A man bought a slave who died soon after. When he complained, the slave seller replied: "Well, he didn't die when I owned him." Fast forward 1,800 years and the ideas behind many modern jokes can be traced back to the basic principles instigated by the Romans. In fact, take a trip on a cruise ship and you'll hear the resident entertainer still telling many of the original gags. Meanwhile new jokes are constantly evolving. The cult of celebrity has brought about numerous jokes at the expense of t…