Behave: The Biology of Humans at Our Best and Worst

by Robert M. Sapolsky

There has been debate as to whether honor killings are “just” domestic violence, and whether morbid Western fascination with them reflects anti-Muslim bias;32 if some Baptist guy in Alabama murders his wife because she wants a divorce, no one frames it as a “Christian honor killing” reflecting deep religious barbarity. But honor killings typically differ from garden-variety domestic violence in several ways: (a) The latter is usually committed by a male partner; the former are usually committed by male blood relatives, often with the approval of and facilitation by female relatives. (b) The former is rarely an act of spontaneous passion but instead is often planned with the approval of family members. (c) Honor killings are often rationalized on religious grounds, presented without remorse, and approved by religious leaders. (d) Honor killings are carried out openly—after all, how else can “honor” be regained for the family?—and the chosen perpetrator is often an underage relative (e.g., a younger brother), to minimize the extent of sentencing for the act.

  By some pretty meaningful criteria, this is not “just” domestic violence. According to estimates by the UN and advocacy groups, five to twenty thousand honor killings occur annually. And they are not restricted to far-off, alien lands. Instead they occur throughout the West, where patriarchs expect their daughters to be untouched by the world they moved them to, where a daughter’s successful assimilation into this world proclaims the irrelevance of that patriarch.

  Left to right, starting top column: Shafilea Ahmed, England, killed by father and mother after resisting an arranged marriage; age 17. Anooshe Sediq Ghulam, Norway, married at 13; killed by husband after requesting a divorce; age 22. Palestina Isa, USA, killed by parents for dating someone outside the faith, listening to American music, and secretly getting a part-time job; age 16. Aqsa Parvez, Canada, killed by father and brother for refusing to wear a hajib; age 16. Ghazala Khan, Denmark, killed by nine family members for refusing an arranged marriage; age 19. Fadime Sahindal, Sweden, killed by father for refusing an arranged marriage; age 27. Hatun Surucu Kird, Germany, killed by brother after divorcing the cousin she was forced to marry at age 16; age 23. Hina Salem, Italy, killed by father for refusing an arranged marriage; age 20. Amina and Sarah Said, USA, both sisters killed by parents who perceived them as becoming too Westernized; ages 18 and 17.

  STRATIFIED VERSUS EGALITARIAN CULTURES

  Another meaningful way to think about cross-cultural variation concerns how unequally resources (e.g., land, food, material goods, power, or prestige) are distributed.33 Hunter-gatherer societies have typically been egalitarian, as we’ll soon see, throughout hominin history. Inequality emerged when “stuff”—things to possess and accumulate—was invented following animal domestication and the development of agriculture. The more stuff, reflecting surplus, job specialization, and technological sophistication, the greater the potential inequality. Moreover, inequality expands enormously when cultures invent inheritance within families. Once invented, inequality became pervasive. Among traditional pastoralist or small-scale agricultural societies, levels of wealth inequality match or exceed those in the most unequal industrialized societies.

  Why have stratified cultures dominated the planet, generally replacing more egalitarian ones? For population biologist Peter Turchin, the answer is that stratified cultures are ideally suited to being conquerors—they come with chains of command.34 Both empirical and theoretical work suggests that in addition, in unstable environments stratified societies are “better able to survive resource shortages [than egalitarian cultures] by sequestering mortality in the lower classes.” In other words, when times are tough, the unequal access to wealth becomes the unequal distribution of misery and death. Notably, though, stratification is not the only solution to such instability—this is where hunter-gatherers benefit from being able to pick up and move.

  A score of millennia after the invention of inequality, Westernized societies at the extremes of the inequality continuum differ strikingly.

  One difference concerns “social capital.” Economic capital is the collective quantity of goods, services, and financial resources. Social capital is the collective quantity of resources such as trust, reciprocity, and cooperation. You learn a ton about a community’s social capital with two simple questions. First: “Can people usually be trusted?” A community in which most people answer yes is one with fewer locks, with people watching out for one another’s kids and intervening in situations where one could easily look away. The second question is how many organizations someone participates in—from the purely recreational (e.g., a bowling league) to the vital (e.g., unions, tenant groups, co-op banks). A community with high levels of such participation is one where people feel efficacious, where institutions work transparently enough that people believe they can effect change. People who feel helpless don’t join organizations.

  Put simply, cultures with more income inequality have less social capital.35 Trust requires reciprocity, and reciprocity requires equality, whereas hierarchy is about domination and asymmetry. Moreover, a culture highly unequal in material resources is almost always also unequal in the ability to pull the strings of power, to have efficacy, to be visible. (For example, as income inequality grows, the percentage of people who bother voting generally declines.) Almost by definition, you can’t have a society with both dramatic income inequality and plentiful social capital. Or translated from social science–ese, marked inequality makes people crummier to one another.

