Naturally Selective: Female Orgasm and Female Sexual Selection
Female orgasms themselves could, once again, be roughly divided into being located either deep inside or comparatively on the surface.
Every second of every day, across the face of planet Earth, there are 18,000 ejaculations of sperm, and 4.4 births. The stark reality that sperm (and the men who produce it) are biologically cheap, in comparison to eggs (and the women who bear them) is arithmetically inescapable. It is worth keeping facts like these in mind, to resist the incessant desire that humans have, to pretend that we are not, in Martin Daly’s memorable phrase, “just another critter.”
We are a sexually dimorphic species, and men and women are different. Evolution has designed us to be different. Realising that we evolved through slow steps, rather than just popping into being in an act of creation, has implications. For one thing, it means that men and women have their own separate evolutionary histories, as a result of differing (although not wholly different, of course) selection pressures. Resisting this truth—pretending that men and women are a sort of silly putty, totally moulded by social forces—has already had serious consequences in medical science, and it also has implications for my field of study.
I study the nature and function of the female orgasm. It might surprise people that there is even a set of questions about this phenomenon, but it is one of the most vexed fields in evolutionary biology. I do not claim that we have solved the puzzle of it. However, I do claim that we know a lot more about female orgasm than we used to. For example, female orgasm is multi-faceted in nature (unlike male orgasm) and is associated with a host of complex, fertility-related, functions. Male orgasm has but one (and a pretty-well understood one at that) fertility related function: reinforcing sexual behaviour. How is it that these stark differences between the sexes have been missed?
A major reason is that sex researchers, in some cases even self-described feminists, have often persisted in treating female orgasm as a mere adjunct to male orgasm. On this view—the by-product view—only male orgasms have a function. Female ones exist as a sort of afterthought of nature. Thus, clitorises have been routinely compared to (functionless) male nipples by, among others, the influential palaeontologist, Stephen Jay Gould. However, this comparison does not stand up to scrutiny. Clitorises are not substandard penises. For starters, they are large, four inches in length, on average. They are highly complex, but their structure—including muscular, erectile, and sensitive tissue—is mostly internal.
The external part—the glans—is highly sensitive, but so is the rest of it, when appropriately aroused. Clitorises connect to their own dedicated area of brain (the somatosensory cortex) utterly distinct from the male version. To see some of this for yourself you could read any number of excellent works by, for example, the brilliant anatomist Helen O’Connell.
If the structure that generates female orgasm is at least as, if not more, complex than the male counterpart, then it makes little sense to assume that the female version depends on the male one. This is doubly true of the event of orgasm itself, prompting the eminent biologist Robert Trivers to quip of female orgasms that “One has to wonder how often Steve [Gould] has been near to that blessed event to regard it as a by-product.” That may be a tad unkind—but it raises a rather important point. If we restrict ourselves to studying female orgasm, or human sexual behaviour generally, in the laboratory alone, then we run a very real risk of missing out on crucial aspects.
Let me make this point more concrete. Over the last couple of years, zoos and wildlife parks across the planet have seen a huge upswing in births, among species previously thought to be sexually frigid—like Pandas. Why? Simple. No humans were about. The animals had some privacy from prying eyes. Does it really stretch imagination to appreciate that the full range of human sexual responses might be also muted when under laboratory conditions? Inefficiency is a hallmark of good sex, and humans use the privacy of the boudoir to do more than make each orgasm as rapidly as possible. We use this space to find out about one another.
Laboratory studies are a hugely important part of science, but they are not synonymous with science. Sometimes—and especially with behavioural science—things need to be studied in as natural a setting as possible. This matters, because unless you have some very specialised tastes, laboratories are not places of romance, desire, or eroticism. It is no accident that human eroticism contains tensions about control and release; trust and risk; privacy and exposure. These are key themes that we need to know about in potential partners.
At this point someone might say, “Hold on a second. If female orgasms are so complex and enjoyable, then why are they so elusive in comparison to male ones?” Why is there, in other words, an orgasm gap? The by-product account has a ready answer to this—women are not designed to orgasm. A century ago, Freud had a similar answer, namely that women are psychologically broken (or “frigid” as he called it). However, reflection on the opening line of this article—and similar important considerations—opens up a much more interesting possibility: Women’s orgasms are choosy in exactly the same way, and for exactly the same reasons, that everything else about them in the sexual arena is choosy. In other words, female orgasmic response could be part of the vast suite of female choice mechanisms.
Robert Darby
That scene in When Harry Met Sally… (don’t pretend you don’t know the one I mean) invariably causes discomfort in men, and guffaws in women. It is a very funny scene—but it’s worth taking a moment to pick apart the dynamic here. The man is uncomfortable that the woman (and by implication other women) is only pretending to enjoy sex, while the woman has a sense of triumph about the fact that she has fooled him. Take a second to consider how odd this is. Imagine if it was a game of tennis you had had, and one partner triumphantly told you that they had only pretended to enjoy the game … that would be very curious, indeed. The natural response to this thought is that the fooling is done to placate the male ego, but this then immediately raises the question of why the male ego is so attached to his partner’s pleasure—especially when men often have a reputation for being sexually selfish.
