We looked at 168 cultures and found couples kissing in only 46 percent of them. Societies with distinct social classes are usually kissers; societies with fewer or no social classes, like hunter-gatherer communities, are usually not. For some, kissing seems unpleasant, unclean, or just plain weird. Kissing is clearly a culturally variable display of affection.
No one knows the exact origins of the romantic kiss. Some say it evolved to help test potential partners’ health through taste, their genetic compatibility through the smell of their immune system, or their romantic interest and sexual compatibility. Alternatively, it might have evolved from “kiss feeding” — the practice of a mother chewing up food and pushing it into her infant’s mouth with her tongue. The earliest known reference to kissing is in the Vedas, a 3,500-year-old Sanskrit scripture. Many classical societies, including the Romans, were passionate about kissing.
At least 90 percent of today’s cultures have kissing of one type or another, but the majority of it is parents kissing their children. Far less is known about patterns of who kisses romantically and who does not, and why.