The Evolution of Desire

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Origins of Mating Behavior

We have never quite outgrown the idea that somewhere, there are people living in perfect harmony with nature and one another, and that we might do the same were it not for the corrupting influences of Western culture.

—Melvin Konner, Why the Reckless Survive

HUMAN MATING BEHAVIOR delights and amuses us and galvanizes our gossip, but it is also deeply disturbing. Few domains of human activity generate as much discussion, as many laws, or such elaborate rituals in all cultures. Yet the elements of human mating seem to defy understanding. Women and men sometimes find themselves choosing mates who abuse them psychologically and physically. Efforts to attract mates often backfire. Conflicts erupt within couples, producing downward spirals of blame and despair. Despite their best intentions and vows of lifelong love, half of all married couples end up divorcing.

Pain, betrayal, and loss contrast sharply with the usual romantic notions of love. We grow up believing in true love, in finding our “one and only.” We assume that once we do, we will marry in bliss and live happily ever after. But reality rarely coincides with our beliefs. Even a cursory look at the divorce rate, the 30 to 50 percent incidence of extramarital affairs, and the jealous rages that rack so many relationships shatters these illusions.

Discord and dissolution in mating relationships are typically seen as signs of failure. They are regarded as distortions or perversions of the natural state of married life. They are thought to signal personal inadequacy, immaturity, neurosis, failure of will, or simply poor judgment in the choice of a mate. This view is radically wrong. Conflict in mating is the norm and not the exception. It ranges from a man’s anger at a woman who declines his advances to a wife’s frustration with a husband who fails to help in the home. Such a pervasive pattern defies easy explanation. Something deeper, more telling about human nature is involved—something we do not fully understand.

The problem is complicated by the centrality of love in human life. Feelings of love mesmerize us when we experience them and occupy our fantasies when we do not. The anguish of love dominates poetry, music, literature, soap operas, and romance novels more than perhaps any other theme. Contrary to common belief, love is not a recent invention of the Western leisure classes. People in all cultures experience love and have coined specific words for it.¹ Its pervasiveness convinces us that love, with its key components of commitment, tenderness, and passion, is an inevitable part of the human experience, within the grasp of everyone.²

Our failure to understand the real and paradoxical nature of human mating is costly, both scientifically and socially. Scientifically, the dearth of knowledge leaves unanswered some of life’s most puzzling questions, such as why people sacrifice years of their lives to the quest for love and the struggle for relationship. Socially, our ignorance leaves us frustrated and helpless when we are bruised by mating behavior gone awry in the workplace, on the dating scene, and in our home.

We need to reconcile the profound love that humans seek with the conflict that permeates our most cherished relationships. We need to square our dreams with reality. To understand these baffling contradictions, we must gaze back into our evolutionary past—a past that has grooved and scored our minds as much as our bodies, our strategies for mating as much as our strategies for survival.

Evolutionary Roots

More than a century ago, Charles Darwin offered a revolutionary explanation for the mysteries of mating.³ He had become intrigued by the puzzling way that animals had developed characteristics that would appear to hinder their survival. The elaborate plumage, large antlers, and other conspicuous features displayed by many species seemed costly in the currency of survival. He wondered how the brilliant plumage of peacocks could evolve, and become more common, when it poses such an obvious threat to survival, acting as an open lure to predators. Darwin’s answer was that the peacock’s displays evolved because they led to an individual’s reproductive success, providing an advantage in the competition for a desirable mate and continuing that peacock’s genetic line. The evolution of characteristics because of their reproductive benefits, rather than survival benefits, is known as sexual selection.

Sexual selection, according to Darwin, takes two forms. In one form, members of the same sex compete with each other, and the outcome of their contest gives the winner greater sexual access to members of the opposite sex. Two stags locking horns in combat is the prototypical image of this intrasexual competition. The characteristics that lead to success in contests of this kind, such as greater strength, intelligence, or attractiveness to allies, evolve because the victors are able to mate more often and hence pass on more genes. In the other type of sexual selection, members of one sex choose a mate based on their preferences for particular qualities in that mate. These characteristics evolve in the other sex because animals possessing them are chosen more often as mates, and their genes thrive. Animals lacking the desired characteristics are excluded from mating, and their genes perish. Since peahens prefer peacocks with plumage that flashes and glitters, dull-feathered males get left in the evolutionary dust. Peacocks today possess brilliant plumage because over evolutionary history peahens have preferred to mate with dazzling and colorful males.

