Why is it so hard to understand a commonplace thing like orgasms?
I think I know why science does not understand the female orgasm. It is because science excels when it breaks free of context, history, human complexities and anthropology, but when a topic requires one to grasp context, history, human complexities and anthropology, then science, especially the hard sciences, can fall short. Also, the nature of the female orgasm is a comparative question, but human sexuality is highly (but not entirely) derived; It is difficult to make a sensible graph or table comparing aspects of sexuality across mammals that usefully includes humans. It is not as impossible as making such a graph or table with “language” (which is entirely unique to humans) but still, it is difficult.
There is another problem as well. Female orgasm is actually a lot like male orgasm, and probably serves the same evolutionary role with one small but important difference. But, that one small but important difference, the ejaculation of seminal fluid by males, blinds researchers to any other function of male orgasms. Seminal fluid is distracting. Male ejaculation and female ovulation are rough homologues, but entirely different in their physiology and timing. Were it the case that female ovulation could only happen together with orgasm … well, the human world would be a very different place but at least science would not be fumbling around in search of an answer for this enigma.
Recent research on female orgasm
The reason I bring any of this up is because of a paper1, just published, that makes the claim that the “byproduct” theory of female orgasms is unsupported. So, I’d like to take a moment to explain the byproduct theory, to explain why this paper does not really address it let alone refute it, and then we’ll get back to the question of what female orgasms really are for. The byproduct theory will not survive this discussion.
The byproduct theory originates with the following observations:
1) Females can not have vaginal orgasms.
2) Vaginal sexual intercourse terminating with male orgasm is the primary evolutionary explanation for human sexual interaction; Everything else is irrelevant.
3) It is possible that some, possibly many, or even all females rarely, or perhaps never actually have orgasms anyway.
These “observations” are exactly what you expect if the following things are true:
1) Society is patriarchal.
2) Science is valued by some elite sections of society, even behavioral science and psychology.
3) Well, the rest is kind of obvious, isn’t it?
I remember with both trepidation and humor the time that a reasonably well known biologist made the public statement that females do not have vaginal orgasms. I remember thinking: Even though this is science and therefore objective measurement must have been involved, would a married hetero male check with his wife before making this statement publicly or not? But I digress.
The point is that female orgasms are being asked to be the same thing as male orgasms, and if they aren’t, then they must not have a valid purpose. However, male orgasms are misunderstood. As a result, female orgasm are being asked to meet the expectations of a dysfunctional view of male orgasms, and the result is they are seen as an evolutionary enigma.
(It may or may not be true that female orgasms do everything that male orgasms do but backwards and in high heels.)
Female orgasms just didn’t make the grade back in the middle and later part of the 20th century when various scientists were trying to work out this question. Neither did male nipples, by the way. Female nipples in humans are for nursing babies. Period. Males don’t nurse babies. Therefore male nipples are a developmental, accidental byproduct of female nipples. It was fairly easy to turn this limited view of both evolution and nipples to the problem of female orgasms and associated physiology. It is essential that males have orgasms or there would be no reproduction. Therefore there is male orgasm-related physiology. Just as males accidentally have female nipples because of a quirk of developmental biology, the theory went, females accidentally have some left over bits of orgasm-making machinery in their bodies so we end up with the occasional and largely unexpected female orgasm. But the orgasms have no adaptive purpose.
The study by Zietsch and Santtila, “Genetic analysis of orgasmic function in twins and siblings does not support the by-product theory of female orgasm” is one of those annoying twin studies. They compare orgasms between male and female twins and find out that the similarity in orgasmic function between closely related individual is not predicted by the genetic relatedness.
Ladies, it turns out that your genes did not make you come. Glad we’ve got that question taken care of.
This study, by the way, has been analyzed by Scicurious as part of her Friday Weird Science feature. Sci goes more into the meat of the study than I am doing here, so don’t miss it! See also this paper by Scicurious: “There are HOW many types of Female Orgasm?”
