It must have been some brave ancestor who thought, "Well, if we've already hugged, why not try pressing our lips to someone else's face?" Maybe it was just a trial kiss at first, and then, looking at the other person's reaction, they realized, "Oh, it works!"
Someone thought it was just funny, someone saw some special magic in it, and somehow, one by one, we came to the point where kissing has become the norm. But in any case, think about it: a kiss is, essentially, contact with someone else's saliva. And this contact has become such a cultural and romantic gesture that now we expect it on dates, in movies, in novels, and if it doesn’t happen, it’s as if the date never happened! It’s hard to believe that someone dared to start all this, but apparently, it was the one who wasn’t afraid to be the first to reach for someone else’s lips who became a real prophet in the field of personal relationships.