THE FOURTH BRIDGE from biology to culture is evolutionary psychology, the study of the phylogenetic history and adaptive functions of the mind.55 It holds out the hope of understanding the design or purpose of the mind—not in some mystical or teleological sense, but in the sense of the simulacrum of engineering that pervades the natural world. We see these signs of engineering everywhere: in eyes that seem designed to form images, in hearts that seem designed to pump blood, in wings that seem designed to lift birds in flight.
Darwin showed, of course, that the illusion of design in the natural world can be explained by natural selection. Certainly an eye is too well engineered to have arisen by chance. No wart or tumor or product of a big mutation could be lucky enough to have a lens, an iris, a retina, tear ducts, and so on, all perfectly arranged to form an image. Nor is the eye a masterpiece of engineering literally fashioned by a cosmic designer who created humans in his own image. The human eye is uncannily similar to the eyes of other organisms and has quirky vestiges of extinct ancestors, such as a retina that appears to have been installed backwards.56 Today’s organs are replicas of organs in our ancestors whose design worked better than the alternatives, thereby enabling them to become our ancestors.57 Natural selection is the only physical process we know of that can simulate engineering, because it is the only process in which how well something works can play a causal role in how it came to be.
Evolution is central to the understanding of life, including human life. Like all living things, we are outcomes of natural selection; we got here because we inherited traits that allowed our ancestors to survive, find mates, and reproduce. This momentous fact explains our deepest strivings: why having a thankless child is sharper than a serpent’s tooth, why it is a truth universally acknowledged that a single man in possession of a good fortune must be in want of a wife, why we do not go gentle into that good night but rage, rage against the dying of the light.
Evolution is central to understanding ourselves because signs of design in human beings do not stop at the heart or the eye. For all its exquisite engineering, an eye is useless without a brain. Its output is not the meaningless patterns of a screen saver, but raw material for circuitry that computes a representation of the external world. That representation feeds other circuits that make sense of the world by imputing causes to events and placing them in categories that allow useful predictions. And that sense-making, in turn, works in the service of motives such as hunger, fear, love, curiosity, and the pursuit of status and esteem. As I mentioned, abilities that seem effortless to us—categorizing events, deducing cause and effect, and pursuing conflicting goals—are major challenges in designing an intelligent system, ones that robot designers strive, still unsuccessfully, to duplicate.
So signs of engineering in the human mind go all the way up, and that is why psychology has always been evolutionary. Cognitive and emotional faculties have always been recognized as nonrandom, complex, and useful, and that means they must be products either of divine design or of natural selection. But until recently evolution was seldom explicitly invoked within psychology, because with many topics, folk intuitions about what is adaptive are good enough to make headway. You don’t need an evolutionary biologist to tell you that depth perception keeps an animal from falling off cliffs and bumping into trees, that thirst keeps it from drying out, or that it’s better to remember what works and what doesn’t than to be an amnesiac.
But with other aspects of our mental life, particularly in the social realm, the function of a faculty is not so easy to guess. Natural selection favors organisms that are good at reproducing in some environment. When the environment consists of rocks, grass, and snakes, it’s fairly obvious which strategies work and which ones don’t. But when the relevant environment consists of other members of the species evolving their own strategies, it is not so obvious. In the game of evolution, is it better to be monogamous or polygamous? Gentle or aggressive? Cooperative or selfish? Indulgent with children or stern with them? Optimistic, pragmatic, or pessimistic?
For questions like these, hunches are unhelpful, and that is why evolutionary biology has increasingly been brought into psychology. Evolutionary biologists tell us that it is a mistake to think of anything conducive to people’s well-being—group cohesion, the avoidance of violence, monogamous pair bonding, aesthetic pleasure, self-esteem—as an “adaptation.” What is “adaptive” in everyday life is not necessarily an “adaptation” in the technical sense of being a trait that was favored by natural selection in a species’ evolutionary history. Natural selection is the morally indifferent process in which the most effective replicators outreproduce the alternatives and come to prevail in a population. The selected genes will therefore be the “selfish” ones, in Richard Dawkins’s metaphor—more accurately, the megalomaniacal ones, those that make the most copies of themselves.58 An adaptation is anything brought about by the genes that helps them fulfill this metaphorical obsession, whether or not it also fulfills human aspirations. And this is a strikingly different conception from our everyday intuitions about what our faculties were designed for.
The megalomania of the genes does not mean that benevolence and cooperation cannot evolve, any more than the law of gravity proves that flight cannot evolve. It means only that benevolence, like flight, is a special state of affairs in need of an explanation, not something that just happens. It can evolve only in particular circumstances and has to be supported by a suite of cognitive and emotional faculties. Thus benevolence (and other social motives) must be dragged into the spotlight rather than treated as part of the furniture. In the sociobiological revolution of the 1970s, evolutionary biologists replaced the fuzzy feeling that organisms evolve to serve the greater good with deductions of what kinds of motives are likely to evolve when organisms interact with offspring, mates, siblings, friends, strangers, and adversaries.
