The Beak of the Finch

The Beak of the Finch: A Story of Evolution in Our Time (ISBN 0-679-40003-6) is a Pulitzer Prize winning book on evolutionary biology written for the layperson by Jonathan Weiner in 1994. The finches of the title are the Galapagos or 'Darwin's Finches,' passerine songbirds in the Galapagos Islands. The adaptations of their numerous species, in three genera, exploiting several ecological niches in the rugged and dry Galápagos Islands provided evidence to Charles Darwin that “species are not immutable.”

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The author Jonathan Weiner follows the career of two biologists, Peter and Rosemary Grant, who have spent twenty years proving that Charles Darwin did not know the full strength of his theory of evolution. On a desert island among the Galapagos, Daphne Major, the Grants are showing that among the finches of the Galapagos, natural selection sometimes takes place so rapidly we can watch it at work.

Darwin's finches are 13 different closely related species of finches Charles Darwin discovered on the Galapagos Islands. Darwin's voyage on the HMS Beagle, and the finches in particular, are known to have influenced his thinking so that he would later produce a basic theory of evolution by natural selection. Darwin reasoned that there had to be a common ancestor. Later, extensive research was done by Peter and Rosemary Grant. The birds are all about the same size (10–20 cm). They mainly differ in the form of the beak. The beak is adapted to the food they eat. The birds are all brownish or black. They have short rounded wings and a rounded tail that often appears cocked to one side. Most male finch mature to a solid black color, while the females mature to a drab grayish color. Exceptions are made for the Vegetarian and Tree Finches the males never become completely black rather they have a black head, neck and upper breast. Warbler, Woodpecker and Mangrove Finches have more of an olive color.

In the conclusion the author relates the speed of evolution to the growing resistance of insects to insecticides and of bacteria to penicillin and related anti-bacterial drugs.