Many animals have a concept of “play.” At times and places where they feel safe, friendly associates practice important motions, like chasing or fighting, but try to avoid any big effects – they retract their claws, pull their punches, etc. Play is an important way for young animals to learn how to act like old ones. Humans retain youthful styles longer into life, and so we play all through life.
Humans also developed language, which enabled stronger social rules about forbidden behaviors. For example, not only are you not supposed to kill associates, you are supposed to punish those who do kill, and those who refuse to punish killers, etc. Language let humans tell others about rule violations, to recruit a wider circle of enforcers than just direct witnesses.
Humans also tend to have rules about what you shouldn’t say. For example, foragers not only forbid domination, at least between families, they also forbid talk that supports domination. So foragers are typically not supposed to brag, threaten, or give orders. The more ancient concept of play, however, let humans evade such rules on forbidden talk. Let me explain.
Just as there is play chasing, play fighting, or even play mating, there is also play talk. Like other kinds of play, play talk only makes sense among friendly associates, when they are in a relaxed and unthreatened mood. Play talk should take the general forms of regular talk, but with claws retracted, punches pulled, etc., and everyone acting relaxed and unthreatened. Play talk should not be directly on serious topics with large important consequences, where people get stressed or angry.
With a little indirection, however, even play talk can communicate on serious important topics. For example, while social rules might forbid directly propositioning others for sex, people often communicate an interest in sex by joking about it in the right way. As long as there are other plausible interpretations of their words and actions, it can be hard for others to accuse them of violating the social rules.
It is easier to use play talk to evade talk rules if groups develop a very local culture and language – particular words and associations that have particular meanings due to the local history. This makes it harder to clearly convince outsiders that something illicit was communicated. It can also be easier to use this trick at the expense of folks who are eager to show their loyalty to the local group – publicly accusing another group member of violating talk rules ends the play mode and risks seeming less friendly to the group, especially if the local group isn’t very vested in that particular rule. Finally, it is easier for smarter people to talk indirectly so that they understand each other, but outsiders do not (achieve common knowledge that they) understand.
Humans thus developed sophisticated capacities for using play talk to indirectly communicate on serious topics. We became very adept at and fond of playfully talking on two levels at once, especially when the more hidden level talks about or embodies rule violations. We are so fond of this sort of activity and ability, in fact, that we often consider a surplus of it the main reason we like or love someone, and a deficit of it almost a definition of being inhuman. And such rule-evading abilities were so important that we developed ginormous brains to support them.
I am talking of course about humor, and sense of humor. We cherish our friends and lovers for making us laugh, and we think inhuman robots and despots couldn’t have a good sense of humor. We not only playfully talk illicitly via humor, we also play at humor, practicing this general capacity through endless variations of stories where a hidden often-rule-violating meaning is just barely revealed to wise listeners. Homo hypocritus hones humor. This is who we are.