What is the theme in The Last Continent: A Discworld Novel by Terry Pratchett?

Sex is an important theme in the story. Terry Pratchett's The Last Continent deals with Sex on two levels: biologically, as the agent of reproduction in plants and higher animals, and as the inspiration for sophomoric humor among celibate and repressed old men. The latter is given much more attention, because it fits the general tone of the novel and helps portray the characters involved.