Pleasing Her: sexual evolution?

I came across an interesting article in the magazine Science a while back. I am always intrigued when a paper tries to place an issue in its ontological context, although I have to confess that the title had something to do with catching my eye. It was a scientific theory from seemingly reputable sources about the evolutionary significance of the female orgasm.  The article to which it refers is more detailed and helpful, but somewhat difficult to read; to get a more comprehensive description of the process however, I will include it here for reference:

Orgasm is a topic that seldom surfaced through all the years of my gynaecologic practice; it was something that many women felt too embarrassed to mention –especially to a male doctor. It was also a subject that I felt ill-prepared to tackle –apart from standard psychological advice of dubious merit, the only benefit seemed to be that of a sympathetic, nonjudgmental hearing. Little was known about either the function or the physiology of orgasm, so advice about its production was more anecdotal than beneficial; it was therefore usually the purview of sexual dysfunction clinics rather than that of the general gynaecologist.

The only thing that seemed on a firm basis with regards to orgasm was that it was essential in males for sperm transfer. Clitoral stimulation is usually required for the production of female orgasm, and since the penis and clitoris share a homologous origin perhaps it was simply a fortuitous consequence of this –a secondary adaptation (exaptation) for the purposes of bonding, or the like.

But to place female orgasm on a more secure footing, the authors have looked at reproduction in other animals. ‘The essential condition for the success of internal fertilization is the timely maturation and release of the oocytes from the ovary into the female reproductive tract, that is, ovulation, for the egg to be accessible to sperm. These events need to be coordinated with the availability of males and favourable environmental conditions for raising the young.’ And for such, there are roughly three factors that might influence induction of ovulation in mammals: environmental –cues that suggest it would be a favourable time for successful rearing of offspring such as weather, food sources, etc.; copulation induction –only produce valuable eggs when they’re needed –i.e. when a mate is available; and spontaneous ovulation –no matter the availability of mate or suitable environment. Humans, it would seem, utilize the latter option –spontaneous ovulation.

In copulation-induced ovulation, a surge of two hormones in the female are required –prolactin, and to a lesser extent oxytocin. Interestingly, these are also produced during human female orgasm, although with spontaneous ovulation in humans, they are not specifically required. As the authors suggest: ‘The orgasm in women does not obviously contribute to the reproductive success, and surprisingly unreliably accompanies heterosexual intercourse. Two types of explanations have been proposed: one insisting on extant adaptive roles in reproduction, another explaining female orgasm as a byproduct of selection on male orgasm, which is crucial for sperm transfer.’ In other words, ‘Human female orgasm is associated with an endocrine surge similar to the copulatory surges in species with induced ovulation. We suggest that the homolog of human orgasm is the reflex that, ancestrally, induced ovulation. This reflex became superfluous with the evolution of spontaneous ovulation, potentially freeing female orgasm for other roles.’

There is another aspect of the study that fascinated me –something that had not registered despite my years as a gynaecologist: ‘With the evolution of spontaneous ovulation, clitoral stimulation lost its role in ensuring fertilization simultaneously with the removal of clitoris from the copulatory canal, likely causing a variable association between copulation and orgasms for the female.’

Think about it. Why would the homologue of something important for ovulation in some species, and so important for orgasm in ours have moved away from the action? The clitoris is now located quite a distance from the vagina and is only inadvertently stimulated with human heterosexual intercourse. I think the Science article expressed it well: ‘Humans and other primates don’t need intercourse to trigger ovulation—they evolved to a point where it happens on its own—but the hormonal changes accompanying intercourse persist and fuel the orgasms that make sex more enjoyable, the biologists hypothesize. And because those hormonal surges no longer confer a biological advantage, orgasms during intercourse may be lost in some women. This explanation “takes away a lot of stigma” of underwhelming sexual relations, says one of the authors, Mihaela Pavlićev, of Cincinnati Children’s Hospital in Ohio.’

And also: ‘Pavlićev and Wagner’s theory helps explain why female orgasms during intercourse are relatively rare. “It is new to use [this] innovative, Darwinian approach to understand one of the mysteries of human sexuality—why the male orgasm is warranted, easy-to-reach, and strictly related to reproduction and the female counterpart [is] absolutely not,” says Emmanuele Jannini, an endocrinologist at University of Rome Tor Vergata. The nonnecessity of orgasms for reproduction may also explain why women’s reproductive tracts vary a lot more than men’s—there are fewer constraints, he adds.’

I have to admit that this was all terra incognita to me. And a clarification and reassurance for those few women who confided concerns about their difficulties or even inability to achieve orgasm with heterosexual intercourse seemed impossible if it was supposed to be part of the process. Surely they weren’t all psychologically liable… So-called foreplay was clearly important –if only to stimulate both the clitoris as well as interest in the procedure- but was there something wrong with them if he couldn’t be persuaded?

Satisfactory sexual experience is clearly important and helps to provide the glue that bonds a relationship. But does the changed anatomy tell us anything? Might we be permitted a secular Darwinian postulate that pleasure may, after all, be divorced from the procreative imperative? A sort of anatomical excuse? Much can be done to wrap this in a more attractive package -the counselling of both partners as well as suggestions on technique- but at least from an evolutionary perspective that seeks to propagate our species, we’re doing just fine. Maybe too fine, in fact…






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