So it is refreshing to see natural selection, the engine of evolution, characterized correctly as haphazard, without scruple, even ''abysmally stupid,'' especially when such blasphemies are loosed by as distinguished a scientist as George C. Williams. Williams, a professor emeritus of evolution and ecology at the State University of New York, Stony Brook, sees ''contrivances without contrivers,'' where organisms in every generation produce haphazard mutations that usually are deleterious but occasionally are advantageous. The pony fish of the title of Williams's new book refers to a small, almost transparent fish with an internal organ, known as a photophore, that generates light. Thus recent research suggests that morning sickness during pregnancy may be designed to alert women to otherwise tolerable toxins that could harm a developing fetus. Throughout this quietly tough-minded volume Williams makes clear that natural selection is a relentlessly effective force in shaping the survival of species.
Evolution never designs anything from scratch.
It can only tinker with whatever happens to be already there, saving those slight modifications that provide immediate benefits, culling those that cause harm. Williams has interesting things to say about body design, sexual reproduction and sexual differences, and old age. But general readers may find his remarks on the medical implications of adaptationist biology to be most provocative. Humans ''are in fact plagued with dysfunctional design features from head to toe,'' he says. We stumble from one slight evolutionary advantage to the next, with no more purposeful plan than surviving to the next generation.