We kiss in greeting. We blow air kisses to say farewell, or when we are too far away to lock lips. Worshipers kiss religious artifacts. Tourists visiting Ireland often stop by Blarney Castle to kiss the Blarney Stone. Parents kiss "ouchies" to make them feel better. When we fight, we "kiss and make up". When passion takes hold, so do our lips. In fact, there is nothing like the electrical exhilaration of a first kiss. Just ask 90% of the people in the world, who enthusiastically engage in the practice.
Why does this simple act signify so much?
Researchers from many different fields are revealing hidden complexities behind the art of osculation, the scientific term for kissing. What happens in the body during a kiss may suggest the biological or evolutionary beginnings for sharing lip space. First, the anatomy of the lips make them highly sensitive to touch. They are not only the slimmest layer of skin on the human body, but are also an area with one of the most densely populated sensory cells (1). But anyone who has ever been kissed knows that the sensations involved in kissing aren't just in your mouth: your whole body reacts physically to being kissed, and your brain is what tells your body that something feels good. Of the 12 cranial nerves that affect brain function, five are communicating important information to the brain about scents, tastes, textures, and even emotions. After receiving this information, the brain unleashes a myriad of chemical messages to relieve stress, bond socially with potential mates and friends, increase motivation to mate, and provide sexual stimulation (1). In fact, kissing may be like an addictive love drug. Levels of cortisol, involved in modulating stress reactions in the body, drop following a kissing episode causing a relaxation effect. Locking lips, especially someone for which you feel romantic love, also releases endorphins and boosts other brain hormones and neurotransmitters involved in pleasure, euphoria, and reward. Levels of These chemicals act in brain areas that keep us coming back for more. So kissing may be a simple act that plays a complex role in falling in love', a reproductive mating strategy that may have evolved to enable humans to focus their mating energies on specific people (1).
~GIMME A PECK~
If you think about it, kissing is pretty disgusting. You share much more than mutual attraction and love for your partner; you're also sharing saliva and potentially millions of bacterial colonies during a good juicy kiss (2). Originally, our ancestors might have shared more than just saliva. In the 1960s British zoologist and author Desmond Morris first proposed that kissing might have evolved from feeding practices in which primate mothers chewed food, pucker their lips, and then fed their children mouth-to-mouth. Even when food was scarce, primate babies might have looked to the mouths of their mothers for food, finding comfort from puckered lips when no food was found. Early humans may have practiced the same methods with their babies, the gesture continuing as a display of affection or comfort after the babies learned to eat solid food (1). Those of us raised in Western culture learned to kiss those we treasure and adore, but many scientists believe that osculation may also have an instinctive component, directed from our genes.
~A KISS TO BUILD A DREAM ON~
Because women must invest more energy in producing children, and have a shorter window than men in which to do so, they may need to be more selective about whom they choose for a partner. Could a simple kiss possibly tell us this information? Anthropologists, psychologists, and ethnologists believe there might have evolved another kind of sharing a type of rating system used as a strategy in courtship. As many of us have figured out, that very first kiss may be pivotal to a future relationship. The evolutionary psychologist Gordon Gallup and colleagues (3) found that over half of men and women surveyed reported that there have been times when an initial attraction to someone was thwarted by the kiss of death a bad first kiss that had no specific flaws except one; it simply did not feel right'. Whereas men may see a deep passionate kiss as a way of advancing through the bases to a home run, women may use kissing to gauge information about the level of commitment in a current relationship. For a woman, a passionate kiss may communicate something besides willingness to have sex it may tell her that her exuberantly kissing partner may have the energy to be good at fathering, and the commitment to stick around and help care for the kids (3).
~KISSING COUSINS? ~
But being a skilled kisser may not seal the romantic deal. Some researchers believe that we convey important information about the genetic compatibility of our prospective mates. Smelling a potential mate while smooching may suggest important reproductive information, albeit unconsciously. Whether chemical messengers called pheromones may be involved remains controversial. Although humans are not known to have a specialized pheromone detector (like rats and pigs), some biologists believe that people are able to sense pheromones with our nose (1). Scientists believe that a woman may be able to smell certain proteins while kissing, and that what she smells may affect whether she finds her partner attractive. In some animals males and females tend to choose mates with differing major histocompatibility complex (MHC) markers in the immune system. Most biologists think mice are able to literally smell how alike or unlike a potential mate's MHCs are to their own and avoid those with very similar ones. There is also some evidence that people prefer to mate with those who have differing MHCs. Pheromones may be responsible for findings that women are attracted the scents of T-shirts worn by men whose immune systems are genetically compatible with their own. From a Darwinian perspective, sexual selection is the key to passing on your genes. As a reproductive strategy, this helps prevent us from becoming "kissing cousins", mating with someone who shares much of our DNA, and thereby making healthier babies (4).
~A FAREWELL KISS~
No matter what what we think we have figured out, kissing, and its' role in sexual attraction, will hopefully always remain a mystery. If the art of love ever completely gives way to scientific formulation and design, I hope my lips are dead and gone.
1. Walter, C. (Feb/March 2008). Affairs of the Lips. Scientific American Mind, 19(1), 24-29.
2. Wilson, T.V. (2008). How Kissing Works. Retrieved from Howstuffworks.com: http://people.howstuffworks.com/kissing.htm February 3, 2008.
3. Gallup, G.G., Hughes, S.M., & Harrison, M.A. (2007). Sex differences in romantic kissing among college students: An evolutionary perspective. Evolutionary Psychology, 5(3), 612-631.
4. Alexander, B. (2008). What's the Secret to Sexual Compatibility? Retrieved from MSNBC.com: http://www.msnbc.msn.com/id/22452653/ February 3, 2008.