When the predictions were combined with some basic facts about the hunter-gatherer lifestyle in which humans evolved, parts of the psyche that were previously inscrutable turned out to have a rationale as legible as those for depth perception and the regulation of thirst. An eye for beauty, for example, locks onto faces that show signs of health and fertility—just as one would predict if it had evolved to help the beholder find the fittest mate.59 The emotions of sympathy, gratitude, guilt, and anger allow people to benefit from cooperation without being exploited by liars and cheats.60 A reputation for toughness and a thirst for revenge were the best defense against aggression in a world in which one could not call 911 to summon the police.61 Children acquire spoken language instinctively but written language only by the sweat of their brow, because spoken language has been a feature of human life for tens or hundreds of millennia whereas written language is a recent and slow-spreading invention.62
None of this means that people literally strive to replicate their genes. If that’s how the mind worked, men would line up outside sperm banks and women would pay to have their eggs harvested and given away to infertile couples. It means only that inherited systems for learning, thinking, and feeling have a design that would have led, on average, to enhanced survival and reproduction in the environment in which our ancestors evolved. People enjoy eating, and in a world without junk food, that led them to nourish themselves, even if the nutritional content of the food never entered their minds. People love sex and love children, and in a world without contraception, that was enough for the genes to take care of themselves.
The difference between the mechanisms that impel organisms to behave in real time and the mechanisms that shaped the design of the organism over evolutionary time is important enough to merit some jargon. A proximate cause of behavior is the mechanism that pushes behavior buttons in real time, such as the hunger and lust that impel people to eat and have sex. An ultimate cause is the adaptive rationale that led the proximate cause to evolve, such as the need for nutrition and reproduction that gave us the drives of hunger and lust. The distinction between proximate and ultimate
causation is indispensable in understanding ourselves because it determines the answer to every question of the form “Why did that person act as he did?” To take a simple example, ultimately people crave sex in order to reproduce (because the ultimate cause of sex is reproduction), but proximately they may do everything they can not to reproduce (because the proximate cause of sex is pleasure).
The difference between proximate and ultimate goals is another kind of proof that we are not blank slates. Whenever people strive for obvious rewards like health and happiness, which make sense both proximately and ultimately, one could plausibly suppose that the mind is equipped only with a desire to be happy and healthy and a cause-and-effect calculus that helps them get what they want. But people often have desires that subvert their proximate well-being, desires that they cannot articulate and that they (and their society) may try unsuccessfully to extirpate. They may covet their neighbor’s spouse, eat themselves into an early grave, explode over minor slights, fail to love their stepchildren, rev up their bodies in response to a stressor that they cannot fight or flee, exhaust themselves keeping up with the Joneses or climbing the corporate ladder, and prefer a sexy and dangerous partner to a plain but dependable one. These personally puzzling drives have a transparent evolutionary rationale, and they suggest that the mind is packed with cravings shaped by natural selection, not with a generic desire for personal well-being.
Evolutionary psychology also explains why the slate is not blank. The mind was forged in Darwinian competition, and an inert medium would have been outperformed by rivals outfitted with high technology—with acute perceptual systems, savvy problem-solvers, cunning strategists, and sensitive feedback circuits. Worse still, if our minds were truly malleable they would be easily manipulated by our rivals, who could mold or condition us into serving their needs rather than our own. A malleable mind would quickly be selected out.
Researchers in the human sciences have begun to flesh out the hypothesis that the mind evolved with a universal complex design. Some anthropologists have returned to an ethnographic record that used to trumpet differences among cultures and have found an astonishingly detailed set of aptitudes and tastes that all cultures have in common. This shared way of thinking, feeling, and living makes us look like a single tribe, which the anthropologist Donald Brown has called the Universal People, after Chomsky’s Universal Grammar.63 Hundreds of traits, from fear of snakes to logical operators, from romantic love to humorous insults, from poetry to food taboos, from exchange of goods to mourning the dead, can be found in every society ever documented. It’s not that every universal behavior directly reflects a universal component of human nature—many arise from an interplay between universal properties of the mind, universal properties of the body, and universal properties of the world. Nonetheless, the sheer richness and detail in the rendering of the Universal People comes as a shock to any intuition that the mind is a blank slate or that cultures can vary without limit, and there is something on the list to refute almost any theory growing out of those intuitions. Nothing can substitute for seeing Brown’s list in full; it is reproduced, with his permission, as an appendix (see p. 435).
The idea that natural selection has endowed humans with a universal complex mind has received support from other quarters. Child psychologists no longer believe that the world of an infant is a blooming, buzzing confusion, because they have found signs of the basic categories of mind (such as those for objects, people, and tools) in young babies.64 Archaeologists and paleontologists have found that prehistoric humans were not brutish troglodytes but exercised their minds with art, ritual, trade, violence, cooperation, technology, and symbols.65 And primatologists have shown that our hairy relatives are not like lab rats waiting to be conditioned but are outfitted with many complex faculties that used to be considered uniquely human, including concepts, a spatial sense, tool use, jealousy, parental love, reciprocity, peacemaking, and differences between the sexes.66 With so many mental abilities appearing in all human cultures, in children before they have acquired culture, and in creatures that have little or no culture, the mind no longer looks like a formless lump pounded into shape by culture.
