Unfit for Purpose: When Human Evolution Collides with the Modern World

Though Hart (The Life of Poo), a biologist and science journalist, explains the goal for his rambling book clearly enough, the underlying evolutionary premise he offers is flawed. He notes that “this book is about mismatches between [humanity’s] evolutionary past and the environment we have created” but fails to mention what biologists understand very well: evolution never yields a perfect match between organisms and their environment. Hart devotes the bulk of the text to supposedly evolution-related problems such as stress, obesity, violence, addiction, and mental health issues, providing for each some brief biological background, a superficial analysis of current research, and a concluding note that the situation is too complex for any simple solution. At times, Hart’s comments come across as gratuitous and unfair, as when discussing geneticist James Neel, who proposed a “thrifty gene” that promoted fat and carbohydrates conservation in ancient hunter-gatherers. Hart begins by mentioning accusations—unrelated to his subject—that Neel deliberately initiated a measles epidemic among a group of indigenous people in the Amazon, only to acknowledge that the accusation was later fully discredited. The few kernels of insight presented in this scattered survey are not worth the work of winnowing them from the large amount of chaff. (Aug.)