The first English joke recorded was a dick joke. The oldest joke we know of is a Sumerian fart joke.
Madness string 4257
Even if your smile is objectively the dumbest-looking smile in the world, anyone who genuinely cares about you will be happy to see it regardless, because it shows that right now, in this moment, you're good. You're happy, amused, whatever, and that's not dumb at all.