The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature (34 page)

Moreover, many male humans with strong homosexual desires get married and produce offspring, as Oscar Wilde did. Many female humans with strong lesbian desires produce children too. Evolution has no moralistic motive to punish homosexual behavior. As long as homosexual behavior does not displace heterosexual behavior, it has little impact on evolution. Homosexual behavior—as an adjunct to heterosexual behavior—would be expected to evolve whenever its fitness benefits (making friends, appeasing threats, making peace after arguments) exceed its costs (energy, time, and the increased risk of sexually transmitted disease).

Our hominid ancestors might have been almost exclusively heterosexual, like chimpanzees, or very homoerotic like bonobos. We do not know. Even male chimpanzees hold each other's penises for comfort when they are frightened. Perhaps, like bonobos, humans evolved some adaptations for homoerotic flirtation and same-sex sexual friendships. If the social benefits of homosexual relationships were strong enough, homosexual preferences could, in principle, have shaped human physical

appearance and mental capacities. However, these preferences had no direct reproductive consequences, so they would have had much weaker evolutionary effects than heterosexual preferences. As a result, we have to focus on heterosexual behavior when considering the role of sexual choice in the mind's evolution.

Mate Choice and Courtship as Social Events

Sexual choice and courtship in human evolution was not just a matter of boy meets girl. We have seen that our ancestors were highly social primates living in groups with children, relatives, and friends. Sexual relationships began and ended within family and tribal contexts.

If mate choice favors good genes, it can be useful to meet a potential mate's blood relatives, because they share some of the same genes. An individual's kin give additional information about their heritable fitness. If an intelligent man has foolish brothers or a beautiful woman has ugly sisters, this may lower their attractiveness as potential parents of one's children. Siblings share half of their genes, as do parents and offspring. The apparent fitness of a woman's mother or daughter carries half as much information about the woman's own genetic quality as her own fitness indicators. Given two sexual prospects who appear to display equal fitness, the one whose relatives appear healthier, brighter, more attractive, more fertile, and more successful probably has higher actual fitness. Since our ancestors tended to live in kin groups, there were plentiful opportunities for mate choice to take into account this sort of kin quality. Our mate choice systems would have evolved to exploit this gold mine of genetic information.

If sexual choice paid attention to the fitness of a potential mate's relatives, then those relatives would have been under sexual selection to display high fitness. This would have been a much weaker pressure than ordinary sexual selection, but it could still have been significant in shaping our instincts for display. If parents could help their offspring attract better mates by appearing intelligent, healthy, and successful, then the copies of their

own genes that are carried in their offspring would benefit. Likewise, if children could help their mothers appear more attractive by demonstrating that they carry good genes, then the copies of their genes in their mothers would be passed on to larger numbers of half-siblings. Any courtship effort that helps your relatives to find good mates helps your own genes to spread. (Of course, there may be conflicts of interest between relatives over these courtship displays, as when adolescents wish that their parents made more effort to act reasonably cool when their friends visit, or divorced parents wish that their adolescents would behave better towards potential stepparents.)

Mate choice that takes into account the qualities of a potential mate's relatives would have favored hominids who spread their courtship effort out across their lifetimes. In childhood and old age their courtship would be vicarious, carried out on behalf of their relatives. In the prime of life it would be mostly for themselves, but also for their sexually active relatives. We should not expect to see fitness indicators used exclusively after puberty and before menopause, only that they are then directed at different targets.

Vicarious, collective courtship by relatives might explain why humans are so good at producing certain kinds of cooperative display. Evolutionary psychologists have usually assumed that human cooperation evolved for survival benefits. Cooperation can certainly help the cooperators survive better—if they are doing something that is actually useful together. But what about religious rituals, dances, and feasts that have high time and energy costs and no credible survival payoffs? Consider the huge Thanksgiving feasts that American families organize when a daughter first brings home a potential husband. The family members are not improving their collective survival chances; they are improving the daughter's mating prospects by demonstrating their wealth, health, family size, and other aspects of familial fitness. The prodigious waste of uneaten turkey even follows the predictions of the handicap principle. Across many cultures, marriage rituals serve similar functions, wasting vast resources so

that a kin group can display its fitness to a group of possible inlaws. American families also advertise their wealth and status by producing costly rituals when one of them reaches sexual maturity—as in bar mitzvahs, debutante balls, and "sweet sixteen" parties. Rich parents even advertise familial fitness by paying over a hundred thousand dollars for each child to attend a private university, whereas in Britain, they pay even more for pre-university private schooling.

Modern human families compete to attract good mates for their young people. Perhaps Pleistocene kin groups and tribes did so too, inventing various rituals, myths, legends, totems, and dances to display their superiority over other groups competing in the same sexual market. To the extent that mating occurred across group boundaries, cooperative group activities may have evolved as collective courtship displays through sexual selection. This may explain the observation by anthropologists Chris Knight and Camilla Power that a great deal of human ritual behavior consists of collective displays by female relatives on behalf of their youngest female kin when they reach sexual maturity. Of course, once the mental capacities for collective fitness displays evolved through sexual selection, those capacities might prove useful for other functions as well, such as intimidating rival groups competing for the same territories and resources.

