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It’s Complicated

June 5, 2017

Unraveling the Mystery of Why People Act as They Do

This review of Behave: The Biology of Humans at Our Best and Worst by Robert M. Sapolsky (Penguin Press, May 2018. ISBN 9780143110910) appeared in The American Scholar in June 2017.

Have you ever thought about killing someone? I have, and I confess that it brought me peculiar feelings of pleasure to fantasize about putting the hurt on someone who had wronged me. I am not alone. According to the evolutionary psychologist David Buss, who asked thousands of people this same question and reported the data in his 2005 book, The Murderer Next Door, 91 percent of men and 84 percent of women reported having had at least one vivid homicidal fantasy in their life. It turns out that nearly all murders (90 percent by some estimates) are moralistic in nature—not cold-blooded killing for money or assets, but hot-blooded homicide in which perpetrators believe that their victims deserve to die. The murderer is judge, jury, and executioner in a trial that can take only seconds to carry out.

What happens in brains and bodies at the moment humans engage in violence with other humans? That is the subject of Stanford University neurobiologist and primatologist Robert M. Sapolsky’s Behave: The Biology of Humans at Our Best and Worst. The book is Sapolsky’s magnum opus, not just in length, scope (nearly every aspect of the human condition is considered), and depth (thousands of references document decades of research by Sapolsky and many others) but also in importance as the acclaimed scientist integrates numerous disciplines to explain both our inner demons and our better angels. It is a magnificent culmination of integrative thinking, on par with similar authoritative works, such as Jared Diamond’s Guns, Germs, and Steel and Steven Pinker’s The Better Angels of Our Nature. Its length and detail are daunting, but Sapolsky’s engaging style—honed through decades of writing editorials, review essays, and columns for The Wall Street Journal, as well as popular science books (Why Zebras Don’t Get Ulcers, A Primate’s Memoir)—carries the reader effortlessly from one subject to the next. The work is a monumental contribution to the scientific understanding of human behavior that belongs on every bookshelf and many a course syllabus.

Sapolsky begins with a particular behavioral act, and then works backward to explain it chapter by chapter: one second before, seconds to minutes before, hours to days before, days to months before, and so on back through adolescence, the crib, the womb, and ultimately centuries and millennia in the past, all the way to our evolutionary ancestors and the origin of our moral emotions. He gets deep into the weeds of all the mitigating factors at work at every level of analysis, which is multilayered, not just chronologically but categorically. Or more to the point, uncategorically, for one of Sapolsky’s key insights to understanding human action is that the moment you proffer X as a cause—neurons, neurotransmitters, hormones, brain-specific transcription factors, epigenetic effects, gene transposition during neurogenesis, dopamine D4 receptor gene variants, the prenatal environment, the postnatal environment, teachers, mentors, peers, socioeconomic status, society, culture—it triggers a cascade of links to all such intervening variables. None acts in isolation. Nearly every trait or behavior he considers results in a definitive conclusion, “It’s complicated.” […]

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