Endorphins! The source of the pleasure we get in a ripping guffaw! Yeah, well, so? And? Not much.
They do, however, own up to the fact that something acts as a catalyst to cause the hahaha (a homo sapiens upgrade to ape-like panting) with the release of the endorphins.
But, nah, sorry, they haven’t cracked what makes something funny yet 😉
Somehow I get the feeling that these guys have no sense of humor whatsoever.