The Evolutionary Significance of Kissing

Kissing, an intimate act between two people, holds a significant place in human relationships. This article explores the origins and benefits of kissing, shedding light on why it became a widespread practice. While initially it may seem strange, understanding the positive effects and evolutionary psychology behind kissing provides insight into its significance as a form of connection and mate selection.

Let's delve into the act of kissing, where two individuals' lips come together. On average, a person will spend approximately 20,160 minutes of their lifetime engaged in this activity. Remarkably, the longest recorded continuous kiss lasted for 58 hours, 35 minutes, and 58 seconds. However, the question remains: why do we kiss? Upon reflection, it may seem peculiar, right? While modern society associates kissing with peace, respect, passion, and love, one might wonder if the first-ever human kiss was merely an unsavory encounter. Let us explore what we do know about kissing: it provides pleasure and offers health benefits. A passionate kiss can burn around 2-3 calories per minute and triggers the release of epinephrine and norepinephrine, which accelerate heart rate. Additionally, increased frequency of kissing has been linked to lower levels of bad cholesterol and perceived stress.

The widespread occurrence of these positive effects associated with kissing did not happen by chance. How did brains and bodies develop a fondness for kissing? One popular tale suggests that the shape of Pacman, a well-known video game character, was inspired by a pizza with a missing slice. However, Toru Iwatani, the creator of Pacman, acknowledged that this story was only partially true. The shape of Pacman was also influenced by the rounded form of the Japanese character representing "mouth." It is through mouths and Pacman's favored activity of eating that we can begin to understand the essence of kissing. Evolutionary psychologists propose that the concept of kissing as we know it today may have evolved from a practice called "kiss-feeding," which involves the exchange of pre-chewed food between mouths. This behavior is observed among mother birds and many primate species. Not long ago, it was also commonplace between human mothers and their children. In fact, before the availability of commercially produced or do-it-yourself baby food instructions, this practice made practical sense.

In recent times, Alicia Silverstone shared a video of herself engaging in mouth feeding with her child. This act appeared peculiar to some individuals. Despite the exchange of saliva, which, similar to any contact with an infant, can transmit pathogens, both healthy mothers and healthy children can derive benefits from kiss feeding due to its nutrient-providing nature. It offers carbohydrates, proteins, iron, and zinc, which may not always be present in breast milk. Moreover, adult saliva aids in the pre-digestion of food, facilitating the baby's absorption of vitamins such as B-12. Thus, mouth-to-mouth attachment carries a historical significance tied to intimacy, trust, and closeness. Additionally, saliva carries valuable information about one's identity and health status, while the mucous membranes in our mouths allow the permeation of hormones like testosterone, making a kiss a means of assessing a potential mate's taste.

A good kiss can serve as biological evidence that the person you're kissing might be a suitable mate. Therefore, prehistoric individuals who enjoyed kissing and engaged in it more frequently may have made better mate selection choices, leading to increased reproductive success and eventually establishing kissing as a norm in our society. Even infants, despite their limited vision, can recognize the benefits of kissing. From birth to around four months, babies can only focus on objects approximately 8-10 inches away from their face, coincidentally the distance to their mother's face during breastfeeding. As a result, faces, particularly those directly looking at them, become the first things infants can clearly focus on and perceive. This early preference for faces may explain our exceptional ability to detect and recognize faces, even when they are not present, a phenomenon known as "pareidolia." Given our cooperative nature, it is advantageous for us to excel at facial recognition and accurately convey when we are looking at someone and when someone is looking directly at us.

For a predator relying on remaining unseen, a less obvious gaze is crucial. Surprisingly, the white scleras, the portion surrounding the iris, in human eyes are not merely coincidental but an essential aspect of our eye structure that enables us to quickly determine the direction of someone else's gaze with a glance. Additionally, our brains possess remarkable gaze-direction networks consisting of individual neurons that activate when someone stares directly at us, but cease firing if the gaze shifts even slightly. Hence, we possess the ability to sense when we are being observed. Humans are highly sensitive to this perception, even individuals with "Scopophobia," the fear of being stared at. However, it is important to note that in order for this detection to occur, the other person's gaze must be within our line of sight and field of vision. If the gaze originates from behind, there is no evidence to suggest that individuals can detect being watched.

