Behave: The Biology of Humans at Our Best and Worst Read online

  ALSO BY ROBERT M. SAPOLSKY

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  A Primate’s Memoir

  The Trouble with Testosterone and Other Essays on the Biology of the Human Predicament

  Why Zebras Don’t Get Ulcers: A Guide to Stress, Stress-Related Diseases, and Coping

  Stress, the Aging Brain, and the Mechanisms of Neuron Death

  PENGUIN PRESS

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  New York, New York 10014

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  Copyright © 2017 by Robert M. Sapolsky

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  Illustration credits appear here.

  Library of Congress Cataloging-in-Publication Data

  Names: Sapolsky, Robert M., author.

  Title: Behave: the biology of humans at our best and worst / Robert M. Sapolsky.

  Description: New York: Penguin Press, 2017.

  Identifiers: LCCN 2016056755 (print) | LCCN 2017006806 (ebook) | ISBN 9781594205071 (hardback) | ISBN 9780735222786 (ebook)

  Subjects: LCSH: Neurophysiology. | Neurobiology. | Animal behavior. | BISAC: SCIENCE / Life Sciences / Biology / General. | SOCIAL SCIENCE / Criminology. | SCIENCE / Life Sciences / Neuroscience.

  Classification: LCC QP351 .S27 2017 (print) | LCC QP351 (ebook) | DDC 612.8–dc23

  LC record available at https://lccn.loc.gov/2016056755

  Interior Illustrations by Tanya Maiboroda here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here

  Version_1

  To Mel Konner, who taught me.

  To John Newton, who inspired me.

  To Lisa, who saved me.

  Contents

  Also by Robert M. Sapolsky

  Title Page

  Copyright

  Dedication

  INTRODUCTION

  One THE BEHAVIOR

  Two ONE SECOND BEFORE

  Three SECONDS TO MINUTES BEFORE

  Four HOURS TO DAYS BEFORE

  Five DAYS TO MONTHS BEFORE

  Six ADOLESCENCE; OR, DUDE, WHERE’S MY FRONTAL CORTEX?

  Seven BACK TO THE CRIB, BACK TO THE WOMB

  Eight BACK TO WHEN YOU WERE JUST A FERTILIZED EGG

  Nine CENTURIES TO MILLENNIA BEFORE

  Ten THE EVOLUTION OF BEHAVIOR

  Eleven US VERSUS THEM

  Twelve HIERARCHY, OBEDIENCE, AND RESISTANCE

  Thirteen MORALITY AND DOING THE RIGHT THING, ONCE YOU’VE FIGURED OUT WHAT THAT IS

  Fourteen FEELING SOMEONE’S PAIN, UNDERSTANDING SOMEONE’S PAIN, ALLEVIATING SOMEONE’S PAIN

  Fifteen METAPHORS WE KILL BY

  Sixteen BIOLOGY, THE CRIMINAL JUSTICE SYSTEM, AND (OH, WHY NOT?) FREE WILL

  Seventeen WAR AND PEACE

  EPILOGUE

  Acknowledgments

  Appendix 1: Neuroscience 101

  Appendix 2: The Basics of Endocrinology

  Appendix 3: Protein Basics

  Glossary of Abbreviations

  Notes

  Illustration Credits

  Index

  About the Author

  Introduction

  The fantasy always runs like this: A team of us has fought our way into his secret bunker. Okay, it’s a fantasy, let’s go whole hog. I’ve single-handedly neutralized his elite guard and have burst into his bunker, my Browning machine gun at the ready. He lunges for his Luger; I knock it out of his hand. He lunges for the cyanide pill he keeps to commit suicide rather than be captured. I knock that out of his hand as well. He snarls in rage, attacks with otherworldly strength. We grapple; I manage to gain the upper hand and pin him down and handcuff him. “Adolf Hitler,” I announce, “I arrest you for crimes against humanity.”

  And this is where the medal-of-honor version of the fantasy ends and the imagery darkens. What would I do with Hitler? The viscera become so raw that I switch to passive voice in my mind, to get some distance. What should be done with Hitler? It’s easy to imagine, once I allow myself. Sever his spine at the neck, leave him paralyzed but with sensation. Take out his eyes with a blunt instrument. Puncture his eardrums, rip out his tongue. Keep him alive, tube-fed, on a respirator. Immobile, unable to speak, to see, to hear, only able to feel. Then inject him with something that will give him a cancer that festers and pustulates in every corner of his body, that will grow and grow until every one of his cells shrieks with agony, till every moment feels like an infinity spent in the fires of hell. That’s what should be done with Hitler. That’s what I would want done to Hitler. That’s what I would do to Hitler.

  —

  I’ve had versions of this fantasy since I was a kid. Still do at times. And when I really immerse myself in it, my heart rate quickens, I flush, my fists clench. All those plans for Hitler, the most evil person in history, the soul most deserving of punishment.

