When Men Behave Badly: The Hidden Roots of Sexual Deception, Harassment, and Assault

by David M. Buss

Although it is easy when thinking about the “battle of the sexes” to fall into the trap of thinking about sexual conflict in terms of men as a group against women as a group, an evolutionary perspective illuminates why that framing is misleading. Sexual conflict is mostly about individual men and individual women interfering with each other in ways ranging from deception in internet dating to sexual harassment in the workplace to sexual coercion by strangers, dates, and mates.

Men can produce a child with the mere act of sexual intercourse and no further investment. Women require a costly nine months of internal gestation to produce that same child.

Within each sex, however, there exist large individual differences. Some men and women have a strong desire for no-strings casual sex; others opt for monogamy with their “one and only.” Some women and men practice the art of deception in the mating game; others opt for honest courtship. Some people remain sexually faithful; others have affairs whenever the opportunity arises. Some sexually harass co-workers with impunity; others are appalled at workplace misconduct.

To a nontrivial degree, we are all locked in the interior of our own minds. We use introspection about our minds to infer the inner landscape of other minds. Because the sexual minds of men and women differ in some respects, these inferences lead to predictable mind-reading errors.

Although the labels and cultural movements are new, the underlying conflicts they reveal are ancient. The battle of the sexes may be traced back in time through human evolutionary history, through primate and mammalian evolutionary history, and even to the origin of sexual reproduction itself 1.3 billion years ago.

Every person alive struggles with sexual conflict. Most of us see only the tip of the iceberg—dating deception, a politician’s unsavory sexual grab, the slow crumbling of a once-happy marriage, a romantic breakup that turns nasty. These flash points make big news when their players are prominent—consider the sexual scandals of Bill Cosby (imprisoned), Al Franken (resigned from Congress), Harvey Weinstein (imprisoned), Bill O’Reilly (fired or resigned), Matt Lauer (fired or resigned), Charlie Rose (fired or resigned), or Jeffrey Epstein (imprisoned followed by death due to suicide or murder).

Social scientists struggle to explain why women and men seem so much at odds with each other. Popular explanations blame patriarchy, masculine hegemony, and toxic masculinity. Men, some scholars argue, maintain a vise grip on power and resources, put up glass-ceiling barriers, and exclude women from the old-boys’ club. Manosphere bloggers, on the other hand, blame women who seek sex wit...

Masculinity does indeed have toxic elements. It is no secret that men have a virtual monopoly on sexual harassment, sexual assault, and crass sexual objectification of women. Patriarchal institutions such as laws that give husbands control over their spouses’ sexuality, for example, are still on the books in some countries and have lingering pernicious effects in others. On the other hand, it is also true that women, as many in the manosphere claim, tend to be attracted to men who have power, status, influence, and resources.2 Some women spurn or ignore men lacking high-status attributes; some men feel invisible when it comes to women. Missing from these manosphere accounts, however, is that women’s mate preferences are enormously complex and include qualities such as honesty, intelligence, dependability, moral character, sense of humor, and many more.

the principle of sexual conflict coevolution. For every tactic one sex evolves to exploit the other, there exists at least one coevolved defense in the other.

Sexual conflict theory—the idea that traits beneficial to the reproductive success of individuals of one sex can damage individuals of the other sex, resulting in coevolutionary arms races of offenses and defenses—has been applied almost exclusively to understanding sexual interactions among insects. Male reproductive organs of some species, such as water striders, possess penile spines that damage the female reproductive tract during mating. Black widow spiders cannibalize their mates after copulation if they fail to flee fast enough, using male bodies as meals for their offspring. Male fruit flies inseminate proteins upon ejaculation that induce female ovulation, reduce her sexual receptivity to other males, compromise her immunity, and shorten her life span.

The incel mantra about women’s rejection of beta males echoes the sexual frustration of spider males who lose in their mating efforts by failing to wrap their gifts in an attractive-enough package.

Studies of online dating sites have discovered that most men find many women to be attractive, showing a roughly normal bell-shaped distribution. In contrast, most women find the average man to be below threshold, showing attraction mostly to men in the top 20 percent.