First, a word about sex among apes
The reason that the Zietsch and Stanttila paper is wrong, in my view, is because it asks the wrong question in the wrong way with an incorrect understanding of what they are studying and why. This paper is so wrong that I’m not even really going to critique it. Instead, I’m going to do what I implied in the title of the paper: Let’s talk about the evolutionary biology of orgasms in humans. When we’re done, the Zietsch and Santtila paper will dissolve all on its own.
Humans are apes, and most sexually mature apes (here, I’m talkin’ individual apes) have one of two kinds of sociosexual interaction with other adult apes: 1) You have sexual interaction habitually with only one individual; or 2) you have sexual interaction habitually with more than one individual. For example, a male silverback gorilla has sex with a list of females, but each of those females has sex with only one male (the silverback). Gibbon males and females have sex habitually with only one other individual. And so on. You can work this out in detail for each kind of ape as homework.
Note that I said “habitually” and that’s important. A given individual who habitually has sex with only one other individual may occasionally break that rule. This does not mean that the rule is gone, or that a common pattern is of no relevance. This does not matter a lot to the present conversation but I find that discussions of primate sexuality often break down the moment someone not versed in the subject learns that monogamy is often not as monogamous as they thought. The fact that monogamy is not what you thought does not mean that it does not exist. OK, back to the point.
Whether or not an ape follows pattern 1 or 2 depends proximally on one factor.2 This most immediate factor is simple propinquity. A female gibbon typically has sex with one male gibbon, habitually, because there is only one male gibbon in the territory that she defends and lives in. A female gorilla typically mates only with her silverback because he’s the only one, and not just in the country western love song kinda way, but literally … he is the only sexually mature male anywhere around. Meanwhile, the silverback mates with any and all sexually mature females in the same group because they are there, and they are there because the apes have arranged themselves on the landscape that way on purpose.
Within the context of a social group there may be patterns and preferences and there is without doubt a complex primate-political dynamic. But, as interesting as that may be, it is for the moment a distraction. Assume for now the simple case: Adult sexually mature apes mate with the other adult sexually mature apes that are around.
Therefore, the actual mating behavior of apes is determined by social geography. If you watch what apes are doing much of the time, it turns out that other than eating and sleeping, they are spending a great deal of time manipulating their social geography at all spatial scales. If that thought has never occurred to you before, let it sink in. This should be a major can’t-turn-back “aha!” moment for you. If you are not having that moment, think about this until it happens. It’s OK to take your time with this.3
There are many important differences in all aspects of behavior between, say, monogamous pairs of gibbons and polygynandrous troops of chimpanzees. These different systems of mating (called by behavioral biologists “Mating Systems”) relate to very important biological variables such as but not limited to: Body size, growth rate and timing, defensive physiology and behavior; primary food types; fallback food types; limbic and other brain functions and communication; tooth enamel thickness and distribution; penis size; testicle size and sperm production rates; and so on and so forth.
And this all comes down to how the apes manipulate their social geography. This determines mating system, which in turn interacts with feeding ecology, and feeding ecology and mating system together relate to and mostly determine absolutely everything else of interest to behavioral biologists.
Who has sex with whom is very important in the behavioral biology of the apes. It has been shown in many studies that the way in which apes interact in groups impacts their fitness, and it is likely that many features of ape social structure that are shown to be more or less similar across groups are adaptations that arise from selection for certain behaviors, both in straight forward traditional biological sense (i.e., alleles that cause specific phenotype are selected for/against) and in the more modernized form of behavioral biology (which allows for additional routes of transmission of fitness enhancing information). It is hard to say that chimpanzee hand-salute or leafing behavior, both symbolic communicative activities, are specifically adaptive, but it is likely that the chimpanzee ability to do and interest in doing these things facilitates various kinds of inter-individual bonding which becomes very directly relevant to fitness in other areas of chimp life, in areas that are literally determining life, death, and reproduction.
In general, this is probably true of mating systems of mammals (and birds as well). Social interactions are critical and related to fitness, and they are mediated through drives, proclivities, limbic sensibilities that are fine tuned or shaped at the genetic level and to varying degrees (in primates and especially apes, and to a lesser degree in social carnivores) by cultural transmission.