The concept of the "Psychic Staring Effect" belongs to the realm of pseudo-science and lacks widely accepted evidence from studies. An alternative explanation for the phenomenon is that people tend to look up and make eye contact when they sense someone watching them, which creates the perception of attachment through gazes. However, what about attachment in the absence of observers? One theory suggests that an infant's attachment to their mother is not based on vision or staring, but rather on the provision of nourishment. The idea is that we develop a bond with our mothers because they serve as a source of life-sustaining sustenance from the moment we are born. However, what if this nourishment came from a frightening "Wire Mother"?

In the 1950s, Harry Harlow conducted a series of well-known yet controversial experiments on monkeys at the University of Wisconsin, Madison, which significantly influenced our understanding of attachment. However, by today's ethical standards, Harlow's work would be widely deemed unacceptable. In one of his most famous experiments, Harlow separated newborn monkeys from their mothers and placed them in cages with two artificial mothers: one made of soft cloth that provided no nourishment and another made of cold wire that offered food. Surprisingly, the baby monkeys did not form a bond with the wire mother, despite it being their source of nourishment.

When Harlow and his team introduced a strange contraption to scare the baby monkeys, the monkeys sought comfort and clung to the soft and cuddly cloth mother, which had no practical function. This suggested that warmth and comfort were more crucial than food in fostering attachment. Harlow also constructed a rejecting mother that used pressurized air to push the baby monkeys away. Rather than seeking an alternative source of comfort, these monkeys clung even tighter to the rejecting mother than monkeys raised without rejecting mothers. This phenomenon is truly astonishing: the instinct for warmth and comfort in newborn creatures not only resists attempts to undermine it but is paradoxically reinforced by such attempts.

Eckhard Hess conducted a similar experiment with ducklings, using electric shocks to discourage them from following the object they were imprinted on. However, instead of deterring them, the shocks actually intensified their attachment and caused them to follow even more closely than before. The fact that attachment, love, and dependence can be enhanced by a "wire mother," a rejecting mother, or even electric shocks when attaching to one's mother may seem paradoxical. Yet paradoxes can offer valuable insights. As Oscar Wilde stated, "a paradox is the truth standing on its head to attract attention." In this case, what captures our attention is the impact of uncertainty.

In 1955, A.E. Fisher conducted an experiment on puppies, dividing them into three groups. The first group received kind treatment whenever they approached a researcher, the second group was punished for approaching researchers, and the third group experienced random alternating treatment of kindness and punishment. The puppies in the third group lived in a world of unpredictability, never knowing what to expect. Surprisingly, the study revealed that this third group developed the strongest attachment to the researchers and displayed the highest level of dependence on them. Guy Murchie referred to this phenomenon as the "Polarity Principle," suggesting that stress, including the mental stress caused by uncertainty, plays a role in attachment or love, and perhaps even contributes to manifestations of hatred as its polar opposite. Psychologically, uncertainty can lead to profound feelings of attachment and dependence.

In our lives, both positive and negative experiences often appear to be random and beyond our control. It is therefore not surprising that we often respond with unconditional love and acceptance when faced with an unfair existence. After all, what other choice do we have? We can relate to the puppies in the third group, seeking comfort and attachment despite the uncertainties. However, it is in our best interest to explore and understand uncertainty in order to make informed decisions.

Throughout the course of history, life has favored activities that help us transform uncertainty into knowledge. It is important to recognize that not every person we encounter is the ideal partner for us. This is precisely why a kiss, akin to a taste-test, becomes significant. If the choice of a partner were inconsequential, there would be no need for a kiss or a taste-test. The fact that kissing feels pleasurable and brings us immense joy is a testament to its role in selecting the most suitable mate.

Therefore, I encourage you to embrace the exploration of uncertainty and engage in the act of kissing. It symbolizes our pursuit of knowledge and the search for compatible partners. Thank you for taking the time to read this.