Who says only one sperm gets the prize?

People in at least 18 societies around the world believe that a child can have more than one biological father, anthropologists now report.

A woman with such beliefs considers the men with whom she has sex during pregnancy as contributing some measure of paternity, and she may publicly acknowledge extramarital lovers as secondary fathers, says Stephen Beckerman of Pennsylvania State University in State College. He presented the latest tally of beliefs in so-called partible paternity at the annual meeting of the American Association for the Advancement of Science last week in Anaheim, Calif.

Before anyone gets smug about the centuries-old Western belief in one father per baby, Beckerman points out that microscope studies didn't confirm the idea for animals until 1879. "It was just a lucky guess [for] Western folk biology."

Diverse societies believe in multiple dads. Most are in South America, with some in India and New Guinea. For example, the Canela in Brazil believe that a fetus keeps incorporating sperm until birth, says William H. Crocker of the Smithsonlan Institution's National Museum of Natural History in Washington, D.C. Traditionally, extramarital sex was "rampant and socially correct," he says, and a pregnant woman sought affairs with men she wanted her baby to resemble.

The idea of partible paternity "seems to be much more common than we'd ever thought," says Paul Valentine of the University of East London. He encountered it among the Curripaco in Venezuela and Columbia. The group opposes extramarital sex but employs partible paternity to resolve conflicts. A wife can appease her husband by stating that he is her baby's main father even though she had sex with a lover.

Partible paternity may benefit children. Among the Bari of Venezuela and Colombia, Beckerman found that 80 percent of kids with extra fathers lived to age 15, in contrast to 64 percent of children with lone dads. Pregnant women with lovers also had less risk of miscarriage, possibly because courtship gifts boost nutrition.

The widespread belief in partible paternity raises doubts about a key factor in what Beckerman calls the standard model of human evolution: the "evolutionary bargain" in which men hunt for family food in return for guaranteed paternity.

Sarah Blaffer Hrdy of the University of California, Davis sees partible paternity as yet another challenge to misleading stereotypes--"the coy female and the ardent male"--in animal evolutionary theory.

Sharing paternity must also have its dark side, observes David M. Buss of the University of Texas at Austin, who Studies jealousy (SN: 10/12/91, p. 232). In cultural surveys, "one myth that's been shot down is that there are cultures that don't have sexual jealousy," he says. Crocker, for example, reports suppressed jealousy even among the Canela, where extramarital sex has been sanctioned.

Partible paternity could hit close to home, notes R. Robin Baker, who did infidelity research at the University of Manchester in England. "If Britain recognized partible paternity," he says, "between 4 and 10 percent of children could claim multiple fathers."