The real origin of Darwin’s theory

Last week, snorkelling into a small bay on Chatham Island (San Cristobal), I looked up from watching a sea lion twist and turn underwater between a novelist and a neuroscientist to see a large man dressed in an incongruous overcoat standing with his back to us on a rocky outcrop. I wiped my goggles and realised I was looking at a statue. Of Darwin, naturally. Lots of other people visited these islands — Herman Melville, for one — and Darwin was just the captain’s companion on a small naval survey vessel, but it is Darwin everybody remembers. Bays, birds and bushes all bear his name.

The oddness of the Galapagos creatures cry out for his theory. Large lizards swim to graze on seaweed; tortoises have long necks and saddle-shaped carapaces on islands where they must eat taller vegetation; mocking birds have longer beaks on some islands than on others; tiny finches change beak shape during droughts through survival of the fittest.