fate.
WHY PLAY SEXUAL MONOPOLY?
But the polygamy threshold is a bird-centric view. Those who study mammals take a rather different view, for virtually all mammals lie so far above the polygamy. threshold that the four commandments are irrelevant: Male mammals can be of so little use to their mates during pregnancy that it need not concern the females whether the POLYGAMY AND THE NATURE OF MEN
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males have already married. Humanity is a startling exception to this rule. Because children are fed by their parents for so long, they are more like baby birds than baby mammals. The female can do a great deal better by choosing an unmarried wimp of a husband who will stay around to help rear the young than by marrying a philandering chief if she has to do all the work herself. That is a point to which I shall return in the next chapter. For the moment, forget people and think about deer.
A female deer has little need of a monopolized male. He cannot produce milk or bring grass to the young. So the mating system of a deer is determined by the battle among males, which in turn is determined by how females decide to distribute themselves.
Where females live in herds (for example, elk), males can be harem masters. Where females live alone (white- tailed deer), males are territorial and mostly monogamous: Each species has its own pattern, depending on the behavior of the females: In the 1970s zoologists began to investigate these patterns to try to find out what determined a species ' mating system. They coined a new term, 'socioecology,' in the process. Its most successful forays were into antelope and monkey society: Two studies concluded that the mating system of an antelope or a primate could be safely predicted from its ecology. Small forest antelopes are selective feeders and, as a consequence, are solitary and monogamous: Middle-sized, open-woodland ones live in small groups and form harems. Big plains antelopes, such as the eland and African buffalo, live in great herds and are promiscuous: At first a very similar system seemed to apply to monkeys and apes. Small nocturnal bush babies are solitary and monogamous; leaf-eating indris live in harems; forest-fringe-dwelling gorillas live in small harems; tree-savanna chimps live in large promiscuous groups; grassland 22
baboons live in large harems or multimale troops.
It began to look as if such ecological determinism was on to something: The logic behind it was that female mammals set out to distribute themselves without regard to sex, living alone or in small groups or in large groups according to the dictates of food and safety. Males then set out to monopolize as many females as
possible either by guarding groups of females directly or by defending a territory in which females lived. Solitary, widely dispersed females gave a male only one option: to monopolize a single female 's home range and be her faithful husband (for instance, the gibbon). Females that were solitary but less far apart gave him the chance to monopolize the home ranges of two or more separate females (for instance, the orangutan): Small groups of females gave him the chance to monopolize the whole group and call it his harem (for instance, the gorilla). He would have to share large groups with other males (for instance, the chimp).
That picture has been complicated by one factor: A species '
recent history can influence what mating system it ends up with: Or, to put it more simply, the same ecology can produce two different mating systems depending on the route taken to get there. On Northumbrian moors the red grouse and the black grouse live in virtually identical habitats. The black grouse prefers bushy areas and places that are not too heavily grazed by sheep, but apart from that, they are ecological brothers: Yet the black grouse gather in spring at spectacular leks where all the females mate with just one or two males, those that have most impressed them with their displays. They then rear their young without any help from the males.
The nearby red grouse are territorial and monogamous; the cock is almost as attentive to the chicks as the hens: The two species share the same food, habitat, and enemies, yet have entirely different mating systems. Why? My preferred explanation, and that of most biologists who have studied them, is that they have different histories. Black grouse are the descendants of forest dwellers, and it was in the forest that their maternal ancestors developed the habit of choosing males according to genetic quality rather than territory:'
HUNTERS OR GATHERERS
The lesson for humanity is obvious: To determine our mating system we need to know our natural habitat and our past: We have lived mostly in cities for less than one thousand years. We have POLYGAMY AND THE NATURE OF MEN
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been agricultural for less than ten thousand: These are mere eye blinks. For more than a million years before that we were recognizably human and living, mostly in Africa, probably as hunter-gatherers, or foragers, as anthropologists now prefer to say. So inside the skull of a modern city dweller there resides a brain designed for hunting and gathering in small groups on the African savanna.
Whatever humanity 's mating system was then is what is ' natural '
for him now.
Robert Foley is an anthropologist at Cambridge University who has tried to piece together the history of our social system: He starts with the fact that all apes share the habit of females leaving their natal group, whereas all baboons share the habit of males leaving their natal group: It seems to be fairly hard for a species to switch from female exogamy to male exogamy, or vice versa. On average, human beings are typical apes in this respect even today. In most societies women travel to live with their husbands, whereas men tend to remain close to their relatives: There are many exceptions, though: In some but not most traditional human societies, men move to women.
Female exogamy means that apes are largely devoid of mechanisms for females to build coalitions of relatives. A young•
female chimpanzee generally must leave her mother 's group and join a strange group dominated by unfamiliar males: To do so, she must gain favor with the females that already live in her new tribe.
A male, by contrast, stays with his group and allies himself with powerful relatives in the hope of inheriting their status later: So much for the ape ' s legacy to mankind: What about the habitat in which he lived? Toward the end of the Miocene era, some 25 million years ago, Africa 's forests began to contract. Drier, more seasonal habitats—grasslands, scrublands, savannas—began to spread. About 7 million years ago the ancestors of mankind
