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The Biology of Attraction

Much of courtship and mating is choreographed by nature. In fact, nature designed men and women to work together.

In an apocryphal story, a colleague once turned to the great British geneticist J.B.S. Haldane, and said, "Tell me, Mr. Haldane, knowing what you do about nature, what can you tell me about God?" Haldane replied, "He has an inordinate fondness for beetles." Indeed, the world contains over 300,000 species of beetles. I would add that "God" loves the human mating game, for no other aspect of our behavior is so complex, so subtle, or so pervasive. And although these sexual strategies differ from one individual to the next, the essential choreography of human courtship, love, and marriage has myriad designs that seem etched into the human psyche, the product of time, selection, and evolution. They begin the moment men and women get within courting range—with the way we flirt.

In describing these strategies, I make no effort to be "politically correct." Nature designed men and women to work together. But I cannot pretend that they are alike. They are not. And I have given evolutionary and biological explanations for their differences where I find them appropriate.


Women from places as different as the jungles of Amazonia, the salons of Paris, and the highlands of New Guinea apparently flirt with the same sequence of expressions.

First the woman smiles at her admirer and lifts her eyebrows in a swift, jerky motion as she opens her eyes wide to gaze at him. Then she drops her eyelids, tilts her head down and to the side, and looks away. Frequently she also covers her face with her hands, giggling nervously as she retreats behind her palms. This sequential flirting gesture is so distinctive that [German ethologist Irenaus] Eibl-Eibesfeldt was convinced it is innate, a human female courtship ploy that evolved eons ago to signal sexual interest.

Men also employ courting tactics similar to those seen in other species. Have you ever walked into the boss's office and seen him leaning back in his chair, hands clasped behind his head, elbows high, and chest thrust out? Perhaps he has come from behind his desk, walked up to you, smiled, arched his back, and thrust his upper body in your direction? If so, watch out. He may be subconsciously announcing his dominance over you. If you are a woman, he may be courting you instead.

The "chest thrust" is part of a basic postural message used across the animal kingdom—"standing tall." Dominant creatures puff up. Codfish bulge their heads and thrust our their pelvic fins. Snakes, frogs, and toads inflate their bodies. Antelope and chameleons turn broadside to emphasize their bulk. Mule deer look askance to show their antlers. Cats bristle. Pigeons swell. Lobsters raise themselves onto the tips of their walking legs and extend their open claws. Gorillas pound their chests. Men just thrust out their chests.

"Copulatory" Gaze

The gaze is probably the most striking human courting ploy. Eye language. In Western cultures, where eye contact between the sexes is permitted, men and women often stare intently at potential mates for about two to three seconds during which their pupils may dilate—a sign of extreme interest. Then the starer drops his or her eyelids and looks away.

No wonder the custom of the veil has been adopted in so many cultures. Eye contact seems to have an immediate effect. The gaze triggers a primitive part of the human brain, calling forth one of two basic emotions—approach or retreat. You cannot ignore the eyes of another fixed on you; you must respond. You may smile and start conversation. You may look away and edge toward the door. But first you will probably tug at an earlobe, adjust your sweater, yawn, fidget with your eyeglasses, or perform some other meaningless movement—a "displacement gesture"—to alleviate anxiety while you make up your mind how to acknowledge this invitation, whether to flee the premises or stay and play the courting game.

Baboon Love

Baboons gaze at each other during courtship too. These animals may have branched off of our human evolutionary tree more than 19 million years ago, yet this similarity in wooing persists. As anthropologist Barbara Smuts had said of a budding baboon courtship on the Eburru cliffs of Kenya, "It looked like watching two novices in a singles bar."

The affair began one evening when a female baboon, Thalia, turned and caught a young male, Alex staring at her. They were about 15 feet apart. He glanced away immediately. So she stared at him—until he turned to look at her. Then she intently fiddled with her toes. On it went. Each time she stared at him, he looked away; each time he stared at her, she groomed her feet. Finally Alex caught Thalia gazing at him—the "return gaze."

