Science of Discworld III: Darwin's Watch

The Science of Discworld III: Darwin's Watch (2005) is a book set on the Discworld, by Terry Pratchett, Ian Stewart and Jack Cohen. It is the sequel to The Science of Discworld and The Science of Discworld II: The Globe. According to Stewart:

As with the first two volumes, the book alternates between a Discworld story and a serious scientific discussion. The Science of Discworld series is arguably unique in style: we call it fact/fantasy fusion. The scenario allows serious discussion of solid, current science, without distorting it into 'yes, pigs really could fly given GM wings' or whatever. All three books entered the Sunday Times bestseller lists, and the third made it to number one, so we managed to reach a significantly large audience. Perhaps the most gratifying comment came from a Times reviewer: 'the hard science is as gripping as the fiction'. Which is just as it should be. The title refers to William Paley's watchmaker analogy and Richard Dawkins' subsequent description of evolution as the Blind Watchmaker.