IT first happened more than a million years ago. Today people all over the globe do it at least once a day - and there's no sign of a let-up.
It is, of course, the kiss - the activity that adolescents around the world anticipate and agonise over, which film directors now dismiss as passe and which advertisers still use to sell anything from perfume to cooking oil.
For all the studies and research into the history of man, precious few facts are known about the kiss and where it came from.
No one, for example, actually knows where or when the first kiss was consummated.
If historians could single out one nation or even one region and prove that the kiss was first known in one place, then we could have a good clue as to how long smooching has been going on.
The trouble is that an enormous amount of national pride rests on the matter.