Even today, some cultures shun kissing. In China and Japan, doing it in public is taboo. An article published in the Chinese Worker's Daily newspaper a decade ago admonished young people for adopting Western kissing practices, declaring that kissing is indeed a harmful form of behaviour. Despite such words of warning, many young people of these cultures have started to embrace the snog under the pervasive influence of Western culture in the media. But if kissing is learned and not innate, then somebody, somewhere must have started smooching, and then convinced a whole load of other people to take it up too.
Theories abound as to the origins of kissing.
Some think it dates back millions of years, and started when women chewed up pieces of food and passed them directly from their lips to their babies' mouths. Kissing might have signalled affection between mother and child after these food exchanges ended. If our ancient human ancestors did kiss, they were coy about depicting it in their art and writing. One of the earliest references comes from India and dates from around 1500 BC when the Vedic Sanskrit texts were written down from oral history. These describe the custom of rubbing and pressing noses together, says Bryant.