So let's play "Stacked Assumptions", shall we?
First of all, name some things, off the top of your head, that separate man from the common animule.
WELL, HUMANS HAVE SELF-AWARENESS. THEY DEVELOP CULTURES AND SOCIETAL BONDS. THEY ARE AWARE OF THEIR OWN MORTALITY. THEY MAKE AND USE TOOLS... COMPLEX ONES. THEY HAVE LANGUAGE.
So what if I told you that, given these basic assumptions, I can prove to you that, for a variety of reasons, [sense of humor is the best measurement of self-awareness]?
PULL THE OTHER ONE.
No, it's true. First of all... what is a joke?
How about this: I'll summarize, and you tell me if I'm off-base or not. Okay?
A joke is something that requires the listener to understand many things. The rules and tendencies of his world. The attitudes and prevalences of his people. Historical references. Philosophical references. Even a knowledge of the references of humor itself. For instance, what is the stereotypical "First Joke"?
WHY DID THE CHICKEN CROSS THE ROAD?
Right. And do you know why that is considered the simplest type of joke?
BECAUSE IT'S SO STUPID?
No. And not because it's been told so many times, either. It's the simplest joke in the world because it makes the listener do all the work.
If I ask you why a person is crossing the road, you're going to want more information, right? You'll want to know what the person does for a living, or what kind of neighborhood he or she is in, or what time of day it is. But this is a joke, and one of the rules of a "joke" is that I get to tell the set-up, and then you say "I don't know", and then I tell you the punchline.
THAT'S THE PROCEDURE.
So you don't get to have any additional information about this guy. Let alone the fact that it isn't a person, it's a chicken. Chickens don't do any of the traditional person stuff. So why do we even assume that this chicken would have anything resembling a homo sapien agenda?
BECAUSE IT'S A JOKE. ANIMALS DO ALL SORTS OF THINGS IN A JOKE.
So jokes also involve the suspension of disbelief.
RIGHT. THEY'RE LIKE LITTLE STORIES.
Right. They aren't necessarily moral lessons, they aren't necessarily rational. They're just unexpected in some way or another. They establish a situation using a combination of story elements, weave an unusual, complex, or emotionally-laden situation (logically known as the "set-up"), and then toss you a curve ball at the last minute. It'd be frightening if it weren't just a collection of phonemes. This, by the way, is why some people don't like jokes.
THEY DON'T LIKE SUPRISES?
Exactly. They don't like not knowing. They don't like being made to play the fool. Anyway, let's get back to the chicken. Whether we like it or not, this old chestnut relies on the premise that the listener has heard enough jokes to be familiar with the convention of unexpectedness that we've just discussed, but hasn't heard THIS ONE yet. So the listener, upon hearing the set-up, begins to try and analyze the joke. And what's the only specific piece of data he or she has?
IT'S A CHICKEN.
Right. And we know all about chickens. They're stupid, they live in barns, they make good eatin. They have chicks, they lay eggs, they cluck and look silly. All this, and far more specific data that the individual listener might have. This all gets pulled from the long-term memory banks and into the "Immediate Use" stack. The listener is getting all geared up for a pun, or a political or cultural reference, or something involving the fact that the joke-teller has bothered to make it a chicken, as opposed to a person. And, because the question sounds to be in the form of a joke, and therefore is assumed to BE a joke, the listener throws away the one answer he really needs.
THE OBVIOUS ONE.
Right. And when the speaker drops the bomb, so to speak, the listener feels completely betrayed. The obvious, logical, correct answer isn't supposed to be the right answer.
SO LAUGHTER IS A RESPONSE OF EMBARASSMENT?
Pretty much. You laugh because you now know what you didn't know before. And because the joke-teller isn't an actual threat to your status. It's like sparring. That's why, when one person tells a joke, everyone else tries to join in. To regain status. If the situation calls for the audience to _not_ join in, it means that the joke-teller has some form of status over the audience. Really good joke-tellers can do this whether the situation is an audience-based one or not.
GET ON WITH IT.
In short, a conversation requires local knowledge. A story requires local knowledge and global information. A joke requires local knowledge, global information, knowledge of human nature and one more thing. Self-awareness.
SELF-AWARENESS. BECAUSE ONE MUST BE AWARE OF ONE'S OWN REACTION TO THE JOKE?
Because if a person isn't being aware of the other person, and of themselves, then they will meet every joke with a "Uh huh." Some people do this. To them, it's just a story. It's just an anecdote. Logic puzzles like "A man is hanging from the ceiling... dead. A puddle of water lies under him. How did he die?" require logical thought. Jokes require not only logical thought, but a willingness to throw away any logical premises that won't help solve the joke and keep any that will.
YOU MAKE JOKES SOUND INCREDIBLY COMPLEX.
You got it. The fact that people can share in something as complex as humor is a fucking miracle of evolution.