Darwin’s theory of sexual selection begins to explain mating behavior by identifying two key processes by which evolutionary change can occur: preferences for a mate and competition for a mate. But the theory was vigorously resisted by male scientists for over a century, in part because the active choosing of mates seemed to grant too much power to females, who were thought to remain passive in the mating process. The theory of sexual selection was also resisted by mainstream social scientists because its portrayal of human nature seemed to depend on instinctive behavior, and thus to minimize the uniqueness and flexibility of humans. Culture and consciousness were presumed to free us from evolutionary forces. The breakthrough in applying sexual selection to humans came in the late 1970s and 1980s, in the form of theoretical advances initiated by my colleagues and me in the fields of psychology and anthropology.⁴ We tried to identify underlying psychological mechanisms that were the products of evolution—mechanisms that help to explain both the extraordinary flexibility of human behavior and the active mating strategies pursued by women and men. This new discipline is called evolutionary psychology.

When I began work in the field, however, little was known about actual human mating behavior. There was a frustrating lack of scientific evidence on mating in the broad array of human populations, and practically no documented support for grand evolutionary theorizing. No one knew whether some mating desires are universal, whether certain sex differences are characteristic of all people in all cultures, or whether culture exerts a powerful enough influence to override the evolved preferences that might exist. So I departed from the traditional path of mainstream psychology to explore which characteristics of human mating behavior would follow from evolutionary principles. In the beginning, I simply wanted to verify a few of the most obvious evolutionary predictions about sex differences in mating preferences; for example, whether men desire youth and physical attractiveness in a mate and whether women desire status and economic security. Toward that end, I interviewed and administered questionnaires to 186 married adults and 100 unmarried college students within the United States.

The next step was to verify whether the psychological phenomena uncovered by this study were characteristic of our species. If mating desires and other features of human psychology are products of our evolutionary history, they should be found universally, not just in the United States. So I initiated an international study to explore how mates are selected in other cultures, starting with a few European countries, including Germany and the Netherlands. I soon realized, however, that since European cultures share many features, they do not provide the most rigorous test for the principles of evolutionary psychology. Over a period of five years, I expanded the study to include fifty collaborators from thirty-seven cultures located on six continents and five islands, from Australia to Zambia. Local residents administered the questionnaire about mating desires in their native language. We sampled large cities, such as Rio de Janeiro and São Paulo in Brazil, Shanghai in China, Bangalore and Ahmadabad in India, Jerusalem and Tel Aviv in Israel, and Tehran in Iran. We also sampled rural peoples, including Indians in the state of Gujarat and Zulus in South Africa. We covered the well educated and the poorly educated. We included respondents of every age from fourteen through seventy, as well as places in the entire range of political systems from capitalist to communist and socialist. All major racial groups, religious groups, and ethnic groups were represented. In all, we surveyed 10,047 persons worldwide.

This study, the largest ever undertaken on human mating desires, was merely the beginning. The findings had implications that reached into every sphere of human mating life, from dating to marriage, extramarital affairs, and divorce. They were also relevant to major social issues of the day, such as sexual harassment, domestic abuse, pornography, and patriarchy. To explore as many mating domains as possible, I launched over fifty new studies, involving thousands of individuals. Included in these studies were men and women searching for a mate in singles bars and on college campuses, dating couples at various stages of commitment, newlywed couples in the first five years of marriage, and couples who ended up divorced.

The findings from all of these studies caused controversy and confusion among my colleagues, because in many respects they contradicted conventional thinking. They forced a radical shift from the standard view of men’s and women’s sexual psychology. One of my aims in this book is to formulate from these diverse findings a unified theory of human mating, based not on romantic notions or outdated scientific theories but on current scientific evidence. Much of what I discovered about human mating is not nice. In the ruthless pursuit of sexual goals, for example, men and women derogate their rivals, deceive members of the opposite sex, and even subvert their own mates. These discoveries are disturbing to me; I would prefer that the competitive, conflictual, and manipulative aspects of human mating did not exist. But a scientist cannot wish away unpleasant findings. Ultimately, the disturbing side of human mating must be confronted if its harsh consequences are ever to be ameliorated.

