There are a vast array of kisses, from perfunctory to serious, but there is something particularly special about romantic and sexual kisses. One of the benefits of kissing is that it allows for loads of data to be exchanged, which then makes it possible for people to unconsciously assess their potential and permanent partners. The lips are one of the thinnest layers of skin on the human body and densely populated with nerve endings, explains Fisher. This allows people to pick up on the temperature, taste, and smell of someone. Through smell, people are able to assess all kinds of information about others, such as the health of their immune system or their fertility. Evolutionary anthropologist and University of Kent professor Sarah Johns, Ph.D., suggests that’s why some cultures may not need to kiss in order to gain certain knowledge. When people are wearing less clothing or bathing less, they are able to tell that information without needing to get too close. She also notes that “exposure to showing people kissing in a romantic way may have an impact on people thinking it’s more desirable,” along with exposure to people of higher statuses practicing kissing because people are more likely to emulate them. When looking to humans’ closest relatives, primates, kissing actually is a common practice, says Fisher. And while there isn’t enough data collected on all animal habits, there is enough evidence to show that face touching, face rubbing, or face licking is involved across many species. Those actions put “participants into such close contact that there is still exchange of intimate, potentially relevant genetic and reproductive information. So it does appear to be a hardwired courtship strategy,” confirms Gallup. However, just because there are deal-breaking kisses does not mean the people in question are bad kissers. Gordon asserts that someone who “may be a good kisser for one person may be a bad kisser for another.” In other words, if you find someone to be a good kisser, that may be a reflection of the fact that that particular person is a good genetic match for you. According to Match’s 2018 Singles in America study, which Fisher helps lead, 81% of men and 62% of women felt it was appropriate to kiss on the first date. This again demonstrates that kissing is used as a mate assessment tool. That said, men and women tend to report kissing for very different reasons. Men tend to kiss as a means of gaining sexual favors or as a way to achieve reconciliation, says Gordon. Women on the other hand tend to kiss as a means of establishing a romantic relationship and monitoring the status of a relationship. Fisher adds that women use kissing as a way to look further down the road, meanwhile asking themselves important questions such as: Do they like this person well enough? Would they make a good partner? Are they patient? According to Fisher, humans have evolved three distinctively different brain systems for mating and reproduction: sex drive, feelings of intense romantic love, and feelings of deep attachment. Saliva contains a lot of testosterone, which helps to trigger the sex drive. And since the internal cheek cells are well built to absorb testosterone, wet kisses cause arousal. As explained earlier, romantic love is triggered by dopamine. And then the third brain system, attachment, is impacted by oxytocin, sometimes referred to as the “cuddle hormone.” Oxytocin brings about feelings of emotional closeness and “cosmic union,” explains Fisher. She also says that in long-term couples, a kiss not only increases levels of oxytocin but reduces cortisol, the body’s main stress hormone. That makes kissing a powerful tool for mating. To put it plainly, there is nothing simple about a kiss. “It’s a hardwired, evolved, largely unconscious interaction that occurs and subserves a basic reproductive biological function that most people have no insight into whatsoever,” says Gordon. And like so many other things in life, humans have no control over how kissing affects our behavior. We’re just along for the ride.