On Tinder, for example, many men “swipe right” on dozens or hundreds of profiles each day, hoping that one or a few might respond in kind. In contrast, one woman who used Tinder exclusively for short-term mating told me that she swiped right on less than 0.8 percent of men she saw on the site and hooked up with only 0.6 percent of those, resulting in a minuscule 0.005 percent of men she saw on the dating app.

Female choosiness—deciding who qualifies for interaction, relationship escalation, and sexual access—is a good candidate for the first principle of mating, and this book will explain why. But it is precisely this female selectivity that creates one key form of sexual conflict, sometimes expressed as resentment from men who fall below threshold.

Men and women need each other. Cooperation is a cardinal feature of successful reproduction. We fall in love, mutually choose each other, consent to sex, and sometimes commit to a lover over the long run. If we produce children, each partner has an equal evolutionary stake in their welfare.

Consider the simplest case—a difference between the male and female perspectives on the optimum amount of time after an initial meeting before initiating sex. Women often require more time than men to accurately assess the other’s mate value. Qualities that enter into the calculus of a man’s mate value—his attentiveness, status trajectory, dependability, health, sense of humor, existing commitments, family ties, and genetic quality—require more than a glance to accurately evaluate. Physical attractiveness, an important component of mate value for both sexes, can be appraised in milliseconds—but this typically makes up a smaller proportion of a man’s mate value than a woman’

Moreover, sexual mistakes are typically costlier to women than to men. Women risk a poorly timed or unwanted pregnancy, a higher probability of acquiring a sexually transmitted infection, and more damage to their sexual reputation. Yes, sexual double standards still exist, even in the most sexually egalitarian cultures, such as Sweden or Norway.

Sexual conflicts begin when a man and woman first meet on the mating market or online. But they do not end after a relationship is formed. Nor do they end after a romantic breakup.

We must first explain why conflicting optima exist at all within a supremely cooperative species such as our own, in which women and men need each other for successful reproduction.

Men produce millions of sperm, replenishable every hour, that are stripped-down packets of DNA with a tail designed for swimming speed. Women have merely a few hundred viable eggs, large and loaded with nutrients, that they ovulate over their reproductive years and cannot be replenished.

From the moment of conception, when the one tiny sperm joins the nutrient-rich egg, women are already contributing much more than the man.

It is the woman who incubates the fertilized egg within her body. It is the woman who transfers calories from her body through the placenta to the developing embryo. It is the woman who suffers through pregnancy sickness, an adaptation to avoid and expel foods containing toxins and pathogens dangerous to the fetus. It is the woman whose center of gravity is shifted increasingly forward, putting more torque and strain on her spinal column, impairing her mobility and rendering her more vulnerable to falling and injury. It is the woman who bears the burden of nine full months of pregnancy, an astonishingly long investment compared to most mammals. And it is the woman who nourishes the infant first with colostrum, which contains key ingredients that help the newborn develop a strong immune system, and then with breast milk—lactation that continues typically for years after birth—to shift metabolic energy from her body to the child’

But the Tiwi share with most cultures the central notion that women embody the most important resource over which men compete. They share with other cultures that conflicts between men often center on competition for women. They share with other cultures that status is a major means by which men attract or acquire women as mates, and reciprocally, that success in acquiring mates bestows status. They share with many other cultures the stance that sex with another man’s wife is a crime against the husband, and that the guilty mate poacher warrants punishment.

Sexual jealousy is a key cause of conflict within mateships—a universal emotion stoked when there is a major threat to a valued relationship. Importantly, sexual conflicts within relationships influence other forms of social conflict, such as between an interloper and the husband, among women, and among the larger coalitional alliances of men and women. Sexual conflict, in short, permeates many deep strands of human social life.

Genetic evolution is a slow process. Cultural evolution is swift.

The intensity of sexual jealousy and the frequency with which it is experienced are roughly equal in men and women. Neither sex has a monopoly on this powerful emotion. The psychological nature of jealousy, however, differs between women and men.