Sexual Strategies

Strategies are methods for accomplishing goals, the means for solving problems. It may seem odd to view human mating, romance, sex, and love as inherently strategic. But we never choose mates at random. We do not attract mates indiscriminately. We do not derogate our competitors out of boredom. Our mating is strategic, and our strategies are designed to solve particular problems for successful mating. Understanding how people solve those problems requires an analysis of sexual strategies. Strategies are essential for survival on the mating battlefield.

Adaptations are evolved solutions to the problems posed by survival and reproduction. Over millions of years of evolution, natural selection has produced in us hunger mechanisms to solve the problem of providing nutrients to the organism; taste buds that are sensitive to fat and sugar to solve the problem of what to put into our mouths (nuts and berries, but not dirt or gravel); sweat glands and shivering mechanisms to solve the problems of extreme hot and cold; emotions such as fear and rage that motivate flight and fight to combat predators or aggressive competitors; and a complex immune system to combat diseases and parasites. These adaptations are human solutions to the problems of existence posed by the hostile forces of nature—they are our survival strategies. Those who failed to develop appropriate characteristics failed to survive.

Correspondingly, sexual strategies are adaptive solutions to mating problems. Those in our evolutionary past who failed to mate successfully failed to become our ancestors. All of us descend from a long and unbroken line of ancestors who competed successfully for desirable mates, attracted mates who were reproductively valuable, retained mates long enough to reproduce, fended off interested rivals, and solved the problems that could have impeded reproductive success. We carry in us the sexual legacy of those success stories.

Each sexual strategy is tailored to a specific adaptive problem, such as identifying a desirable mate or besting competitors in attracting a mate. Underlying each sexual strategy are psychological mechanisms, such as preferences for a particular mate, feelings of love, desire for sex, or jealousy. Each psychological mechanism is sensitive to information or cues from the external world, such as physical features, signs of sexual interest, or hints of potential infidelity. Our psychological mechanisms are also sensitive to information about ourselves, such as our ability to attract a mate who has a certain degree of desirability. The goal of this book is to peel back the layers of adaptive problems that men and women have faced in the course of mating and uncover the complex sexual strategies they have evolved for solving them.

Although the term sexual strategies is a useful metaphor for thinking about solutions to mating problems, it is misleading in the sense of connoting conscious intent. Sexual strategies do not require conscious planning or awareness. Our sweat glands are “strategies” for accomplishing the goal of thermal regulation, but they require neither conscious planning nor awareness of the goal. Indeed, just as a piano player’s sudden awareness of her hands may impede performance, most human sexual strategies are best carried out without the awareness of the actor.

Selecting a Mate

Nowhere do people have an equal desire for all members of the opposite sex. Everywhere some potential mates are preferred, others shunned. Our sexual desires have come into being in the same way as have other kinds of desires. Consider the survival problem of what food to eat. Humans are faced with a bewildering array of potential objects to ingest—berries, fruit, nuts, meat, dirt, gravel, poisonous plants, twigs, and feces. If we had no taste preferences and ingested objects from our environment at random, some people, by chance alone, would consume ripe fruit, fresh nuts, and other objects that provide caloric and nutritive sustenance. Others, also by chance alone, would eat rancid meat, rotten fruit, and toxins. Earlier humans who preferred nutritious objects survived.

Our actual food preferences bear out this evolutionary process. We show great fondness for substances rich in fat, sugar, protein, and salt and an aversion to substances that are bitter, sour, and toxic.⁵ These food preferences solve a basic problem of survival. We carry them with us today precisely because they solved critical adaptive problems for our ancestors.

Our desires in a mate serve analogous adaptive purposes, but their functions do not center simply on survival. Imagine living as our ancestors did long ago—struggling to keep warm by the fire; hunting meat for our kin; gathering nuts, berries, and herbs; and avoiding dangerous animals and hostile humans. If we were to select a mate who failed to deliver the resources promised, who had affairs, who was lazy, who lacked hunting skills, or who heaped physical abuse on us, our survival would be tenuous, our reproduction at risk. In contrast, a mate who provided abundant resources, who protected us and our children, and who devoted time, energy, and effort to our family would be a great asset. As a result of the powerful survival and reproductive advantages that were reaped by those of our ancestors who chose a mate wisely, clear desires in a mate evolved. As descendants of those people, we carry their desires with us today.

