Less than half of all societies kiss with their lips, according to a study of 168 cultures from around the world. William Jankowiak, a professor of anthropology at the University of Nevada Las Vegas, found that only 46% use lip-kissing in a romantic sense, excluding parent-child greetings or kisses.

Two theories as to why people need to kiss stem from the idea that as babies, we have an innate desire to touch our lips. In one case, it may be the fact that we associate touching the lips with breastfeeding and this reflex is innate in everyone. There is also a suggestion that mothers and their children associate lip-to-lip kissing because of something called "pre-mastication food transfer *". The mothers of our ancient ancestors may have chewed our food for us in the first years of life and transferred the food directly to our mouth. This is something that is seen in our nearest ancestors - chimpanzees - as well as other great apes.

* Pre-mastication: A term used when chewing food with the intention of softening it or breaking it into small pieces to feed the baby.

Jankowiak, however, thinks that "people's sensuality can be fulfilled in many ways, apart from kissing." 

"Those cultures that do not kiss on the lips find other ways to be intimate. For example, in the 'Malaysian kiss' described by Darwin, women sat on the ground and men hung on them and sniffed each other - getting one." sample "of their partner 's fragrance.

In the Trobriand Islands, off the east coast of New Guinea, lovers kiss while sitting face to face and biting each other's eyelashes.

The normal lip kiss we know today is an almost unique human behavior. If it has an evolutionary purpose, why not see more animals kissing?

One of the reasons we may have been "forced" to approach our partner's face has been to smell him. Aroma can reveal all kinds of useful information: diet, the presence of diseases, mood, etc. Many animals have much more sophisticated sense of smell than we do, so they should not be so close.

Source: BCC