Pop culture paints the female orgasm in contradictory light, which flickers through waves of sexual liberation. On one hand, some heterosexual male characters like How I Met Your Mother’s Barney Stinson completely disregard women’s sexual needs, treating them as vessels for their own egotistical pleasure. On the other hand, women like Samantha Carr from Sex and the City are sexually liberated, empowered by their ability to sustain multiple orgasms in quick succession. In any case, the female orgasm has more: more potential, more elusiveness, and more complexity than its male counterpart.

“Human women produce the egg regardless of sexual satisfaction”

Why do women have them? Men orgasm and ejaculate to shoot sperm into a vagina (in fact, male orgasm and ejaculation are two separate phenomena, worthy of their own discussion), after which sperm can swim to an egg which can be fertilised to give rise to more humans. But human women produce the egg regardless of sexual satisfaction. How does a woman’s enjoyment of sex to the point of sustaining a changed conscious state and experiencing involuntary muscular contractions benefit our species?

Pleasure

The most intuitive evolutionary explanation for the female orgasm is that enjoying sex will make women have it more, increasing chances of pregnancy and thus leading to more sex-enjoying offspring with every generation. However, orgasm is not always about making babies, nor is it entirely psychological. Procreation is not the whole story. And that fact is not limited to humans.

Bonobos, one of our closest ape relatives, are notorious for enjoying sex. This is asserted by primatologists not only because they appear to have sex regularly, emoting extensively while doing so, but also because bonobos have gay sex (which cannot lead to babies). Females will engage in mutual clitoral stimulation, known as genito-genital (G-G) rubbing, in greeting or before sharing food. It is no surprise bonobos are dubbed ‘hippie apes’. It is unclear whether G-G rubbing tends to lead to orgasm, or if this is the intention: primatologists do occasionally respect personal boundaries of their subjects, it seems. However, sexual pleasure does convincingly play a role in social bonding beyond human society.

While most human beings may not be as sexually liberated as these great apes, it is obvious from the existence of contraception that sex between humans is not always about babies. Nor does it always result in orgasm, and orgasm is not always the point. Especially among humans, the role of sexual pleasure and orgasm in social bonding is incredibly variable, influenced by culture and personal values, and it is not my role as an author to tell you what it means to you. Allow me instead to guide you to consider the biology of orgasm: what might the physiological roles be?

Insemination

One of the most clinical ideas put forward to explain the female orgasm is known as ‘upsuck’. It was suggested that the muscular contractions brought about as part of the female orgasm would propel sperm towards the egg, a little like extruding a Calippo. This does seem to happen in pigs and macaques. While applying the same logic to humans doesn’t sound entirely absurd, the experiment which disproved it does: Masters and Johnson, the scandalous scientific duo behind early human studies of sexual responses, recruited women and presented them with artificial sperm laced with chemicals which would show up dark on an x-ray. The participants were instructed to masturbate while x-ray images were taken. No evidence was found for the fluid being vacuumed up from where it was placed in the cervix into the uterus. In short, the female orgasm does not seem to increase the chances of pregnancy occurring from sex.

“The female orgasm does not seem to increase the chances of pregnancy occurring from sex”

In non-human species, sex does induce changes in the female which are required for pregnancy. Rabbits, for instance, only ovulate, releasing the egg from the ovary into the uterus, in response to sex. We cannot call this orgasm: who are we to assert what the rabbit feels? ‘Fall off’, where the male rabbit momentarily loses consciousness as he literally falls off his partner’s back, is the end of rabbit sex and, rather amazingly, does seem sufficient to induce female ovulation (do both rabbits climax simultaneously?).

A 2019 article considering whether this process is related to human female orgasm gave rabbits human antidepressants known to reduce human female sexual function. This reduced rabbit ovulation following copulation by 30%, suggesting a common mechanism to human orgasm and rabbit ovulation. Perhaps we evolved from induced ovulators, and later evolved the more regular menstrual cycle, but retained some psychological reaction to sex. This would have happened in parallel with stricter mate selection: induced ovulation increases chances of pregnancy given sex, but in more complex social groups it can pay for a female to have fewer babies, devoting more energy to each one. So while orgasm does not improve chances of pregnancy directly, it may have done so in our ancient ancestors. Do human women merely enjoy the remnants of ancient physiology?

The spectacular diversity of clitoral anatomy in species with fixed (as opposed to sex-induced) ovulation demonstrates that this is not a sufficient explanation. From the female hyena’s penis-like clitoris to the dolphin’s large clitoris placed much closer to the vagina than its human counterpart, diversity of form indicates that natural selection has acted specifically on the hotspot of female sexual pleasure.

Despite efforts to reduce the female orgasm to a reproductive function, the importance of its psychology is undeniable. Perhaps orgasm first evolved in tandem with the brain-involving mechanisms of induced ovulation, maximising chances of pregnancy after sex. However, once this physiological role was overwritten by the menstrual cycle, orgasm prevailed. From that point onwards, sexual pleasure may have dictated the diverse evolution of the clitoris to be tailored to the sexual habits of different species, humans included. Female sexual pleasure has hence become a driving force in sexual evolution.