Many other species have evolved mate preferences. The African village weaverbird provides a vivid illustration.⁶ When the male weaverbird spots a female in the vicinity, he displays his recently built nest by suspending himself upside down from the bottom and vigorously flapping his wings. If the male passes this test, the female approaches the nest, enters it, and examines the nest materials, poking and pulling them for as long as ten minutes. As she makes her inspection, the male sings to her from nearby. At any point in this sequence she may decide that the nest does not meet her standards and depart to inspect another male’s nest. A male whose nest is rejected by several females will often break it down and start over. By exerting a preference for males who can build a superior nest, the female weaverbird solves the problems of protecting and provisioning her future chicks. Her preferences have evolved because they bestowed a reproductive advantage over other weaverbirds who had no preferences and who mated with any males who happened along.

Women, like weaverbirds, prefer men with desirable “nests.” Consider one of the problems that women in evolutionary history had to face: selecting a man who would be willing to commit to a long-term relationship. A woman in our evolutionary past who chose to mate with a man who was flighty, impulsive, philandering, or unable to sustain relationships found herself raising her children alone, without benefit of the resources, aid, and protection that another man might have offered. A woman who preferred to mate with a reliable man who was willing to commit to her was more likely to have children who survived and thrived. Over thousands of generations, a preference for men who showed signs of being willing and able to commit to them evolved in women, just as preferences for mates with adequate nests evolved in weaverbirds. This preference solved key reproductive problems, just as food preferences solved key survival problems.

People do not always desire the commitment required of long-term mating. Men and women sometimes deliberately seek a short-term fling, a temporary liaison, or a brief affair. And when they do, their preferences shift, sometimes dramatically. One of the crucial decisions for humans in selecting a mate is whether they are seeking a short-term mate or a long-term partner. The sexual strategies pursued hinge on this decision. This book documents the universal preferences that men and women display for particular characteristics in a mate, reveals the evolutionary logic behind the different desires of each sex, and explores the changes that occur when people shift their goal from casual sex to a committed relationship.

Attracting a Mate

People who possess desirable characteristics are in great demand. Appreciating their traits is not enough for successful mating, just as spying a ripe berry bush down a steep ravine is not enough for successful eating. The next step in mating is to compete successfully for a desirable mate.

Among the elephant seals on the coast of California, males during the mating season use their sharp tusks to best rival males in head-to-head combat.⁷ Often their contests and bellowing continue day and night. The losers he scarred and injured on the beach, exhausted victims of this brutal competition. But the winner’s job is not yet over. He must roam the perimeter of his harem, which contains a dozen or more females. This dominant male must hold his place in life’s reproductive cycle by herding stray females back into the harem and repelling other males who attempt to sneak copulations.

Over many generations, male elephant seals who are stronger, larger, and more cunning have succeeded in getting a mate. The larger, more aggressive males control the sexual access to females and so pass on to their sons the genes conferring these qualities. Indeed, males now weigh roughly 4,000 pounds, or four times the weight of females, who appear to human observers to risk getting crushed during copulation.

Female elephant seals prefer to mate with the victors and thus pass on the genes conferring this preference to their daughters. But by choosing the larger, stronger winners, they also determine the genes for size and fighting abilities that will live on in their sons. The smaller, weaker, and more timid males fail to mate entirely. They become evolutionary dead ends. Because only 5 percent of the males monopolize 85 percent of the females, selection pressures remain intense even today.

Male elephant seals must fight not just to best other males but also to be chosen by females. A female emits loud bellowing sounds when a smaller male tries to mate with her. The alerted dominant male comes bounding toward them, rears his head in threat, and exposes a massive chest. This gesture is usually enough to send the smaller male scurrying for cover. Female preferences are one key to establishing competition among the males. If females did not mind mating with smaller, weaker males, then they would not alert the dominant male, and there would be less intense selection pressure for size and strength. Female preferences, in short, determine many of the ground rules of the male contests.

