The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature (29 page)

Primate researchers still know little about what traits are preferred by male and female primates. For example, we know less about female choice in other apes than we do about female choice in the Tungara frog, the guppy fish, or the African long-tailed widowbird. Nevertheless, three kinds of female preference have been reported in primates: preferences for high-ranking males capable of protecting females and offspring from other males; preferences for male "friends" that have groomed the female a lot and have been kind to her offspring; and preferences for new males from outside the group, perhaps to avoid genetic inbreeding. Each sort of preference could be explained in terms of female choice for good genes, or female choice for material and social benefits. Although male primates have evolved an astounding diversity of beards, tufts, and colorful hair styles, there has been very little research on female choice for male appearance.

Also, there has been virtually no research on primate sexual choice for personality or intelligence. Female primates are sometimes reported to show "irrational" or "capricious" preferences that cannot be explained on the basis of male dominance, age, or group membership. Sometimes two primates just seem to like each other based on unknown features of appearance, behavior, or personality. Female primates might well be choosing males for their personalities and not just their status, but we do not know.

Most primates follow the general animal pattern of male sexual competition and female choosiness. But when the costs of male sexual competition and courtship are high, males also have incentives to be choosy When male mate choice becomes important, sexual selection affects females as well as males. In monogamous marmosets and tamarins, females compete to form pairs with quality males and drive off competing females. In single-male harem systems, the dominant male's sperm can become a limiting resource for female reproduction, and high-ranking females prevent low-ranking females from mating through aggression and harassment. In multi-male groups, females sometimes compete to form consortships and friendships with favored males. Such patterns of female competition suggest some degree of male mate choice. When the costs of sexual competition and courtship are high, males have an incentive to be choosy about how they spread their sexual effort among the available females. Males compete much more intensely for females who show signs of fertility such as sexual maturity, estrus swellings, and presence of offspring Like females, some male primates also develop special friendships with particular sexual partners. It may not be romantic love, but, at least among some baboon pairs, it looks pretty similar.

Our closest ape relatives, the chimpanzees and the bonobos, live in multi-male, multi-female groups in which sexual choice is dynamic, intense, and complicated. Under these relentlessly social conditions, reproductive success came to depend on social intelligence rather than brute strength. Both sexes compete, both sexes have dominance hierarchies, and both sexes form alliances. Sexual relationships develop over weeks and years rather than

minutes. Many primatologists and anthropologists believe that our earliest hominid ancestors probably lived under similar social and sexual conditions. Constant sociosexual strategizing in mixed-sex groups was the legacy of our ape-like ancestors. It was the starting point, not the outcome, of sexual choice in human evolution.

Pleistocene Mating

If we could look at the Earth through an extremely powerful telescope a million light-years away, we could see how our ancestors actually formed sexual relationships a million years ago. Until NASA approves that mission, we have to combine evidence from several less direct sources: the sexual behavior of other primates, the sexual behavior of modern humans who live as hunter-gatherers, the evidence for sexual selection in the human body and human behavior, and psychological findings on sexual behavior, sexual attraction, sexual jealousy, and sexual conflict. A number of good evolutionary psychology books already review this evidence, including David Buss's
The Evolution of Desire.
A consensus is emerging about the key aspects of ancestral life, though there is still vigorous debate about many details.

Our ancestors probably had their first sexual experiences soon after reaching sexual maturity. They would pass through a sequence of relationships of varying durations over the course of a lifetime. Some relationships might have lasted no more than a few days. Given that it takes an average of three months of regular copulation before conception, very short-term partnerships would probably not produce a child. Longer-term relationships would have been much more evolutionarily important because they were much more likely to produce offspring. Indeed, in the absence of contraception the longer partnerships would almost inevitably produce a child every two or three years.

Most children were probably born to couples who stayed together only a few years. Exclusive lifelong monogamy was practically unknown. The more standard pattern would have been "serial monogamy": a sequence of nearly exclusive sexual

partnerships that were socially recognized and jealously defended. Relationships may have sometimes ended amicably, but perhaps more often one partner would reject or abandon the other, or one would happen to die. This is the pattern characteristic of most human hunter-gatherers, because they do not have the religious, legal, and property ties that reinforce ultra-long-term monogamous marriages in civilized societies.

Some desirable males were probably able to attract more than one regular sexual partner. Their polygyny opened the possibility of runaway sexual selection effects. But they were probably the exception. Much more common would have been the affairs and flings that bedevil ordinary sexual partnerships. For women, there were incentives to mate with males of higher fitness than their current partner. For men, there were incentives to mate with as many females as possible (if the current partner could stand it). Yet there were probably social pressures against such dalliances from jealous partners and their families. There is plenty of evidence from evolutionary psychology that men and women have physical, emotional, and mental adaptations for short-term liaisons and adulterous affairs. The different costs and benefits of such affairs for males and females explain most of the sex differences in human psychology. In particular, the higher incentives for males to attract large numbers of sexual partners through public displays of physical and mental fitness explain why males are so much more motivated to produce such displays.

