by Chip Walter
Osculation (the scientific term for kissing) is not the reason why we developed all of these nerves and muscles. They originally evolved for eating, and the forces of natural selection have refined them to sense flavors and textures and tastes that can make the difference between a nice snack or an ugly, poisonous death. Some scientists wonder if this might explain why we are the only mammals with red, outwardly turned lips. But others, like Desmond Morris, theorize that just as the red and blue faces of male mandrills are facial imitations of the sexual messages their colorful rumps send, our red, pouting lips recapitulate a woman’s genital labia. Like sexual labia, after all, our lips (women’s more than men’s because women’s are fleshier) become redder and more swollen when we are sexually aroused and more blood flows their way.4
This swelling is itself arousing, which explains the wealth of longstanding cultural evidence that men find it attractive, and women often do what they can to enhance it. Egyptian ladies painted their lips a reddish purple with a plant dye called fucus-algin.5 And seventeenth-century European women rouged their lips enough that Thomas Hall, an English pastor, felt compelled to write that those who did were brazenly trying to “kindle a fire and flame of lust in the hearts of those who cast their eyes upon them.”6 Today lips continue to be enhanced, and at a record pace. Lipstick is a $1.5 billion business, and among the more popular current cosmetic procedures is a silicone injection designed to make every pair of lips appear as though they belong to Angelina Jolie. Some psychologists even believe that pouting and lip biting are forms of body language that developed to puff lips up, all in the primal interest of getting the two sexes together to make more versions of ourselves.
However our lips came to have their unique shape and special sensory capabilities, in kissing they found new purpose. We use them to send messages far more dramatic than any words they can form, and nourish hungers deeper than any food mouths consume. As actress Ingrid Bergman once observed, “A kiss is a lovely trick designed by nature to stop speech when words become superfluous.” A “secret told to the mouth instead of to the ear” is the way Edmond Rostand put it.
If we look at it this way, kissing is another human variation on the thing we do better than any other species: communicate. Like laughter and crying, it reaches deep into our past to tie old parts of our nature up with new ones and create behavior that only we are capable of. When we kiss, our history and evolution—all of the wheels and gears and chemistry that make us go—are plastered all over the whole tender, tempestuous, and splendidly human act.
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Kissing is not a universal human behavior. About 90 percent of us do it. But that means some 650 million of us don’t, more than the populations of every country on the planet except for China and India.
Why this is the case is hard to fathom. It is such a sumptuous, luscious invention, you would think it is as deeply spun into our DNA as breathing and walking. But it is a cultural, not a genetic innovation, which is to say we are not born kissers. We have had to learn it.
Back at the turn of the twentieth century, for example, Danish philologist Kristoffer Nyrop found that members of certain Finnish tribes bathed together completely nude, but considered kissing indecent. In Mongolia, some fathers still do not kiss their sons. Instead they smell their heads. An “Eskimo kiss” involves rubbing noses, not touching lips. Neither Polynesians nor Maoris prefer to show affection by kissing. In 1897 the French anthropologist Paul d’Enjoy (an apt name for a budding philematologist—a scientist who studies kissing) reported that the Chinese found mouth-to-mouth kissing nearly as horrifying as we find cannibalism. When Charles Darwin first visited the inhabitants of Malaya, he reported that there was absolutely no osculation going on, but plenty of nose rubbing. And the explorer Captain James Cook discovered similar behavior when he first visited Tahiti, Samoa, and Hawaii.7
Kissing may not be for everybody, but apparently it never fails to become popular wherever it is introduced. By all accounts, once Cook’s crews made landfall, everyone quickly became amateur philematologists. And today kissing is common throughout China. It is strange to say in an age of cell phones, computers, and satellites that we may actually be witnessing the last evolutionary stages of a cultural behavior that has been sweeping through the race for tens of thousands of years but hasn’t quite reached the finish line.
But even if all of us haven’t yet quite learned to kiss, how did any of us get started in the first place? Pheromones may provide a clue. In 1995 an enterprising group of Swiss researchers headed by zoologist Claus Wedekind decided to test the effects of scents on human behavior. The idea was that certain mysterious clusters of molecules called pheromones might shape some very important, even life-changing decisions that we all make, without us even consciously realizing it—whom we choose to marry, for instance.
Wedekind and his team first gathered up forty-four men and forty-nine women. They next tested and profiled all of their immune systems to map which diseases they would tend to resist well and which they wouldn’t. Wedekind then instructed the men to wear the same T-shirt to bed for two consecutive nights. Each was given unscented soap and told in no uncertain terms not to tamper in any way with how he smelled. Off went the men.
At the end of the obligatory two days, the same forty-four fellows took off their well-slept-in shirts and deposited them into several boxes that also contained other, completely new T-shirts. Now the forty-nine women were assembled, asked to sniff the shirts, and questioned about which ones they found most “sexy.” You would think the universal answer would be a resounding “None of them!” But as it turned out, the women did have a preference—and strangely enough, the shirts they preferred belonged to men whose immune systems were dramatically different from theirs. The women, in other words, tended to be attracted to the men who, if they were to have children with them, would father offspring capable of fighting off more diseases than either of their parents. That, of course, would make them more likely to survive (and pass along their genes).8 A very primal chemistry seemed to be at work.
