Why Women Have Sex (21 page)

Occasionally, however, there are no negative repercussions. Sometimes it can fulfill a desire:

I wanted to make the other person jealous so they’d do what I wanted them to do, so I slept with someone else. The guy I slept with was someone I wanted to screw anyway, so it worked out nicely, for me at least.

—predominantly heterosexual woman, age 25

Jealousy evocation through flirting can be an effective tactic for increasing a partner’s perceptions of desirability and consequently increasing commitment. When women have sex to evoke jealousy, however, it usually is an unsuccessful effort to correct a commitment imbalance—and fails more often than not.

My mother taught me to please my man or someone else will.

—heterosexual woman, age 37

Many times, in most of my long term relationships, I have had sex because I felt that to go for too long without sex would risk having my partner leave or go somewhere else for sex.

—heterosexual woman, age 33

Mate guarding
refers to a range of strategies, from vigilance to violence, designed to retain a partner. Having sex as a means of defending a relationship is one mate-guarding tactic. Women say they have sex because they want to keep their partners from straying and hope to decrease their partners’ desire to have sex with someone else. One woman in our study described how worried she was about the threat of mate poachers:

[I] had an ex-boyfriend that thought he was “in love” with another woman online—never even saw a picture of her, but when they talked online he lived a fantasy, so I always tried to do anything sexual to win over this fantasy woman that would tell him anything he wanted to hear, and that said she would fulfill all his fantasies. I was in a competition with someone who never actually materialized. It was all a game to her, but not to him, so I always had the thought about him comparing me to this “fantasy” and tried to outdo it all the time.

—heterosexual woman, age 41

Nor is sexual mate guarding limited to Western cultures. Among the Muria, a group residing in the Bastar region of central India, women are particularly concerned about their husbands’ straying early in the marriage: “Wives are never happy about their husbands’ visits to the
ghotul
[a sort of mixed-sex lodge for young people in which sex is common] . . . and may insist on having intercourse before their husbands leave the house, hoping to reduce the temptations that the
ghotul
offers.”

Having sex works as a mate-guarding strategy among women for two key reasons. First, it may help to keep a romantic partner sexually satisfied and sexually faithful, in both short-term and long-term relationships. As one woman noted:

I recently found out that my husband was looking into an online dating site on our computer. We had just had a new baby and everything was really crazy. We had not had sex in over nine months. (I had a very difficult pregnancy and was not allowed to have sex for some time.) I asked him about it. We fought about it. The best answer he gave me was that he was bored. I felt responsible for this so I had sex with him so he would not try to find it somewhere else.

—heterosexual woman, age 27

Second, it can serve to broadcast a woman’s sex life with her partner to others in her social circle, providing a clear signal to would-be mate poachers to stay away.

Mate-guarding strategies have been documented in a variety of species, from insects to mammals. Usually, but not always, males do the mate guarding. For example, in the veliid water strider, males ride on the backs of their mates for hours, even when they’re not copulating, to prevent other sneaky water striders from stealing their mates. Unlike most insects and other mammals, humans generally form enduring partnerships that last years, decades, or lifetimes. Consequently, both women and men are faced with the challenge of how to “hang on to” their mates.

As a highly social species, we are constantly threatened by potential mate poachers who try to lure our partners, be it for brief sexual encounters or for a more permanent relationship. We also face the risk that our partners might be tempted to leave the relationship in hopes of “trading up” to a more desirable partner. Among both dating and married couples, the Buss Lab’s research has revealed findings similar to those in our study: Women often use sex in many different ways to protect their relationships. They give in to their partners’ sexual requests in an attempt to keep them happy, they act “sexy” to take their partners’ mind off potential competitors, and they perform sexual favors or succumb to sexual pressures to entice their partners into staying. Sometimes these strategies achieve the desired function:

My husband always seems happier with [me] after we have sex when I initiate it. He spends more time with me, and doesn’t seem to gawk at other women as much.

—heterosexual woman, age 30

I guess I wanted to have sex more, before we broke up (I was a virgin at the time and we’d been going out for six months and I tend not to have the same partner for that long). So I thought I should do it actually after we’d broken up . . . so we did . . . and it somehow had the miraculous power of fixing the relationship. That sounds kind of horrible, doesn’t it? Like what kind of people are that shallow. . . . But weird, we start having sex and he starts getting way more invested in me, and acting how he should and being more protective and initiating things and so on. So maybe on a subconscious level it was to prevent the breakup from continuing as much as it was to just do it for the sake of not being a virgin anymore. Either way, it worked.

—heterosexual woman, age 24

But sexual mate-guarding tactics can also fail:

I thought at the time that I found the man of my dreams. That if I gave him sex, he would want only me. Little did I know that I wasn’t the only one giving him sex. It was not worth the hassle of trying to keep the man.

—heterosexual woman, age 37

I was young and stupid and thought sex would keep my boyfriend around. I was seventeen years old and it didn’t work. It pissed me off and taught me a lesson.

