Why Do Humans Kiss? A Valentine’s Day Investigation (Video)

Why Do Humans Kiss? A Valentine’s Day InvestigationKissing is an accepted human activity, seen as a sign of sincere affection, but why on earth do we do it? As Valentine’s Day looms, the festival for lovers, lips all over will be puckering up in anticipation of romantic attention. But why is kissing such a favored and favorite pastime?  Why do 90 percent of all humans engage in it?  Does science have the answer?

As it turns out: No. In The Science of Kissing: What Our Lips Are Telling Us, Sheril Kirshenbaum tells us, “ Scientists are not exactly sure why we kiss.” She deduces that “Perhaps kissing seems so commonplace that few of us have paused to reflect on its deeper significance.” As Valentine’s Day smoochers come together to kiss, they might pause to wonder what it is that they are doing.

Kirshenbaum has teamed up with Joe Hanson, the author of It’s Okay to Be Smart, to explore the subject.  In the resulting video, produced by PBS, Hanson comes straight out with it: Kissing is weird. He admits we love doing it, and damn, it feels good, but why do we want to rub our open mouths against each other’s? Is there a reason behind it? Valentine’s Day or not, is there any valid rationale behind this odd act?

Hanson does have some answers. As David Attenborough reminded us in the ground-breaking TV series, Life on Earth, our lips have evolved from–get ready for this–the primate’s butt.  As we became upright, our “lips” as flags to fertility appeared on our faces. Like our ape ancestors, our lips become more attractive if they are red and rosy.  Thus, the predilection among at least eight out of 1o women for painting their lips.  The eyes are then drawn to the lips, which is the precursor to kissing.

Five out of the 10 cranial nerves get engaged as a kiss commences, as well as a dozen facial muscles. One of these is the obiculus oris, the same muscle that makes babies mouths pucker up as they go for the nipple to nurse. The neurological satisfactions of the nursing infant as it bonds with the mother who is nursing is entirely the same as that experienced by a kisser.

During the act of kissing, oxytocin is released, which is a great feel-good relaxant. It is intensely pleasurable. Fascinatingly, most mothers, whether breast feeding or bottle feeding, hold their child to the left, and this is why, in later life, almost all of us tilt to the right when kissing.

But there is that troublesome nose problem. Noses do get in the way. In Vedic Sanskrit scriptures, Hanson tells us, there is a sound rationale for the involvement of the nasal regions. Smell is a big indicator of a potential partner; breath is a clue to a healthy mate. Many cultures still use noses for affectionate nuzzling, as an adjunct or even a substitute for kissing. In an experiment where women were asked to sniff T-shirts worn by males, they picked the ones where the man had a different immune system from their own. This is better for breeding; this is not the most romantic background to a Valentine’s day tryst, but hey, it is science.

Lips have more nerves than genitals do, and are highly wired to the pleasure and reward centers of the brain.  This means that a kiss can bring on a rush of dopamine equivalent to a hit of cocaine. The heart beats faster and blood is flushed with oxygen, which goes zooming to the brain. In the never-ending cascade of delight, this then releases endorphins.  All of that from just locking lips with someone, which is so much less effort than going for a run.  Just to add a satisfactory conclusion to the event, cortisol, the stress hormone, is reduced.  No wonder we like kissing–on Valentine’s Day and the rest of the year.

More people are said to remember their first kiss  more than they remember the activity that may have taken place after it. Kissing is somehow more intimate. In the Middle Ages, important contracts were sealed with the sign of a kiss, and many of us still do this inadvertently today, adding a cross to the ends of emails and texts.

Hanson concludes that kissing is a complex behavior, but there is still a lot left to learn about it. One thing is for sure–we are not about to stop doing it.

Other studies have affirmed that kissing is a test to vet future mates, and that women set more store by it than men do. Helen Fisher, author of Why Him, Why Her: Finding Real Love by Understanding Your Personality Type, and a professor at Rutgers University, said it is either a major escalation or a de-escalation point in mate selection.

Last year, Oxford University experimental psychologists, Rafael Wlodarski and Robin Dubar, ran an online survey on kissing. They deduced that kissing is a key determinant as to whether partners will carry on relationships or not. One of the funny things about kissing, researchers agree, is that while kissing can cause arousal, arousal is not what drives people to kiss in the first place.

Although chimpanzees and bonobos do kiss, they do not do it with anything like the same degree of lovestruck mooniness that homo sapiens do. Almost all humans do it, but almost no other animals. It remains somewhat of a mystery.

As Einstein opined, “Any man who can drive safely while kissing a pretty girl is simply not giving the kiss the attention it deserves.”

Humans love kissing, but why? Science has yet to reveal all. In the meantime, on Valentine’s Day, plenty of the human race will be testing out the theories.

By Kate Henderson


Huffington Post

3 Responses to "Why Do Humans Kiss? A Valentine’s Day Investigation (Video)"

  1. Marcia W.   February 14, 2014 at 3:41 pm

    This is a very heterocentric article and racist in tone.

  2. Kate Henderson   February 14, 2014 at 1:59 pm

    Thanks Chris, but aren’t pheromones odourless? Not to say that “following your nose” is not an excellent piece of advice.

  3. Chris Kempling   February 14, 2014 at 8:36 am

    The article didn’t mention one reason related to smell and mate selection. There are certain regions of the body which emit pheromones–the armpits, the areolas around the nipple, and the area of the cheeks next to the nose (which is where one’s nose is when kissing). Women noses are better equipped to discern appropriate mates, and a good long kiss helps them to decide. One caveat–women on birth control pills do not seem to have the same level of smell discernment, which may be a cause of later infertility problems or birth defects, because they end up with mates who are not genetically compatible. Before picking a mate, avoid the pill, give him a good long kiss, and follow your nose, not your heart;)


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