Shadows of Forgotten Ancestors

In chimpanzee etiquette, the correct response to the male courtship display is to crouch down on the ground and lift your behind invitingly. If the social niceties should elude you at first, the male will shortly set you straight. Recalcitrant females are attacked. All males in the group expect sexual access to all females, subject to necessary exclusions enforced by jealous, higher-ranking males. (Adolescent females are available for copulation even to infant males, who are sometimes ardent lovers.) Again, a significant exception is mothers and sons; although the son may give it a try, the mother tends to resist vigorously.

It’s natural for us to think of the instant submission and compliance of these female apes as exacted under threat of bodily harm, as rape pure and simple, even if the female is not bitten or bruised. But this cannot be the whole story, because female primates raised alone will, on going into first estrus, present themselves readily to many passing males, to humans, and, occasionally, even to furniture. Not just some degree of compliance is hardwired and built in, but so is real sexual enthusiasm. As in the hamsters-in-motorcycle-jackets experiment, the females, if given a chance, often show a marked preference for the higher-ranking males: The Big Guy, he’s all right. Perhaps also the males present themselves to those of higher rank not so much as a humiliating means of social advancement but because they genuinely enjoy submission.

As with most animals, the chimp male enters the female’s vagina from behind. Often the male is in a crouching or seated position, with his hands on her waist or buttocks as she positions herself on him. To a human observer their faces are strangely expressionless. Much has been made about the difference between chimp and human sexual practices—almost certainly in an attempt to deny the closeness of the kinship. But the favorite ancient Roman sexual practice was chimp-like, the male seated on a small stool and the female, often her back to his front, settling herself down on him. The style of our hunter-gatherer ancestors (if we may judge from contemporary examples) is also more like the chimps: They are often recumbent on their sides, the male embracing the female from behind. As a fashionable human sexual practice, perhaps the “missionary position” is not much older than missionaries—although, as we’ll see later, there’s one other animal that adopted it long before they did.

By human standards chimp sexual life is a perpetual open-air orgy—compulsive, unending, and always with the male grasping the female from behind. The average copulation rate is one or two an hour. Every hour. For each mature chimp. In estrus, of course, it’s more. When the females are ovulating and able to be impregnated, their vulvas and allied nether parts swell extravagantly and turn bright pink.* In estrus, they’re walking sexual advertisements, and are then far more alluring. Because estrous periods are to some degree synchronized, there are times when a chimpanzee group is a sea of bobbing, compliant, soliciting swollen red rumps. Olfactory cues also signal their sexual availability. In marginal cases a passing male, unable to determine just by looking if she’s ovulating, may simply insert his finger into her vulva and take a sniff.

Chimpanzee sex isn’t a long and drawn-out business. Maybe eight or nine thrusts, each taking less than a second, and they’re done. The males have, by human standards, impressive recovery rates, including documented sequences of many ejaculations at five-minute intervals. Females in estrus are especially attractive in the early morning, probably because of the long and stressful celibacy imposed on the males by the necessity of having to sleep at night. As a kind of community property for the males, she may be taken every ten minutes by one male after another through mid-morning, by which time they may tire a little.

Occasionally a heroic or foolish female will refuse the male despite his transfixing stare, threatening gestures, and other signs of arousal. When he makes his approach she may scream and run away from him. Generally she doesn’t get far. When some hesitation is discerned, young males will ostentatiously search for a rock, or actually find one and make as if to throw it at her. This serves almost always as a convincing argument. One of the earliest studies of chimp sexual behavior suggested that female compliance occurs “by reason of the dominance or impulsiveness of the male and the desire of the female to avoid risk of physical injury by obeying his command.”⁷