Man and Woman, Part VI: The Main Event

sure, it feels good--but why? what exactly happens to each of them when a man and a woman have sex?

Four hundred years ago, Columbus claimed he discovered the clitoris. Realdus Columbus, that is. Nearly 50 years later, in 1642, came another astonishing revelation. One Giovanni Sinibaldi, the writer of the first standard work on sexuality, announced that he had identified the seat of male pleasure, "a structure which so greatly enhances female enjoyment"--the foreskin.

We seem to have come a long way since then. We no longer fear eternal damnation if we go to bed with each other. We no longer use silk handkerchiefs for contraception. And we're no longer inclined to deal with sex, as Thomas Carlyle's wife did, by closing our eyes and thinking of England. Instead, we have drawers full of pills, vibrators and condoms. We frolic happily together. Like butterfly hunters, we collect orgasms. And sex, unglued from reproduction, has become the national sport. All that only 40 years after America was pronounced one of the three societies on earth in which sex was taboo. Not bad, eh?

Not bad, no--but not entirely good, either. For the enforced democratization of our sexual revolution has taken some of the subtlety out of our rituals of flirtation and courtship. All in all, the pressures in our society appear to have conspired to make the act of sex an end in itself. It has become so important that it's unimportant. And that, ironically, as we'll see, probably works to the short-term advantage of men. But it also works to the long-term disadvantage of all of us. For the essence of any democracy is that we are all essentially alike. And the essence of this sexual democracy of ours is that we are all sexually alike--apart from a few minor differences in the plumbing we carry around with us.

That, as we've been saying throughout this series, is simply not true of men and women in general. And it's no more true of the way we approach and experience sex. Life isn't as simple as Masters and Johnson's proclamation that the female orgasm is the same as the male orgasm--and that an orgasm is an orgasm is an orgasm, however got. It's a great deal more complex and potentially rewarding than that. As men and women, we have been a long time coming to this place. We've brought to it different sexual baggage--different bodies, different needs, different drives, different mechanisms and different experiences of pleasure--and in that difference lies our togetherness.

Science has had very little to say about any of this since the days of Columbus and Sinibaldi--very little, at least, that wasn't both harebrained and murderously sexist. And so far in this century, science has had to take a back seat to the largely intuitive findings of psychology and psychiatry, which have persistently emphasized how alike we are, how alike we ought to be. (Not, perhaps, a good thing, since psychiatrists, according to a 1979 poll, have the worst sex lives of those in any branch of the medical profession, for all their fine democratic notions.) Now, though, science is beginning to have something new and very important to say. Along scattered fronts, including that of research psychology, it's beginning to suggest that a new age in our sexual relations may be upon us. It may turn out to be a time in which, because we'll understand more, we'll learn to give more. Our sex could become less confusing and less anxiety-ridden, more hopeful and more loving. We may stop having to limp off to the helping professions with our sexual problems, because the answer is within us, between us, in the differences that make us one.

On the other hand, this new age could take another shape. For science now has tools that allow it to dig deep into the human brain and into the chemistry by which it controls our sex and reproduction. And although its work will virtually guarantee us wonderful things--new treatments for impotence and infertility, nasal sprays for contraception and simple saliva-test kits for timing ovulation--it could also guarantee us something considerably less wonderful: a time when all the strange, satisfying, messy humanity of sex was stripped from it. Reproduction is one area in which we're already beginning to lose control--"test tube" babies, artificial insemination and genetic engineering are the writing on the wall. And the special, private individuality of our sex lives may be next. For as science understands more about the mechanisms of sex, it will become easier for it to develop drugs to alter and govern them. Work is already going forward on chemicals that affect sexual appetite, ejaculation and orgasm in humans as well as in laboratory animals. And one can easily envision a time when erections become repeatable and orgasms, after a visit to the pharmacist, become available on demand. You may even achieve sexual pleasure at the popping of a pill.

A senior scientist at the U. S. National Institutes of Health said not long ago that, yes, "the brave new world is something that's subtly and slowly emerging." And if you say that's all right with you--that sex with two or sex with love is a problem anyway--then consider for a moment the sweet give-and-take that you'll be missing. Watch with us, through our editorial one-way mirror, as a couple plays out that timeless ritual of courtship and seduction. As all of us who've been there know, it's a process that all by itself feels better than any ten other things we could name--combined. But this time, you're going to see what goes on beneath the skin. And by the morning after, you'll have an appreciation for the mystery of sex that you never would have gotten if this had been your evening.

As we join our unsuspecting couple, the party is in progress. Lights are low; the ice cubes rattle in the glasses. Watch carefully.

He feels her presence--a stir in the room, a smell, a tone of voice. He turns, and suddenly his muscles stiffen. His face is flushed; his heart beats faster. His pupils dilate as he watches her from across the room.

