Homo Mysterious: Evolutionary Puzzles of Human Nature (10 page)

Such a prospect is intriguing enough. It is also consistent with the hideous practice of female circumcision, still widespread in much of northern and eastern Africa, which is based on the notion that female sexual desire could lead to multiple partners, so that for a woman to be considered marriageable, it is necessary to guarantee her fidelity by curtailing her orgasmic potential, if not eliminating it altogether.

Equally intriguing is Hrdy’s suggestion, made at the end of the quote reprinted above, that female orgasm could have been “secondarily enlisted” to enhance an existing pair bond—which leads to precisely the opposite consequence in terms of sexual partnering. There is some evidence that women are more likely to reach orgasm with familiar partners, because they are more likely to feel (and to be) safe, and thus comfortable, relaxed, able to make their needs and preferences clear, and more likely to have them met.
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Put this all together and a case might be made that rather than being an inducement for polyandry, as Hrdy proposed, female orgasm is an evolutionary sweetener for its opposite: monogamy … as Hrdy also proposed! In this regard, it is altogether consistent to have it both ways, since, as already noted, a trait can evolve for one reason, then be employed for another.

In his poem “Of the progress of the soul,” John Donne once eloquently described a young lady he admired (one Elizabeth Drury), by observing that

Her pure, and eloquent blood
Spoke in her cheeks, and so distinctly wrought
That one might almost say, her body thought.

Of course, bodies don’t actually think. Brains do. And should bodies think, they can be expected to do so in silence, as befits good thought. Mr. Donne, moreover, a now-dead white male writing four centuries ago, was probably not gesturing toward female orgasm in any case. By contrast, the 20th-century writer and feminist icon Anaïs Nin definitely was, when she referred to “Electric flesh-arrows … traversing the body,” noting how “a rainbow of color strikes the eyelids. A foam of music falls over the ears. It is,” she announced, “the gong of the orgasm.”
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With or without an accompanying gong, orgasms may sometimes appear to speak, at least to the person who occupies that body’s brain and who might stand to gain from the information thereby acquired. More than 30 years ago, the idea occurred to me that female orgasm might be a way by which a woman’s body speaks to her brain, saying something positive about her current sexual partner. I had been studying the sexual behavior of grizzly bears and was struck by the differences between subordinate and dominant males. While copulating, the former constantly swivel their heads from side to side, looking out for a dominant boar who might displace them. Not surprisingly, they ejaculate quickly, something that the sow grizzly may or may not find disappointing but which, under the circumstances, is entirely understandable and likely adaptive as well. By contrast, dominant males take their time.

I don’t know if female grizzlies experience orgasm, but if they do, with which partner would you expect it to be more likely? And is it surprising that premature ejaculation is also a common problem of young, inexperienced men lacking in status and self-confidence? Or that women paired with such men are unlikely to be orgasmic?

Interestingly, a study of Japanese macaque monkeys found that the highest frequency of female orgasms occurred when high-ranking males were copulating with low-ranking females, and the lowest when low-ranking males were having intercourse with high-ranking females.
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So maybe a woman’s orgasm isn’t elusive because it is a vestigial by-product, fickle and flaky, sometimes on and sometimes off like a light bulb that isn’t firmly screwed into its evolutionary socket. Maybe, instead, it is designed to be more than a little hard to get, adaptive precisely
because
it can’t be too readily summoned, so that when it arrives, it means something.

The evaluation hypothesis is even compatible with the fact that orgasm is more reliably evoked by masturbation than by sexual intercourse; potential partners warrant evaluation, whereas there is no comparable pressure to assess one’s own masturbatory technique. Moreover, any information made available in the former case can certainly be used to fine-tune the latter. Masturbation almost certainly is not an adaptation for reproduction in either sex; rather, it occurs just because the wiring exists—in both males and females—for orgasm based on stimulation, even in the absence of a sexual partner.