That mating systems in apes are generally adaptations has not been seriously questioned by behavioral biologists for decades. The details, however, are still very much under investigation, and the study of mating systems in humans has been hampered by those pushing for human exceptionalism (of all sorts, including the “we are too cultural to have adaptations” arguments as well as the “god made us different” arguments which often come from totally opposite quarters) as well as by the “evolutionary psychologists” who have muddied the waters in human behavioral biology by having theory that is half pretty good, half totally wrong.
The evolution of sex and marriage in human ancestors
But what if the feeding ecology required a different social geography than the mating system? Well, it does for most, possibly all apes! This is something Wrangham and Smuts revealed in their seminal study way back when4. For example, fruit-eating apes need to forage apart because fruit is rare and dispersed. But if “mate guarding” is important, then they need to forage together to keep an eye on things. One solution to that is to create very serious territories and then eat and or have sex with whatever is in that territory. That would be chimps. Apes that eat more low quality food which is less dispersed and more abundant can get into bigger groups to forage and thus gorilla-like mating systems evolve. Apes that eat higher quality and more dispersed and hard to find food can’t do that. I could go on and on about the conflicts between diet and sex.
So, a theory came along a while back presented in a paper by Richard Wrangham, Jamie Jones, Me, David Pilbeam and Nancy-Lou Conklin-Brittain.5 I’m not going to toot my own horn or anything, but this paper and the idea it suggests have certain interesting characteristics: 1) Everyone who is anyone these days thinks it is either correct or could be correct (it has become textbook knowledge); 2) the paper is in the top ten cited ever in the flagship anthropology journal in which it is published (i.e., among the highest impact factors ever for any paper in any field); 3) As time goes by I start to believe it is probably mostly correct!
The idea has to do with the origin of cooking and changes in hominid social structure connected to that. Never mind the details. And, in fact, if you look at the original paper, you’ll probably see a version of this idea that I would revise today. The point is this: Human ancestors, just under 2 million years ago, underwent an ecological change that required that they live in multi-male multi-female groups, like chimps do, but that also resulted in selection for a mostly monogamous (or at least, less poygynandrous) mating system, kinda like gibbons have today, but really, not very different from typical modern human marriage.
But this causes a major conflict, more than is found in any other ape species, between the ideal social geography for mating and the ideal social geography for eating. In apes, the sexual landscape is determined by hard working apes making sure that the social geography is just right. But the ideal social geography for what we might call “proto-marriage” conflicts with the geography required for cooking and all that it entails. So something new had to be introduced to make the system work. Several new things, including what we know of today as human sexuality. Let’s look at some of the details.
Did you know that humans are the only ape where males always lack a penis bone? In order for a male to ejaculate (typically) he has to have an orgasm, and the orgasm requires a certain amount of stimulation of the penis which pretty much only works in connection with erection. Also, the erection is pretty much required for intromissive sex. With all this emphasis on erection, why is there not a penis bone? Obviously, human male sexual interaction has been tied more closely to longer term and more intensive erotic interaction to produce and maintain an erection despite the lack of the internal hard part to make that happen more easily, quickly, and effectively. Human males typically take much longer to achieve their orgasm than their ape counterparts.
Do you see what I’m getting at? Male sexuality involves a much more elaborate, longer term, and complex set of psycho-sexual-social elements than usually found in apes, that are linked to social bonding. There are of course all sorts of exceptions, but typical, normal adult male human sexuality is actually somewhat complex and nuanced and not ape-like in many ways. Yes, folks, compared to Pan trogoldytes, our nearest relative, human male sex is all about relationships. If you were thinking otherwise, this would be a good time to recalibrate.
Meanwhile, female sexuality has its own very strange differences in humans. For instance, human females are sexual even when they are not ovulating. Human females are set up, psycho-sexually and physically, for non-reproductive sex. That is not a typically ape feature.
