Where do all the Jokes Come From?

I came across an interesting science fiction short story Jokester, by Isaac Asimov in Isaac Asimov -- The Complete Short Stories, Volume I. In the story, a humongous computer -- the Multivac -- explains why jokes are funny.

I found the story interesting for another reason. In it, the central character, Grand Master Noel Meyerhof asks Multivac a question -- "Where do all the jokes come from?"

Meyerhof claims to know (and tell) thousands of jokes, yet he has never made up one. He has either heard or read the jokes and then merely repeated them. And he finds that none of his sources of hearing or reading have made up the jokes either. They, like him, have merely embellished the jokes and contributed by (re)telling them. He has never met anyone who has constructed a joke. He has, of course, met many who have made original puns but none of the puns provoke laughter. All puns either make you smile or groan but don't induce the same kind of laughter that a (unoriginal and retold) joke does. And so he wonders, who makes up the jokes?

Come to think of it -- I too haven't met any person who has claimed to have made a joke. Most of the jokes that I know are variations of a few very recognizable themes -- with only the setting and the characters changing in the retelling. A joke is always "a good one that I heard the other day" or "a funny email forward" or a "good SMS that was sent by a friend." Have you come across a person who has claimed to have constructed a totally original joke?

In the story, the Multivac studies many jokes for patterns, considers all the data and comes up with an answer.

An answer that has a catastrophic effect on humanity.

I am not revealing the answer. Get hold of Isaac Asimov's short stories and find out for yourself.

But, where do all the jokes come from? Do you know?