“…laughter is more often prompted by banal comments than amusing jokes. That makes it even more mysterious.” New Scientist August 2009.
Laughter, or something very similar, has been observed in various different species – including (but probably not limited to) chimpanzees, gorillas, bonobos, orangutans, rats, mice and dogs. Although it’s known that laughter can be induced by various situations, joy, play, relief, and humour etc - the biological function of laughter in humans (if there is one) is not known.
Note: One of the laughter inducing stimuli – humour – has its own academic journal. The International Journal of Humor Research