Kissing, for the hopeless romantic, is the best thing you could do with your lips. The practice of mouth-to-mouth sexual kissing is common in more than 90 percent of human cultures. Many theories have been formulated to try to explain why we kiss but none have accounted for this uniquely human practice within an evolutionary framework.
Researchers from the University of Leeds in Yorkshire, England, were the most recent to give it a shot and say that kissing is nothing romantic – they believe that it developed to transmit germs.
Human cytomegalovirus (HCMV) is a virus which lurks in saliva and other bodily fluids and infects between 50 to 80 percent of American adults. HCMV normally causes no problems but it can be extremely dangerous for pregnant women and can kill unborn babies or cause birth defects, including cerebral palsy and deafness.
In the journal Medical Hypotheses, Dr. Colin Hendrie explains that prior to pregnancy, a woman can develop immunity from the cytomegalovirus through mouth-to-mouth contact and saliva exchange with a particular man carrying HCMV.
The hypothesis proposes that mouth-to-mouth kissing enables women to control when they become infected with a particular man’s HCMV and so protect their offspring from primary infection during vulnerable times in their development. A woman, however, only gains this protection if she also avoids infection by other men. This means that she must only kiss one particular man because kissing the same person for about six months will give her optimum protection from HCMV.
During the first kiss (which is assumed to be chaste and short), the man spreads just a small amount of HCMV to the woman to reduce her risk of becoming ill. As the relationship progresses and their kisses become more passionate and torrid, the woman’s immunity also builds up, and when she becomes pregnant, the risk of her unborn child getting infected by HCMV is significantly lower.
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