Love: A kiss is just a kiss … or is it?

“A kiss is a lovely trick designed by nature to stop speech when words become superfluous.”
—Ingrid Bergman

This Valentine’s Day, let’s contemplate and celebrate romantic kisses, those warm, moist, dazzlingly intimate smooches that usually lead to even juicier excitements but can be perfectly delightful all by themselves.

There are many other kinds of kisses, of course, like the cheek brushings we give in greeting or the nuzzling kisses we tease our children with when we tuck them in at night. Indeed, kissing is an all-purpose gesture, one that can convey a wide range of feelings, from the most intense sexual desire and deepest familial love to hostility or foreboding, as in “kiss my ass” or the mob boss’ “kiss of death.”

We kiss under the mistletoe, we kiss the Blarney Stone. The bride and groom seal their marriage with a kiss, and lovers kiss at midnight when New Year’s Eve slides into New Year’s Day. The pope kisses the ground when he arrives in a country, and followers kiss his ring. As children we sing kissing songs ("Johnny and Mary sitting in a tree/ K-I-S-S-I-N-G …"), and as teenagers we play kissing games like “Post Office” and “Spin the Bottle.”

But when we think about kissing, we invariably dwell on the wonders and delights of romantic kissing, of what happens when passion grips two lovers and they bring their mouths together, nibbling lips and delicately sliding their tongues into each other’s mouth. Say “kiss” to someone, and chances are that’s what comes to mind.

It’s a good thing that kissing is such a passionate and consuming activity, because the last thing anyone would want to do at such a moment is consider what bacteriologists say about it, how they warn of veritable armies of germs that march from mouth to mouth when people kiss. Well, let them march. Kissing is too much fun to be foiled by mere bacteria. Besides, a soupçon of danger adds to the excitement.

Anthropologists estimate that 90 percent of us smooch. Apparently there are a few people, hidden away in tribal niches in obscure parts of the world, who simply don’t see kissing as erotic. They don’t know what they’re missing.

The word “kiss” comes from the Old English cyssan, “to kiss,” a derivative of coss, “a kiss.” Both words are Germanic in origin. Modern German, it turns out, has some 30 different words for kissing, including one, nach-chüssen, that means a kiss “making up for kisses that have been omitted.” Who knew Germans were such fastidious kissers?

In fact, it was a German, Martin von Kempe, who in the 17th century wrote the longest single work devoted to the kiss, a thousand-page tome—the Opus Polyhistoricum … de Osculis—that drew on classical, biblical, legal, medical and other learned sources to form a veritable encyclopedia of kissing.

Scientists don’t know, or don’t fully agree about, whether we kiss because it’s an instinctive or a learned behavior, nature or nurture. Those who lean toward nature note that other animals such as nonhuman primates exhibit kissing behavior, even seem to kiss and make up. And those of us who share our lives with dogs or cats know they sometimes lick and groom each other, as well as their human companions, in a manner that resembles kissing.

Only one other animal mines kissing for its erotic value, however. As Joshua Foer, writing in The New York Times, puts it, “only humans and our lascivious primate cousins the bonobos engage in full-fledged tongue-on-tongue tonsil-hockey.”

Anthropologists think kissing might have originated with human mothers feeding their babies much as birds do, first chewing the food and then passing it from their mouths to their infants’ mouths. It would have been natural, once the babies developed teeth and the ability to chew their own food, for mothers to kiss them to comfort them or show affection.

There’s one problem with this theory: Women in a few modern indigenous cultures continue to feed their babies that way, but in some of those cultures erotic kissing didn’t occur before Westerners introduced it.

On the nurture side, Foer notes that Vaughn Bryant, an anthropologist at Texas A&M, has traced the first recorded kiss back to India, home of the Kama Sutra. Sometime around 1500 BCE, early Vedic scriptures mention people “sniffing” with their mouths, and later writings describe lovers “setting mouth to mouth.” Bryant believes the kiss spread westward after Alexander the Great conquered the Punjab in 326 BCE.

The ancient Romans were big kissers, though it’s unclear how much erotic smooching went on, dentistry being what it was at the time. For many centuries kissing was largely a ceremonial means of expressing and cementing social, personal and political relationships.

Indeed, it’s only since the advent of dental hygiene about 800 years ago that the mouth and lips have been free to be an erogenous zone and kissing has become a popular source of erotic pleasure.

Kissing facilitates mate selection, some scientists say. This is especially true of first kisses, which convey complicated information about the possibilities of a relationship. In fact, recent research shows that, if a first kiss goes bad, it can put the kibosh on an otherwise promising romance.

A January 2008 article in Scientific American by Chip Walter, ‘Affairs of the Lips: Why We Kiss,” quotes evolutionary psychologist Gordon G. Gallup, of State University of New York, Albany: ‘Kissing involves a very complicated exchange of information—olfactory information, tactile information and postural types of adjustments that may tap into underlying evolved and unconscious mechanisms that enable people to make determinations … about the degree to which they are genetically incompatible.”

Gallup found that 59 percent of the men and 66 percent of the women he and his colleagues studied admitted there had been times when they’d been attracted to someone only to be turned off after the first kiss. As Walter puts it, ‘The ‘bad’ kisses had no particular flaws; they simply did not feel right—and they ended the romantic relationship then and there—a kiss of death for that coupling.”

But a first kiss taps into ancient courtship rituals and language in a way that would seem to defy Gallup’s scientific analysis. As the German writer Emil Ludwig wrote, ‘The decision to kiss for the first time is the most crucial in any love story. It changes the relationship of two people much more strongly than even the final surrender; because this kiss already has within it that surrender.”

Still, it’s hard to argue with Gallup’s findings that men and women see kissing differently. For most of the men he interviewed, a deep kiss was largely a way to get to the next base, so to speak, while most women were looking to take the romance to the next stage emotionally. They were checking the guy out to determine whether he’d make a good long-term partner.

Well, yes and no. Kissing has a way of putting such calculations on hold, at least for the duration of the smooch. The lips are among the most sensitive parts of the human body. Skin is thinnest there, and the lips are densely populated with sensory neurons. As Walter writes, ‘When we kiss, these neurons, along with those in the tongue and mouth, rocket messages to the brain and body, setting off delightful sensations, intense emotions and physical reactions.”

Needless to say, perhaps, prudence and self-consciousness are in short supply at such times. ‘The pupils dilate, breathing deepens and rational thought retreats,” Walter writes. ‘For their part, the participants are probably too enthralled to care.”

As a relationship evolves, Gallup found, women tend to use their partners’ enthusiasm levels as a way of measuring their level of commitment. For reproduction reasons, they need to choose a mate who’s good at fathering children and is going to stick around and help rear them.

Scientists seem to like to study kissing as much as the rest of us enjoy doing it. They’ve examined why we tend to tilt our heads right when we kiss, whether we can scent each other’s pheromones when we kiss, how the body reacts when we kiss and how cultural factors affect our kissing.

Somehow, though, kissing defies complete scientific analysis—and will always do so. Romantic love is full of mystery; no amount of research will ever explain it fully. And that’s just the way we like it.