Immediately he flattened his ears against his head, narrowed his eyelids, and began to smack his lips, the height of friendliness in baboon society. Thalia froze. Then, for a long moment, she looked him in the eye. Only after this extended eye contact had occurred did Alex approach her, at which point Thalia began to groom him—the beginning of a friendship and sexual liaison that was still going strong six years later, when Smuts returned to Kenya to study baboon friendships.

At The Bar

Could these courting cues be part of a larger human mating dance?

According to David Givens, an anthropologist, and Timothy Perper, a biologist, who spent several hundred hours in American cocktail lounges watching men and women flirt, American singles-bar courtship has several stages, each with distinctive escalation points. I shall divide them into five. The first is the "attention getting" phase. Young men and women do this somewhat differently. As soon as they enter the bar, both males and females typically establish a territory—a seat, a place to lean, a position near the jukebox or dance floor. Once settled, they begin to attract attention to themselves.

Tactics vary. Men tend to pitch and roll their shoulders, stretch, exaggerate their body movements. Instead of using the wrist to stir a drink, men often employ the entire arm, as if stirring mud. The normally smooth motion necessary to light a cigarette becomes a whole-body gesture, ending with an elaborate shaking from the elbow to extinguish the match.

Then there is the swagger with which young men often move to and fro. Male baboons on the grasslands of East Africa also swagger when they foresee a potential sexual encounter. A male gorilla walks back and forth stiffly as he watches a female out of the corner of his eye. The parading gait is known to primatologists as bird-dogging. Males of many species also preen. Human males pat their hair, adjust their clothes, tug their chins, or perform other self-clasping or grooming movements that diffuse nervous energy and keep the body moving.

Young women begin the attention-getting phase with many of the same maneuvers that men use—smiling, gazing, shifting, swaying, preening, stretching, moving in their territory to draw attention to themselves. Often they incorporate a battery of feminine moves as well. They twist their curls, tilt their heads, look up coyly, giggle, raise their brows, flick their tongues, lick their upper lips, blush, and hide their faces in order to signal, "I am here."

Some women also have a characteristic walk when courting; they arch their backs, thrust out their bosoms, sway their hips, and strut. No wonder many women wear high-heeled shoes. This bizarre Western custom, invented by Catherine de Medici in the 1500s, unnaturally arches the back, tilts the buttocks, and thrusts the chest out into a female come-hither pose. The clomping noise of their spiky heels draws attention too.

Keeping Time

Body synchrony is the final and most intriguing component of the pickup. As potential lovers become comfortable, they pivot or swivel until their shoulders become aligned, their bodies face-to-face. This rotation toward each other may start before they begin to talk or hours into conversation, but after a while the man and woman begin to move in tandem. Only briefly at first. When he crosses his legs, she crosses hers; as he leans left, she leans left; when he smoothes his hair, she smoothes hers. They move in perfect rhythm as they gaze deeply into each other's eyes.

Called interactional synchrony, this human mirroring begins in infancy. By the second day of life, a newborn has begun to synchronize its body movements with the rhythmic patterns of the human voice. And it is now well established that people in many other cultures get into rhythm when they feel comfortable together. Our need to keep each other's time reflects a rhythmic mimicry common to many animals. Chimps sometimes sway from side to side as they stare into one another's eyes just prior to copulation. Cats circle. Red deer prance. Howler monkeys court with rhythmic tongue movements. Stickleback fish do a zigzag jig. From bears to beetles, courting couples perform rhythmic rituals to express their amorous intentions.

Wooing Messages

Human courtship has other similarities to courtship in "lower" animals. Normally people woo each other slowly. Caution during courtship is also characteristic of spiders. The male wolf spider, for example, must enter the long, darker entrance of a female's compound in order to court and copulate. This he does slowly. If he is overeager, she devours him.

Men and women who are too aggressive at the beginning of the courting process also suffer unpleasant consequences. If you come too close, touch too soon, or talk too much, you will probably be repelled. Like wooing among wolf spiders, baboons, and other creatures, the human pickup runs on message. At every juncture in the ritual each partner must respond correctly, otherwise the courtship fails.

The Dinner Date

Probably no ritual is more common to Western would-be lovers than the "dinner date." If the man is courting, he pays—and a woman instinctively knows her partner is wooing her. In fact, there is no more widespread courtship ploy than offering food in hopes of gaining sexual favors. Around the world men give women presents prior to lovemaking. A fish, a piece of meat, sweets, and beer are among the delicacies men have invented as offerings.

