Marriage and Civilization

5 million years ago, the East African climate grew drier and the tropical forest receded, leaving treeless patches that eventually opened into the current vast savannas. Onto these open grasslands ventured our common ancestors who, if they were not identical to the chimpanzees of today, were much more chimp than they were human. Recent research suggests that they may have first survived in this sparse environment by digging roots deep out of the ground and that the sticks they used for this task may have been the first human “tool.” They were only about three feet tall, no bigger than today’s baboons.

What differentiates gibbon couples from human beings is that they are purely antisocial. They do not want other couples around. As they settle down to raise offspring, their songs become duets. These gibbon duets serve a very distinct purpose. They warn other males and females out of their territory.

They are purely monogamous. Gibbons court each other by singing eerie, high-pitched songs that can be heard half a mile away. If a male and female like each other’s song, they rendezvous in the forest, do a brief mating dance, and then copulate up to five hundred times over the next forty-eight to seventy-two hours, forming a tight sexual bond. (An immediate period of intense sexual abandon is what characterizes all monogamous species.)

The fifty to two hundred members of a savanna baboon troop are arranged in concentric circles, with the older and dominant males alongside the fertile females. As they reach maturity, the younger males are expelled to the perimeter of the troop, where they form a kind of Praetorian Guard to protect the troop from predators. Over the course of the next several years, the young male baboon will engage in endless status quarrels as he gradually attempts to work his way back toward the center. Not all this involves fighting. Younger males often form alliances that improve their chance of advancement. Having a high-status mother also helps as she often influences her sons’ progress. One way or another, however, it is a long and arduous journey from the periphery to the center where mating takes place, often consuming five to ten years. In his 1970 book, The Social Contract, playwright-turned-anthropologist Robert Ardrey chronicled this eloquently in an often-excerpted chapter, “Time and the Young Baboon.”

Baboons are much smaller than gorillas, orangutans, or chimps, standing only three feet tall and weighing less than fifty pounds. Despite their diminutive size, the savanna baboon has been able to abandon the forest, where the hamadryas baboon still lives, and move out onto the East African grasslands where they have survived in an environment filled with predators, particularly the leopard, which relishes baboon meat. Baboons survive in the same manner that African antelope, wildebeest, and other grazing animals do—by forming large herds that offer protection in numbers. But there is a difference. Unlike these herbivores, baboons have developed a complex, hierarchical, almost military social system.

Males attract females by singing. Upon pairing off, a couple may travel together for as long as a week, copulating all the while, but soon part ways. Infants remain with their mothers until age five and males play no part in rearing the offspring. Orangutans reach sexual maturity around age twelve. Their rather indolent lifestyle has much limited the orangutan’s range. Their habitat is rapidly diminishing as Borneo and Sumatra cut down rainforests and, like the gorilla, they are being pushed to the brink of extinction.

Orangutan mating patterns resemble the casual couplings of the most disorganized human societies. Their lifestyle has been described as “solitary but social.” Except for mothers caring for their youngsters, neither males nor females move in groups but wander the forest alone. If a young male encounters a female in estrus, he will force copulation—“orangutan rape.” The females do not like this and often seek protection from the more dominant males. At about age twenty males grow “flanges” on the side of their cheeks that expand to make their heads appear bigger. The size of the flanges usually determines dominance.

Gorillas live deep in the forests of Central Africa, far removed from any potential predators. They weigh between four hundred and five hundred pounds and are entirely vegetarian, munching up to fifty pounds of leaves a day. The silverback gorilla collects between four and eight females in a harem. He sometimes tolerates the presence of one or two subordinate males, to whom the females often allow secret sexual favors. They are now threatened by loss of habitat.

Now the chimp “primal horde” seemed as if it must have been the original template. Still, this left us with the question, how could chimp polymorphous polygamy have evolved into human monogamy?

polymorphous polygamy,” as chimp mating came to be called, completely rearranged our assumptions about human evolution.