It is a saying of the Sumerians, who lived in what is now
southern Iraq and goes: "Something which has never occurred
since time immemorial; a young woman did not fart in her
husband's lap."
A 1600 BC gag about a pharaoh, said to be King Snofru,
comes second -- "How do you entertain a bored pharaoh? You sail
a boatload of young women dressed only in fishing nets down the
Nile and urge the pharaoh to go catch a fish."
The oldest British joke dates back to the 10th Century and
reveals the bawdy face of the Anglo-Saxons -- "What hangs at a
man's thigh and wants to poke the hole that it's often poked
before? Answer: A key."
"Jokes have varied over the years, with some taking the
question and answer format while others are witty proverbs or
riddles,"
"What they all share however, is a willingness to deal with
taboos and a degree of rebellion. Modern puns, Essex girl jokes
and toilet humor can all be traced back to the very earliest
jokes identified in this research."