  But there is a big problem. I don’t believe in souls or evil, think that the word “wicked” is most pertinent to a musical, and doubt that punishment should be relevant to criminal justice. But there’s a problem with that, in turn—I sure feel like some people should be put to death, yet I oppose the death penalty. I’ve enjoyed plenty of violent, schlocky movies, despite being in favor of strict gun control. And I sure had fun when, at some kid’s birthday party and against various unformed principles in my mind, I played laser tag, shooting at strangers from hiding places (fun, that is, until some pimply kid zapped me, like, a million times and then snickered at me, which made me feel insecure and unmanly). Yet at the same time, I know most of the lyrics to “Down by the Riverside” (“ain’t gonna study war no more”) plus when you’re supposed to clap your hands.

  In other words, I have a confused array of feelings and thoughts about violence, aggression, and competition. Just like most humans.

  To preach from an obvious soapbox, our species has problems with violence. We have the means to create thousands of mushroom clouds; shower heads and subway ventilation systems have carried poison gas, letters have carried anthrax, passenger planes have become weapons; mass rapes can constitute a military strategy; bombs go off in markets, schoolchildren with guns massacre other children; there are neighborhoods where everyone from pizza delivery guys to firefighters fears for their safety. And there are the subtler versions of violence—say, a childhood of growing up abused, or the effects on a minority people when the symbols of the majority shout domination and menace. We are always shadowed by the threat of other humans harming us.

  If that were solely the way things are, violence would be an easy problem to approach intellectually. AIDS—unambiguously bad news—eradicate. Alzheimer’s disease—same thing. Schizophrenia, cancer, malnutrition, flesh-eating bacteria, global warming, comets hitting earth—ditto.

  The problem, though, is that violence doesn’t go on that list. Sometimes we have no problem with it at all.

  This is a central point of this book—we don’t hate violence. We hate and fear the wrong kind of violence, violence in the wron
g context. Because violence in the right context is different. We pay good money to watch it in a stadium, we teach our kids to fight back, we feel proud when, in creaky middle age, we manage a dirty hip-check in a weekend basketball game. Our conversations are filled with military metaphors—we rally the troops after our ideas get shot down. Our sports teams’ names celebrate violence—Warriors, Vikings, Lions, Tigers, and Bears. We even think this way about something as cerebral as chess—“Kasparov kept pressing for a murderous attack. Toward the end, Kasparov had to oppose threats of violence with more of the same.”1 We build theologies around violence, elect leaders who excel at it, and in the case of so many women, preferentially mate with champions of human combat. When it’s the “right” type of aggression, we love it.

  It is the ambiguity of violence, that we can pull a trigger as an act of hideous aggression or of self-sacrificing love, that is so challenging. As a result, violence will always be a part of the human experience that is profoundly hard to understand.

  This book explores the biology of violence, aggression, and competition—the behaviors and the impulses behind them, the acts of individuals, groups, and states, and when these are bad or good things. It is a book about the ways in which humans harm one another. But it is also a book about the ways in which people do the opposite. What does biology teach us about cooperation, affiliation, reconciliation, empathy, and altruism?

  The book has a number of personal roots. One is that, having had blessedly little personal exposure to violence in my life, the entire phenomenon scares the crap out of me. I think like an academic egghead, believing that if I write enough paragraphs about a scary subject, give enough lectures about it, it will give up and go away quietly. And if everyone took enough classes about the biology of violence and studied hard, we’d all be able to take a nap between the snoozing lion and lamb. Such is the delusional sense of efficacy of a professor.

  Then there’s the other personal root for this book. I am by nature majorly pessimistic. Give me any topic and I’ll find a way in which things will fall apart. Or turn out wonderfully and somehow, because of that, be poignant and sad. It’s a pain in the butt, especially to people stuck around me. And when I had kids, I realized that I needed to get ahold of this tendency big time. So I looked for evidence that things weren’t quite that bad. I started small, practicing on them—don’t cry, a T. rex would never come and eat you; of course Nemo’s daddy will find him. And as I’ve learned more about the subject of this book, there’s been an unexpected realization—the realms of humans harming one another are neither universal nor inevitable, and we’re getting some scientific insights into how to avoid them. My pessimistic self has a hard time admitting this, but there is room for optimism.

  THE APPROACH IN THIS BOOK

  I make my living as a combination neurobiologist—someone who studies the brain—and primatologist—someone who studies monkeys and apes. Therefore, this is a book that is rooted in science, specifically biology. And out of that come three key points. First, you can’t begin to understand things like aggression, competition, cooperation, and empathy without biology; I say this for the benefit of a certain breed of social scientist who finds biology to be irrelevant and a bit ideologically suspect when thinking about human social behavior. But just as important, second, you’re just as much up the creek if you rely only on biology; this is said for the benefit of a style of molecular fundamentalist who believes that the social sciences are destined to be consumed by “real” science. And as a third point, by the time you finish this book, you’ll see that it actually makes no sense to distinguish between aspects of a behavior that are “biological” and those that would be described as, say, “psychological” or “cultural.” Utterly intertwined.