People are not like elephant seals in most of these mating behaviors. For example, whereas only 5 percent of the male elephant seals do 85 percent of the mating, more than 90 percent of men are able at some point in their lives to find a mate.⁸ Male elephant seals strive to monopolize harems of females, and the winners remain victorious for only a season or two, whereas many humans form enduring unions that last for years and decades. But men and male elephant seals share a key characteristic: both must compete to attract females. Males who fail to attract females risk being shut out of mating.

Throughout the animal world, males typically compete more fiercely than females for mates, and in many species males are certainly more ostentatious and strident in their competition. But competition among females is also intense in many species. Among patas monkeys and gelada baboons, females harass copulating pairs in order to interfere with the mating success of rival females. Among wild rhesus monkeys, females use aggression to interrupt sexual contact between other females and males, occasionally winning the male consort for herself. And among savanna baboons, female competition over mates serves not merely to secure sexual access but also to develop long-term social relationships that provide physical protection.⁹

Competition among women, though typically less florid and violent than competition among men, pervades human mating systems. The writer H. L. Mencken noted: “When women kiss, it always reminds one of prize fighters shaking hands.” This book shows how members of each sex compete with each other for access to members of the opposite sex. The tactics they use to compete are often dictated by the preferences of the opposite sex. Those who do not have what the other sex wants risk remaining on the sidelines in the dance of mating.

Keeping a Mate

Keeping a mate is another important adaptive problem; mates may continue to be desirable to rivals, who may poach, thereby undoing all the effort devoted to attracting, courting, and committing to the mate. Furthermore, one mate may defect because of the failure of the other to fulfill his or her needs and wants or upon the arrival of someone fresher, more compelling, or more beautiful. Mates, once gained, must be retained.

Consider the Plecia nearctica, an insect known as the lovebug. Male lovebugs swarm during the early morning and hover a foot or two off the ground, waiting for the chance to mate with a female.¹⁰ Female lovebugs do not swarm or hover. Instead, they emerge in the morning from the vegetation and enter the swarm of males. Sometimes a female is captured by a male before she can take flight. Males often wrestle with other males, and as many as ten males may cluster around a single female.

The successful male departs from the swarm with his mate, and the couple glides to the ground to copulate. Perhaps because other males continue to attempt to mate with her, the male retains his copulatory embrace for as long as three full days—hence the nickname “lovebug.” The prolonged copulation itself functions as a way of guarding the mate. By remaining attached to the female until she is ready to deposit her eggs, the male lovebug prevents other males from fertilizing her eggs. In reproductive currency, his ability to compete with other males and attract a female would be for naught if he failed to solve the problem of retaining his mate.

Different species solve this problem by different means. Humans do not engage in continuous copulatory embraces for days, but the problem of holding on to a mate is confronted by everyone who seeks a long-term relationship. In our evolutionary past, men who were indifferent to the sexual infidelities of their mates risked compromising their paternity. They risked investing time, energy, and effort in children who were not their own. Ancestral women, in contrast, did not risk the loss of parenthood if their mates had affairs, because maternity has always been 100 percent certain. But a woman with a philandering husband risked losing his resources, his commitment, and his investment in her children. One psychological strategy that evolved to combat infidelity was jealousy. Ancestral people who became enraged at signs of their mate’s potential defection and who acted to prevent it had a selective advantage over those who were not jealous. People who failed to prevent infidelity in a mate had less reproductive success.¹¹

The emotion of jealousy motivates various kinds of action in overt response to a threat to the relationship. Sexual jealousy, for example, may produce either of two radically different actions, vigilance or violence. In one case, a jealous man might follow his wife when she goes out, call her unexpectedly to see whether she is where she said she would be, keep an eye on her at a party, or read her mail. These actions represent vigilance. In the other case, a man might threaten a rival whom he spotted with his wife, beat the rival with his fists, get his friends to beat up the rival, or throw a brick through the rival’s window. These actions represent violence. Both courses of action, vigilance and violence, are different manifestations of the same psychological strategy of jealousy. They represent alternative ways of solving the problem of the defection of a mate.

Jealousy is not a rigid, invariant instinct that drives robotlike, mechanical action. It is highly sensitive to context and environment. Many other behavioral options are available to serve the strategy of jealousy, giving humans a flexibility in tailoring their responses to the subtle nuances of a situation. This book documents the range of actions that are triggered by jealousy and the contexts in which they occur.

Replacing a Mate