The standard definition of pheromones is that they are naturally occurring compounds that instigate some remarkable behavior in members of the opposite sex. Scientists have known for some time that they exist in the insect and animal worlds, where their effect is indisputably powerful. For example, the cecropia moth, the largest in North America (and one of the most beautiful), has been known to catch a whiff of a female’s pheromones and gamely push itself upwind a full seven miles to reach and mate with her. Social insects such as bees, wasps, and ants can’t live without pheromones. They use them to maintain the complicated societies in which they live and work, which explains why their antennae insistently search out and wave at their surroundings wherever they go, hunting invisible molecular messages that signal them what their next move should be.
Mammals also rely on these chemical communicators. Male pigs exude a pheromone that goes by the nondescript name 5-androst-16-en-3-one, and it makes sows as amorous as Mae West in Night After Night. It is so reliable, in fact, that it is sold as BOARMATE to pig farmers who need to keep their supply of new piglets uninterrupted.9
Though the list of pheromone-driven behavior in nature is long and fascinating, scientists continue to wrangle over the precise role it plays when it comes to humans. For years they were thought to have no place in the human world. But the evidence is mounting, as Wedekind’s experiment indicates, that pheromones have a good deal to say about how we behave, especially when we are in the presence of the opposite sex.
In the Swiss test, it was as though certain chemical messengers evolved to ensure that opposites attract, at least opposite immune systems, the better to maximize the continuation of the species. You can see how this might be useful out on the savanna, where the survival of the group would take precedence over personal likes and dislikes. Without this kind of chemistry our ancestors may have gone extinct before they became our ancestors.
If pheromones do play a role i
n our personal lives, it might mean that today the reasons why we find some people appealing and others not has nothing to do with why we think we find them that way. Love, or at least attraction, might be blinder than we ever suspected. Whatever the case, our pheromonal predilections apparently go way back. We may not only share the trait with pigs, bees, and moths, but also with rats, who “read” the pheromones in the urine of the opposite sex and choose their mates accordingly, a kind of chemical date-matching system.
The difference between us and other mammals, however, is that they search for pheromones actively, sniffing out the mates most likely to create strong offspring and avoiding those who won’t. We, on the other hand, are completely clueless that any of these chemical conversations are taking place. The communication is entirely unconscious, which may help explain why some people fall in love “at first sight.” Love at first smell may be more accurate.
Until relatively recently it would have been unthinkable in scientific circles to theorize that silent chemical envoys secretly affect intimate decisions such as choosing a suitor or a spouse. Insofar as scientists thought about these questions at all, they had concluded that we simply didn’t have the organs necessary for sensing such things. Pound for pound, after all, rodents have much larger olfactory bulbs than we do. The chemistry of smelling is a much larger part of their world, and the worlds of most other mammals, including dogs and cats and cows. Part of the fragrance-sensing apparatus in rats, for example, is something called a vomeronasal organ, or VNO, which has evolved just for the recognition of pheromones. The VNO senses molecules in the environment that accelerate puberty, reveal pregnancy (and failed pregnancies), and even generate testosterone surges. It tells male rodents when it is best to mate and signals them when it is a bad idea.
For years it was assumed that if we humans ever had organs like these, we would have forsaken them long ago for lack of need. After all, why send messages chemically when we have these big brains and lavish vocabularies? But then in the 1970s, in a still-famous experiment, Martha McClintock, a psychology student at Wellesley College in Massachusetts, studied the menstrual cycles of 135 women who lived together in her college dormitory. She found that after spending several weeks in one another’s company, the menstrual cycles of her female dormitory mates drew together in nearly perfect synchrony. In other words, it appeared that bodies that had come together from all around the country to live in the same place had begun talking with one another, coming to agreement, silently and chemically, for no other reason than that they were in one another’s company. How?
Obviously this synchronization wasn’t the result of any conscious effort. Women cannot purposefully control the timing of their hormonal cycles. And though McClintock suspected that pheromones were behind the synchronization when she published her now famous findings in Nature in 1971, she couldn’t say so for certain.10 The technology didn’t exist for such minute molecular measurements. Nevertheless, her findings indicated that to the long list of complex ways we communicate, we could apparently add that we connected with one another by a kind of chemical telepathy that had nothing to do with conscious thoughts or feelings.
Following McClintock’s study, more evidence for human pheromonal communication emerged. In 1985 researchers at the University of Colorado discovered that we did indeed have working vomeronasal organs after all, in the form of a very small pair of ducts just inside our noses, one tiny pit in each nostril. The research even turned up evidence that the human VNO had its own proprietary nerve connections, wired directly to the brain, that operated altogether independently of the olfactory system that does most of our nose’s work. That meant that strictly speaking, pheromones didn’t really have anything to do with odors because we don’t actually smell them (although we may smell other odors that accompany them). Apparently it is all about the molecules reaching the VNO and triggering parts of the brain that in turn trigger very specific behavior. This makes pheromones the “words” in a direct, molecular conversation between the brain of one person and the body of another.
