Playful, platonic, passionate, or parental, kisses transmit a surprising amount of information. In fact, they even play an evolutionary role in fertility. In spite of the old song, it turns out that a kiss is almost never “just a kiss.”
In the art and science of romance, there’s nothing more powerful than a kiss. There’s also little question that when a couple is trying to start a family, too often that all-mighty kiss becomes secondary (ok, it’s not really on the priority list at all) to ovulation cycles, egg dropping, and sperm counts. But that passionate make-out session you’re skipping may actually be one very important step in the process of conceiving a child.
It’s now pretty widely agreed that stress can have a negative impact on fertility, but what’s not so well-known is that kissing may actually relieve it. “Higher anxiety and depression levels have been found in both partners of infertile couples,” says Mohit Khera, M.D., MPH, an assistant professor of urology at Baylor College of Medicine in Houston, Texas. “Studies have shown that emotional distress is associated with difficulty in conceiving.”
And kissing, the all-natural stress reliever, can help. “Relaxing and cuddling, especially with intimacy, can enhance fertility,” says Jacob Teitelbaum, M.D., author of From Fatigued to Fantastic! (Avery, revised 3rd edition 2007). A kiss on the lips literally triggers the brain to secrete a rush of feel-good chemicals, including norepinephrine, dopamine, and phenylethylamine, explains Andréa Demirjian, author of Kissing: Everything You Ever Wanted to Know About One of Life’s Sweetest Pleasures (Perigee Trade, 2006).
Kissing may also be “part of an evolved courtship strategy,” suggests Gordon G. Gallup, Jr., Ph.D., professor of psychology at the University at Albany in upstate New York, and primary author of a study published this past August in the online journal Evolutionary Psychology. When Gallup and his co-authors surveyed more than 1,000 University at Albany students, they found that a greater percentage of men preferred wetter, open-mouthed kisses than did women, whether early on in a courtship or in a long-term relationship.
One possible explanation for this difference may be that biology trumps romance. “A more moist kiss may signal to a male that the female is sexually receptive. Or, males may simply require greater salivary exchange to facilitate assessments of female fertility,” explains Susan Hughes, Ph.D., assistant professor of psychology at Albright College in Reading, Pennsylvania, and one of the study’s co-authors.
Breath odor and saliva, some studies suggest, may provide clues to a woman’s fertility. The rise in estrogen that occurs near the onset of menstruation triggers the shedding of body cells, and an increase in sulfur compounds in the mouth, each of which could cause unpleasant odors, Hughes explains. “Furthermore, females produce certain distinctive yet odorless molecules in saliva while ovulating that might be detected by males during kissing.” And male saliva contains measurable amounts of testosterone, which can affect libido. In other words, a kiss may “transmit[s] a sumptuous supply of data ranging from health, fertility, and commitment to sexual receptivity” as senior author Gallup told the Albany Times Union.