The evaluation hypothesis yields some testable predictions. One that seems so obvious as to be unworthy of testing is that women should find orgasms not only pleasurable but also important in the context of a sexual relationship. Don’t scoff: If a woman’s climax is merely an irrelevant, tag-along by-product, then it needn’t be accorded any more attention than men do their nipples. In a survey of 202 Western women of reproductive age, 76% reported that experiencing orgasm with a partner was between somewhat important and very important; only 6% said it was somewhat unimportant to very unimportant.
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If orgasm helps women evaluate their partners, then it helps make sense of the otherwise perplexing fact that female orgasm is notoriously inconsistent: It wouldn’t be much good as a means of partner evaluation if it occurred every time and with every partner. The evaluation hypothesis would also seem compatible with an attitude of control and independence. In much of the world, women tend to associate sex with submission, and interestingly, the more they do so, the more they experience impaired arousability and reduced orgasm frequency, suggesting that orgasms
have something to do with autonomy and selfhood, but in an erotic context.
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Another prediction: Compared to their socially subordinate fellows, dominant men should be better lovers, that is, more likely to evoke orgasms in their partners. And for women, experiencing orgasm with a particular partner should lead to preference for that partner. In short, after having had an orgasm, a woman would likely want more and would therefore be (adaptively) predisposed to have additional sex with the partner in question. The evolutionary outcome is that, in the absence of reliable birth control, a woman would increase the probability of being impregnated by this person. Preference for sex with a sexually satisfying lover seems so obvious that it, too, might appear a foregone conclusion, but just because it is obvious doesn’t make it any less true, or significant. In addition, it is at least possible that causation actually runs the other way: Once a woman has a preference for a particular partner (for whatever reason), she might be more likely to be orgasmic with him or her. It might be possible to disentangle these factors, but not easy.

Thus far, we have focused on those individuals who experience female orgasm directly, namely, women. But what about those who encounter it second-hand: men? Most lovers—of either sex—are interested in whether their partner experiences an orgasm. Sometimes it becomes an obsession, such that “Was it good for you?” has become a much-satirized query, susceptible to satire precisely because it is asked so often. This leads to the interesting possibility that orgasm may be important not merely for the information it provides to the woman in question, but also as a way of communicating to the partner.

And what would it communicate? The fact that many people take a partner’s orgasm as important information may itself speak to an unconscious realization that sexual response inevitably includes an evaluation component. If so, then female orgasm may help reassure one’s lover that he (or she) has passed the test, and that accordingly there is less reason to worry about infidelity.
After all, a sexually satisfied woman is presumably less likely to look for additional gratification with someone else. Although probably true, this leads to another, more cynical consideration, which may or may not be true; namely, it generates the prospect of fake orgasms.

It isn’t clear how many women fake their orgasms, or how often. But doing so could be in their interest in several circumstances: For one, it can speed up the partner’s response, useful if she simply wants to “get it over with.” For another, it could be used benevolently to enhance the other’s confidence, although such deception is likely to be erosive in the long run. Lastly—and most cynically—faking orgasm could be a ploy to mislead the partner, inducing him (or, in the case of lesbian relationships, her) to think that the woman is sexually satisfied and thus unlikely to seek other partners, as a result of which the deceived individual is predisposed to let down his or her guard, giving the faker greater leeway to pursue other relationships (in which her orgasms presumably wouldn’t be fake).

In short, women might use orgasm not only as a means of evaluating prospective partners but also as a way of manipulating them.

Returning to the more straightforward evaluation hypothesis, even though such assessment may seem limited to his or her sexual technique, ability to induce an orgasmic response could also be a cue that serves as a proxy for a more significant, ultimate evolutionary payoff: indicating something deeper about the partner’s personality and inclination toward the woman. Thus, male mammals are, in a sense, roving inseminators. Since sperm are abundant and cheap to produce, males are generally primed by natural selection to be quick on the draw and not terribly selective as to targets. (“Bim, Bam, thank you ma’am!”) Male grizzlies do not contribute to rearing their offspring. Men do—or at least, they can.

