Well, a popular theory believed by Philematologists (people who study the science or art of kissing) is that in the pre-historic times mothers used to perform a process called kiss-feeding where mothers would chew food and pass the chewed food to their toothless babies as they couldn’t chew themselves and even the saliva of the adult pre-digests the food making it easily digestible for the baby. Gross isn’t it? Well, in an era oblivious to the modern DIY guides, advanced technologies, etc, survival was a day to day activity.

Studies have also revealed that a kiss could help a person in finding a suitable mate. If you are attracted to someone, after kissing the attraction might grow or in certain situations fade out. Kissing releases adrenaline, dopamine, oxytocin and serotonim that in turn provide a sensation of pleasure, trust, attachment and awesomeness. It transmits sensory signals on a subconscious level that may even carry information about the kisser’s personality. This exchange is most likely facilitated by pheromones which are chemical signals passed between animals to help send messages.

This theory gives rise to another one as it suggests that the pre-historic or primal people used kissing as a strategy for mate selection. They enjoyed kissing and probably did it more often and may have even made better decisions in choosing their mates via kissing. This practice of kissing so often for mate selection gave birth to a generation i.e. “us”, people who enjoy kissing, a sort of a genetic code may have got embedded within us as our ancestors kissed so often. Still, this all is only a theory as there are no books or a source of literature that provides information regarding the action of kissing although they explicitly depict the action as it was and still is a common action of touching lips of two human beings to show love or greeting.