The true test of the book, though, is whether or not it delivers on its more serious purpose. It does partly explain the origin of humour, but it also falls into the trap that evolutionary psychology so often sets for itself — that of seeking an all-encompassing explanation. Humour could be the resolution of non-threatening incongruity, and it probably is an advertisement of intelligence, but it is many other things besides. It undoubtedly is partly genetic, but it is also deeply cultural. And it is in culture that its real interest and complexity — and possibly its explanation — will surely be found.