Behave: The Biology of Humans at Our Best and Worst

by Robert M. Sapolsky

  Meanwhile, ran the criticism, some traits exist not because they’re adaptive, or were adapted for something else but got co-opted, but because they’re baggage carried along with other traits that were selected for. It was here that Gould and Lewontin famously introduced “spandrels” in their 1979 paper “The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme.” A spandrel is an architectural term for the space between two arches, and Gould and Lewontin considered the artwork on the spandrels of the Basilica San Marco in Venice.*

  Gould and Lewontin’s stereotypical adaptationist would look at these spandrels and conclude that they were built to provide spaces for the artwork. In other words, that these spandrels evolved for their adaptive value in providing space for art. In reality they didn’t evolve for a purpose—if you’re going to have a series of arches (which most definitely exist for the adaptive purpose of holding up a dome), a space between each pair is an inevitable by-product. No adaptation. And as long as these spaces were carried along as evolutionary baggage as a result of selection for the adaptive arches, might as well paint on them. In that view, male nipples are spandrels—they serve an adaptive role in females and came along for the ride as baggage in males because there’s been no particular selection against males having them.* Gould and Lewontin argued that numerous traits that prompted just-so stories from adaptationists are merely spandrels.

  Sociobiologists responded to spandrelism by noting that the rigor in pronouncing something a spandrel was not intrinsically greater than that in pronouncing it adaptive.76 In other words, the former provide just-not-so stories. Psychologist David Barash and psychiatrist Judith Lipton compared spandrelites to the character Topsy in Uncle Tom’s Cabin, who states that she “just growed”—when faced with evidence of adaptation in traits, they’d conclude that those traits are mere baggage, without adaptive purpose, providing explanations that explained nothing—“just growed stories.”

  Furthermore, sociobiologists argued, adaptationist approaches were more rigorous than Gouldian caricature; rather than explaining everything and predicting nothing, sociobiological approaches predict plenty. Is, say, competitive infanticide a just-so story? Not when you can predict with some accuracy whether it will occur in a species based on its social structure. Nor is the pair-bond/tournament comparison, when you can predict a vast amount of information about the behavior, physiology, and genetics of species ranging across the animal kingdom simply by knowing their degree of sexual dimorphism. Furthermore, evolution leaves an echo of selection for adaptive traits when there is evidence of “special design”—complex, beneficial functions where a number of traits converge on the same function.

  —

  All this would be your basic, fun academic squabble, except that underlying the criticisms of adaptationism, gradualism, and sociobiology is a political issue. This is embedded in the title of the spandrel paper: the “Panglossian paradigm.” This refers to Voltaire’s Dr. Pangloss and his absurd belief, despite life’s miseries, that this is the “best of all possible worlds.” In this criticism, adaptationism stinks of the naturalistic fallacy, the view that if nature has produced something, it must be a good thing. That furthermore, “good” in the sense of, say, solving the selective problem of water retention in deserts, is in some indefinable way also morally “good.” That if ant species make slaves, if male orangutans frequently rape females, and if for hundreds of thousands of years hominin males drink milk directly out of the container, it is because it is somehow “meant” to be that way.

  When aired as a criticism in this context, the naturalistic fallacy had an edge to it. In its early years human sociobiology was wildly controversial, with conferences picketed and talks disrupted, with zoologists guarded by police at lectures, all sorts of outlandish things. On one storied occasion, E. O. Wilson was physically attacked while giving a talk.* Anthropology departments split in two, collegial relationships were destroyed. This was particularly so at Harvard, where many of the principals could be found—Wilson, Gould, Lewontin, Trivers, Hrdy, the primatologist Irven DeVore, the geneticist Jonathan Beckwith.

  Things were so febrile because sociobiology was accused of using biology to justify the status quo—conservative social Darwinism that implied that if societies are filled with violence, unequal distribution of resources, capitalistic stratification, male dominance, xenophobia, and so on, these things are in our nature and probably evolved for good reasons. The critics used the “is versus ought” contrast, saying, “Sociobiologists imply that when an unfair feature of life is the case, it is because it ought to be.” And the sociobiologists responded by flipping is/ought around: “We agree that life ought to be fair, but nonetheless, this is reality. Saying that we advocate something just because we report it is like saying oncologists advocate cancer.”

  The conflict had a personal tinge. This was because by chance (or not, depending on your viewpoint), that first generation of American sociobiologists were all white Southerners—Wilson, Trivers,* DeVore, Hrdy; in contrast, the first generation of its loudest critics were all Northeastern, urban, Jewish leftists—Harvard’s Gould, Lewontin, Beckwith, Ruth Hubbard, Princeton’s Leon Kamin, and MIT’s Noam Chomsky. You can see how the “there’s a hidden agenda here” charge arose from both sides.*

  It’s easy to see how punctuated equilibrium generated similar ideological battles, given its premise that evolution is mostly about long periods of stasis pierced by revolutionary upheaval. In their original publication, Gould and Eldredge asserted that the law of nature “holds that a new quality emerges in a leap as the slow accumulation of quantitative changes, long resisted by a stable system, finally forces it rapidly from one state into another.” This was a bold assertion that the heuristic of dialectical materialism not only extends beyond the economic world into the naturalistic one, but is ontologically rooted in the essential sameness of both worlds’ dynamic of resolution of irresolvable contradictions.* It is Marx and Engels as trilobite and snail.*

  —

  Eventually the paroxysms about adaptationism versus spandrels, gradualism versus punctuated change, and the very notion of a science of human sociobiology subsided. The political posturing lost steam, the demographic contrasts between the two camps softened, the general quality of research improved considerably, and everybody got some gray hair and a bit more calm.

