Well, we couldn’t. It’s an elusive phenomenological question that seems indeed unanswerable in principle. But then, really, we don’t know anything. Except, perhaps, as Descartes would argue, that we as individual minds exist (I think, therefore I am) and as others would argue, that certain a priori statements are true (e.g. 2+2=4). For a posteriori beliefs that rely on empirical data, however, you just can’t have any bulletproof justification to believe anything with 100% confidence. For all you know, you could be a butterfly dreaming you’re a human or a brain in a vat living an illusion created by an evil demon, or the universe may have sprung into existence last Thursday, with fossils, ruins, and fake memories implanted in all our brains. But although we can’t have 100% confidence in our beliefs, we don’t let this paralyze ourselves in our day-to-day lives. For all intents and purposes, there is such a thing as sufficient confidence. We assume we’re not living in the matrix, and we assume that our fellow human beings are not philosophical zombies. We may be wrong, but it seems so unlikely that it is irrelevant.

So if we assume other humans feel pain and pleasure, why not assume other animals also do? It would be inconsistent not to. After all, humans share a long evolutionary history with other animals, and it would be outrageous to presume that the complex processes in the brain that we experience as pain and pleasure could have developed so recently that all other animals lack it, except us. Besides, we would be left with the burden of explaining what mechanisms dictate the behavior of other animals and what evolutionary pressures could have possibly triggered the development of an entirely different mechanism in humans. Occam would turn in his grave. Another possibility is that the processes that guide our behaviors are indeed similar biochemically, but that the way animals experience those processes are categorically different from the way in which we humans do it. I don’t see any reason, however, to consider this scenario plausible other than anthropocentric wishful thinking. If we do go as far as considering this hypothesis seriously, why not consider the philosophical zombie hypothesis as seriously?

Even if you think philosophical arguments are no match for real data, empirical evidence also seems to confirm that the mechanisms of plain and pleasure that guide our behaviors guide the behavior of other animals as well. We know that the centers in the brain responsible for pain and pleasure are not exclusive to humans. Even fish exhibit behaviorally and neurologically analogous responses when subjected to stimuli that causes pain in humans, while rats and humans alike can be turned to dopamine junkies by having the reward centers in their brains stimulated artificially. We have no legitimate reason, therefore, not to presume that the experience of humans and other animals are roughly analogous. Denying that animals experience any type of pleasure during sex is as absurd as denying that animals feel pain when cut open, beaten or burned. It is an old-fashioned and dangerous Aristotelian idea that allowed thinkers as prominent as Descartes to perform vivisection on animals with a clean conscience. It has no place in a world that claims to have undergone a scientific revolution.

Teleology in biology

Non-human animals only have sex in order to reproduce

This sentence reveals a terrible but unfortunately persistent linguistic issue in the teaching of evolution: the issue of teleology in biology. In order to clarify this issue, we must ask ourselves: what does it mean to ask why an animal engages in a certain behavior? It could mean two things:

  1. What conscious intention does the animal have when they engage in that behavior? (the teleological interpretation)
  2. What is the evolutionary explanation for that behavior? (the evolutionary interpretation)

It is not uncommon to find a question that can be answered in multiple ways that are nevertheless all valid because they provide different levels of analysis. Although these levels of analysis could be potentially infinite, explanations are often divided into explanations that address proximate or ultimate causation. In our case, the teleological explanation is the proximate cause of a behavior, while the evolutionary explanation is the ultimate cause. The problem is, when we talk about animal behavior, we often mix up these two interpretations of our initial question and end up perpetuating absurd myths such as the one that only dolphins and humans have sex for pleasure. And what’s shocking is that even big names in the popular science media industry perpetuate such misinformation. I’m tired of hearing this language in Animal Planet, Discovery, National Geographic, etc.


Clearly, as I have argued above, humans, lions, dogs or any animal that reproduces sexually engage in sexual behavior with the intention of obtaining some sort of pleasure. This is the most proximate explanation possible for any behavior, and because it is always the same it is rarely interesting. I must concede, however, that the more we distance ourselves from humans in the evolutionary timeline, the less confidence we can have in our assumption that the experience of those animals is really similar to ours for any given behavior. It is even questionable whether some animals have any subjective experience at all (e.g. oysters of sea sponges), so I should note that my arguments focus on more complex animals, especially those that move.