Female mate choice was powerful in prehistory. Although sexual harassment of females by males was probably common, females could retaliate by soliciting assistance from female friends, male partners, and relatives. They would not have been jailed for killing a psychopathic stalker or an abusive boyfriend. Our female ancestors lost all visible signs of ovulation, so it would not have been possible for a would-be rapist to know when a woman was fertile. Concealed ovulation reduced the male incentives for rape, and it usually protected women from conceiving the offspring of rapists. From an evolutionary point of view, it guarded their power of sexual choice. Also, rapists would have been subject to

vigilante justice by the male relatives of the victim. The power of clan members to enforce good sexual behavior is often overlooked in discussions of human evolution. Once language evolved, sexual gossip would have been a deterrent against illicit affairs, sexual harassment, and reputation-destroying rape accusations. Nevertheless, the prevalence of rape in human prehistory is still subject to intense debate. The higher the actual prevalence was, the less important female mate choice would have been, and the weaker my sexual choice theory would become.

Pleistocene Flirting Versus Modern Dating

Suppose that the level of fascination, happiness, and good humor that our ancestors felt in another individual's company was a cue that they used to assess the individual's mind and character. If an individual made you laugh, sparked your interest, told good stories, and made you feel well cared for, then you might have been more disposed to mate. Your pleasure in his or her presence would have been a pretty good indicator of his or her intelligence, kindness, creativity, and humor.

Now consider what happens in modern courtship. We take our dates to restaurants where we pay professional chefs to cook them great food, or to dance clubs where professional musicians excite their auditory systems, or to films where professional actors entertain them with vicarious adventures. The chefs, musicians, and actors do not actually get to have sex with our dates. They just get paid. We get the sex if the date goes well. Of course, we still have to talk in modern courtship, and we still have to look reasonably good. But the market economy shifts much of the courtship effort from us to professionals. To pay the professionals, we have to make money, which means getting a job. The better our education, the better our job, the more money we can make, and the better the vicarious courtship we can afford. Consumerism turns the tables on ancestral patterns of human courtship. It makes courtship a commodity that can be bought and sold.

During human evolution, though, one's ability to make a good

living did not automatically mean that one could buy a desired sexual partner good-quality entertainment. If you were a prehistoric hominid, you would have had to do the entertaining yourself. If you did not make a desired mate laugh, nobody would do it for you. And if they did, your date would probably run off with them instead of you.

The minds of our ancestors were relatively naked compared to ours. They did not spend twenty years in formal education ornamenting their memory with dead people's ideas. They did not read daily newspapers so that they could recount human-interest stories. In courtship, they had to make up their ideas, stories, jokes, myths, songs, and philosophies as they went along. There was no masking a poor imagination with a good education, or a poor sense of rhythm with a good CD collection.

Perhaps even more importantly for long-term relationships, there was no television to keep your sexual partner amused after the first blush of romance faded. If they were bored in the relationship, there was no vicarious entertainment to be had. They either had to put up with your boring old self, or find a new lover. During the Holocene, when long-term monogamy thrived, people worked much harder and longer hours doing their planting, herding, trading, and career-climbing. There were fewer hours of leisure to fill, and more ways to fill them without talking to one another. Historically, humans did not begin to put up with lifelong marriage until they could no longer live off the land, property inheritance became the key to children's survival, and couples had economic incentives to continue cooperating long after they were no longer on speaking terms. During prehistory, there were fewer economic incentives to stay together, fewer distracting entertainments to replace lost romance, and fewer ways to insulate oneself from new sexual opportunities.

Were Fathers Important?

Single mothers may have been the norm during most of human
evolution, as they were during the previous 50 million years of
primate evolution. As Sarah Blaffer Hrdy has argued in her book

Mother Nature,
human females have inherited a rich set of mental and physical adaptations fully sufficient to nurture their offspring with minimal assistance from males. Male help may have been a welcome luxury, but it was not a necessity

Many Pleistocene mothers probably had boyfriends. But each woman's boyfriend may not have been the father of any of her offspring. Or he may have been the father only of the most recent baby. Even so, his typical contribution to parenting is debatable. Males may have given some food to females and their offspring, and may have defended them from other men, but as we shall see, anthropologists now view much of this behavior more as courtship effort than paternal investment.

Viewed from the broad sweep of evolution, it is unlikely that male hominids did much direct fathering. In almost all mammals and all primates, females do almost all of the child care, with very little help from males. Males could never be sure which offspring really carried their genes, whereas females could be certain. This uncertainty about paternity leads most male mammals to invest much more in pursuing new sexual opportunities than in taking care of their putative offspring.

Like all other primates, the basic social unit among our ancestors was the mother and her children. Women clustered together for mutual help and protection. Male hominids, like males of other primate species, were probably marginal, admitted to the female group only on their forbearance. Herds of young bachelor males probably roamed around living their squalid, sexually frustrated lives, hoping they would eventually grow up enough for some group of women to take them in.

The traditional view that females needed males to protect them from predators has been challenged by an increased understanding of primate and hunter-gatherer behavior. To us, our sex differences in size and strength are salient. But to a large predator looking for an easy kill, female humans would have been only marginally less dangerous than males. Adult males may be more accurate at throwing things, but females tend to go around in larger groups while foraging, with many eyes and many hands to

offer mutual vigilance and protection. An ancestral female would have been much safer in a group of a dozen sisters, aunts, and female friends than with a single male in a nuclear family. Female humans were among the largest primates ever to have evolved, and among the strongest omnivores in Africa. They did not necessarily need any help from boyfriends only 10 percent taller than themselves. Female hominids seem unlikely to have displayed the exaggerated physical vulnerability expected of women under patriarchy. When you picture ancestral females facing predators, do not imagine Marilyn Monroe whimpering and cowering. Imagine Steffi Graf brandishing a torch in place of a tennis racket.