She notices his reaction, and her sympathetic nervous system responds--as if to danger. Her pulse quickens. Her palms tingle and become warm. A blush washes across her face. Glancing downward to hide the moment, she is half-conscious of a prickling in her scalp--and of her nipples pressing against the stretched silk of her dress. For a second, she feels as if she's been attacked, and her breathing becomes quicker, shallower. Dimly irritated, she draws distractedly on a cigarette. But when she finally looks up to meet his stare, her pupils, too, are subtly larger than they were a few moments before.

Now our strangers in the night are well into the song. Intensely conscious of each other, they continue to play their drama from across the room, a drama of glances, gestures and tones of voice--of coded information given and received. The result is a flurry of small-print news about suitability, status and availability, each item buried in the gathering bustle of the party in progress. He shows his leanness, his success with others, his clothes, his tan, the readiness of his smile. She offers him a softness, a seriousness and an adroit, flirtatious coolness with the man she's talking to. As she moves, she runs her unringed fingers down the long cascade of her throat. A glimpse of breast is proffered, then deferred. The senses of both become heightened. And the drama moves into a new phase.

Wherever they go now, moving still in circles that never quite touch, she hears his voice arguing, laughing, teasing. And he follows her constantly with his eyes. Finally, she stands apart from the others for a moment, fishing with her tongue for a piece of ice in her glass. And their eyes lock as she looks up again. For a second, she feels panicked, naked. Then he is at her side.

The restaurant is well chosen, un-crowded, candlelit. A piano plays softly, sealing off the diners from one another. Our couple sit in a well of separateness, testing each other, gently probing in a process as old as mankind. She watches his quiet authority with the waiters, the way he eats and moves and sips his wine. All the while, she measures his real interest in her, sitting the clues of words and eyes and mouth and tongue. He takes in the healthy glow of her skin, the whiteness of her teeth, and he leans forward to touch her hand where it lies, curved, around the stem of her wineglass. As the evening deepens, their talk becomes more muted and more charged. Amid this spell, an unvoiced decision has to be made.

To that decision, to their new closeness, comes the hormonal status of their bodies. As they talk, seemingly idly, it is the balance of estrogen and progesterone in her that helps produce her glow, her self-assurance and her readiness. And it is the level of testosterone in him that induces his confidence and the sort of canny, disguised aggression he's showing in his pursuit of her. All those hormones act upon the brain. They interact there with chemically controlled systems governing memory, learning, past associations and expectation of pleasure and reward. From the beginning of their drama, the brains of both have been regulating and following the intricate patterns of their courtship--one step forward, one step back. Sensory receptors have recorded the looks, the movements, the words, the food, the wine, the touch. And at a high level of the brain, all that information has been integrated with experience and anticipation. From there, the good news has traveled to self-reinforcing brain circuits controlling pleasure and reward, and messenger chemicals--in this case, dopamine and noradrenaline--have carried it to brain structures responsible for emotion and motivation. All those interlocking systems, influenced by hormonal messages from the secreting glands of the body, are constantly communicating with one another, totting up the pluses and minuses of the flirtation and initiating behavior that will carry it forward. And each can still respond--to too much food and drink, too bold a move, a false word, a bad impression--by influencing the other systems to turn off, tune down, withdraw.

Our couple's evening, in other words, is first and always a matter of the right chemistry. And at the heart of it, as they drink their coffee, still wondering, waiting for the outcome, is a bundle of tissue at the base of each of their brains called the hypothalamus. The keeper of the border between brain and body, the hypothalamus receives from and transmits to virtually every area of their brains. At the same time, it is in constant two-way communication with the outlands of their bodies.

Right now, it is monitoring their blood pressure, their temperature and their breathing rate. It is inspecting their appetite--and it is integrating, expressing and pushing forward their basic drive toward sex. Neither one of our subjects is aware of its influence, of course. But it was the hypothalamus, acting through the long-distance messengers of the pituitary gland just beneath it, that ordered up from testis and ovary the levels of hormones that got this started in the first place. And it is the hypothalamus that's now bidding up from their adrenal glands the cortisone and the adrenaline responsible for the heightened charge and warmth of their encounter. It makes her exquisitely sensitive to the hand that reaches out to touch her face, to the leg gently leaning against hers. And it makes him feel, by calling up more testosterone, a new tightness in his loins.

Nothing is said. They walk through the night, he with his arm around her, just touching the curve of her breast--imagining it, imagining her, without clothes. Her nerve impulses race back and upward, to spine, to brain, to hypothalamus. And once more, her nipples press against the material of her dress. A rise in the amount of circulating estrogen (continued on page 190) Man and Woman (continued from page 166) makes her moist. She moves closer to him and they stop to kiss, each exploring the biology of the other's mouth. They stand still for a moment, understanding through smell and the sensations of breath and heartbeat that they're now part of a common arousal. Somewhere in the wash of hormones and the complex brain talk of the messenger chemicals, a decision has been made. She shivers, though it is not cold, and the tiny hairs along her forearms become erect.