Still, one could argue, for example, that when a fish releases sperm in the water, the experience of that fish is more akin to the experience of peeing in humans than that of orgasm. I am no specialist in fish reproduction, but for the sake of the argument, it could indeed be the case that, for fish, the experience of ejaculating is more like an experience of relief from discomfort than an experience of pleasure. This could potentially be verified by studying the brain of humans and fish. If it turns out that we have different brain regions responsible for typical sensations of pleasure such as orgasm, and another brain region responsible for relief from discomfort, such as peeing after holding it in for a long time, then we could check what area is active when a fish ejaculates and determine whether their experience is (probably) more similar to that of pleasure or to that of relief from discomfort.

In the case of mammals, however, even in the absence of such data, it is only natural to assume that their experience is similar to ours. And in the absence of the capacity to plan for the long-term, it would be absurd to speculate that any animal actually has sex with the conscious intention to procreate. Ironically, although it is often said that “non-human animals have sex in order to reproduce”, if we interpret the question as a question about intention, then humans are in fact the only species that has sex in order to reproduce, and also the only species that has sex for reasons other than. After all, only humans (in fact, only some humans) really know that sex leads to reproduction.

Another concession I must make is that, although I still maintain that all animals experience some sort of immediate gratification during at least some instances of copulation, it is indeed possible that some animals have some complex intentions. Prostitution is a perfect example. This, however, is indeed an exclusive category, for an animal requires very advanced cognitive abilities in order to be able to engage in any such behavior. Humans are clearly an example, but perhaps also penguins and chimpanzees.

Evolutionary explanations

If we interpret the question of “why animals have sex” as a question about the evolutionary origins of a behavior, however, then the answer is very different. Indeed, in this case it is fair to say that for many animals the only role of sex is the transmission of genes to the next generation. Species that only have sex during mating season and whose males only become aroused when exposed to females who are in their fertile period would be in this category.

But what about “non-reproductive sex”? In this context, this term is simply used to describe sex that doesn’t lead to reproduction. There are indeed not so many species that engage in such behavior, but still, they’re far from being only dolphins, bonobos and humans.

Animals have been observed to engage in sex for social interaction, demonstration of dominance, aggression relief, exchange for significant materials, and sexual stimulation. Observed non-procreative sexual activities include non-copulatory mounting (without penetration, or by the female), oral sex, genital stimulation, anal stimulation, interspecies mating, and acts of affection.[2] There have also been observations of animals engaging in homosexual behaviors,[3][4] as well as sex with dead animals[5] and sex involving juveniles.[6]
Non-reproductive sexual behavior in animals

Several theories have been provided to explain why certain animals engage in non-reproductive sex. These theories differ from one species to another and it’s not worth entering into detail here, but just to give a few examples, sex in bonobo communities has a conciliatory role and helps prevent conflict. In some pair-bonding species, it may help parents strengthen their bond, which in turn translates into more numerous and healthier offspring that is more likely to survive and transmit the genes further.


All animals have sex for pleasure. The experience of pleasure a chimpanzee feels when copulating is probably very similar to ours, while that of a snail is probably very different, but still all of us must experience at least some sort of proto-pleasure. However, it is true that not all animals have exclusively reproductive sex. The most common examples are indeed humans, bonobos and dolphins, but the more studies come in, the more species seem to enter this category, which by now also includes langurs, lemurs, capuchin monkeys and even lions, for example.

Note, however, that this is not to say that only these animals have sex for pleasure. Non-reproductive sex is non-reproductive sex. That’s it. It is not “sex for fun” or “sex for pleasure”. Even if a male cat only gets horny when a potential mate nearby is in heat and sending signs of fertility, still we have no basis to assume that the sex they will have is not pleasurable. In fact, as I have argued, it would be absurd to assume it is not pleasurable. If it wasn’t pleasurable, they wouldn’t do it. It’s that simple.

Humanist Voices

Official Secular-Humanist publication by Humanist Voices

Ariel Pontes

Written by

Secular-humanist, web developer, philosophy student, volunteer at @YoungHumanIntl, blogger at

Humanist Voices

Official Secular-Humanist publication by Humanist Voices