  This has paved the way for a sensible, middle-of-the-road middle age for the field. There’s clear empirical evidence for both gradualism and punctuated change, and for molecular mechanisms underlying both. There’s less adaptation than extreme adaptationists claim, but fewer spandrels than touted by spandrelites. While sociobiology may explain too much and predict too little, it does predict many broad features of behavior and social systems across species. Moreover, even though the notion of selection happening at the level of groups has been resurrected from the graves of self-sacrificial elderly wildebeest, it is probably a rare occurrence; nonetheless, it is most likely to occur in the species that is the focus of this book. Finally, all of this is anchored in evolution being a fact, albeit a wildly complex one.

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  Remarkably, we’ve finished this first part of the book. A behavior has occurred; what happened in everything from a second to a million years earlier that helps explain why it happened? Some themes have come up repeatedly:

  The context and meaning of a behavior are usually more interesting and complex than the mechanics of the behavior.

  To understand things, you must incorporate neurons and hormones and early development and genes, etc., etc.

  These aren’t separate categories—there are few clear-cut causal agents, so don’t count on there being the brain region, the neurotransmitter, the gene, the cultural influence, or the single anything that explains a behavior.

  Instead of causes, biology is repeatedly about propensities, potentials, vulnerabilities, predispositions, proclivit
ies, interactions, modulations, contingencies, if/then clauses, context dependencies, exacerbation or diminution of preexisting tendencies. Circles and loops and spirals and Möbius strips.

  No one said this was easy. But the subject matters.

  —

  And thus we transition to the second part, synthesizing this material in order to look at realms of behavior where this matters the most.

  Eleven

  Us Versus Them

  As a kid, I saw the original 1968 version of Planet of the Apes. As a future primatologist, I was mesmerized, saw it repeatedly, and loved the cheesy ape costumes.

  Years later I discovered a great anecdote about the filming of the movie, related by both Charlton Heston and Kim Hunter, its stars: at lunchtime, the people playing chimps and those playing gorillas ate in separate groups.1

  As it’s been said (most often attributed to Robert Benchley), “There are two kinds of people in the world: those who divide the world into two kinds of people and those who don’t.” There are more of the first. And it is vastly consequential when people are divided into Us and Them, in-group and out-group, “the people” (i.e., our kind) and the Others.

  This chapter explores our tendency to form Us/Them dichotomies and to favor the former. Is this mind-set universal? How malleable are “Us” and “Them” categories? Is there hope that human clannishness and xenophobia can be vanquished so that Hollywood-extra chimps and gorillas break bread together?

  THE STRENGTH OF US/THEM

  Our brains form Us/Them dichotomies (henceforth, “Us/Them-ing,” for brevity) with stunning speed.2 As discussed in chapter 3, fifty-millisecond exposure to the face of someone of another race activates the amygdala, while failing to activate the fusiform face area as much as same-race faces do—all within a few hundred milliseconds. Similarly, the brain groups faces by gender or social status at roughly the same speed.

  Rapid, automatic biases against a Them can be demonstrated with the fiendishly clever Implicit Association Test (IAT).3

  Suppose you are unconsciously prejudiced against trolls. To simplify the IAT enormously: A computer screen flashes either pictures of humans or trolls or words with positive connotations (e.g., “honest”) or negative ones (“deceitful”). Sometimes the rule is “If you see a human or a positive term, press the red button; if it’s a troll or a negative term, press the blue button.” And sometimes it’s “Human or negative term, press red; troll or positive term, press blue.” Because of your antitroll bias, pairing a troll with a positive term, or a human with a negative, is discordant and slightly distracting. Thus you pause for a few milliseconds before pressing a button.

  It’s automatic—you’re not fuming about clannish troll business practices or troll brutality in the Battle of Somewhere in 1523. You’re processing words and pictures, and unconsciously you pause, stopped by the dissonance linking troll and “lovely,” or human and “malodorous.” Run enough rounds and that pattern of delay emerges, revealing your bias.

  The brain’s fault lines dividing Us from Them were shown in chapter 4’s discussion of oxytocin. Recall how the hormone prompts trust, generosity, and cooperation toward Us but crappier behavior toward Them—more preemptive aggression in economic play, more advocacy of sacrificing Them (but not Us) for the greater good. Oxytocin exaggerates Us/Them-ing.

  This is hugely interesting. If you like broccoli but spurn cauliflower, no hormone amplifies both preferences. Ditto for liking chess and disdaining backgammon. Oxytocin’s opposing effects on Us and Them demonstrate the salience of such dichotomizing.

