When the young naturalist Darwin set sail on a round the world expedition at the end of 1831, it was only with a vague notion that the relationships between all life forms, both present and extinct, were more complex than the Christian version of the world s creation purported them to be. During his five-year voyage of discovery on board HMS Beagle and more than two decades subsequently devoted to research, he painstakingly collected a mass of evidence from across the planet from Paraguay and th