While sociobiology is therefore useful for understanding the evolutionary context of human social behaviour, this approach still should not be pushed too far. The goal of all human activity cannot be reduced to the leaving of descendants. Once human culture was firmly in place, it acquired new goals. Many people debate today whether to have children, and many decide that they prefer to devote their time and energy to other activities. We shall reach a simiiar perspective in later chapters for other attributes as uniquely human as our sexuality, including our art and our abuse of drugs. For these activities too, one can identify animal precursors and discern original roles in promoting survival and gene transmission, but these activities also proceeded to take on a life of their own. Hence I claim only that evolutionary reasoning is valuable for understanding the origin of such human practices, and not that it is necessarily the only way to understand their current forms.
In short, we evolved, like other animals, to win the reproduction game. That contest has a single aim, to leave as many descendants as possible. Much of the legacy of that game strategy is still with us. But we have also chosen to pursue ethical goals, which can conflict with the goals and methods of the sexual contest. Having that choice among goals represents one of our most radical departures from other animals.
FIVE
HOW WE PICK OUR MATES AND SEX PARTNERS
Most humans are choosier about their sex partners than are the (other two) chimpanzees. By what criteria do we select our spouse or bedmate, and how does each of us develop our individual standard of beauty?
One evening, while I was camping with some New Guinea men of the Fore tribe, the conversation turned to women and sex, and my Fore friends proceeded to explain to me their tastes: The most beautiful women are Fore women. They have gorgeous black skin, thick, dark frizzy hair, full lips, broad noses, small eyes, a nice smell, and perfectly shaped breasts and nipples. Women of other New Guinea tribes are less attractive, and white women are unspeakably hideous. Just compare your white women with our women to see why—white skin like a sick albino's, straight hair like strings, sometimes even hair coloured yellow like dead grass or red like a poisonous snail, thin lips and narrow noses like axe blades, big eyes like a cow's, a repulsive smell when they sweat, and breasts and nipples of the wrong shape. When you get ready to buy a wife, find a Fore if you want someone beautiful.
Among the reasons I did not follow that advice was that I happen to find those 'unspeakably hideous' women attractive. But then I was conditioned by my own society's ideals, just as my Fore friends were by theirs. Darwin commented that every people he knew about—Chinese, Hottentots, black Africans, Fijians, and others—measure beauty by their own appearance. Are there really no universal rules of human beauty and sex appeal? If not, do we inherit our particular taste in marriage partner through our genes, or do we learn it by looking at other members of our society? How, really, do we pick our sex partners and spouse?
It may be surprising to realize that this problem is one that arose anew during the evolution of the human species—or at least became much more important for us than for the other two chimpanzees. As we saw in Chapter Three, our familiar human mating-system, based ideally on couples maintaining on-going involvement, is a human innovation. Pygmy chimps are the opposite of sexually selective; females mate in sequence with many males, and there is much sexual activity between females and between males as well. Common chimps are not so completely promiscuous—a male and female may sometimes go off and 'consort' with each other for a few days—but they still rank as promiscuous by human standards. However, humans are much more selective sexually, since rearing a human child is difficult (at least for hunter-gatherers) without a father's help, and since sex becomes part of the cement that differentiates co-parents from other men and women frequently encountered. Choosing a mate or sex partner is not so much a human invention as a reinvention of something practised by many other (nominally) monogamous animals with lasting pair-bonds, and lost by our chimpanzee-like ancestors. Those choosy animals include many bird species, plus our distant ape relatives, the gibbons. We saw in Chapter Four that this ideal depiction of a human society based on monogamous couples coexists with a good deal of extramarital sex. That activity also involves selection of sex partners, with adulterous women tending to be more selective than adulterous men. Thus, selection of spouses and sex partners is another important piece of what defines humanity. It is as basic to our rise from chimpanzee status as is the remodelled pelvis discussed in detail in physical anthropology texts. We shall see in the next chapter that our sexual choosiness may be central to the origin of the most conspicuous visible variability in modern humans. That is, much of what we think of as human racial variation may have arisen as a by-product of the beauty standards by which we choose our sex partners.
In addition to this theoretical interest, the question of how we select our mates and sex partners is of much personal interest. It preoccupies most of us for much of our lives. Those of us who are still unattached spend daily hours dreaming about whom we will consort with or marry. The question becomes more intriguing when we compare what turns on different people within the same culture. Think of the men or women that you find sexually attractive. If you are a man, for instance, do you prefer women who are blonde or brunette, flat-chested or buxom, and with big or small eyes? If you are a woman, do you like men who are bearded or smooth-shaven, tall or short, and smiling or scowling? Probably you do not go for just anyone, only certain types attract you. Everyone can name friends who got divorced, then chose a second spouse who was the spitting image of the first. A colleague of mine went through a long series of plain, slim, brown-haired, round-faced girlfriends, until he finally found one he got along with and married her. Whatever your own preference, you will have noticed that some of your friends have completely different tastes.
The particular ideal that each of us pursues is an example of what are called 'search images'. (A search image is a mental picture against which we compare objects and people around us in order to be able to recognize something quickly, like a Perrier bottle amidst all the other bottled waters on the supermarket shelf, or one's child at a playground with other kids.) How do we develop our private search image for a mate? Do we seek someone familiar and similar to us, or are we more turned on by someone exotic? Would most European men really marry a Polynesian woman if given the chance? Do we seek someone complementary to us so as to fulfil our needs? For instance, there undoubtedly are some dependent men who marry a mothering woman, but how typical are such pairings? Psychologists have tackled this question by examining many married couples, measuring everything conceivable about their physical appearance and other characteristics, and then trying to make sense out of who married whom. A simple numerical way of describing the result is by means of a statistical index called the correlation coefficient. If you line up 100 husbands in order of their ranking for some characteristic (say, their height), and if you also line up their 100 wives with respect to the same characteristic, the correlation coefficient describes whether a man tends to be at the same position in the husbands' line-up as his wife is in the line-up of wives. A correlation coefficient of plus one would mean perfect correspondence: the tallest man marries the tallest woman, the thirty-seventh tallest man marries the thirty-seventh tallest woman, and so on. A correlation coefficient of minus one would mean perfect matching by opposites: the tallest man marries the shortest woman, the thirty-seventh tallest man marries the thirty-seventh shortest woman, and so on. Finally, a correlation coefficient of zero would mean that husbands and wives assort completely randomly by height: a tall man is as likely to marry a short woman as a tall woman. These examples are for height, but correlation coefficients can also be calculated for anything else, such as income and IQ.