Inside the apartment, he slowly undresses her--whispering, kissing, reassuring. His excitement feeds on hers as he sees her swelling lips, the rush of blood to her areolae, the blush that spreads across her body. The reservoirs in the erectile tissue of his penis fill with blood and trap more and more of the blood that the brain orders up in compensation. Fully erect now, he quickly removes his own clothes. He teases at her breasts with his mouth and runs his hands down her flanks, reaching, little by little, toward the center of her. He fingers her clitoris, which also engorges with blood to become erect. He explores the wetness being spilled out into her vagina from glands lining the entrance and the walls of her vaginal canal.

At that point, you can bet our hero and heroine aren't thinking about what a tough day they had at the office. In fact, control of the reasoning forebrain has been removed, and both are now creatures of the lower brain and of the autonomic nervous system. The parasympathetic nervous system is causing hardness and moistness--the drop of moisture at the end of his penis; the discharge of hormones from glands in armpits, breasts and pubic skin. And the sympathetic nervous system is washing the muscles of both partners with adrenaline. Their hearts are beating faster, their breathing has become heavy, their muscles are taut. Meanwhile, their adrenal glands are pumping out testosterone in a mix of other hormones, making her clitoris more sensitive and giving him an extra urgency centered on his penis and on the reflex are that now governs his erection from nerve centers at the base of his spine.

Automatic nervous impulses rush to their pelvic muscles. Their excitement mounts. She pulls him closer and he enters her. Now both are working, matching the rhythm of their movements, thrusting, lifting and pushing. And slowly. the sympathetic nervous tension builds in each of them to a higher and higher pitch. Pressure changes in her womb. Blood vessels are increasingly constricted. Glands are burdened. Muscles are drum tight.

Then, suddenly, release. The right brain takes command, and the parasympathetic nervous system suddenly erupts into action to take over their bodies. The messenger chemical acetylcholine takes the place of adrenaline. And where there was tension, there is now an explosion into calmness. The muscles of his penis contract involuntarily, sending a stream of sperm arcing into her, Nerve impulses race toward his brain. If our hero is the noisy type, he probably cries something like "Yeees!" in a great exhilaration of air. At the same time, contractions begin to ripple along the walls of our heroine's vagina as he shudders within her. They reach upward toward her womb and outward to her pulsing, disgorging clitoris. A new hormone, oxytocin, is released from her pituitary. Her skin darkens. And "Yes!" she cries, too, as she plummets back to rest.

They're quiet for a moment as hearts slow, blood pressure drops and bodies return to normal. He falls asleep quickly; but she lies awake as substances within the ejaculate now inside her cause the contractions in her womb and vagina to continue, only more slowly. As he begins to breathe more deeply, she continues to feel vaguely aroused. How good was it? she wonders. Could there have been more?

•

That, ladies and gentlemen, is sex. More or less. Give or take. And it's obviously an immensely complicated business. It involves the state of two bodies, attraction, arousal and what Masters and Johnson have called E.P.O.R. (excitement, plateau, orgasm and resolution). For our hero and heroine, it has involved literally millions of variables. For them, it has depended on chance. It has been carried through a delicate dance of moves and countermoves. And at any point, anything--a distraction, a dropped cue, a twinge of guilt--could have nipped their affair in the bud. It has also been dependent not only on them but on the culture that surrounds them. If one or the other of them, for example, had sported saucer-shaped lips, a large nose ring or whole-body basket-weave tattooing (signs of considerable beauty elsewhere), the evening would never have begun. And if he or she had started poking the other in the eye or biting at the other's eyebrow (all the rage in other places). it would never have continued.

Their attitudes toward sex, in other words, and much of what they do during it, are based on local custom. They have to do with religion and law and upbringing and experience. They're learned. Fellatio, cunnilingus and all the other variations on the theme that we have left out may be fun, but they, too, are learned (usually only in societies that are maritally stable--which, by that definition, ours is). The point is, an enormous amount of our sexual jousting is purely cultural. And if we're going to be able to say anything fundamental about it, we're going to have to strip away culture and aim straight at the biological heart of the scene between him and her. We're going to have to look at the biological inheritance they received from all the sexually successful parents who preceded them--the programs that evolved to bring a man and a woman together and to make them attractive to each other. Those programs aren't rigid; they don't dictate behavior. But they predispose.

