The Fly in the DNA

In San Francisco I once knew a woman who had been adopted as a baby. When first I met her she hadn’t seen her mother since the day she was born, and had never met her father or any other blood relative. When she was twenty-one years old, she managed, somehow, to track down her mother, who was then living in central California with a man, not her father, and four other children. My friend wrote to the family and was invited to visit them in their large, noisy house on the outskirts of a large town. On the day she arrived she stayed up talking late into the night. Finally everyone went to bed. But at around three in the morning my friend woke up. She often got hungry in the middle of the night, and was in the habit of making plain spaghetti at two or three in the morning. She decided to go down to the kitchen to see what was there. To her astonishment, she found her mother standing by the stove, boiling a pot of spaghetti. “That’s how I knew she was my mother,” my friend said. “She ate spaghetti in the middle of the night, just like me.”

Who are we, really? How much of what we do is a learned response to the assaults and rewards of life and how much is programmed in our genes from the moment of conception? This question is hardly new, nor are answers expected any time soon. One would expect recent advances in molecular biology to settle this issue once and for all, but they seem only to be adding to the confusion. In Time, Love, Memory, the science writer Jonathan Weiner takes us up and down the evolutionary ladder, looking for clues about the behavior of human beings from the DNA of insects and mice, and from the scientists who study them.

During the last forty-five years, a great number of discoveries about how cells work and how plants and animals develop have issued from molecular biology labs all over the world. In the 1950s and 1960s, many of the pioneers of the new biology were former physicists who realized that the kind of bold experimental and theoretical approaches that led to discoveries about the structure of the atom and quantum mechanics might also be applied to the study of life. In Time, Love, Memory, Weiner deals with the work of Seymour Benzer, who was in his twenties when he decided to leave physics and become a biologist. During World War II he worked in a top-secret government lab on semiconductors, and others would later build on his work to develop the transistor. Weiner suggests that, for the young Benzer, physics—or at least the physics in which he specialized—just seemed too easy. Benzer’s friends were eager to carry on their work in solid-state physics, or to set up lucrative electronics companies, but Benzer worried that the entire field was becoming pedestrian. On the other hand,…

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