Although there is considerable overlap, men’s jealousy focuses more heavily on the sexual aspects of their partner’s conduct. It does so for an extremely important functional reason. It evolved to solve the problem of paternity uncertainty. Women are always 100 percent certain that they are the mothers of their offspring. No woman ever wondered, as an infant was emerging from her body, “Is this kid really mine?” Men can never be sure. As people in some cultures say, “Mama’s baby, Papa’s maybe.” It’s an asymmetry that stems directly from an asymmetry of human reproductive biology—fertilization occurs internally within the woman’s body, not the man’s. And unless a woman is under lock and key twenty-four hours a day guarded by a phalanx of eunuchs, another man might have the opportunity to inseminate her.

Sexual jealousy, expressed in ancient and culturally modern forms, motivates men to increase the odds that they are the actual genetic fathers. It also minimizes “wasting” their investment on children sired by rival men—a costly endeavor in reproductive currencies.

Then along came a novel cultural invention that changed everything—reliable hormonal birth control pills, which received FDA approval in 1960. Within a few years, millions of women were taking the pill. In the United States, 98 percent of sexually active women have taken a hormonal contraceptive at some point in their lives, and 62 percent of reproductive-age women are currently on the pill. Comparable figures in Nordic countries such as Denmark, Sweden, and Finland hover in the low 40 percent range.

The pill’s invention and spread had many consequences for human sexuality. It liberated women from unwanted and untimely pregnancies, for example. But ...

Consider this thought experiment. You are interviewing a newlywed man in a study about his sexual attitudes. You explain to him that although sexual jealousy evolved partly to solve the problem of paternity uncertainty, his blushing bride is taking highly effective birth control pills. Moreover, in the unlikely event that she gets pregnant (less than 2 percent chance if used as directed) you can conduct a DNA test to be 100 percent sure the child is your own. Therefore, the main adaptive rationale for the existence of sexual jealousy is entirely absent. Paternity uncertainty is an ancient adaptive problem that is no longer relevant. After you explain this, you ask the man: “Would you be okay with another man having sex with your wife this evening, now that you know that there’s no need for sexual jealousy, as long as there is a guarantee that she won’t leave you?” Would most men be okay with other men having passionate sexual intercourse with their beautiful brides or trying out different sexual positions with them? If this thought experiment doesn’t convince you of the answer, our empirical studies might. When we brought men into the physiological lab and asked them to imagine ...

This example illustrates a few key points. First, cultural inventions such as the birth control pill fundamentally change the ground rules within which human sexuality gets expressed—they alter the cost-benefit calculus of sexual behavior, in this case severing the link between sexual intercourse and conception. Second, some components of our sexual psychology, exquisitely adaptive in the past, may no longer be adaptive in modern cultural contexts. Third, some aspects of our sexua...

Importantly, culture continues to evolve and does so rapidly. We invent cultural products that activate and satisfy our evolved sexual psychology whether or not the adaptations that comprise that psychol...

We tend to think of cultural inventions as more or less unmitigated blessings, and many are. Dishwashers save time wasted on washing. Food-delivery services save time on shopping. Video-streaming services provide immediate access to an array of exciting movies and shows. Modern medicine extends our lives. But just a...

When Rohypnol is secretly slipped into a woman’s drink at a bar, it combines with alcohol to disarm her defenses. It produces partial amnesia. It clouds her memory. It renders her unable to clearly recall the sexual assault, her assailant, or even the events immediately preceding and following the assault.

Whereas men’s leg muscle mass exceeds that of women’s by 50 percent, men have 75 percent more arm muscle mass and exceed women by 90 percent in total upper-body strength.

Our research discovered that most women cultivate backup mates, ranging in number from one to five, who function as “mate insurance.” Women with their own economic resources have greater power to leave bad relationships or trade up to better ones. Women with small children who are economically dependent on their husbands have less choice. This is undoubtedly one reason why divorce rates are twice as high when the woman’s income exceeds the man’s rather than vice versa.

Sexual conflict theory with sexually antagonistic arms races can take us only so far in understanding the war of the sexes. We must explain individual differences—why only some men and some women are especially prone to inflict costs on members of the other sex.