—heterosexual woman, age 40

Sometimes, having sex with someone else serves to lure a man back into the relationship, at least for a period of time, as illustrated by the following case:

My husband had an affair and his girlfriend called me to tell me the details so I joined a gym to get back in shape for him. Instead I met
a handsome, “macho” construction worker and began to see him so that my husband would leave his girlfriend. It worked and that is our pattern for the last thirty years. Sad and pathetic, I know.

—heterosexual woman, age 50

Some women who engage in “threesomes,” the most common among two women and one man, are motivated by mate guarding, as exemplified in the experiences of these women in our study:

My boyfriend . . . had always wanted to have a threesome with me and this other girl, and I had always said no. I did not want it to affect our relationship. Well, the other girl was at the same party and we started talking and kissing all over each other, right in front of him. Then me and the other girl went to an empty room and had sex.

—heterosexual woman, age 22

Right now, the guy I am with is into swinging. I am not comfortable with that lifestyle, but I love him, so I do it for him. We go to a swing club, and we have sex with other people because it turns him on. It makes him happy, so I do it for him. I just pretend he is my master and I am to follow his every command and it makes it easier for me to get through the night that way. I would never do it on my own. He keeps asking me to have a threesome with my best friend and I keep acting like it is okay, but I am dreading it. I just don’t want to have to face her in the morning and pretend like it didn’t happen.

—heterosexual woman, age 32

Of course, threesomes undoubtedly can have other motivations, such as adventure seeking or experimentation, which we explore in chapter 7. But for some women, threesomes and related sexual activities such as swinging and polyamory (the open practice of having more than one sexually and emotionally intimate relationship at one time) are attempts to make their partners happy—and to hold on to them.

Women are motivated to have sex to mate guard because the costs of not doing so can be catastrophic. A woman who fails at mate guarding can lose the support provided by her mate, whether it be material or
emotional. A woman whose mate cheats may be at risk of contracting a sexually transmitted disease, passed from her partner’s lover to her mate and then to her. She can suffer embarrassment, humiliation, and reputational damage if she is “dumped” for another. Having sex, even though it does not always work as planned, is partly designed to prevent infidelity and keep a couple from breaking up.

Many people believe affairs are morally wrong, and sexual infidelity often can be extremely destructive to the individuals as well as to the couple’s commitment. An act of infidelity causes much psychological anguish, a mix of emotions including jealousy, sadness, depression, anger, and a profound sense of humiliation. Sexual infidelity is a key cause of spouse abuse. It sometimes triggers homicidal rages. And in a study of eighty-nine cultures conducted by evolutionary anthropologist Laura Betzig, it proved to be the second leading cause of divorce, exceeded only by infertility.

Despite the damage infidelity causes, when a woman has sex with a partner other than her primary partner, her decision is driven, in part, by a collection of underlying benefits. It may seem strange to speak of “benefits” when it comes to infidelity, but bear with us. First, sex with another partner provides a person with valuable information about his or her own desirability on the mating “market”—information critical to a decision whether to stay in a relationship or leave. If the affair partner is highly desirable, that tells the person that he or she is desirable, too.

As one woman in our study said:

I felt like if he was moving on and sleeping with other people, I had to do the same, just to keep myself from getting hurt. Not only was it to keep up with what he was doing (to keep a level playing field, I guess) but also for reinforcement for me [against] my insecurity. If I felt that he didn’t find me attractive, or wanted something else, I needed to have sex with other people to prove to myself that I still was attractive and desirable.

—heterosexual woman, age 19

If the affair partner finds the woman sexually skilled and satisfying, it reveals that she should not evaluate her mate value based on unsatisfying marital sex. The affair partner also can provide a transitional relationship, functioning as a safety net that ensures some measure of protection from the psychological isolation one sometimes feels when adjusting to the often dramatic changes that come from leaving a long-term relationship:

My partner had just indicated some incredible insecurity about our relationship, so I seduced someone else just to give myself the confidence that, if I was dumped, I would still be able to find another partner.

—bisexual woman, age 20

The affair partner might not be around forever, but the sex provides a psychological boost to ease the transition.

Sometimes the affair partner becomes the love of one’s life. This is revealed by women in their stated motivations for sexual affairs. One study found that 79 percent of women who had affairs became emotionally involved with, or fell in love with, their affair partners. Although this finding may seem obvious, it is in stark contrast to the experiences of men, of whom only about a third become emotionally enmeshed. According to one study, most men’s motivations for sex outside their primary relationship are more a matter of desire for sexual variety. The importance of emotional connection for women is revealed by another key finding: Most women who have affairs are deeply unhappy with their marriages. Again, although this may seem obvious, it is not true of men. Men who have affairs do not differ from men who remain faithful in terms of their level of marital happiness! Whereas only 34 percent of women who have affairs report that their marriages are happy or very happy, a full 56 percent of men who have extramarital sex consider their marriages to be happy or very happy.

The fact is that roughly a third of all married women in Western cultures will have an affair at some point during the course of their marriage. There is a hidden evolutionary logic behind many pursued affairs.
By providing women with valuable information about their sexual desirability, affairs enhance self-esteem, often provide a beneficial transitional relationship, and sometimes allow a woman to forge a new, more meaningful emotional connection, enabling her to trade up to long-lasting love.