Meanwhile, human males have another strange quirk: Relatively speaking, compared to our nearest living relative and presumably our common ancestor, human males find females who are not ovulating to be sexually attractive. Sure, there are some studies that might show that human males are more attracted to ovulating females, but the fact that you have to do carefully controlled studies and then look very closely at the data to see a pattern like this (if it even exists) should not be ignored: If human males were primarily attracted to ovulating females and not very interested in non-ovulating females, then that would be easily seen and demonstrated.
And, of course, females are adapted to this quirk of males. And so on back and forth. Human sexuality is highly complex, interactive, and typically involves attention to long term relationships. This is how we get something vaguely like a sexual gibbon living in the world of an ecological chimp.6
And female orgasms are like male orgasms but more so. They are part of human attraction, bonding, social commitment, pairing off, long term relationships, and ultimately, generating and maintaining two landscapes … sexual and ecological … in one system. (It is not a very large step from this point to understand homosexuality, but that would be a digression at this time.)
Once you’ve calibrated your understanding of human sexuality in males, it is an easy matter to understand female sexuality a bit differently than it is usually framed in evolutionary biology. In the old model, male orgasm was a simple delivery system for sperm. In pop-level evolutionary biology (a.k.a. “Evolutionary Psychology” as per David Buss and Steve Pinker), males will, shall we say, make love to mud (i.e. are indiscriminate and primarily seek novelty, etc. etc.) because every single ejaculation could make a baby even though ejaculations are easy to come by. Throw in a little patriarchic male-biased thinking and female orgasms are left with nothing important to do. They become a sexual vestigial feature in the minds of some biologists.
But in the new model, which includes our revision in understanding human ecology, long term and somewhat complex relationships are critical in raising offspring. These relationships are hard to manage in apes because of the old ape rule … the sexual landscape is mapped on the actual geographical landscape which is a product of the interaction of individuals and their feeding ecology. Therefore, social mechanisms evolve.
And part of the human social adaptive suite is proto marriage in earlier Homo and what we today call marriage, and part of that is human erotic behavior, which does very much involve orgasms. Every body’s orgasms. Even females!
1Zietsch, B., & Santtila, P. (2011). Genetic analysis of orgasmic function in twins and siblings does not support the by-product theory of female orgasm Animal Behaviour DOI: 10.1016/j.anbehav.2011.08.002
2I just want to point out that you don’t see a pun using the word “proximate” every day.
3What I just said actually applies to mammals in general, but I’m trying to stay focused on apes to keep it relatively simple.
4See for example:R.W. Wrangham and B.B. Smuts. 1980 Sex differences in the behavioural ecology of chimpanzees in Gombe National park, Tanzania. Journal of Reproduction and Fertility supplement 28:13-31 and R.W. Wrangham. 1987. The evolution of social structure. In B.B. Smuts, D.L. Cheney, R.M. Seyfarth, R.W. Wrangham, and T.T. Struhsaker (Eds.). Primate Societies, pp. 282-296. Chicago: Chicago University Press.
5R.W. Wrangham, J. H. Jones, G. Laden, D. Pilbeam and N.L. Conklin-Brittain. 1999. The raw and the stolen: cooking and the ecology of human origins. Current Anthropology 40: 567-594. You can get a copy here.
6I should say something about bonobos because you may be thinking that I missed the fact that there is another apes species that could be thought of as “erotic.” Consider that bonobos are not like our Last Common ancestors with chimps: Like humans, bonobos are also derived in their sexual behavior. Don’t think of them as a human evolutionary stage. Also, bonbo sex is not the same as human sex. Briefly, bonobo erotic interactions fill the same role as agonistic interactions in common chimps, but instead of “I’ll bit you if you do/don’t do that” it is “I won’t give you oral sex if you do/don’t do that.” Sure, there are probably parallels in human interaction, but to the extent that there are the next point I make subsumes them. Even common chimps are fairly sexy. They don’t have “reproductive sex” that isn’t, well, reproductive but they do various erotic things just not as elaborately as bonobos. The thing is, common chimps do not use relationships that have a strong erotic/sexual componant to organize their society, except a little. It is not a requirement that for a set of traits to be “derived” in humans there can be zero representation of anything like them in chimps. One would not, in fact, expect that to be the case.