Kissing

Kissing is a highly species-typical instance of human behavior. Why do people kiss? Does kissing have important consequences? Do men and women use kissing to achieve different objectives? What about kissing technique? Why are males more likely to attempt to initiate open mouth kissing with tongue contact?

The origin of kissing behavior is a good place to start. Long before the invention of blenders and baby food, mothers probably chewed up food and then transferred small portions of the food from their mouth to their baby's mouth to introduce solid food into the baby's diet. Some people theorize that kissing is an evolved derivative of this primitive feeding gesture between mother and child.

There are at least three different types of kisses. Kissing can be used as a ritualized symbolic greeting gesture, as when people meet and kiss each other on the cheek or hand. Kissing on the face but rarely the lips also occurs among family members as a gesture of affection and caring between close relatives. Romantic kissing, on the other hand, is more likely to involve kissing on the lips and often has mating or sexual overtones.

Romantic kissing occurs in over 90 percent of human cultures. Even among those cultures where kissing is absent, courtship often involves face touching, face licking, face rubbing, and nose-to-nose contact, which like kissing brings the participants into close intimate facial contact. Some of humans' closest living relatives, chimpanzees and bonobos, appear to engage in kissing behaviors as well.

Kissing may be part of an evolved courtship ritual. Based on a recent study of 1,041 college students all but five had experienced romantic kissing, and over 20 percent estimated kissing more than 20 partners. When two people kiss, there is a rich and complicated exchange of information involving chemical (smell and taste), tactile, and postural cues. Kissing can have profound consequences for romantic relationships. A kiss will not necessarily make a relationship, but the evidence shows that it can break or kill a relationship. Most students who were surveyed report having found themselves attracted to someone in one or more instances, only to discover after they kissed him or her for the first time that they were no longer interested. It would appear, therefore, that kissing may activate evolved, hardwired unconscious mechanisms that function to assess the genetic compatibility, reproductive viability, and health of a prospective partner.

Evolution is not about survival, it is about reproduction. When it comes to competition for passing genes on to subsequent generations, insemination is the name of the game for males. For females, however, insemination is the mere beginning of the reproductive process that includes pregnancy, childbirth, breast feeding, and extended periods of childcare that can span many years. The costs and consequences of reproduction are dramatically different for females than for males. Because females bear the burden of the reproductive costs, females have been selected to put a lot of emphasis on making careful, judicious mate choices. Since females pick up the tab when it comes to reproduction, females have a vested interest in the other 50 percent of the genes being carried by each of their children. Clearly, females that not only mated preferentially with high-quality males but also picked mating partners who were likely to enter into a long-term committed relationship that involved providing for and protecting her and her dependent children would have had an adaptive advantage.

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