  Our depth of Us/Them-ing is supported further by something remarkable—other species do it as well. Initially this doesn’t seem profound. After all, chimps kill males from other groups, baboon troops bristle when encountering each other, animals of all stripes tense at strangers.

  This simply reflects not taking kindly to someone new, a Them. But some other species have a broader concept of Us and Them.4 For example, chimp groups that have swollen in number might divide; murderous animosities soon emerge between ex-groupmates. Remarkably, you can show automatic Us/Them-ing in other primates with a monkey equivalent of the IAT. In one study animals were shown pictures of either members of their own or the neighboring group, interspersed with positive things (e.g., fruit) or negative (e.g., spiders). And monkeys looked longer at discordant pairings (e.g., group members with spiders). These monkeys don’t just fight neighbors over resources. They have negative associations with them—“Those guys are like yucky spiders, but us, us, we’re like luscious tropical fruit.”*

  Numerous experiments confirm that the brain differentially processes images within milliseconds based on minimal cues about race or gender.5 Similarly, consider “minimal group” paradigms, pioneered in the 1970s by Henri Tajfel of the University of Bristol. He showed that even if groupings are based on flimsy differences (e.g., whether someone over- or underestimated the number of dots in a picture), in-group biases, such as higher levels of cooperation, still soon develop. Such prosociality is about group identification—people preferentially allocate resources to anonymous in-group individuals.

  Merely grouping people activates parochial biases, no matter how tenuous the basis of the grouping. In general, minimal group paradigms enhance our opinion of Us rather than lessening our opinion of Them. I guess that’s meager good news—at least we resist thinking that people who came up heads on the coin toss (in contrast to our admirable tails) eat their dead.

  The power of minimal, arbitrary groupings to elicit Us/Them-ing recalls “green-beard effects” from chapter 10. Recall how these hover between prosociality due to kin selection and due to reciprocal altruism—they require an arbitrary, conspicuous, genetically based trait (e.g., a green beard) that indicates a tendency to act altruistically toward other green-bearders—under those conditions, green-bearders flourish.

  Us/Them-ing based on minimal shared traits is like psychological rather than genetic green-beard effects. We feel positive associations with people who share the most meaningless traits with us.

  As a great example, in one study subjects conversed with a researcher who, unbeknownst to them, did or didn’t mimic their movements (for example, leg crossing).6 Not only is mimicry pleasing, activating mesolimbic dopamine, but it also made subjects more likely to help the researcher, picking up their dropped pen. An unconscious Us-ness born from someone slouching in a chair like you do.

  Thus an invisible strategy becomes yoked to an arbitrary green-beard marker. What helps define a particular culture? Values, beliefs, attributions, ideologies. All invisible, until they are yoked with arbitrary markers such as dress, ornamentation, or regional accent. Consider two value-laden approaches to what to do to a cow: (A) eat it; (B) worship it. Two As or two Bs would be more peaceful when sorting out cow options than an A and B together. What might reliably mark someone who uses approach A? Maybe a Stetson and cowboy boots. And a B person? Perhaps a sari or a Nehru jacket. Those markers were initially arbitrary—nothing about the object called a sari intrinsically suggests a belief that cows are sacred because a god tends them. And there’s no inevitable link between carnivory and a Stetson’s shape—it keeps the sun out of your eyes and off your neck, useful whether you tend cows because you love steak or because Lord Krishna tended cows. Minimal group studies show our propensity for generating biased Us/Thems from arbitrary differences. What we then do is link arbitrary markers to meaningful differences in values and beliefs.

  And then something happens with those arbitrary markers. We (e.g., primates, rats, Pavlov’s dogs) can be conditioned to associate something arbitrary, like a bell, with a reward.7 As the association solidifies, is the ringing bell still “just” a marker symbolizing impending pleasure, or does it become pleasurable itself? Elegant work related to the mesolimbic dopamine system shows that in a substantial subset of rats, the arbitrary signal itself becomes rewarding. Similarly, an arbitrary sym
bol of an Us core value gradually takes on a life and power of its own, becoming the signified instead of the signifier. Thus, for example, the scattering of colors and patterns on cloth that constitutes a nation’s flag becomes something that people will kill and die for.*

  The strength of Us/Them-ing is shown by its emergence in kids. By age three to four, kids already group people by race and gender, have more negative views of such Thems, and perceive other-race faces as being angrier than same-race faces.8

  And even earlier. Infants learn same-race faces better than other-race. (How can you tell? Show an infant a picture of someone repeatedly; she looks at it less each time. Now show a different face—if she can’t tell the two apart, she barely glances at it. But if it’s recognized as being new, there’s excitement, and longer looking).9

  Four important thoughts about kids dichotomizing:

  Are children learning these prejudices from their parents? Not necessarily. Kids grow in environments whose nonrandom stimuli tacitly pave the way for dichotomizing. If an infant sees faces of only one skin color, the salient thing about the first face with a different skin color will be the skin color.