Women, for example, seem to be particularly tuned into a male pheromone called androstenol, an odorless molecule produced by male sweat glands. When women see pictures of men that have been sprayed with androstenol, they actually find the picture more appealing than one that hasn’t been sprayed, and it doesn’t matter whether it is an image of Mel Gibson or Joe the plumber. Another study, at University College in London, revealed that when women were exposed to androstenol they were more likely to have greater social contact with men in the hours that followed. It may not be BOARMATE, but it apparently made them more outgoing than usual, but only when they encountered men.
Still another study revealed that when theater seats were randomly inoculated with androstenol, women were more likely to sit in them than seats that were pheromone-free, unaware that they had been led to the seat literally by their noses. An experiment at the Monell Chemical Senses Center in Philadelphia even found that when women are consistently in the company of men, the length and timing of their menstrual cycles changes. They tended to ovulate more regularly, basically making them more predictably fertile. For mating couples who want to bring more babies into the world, that would be a good thing. But how odd that such personal behaviors are affected by chemicals about which we are completely oblivious.
Pheromones can have strange effects on men, too. One recent experiment showed that the female hormone copulin seemed to tune men into the women around them who were “wearing” it. To test a similar idea, the ABC News show 20/20 conducted an informal test. The network recruited two sets of twins, one male and one female. A member of each set was then sprayed with an unscented pheromone that was supposed to attract the attention of the opposite sex. The other members got nothing more than plain old witch hazel. They then stationed themselves in separate sections of a popular New York City bar, where they were told to just sit and do nothing. No charming smiles or evocative body language were allowed.
Neither of the male twins saw much action. They both received about the same amount of attention from women in the bar as they always did. But for the pheromone-scented sister, it was a different story. She attracted thirty different men, nearly three times more than the eleven whom her equally attractive twin received. The only difference, apparently: the silently communicating pheromone she had been sprayed with.11
How this happens precisely is still a mystery, but it provides some clues to pheromones’ connection to kissing. They seem to have a magnetic effect, encouraging members of the opposite sex (and gay members of the same sex12) to want to cuddle and embrace. We have all seen animals nuzzling, perhaps because their pheromones are at work. Some scientists have wondered if the nose rubbing of Inuits and Malayans is a nuzzling precursor of kissing, an effort to get closer to one another so we can more deeply inhale the intoxicating messages are bodies are tossing off.
So far the best that scientists can say is that the human VNO provides a hotline to our hypothalamus, the part of the brain that affects everything from body temperature and heart rate to emotions and sexual appetite. It is the hypothalamus that then goes on to revamp our behavior.13
Imagine the effect this might have had among our precursors—early humans throwing off chemical signals like party confetti that drew or repelled one another, totally unaware of how it was all happening. Picture Homo erectus, Neanderthal, or Cro-Magnon couples, sniffing, rubbing faces, and cuddling, mingling their scents. Unlike in the love life of rodents, these pheromones would not have been the sole arbiters of affection and attraction, just silent partners that led to the first kiss. As cheeks and breath and roaming hands came together; as personal attractions converged with primal chemistry and sensations grew stronger and richer, kissing—literally tasting and sharing one another with the most sensitive and sensual parts of our bodies—would have been a perfectly natural next step.
In fact, new research has revealed that while we sense pheromones (and all of the feelings th
ey can induce) by hijacking them out of the air, we also can “taste” pheromones with our tongues and lips, which enables us to gather even more chemical information from the person we are kissing. In other words, osculation would have been a natural, if unconscious, way to scan the gene pools of potential mates even more completely than simply inhaling. Maybe that is another reason why nature ensures that kisses feel so good. It is a way to encourage us to find the best possible mate so we will create more human beings, the ultimate goal of every self-respecting strand of DNA.
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The driving search for pheromones is not the only current theory about why we began to kiss. It is also possible that it began as a prehistoric feeding practice between parent and child. It could be that the two apparently separate theories are actually connected. The idea behind the feeding hypothesis is that hominid mothers prechewed food for their young, not unlike birds and other animals do, and then passed it along their children in a kind of kiss. Chimpanzees do this. Pressing outturned lips against lips may then have later developed to comfort a hungry child when food was scarce, and eventually come to express love and affection. In time this parental kissing might then have found its way into use among lovers who brought new variations to the practice.
There is a certain amount of sense in connecting nurturing and appetites with kissing. It introduces emotion into the equation, and it makes kissing more than a soulless fishing expedition for finding fertile, healthy mates.14 Food, hunger, passion—they are all connected on some level. An ancient poem from the Bible’s Song of Songs (4:11) says it all: “Thy lips drip as the honeycomb, my spouse:/Honey and milk are under thy tongue.” We are all hungry for affection, after all, and for someone out there.