Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines (review)

Each of us has dutifully learned an explanation of a physical or biological process—why the planets have their course, or how the phenotype of an anemic human is generated by the genotype responsible for his or her blood cells' development. The explanations sometimes are enough, sometimes not. Why and how is gravitation, we might ask. Why is it that DNA replicates? When have we reached an "explanation," and what counts as a convincing one? Shifting directly to one of the largest of these questions, author Keller explores explanations given for life itself, tracing the shifting elucidation of life in the last hundred years.

What counts as an explanation for life, not to say an adequate explanation, depends on the time and its needs, Keller establishes. This sounds tautological, but Keller's detailed review of the differing criteria for explanation is a story about the essential nature of scientific examination as it makes different analogies and calls on shifting metaphors from time to time. Life's explanation took on the model of mechanical simulacrum a century ago; today computers and artificial digital "life" appear to capture some essential nature of life, so we say. Keller establishes the link between, on the one hand, technological and other developments in the world at large and, on the other hand, the criteria of scientific explanation. She carefully traces the use of language and its not-so-hidden assumptions, the use of figures of speech and metaphors to provide the sense that a phenomenon has been identified and understood.

It is a convincing, thorough recitation, because Keller relies directly on the then-contemporaneous sources. By the same token, for those interested only in the epistemological and linguistic issues it can be slow going—there's more detailed history here of quaint, superseded theories than one might wish. But one cannot really argue with Keller's decision to let the old explainers speak for themselves. It is a powerful lesson to see that even in the last 100 years the very nature of scientific inquiry and its goals has shifted so profoundly. We may advance in our scientific understanding, to be sure, but we are also continuously changing the criteria by which such "advances" are measured. Even questions such as "what is life?" Keller notes, are not answerable absolutely (p. 294); these questions pose historical conundrums, and answers can never be better than good enough for the time.