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The Red Queen
No hunter-gatherer society supports more than occasional polygamy, and the institution of marriage is virtually universal.
People live in larger bands than they used to, but within those bands the kernel of human life is the nuclear family: husband, wife, and children: Marriage is a child-rearing institution; wherever it occurs, the father takes at least some part in rearing the child even if only by providing food: In most societies men strive to be polygamists but few succeed: Even in the polygamous societies of pastoralists, the great majority of marriages are monogamous ones.'
It is our usual monogamy, not our occasional polygamy, that sets us apart from other mammals, including apes: Of the four other apes (gibbons, orangutans, gorillas, and chimpanzees), only the gibbon practices anything like marriage. Gibbons live in faithful pairs in the forests of Southeast Asia, each pair living a solitary life within a territory.
If men are opportunists-polygamists at heart, as I argued in the last chapter, then where does marriage come from? Although men are fickle ("You 're afraid of commitment, aren 't you? " says the stereotypical victim of a seducer), they are also interested in finding wives with whom to rear families and might well be very set on stick-ing by them despite their own infidelity ( "You 're never going to leave your wife for me, are you? " says the stereotypical mistress).
The two goals are contradictory only because women are not prepared to divide themselves neatly into wives and whores.
Woman is not the passive chattel that the tussles of despots, described in the last chapter, have implied. She is an active adversary in the sexual chess game, and she has her own goals: Women are and always have been far less interested in polygamy than men, but that does not mean they are not sexual opportunists: The eager male/coy female theory has a great deal of difficulty answering a simple question: Why are women ever unfaithful?
THE HEROD EFFECT
In the 1980s a number of women scientists, led by Sarah Hrdy, now of the University of California at Davis, began to notice that MONOGAMY AND THE NATURE OF WOMEN
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the promiscuous behavior of female chimpanzees and monkeys sat awkwardly alongside the Trivers theory that heavily female biased parental investment leads directly to female choosiness: Hrdy 's own studies of langurs and the studies of macaques by her student Meredith Small seemed to reveal a very different kind of female from the stereotype of evolutionary theory: a female who sneaked away from the troop for assignations with males; a female who actively sought a variety of sexual partners; a female who was just as likely as a male to initiate sex. Far from being choosy, female primates seemed to be initiators of much promiscuity. Hrdy began to suggest that there was something wrong with the theory rather than the females. A decade later it is suddenly clear what: A whole new light has been shed on the evolution of female behavior by a group of ideas known as " sperm competition theory. "'
The solution to Hrdy 's concern lay in her own work: In her study of the langurs of Abu in India, Hrdy discovered a grisly fact: The murder of baby monkeys by adult male monkeys was routine.
Every time a male takes over a troop of females, he kills all the infants in the group. Exactly the same phenomenon had been discovered in lions a short time later: When a group of brothers wins a pride of females, the first thing they do is slaughter the innocents: In fact, as subsequent research revealed, infanticide by males is common in rodents, carnivores, and primates. Even our closest relatives, the chimpanzees, are guilty: Most naturalists, reared on a diet of sentimental natural history television programs, were inclined to believe they were witnessing a pathological aberration, but Hrdy and her colleagues suggested otherwise. The infanticide, they said, was an "adaptation "—an evolved strategy_. By killing their stepchildren the males would halt the females ' milk production and so bring forward the date on which the mother could conceive once more. An alpha male langur or a pair of brother lions has only a short time at the top, and infanticide helps these animals to father the maximum number of offspring during that time.'
The importance of infanticide in primates gradually helped scientists to understand the mating systems of the five species of apes because it suddenly provided a reason for females to be loyal to one or a group of males—and vice versa: to protect their genetic
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The Rid Quern
investment in each other from murderous rival males: Broadly speaking, the social pattern of female monkeys and apes is determined by the distribution of their food, while the social pattern of males is determined by the distribution of females. Thus, female orangutans choose to live alone in strict territories, the better to exploit their scarce food resources. Males also live alone and try to monopolize the territories of several females: The females that live within his territory expect their " husband" to come rushing to their aid if another male appears.
Female gibbons also live alone: Male gibbons are capable of defending the home ranges of up to five females, and they could easily practice the same kind of polygamy as orangutans: one male can patrol the territories of five females and mate with them alclass="underline" What is more, male gibbons are of little use as fathers. They do not feed the young, they do not protect them from eagles, they do not even teach them much: So why do they stick with one female faithfully? The one enormous danger to a young gibbon that its father can guard against is murder by another male gibbon. Robin Dunbar of Liverpool University believes that male gibbons are monogamous to prevent infanticide:'
A female gorilla is as faithful to her husband as any gibbon; she goes where he goes and does what he does: And he is faithful to her in a manner of speaking: He stays with her for many years and watches her raise his children: But there is one big difference: He has several females in his harem and is, as it were, equally faithful to each: Richard Wrangham of Harvard University believes the gorilla social system is largely designed around the prevention of infanticide but that for females there is safety in numbers. (For fruit-eating gibbons there is not enough food in a territory to feed more than one female.) So a male keeps his harem safe from the attentions of rival males and pays his children the immense favor of preventing their murder:'
The chimpanzee has further refined the anti-infanticide strategy by inventing a rather different social system: Because they eat scattered but abundant food such as fruit and spend more time on the ground and in the open, chimps live in larger groups (a big MONOGAMY AND THE NATURE OF WOMEN
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group has more pairs of eyes than a small group) that regularly fragment into smaller groups before coming back together. These
" fission-fusion" groups are too large and too flexible for a single male to dominate. The way to the top of the political tree for a male chimp is by building alliances with other males, and chimp troops contain many males. So a female is now accompanied by many dangerous stepfathers. Her solution is to share her sexual favors more widely with the effect that all the stepfathers might be the father. As a result, there is only one circumstance in which a male chimp can be certain an infant he meets is not his: when he has never seen the female before. And as Jane Goodall found, male chimps attack strange females that are carrying infants and kill the infants. They do not attack childless females.'
Hrdy 's problem is solved. Female promiscuity in monkeys and apes can be explained by the need to share paternity among many males to prevent infanticide. But does it apply to mankind?
The short answer is no. It is a fact that stepchildren are sixty-five times more likely to die than children living with their true parents,' and it is inescapable that young children often have a terror of new stepfathers that is hard to overcome: But neither of these facts is of much relevance, for both apply to older children, not to suckling infants. Their deaths do not free the mother to breed again.