  This can be shown in various ways, studied on the levels of Westernized countries, states, provinces, cities, and towns. The more income inequality, the less likely people are to help someone (in an experimental setting) and the less generous and cooperative they are in economic games. Early in the chapter, I discussed cross-cultural rates of bullying and of “antisocial punishment,” where people in economic games punish overly generous players more than they punish cheaters.* Studies of these phenomena show that high levels of inequality and/or low levels of social capital in a country predict high rates of bullying and of antisocial punishment.36

  Chapter 11 examines the psychology with which we think about people of different socioeconomic status; no surprise, in unequal societies, people on top generate justifications for their status.37 And the more inequality, the more the powerful adhere to myths about the hidden blessings of subordination—“They may be poor, but at least they’re happy/honest/loved.” In the words of the authors of one paper, “Unequal societies may need ambivalence for system stability: Income inequality compensates groups with partially positive social images.”

  Thus unequal cultures make people less kind. Inequality also makes people less healthy. This helps explain a hugely important phenomenon in public health, namely the “socioeconomic status (SES)/health gradient”—as noted, in culture after culture, the poorer you are, the worse your health, the higher the incidence and impact of numerous diseases, and the shorter your life expectancy.38

  Extensive research has examined the SES/health gradient. Four quick rule-outs: (a) The gradient isn’t due to poor health driving down people’s SES. Instead low SES, beginning in childhood, predicts subsequent poor health in adulthood. (b) It’s not that the poor have lousy health and everyone else is equally healthy. Instead, for every step down the SES ladder, starting from the top, average health worsens. (c) The gradient isn’t due to less health-care access for the poor; it occurs in countries with universal health care, is unrelated to utilization of health-care systems, and occurs for diseases unrelated to health-care access (e.g., juvenile diabetes, where having five checkups a day wouldn’t change its incidence). (d) Only about a third of the gradient is explained by lower SES equaling more health risk factors (e.g., lead in your water, nearby toxic waste dump, more smoking and drinking) and fewer protective factors (e.g., everything from better mattresses for overworked backs to health club memberships).

  What then is the principal cause of the gradient? Key work by Nancy Adler at UCSF showed that it
’s not so much being poor that predicts poor health. It’s feeling poor—someone’s subjective SES (e.g., the answer to “How do you feel you’re doing financially when you compare yourself with other people?”) is at least as good a predictor of health as is objective SES.

  Crucial work by the social epidemiologist Richard Wilkinson of the University of Nottingham added to this picture: it’s not so much that poverty predicts poor health; it’s poverty amid plenty—income inequality. The surest way to make someone feel poor is to rub their nose in what they don’t have.

  Why should high degrees of income inequality (independent of absolute levels of poverty) make the poor unhealthy? Two overlapping pathways:

  A psychosocial explanation has been championed by Ichiro Kawachi of Harvard. When social capital decreases (thanks to inequality), up goes psychological stress. A mammoth amount of literature explores how such stress—lack of control, predictability, outlets for frustration, and social support—chronically activates the stress response, which, as we saw in chapter 4, corrodes health in numerous ways.

  A neomaterialist explanation has been offered by Robert Evans of the University of British Columbia and George Kaplan of the University of Michigan. If you want to improve health and quality of life for the average person in a society, you spend money on public goods—better public transit, safer streets, cleaner water, better public schools, universal health care. But the more income inequality, the greater the financial distance between the wealthy and the average and thus the less direct benefit the wealthy feel from improving public goods. Instead they benefit more from dodging taxes and spending on their private good—a chauffeur, a gated community, bottled water, private schools, private health insurance. As Evans writes, “The more unequal are incomes in a society, the more pronounced will be the disadvantages to its better-off members from public expenditure, and the more resources will those members have [available to them] to mount effective political opposition” (e.g., lobbying). Evans notes how this “secession of the wealthy” promotes “private affluence and public squalor.” Meaning worse health for the have-nots.39

  The inequality/health link paves the way for understanding how inequality also makes for more crime and violence. I could copy and paste the previous stretch of writing, replacing “poor health” with “high crime,” and I’d be set. Poverty is not a predictor of crime as much as poverty amid plenty is. For example, extent of income inequality is a major predictor of rates of violent crime across American states and across industrialized nations.40

  Why does income inequality lead to more crime? Again, there’s the psychosocial angle—inequality means less social capital, less trust, cooperation, and people watching out for one another. And there’s the neomaterialist angle—inequality means more secession of the wealthy from contributing to the public good. Kaplan has shown, for example, that states with more income inequality spend proportionately less money on that key crime-fighting tool, education. As with inequality and health, the psychosocial and neomaterial routes synergize.

  A final depressing point about inequality and violence. As we’ve seen, a rat being shocked activates a stress response. But a rat being shocked who can then bite the hell out of another rat has less of a stress response. Likewise with baboons—if you are low ranking, a reliable way to reduce glucocorticoid secretion is to displace aggression onto those even lower in the pecking order. It’s something similar here—despite the conservative nightmare of class warfare, of the poor rising up to slaughter the wealthy, when inequality fuels violence, it is mostly the poor preying on the poor.

