THE TRIPLE HELIX.

By Richard Lewontin. Harvard Univ. Press. 136 pp. $22.95

At least since Descartes described the visible world as "merely a machine in which there was nothing at all to consider except the shapes and motions of its parts," metaphor has played a central role in scientific understanding. We think of our brains as computers, or we refer to the human genome as the master blueprint for the species. Lewontin, a professor of evolution and zoology at Harvard University, contends that metaphors can mislead as well as enlighten. While conceding that scientific explanations "necessarily involve the use of metaphorical language," he argues that many common terms have outlived their usefulness, especially in the realm of evolution.

To begin with, he finds fault with use of the word development to describe how an organism changes over time. In photography, "the image is already immanent in the exposed film, and the process of development simply makes this latent image apparent." Some biologists believe that organisms change in a similarly preordained fashion: Genes determine the outcome, while environment, like photographic developer, provides nothing more than "a set of enabling conditions that allow the genes to express themselves." Scientists who discount the role of environment in this fashion, he contends, are guilty of "bad biology."

Darwin’s notion of adaptation does account for the influence of environment, but Lewontin believes that it too constitutes "an impediment to a real understanding of evolutionary processes." The term implies that the organism adapts to a fixed world—that the organism is the variable and the environment is the constant—whereas the two actually affect each other. Humans, for example, produce a "microclimate": a layer of higher-density air, warm and moist, that surrounds the body and rises slowly upward. "This heat layer is the self-produced shell that constitutes the immediate space within which the organism is operating." The body thus helps create its own external environment.

In place of the flawed images that prevail, Lewontin proposes the metaphor of the triple helix—signifying gene, organism, and environment, all interrelated and interacting. A modest proposal, perhaps, but one that he believes could make a marked difference in scientific inquiry: Progress "depends not on revolutionary new conceptualizations, but on the creation of new methodologies that make questions answerable in practice in a world of finite resources." In this deft blend of biology and literary theory, Lewontin makes a compelling case that scientific metaphors, like scientific theories themselves, must be subjected to rigorous, unremitting re-evaluation.

—Jennifer A. Dowdell