My thought exactly. Humour is a way to validate assumptions about other people. It is a way to probe them in search of common hermeneutical grounds. If we can laugh together and eat the same things, then chances are we can also have a constructive relationship together. I think its main evolutionary purpose is the production of pleasant shared experiences, to add positive feelings to the memories of others - and others' memories of us. I have a better chance of our relationship being beneficial to me if you remember laughing every time you see me. And if I can make a lot of people laugh on the regular, then I stand a better chance of building beneficial relationships with my peers than those who can't, thus increasing my chances of survival.

I believe humour is one of those evolutionary attractors, a sort of inevitable side-effect of the coexistence of communication and play. Obviously it has been rendered way more complex and nuanced through our development of language and all our social rituals, but most animals we regard as highly intelligent seem capable of both play and humour. They are both ways of testing different behaviours in safe contexts, as well as ways of getting to know other individuals. Humour lets me simultaneously play with a social situation (thus learning about its intricacies and trying new things), produce a pleasant memory of me in the other's mind (thus increasing my chances of building a beneficial relationship with them) and probe them to garner information on their culture, idiosyncrasies and reputation (thus making my relationship with them potentially safer).

These three direct benefits of humour are reason enough for this behaviour to have taken evolutionary roots. Starting from there, the behaviour has evolved through culture, like many other social behaviours, to become a sort of fractalized version (or, more exactly, versions) of itself. Now, humour feeds on itself ad infinitum into ever more incongruous and bizarre regressions. That's how we get memes that are surreal versions of sarcastic memes, that were themselves parodies of other popular memes laughing at completely ordinary real world situations.