The oldest "guy walks into a bar joke" is from Sumer, c. 1900 BC at youngest.
"A dog walked into a tavern and said, 'I can't see a thing. I'll open this one'."
Clearly we've lost the context of the joke that made it worth writing down, but it's fascinating that 4000 years later, we're still telling the same sorts of jokes that our ancient ancestors did.