Very Old Jokes

They were discussing old jokes on QI last night- and by old I mean very old- anything up to 4,000 years old. Jimmy Carr, who has just written a book about jokes and has been trawling the archives, offered us what he considers the oldest joke that still works. It's Greek, it's over 2,000 years old- and it goes like this:

Barber to customer: How would sir like his hair cut?

Customer to barber: In silence.