jokes

I often think that Isaac Asimov was on to something in one of his short stories (I forget which one right now) that proposed that jokes were an alien experiment to work out the personalities of Humans. I find it difficult to understand how it could be anything else by the amount of repetition in jokes. I just received yet ANOTHER joke that I originally got about 5 years ago but that once again seems to be making the rounds. Now that is not particularly unusual, which says something in of itself, but what is unusual is that half the recipients are the same people as well...