英语时差：笑话的来源及演变（下）

Some people, like comedians, actually sit down and invent jokes. But the neat thing is that most jokes come about without anyone inventing them. Philosopher of science Daniel Dennett uses jokes as an example of how evolution works. Let’s say the President does something embarrassing. Someone comments on it in a funny way. Someone else repeats the comment with an embellishment to make it funnier. Someone else turns it into “What does the President say when…?” And so on. Jokes evolve. This is why you run across so many jokes you’ve heard before, though you may not know it until the punchline. They’ve gone through so many changes you may not recognize them at all. Then suddenly you say “Oh, I’ve heard this.” What you actually heard was a kind of joke ancestor.