  Understanding the biology of these human behaviors is obviously important. But unfortunately it is hellishly complicated.2 Now, if you were interested in the biology of, say, how migrating birds navigate, or in the mating reflex that occurs in female hamsters when they’re ovulating, this would be an easier task. But that’s not what we’re interested in. Instead, it’s human behavior, human social behavior, and in many cases abnormal human social behavior. And it is indeed a mess, a subject involving brain chemistry, hormones, sensory cues, prenatal environment, early experience, genes, both biological and cultural evolution, and ecological pressures, among other things.

  How are we supposed to make sense of all these factors in thinking about behavior? We tend to use a certain cognitive strategy when dealing with complex, multifaceted phenomena, in that we break down those separate facets into categories, into buckets of explanation. Suppose there’s a rooster standing next to you, and there’s a chicken across the street. The rooster gives a sexually solicitive gesture that is hot by chicken standards, and she promptly runs over to mate with him (I haven’t a clue if this is how it works, but let’s just suppose). And thus we have a key behavioral biological question—why did the chicken cross the road? And if you’re a psychoneuroendocrinologist, your answer would be “Because circulating estrogen levels in that chicken worked in a certain part of her brain to make her responsive to this male signaling,” and if you’re a bioengineer, the answer would be “Because the long bone in the leg of the chicken forms a fulcrum for her pelvis (or some such thing), allowing her to move forward rapidly,” and if you’re an evolutionary biologist, you’d say, “Because over the course of millions of years, chickens that responded to such gestures at a time that they were fertile left more copies of their genes, and thus this is now an innate behavior in chickens,” and so on, thinking in categories, in differing scientific disciplines of explanation.

  The goal of this book is to avoid such categorical thinking. Putting facts into nice cleanly demarcated buckets of explanation has its advantages—for example, it can help you remember facts better. But it can wreak havoc on your ability to think about those facts. This is because the boundaries between different categories are often arbitrary, but once some arbitrary boundary exists, we forget that it is arbitrary and get way too impressed with its importance. For example, the visual spectrum is a continuum of wavelengths from violet to red, and it is arbitrary where boundaries are put for different color names (for example, where we see a transition from “blue” to “green”); as proof of this, different languages arbitrarily split up the visual spectrum at different points in coming up with the words for different colors. Show someone two roughly similar colors. If the color-name boundary in that person’s language happens to fall between the two colors, the person will overestimate the difference between the two. If the colors fall in the same category, the opposite happens. In other words, when you think categorically, you have trouble seeing how similar or different two things are. If you pay lots of attention to where boundaries are, you pay less attention to complete pictures.

  Thus, the official intellectual goal of this book is to avoid using categorical buckets when thinking about the biology of some of our most complicated behaviors, even more complicated than chickens crossing roads.

  What’s the replacement?

  A behavior has just occurred. Why did it happen? Your first category of explanation is going to be a neurobiological one. What went on in that person’s brain a second before the behavior happened? Now pull out to a slightly larger field of vision, your next category of explanation, a little earlier in time. What sight, sound, or smell in the previous seconds to minutes triggered the nervous system to produce that behavior? On to the next explanatory category. What hormones acted hours to days earlier to change how responsive that individual was to the sensory stimuli that trigger the nervous system to produce the behavior? And by now you’ve increased your field of vision to be thinking about neurobiology and the sensory world of our environment and short-term endocrinology in trying to explain what happened.

  And you just keep expanding. What features of the environment in the prior weeks to years changed the structure and function of that perso
n’s brain and thus changed how it responded to those hormones and environmental stimuli? Then you go further back to the childhood of the individual, their fetal environment, then their genetic makeup. And then you increase the view to encompass factors larger than that one individual—how has culture shaped the behavior of people living in that individual’s group?—what ecological factors helped shape that culture—expanding and expanding until considering events umpteen millennia ago and the evolution of that behavior.

  Okay, so this represents an improvement—it seems like instead of trying to explain all of behavior with a single discipline (e.g., “Everything can be explained with knowledge about this particular [take your pick:] hormone/gene/childhood event”), we’ll be thinking about a bunch of disciplinary buckets. But something subtler will be done, and this is the most important idea in the book: when you explain a behavior with one of these disciplines, you are implicitly invoking all the disciplines—any given type of explanation is the end product of the influences that preceded it. It has to work this way. If you say, “The behavior occurred because of the release of neurochemical Y in the brain,” you are also saying, “The behavior occurred because the heavy secretion of hormone X this morning increased the levels of neurochemical Y.” You’re also saying, “The behavior occurred because the environment in which that person was raised made her brain more likely to release neurochemical Y in response to certain types of stimuli.” And you’re also saying, “. . . because of the gene that codes for the particular version of neurochemical Y.” And if you’ve so much as whispered the word “gene,” you’re also saying, “. . . and because of the millennia of factors that shaped the evolution of that particular gene.” And so on.

  There are not different disciplinary buckets. Instead, each one is the end product of all the biological influences that came before it and will influence all the factors that follow it. Thus, it is impossible to conclude that a behavior is caused by a gene, a hormone, a childhood trauma, because the second you invoke one type of explanation, you are de facto invoking them all. No buckets. A “neurobiological” or “genetic” or “developmental” explanation for a behavior is just shorthand, an expository convenience for temporarily approaching the whole multifactorial arc from a particular perspective.