A joke is anything said, written, or acted upon with the intention of being funny or amusing. It may use word play, sarcasm, irony, or a punch line to get a response. A practical joke, on the other hand, is something actively done physically to provoke a humorous situation. The purpose behind a joke can be to cause embarrassment, but more commonly it is to entertain, or garner attention.

Jokes have been entrenched in human culture the world over for millennia. It's actually believed by anthropologists and historians that the world's oldest joke dates from ancient Mesopotamia and was, perhaps not surprisingly, a fart joke. An ancient Greek document dating from circa 250 AD contains no less than two hundred and sixty jokes – and the nature of the humour enjoyed almost two thousand years ago is remarkably similar to that we find amusing today. Common themes from the time include jokes about eunuchs, people with halitosis or hernias, people who were bald, and the stereotypical absent minded professor.

But why do we laugh at jokes? Believe it or not, serious research by academics has gone into analysing and answering this question. Some studies and theories include:

• That laughter has evolved in order to make socialising more easily possible for humans.

• That laughter's function in the human brain is to provide a mechanism for the brain to learn nonsense. This theory seeks to explain why jokes heard repeatedly cease to be funny.

• That the intended reaction to a joke, that is laughter, is healthy – it releases endorphins (feel good chemicals) into the brain, and exercises the muscles of the abdomen.

• Contextual jokes, or "survival humour", can be a valuable survival mechanism during life's most difficult situations. For example, an amputee making jokes about his missing limb.

• There is a scientific suggestion that the human mind matches patterns, recognising anecdotes and organising them into a familiar connection. If a connection is disrupted, a new and unexpected link is made in the brain and we laugh as a physiological response when the new connection is made. This theory helps to explain why jokes are not so funny after the first time they are heard; why many jokes are elaborate and reiterate themselves before the punch line (for example, "There was an Englishman, an Irishman, and a Scot..."; why stereotypes feature so heavily in jokes (linking to expected stereotypical behaviour); and the reason why many jokes are actually variants of other well known stories.

There are certain elements in the telling of jokes and their reception which are almost universal: the sense of superiority felt over the subject of the joke; that of all animal jokes, those with ducks are the funniest (why are ducks so funny?); and the use of sensitive topics like illness, morality, and marriage.

Whether telling a funny joke, or using a gag gift from a joke shop, jokesters of today are simply following a long line of forebears – and let's face it, who doesn't love a good laugh?