The Beak of the Finch: A Story of Evolution in Our Time by Jonathan Weiner. Alfred A. Knopf. 332 pages. $25. Reviewed in the Raleigh News & Observer on August 7, 1994.

The News & Observer


August 7, 1994

Evolution in action


By: Phillip Manning

Nearly half the population of the United States does not believe in evolution. Many of the disbelievers are members of the religious right, and their anti-science bias worries many scientists, some of whom fear a 1990s replay of the Scopes trial. Since Charles Darwin's theory of evolution was published in London in 1859, creationists have continued to insist that it is merely a theory, and that the species were created at a particular moment of history.

Into this breach now step Peter and Rosemary Grant, who spent the last 20 years watching evolution occurring on a tiny island in the Galapagos -- the stomping grounds of Darwin himself. What they found will not be news to anyone who accepts Darwin's theory; but it will present problems for anyone believing in the Biblical version.

The Grants, of Princeton University, began monitoring the finches on Daphne Major, an extinct volcano near the center of the Galapagos archipelago in 1973, and they have continued to do so every year since. They, and a host of graduate students, have watched over 20 generations of finches, banding them and measuring their beak sizes, recording their songs and snapping their pictures. They know every finch on the island by sight, recognizing them as easily as the rest of us recognize the people who work in our offices.

The ground finches studied by the Grants, Geospiza fortis, eats seeds, and a seed-eating finch's most important survival tool is its beak. The size of the beak determines how hard a seed a bird can crack. When an especially rainy year produced an abundance of small, soft seeds on Daphne major, the Grants' careful measurements showed that the next generation of finches had smaller beaks. When a severe drought reduced the finches to eating larger, tougher seeds, the fortis population on the island plummeted from 1,200 to 180, and the beaks of the next generation were larger than those of the previous one. This is natural selection in action.

It is true that the increase in average beak size was a mere half-millimeter. It is also true that the Grants' have not observed the creation of a new species, though the drought took fortis beaks a quarter of the way to the size of a larger species of finch that also lives in the Galapagos. There is little doubt, though, that the Grants' measurements over time show vividly how natural selection and its inevitable result, evolution, work in the wild.

To broaden the book's scope, Weiner ranges beyond the Grants' work to tell how E. coli, the most common bacteria in the human gut, can evolve in a single day to resist an antibiotic; how the gonorrhea bacterium is changing and becoming more resistant to penicillin; and how the slaughter of elephants with big tusks is producing more tuskless elephants.

Despite an occasional tendency to overwrite (one passage has an ocean "1,000 fathoms of sharks" deep), Weiner, formerly an editor for "The Sciences" and the author of two previous books, has produced a smoothly moving, meticulously researched book.

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