"What we have to do is look across human cultures and see if they fit a central hypothesis," says Donald Symons, associate professor of anthropology at the University of California at Santa Barbara and author of The Evolution of Human Sexuality. "The hypothesis is this: Since human females, like those of most species, make a relatively large investment in the production and survival of each offspring--and males can sometimes get away with a relatively small one--they'll approach sex and reproduction in rather different ways from males. During our evolutionary history, the sexual desires and dispositions that promoted reproductive success for one sex probably spelled reproductive disaster for the other sex. Therefore, assuming that our brains, like the rest of our bodies, were designed by natural selection, men and women today ought to differ in their sexual psychologies. Women should be more choosy and more hesitant, because they're more at risk from the consequences of a bad choice. And men should be less discriminating, more aggressive and have a greater taste for a variety of partners--because they're less at risk. That is, in fact, what we find.

"Furthermore, individual males and females aren't equally valuable as mates. So mechanisms ought to have developed that enabled them to detect and be attracted to the most reproductively valuable members of the opposite sex, the ones most useful to their genes. Males would look for health, aptness for (continued on page 240) Man and Woman (continued from page 190) motherhood and youth--it's in their interests to tie up a woman's whole reproductive career. And females would look for something else: health, yes, but also strength and long-term resources: whatever was necessary for the survival of their genes.

"The first part of the hypothesis is supported," Symons continues, "by studies done all over the world on people of different ages, classes and sexual preferences. Men tend to be the sex-seeking gender. And women--if you read The Hite Report, for example--are simply not as interested in casual sex, even though they sometimes believe they should be and would be happier if they were. What they require from sex in general is some sort of emotional involvement.

"The second part of the hypothesis holds up equally well. Let's start with men. Men in all cultures prize health and cleanliness--good skin, good teeth. They set great store by physical attractiveness, and this attractiveness is always associated with youth. Why? Because youth is when a woman is most valuable, reproductively speaking. She can have and care for only a relatively small number of children during her lifetime, and so the earlier a man acquires her, the better. Detecting and being attracted by signs of female youth is part of the male's genetic program.

"Youth, though, isn't a criterion that women apply to men, because a man's reproductive value can actually increase with age. And his value is less dependent on his physical appearance. It has more to do with reliability, status, prowess, skills and the ability to command and accumulate wealth. During our evolution, then, women who attended to those signs of value would have had the reproductive edge over those who paid court primarily to youth and physical attractiveness. And there would have been selective pressures to ensure that such a tendency survived in women today. In fact, that's what we see. While men are sexually drawn to younger women, women routinely marry older men and not necessarily Adonises.

"The upshot of all this," says Symons, "is that men and women have different sexual psychologies because they have different reproductive strategies. And those psychological differences underlie all heterosexual transactions. Women control what men have always needed--the ability to carry and reproduce their genes for them. And so a man tends to pursue sex aggressively--it's a trivial expenditure of energy with a potentially big payoff. For a woman, though, sex is something else. Women, after all, have always had one of their few, expensive eggs and their bodies on the line. And so sex for a woman remains a valuable service--a service that has to be carefully traded."

Back to the restaurant. Now we can see what's been going on in the attraction between our hero and heroine. Originally, of course, she noticed him because he so obviously had eyes for her. Then she liked what she had noticed. And then, almost unconsciously, she began to absorb all the clues in him that suggested status and resources (and potentially valuable genes): his clothes, his tan, his ease with others, his leanness. All those things carry shifting social meanings. A tan, for example, once meant outside work: now it means money for vacations. Thinness once meant the poverty of undernourishment: now thin is in--it's the poor, by and large, who are fat.

Our hero, meanwhile, went through a similar process. Status--clothing and so on--was clearly important to him. But his appraisal was mainly physical. As he watched her, what he checked out were her age, her skin, her hips and her breasts--all signs of her fitness for motherhood. And since he thought her beautiful, one can assume something else--that in appearance, she was somewhere close to the population average. Standards of beauty vary from society to society, but they always represent an averaging of what the society looks like. There are genetic reasons for this--reasons that are part of his sex drive. For the average is the mainstream of the genetic pool in any society. Other things being equal, the average is a better bet, genetically speaking, than something on the fringes.

All that has been considered. And now, as they order their food and eat their dinner, they're at a second stage, at which she holds all the cards. For if they're to have sex, she has to say yes. She has to be convinced that there's no danger in their intimacy, that he is gentle and reliable. To find out whether or not that is true, she requires courtship. She needs evidence. She needs, in evolutionary terms, to make sure that the man will stay around long enough to provide resources for her and her offspring. For a woman, that decision is crucial. And in order to deal with it, women have developed mechanisms that make them much more discriminating, guarded and conservative in their sex drive than men. She sits opposite him, in other words, possessed of a different evolutionary inheritance. She almost certainly has an enhanced ability to read his character from gesture, posture and tone of voice (see Man and Woman, Part Three: The Sex Life of the Brain, March). Her senses are more finely tuned and her brain is organized in such a way that she has readier access to the emotional context of what she's experiencing. She's quick, therefore, to react to the slightest sign of danger, and she responds sexually not to instant cues but to atmosphere, to all those collective cues that signal warmth, intimacy and absence of danger--attentiveness, a soothing voice, whispering, touching, quiet music.

