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The Beak of the Finch: A Story of Evolution
in Our Time |
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| (Illus.) Alfred A. Knopf Inc. 1994 x+332pp. 0-679-40003-6 Index C, T, GA ** |
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Recent polls suggest that approximately 50% of Americans do not believe in evolution. Most
people, even trained scientists, would refer to evolution as the "theory" of
evolution. Darwin never used the word "evolution" in The Origin of Species. All
of this can be explained by the understanding that the process takes place over a long
period of time and cannot be observed or tested. Evolution must be believed by logic
alone. This book clearly and elegantly shows the modern-day reality of the visible action
of evolution as observable fact. The text is based on numerous scientific publications by
professors Peter and Rosemary Grant and their associates. Weiner takes us through the
steps of these two researchers in over a decade of daily observations and measurements on
perhaps the most famous birds in the world, Darwin's finches. Darwin himself was the first
to describe and marvel over this diverse, yet similar, group of closely related birds that
inhabit the Galapagos Islands in a patchwork of species and adaptations. Darwin was also
the first to note how seemingly minute variations in the beaks of different species
coincided with very different behaviors and distributions on the islands. The Grants have
taken Darwin's and others' observations many steps further. They began by taking dozens of
measurements on every bird on one island of the Galapagos (Daphne Major) and following
every individual and every one of its progeny through a decade that included both a major
drought and a veritable flood: climatic extremes. What they found first was that the
population of various finches on Daphne Major are not static. The seasonal differences
swing wildly about and are directly related to changes in rainfall, food availability, and
other factors. Detailed studies show that seemingly minute differences of only a single
millimeter in the depth of a finch's beak can strongly influence that bird's survival,
breeding potential, and contribution to the gene pool. The researchers were able to
observe conditions that favored both greater separation of species (i.e., greater
distinction) and the fusion of species (when conditions favor the survival of hybrids).
And, unlike Darwin's wildest dreams, the Grants actually measured factors that might
easily suggest the origin of new species. Their students who were working with blood
samples were able to pinpoint DNA chains that corresponded with changes in the birds'
structure and changes in climate. At high noon, the sun is so bright we cannot see the
stars, but they are always there. And so it is with evolution, it is always moving and
changing the players in each species even if very slowly, but it is there and it can be
seen and measured. Today, the prime agents of change are humans, and our selection
pressure on a wide range of plants and animals may unalterably force this world into a new
phase of evolution. The author relates all of these factors to the readers through various
other examples of plants, animals, and humans in a highly readable manner.
--Reviewed by James W. Waddick in Science Books and Films, 30/9 (December 1994), pp. 263-4.
