Spit Swapping!

Why do humans kiss? If one really thinks about it, kissing is a pretty bizarre and gross action! Just as how it is sometimes described in narratives, kissing involves some heavy spit swapping and it is estimated that “hundreds or even millions of bacterial colonies move from one mouth to anther during a kiss.”

Most people if asked such a question, would probable answer that humans (Homo sapiens) kiss simply because it feels good. Well, yes, it does but scientists (philimatologists) who study the evolutionary history of kissing will probably not be satisfied with just that answer. Thus far, while there has been no conclusive reason as to why people perform this act of saliva trading, it is believed that kissing is a behavior that is both instinctive and learned.

Tigers kissing

For those who deem kissing to be part of our nature, other animals have been cited in support of this behavior. One of the most concrete proofs is from that of the Bonobos ape, the most human-like of all apes, which have been observed to kiss each other to offer comfort, to make up after fights and sometimes, for no seemingly special reason at all.

Then there are others who support the idea that kissing is learned rather than instinctual because it is a fact that not all human beings actually engage in acts of kissing – certain tribal groups in the world doesn’t and for those who do, kissing was first observed as an act carried out by mothers to pass chewed food to their newborn, toothless infants.

Today, a generally accepted theory as to why humans kiss is that as people move their faces close together, our noses are subconsciously sniffing each other out and our pheromones would exchange biological information in order to determine the suitability of each other in becoming mates to produce a stronger offspring. It seems that people prefer someone whose scent “tells” us that his/her genes have certain immune system proteins that are different from our own thus a union of these two sets of genes could possibly bear an offspring whose immunity would be even stronger. Still – scientific reasoning aside, I’m one of those believer that with the tones of nerves present on our tongues and lips, kissing is simply a pleasure that we get just we try delicious food so who cares really why humans kiss?


Scienceline.org (2006, October 2). “Why do humans kiss?”. Retrieved March 28, 2010, from http://www.scienceline.org/2006/10/02/ask-fiore-kiss/

The Bonobo Page. (2006, April 26). “Bonobo”. Retrieved March 30, 2010, from http://williamcalvin.com/teaching/bonobo.htm”Tiger-kiss,” by tomjude. Stock xchng: iStockPhoto.com. URL: http://www.howstuffworks.com/framed.htm?parent=kissing.htm&url=http://www.sxc.hu/photo/531160 (accessed on 29 Mar 2010)