Something of who she is can be seen in the huge industry of romantic magazines and fictions aimed at her. She requires a certain ambience for sex. When it comes to representations of sex in books and pictures, she responds most to those in which the relationships are believable. And as for her own sex life, her sexual willingness requires a psychological go-ahead. John Wincze of Brown University Medical School and Patricia Schreiner-Engel of Mount Sinai School of Medicine have found--in separate studies--that a woman often shows physiological, vaginal arousal when watching sex films or listening to erotic tapes. But she doesn't, by any means, always feel aroused at the same time--as a man always does. There's a potential gap between the responses of her body and the conscious part of her brain.

She's protected by nature, then, from making the wrong snap decision about him. And she's been provided by evolution with a further protective mechanism, the effects of which are all around us. She is, quite simply, less visually arousable than he is, because it wouldn't serve her reproductive purposes to be turned on by the sight of just any old male body.

He, of course, isn't so restrained. He has different evolutionary fish to fry, so he devours her with his eyes, undresses her in his mind. It's no wonder that a successful men's-magazine industry has been built up around his visually oriented male libido--but not around hers. No women's magazines can find a market solely on the basis of male nudes--they sell, rather, to male homosexuals.

What does all this add up to in the attraction between him and her? Well, if he comes on too strong, he may not make out--there's more ultimate compatibility between two people when the man isn't too pushy. What he has to remember is that her approach to sex has less to do with what the poet W. H. Auden once called "the intolerable neural itch." That doesn't mean she can't be instantly attracted to a man, and it doesn't mean she can't pursue large numbers of sexual partners. But it does mean that the attraction she feels is unlikely to be a purely physical one. And it means that, in being promiscuous, she may have some difficulty overriding the evolutionary programs within her. For she'll be doing something that in evolution worked not to her advantage but to man's. And no matter how hard she tries, she simply isn't a man. She hasn't inherited the male pattern of sexual behavior, and, like it or not, a number of studies have shown that she is less likely to experience orgasm during a one-night stand than she is in the context of a stable long-term relationship.

•

If you don't buy the idea of different evolutionary programs operating within our hero and our heroine as they sit in the restaurant appraising each other, then consider this: Ten or 15 years ago--or however many years ago they began to go through puberty--they wouldn't have given two cents for the pleasure of each other's company. Then, two or so years later, their parents probably said: "Oh, God, he's/she's girl/boy crazy."

By that time, the sex hormones had done their work. She'd become locked into her menstrual cycle, had developed breasts, had grown her particular pattern of pubic hair, had expanded her pelvis and put on weight at her hips--so gaining a low center of gravity and the beginnings of the hip-swiveling walk of a mature woman. He, meanwhile, had developed a deep voice, new muscles and larger bones, had grown facial hair and a larger penis and had set up continuous sperm production. Now they were ready to meet, having become attractive to each other by becoming different from each other, and all according to the time-table of an evolutionary program that continues in the restaurant and for the rest of their reproductive lives. The overseer of the program is, in both cases, the hypothalamus. But its most important field representative is different in each of them. In him, it's testosterone: in her, it's estrogen.

The hypothalamus is primed in the womb to produce those extraordinary events of puberty by starting up major production of the sex hormones. From that point on, it controls the sexual and reproductive behavior of us all. It is, as we've said, a sort of command center between the brain and the body, constantly monitoring the state of both. When necessary, it calls up long-distance messengers from the pituitary to influence the working of the various organs of the body. In matters sexual, it does that by sending the pituitary a hormone called L.H.R.H. (luteinizing hormone-releasing hormone). L.H.R.H. causes the pituitary to release into the blood stream two additional hormones. F.S.H. (follicle-stimulating hormone) and L.H. (luteinizing hormone), which then home in on particular targets. In men, F.S.H. starts up sperm production. And L.H. tells the testes to produce testosterone, which then travels to various tissues in the body and back to the brain.

All three hormones are more or less continuously produced in men, whose testosterone levels bounce up and down like a yo-yo several times a day. So it's very hard to tell how this system affects their sex lives--except, perhaps, by helping to maintain a consistent sex drive.

In women, it's a different story. For the three hormones are intimately involved with both the rigorous timing of events during the menstrual cycle and the ebb and flow of the sexual appetite. The way the hormones do that is complicated, but F.S.H. is basically responsible for the production of estrogen and L.H. for progesterone. And the rise and fall of those two hormones during the 28-day cycle of ovulation and menstruation are accompanied by subtle changes in sexual readiness and desire. The sex drive in women, in other words, is under particular hormonal constraints--part of their ancient evolutionary program.

