Kissing

Some scientists believe that the fusing of lips evolved because it facilitates mate selection. “Kissing,” said evolutionary psychologist Gordon G. Gallup, Jr., of the University at Albany, State University of New York, in a September 2007 interview with the BBC, “involves a very complicated exchange of information—olfactory information, tactile information and postural types of adjustments that may tap into underlying evolved and unconscious mechanisms that enable people to make determinations … about the degree to which they are genetically incompatible.” Kissing may even reveal the extent to which a partner is willing to commit to raising children, a central issue in long-term relationships and one that is crucial to the survival of our species.

The brain goes into overdrive during the all-important kiss. It dedicates a disproportionate amount of space to the sensation of the lips in comparison to much larger body parts. During a kiss, this lip sensitivity causes our brain to create a chemical cocktail that can give us a natural high. This cocktail is made up of three chemicals, all designed to make us feel good and crave more: dopamine, oxytocin, and serotonin. Like any cocktail, this one has an array of side-effects. The combination of these three chemicals work by lighting up the 'pleasure centres' in our brain. The dopamine released during a kiss can stimulate the same area of the brain activated by heroin and cocaine. As a result, we experience feelings of euphoria and addictive behaviour. Oxytocin, otherwise known as the 'love hormone', fosters feelings of affection and attachment. This is the same hormone that is released during childbirth and breastfeeding. Finally, the levels of serotonin present in the brain whilst kissing look a lot like those of someone with Obsessive Compulsive Disorder. No wonder the memory of a good kiss can stay with us for years.

kissing is a communal affair. The fusion of two bodies dispatches communiqués to your partner as powerful as the data you stream to yourself. Kisses can convey important information about the status and future of a relationship. So much, in fact, that, according to some research, if a first kiss goes bad, it can stop an otherwise promising relationship dead in its tracks.

From an evolutionary perspective, the exchange of saliva during a kiss enables a subtle, subconscious form of mate assessment. Saliva contains hormones like testosterone, which can trigger or enhance arousal and signal sexual availability. It also carries genetic information about a person's immune system. When we kiss a potential mate, we might subconsciously be testing their biological compatibility with us.