Before Watson and Crick described the gene as a sequence of DNA, visualized as a succession of letters—like a line of computer code—terms such as information would have been nonsensical. Genes had been imagined as beads strung along the chromosomes. They didn’t “encode” anything; they simply carried traits. The term gene wasn’t coined until 1909. Before the turn of the 20th century, Mendel’s elemente were not thought of as physical things. They were mere abstractions. Saying that Darwin lacked the concept of information is like pointing out that T. rex lacked an iPhone.

If Mukherjee had actually read the reference to Mendel he cites from Darwin’s bookshelf, he would have seen that it discussed hybrids and pollination. It gave not a clue to what would later be called Mendel’s laws of heredity. Moreover, Darwin understood his own theory perfectly: It assumes that heritable variation occurs, but it does not depend on knowing where that variation comes from.

This handful of errors, drawn from a sackful of options, illustrates a larger point. The Whig interpretation of genetics is not merely ahistorical, it’s anti-scientific. If Copernicus displaced the Earth from the center of the universe and Darwin displaced humanity from the pinnacle of the organic world, a Whig history of the gene puts a kind of god back into our explanation of nature. It turns the gene into an eternal, essential thing awaiting elucidation by humans, instead of a living idea with ancestors, a development and maturation—and perhaps ultimately a death.

There is a subtler gene, and Mukherjee acknowledges it when he doffs his history hat and dons his white coat. Over the past three decades, the rise of genomics—the move from studying single genes to analyzing and comparing whole genomes—has led to a newly sophisticated understanding of how our DNA influences disease and behavior. As a clinician, Mukherjee grasps this complexity. He understands the humanitarian cost of essentializing the gene. “Genes cannot tell us how to categorize or comprehend human diversity,” he writes. “Environments can, cultures can, geographies can, histories can.” He has well-justified qualms about scientific hubris, about technology getting ahead of ethics. He details with due solemnity and reflection the recklessness of early gene therapy. Its few successes, he takes care to note, were overshadowed by tragedies such as the case of Jesse Gelsinger in 1999. When Gelsinger, a teenager from Arizona with a rare disorder, was injected with a modified virus carrying a supposedly corrective gene, a cascade of unintended consequences was triggered. His organs shut down and he died.

Mukherjee writes eloquently about the limitations of medical genetics. Thus far, he observes, scientists have compiled an impressive (if incomplete) “backward catalog” of gene function: Given a person with a set of symptoms, what gene variants does one tend to find? But clinical genetics needs a forward catalog: “If a child has a mutant gene, what are the chances that he or she will develop the syndrome?” In many cases, he notes, such a catalog may be unattainable. Genetic tests for complex diseases such as schizophrenia or autism are unlikely to be very predictive. As Bryna Siegel, an autism expert at the University of California at San Francisco, has put it, genetic counselors may have to say, “Mrs. Smith, here are the results of your amnio. There’s a one-in-10 chance that you’ll have an autistic child, or the next Bill Gates. Would you like to have an abortion?”