Just in time for Valentine's Day, a panel of scientists examined the mystery of what actually happens when we kiss. Regardless, the practice of kissing is nearly universal. It is practiced in at least 90 percent of cultures among sexual or romantic partners, experts say. Recently, scientists investigated the biological factors underlying that ubiquitous expression of love; its science even has a name: philematology.
Helen Fisher, an anthropologist at Rutgers University in New Jersey, said for men the kisses appear to provide data on a woman's estrogen level. That would let them know where the woman is in the fertility cycle. Women, on the other hand, may be getting unconscious information on whether a potential partner has an immune system different from theirs. Marrying someone with complementary immunity could lead to healthier offspring with a broad range of disease resistance.
"There's a good deal of evidence that saliva has testosterone in it, and there's also evidence that men like sloppier kisses with a more open-mouth," said Helen E. Fisher, a Rutgers University anthropologist and author of “Why Him? Why Her?: Finding Real Love By Understanding Your Personality Type.” “And that suggests to me that they are unconsciously intending to transfer testosterone to stimulate sex drive in women,” Fisher said .
In the first experiment, Hill explained, pairs of heterosexual college students who kissed for 15 minutes while listening to music experienced significant changes in their levels of the chemicals oxytocin, which affects pair bonding, and cortisol, which is associated with stress. Their blood and saliva levels of the chemicals were compared before and after the kiss. Both men and women had a decline in cortisol after smooching, an indication their stress levels declined.
A second experiment in a more romantic setting -- a secluded room with jazz music, flowers and electric candles -- looked at nine heterosexual couples and three lesbian couples. Researchers found that the longer the relationship of a couple, the more the cortisol levels declined in both partners. The heterosexual women, moreover, said they felt greater intimacy with their partners than the heterosexual men or the homosexual women did, while all groups expressed equal satisfaction in kissing their partners. The researchers are in the process of analyzing oxytocin levels in this experiment.
Furthermore, it's not the lips that deserve most of the credit for why we kiss. The brain does much of the heavy lifting, and new technology is allowing scientists to examine this better. For example, the neurology research of Dr. Vilayanur Ramachandran of the University of California at San Diego, suggests that kissing stimulates mirror neurons in the brain that promote empathy and reduce inhibitions. In other words, kissing truly could be the real language of love.
As for the origins of kissing, one theory is that kissing evolved as an extension of the way mothers used to feed their children. Kissing appears infrequently in Greek and Roman art, but was widely practiced, despite the spread of skin disease at that time by facial kissing. And there was a potential for social faux pas by kissing the wrong person at the wrong time.