  This point is made with a great metaphor for the consequences of societal inequality.41 The frequency of “air rage”—a passenger majorly, disruptively, dangerously losing it over something on a flight—has been increasing. Turns out there’s a substantial predictor of it: if the plane has a first-class section, there’s almost a fourfold increase in the odds of a coach passenger having air rage. Force coach passengers to walk through first class when boarding, and you more than double the chances further. Nothing like starting a flight by being reminded of where you fit into the class hierarchy. And completing the parallel with violent crime, when air rage is boosted in coach by reminders of inequality, the result is not a crazed coach passenger sprinting into first class to shout Marxist slogans. It’s the guy being awful to the old woman sitting next to him, or to the flight attendant.*

  POPULATION SIZE, POPULATION DENSITY, POPULATION HETEROGENEITY

  The year 2008 marked a human milestone, a transition point nine thousand years in the making: for the first time, the majority of humans lived in cities.

  The human trajectory from semipermanent settlements to the megalopolis has been beneficial. In the developed world, when compared with rural populations, city dwellers are typically healthier and wealthier; larger social networks facilitate innovation; because of economies of scale, cities leave a smaller per-capita ecological footprint.42

  Urban living makes for a different sort of brain. This was shown in a 2011 study of subjects from a range of cities, towns, and rural settings who underwent an experimental social stressor while being brain-scanned. The key finding was that the larger the population where someone lived, the more reactive their amygdala was during that stressor.*43

  Most important for our purposes, urbanized humans do something completely unprecedented among primates—regularly encountering strangers who are never seen again, fostering the invention of the anonymous act. After all, it wasn’t until nineteenth-century urbanization that crime fiction was invented, typically set in cities—in traditional settings there’s no whodunit, since everyone knows what everyone dun.

  Growing cultures had to invent mechanisms for norm enforcement among strangers. For example, across numerous traditional cultures, the larger the group, the greater the punishment for norm violations and the more cultural emphases on equitable treatment of strangers. Moreover, larger groups evolved “third-party punishment” (stay tuned for more in the next chapter)—rather than victims punishing norm violators, punishment is meted out by objective third parties, such as police and courts. At an extreme, a crime not only victimizes its victim but also is an affront to the collective population—hence “The People Versus Joe Blow.”*44

  Finally, life in larger populations fosters the ultimate third-party punisher. As documented by Ara Norenzayan of the University of British Columbia, it is only when societies grow large enough that people regularly encounter strangers that “Big Gods” emerge—deities who are concerned with human morality and punish our transgressions.45 Societies with frequent anonymous interactions tend to outsource punishment to gods.* In contrast, hunter-gatherers’ gods are less likely than chance to care whether we’ve been naughty or nice. Moreover, in further work across a range of traditional cultures, Norenzayan has shown that the more informed and punitive people consider their moralistic gods to be, the more generous they are to coreligionist strangers in a financial allocation game.

  Separate from the size of a population, how about its density? One study surveying thirty-three developed countries characterized each nation’s “tightness”—the extent to which the government is autocratic, dissent suppressed, behavior monitored, transgressions punished, life regulated by religious orthodoxy, citizens viewing various behaviors as inappropriate (e.g., singing in an elevator, cursing at a job interview).46 Higher population density predicted tighter cultures—both high density in the present and, remarkably, historically, in the year 1500.

  The issue of population density’s effects on behavior gave rise to a well-known phenomenon, mostly well known incorrectly.

  In the 1950s John Calhoun at the National Institute of Mental Health asked what happens to rat behavior at higher population densities, research prompted by America’s ever-growing cities.47 And in papers for both scientists and the lay public, Calhoun gave a clear answer: high-density living produced “deviant” behavior and “socia
l pathology.” Rats became violent; adults killed and cannibalized one another; females were aggressive to their infants; there was indiscriminate hypersexuality among males (e.g., trying to mate with females who weren’t in estrus).

  The writing about the subject, starting with Calhoun, was colorful. The bloodless description of “high-density living” was replaced with “crowding.” Aggressive males were described as “going berserk,” aggressive females as “Amazons.” Rats living in these “rat slums” became “social dropouts,” “autistic,” or “juvenile delinquents.” One expert on rat behavior, A. S. Parkes, described Calhoun’s rats as “unmaternal mothers, homosexuals and zombies” (quite the trio you’d invite to dinner in the 1950s).48

  The work was hugely influential, taught to psychologists, architects, and urban planners; more than a million reprints were requested of Calhoun’s original Scientific American report; sociologists, journalists, and politicians explicitly compared residents of particular housing projects and Calhoun’s rats. The take-home message sent ripples through the American heartland destined for the chaotic sixties: inner cities breed violence, pathology, and social deviance.

  Calhoun’s rats were more complicated than this (something underemphasized in his lay writing). High-density living doesn’t make rats more aggressive. Instead it makes aggressive rats more aggressive. (This echoes the findings that neither testosterone, nor alcohol, nor media violence uniformly increases violence. Instead they make violent individuals more sensitive to violence-evoking social cues.) In contrast, crowding makes unaggressive individuals more timid. In other words, it exaggerates preexisting social tendencies.

  Calhoun’s erroneous conclusions about rats don’t even hold for humans. In some cities—Chicago, for example, circa 1970—higher population density in neighborhoods does indeed predict more violence. Nevertheless, some of the highest-density places on earth—Hong Kong, Singapore, and Tokyo—have miniscule rates of violence. High-density living is not synonymous with aggression in rats or humans.