The science of all this is still in its infancy, L.H.R.H., for example, was discovered and synthesized only 11 years ago, and it took hundreds of thousands of dollars and millions of animal brains to do the job. Science is also strictly limited, still, in the number of ways it can look at human sex. It can show men and women erotic flicks while their penises and vaginas are decked out with strain gauges and measurers of bloodvessel constriction. It can measure the level of their hormones. It can wire the heads of men and women making love or masturbating. It can look at men and women who suffer from sexual disorders and dysfunctions because their supply of estrogen and testosterone or their hypothalamus or their pituitary or their adrenal glands have gone on the fritz. And it can then try out various drugs on them--including the hormones and chemical messengers it's found to be involved in the sex lives of animals.

All this is still very crude. But despite its crudeness, science is nevertheless, little by little, beginning to tell us a new story. It's beginning to tell us that deep within the chemistry of him and her--though there are mechanisms that dictate different sexual strategies--there are also ancient mechanisms yoking them together in the courtship dance.

Back again to the restaurant. One of the things we can imagine about our heroine's presence there is that at some point, she has painted her lips, put on eye make-up and dabbed a drop or two of perfume behind her ears and between her breasts. That's something women have been doing on such occasions for thousands of years. Those are ancient sexual signals.

More important, for our purposes, is the fact that they actually mimic hormonal events that take place in a woman's body. Lip paint duplicates the reddening of the lips during sexual arousal. Eye make-up reflects the old knowledge that our pupils dilate when we see something attractive and that we become more attractive as a result. (Belladonna, which used to be part of a woman's cosmetic repertoire, produces the pupil-dilating effect directly.) And perfume--well, the odd thing about perfumes in history is that their most important ingredients have been secretions from the sexual-scent glands of animals: musk deer. European beaver and civet cat. We have scent glands, too--in armpit, breast and pubic skin. So what we've been doing all these years is borrowing the powerful sexual smells of other species to overpower the grace notes of our own hormonal communications system.

She does all this leisurely dabbing and daubing because she's feeling good about herself, confident, subtly sexy. The reason, let us assume, is that she's somewhere near the point of ovulation, in the middle of her cycle. Estrogen is, roughly, the hormone of the first part of the cycle. It prepares her body for the egg--and for sex. It builds up the lining of her womb and vagina and it makes her feel and look good. It subtly raises her temperature and gives her body tone and color. She glows. Then, around the time of ovulation, there's a rise in her progesterone level, the first impact of which is to make her receptive. And it's accompanied--some scientists believe--by a peak in adrenal-produced testosterone, which makes her clitoris more sensitive and increases her sex drive. At no other time in her cycle do those three hormones coincide in her in the same way. Only at ovulation do they conspire to give her that unique readiness for sex as well as a heightening of three of her senses--sight, taste and smell.

There's no doubt that this is a holdover from a very old mechanism that makes most female primates receptive--in heat--at only one point in their cycle. But it continues to be part of our heroine's evolutionary program, and it continues, mysteriously, to affect the way our hero behaves toward her. Somehow or other, he can pick up on what's going on in her body. In general, men seem to want sex less during the second part of a woman's cycle, after her egg has come and gone. And although you may say it has to do with external signs, the change in her attractiveness, and so on, that still doesn't explain some even odder things that go on between men and women. There's evidence that simply dating a man--or working around male hormones--alters a woman's cycle and makes it more regular. There's evidence, too, that when a man and a woman live together, their base levels of testosterone rise and fall in unison: the temperature changes characteristic of her cycle are echoed in him.

How is such hidden information communicated? Probably by smell. And here we come to the mysterious heart of the chemical communication between him and her. Smell messages travel to the hypothalamus and to other areas of the brain known to be involved in sex. And it's possible that he and she still have inherited ability to appraise each other sexually by smell. At puberty, their apocrine glands--in armpit, breast and pubic skin--started to put out substances that are by-products of their fluctuating sex hormones. And at least one of those substances has been shown to alter mood and attraction in men and women--even when they aren't aware of smelling it.

It may be, then, as they sit in the restaurant, that our couple are communicating in a language they don't know they know, a language that affects how attracted they are to each other. He, way below the surface of consciousness, is vetting her hormonal state, seeing how close she is to producing his own reproductive goal, her egg. And to all her other collected information, she's adding news about the level of his testosterone. Testosterone levels are markers in animals of their relative position in the pecking order. And in human males, they rise both after any success and when sex is anticipated. So they're a pretty good measure, it she can read them, of the promise or potential value of his genes--and of his interest in her.

•

And so, as they say, to bed. To the roller coaster of Masters and Johnson's E.P.O.R. What can science tell us about him and her at this stage? Well, until recently, the only sort of science that had anything to say was social science. And, according to Kinsey, social science, after years of patient work, can tell us that she has an 89 percent chance of having more than three minutes of foreplay and a 22 percent chance of having more than 20 minutes. (The average in this society, according to two further studies, is between 12 and a half and 15 minutes.) It can tell us that their coitus will last an average of two minutes (Kinsey) or ten minutes (Morton Hunt). And it can tell us that she'll take about eight minutes to reach orgasm as against two minutes for him.

