October 19, 2000 Harvard
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Female monogamy is fiction, not fact, Hrdy says

By Ken Gewertz
Gazette Staff

Women are naturally monogamous. Men tend to rove.

That assumption is not only part of popular belief, it has also been enshrined by science. Darwin, writing of animal mating habits, referred to the "elusiveness of females." More recently, Donald Symons, in his influential 1979 book "The Evolution of Human Sexuality," contended that it is natural for men to seek out multiple sexual partners while women are motivated to settle down with a single "good provider."

It's not true, says Sarah Hrdy.

Hrdy is Professor of Anthropology Emeritus at the University of California, Davis, and the author of "Mother Nature: A History of Mothers, Infants and Natural Selection" (Pantheon, 1999). On Oct. 12, she delivered the keynote lecture at the Radcliffe Institute for Advanced Study's first major symposium, "Gender and Inquiry."

The only reason scientists assume females are more monogamous and less sexually driven than men is that Darwin, the first and most influential writer on human evolution, unconsciously reflected the Victorian mores of his time, Hrdy said. If the theory of evolution had emerged a few hundred years earlier, when common belief assumed women to be more lustful than men, the results would have been quite different.

The assumption that females of all species tend to be less promiscuous than males simply does not fit the facts, Hrdy contended.

Among the langur monkeys of India, a species Hrdy studied extensively and wrote about in "The Langurs of Abu: Female and Male Strategies of Reproduction" (Harvard University Press, 1977), females regularly initiate sex with males outside their group and do so more often than necessary for breeding purposes. In doing so, they act in defiance of the dominant male monkey, who seeks to defend his harem of females against rival males. What is the reason for the females' promiscuity? The answer, Hrdy discovered, has to do with the tendency of dominant males to kill babies that are not their own. Since dominent males are dethroned by rivals every 27 months or so, these infanticides are quite common, so common, in fact, that, if unchecked, they would be detrimental to the langurs as a species.

But langur males are easily deceived. If a male has mated with a particular female, he will spare her infant, even if she is a member of the breeding group belonging to the male he has just deposed.

Thus polyandry, or mating with multiple males, is an advantageous breeding strategy for langur females. By mating with as many extra-group males as possible, female langurs ensure their offspring against infanticide should one of those males take over the group at a later date.

"From a mother's perspective, polyandrous behavior is assiduously maternal," Hrdy said.

Langurs are far from unique. Promiscuity serves as an effective reproductive strategy among many other species as well.

"There is abundant evidence among a range of species that females who copulate with multiple partners are more fertile," Hrdy said.

Female prairie dogs that mate with more than one male tend to have larger litters than those that mate with just one, possibly because these promiscuous females tend to be bigger to begin with. Among certain types of polyandrous European sparrows, there seems to be a direct correlation between the amount of food a male brings to the chicks and the number of times he has copulated with their mother.

These correlations can be seen even in humans. Among many South American Indians, for example, there is a belief that children can have more than one father. Studies of some of these tribes have shown that children who are acknowledged to have multiple fathers survive better than those with just one.

Looking at female promiscuity among humans, Hrdy said that "what stands out is not so much the spectacle of women having fun, but of mothers making due under difficult circumstances."

Contrary to what earlier theorists have said about the advantage of women clinging to a single mate, "it may be inopportune for mothers to rely on just one man."

Hrdy's talk kicked off a two-day round of talks at which distinquished scholars, male and female, looked through the lens of gender at a great variety of topics, including heart disease, the human genome, balancing work and family, welfare reform, power, and violence. The talks took place in Agassiz Theatre, where a capacity audience listened intently, then took part in lively question-and-answer sessions.

"This is a wonderful event," said Drew Gilpin Faust, Dean designate of the Radcliffe Institute. "It's marvelous to see all these people taking advantage of what Radcliffe has to offer."

The glimpse of fresh intellectual horizons that each of the talks revealed was also exciting, Faust said.

"Gender studies have transformed our understanding of a variety of fields of inquiry, and as a result, we have to ask questions about many things that have been taken for granted."

Mary Maples Dunn, acting Dean of the Radcliffe Institute, was equally satisfied with the way the event had turned out.

"I'm feeling very pleased," she said. "We put on our first big symposium and it drew a great crowd. People were very stimulated and excited. It's been great!"




Copyright 2000 President and Fellows of Harvard College