This ploy is not exclusive to men. Black-tipped hang flies often catch aphids, daddy longlegs, or houseflies on the forest floor. When a male has felled a particularly juicy prey, he exudes secretions from an abdominal scent gland that catch the breeze, announcing a successful hunting expedition. Often a passing female hang fly stops to enjoy the meal—but not without copulating while she eats.

"Courtship feeding," as this custom is called, probably predates the dinosaurs, because it has an important reproductive function. By providing food to females, males show their abilities as hunters, providers, worthy procreative partners.

Odor Lures

Every person smells slightly different; we all have a personal "odor print" as distinctive as our voice, our hands, our intellect. As newborn infants we can recognize our mother by her smell. Both men and women have "apocrine glands in their armpits, around their nipples, and in the groin that become active at puberty. These scent boxes differ from "eccrine" glands, which cover much of the body and produce an odorless liquid, because their exudate, in combination with bacteria on the skin, produce the acrid, gamy smell of perspiration.

Today in parts of Greece and the Balkans, some men carry their handkerchiefs in their armpits during festivals and offer these odoriferous tokens to the women they invite to dance: they swear by the results.

But could a man's smell actually trigger infatuation in a woman? This possible link between male essence and female reproductive health may provide a clue to attraction. Women perceive odors better than men do. They are a hundred times more sensitive to Exaltolide, a compound much like men's sexual musk; they can smell a mild sweat from about three feet away; and at midcycle, during ovulation, women can smell men's musk even more strongly. Perhaps ovulating women become more susceptible to infatuation when they can smell male essence and are unconsciously drawn toward it to maintain menstrual cycling.

A woman's or a man's smell can release a host of memories too. So the right human smell at the right moment could touch off vivid pleasant memories and possibly ignite that first, stunning moment of romantic adoration.

But Americans, the Japanese, and many other people find odors offensive; for most of them the smell of perspiration is more likely to repel than to attract. Some scientists think the Japanese are unduly disturbed by body odors because of their long tradition of arranged marriages: men and women were forced into close contact with partners they found unappealing. Why Americans are phobic about natural body smells, I do not know. Perhaps our advertisers have swayed us in order to sell their deodorizing products.

Love Maps

A more important mechanism by which human beings become captivated by "him" or "her" may be what sexologist John Money called your love map. Long before you fixate on Ray as opposed to Bill, Sue instead of Ceciley, you have developed a mental map, a template replete with brain circuitry that determines what arouses you sexually, what drives you to fall in love with one person rather than another.

These love maps vary from one individual to the next. Some people get turned on by a business suit or a doctor's uniform, by big breasts, small feet, or a vivacious laugh. But averageness still wins. In one study, psychologists selected 32 faces of American Caucasian women and, using computers, averaged all of their features. Then they showed these images to college peers. Of 94 photographs of real female faces, only four were rated more appealing than these fabrications.

As you would guess, the world does not share the sexual ideals of Caucasian students from Wyoming. Despite wildly dissimilar standards of beauty and sex appeal, however, there are a few widely shared opinions about what incites romantic passion. Men and women around the world are attracted to those with good complexions. Everywhere people are drawn to partners whom they regard as clean. And men in most places generally prefer plump, wide-hipped women to slim ones. Looks count.

So does money. From rural Zulus to urban Brazilians, men are attracted to young, good-looking, spunky women, while women are drawn to men with property or money. Americans are no exception.

These male/female appetites are probably innate. it is to a males' genetic advantage to fall in love with a women who will produce viable offspring; it is to a woman's biological advantage to become captivated by a man who can help support her young. As Montaigne, the 16th-century French essayist, summed it up, "We do not marry for ourselves, whatever we say; we marry just as much or more for our posterity."

Love At First Sight

Could this human ability to adore another within moments of meeting come out of nature? I think it does. In fact, love at first sight may have a critical adaptive function among animals. During the mating season a female squirrel, for example, needs to breed. It is not to her advantage to copulate with a porcupine. But if she sees a healthy squirrel, she should waste no time. She should size him up. And if he looks suitable, she should grab her chance to copulate. Perhaps love at first sight is no more than an inborn tendency in many creatures that evolved to spur the mating process. Then among our human ancestors what had been animal attraction evolved into the human sensation of infatuation at a glance.

