If Richard Lewontin is right, we’re in for a big letdown when the Human Genome Project is completed. The promise used to justify the $3 billion effort is that the 3 billion base pairs in human DNA make up a “Book of Life” that will reveal the secrets of development, disease and everything in between. But as Lewontin points out in It Ain’t Necessarily So-a collection of nine extended pieces from The New York Review of Books-there are a few troublesome details scientists “forgot” to mention when they were lobbying for the project more than a decade ago.

For one thing, we have only the foggiest picture of how our 100,000 genes interact to regulate one another’s expression and to direct protein production. Extrapolating from the genome to the whole organism is therefore akin to writing a history of New York City based on the phone directory. Another problem is that DNA, by itself, doesn’t produce or explain anything. Genes specify which amino acids should be used to build a protein, but proteins themselves “are made by other proteins, and without that protein-forming machinery nothing can be made,” Lewontin observes. Life, in other words, is a co-production between DNA and its cellular surroundings, the choreography of which cannot be recorded solely in the genome.

Lewontin, a renowned geneticist and evolutionary biologist at Harvard, blames the Genome Project’s “fetishization” of DNA partly on the “evangelical enthusiasm” of prominent academic biologists with large personal financial stakes in the genomics industry, and partly on the gullibility of their journalistic “acolytes.” But he also sees it as a continuation of biology’s attempt since World War II to explain life in the same exact, mechanistic terms employed with such success by physicists earlier in the century. The problem is that where physics is neat and deterministic-“If you have seen one electron, you have seen them all,” as Steven Weinberg puts it-biology is messy and multithreaded.

Lewontin’s skillfully crafted reviews, which also cover books on evolution, embryology, sex research and cloning, say less about the books themselves than about Lewontin’s sharp-witted skepticism and humility about nature’s mysteries.”The truth is sometimes unavailable,” he cautions -something biology’s evangelists would do well to acknowledge.