So much for collective courtship. As for collective sexual choice, each individual's mate choice decisions probably took into account the views of their parents, siblings, offspring, and companions. Sometimes they may have immediately discounted this advice, realizing that their relatives' interests did not coincide with theirs. But sometimes other individuals would have offered useful information about a potential mate. They may have interacted with the prospect in other contexts, or heard useful gossip. Older relatives may have offered words of wisdom from their past experience of sexual choices and sexual relationships. During the Pleistocene, when social conditions were less volatile than today, one generation's experiences of courtship and parenting would have been much more relevant to the next generation. Before the

evolution of language, relatives could have revealed their attitudes about a sexual prospect through the usual primate signals: threat displays and attacks, or friendly grooming and food sharing After language evolved, the relative merits of sexual rivals must have become subjects of impassioned discussion. Parents may have been especially vocal about their views, because the sexual choices of their children were so important to the number and quality of grandchildren who would carry their genes. However, parental influence on sexual choice does not imply some sort of arranged marriage system in which sexual selection no longer operates. On the contrary, by integrating information from several individuals our ancestors could have made much more accurate estimates of each prospect's strengths and weaknesses, driving sexual selection more strongly in particular evolutionary directions.

Biologists have not developed models of how sexual selection works when mate choice and courtship are socially distributed. I would guess that the runaway process would not work so strongly when sexual preferences and sexually selected traits are spread across different bodies. It would have a harder time establishing the genetic correlations between preferences and traits that drive runaway. However, there may be fewer such problems with sensory bias effects and preferences for fitness indicators. For example, the sensory and cognitive biases of friends and relatives could influence an individual's sexual choices just as their own biases would. Ornaments and indicators could still evolve even if parents were choosing sexual partners for their children, and even if aunts were producing courtship displays on behalf of their nieces.

Afrocentrism

It should go without saying, but I'll say it anyway: all of the significant evolution in our species occurred in populations with brown and black skins living in Africa. At the beginning of hominid evolution five million years ago, our ape-like ancestors had dark skin just like chimpanzees and gorillas. When modern
Homo sapiens
evolved a hundred thousand years ago, we still had

dark skins. When brain sizes tripled, they tripled in Africans. When sexual choice shaped human nature, it shaped Africans. When language, music, and art evolved, they evolved in Africans. Lighter skins evolved in some European and Asian populations long after the human mind evolved its present capacities.

The skin color of our ancestors does not have much scientific importance. But it does have a political importance given the persistence of anti-black racism. I think that a powerful antidote to such racism is the realization that the human mind is a product of black African females favoring intelligence, kindness, creativity, and articulate language in black African males, and vice versa. Afrocentrism is an appropriate attitude to take when we are thinking about human evolution.

7

Bodies of Evidence

By primate standards, humans look strange, even after we step out of our sport utility vehicles. Compared with other apes, we have less hair on our bodies, more on our heads, whiter eyes, longer noses, fuller lips, more expressive faces, and more dextrous hands. In most species, sexual ornaments like long head hair, hairless skin, and full lips would have evolved only in males, because females would have been the choosy sex. Males have few incentives to reject any female mates. The fact that both human sexes evolved distinctive sexual ornaments shows that both female choice and male choice was important in human evolution. If both sexes were choosy about bodies, they might also have been choosy about minds.

Not only do we look different from other apes, but each human sex also has distinctive body traits shaped by sexual selection. Men are taller and heavier on average than women, with more upper body strength, higher metabolic rates, more hair, deeper voices, and slightly larger brains. Some of these traits may have evolved for sexual competition against other males. But male bodies are also living evidence of the sexual choices made by ancestral females. Men grow beards, and possess penises that are much longer, thicker, and more flexible than those of other primates. These are more likely to reflect female choice than male competition. Women also evolved to incarnate male sexual preferences. Women have enlarged breasts and buttocks, narrower waists, and a greater orgasmic capacity than other apes.

Sexual selection has also made male bodies grow according to a higher-risk, higher-stakes strategy. For males there is a higher

incidence of birth defects, more death in infancy, higher mortality at every age, earlier senescence, and greater variation in health, strength, body size, brain size, and intelligence. This risky, go-forbroke strategy suggests that sexual competition among males was often a winner-takes-all contest. It was better to take a big gamble on producing the most attractive image during a short peak, rather than aiming to create a mediocre impression over a long period of time.

Our bodies are rich sources of evidence about sexual selection pressures because they are visible, measurable, easily comparable with those of other species, and relatively undistorted by human culture. In recent years much nonsense has been written by post-modern theorists such as Michel Foucault about the "social construction of the body," as if human bodies were the incarnation of cultural norms rather than ancestral sexual preferences. These theorists should go to the zoo more often. What they consider a "radical reshaping" of the human body through social pressure is trivial compared to evolution's power. Evolution can transform a dinosaur into an albatross, a four-legged mammal into a sperm whale, and a tiny, bulgy-eyed, tree-hugging, insect-crunching proto-primate into Julia Roberts—or Arnold Schwarzenegger. Selection is vastly more powerful than any cosmetic surgeon or cultural norm. Minds may be sponges for soaking up culture, but bodies are not.

The most sexually selected parts of our bodies have been neglected in theories of human evolution because they don't fossilize. Sexual choice sculpts body ornaments out of muscle, fat, skin, and nerves, often without leaving many clues in the bones. This makes it hard to know when and where these traits evolved. We don't know how hairy our ancestors were a million years ago, whether
Homo erectus
males had huge penises, or whether Neanderthal females had large breasts. But we do know that our body's sexual ornaments are universal across human groups, so they must have evolved at least 60,000 years ago or so, when human groups colonized different areas of the world. In these respects our bodily ornaments are like many of our mental