It can also tell us that he is unlikely to be very skilled at pleasing her. American men are by no means as good at that as the men of Mangaia, in central Polynesia. There, at the age of 13 or 14, boys start their sexual education under the tutelage of older men and then of older women. They learn the techniques for pleasuring a woman. And, according to D. S. Marshall, in the process, they acquire a knowledge of female anatomy superior to the average g.p.'s. The result? A happily assumed responsibility for multiple female orgasms that lasts through their reproductive lives.

The difference between a Mangaian man and our American men is cultural, of course. Skills are learned and a man can always improve his performance. Again, though, we have to look below the level of such cultural differences if we're to find anything fundamental to say about the sexual possibilities that exist between two hypothalamuses, two pituitaries, two lots of 16-square-foot skin covering and two sets of genitals. As we've seen, hard science can tell us something about the nervous apparatus, the hormones, the glands and the chemicals that are involved, willy-nilly, in their bedroom encounter. But it still can't answer two important questions that are basic to the difference between them. Why does one gaggle of human tissue--his--reach its peak of sexual activity about the age of 18 while the other gaggle of human tissue--hers--reaches its peak much later, around 28? And why is his orgasm universal--a foregone conclusion--while hers is various and sporadic?

Back again to evolution--to tie together in one bundle our couple's different evolutionary strategies and the sexual mechanisms that still mediate them. First the facts. A man's sexual activity rises steeply immediately after puberty, reaching its height before he turns 20. From then on, it steadily declines toward zero--which is reached well after the age of 70. A woman, meanwhile, increases her sexual activity very slowly after puberty. She doesn't reach her peak until about the age of 28. She remains at the same level of activity until around 45, when a slow decline sets in.

That is fairly easy to understand in the case of the eager male. Life was almost certainly nasty, brutish and short for males in the hunter-gatherer societies, and there was obviously a genetic advantage in reaching a sexual peak. The earlier a male started, the better chance his genes had of surviving. And if his genes survived, then his male descendants would also be early starters, as we men are today. The male decline is simply a by-product of the early peak. It's slow and very gradual. And it's simply the result of generations of men's tending to have children earlier rather than later.

The pattern in women is more difficult to read, but, again, it has to do with selection and the survival of their genes. A woman doesn't come into full reproductive maturity until the years between 19 and 24. One element in this is the fact that her pregnancy between puberty and the late teens is associated with all sorts of problems: her children have more difficulty surviving. A second element is that a woman needs help if she's to guarantee her genes' survival, so it's simply in her interests to wait until the right man comes along. Nature now comes into the picture, favoring those women who have the tendency to hold back until the ties of a lasting affection are established. Only then is the peak of sexual activity reached.

"Then why," you're probably asking, "aren't 28-year-old women getting it on with 18-year-old men?" For all the old protective reasons we've given. Eighteen-year-old men are notoriously unreliable. They have little to offer in the way of resources. They're aggressive: and, equally to the point, they know very little about the complicated give-and-take of sex. If human sex were simply a branch of athletics, then, of course, 18-year-old men and 28-year-old women would be constantly cavorting. But sex isn't athletics. Contraception or no, it's about reproduction, and the considerable pleasures it offers are, in evolutionary terms, the glue that binds two humans together for the joint project of reproduction (see Part Two: The Sexual Deal: A Story of Civilization, February).

For that, a woman needs intimacy, trust and consideration--precisely what a skilled older man can offer. Learning is, indeed, a crucial part of sex. Because of it, an older man can more readily understand her need for a psychological commitment--he has one of his own to give. Because of it, he knows about courtship--the foreplay before the foreplay in bed. And because of it, too, once they're there, he knows how to help produce in her the ultimate learning experience, the icing on the reproductive cake: the female orgasm.

"Orgasm," says Symons, "is apparently not a common phenomenon among other female primates. And even among humans, it's by no means universal. Some societies don't even have a word for it. They don't know it exists. Even in our own society, between five and ten percent of women never experience it: another 30 or 40 percent experience it only intermittently. It's not tied in any obvious way to reproduction, as the male orgasm is. What's so interesting is that the intense pleasure of orgasm occurs precisely when ejaculation in the male occurs. The pleasure of orgasm is the motivating force in the male: in other words, to get to the point of this crucial reproductive event. Now, there is no comparable crucial reproductive event for the female. She is the receiver. So there is no comparable reinforcing mechanism. In the female, then, orgasm is a potential--one that requires male skill and interest to be expressed. In the few societies in which all females are said to experience orgasm, there is either prolonged foreplay, in which the clitoris plays a big part, or consciously prolonged intercourse.