Infatuation Fades

Alas, infatuation fades. As Emerson put it, "Love is strongest in pursuit, friendship in possession." At some point, that old black magic wanes. Yet there does seem to be a general length to this condition. Psychologist Dorothy Tennov measured the duration of romantic love, from the moment infatuation hit to when a "feeling of neutrality" for one's love object began. She concluded, "The most frequent interval, as well as the average, is between approximately 18 months and three years" John Money agrees, proposing that once you begin to see your sweetheart regularly the passion lasts two to three years.

Psychiatrist Michael Liebowitz suspected that the end of infatuation is also grounded in brain physiology. He theorized that the brain cannot eternally maintain the revved-up site of romantic bliss. As he summed it up, "If you want a situation where you and your long-term partner can still get very excited about each other, you will have to work on it, because in some ways you are bucking a biological tide."

Harem Building

Only 16 percent of the 853 cultures on record actually prescribe monogyny, in which a man is permitted only one wife at a time. Western cultures are among them. We are in the minority, however. A whopping 84 percent of all human societies permit a man to take more than one wife at once—polygyny.

Men seek polygyny to spread their genes, while women join harems to acquire resources and ensure the survival of their young. If you ask a man why he wants a second bride, he might say he is attracted to her wit, her business acumen, her vivacious spirit, or splendid thighs. If you ask a women why she is willing to "share" a man, she might tell you that she loves the way he looks or laughs or takes her to fancy vacation spots.

But no matter what reasons people offer, polygyny enables men to have more children; under the right conditions women also reap reproductive benefits. So long ago ancestral men who sought polygyny and ancestral women who acquiesced to harem life disproportionately survived.

Man Is Monogamous

Because of the genetic advantages of polygyny for men and because so many societies permit polygyny, many anthropologists think that harem building is a badge of the human animal. But in the vast majority of societies where polygyny is permitted, only about five to 10 percent of men actually have several wives simultaneously. Although polygyny is widely discussed, it is much less practiced.

Whereas gorillas, horses, and animals of many other species always form harems, among human beings polygyny and polyandry seem to be optional opportunistic exceptions; monogamy is the rule. Human beings almost never have to be cajoled into pairing. Instead, we do this naturally. We flirt. We feel infatuation. We fall in love. We marry. And the vast majority of us marry only one person at a time.

Pair-bonding is a trademark of the human animal.

Unfaithfully Yours

Although we flirt, fall in love, and marry, human beings also tend to be sexually unfaithful to a spouse. Americans are no exception. Despite our attitude that philandering is immoral, regardless of our sense of guilt when we engage in trysts, in spite of the risks to family, friends, and livelihood that adultery entails, we indulge in extramarital affairs with avid regularity.

A survey of 106,000 readers of Cosmopolitan magazine in the early 1980s indicated that 54 percent of the married women had participated in at least one affair, and a poll of 7,239 men reported that 72 percent of those married over two years had been adulterous.

Why? From a Darwinian perspective, it is easy to explain. If a man has two children by one woman, he has, genetically speaking, "reproduced" himself. But if he also engages in dalliances with more women and, by chance, sires two more young, he doubles his contribution to the next generation. Those men who seek variety also tend to have more children. These young survive and pass to subsequent generations whatever it is in the male genetic makeup that seeks "fresh features," as Byron said of men's need for sexual novelty.

Unlike a man, a woman cannot breed every time she copulates. In fact, anthropologist Donald Symons has argued that, because the number of children a woman can bear is limited, women are biologically less motivated to seek fresh features.

Sexual Variety

Are women really less interested in sexual variety? My own modest proposal is that during our long evolutionary history most males pursued trysts to spread their genes, while females evolved two alternative strategies to acquire resources: some women elected to be faithful to a single man in order to reap a lot of benefits from him; others engaged in clandestine sex with many men to acquire resources from each. This scenario roughly coincides with common beliefs: man, the natural playboy; women, madonna or whore.

