How Many Fathers are Best? dal sito DISCOVER (clicca)

usa il traduttore (clicca) .................More important, the Barí idea that biological paternity can be shared is not just the quirky custom of one tribe; anthropologists have found that this idea is common across South America. The same belief is shared by indigenous groups in New Guinea and India, suggesting that multiple paternity has been part of human behavior for a long time, undermining all previous descriptions of how human mating behavior evolved. Since the 1960s, when anthropologists began to construct scenarios of early human mating, they had always assumed that the model family started with a mom and dad bonded for life to raise the kids, a model that fit well with acceptable Western behavior. In 1981 in an article titled "The Origin of Man," C. Owen Lovejoy, an anthropologist at Kent State University, outlined the standard story of human evolution as it was used in the field—and is still presented in textbooks today: Human infants with their big brains and long periods of growth and learning have always been dependent on adults, a dependence that separates the humans from the apes. Mothers alone couldn't possibly find enough food for these dependent young, so women have always needed to find a mate who would stick close to home and bring in supplies for the family. Unfortunately for women, as evolutionary psychologists suggest, men are compelled by their biology to mate with as many partners as possible to pass along their genes. However, each of these men might be manipulated into staying with one woman who offered him sex and a promise of fidelity. The man, under those conditions, would be assured of paternity, and he might just stay around and make sure his kids survived.

Ashirokó (left), one of the oldest of the Barí, uses a shugda, the traditional spear made from palm wood, to catch fish, which account for 75 percent of the protein in their diet. His great-grandson (right) uses a spear made of rubber and metal as well as a diving mask, popular new technology from the West.

This scenario presents humans as naturally monogamous, forming nuclear families as an evolutionary necessity. The only problem is that around the world families don't always operate this way. In fact, as the Barí and other cultures show, there are all sorts of ways to run a successful household. The Na of Yunnan Province in China, for example, have a female-centric society in which husbands are not part of the picture. Women grow up and continue to live with their mothers, sisters, and brothers; they never marry or move away from the family compound. As a result, sisters and brothers rather than married pairs are the economic unit that farms and fishes together. Male lovers in this system are simply visitors. They have no place or power in the household, and children are brought up by their mothers and by the mothers' brothers. A father is identified only if there is a resemblance between him and the child, and even so, the father has no responsibilities toward the child. Often women have sex with so many partners that the biological father is unknown. "I have not found any term that would cover the notion of father in the Na language," writes Chinese anthropologist Cai Hua in his book A Society Without Fathers or Husbands: The Na of China. In this case, women have complete control over their children, property, and sexuality. Across lowland South America, family systems vary because cultures put their beliefs into practice in different ways. Among some native people, such as the Canela, Mehinaku, and Araweté, women control their sex lives and their fertility, and most children have several fathers. Barí women are also sexually liberated from an early age. "Once she has completed her puberty ritual, a Barí girl can have sex with anyone she wants as long as she doesn't violate the incest taboo," Beckerman explains. "It's nobody's business, not even Mom's and Dad's business." Women can also turn down prospective husbands. In other cultures in South America, life is not so free for females, although members of these cultures also believe that babies can have more than one father. The Curripaco of Amazonia, for instance, acknowledge multiple fatherhood as a biological possibility and yet frown on women having affairs. Paul Valentine, a senior lecturer in anthropology at the University of East London who has studied the Curripaco for more than 20 years, says, "Curripaco women are in a difficult situation. The wives come into the village from different areas, and it's a very patrilineal system." If her husband dies, a widow is allowed to turn only to his brothers or to clan members on his side of the family for a new husband.

This little boy climbs on a kirora, a wall built of stones and palm leaves that the Barí construct to entrap fish in pools and so increase their catch.

The relative power of women and men over their sex lives has important consequences. "In certain social and economic systems, women are free to make mate choices," says Valentine. In these cultures women are often the foundation of society, while men have less power in the community. Sisters tend to stay in the same household as their mothers. The women, in other words, have power to make choices. "At the other extreme, somehow, it's the men who try to maximize their evolutionary success at the expense of the women," says Valentine. Men and women often have a conflict of interest when it comes to mating, marriage, and who should invest most in children, and the winners have sometimes been the men, sometimes the women. As Beckerman wryly puts it, "Anyone who believes that in a human mating relationship the man's reproductive interests always carry the day has obviously never been married." The Barí and others show that human systems are, in fact, very flexible, ready to accommodate any sort of mating system or type of family. "I think that human beings are capable of making life extremely complicated. That's our way of doing business," says Ian Tattersall, a paleoanthropologist and curator in the division of anthropology at the American Museum of Natural History in New York City. Indeed, such flexibility suggests there's no reason to assume that the nuclear family is the natural, ideal, or even most evolutionarily successful system of human grouping. As Beckerman says, "One of the things this research shows is that human beings are just as clever and creative in assembling their kin relations as they are putting together space shuttles or symphonies."