Born to Be Good: The Science of a Meaningful Life

It does not take a great leap of the imagination to recognize human leks—junior proms and Sadie Hawkins dances, bars, nightclubs, Bible study groups, coffee and copy machines at the office, singles hikers in the Sierras, activist meetings—where desire is negotiated according to our own ancient patterns of courtship. This ancient language of desire catapults us, heads spinning, into reproductive relations. Before cataloguing this language of desire, it is worth considering two underappreciated qualities of human desire that might be taken for granted. The first is that human desire channels us into monogamous bonds. This is not the trajectory of desire in our closest primate relatives. In gorillas, resource-rich alpha males lord over harems, while other males do their best to sneak in surreptitious copulations—like those elephant seal beta males. In chimpanzees, all is quiet on the sexual front until the female goes into estrus. At this time she most typically mates indiscriminately with dozens of males each day, often requiring up to 3,000 copulations prior to pregnancy. And bonobos wage an all-out, polyamorous Haight-Ashbury lovefest, using sex for just about every purpose: to reproduce, to form friendships, to help share food, to play, to pass the time.

Putting aside your bonobo envy, it is important to appreciate that human desire, at least in the moment, is singular. It is oriented toward one person; it pair-bonds. The most obvious reason for this is that our big-brained, ultravulnerable offspring required multiple caretakers, including fathers. Another factor, suggests Matt Ridley in The Red Queen, is our love of meat. Some 1.6 million years ago, our foraging, group-dwelling hominid predecessors started eating meat. The provision of meat is a probabilistic affair, and bound males into dependent trade relations. This focus of early hominid dietary activity prevented any single male from hoarding all the resources—a precondition for harems—and kept early hominids in pair-bonding relations.

If you need further proof of our pair-bonding predilections, just look at a few males’ testicles. In species with polygamous females, males have outsized testicles that produce copious amounts of sperm to win in the game of sperm competition with other males. Thus, in chimps, with their promiscuous females, the male’s testicles on average are two times larger than those of the gorilla, whose females mate in serial and monogamous fashion with one alpha male. In the right whale, whose females are polygamous, the testicles of the male weigh half a ton, or 1 percent of its body weight (two pounds on a 200-pound human). The right whale’s testicles greatly outweigh those of the male in the pair-bonding gray whale. Human testicle size reveals us to be more on the pair-bonding end of the continuum. Sexual desire is the rocket booster that moves us toward that arrangement.

Human desire is just as remarkable in that it leads to sex and intimacy unrelated to procreation. Long before the birth control pill revolutionized intimate life by freeing sexual behavior from reproductive outcome, the same was happening in human evolution. Females of our closest primate relatives advertise their reproductive readiness with swollen, colorful sexual regions—displays that shock and astonish in the primate section of your local zoo. Human females, in contrast, have evolved concealed ovulation. As a result, women and men do not necessarily know whether their desire will lead to reproductive outcome (although a woman is more likely to initiate sex, masturbate, have affairs, and be accompanied by her husband during ovulation; and pole dancers earn bigger tips, Geoffrey Miller has recently found, at the peak of their ovulation). Concealed ovulation evolved, we now know, to prevent stepfather infanticide, which is unnervingly common in mammals, and seen in many rodent species, lions, and many primates. Concealed ovulation keeps males guessing about whether offspring are theirs, thus reducing the likelihood of infanticide. Concealed ovulation also allows women and men to have sex throughout the female’s cycle—an ongoing incentive for the male to remain in a relationship and contribute to the raising of such resource-dependent, vulnerable offspring.

The specific language of desire, which propels potential partners toward one another, has been documented by Givens and Perper. These researchers spent hundreds of hours hiding behind ferns and jukeboxes, laboriously documenting four-or five-second bursts of nonverbal behavior amid the lambent light and Lionel Richie tunes of 1980s singles bars. They homed in on those microscopic behaviors that predict whether women and men will pursue a romantic encounter—a shared drink, an exchange of phone numbers, leaving the bar with buoyant step, arm in arm.