In a study by Donald Symons and Bruce Ellis, for example, 415 college students were asked whether they would have sex with an anonymous student of the opposite sex. In this imaginary scenario, participants were told that all risk of pregnancy, discovery, and disease was absent. The results were those you would expect. Males were consistently more likely to say yes, leading these researchers once again to conclude that men are more interested in sexual variety than women are.

But here's the glitch. This study takes into consideration the primary genetic motive for male philandering (to fertilize young women). But not the primary motive for female philandering—the acquisition of resources.

There is no evidence whatsoever that women are sexually shy or that they shun clandestine sexual adventures. Instead, both men and women seem to exhibit a mixed reproductive strategy: monogamy and adultery are our fare.


We all have our share of troubles. But probably one of the hardest things we do is leave a spouse. From the tundras of Siberia to the jungles of Amazonia, people accept divorce as regrettable—although sometimes necessary. They have specific social or legal procedures for divorce. And they do divorce. Moreover, unlike many Westerners, traditional peoples do not make divorce a moral issue. The Mongols of Siberia sum up a common worldwide attitude, "If two individuals cannot get along harmoniously together, they had better live apart."

Why do people divorce? Bitter quarrels, insensitive remarks, lack of humor, watching too much television, inability to listen, drunkenness, sexual rejection—the reasons men or women give for why they leave a marriage are as varied as their motives for having wedded in the first place.

Overt adultery heads the list. Sterility and barrenness come next. Cruelty, particularly by the husband, ranks third among worldwide reasons for divorce. I am not surprised that adultery and infertility are paramount. Darwin theorized that people marry primarily to breed.

The Four-Year Itch

Hoping to get some insight into the nature of divorce, I turned to the demographic yearbooks of the United Nations. Divorce generally occurs early in marriage—peaking in or around the fourth year after wedding—followed by a gradual decline in divorce as more years of marriage go by. The American divorce peak hovers somewhat below the common four-year peak. Purely as a guess, I would say that this may have something to do with American attitudes toward marriage itself. We tend not to marry for economic, political, or family reasons. Instead, as anthropologist Paul Bohannen once said, "Americans marry to enhance their inner, largely secret selves."

I find this remark fascinating—and correct. We marry for love and to accentuate, balance out, or mask parts of our private selves. This is why you sometimes see a reserved accountant married to a blond bombshell or a scientist married to a poet. Perhaps it is no coincidence that the American divorce peak corresponds perfectly with the normal duration of infatuation—two to three years. If partners are not satisfied with the match, they bail out soon after the infatuation wears off. So there are exceptions to the four-year itch.

Divorce Is For The Young

Another pattern to emerge from the United Nations data regards "divorce with dependent children." Among the hundreds of millions of people recorded in 45 societies between 1950 and 1989, 39 percent of all divorces occurred among couples with no dependent children, 26 percent among those with one dependent child, 19 percent among couples with two, 7 percent among those with three children, 3 percent among couples with four young, and couples with five or more dependent young rarely split. Hence, it appears that the more children a couple bear, the less likely they are to divorce.

This pattern is less conclusively demonstrated by the U.N. data than the first two. Yet it is strongly suggested and it makes genetic sense. From a Darwinian perspective, couples with no children should break up; both individuals will mate again and probably go on to bear young—ensuring their genetic futures. As couples bear more children they become less economically able to abandon their growing family. And it is genetically logical that they remain together to raise their flock.

Planned Obsolescence Of The Pair Bond

Marriage clearly shows several general patterns of decay. Divorce counts peak among couples married about four years. And the longer a couple remain together, the older the partners get, and probably the more offspring they produce, the less likely spouses are to leave each other.

This is not to say that everybody fits this mold. But Shakespeare did. Etched in Shakespeare's marriage and in all these other divorces recorded from around the world is a blue print, a primitive design. The human animal seems built to court, to fall in love, and to marry one person at a time; then, at the height of our reproductive years, often with single child, we divorce; then, a few years later, we remarry once again.

Adapted from Anatomy of Love; The Natural History of Monogamy, Adultery, and Divorce, by Helen E. Fisher. Copyright C 1992 by Helen E. Fisher. Reprinted by arrangement with W. W. Norton & Co., Inc.