Sex at Dawn

evolved in the human female to facilitate and sustain the

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long-term pair bond at the heart of the nuclear family. Once you’ve swallowed that story, it becomes problematic to admit that the females of other primate species are orgasmic, too. Your problem gets worse if the most orgasmic species happen to be the most promiscuous as well, which appeares to be the case.

As Alan Dixson writes, this monogamy-maintenance explanation for female orgasm “seems farfetched. After all,” he writes, “females of other primate species, and particularly those with multimale-multifemale [promiscuous] mating systems such as macaques and chimpanzees, exhibit orgasmic responses in the absence of such bonding or the formation of stable family units.” On the other hand, Dixson goes on to note, “Gibbons, which are primarily monogamous, do not exhibit obvious signs of female orgasm.”¹⁹ Although Dixson classifies humans as mildly polygynous in his survey of primate sexuality, he seems to have doubts, as when he writes, “One might argue that ... the female’s orgasm is rewarding, increases her willingness to copulate with a variety of males rather than one partner, and thus promotes sperm competition.”²⁰

Donald Symons and others have argued that “orgasm is most parsimoniously interpreted as a potential all female mammals possess.” What helps realize this “potential” in some human societies, argues Symons, are “techniques of foreplay and intercourse [that] provide sufficiently intense and uninterrupted stimulation for females to orgasm.”²¹ In other words, Symons thinks women have more orgasms than mares simply because men are better lovers than stallions. Stomp your foot three times if you believe this.

In support of his theory, Symons cites studies like Kinsey’s showing that fewer than half of women questioned (Americans in the 1950s) experienced orgasm at least nine out of ten times they had intercourse, whereas in other societies (he refers to Mangaia, in the South Pacific), elaborate and extended sexual play result in nearly universal orgasm for women. “Orgasm,” Symons concludes, “never is considered to be a spontaneous and inevitable occurrence for

females as it always is for males.” For Symons, Stephen Jay

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Gould, Elisabeth Lloyd, and others, some women have orgasms sometimes because all men do every time. For them, the female orgasm is the equivalent of male nipples: a structural echo without function in one sex of a trait vital in the other.

Given all the energy required to get there, it’s surprising that

the female reproductive tract is not a particularly welcoming

place for sperm cells. Researchers Robin Baker and Mark

Bellis found that approximately 35 percent of the sperm are

ejected within half an hour of intercourse and those that

remain are anything but home free.²³The female’s body

perceives sperm as antigens (foreign bodies) that are promptly

attacked by anti-sperm leucocytes, which outnumber sperm

100:1. Only one in 14 million ejaculated human sperm even 24

reach the oviduct. In addition to the obstacles imposed by the female’s body, even those lucky few sperm are going to run into competition from other males (at least, if our model of human sexuality has any validity).