The oldest joke historians have found is a 3,900-year-old fart joke

A Sumerian proverb dated to roughly 1900 BC reads: "Something which has never occurred since time immemorial: a young woman did not fart in her husband's lap." A 2008 University of Wolverhampton study, searching written records for the earliest jokes with a clear setup and punchline, crowned it the oldest on record, ahead of a 10th-century English riddle about a key.

— Paul McDonald, Research into the world's oldest recorded jokes — University of Wolverhampton, 2008