Why do we laugh?

You ask: Why we laugh?

Caveman brain always guess what come next. Then thing jump sideways — safe surprise, no real danger — and brain let out a bark: ha-ha-ha! Laugh start long ago as a play-sound, like young ape kin make when they tussle, to say 'this fight only game, we still friend'. So Caveman laugh most with tribe — near thirty times more than when alone in cave. Laugh flood brain with feel-good stuff, wash out worry, and glue the tribe tight. Tickle work bit different — body jump at surprise touch it cannot make on self. Science tribe still poke at the full why. Cave wisdom: laugh not just for funny thing — laugh is Caveman way to shout 'we safe, we together' without needing any word.