Diagram of Beaks of Galapagos Finches by DarwinBy Jeremy Burgess

A classic illustration of evolutionary theory made by Charles Darwin in his book A Naturalists Voyage London The drawing shows the beaks of four species of finches found in the Galapagos Islands Darwin drew the conclusion that they all probably came from a common ancestor but had diversified and evolved to adapt to local food supplies on the different islands In his own words Seeing this gradation and diversity of structure in one small intimately related group of birds one might really fancy that from an original paucity of birds in this archipelago one species had been taken and modified for different ends