When passion takes a grip, a kiss locks two humans together in an exchange of scents, tastes, textures, secrets and emotions unlike any other act. We kiss furtively, lasciviously, gently, shyly, hungrily and exuberantly. We kiss in broad daylight and in the dead of night. We give ceremonial kisses, affectionate kisses, Hollywood air kisses, kisses of death and, at least in fairy tales, pecks that revive princesses.
Lips may have evolved first for food and later applied themselves to speech, but in kissing, they satisfy hungers of a different kind. In the body, a kiss triggers cascades of neural messages and chemicals that transmit tactile sensations, sexual excitement, feelings of warmth, motivation and even outright euphoria.
Not all the messages are internal. After all, kissing is a communal affair. The fusion of two bodies dispatches communiqués to your partner as powerful as the data you stream to yourself. Kisses can convey important information about the status and future of a relationship. So much, in fact, that, according to recent research, if a first kiss goes poorly, it can stop an otherwise promising relationship dead in its tracks.
Some scientists believe that fusing lips first evolved because it facilitates mate selection. “Kissing,” said evolutionary psychologist Gordon G. Gallup, Jr., of the University at Albany, S.U.N.Y., in a September 2007 interview with the BBC, “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.” Kissing may even reveal the extent to which a partner is willing to commit to raising children, a central issue in long-term relationships and one that is crucial to the survival of our species.