Well I guess it shouldn't be that much of a surprise that that world's oldest joe turned out to be a joke about flatulence but the big surprise is that the joke came from an old Sumerian proverb dating back to 1000BC in what is now southern Iraq.
So you're wondeirng what the joke is? well here it is:
"Something which has never occurred since time immemorial; a young woman did not fart in her husband's lap,"
and check out some of the wonderful fart jokes the late, great, George Carlin left us below:
"Time for some fart jokes"
(what Carlin thought should be done to the Taliban days after the September 11th attacks)
and a bit on pusy farts: