The rise of evolutionary biology - How did Darwin form his ideas?
Darwin on The Beagle
Charles Darwin, after graduating from Cambridge, had traveled the world as a naturalist on board the Beagle (1832 - 1837). As he collected birds from the Galapagos Islands, he realized that they varied from island to island. He had initially supposed that the Galapagos finches were all one species, but it now became clear that each island had its own distinct species. How easy to imagine that they had evolved from a common ancestral finch!
It was probably these observations of geographic variation that first led Darwin to accept that species can change.
The image opposite is of Geospiza fortis, one of the famous Galapagos finches studied by Darwin.