We’ve already noted that human beings are unusual in the degree to which they benefit from committed biparental care. Accordingly, perhaps an additional reason why human evolution has employed female orgasm is intimately tied to the fact that women are somewhat slower to rouse, often requiring extensive foreplay and direct, focused attention to the clitoris, which, since
it isn’t within the vagina, isn’t likely to be stimulated by a hurried and selfish male focus on penile penetration and ejaculation. This, in turn, could have set the stage for a woman to assess whether her partner demonstrates an inclination to be lovingly generous, predisposed to help meet
her
needs, rather than selfishly focus only on his pleasure. If so, then maybe he’ll also be inclined to clean up the family cave, and—a few tens of thousands of years later—mow the lawn and help put the kids through college.

Last among sexual mysteries in this chapter, as in life, we come to menopause. Less engaging than orgasm, less obvious than breasts, menopause shares more with menstruation than its first three letters (which don’t refer to male human beings, but to “month”). Like menstruation, menopause is semisecret and hormonally underwritten. It is the matching bookend to a woman’s reproductive life: from menarche to menopause. And like menstruation, menopause can also be downright troublesome, substituting hot flashes for monthly cramps.

Biologists, too, are discomfited by menopause, since it presents us with yet another evolutionary conundrum. We’ve already noted that reproduction is the
sine qua non
of evolutionary success, which makes it especially perplexing that women’s reproductive spigots are turned off at what seems an inappropriately early age. Most animals do not experience a prolonged life stage during which they are alive yet nonbreeding. So long as they draw breath, they typically release eggs. But women stop ovulating within just a few years of age 50, when they may still have a few decades of vigorous and for the most part healthy life ahead of them.

Men keep producing sperm into their eighth and even ninth decades. For women, it isn’t even a question of making eggs, since every girl is born with all the eggs she will ever have, roughly 400; they simply have to mature and then be released. The “how” of menopause is well understood. A woman’s reproductive spigot is literally turned off by a dramatic reduction in endocrine hormones, notably estrogen. But this is proximate causation. What about the “why”? Why has selection evidently favored women whose
endocrine machinery runs down when it does? What are the ultimate, evolutionary reasons?

There is no reason to suppose that age and eggs are necessarily incompatible: Female African elephants breed into their 60s and blue whales into their 90s. Not only that, but in
Homo sapiens
, eggs—unlike sperm—aren’t produced de novo throughout life. Maybe that’s the answer: At some point, each woman just runs out of eggs.

This “explanation” turns out to be no explanation at all, however, since once again it confuses proximate with ultimate causation. If there were a reproductive payoff to reproducing in one’s 50s, 60s, or 70s, you can rest assured that girls would be born with 500, 600, or 700 eggs, instead of their current 400 or so. Not only that, but women who use birth control pills—which inhibit ovulation—and who therefore only release one half to one third of the lifetime egg supply nonetheless enter menopause just like everyone else, despite having all those unused eggs, and no later than their sisters who supposedly became menopausal because they’d used up all of theirs.

More important, eggs eventually go “bad,” causing the risk of genetic defects to increase with maternal age. According to the March of Dimes, for example, a 25-year-old woman has about a 1 in 1,250 chance of having a baby with Down syndrome; a 30-year-old has a 1 in 1,000 chance; a 35-year-old, 1 in 400; a 40-year-old, 1 in 100; and a 45-year-old, 1 in 30.
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These are impressive numbers, showing that a 45-year-old woman is more than 40 times more likely to produce a baby with Down syndrome. Looked at in terms of actual risk, however, the data are much less overwhelming: Even a 45-year-old has a 29 in 30 chance of giving birth to a child who does
not
have Down syndrome! Whereas there is a genuine genetic risk to reproducing in one’s fifth or sixth decade, sheer mathematics nonetheless suggests that the potential genetic payoff greatly exceeds the possible downside.