Furthermore, why doesn’t the woman in this scenario (who in this day and age knows how to masturbate, one hopes) simply tell (and show) the man what she enjoys? Think about the reverse scenario—a man who “resists” a female seduction by “triumphantly” not getting an erection. Who would the laugh be on now? This line of thought prompts us to remember other things that men are typically sensitive about, and hence lie about while dating. These things, such as height, wealth, and status, are all things that have conspicuous fitness properties—which is just another way of saying that women select for them. Men are right to suffer from performance anxiety—they are being assessed.
Fortunately, although women may be somewhat cryptic in the bedroom, they are more than happy to talk about their sexual experiences, if you ask them nicely.
So, what did we find when we asked women (and men) directly about their experience of orgasm? At the start of my career, I was very lucky to be given access to detailed clinical data about sexual response by two Canadian giants of sex research, Kenneth Mah, and Irving Binik. They allowed us (me, and my PhD supervisor, Jay Belsky) to re-analyse their data using a technique called latent class analysis—a sort of statistical method that allows you to drop various types of data into the mathematical hopper, turn the crank, and get the data sorted into possible types based on underlying patterns. Orgasms were divided into solitary or partnered, and then subdivided by adjectival descriptions of pleasure and sensation. In brief, what we found was a lot of variation. They differed in location, intensity, and a host of other things. It was not always the case that partnered orgasms were preferred to solitary ones, for example. However, this initial study made comparisons between individuals. If female orgasms function as a test bed for partners, then what we needed to move things forward was women comparing their orgasm experiences with different partners.
We did this the next year with hundreds of women aged 18 to 84 (which is encouraging in itself) from five continents. We got a lot of data about where orgasms were located and the associated sensations, with a range of partners.
Female orgasms themselves could, once again, be roughly divided into being located either deep inside or comparatively on the surface. One interesting part was that the deeper ones had a bunch of sensations such as floating, apnea (breath catching), sense of loss of self, feelings of internal pulsing, all associated with a neurotransmitter called oxytocin. This matters because we have known for about 50 years that oxytocin is not just associated with orgasm in women, but, if it is administered artificially, it generates what is called uterine peristalsis—an internal movement of material—potentially sperm—up to the fallopian tubes.
However, these effects were not always present—not even in the same women all the time. So, we correlated these effects with partner characteristics and behaviours. Evolutionary scholars have a go-to bag of potential partner properties at this point, partly derived from observation of what people say they want in partners, and partly based on some (reasonable) guesses about what features might have been desirable in ancestral states. Were these partners especially muscular? No. Especially masculine? Not particularly—although sexual dominant behaviour did predict sexual response, as did partner considerateness, and penetrative vigour. This last one is interesting because humans, unlike some other primates, do not have a bone in their penis to help keep it erect. And (I don’t want to sound boastful here) we have the largest penises of any primate. Not largest in proportion—just the longest and most full of girth. So, the ability to keep one up, and in working order, could be an honest signal of health and vitality. However, the strongest predictor of female sexual response was none of these—it was attractive partner smell.
This will come as no surprise to, say, Jennifer Aniston, who is on record as saying that there is no better smell than that of the man you love, but it was an interesting finding to us. This is because smell appears to advertise your genome to potential partners. The science is complex, and some of it is in dispute, but there is credible research that immune system compatibility—what would make your baby healthy if you were to have one together—is signalled (both ways) by how attractive you find your partner’s smell. That women’s olfactory bulbs, the part of the brain that processes smell, are fully 40 percent denser than men’s would fit well with the knowledge that their decision-making here needs to be keener than men’s.
So, in brief, it seems that Darwin was right when he said “The power to charm females has been more important than the power to conquer other males in battle.”
Our next step was to try to measure more directly whether orgasms experienced deep inside were closely associated with retaining sperm—i.e., increasing the chances of pregnancy. This was tricky because to do it you need a controlled dose of some sort of sperm simulant (and men do not, ahem, come in controlled doses) and a way to stimulate orgasms deep inside. Eventually we devised a way to generate orgasms through deep tissue massage using the (pornography) industry standard of the Hitachi Magic Wand™ a substance with the same viscosity properties as sperm, and a device (in this case the Mooncup™) to catch material as it emerged. Initial findings were encouraging. However, they are only preliminary—although it was encouraging to hear from a fertility clinic soon after we published, who encourage their customers to maximise orgasms to increase fertility and have found solid results. It would be good to hook up with more such projects on a larger scale, maybe when the world gets back to normal.
