This is my evolution column for this week. It will also run in Monday’s Philadelphia Inquirer:
A while back, a reader wanted me to investigate whether there was an evolutionary explanation for women sleeping around.
He didn’t come at the question directly, but asked me to look at female low self-esteem and evolution. I pressed on how such low self-esteem was manifested, and that’s when the sex question came out. He said he was worried about his daughters.
The exchange left me with an interlocking series of questions: Why do some women sleep around? Does sleeping around have anything to do with self-esteem? And finally, why do some people associate female (but not male) promiscuity with low self-esteem?
One piece of this puzzle was solved by Cosmopolitan magazine editor and Sex and the Single Girl author Helen Gurley Brown, who died last week at 90. Sex, she pointed out, is fun and it feels good — or at least it can if you follow the tips and advice offered by Cosmopolitan. Why wait till you’re married to be in on the enjoyment?
But pleasure and fun get at only part of the question. In the real world, sex is not as simple as throwing a cocktail party. It comes with risks — of disease, unintended pregnancy, tarnished reputation, heartbreak, stalkers, and bedbugs, to name a few. What tips the risk/benefit balance for women in favor of what scientists call short-term mating? And does self-esteem play any role?
Self-esteem can be connected to sex, said Bobbi Low, a behavioral ecologist at the University of Michigan. Women sometimes use short-term sex to boost self-esteem because they can, she said. Women who are unappreciated by their partners might indeed enjoy a confidence boost after a fling with someone more attentive. This is harder to pull off for men, she said, since flagging male confidence is a turnoff. “Nobody wants to sleep with a wuss,” said Low.
Low said there are a couple of biological factors underlying differences in male and female mating behavior. Women are the ones who end up gestating the offspring — and so, in evolutionary terms, it is “costly” to get knocked up by a loser who can offer neither good genes nor help feeding the child. Natural selection therefore favors some pickiness in women. Men, on the other hand, have less at stake.
Which may explain a few things about Brown’s life. According to the obituary in the New York Times, she admitted she didn’t consider herself attractive. At 5-foot-4, she weighed barely 100 pounds and was given to bouts of acne and irrational fears of getting fat. She described herself as a “mouseburger” — meaning an unattractive woman with poor marriage prospects — though she did marry. None of that got in the way of her sex life.
Low said that human mating psychology isn’t hardwired, but can be shaped by culture and other environmental factors, from demographics to life expectancy to food availability to technology. Groups that make a living raising animals tend to be very male-dominant and controlling of women, and so are farming groups that have acquired a plow. But people who engage in simpler farming techniques and some hunter-gatherers such as the Inuit show more open attitudes about short-term mating by women, as well as single motherhood, divorce, and cohabitation among unmarried couples.
University of Texas evolutionary psychologist David Buss agrees that environment matters, and adds that short-term mating tends to increase when there are more women than men in a population. That can be explained in part because the males in such populations feel less need to commit and settle down.
A baby boom can have the same effect because men tend to choose mates three to five years younger than they are. A bump in the overall population can lead to an effective excess of females in the most sexually desirable age bracket.
And so it may be no coincidence that the sexual revolution of the 1960s coincided with the coming of age of a large baby boom. Another big factor is life in big cities, said Buss, because short-term mating tends to have a negative impact on women’s reputations, especially if they live in small groups. In New York City, much more can be kept secret.
Buss, too, was intrigued by Brown’s life. He shares with her an interest in female sexuality; his latest book is titled Why Women Have Sex: Understanding Sexual Motivations from Adventure to Revenge (and Everything in Between), coauthored by Cindy Meston. Buss said he was particularly intrigued with the way Brown recommended that single women have sex with other women’s husbands. In the jargon, this is called mate poaching, he said. It’s not that people don’t do this, but they rarely advertise it.
When it comes to mating, humans are more complex and varied than our fellow great apes. “We have a mixed menu of mating strategies,” Buss said, which include short-term and long-term mating and everything in between.
Across cultures, women engage in short-term mating for several reasons. Some do it because they meant to engage in long-term mating but it didn’t work out. Other women do engage in flings to boost confidence, especially when stuck in a bad relationship. Such women may need a self-esteem boost to get up the courage to break away and move on, he said. Psychologists have studied this, he said, and the evidence suggests that it often works.
Contact Faye Flam at 215-854-4977 215-854-4977 or firstname.lastname@example.org, or follow on Twitter @fayeflam. Read her blog at philly.com/evolution.