Good question! I think in most cases Western humour is derived from the Greeks (like most of Western culture). For example, a joke book by "Philogelos" (probably not his/her real name, since it means "lover of laughter", so is very appropriate for a joke-book author) from the early centuries AD can be seen to contain prototypes of many Western jokes: misunderstandings (or refusals to understand), clever tricks perpetrated on people in authority by people below them, and 'dirty jokes'. Similarly, puns have been around since at least the seventh century AD (a Pope, on seeing some pretty German barbarians, and being told that they were called 'Angli' said "non Angli sed Angeli", which means "not Angles but Angels" in Latin). However, many of these things are common to several cultures- the Middle Eastern/Central Asian jokes based on the character of Nasreddin Hoja share several characteristics with Western jokes, and are recognisably funny to a Western audience. In short, although 'Western humour' (that is, things that are funny to Westerners) probably derives from the Greeks, most humour is probably universal.