Not all of us kiss. Some cultures today don’t even engage in kissing. Scientists suggest that this means kissing is not an innate or intuitive trait in humans. There are a few theories that explain the evolution of kissing.
The first possibility is that kissing became a learned behavior evolving from “kiss feeding.” This is the practice of mothers passing chewed food from mouth-to-mouth to feed their babies. Cultures today still engage in kiss feeding that is not social or erotic, for example some contemporary indigenous cultures.
The second possibility is that kissing is a type of grooming behavior that is culturally determined. Or that kissing (in the case of erotic of deep kissing) represents, substitutes, and complements intercourse.
Humans aren’t the only ones that kiss. Another one of the five great apes, Bonobos, frequently kiss each other to create social cohesion. Dogs and cats lick and nuzzle each other. These animals “kiss” to groom, smell, or communicate with each other, but this still implies and furthers trust and bonding.
Kissing is ancient, that’s for sure. Ancient Indian Vedic texts talk about kissing. There’s a whole chapter in the Kama Sutra that discusses modes of kissing (this book is from the 2nd century).
It’s possible that after Alexander the Great travelled to India in 326 BC, he learned about erotic kissing from the Indians and brought the technique back with him to ancient Greece. This doesn’t necessarily mean that kissing started in India; it’s possible kissing came even before the oral roots of the Vedic texts.
Kissing is mentioned in Homer, dating back to the 9th century BC, when King Priam pleads for the return of his son’s body by memorably kisses Achilles’ hand.
Kissing also marked rank and social order. Herodotus mentions that Persians greeted men of equal rank by kissing each other on the mouth and those of lower rank with a kiss on the cheek in his Histories, which date back to the 5th century BC.