You might think it is a universal trait, something that we all do. But when European explorers travelled the world, they met tribes that didn't kiss. So is it a learnt response after all?

It can be as a greeting, or a sign of reverence or supplication- but we will be talking about the romantic kiss- face to face, lips to lips.

We examine the biochemistry, psychology, anthropology and history of kissing. Where does it come from?

Presented by Charlotte McDonald
Produced by Lizzy McNeill

More editions of The Why Factor are available on the BBC World Service website. Show less