"Why, if it's only a potential, is it there? The answer," Symons suggests, "is that though it was favored by natural selection in males and not in females, it nevertheless survives in females in the same way the nipples survive in males--even though males can't normally produce milk. Ejaculation, from a vestigial prostate, can also occur in some women when they orgasm. And I think that's the same sort of thing.

"The female orgasm has, I know, received a lot of press, usually linked to the idea of female insatiability. And I think it's thrown us off track. First, I don't believe that women are insatiable--it's not what one finds cross-culturally, and it's hard to imagine how female insatiability could have been favored by natural selection. And, second, orgasm is simply not the be-all and end-all of sex for most women. If you read The Hite Report, for example, an overwhelming number of women talked about affection, intimacy and love as their primary reasons for liking intercourse--not orgasm. And most women considered the moment of penetration to be their favorite physical sensation."

What Symons implies is that in our culture, women are being trapped into pursuing a will-o'-the-wisp--being persuaded that what's important to men is of the utmost importance to them as well. That doesn't mean that men shouldn't improve their performance and become more skillful and helpful lovers than they are. But the female orgasm, remember, is most likely to be experienced in the context of a stable, loving relationship. And if a woman pursues it through variety, then she may be using an essentially male strategy--playing into male hands and probably undercutting her own satisfaction.

The point is that she is under evolutionary constraints. And just as her vagina evolved to accommodate his penis, and vice versa, so her constraints evolved to accommodate the danger that he represents. If a push-button orgasm had served her reproductive purposes in the past, then it would be with her today. Put another way, her clitoris would be in her vagina. But it isn't. No, a woman is different from a man--differently programed, differently aroused, differently wired for pleasure.

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For thousands of years, human beings have known instinctively about the chemistry of sex. They've used those animal sex scents in their perfumes and they've also compulsively eaten everything that reminds them of the sex organs (bananas, avocados and oysters) as well as the sex organs of animals themselves (pig vulvas, sheep penises and bull balls). What they were after was some essence of sex to improve their performance.

They were on the right track, because food does, indeed, contain substances from which the hormones and the chemical messengers involved in sex are made. Dopamine, for example, is manufactured from tyrosine, found in large quantities in cereal. It has a stimulating effect on men--though not, as far as can be seen, on women. Serotonin, another messenger, is manufactured from tryptophan in food high in carbohydrates, and it seems to excite her but depress him. Acetylcholine--the raw material for which is found in eggs--has an extraordinary effect, according to some preliminary work done with animals at Tulane University in New Orleans, on the mating behavior of both sexes.

The truth is, you'd probably have to eat an enormous amount of cereal or starch or eggs to get the effect you're after. But there is a simpler and more direct way of taking those and other substances--via a hypodermic or a pill. And that, inevitably, is where science is headed. For the moment, it's turning its findings to such important human uses as the treatment of impotence and infertility and the control of conception. But what science is discovering in the process are things that, in our pill-oriented society, could easily be put to different purposes. These are early days yet. But L.H.R.H., which has a dampening effect on the male libido, has been shown, in unpublished studies, to have the opposite effect on women: a treated woman, according to one researcher, "was really jumping around in bed." And as for male impotence--well, a Canadian group is having "very promising results" with experiments involving a synthetic derivative of the bark of an African tree, the yohimbé. There's a whole pharmacopoeia of other potential candidates with even stranger names--some derived from the human body and brain, some not. Parachlorophenylalanine, given with or without testosterone, has aphrodisiac effects: the body seems to give up before the sex drive does. And three other substances do something of the same sort. Naloxone, according to work done at Vassar and elsewhere, turns sleepy male animals into Don Juans. Alpha M.S.H. vastly increases sexual behavior in both males and females. And ACTH1-10 produces "dreamlike erections, copulatory movements and ejaculations."

Scientists have known for some time that it a rat is allowed to stimulate certain parts of its brain electrically, it will continue to press the lever to do that until it dies of malnutrition and exhaustion. Researchers have also found that if you stimulate the hypothalamus of a male rat, it will have erections at the rate of about 24 an hour--and will ejaculate about 15 times an hour.

It's the chemistry of both phenomena that science is now, little by little, working out. And it's time to ask: Do we want this chemistry for ourselves--for people who aren't afflicted by sexual disorders? Should we manipulate, for our own pleasure, the sexual behavior that our evolution has prescribed for us?

These are serious questions, because they involve the two ages that we talked about at the beginning of this report. One age leads us back to nature--to the place in nature, the constraints of nature that science has recently understood us to have inherited. The other age leads forward to a technology of pleasure and to the ultimate democracy of men and women. The question is, in such a democracy, would our hero and heroine find themselves marooned in their own selfishness?

"A distraction, a dropped cue, a twinge of guilt could have nipped their affair in the bud."

"'Detecting and being attracted by signs of female youth is part of the male's genetic program."'