The kiss may have evolved for reasons that are far more practical — and less alluring — than previously thought.
British scientists believe it developed to spread germs.
They say that the uniquely human habit allows a bug that is dangerous in pregnancy to be passed from man to woman to give her time to build up immunity.
Cytomegalovirus, which lurks in saliva, normally causes no problems. But it can be extremely dangerous if caught while pregnant and can kill unborn babies or cause birth defects. These can include problems ranging from deafness to cerebral palsy.
Writing in the journal Medical Hypotheses, researcher Dr. Colin Hendrie from the University of Leeds said: “Female inoculation with a specific male's cytomegalovirus is most efficiently achieved through mouth-to-mouth contact and saliva exchange, particularly where the flow of saliva is from the male to the typically shorter female.”
Kissing the same person for about six months provides optimum protection, he added. As the relationships progresses and the kisses become more passionate, her immunity builds up.
Previously scientists have claimed that kissing acts as a form of evolutionary quality control, with saliva holding clues to fertility, health, and genes.
Although not as romantic a notion as we might like, the theory that kissing may have a far more important biological function than the pleasure of bonding makes sense.
Sharing germs through kissing, prior to pregnancy, which allows the woman to develop natural immunity that protects the couple’s offspring, is a simple and elegant solution against a potentially devastating infection.
The Curious Biology of Sexual Attraction and Lasting Love
Needless to say, the reason why we kiss is not the only area of human sexuality that has been explored by researchers. Virtually every nook and cranny of sexuality and procreation has been investigated, to find out the elusive reasons for why you do what you do.
Pheromones, for example, likely set the stage for the “immunity-building” exercise of kissing. Because without the right chemical signals, you probably wouldn’t get around to kissing in the first place.
Pheromones are chemical signals that animals secrete to communicate their gender or reproductive status to other animals – and humans are no exception.
Even though you don’t consciously recognize the smell of pheromones, these chemicals likely play a role in helping you find a suitable partner.
For example, if you’ve ever found yourself inexplicably attracted to a stranger you’ve just met, it could very well be their chemical signals that you find irresistible. Humans tend to be attracted to those with a dissimilar genetic make-up to themselves, which is signaled by subtle odors. This ensures genetic diversity for the species.
Researchers have actually confirmed the presence of a “secret sex nerve” (Nerve “O”), which has endings in your nasal cavity. Nerve O’s fibers go directly to the sexual regions of your brain, and because Nerve O bypasses the olfactory cortex, it does not register a conscious smell, but rather identifies chemical sexual cues.
Interestingly, this biological strategy designed to ensure healthy offspring and a diversified gene pool, has been artificially altered through modern medicine, with the invention of the contraceptive pill.
As it turns out, pregnant women are drawn to people with a similar chemical makeup. And when a woman takes a hormonal contraceptive, her body believes, in a sense, that she is pregnant even though she’s not.
This hormonal alteration causes her to become unconsciously attracted to men with a similar, rather than different, chemical makeup. Unfortunately, couples who have high levels of chemicals in common are more likely to encounter fertility issues, miscarriage, and even infidelity.
It could even explain the inexplicable – why so many people have such a hard time maintaining long-term attraction, and staying “in love”… Because according to researchers, odor perception also plays a significant role in maintaining attraction to partners.
When the woman stops taking the contraceptive pill, she again becomes more attracted to people with a dissimilar genetic blueprint from her own. So, the level of attraction felt to a specific person while on the pill may change once she stops taking the pill.
Finding a partner who is chemically different from yourself appears to give you the best chance of reproducing successfully, and enjoying continual attraction to each other, without infidelity.
For some people, this may be enough to reconsider the pill, but there are even more important reasons to avoid birth control pills. Birth control pills alter many chemical signals in your body, which is the real reason why I strongly suggest that women avoid birth control pills like the plague and seek out natural family planning methods instead.