The More Social Sex

Western culture is filled with examples of heroic male friendships. Lewis and Clark opened up the American West. James Watson and Francis Crick unveiled the DNA double helix, the secret of life. Crime-fighting duos from the Lone Ranger and Tonto to Batman and Robin have kept bad guys at bay. And what have women's friendships fostered? Cut to Carrie and her "Sex and the City" pals sipping cosmos and dishing about their boyfriends, Dolly Parton and the Steel Magnolias bawling at the local beauty salon and Rebecca Wells's Ya-Ya Sisterhood with their motto: "Smoke, drink, never think." Wherever you look, female friendships are portrayed as frivolous--significant only to the sappy parties involved.

But "girl talk," it turns out, isn't quite so trivial after all. Scientists are finding new evidence that women's friendships have played a crucial role in human evolution. Just as our ancestors shared child-care duties while men were out hunting, contemporary females come together during times of war or famine to pitch in with material and emotional support. "Female ties have evolved to ensure that certain vital functions important to life get maintained," says Shelley Taylor, a professor of psychology at UCLA and author of "The Tending Instinct." Human and primate studies suggest that friendship does for females what status does for males--that it enhances their own sense of well-being while improving their children's prospects for survival.

Not long ago it was unfashionable to think of men and women as fundamentally different. "There was a feeling that if there was any biological basis to our difference, men would tell us to get back into the kitchen," says Anne Campbell, a psychologist at the University of Durham in Britain and author of "A Mind of Her Own." But in recent years studies have shown consistently that women are better than men at reading and responding to subtle cues about mood and temperament. They're more trusting, more empathetic and more focused on one-on-one friendships.

True, girls and boys are often raised differently. But females possess many of these skills from birth. Studies performed on babies as young as 1 day old have shown that girls stare longer at human faces than at mechanical objects, while boys do just the opposite. "This difference at birth echoes a pattern we see right across the lifespan," writes Cambridge University psychologist Simon Baron-Cohen--whose lab performed many of these studies--in "The Essential Difference: The Truth About the Male and Female Brain." "On average, women engage in more 'consistent' social smiling and 'maintained' eye contact than does the average man."

Why are women wired to be more social? Evolutionists note that mutual support has helped women achieve "reproductive success"--the currency by which all life evolves. They theorize that males have evolved to compete for access to relatively scarce fertile eggs, while women have evolved to nurture whatever offspring they produce. In this scenario, natural selection would have favored the female who attracted the most social support. Other things being equal, her offspring would have stood the greatest chance of surviving to perpetuate her DNA.

The beauty of this idea is that it's testable. Do female friendships pay real dividends in the types of environment where human beings evolved? To find out, researchers Joan Silk of UCLA, Susan Alberts of Duke University and Jeanne Altmann of Princeton tracked baboons in Kenya's Amboseli basin, carefully recording the amount of time each female spent socializing--sitting near other (mostly female) baboons, or grooming them by picking insects and dirt out of their fur. As expected, the females who developed the most elaborate social networks stood the best chance of having offspring survive past the age of 2 years. The precise reasons aren't clear, but Alberts suspects that the friendly females (and their babies) were less vulnerable to predators and healthier for all the grooming they received.

These findings aren't limited to baboons. Chris Dunkel Schetter, a psychologist at UCLA, has documented a similar pattern among human mothers. In 2000 she interviewed 247 women in midpregnancy and found that those who got the most support from family and friends delivered higher-weight babies.

If women are really wired to support each other, what wiring might be involved? Scientists are currently focused on two types of hormones: oxytocin and endogenous opioids. Both are associated with feelings of relaxation and nurturing. Both are released when women are lactating, helping to bond them emotionally to their newborns. And some experts believe that the same molecules may help foster women's friendships. To test this hypothesis, Larry Jamner of the University of California, Irvine, administered oral opioid blockers to 22 men and 29 women and monitored them for three days. The men were relatively unaffected, but women's social behavior changed dramatically. The women in the nonplacebo group spent more time alone, called their friends less often and said that when they did socialize, the occasions were less pleasant than usual.

In humans and animals alike, companionship among females is a great stress reliever. Several studies have shown that married women are more likely to turn to their girlfriends than to their husbands for emotional support. A survey due out this week from Harris Interactive, Psychology Today and PacifiCare Behavioral Health shows that 45 percent of men report turning regularly to their spouses, compared with only 21 percent of women. Sue Carter, a professor of psychiatry at the University of Illinois, Chicago, has noticed a similar pattern in prairie voles--small, monogamous rodents native to the North American grasslands. When conditions are stressful, the males seek out contact with their mates, but females turn first to each other. Carter suspects that females who sidle up to their males are essentially "initiating reproduction and putting themselves under double stressors... gaining the benefit of a male partner but also the [burden]." Sound familiar?

Females can, of course, be vicious to each other. Anyone who's been through junior high or a showing of "Mean Girls" knows that. But among women, ostracism and rumormongering are more common than bricks and bats. Campbell speculates that's because the costs of physical injury and death are higher for women than for men. "If anything happens to them, there's a good chance their offspring just won't make it," she says. That's precisely why, in a woman's world, it pays to play nice.