When the bones of prehistoric animals began to be discovered and scrutinized in the nineteenth century, there were those who said that the fossils had been placed in the rock by god, in order to test our faith. This cannot be disproved. Nor can my own pet theory that, from the patterns of behavior that are observable, we may infer a design that makes planet earth, all unknown to us, a prison colony and lunatic asylum that is employed as a dumping ground by far-off and superior civilizations. However, I was educated by Sir Karl Popper to believe that a theory that is unfalsifiable is to that extent a weak one.