During his momentous voyage aboard HMS Beagle, Charles Darwin made a series of observations that led him seriously to question, for the first time, the literal truth of the Bible. Like most people, he had accepted Archbishop Ussher's calculation of 4004BC as the date of the world's creation. He was familiar with Lamarck's theory of evolution, but dismissed it as blasphemous nonsense.

The Galapagos Islands were to provide the most illuminating experience of that long voyage. Each island, though only 50-odd miles from its neighbours, had its own species: 'This appears to be one of those admirable provisions of Infinite Wisdom by which each created thing is adapted to the place for which it was intended.'