THE BEAK OF THE FINCH by...

THE BEAK OF THE FINCH by Jonathan Weiner (Vintage: $13; 332 pp., illustrated). Darwin’s observations of the Galapagos finches helped inspire his theory of evolution. In this Pulitzer and L.A. Times prize-winning study, Weiner reveals how the incremental changes that occur between generations of finches demonstrate natural selection. A difference of a single millimeter in the depth of a bird’s beak can affect its ability to crack tough seeds: A finch with a larger beak may survive a drought while its smaller cousins starve. Discussions with prominent ornithologists make it clear that the finches--and all plants and animals--continue to evolve in response to environmental and sexual pressures: “It is as if each living thing on earth is holding on at the very shore of an ocean, in rough and invisible seas, swaying in place as each wave shoves it toward shore and then tottering as the broken surf drags it back again.” Female finches favor larger males, but the scant food supply on the desert islands limits the size a bird can attain. Weiner also notes that the overuse of chemical pesticides is causing insects to evolve at an unprecedented rate in the American South--where opposition to teaching evolution remains strong.