Some scholars argue that all men are potential sexual predators, but science does not bear out this dismal premise. Most men do not “corner” women by the copy machine, surreptitiously “ass-grab” when the opportunity arises, brag about sexual assault as part of “locker-room talk,” or show up to business meetings in bathrobes. Many men would not dream of harming women in these ways, or risk compromising their reputations, their futures, or their moral standards with inappropriate sexual advances, even if they experience sexual attraction and could get away with it. But some men do, and the qualities of this subset of serial harassers and assailants deserve special focus.

Research has hit upon an important discovery: serial harassers score high on the Dark Triad of personality traits—narcissism,...

A hallmark of narcissism is a strong sense of personal entitlement, and this extends to the sexual sphere. Machiavellianism is marked by a social strategy of manipulation and exploitation. High Machs, as they are called, view other humans as mere tools to be used for instrumental aims and discarded. High scorers on psychopathy are deficient in empathy and indifferent to others’ suffering, although they often convey a superficial veneer of charm that fools some women. All three ele...

Can women be sexual predators? Our research on the Dark Triad suggests yes, but in somewhat different ways. Women who score high in Dark Triad traits are more likely to engage in mate poaching, luring men away from existing relationships for sexual encounters. High-scoring women are ...

Each of us is descended from innumerable generations of men who lied, cheated, charmed, bullied, or killed their way to sexual intercourse, and from innumerable generations of women who charmed, seduced, lied, or manipulated their way to extracting economic privileges in return for access to their bodies. —Paul Seabright, The War of the Sexes

CONFLICT ON THE MATING MARKET starts when a woman and a man pursue fundamentally different mating strategies. When a strategy pursued by one interferes with the successful implementation of the strategy pursued by the other, it produces strategic interference. If a woman is seeking a brief fling and the man she meets at a bar is looking for a wife for life, the strategies are inherently in conflict. Their desires cannot be simultaneously satisfied. One is bound to be disappointed.

Strategic interference on the mating market takes many forms. It can occur over differences in perceived mate value, as when a man is attracted to a woman he perceives as an 8 (on a scale of 1 to 10), but she believes he’s not good enough for her. It can occur on a date when one individual pushes for sex sooner or with less emotional connection than the other requires. It can occur when a woman walks down the street and is subjected to unwanted sexual attention such as lewd leering or catcalls. Men who harass women interfere with a cardinal component of their sexual psychology—female choice. And it can occur in any circumstance in which men try to bypass a woman’s freedom to exercise selectivity, be it sexual harassment in the workplace or sexual assault from a stranger.

A key cause of sexual conflict on the mating market is one of the largest psychological sex differences ever document...

Another behavioral marker of the desire for sexual variety is seeking sex outside one’s primary and presumptively monogamous mateship. The famous sexologist Alfred Kinsey found that twice as many men as women had experienced at least one sexual infidelity while married—50 percent versus 26 percent.2 Although women have started to close the gap in recent years, all studies show a sex difference in infidelity rates of at least 10 percent, and most show a larger gap than that. Moreover, men who cheat do so with a larger number of sex partners. Men seeking sex on the side apparently are serial philanderers. Women are choosier even in this domain, typically having a single affair. And of those women, 70 percent cite love or emotional connection as the key reason for the affair, a finding that points less to women’s desire for sexual variety and more to the mate-switching function of infidelity—a topic we take up in Chapter 3. Men’s affairs are more motivated by sex with someone new.

Most women need a bit more time, information, and emotional involvement before consenting to sex with a stranger.

The psychological and behavioral evidence, in short, all points to the same conclusion: that men and women differ profoundly in their desire for sexual variety.

Individuals differ, of course, in the strength of this desire—the distributions overlap, and some women exceed some men, just as they do in weight or height. Individuals also differ in whether this desire is expressed in actual mating behavior, such as casual sex, affairs, or patronizing prostitutes. Many men choose not to act on their desires. Some lead lives of quiet desperation. They suffer longings unfulfilled due to moral, religious, or reputational considerations, or simply because they lack opportunity. “A man is only as faithful as his options,” according to comedian Chris Rock.