But it is the doctrine of the Noble Savage that has been most mercilessly debunked by the new evolutionary thinking. A thoroughly noble anything is an unlikely product of natural selection, because in the competition among genes for representation in the next generation, noble guys tend to finish last. Conflicts of interest are ubiquitous among living things, since two animals cannot both eat the same fish or monopolize the same mate. To the extent that social motives are adaptations that maximize copies of the genes that produced them, they should be designed to prevail in such conflicts, and one way to prevail is to neutralize the competition. As William James put it, just a bit too flamboyantly, “We, the lineal representatives of the successful enactors of one scene of slaughter after another, must, whatever more pacific virtues we may also possess, still carry about with us, ready at any moment to burst into flame, the smoldering and sinister traits of character by means of which they lived through so many massacres, harming others, but themselves unharmed.”67
From Rousseau to the Thanksgiving editorialist of Chapter 1, many intellectuals have embraced the image of peaceable, egalitarian, and ecology-loving natives. But in the past two decades anthropologists have gathered data on life and death in pre-state societies rather than accepting the warm and fuzzy stereotypes. What did they find? In a nutshell: Hobbes was right, Rousseau was wrong.
To begin with, the stories of tribes out there somewhere who have never heard of violence turn out to be urban legends. Margaret Mead’s descriptions of peace-loving New Guineans and sexually nonchalant Samoans were based on perfunctory research and turned out to be almost perversely wrong. As the anthropologist Derek Freeman later documented, Samoans may beat or kill their daughters if they are not virgins on their wedding night, a young man who cannot woo a virgin may rape one to extort her into eloping, and the family of a cuckolded husband may attack and kill the adulterer.68 The !Kung San of the Kalahari Desert had been described by Elizabeth Marshall Thomas as “the harmless people” in a book with that title. But as soon as anthropologists camped out long enough to accumulate data, they discovered that the !Kung San have a murder rate higher than that of American inner cities. They learned as well that a group of the San had recently avenged a murder by sneaking into the killer’s group and executing every man, woman, and child as they slept.69 But at least the !Kung San exist. In the early 1970s the New York Times Magazine reported the discovery of the “gentle Tasaday” of the Philippine rainforest, a people with no words for conflict, violence, or weapons. The Tasaday turned out to be local farmers dressed in leaves for a photo opportunity so that cronies of Ferdinand Marcos could set aside their “homeland” as a preserve and enjoy exclusive mineral and logging rights.70
Anthropologists and historians have also been counting bodies. Many intellectuals tout the small numbers of battlefield casualties in pre-state societies as evidence that primitive warfare is largely ritualistic. They do not notice that two deaths in a band of fifty people is the equivalent of ten million deaths in a country the size of the United States. The archaeologist Lawrence Keeley has summarized the proportion of male deaths caused by war in a number of societies for which data are available:71
The first eight bars, which range from almost 10 percent to almost 60 percent, come from indigenous peoples in South America and New Guinea. The nearly invisible bar at the bottom represents the United States and Europe in the twentieth century and includes the statistics from two world wars. Moreover, Keeley and others have noted that native peoples are dead serious when they carry out warfare. Many of them make weapons as damaging as their technology permits, exterminate their enemies when they can get away with it, and enhance the experience by torturing captives, cutting off trophies, and feasting on enemy flesh.72
Counting societies instead of bodies leads to equally grim figures. In 1978
the anthropologist Carol Ember calculated that 90 percent of hunter-gatherer societies are known to engage in warfare, and 64 percent wage war at least once every two years.73 Even the 90 percent figure may be an underestimate, because anthropologists often cannot study a tribe long enough to measure outbreaks that occur every decade or so (imagine an anthropologist studying the peaceful Europeans between 1918 and 1938). In 1972 another anthropologist, W. T. Divale, investigated 99 groups of hunter-gatherers from 37 cultures, and found that 68 were at war at the time, 20 had been at war five to twenty-five years before, and all the others reported warfare in the more distant past.74 Based on these and other ethnographic surveys, Donald Brown includes conflict, rape, revenge, jealousy, dominance, and male coalitional violence as human universals.75
It is, of course, understandable that people are squeamish about acknowledging the violence of pre-state societies. For centuries the stereotype of the savage savage was used as a pretext to wipe out indigenous peoples and steal their lands. But surely it is unnecessary to paint a false picture of a people as peaceable and ecologically conscientious in order to condemn the great crimes against them, as if genocide were wrong only when the victims are nice guys.
The prevalence of violence in the kinds of environments in which we evolved does not mean that our species has a death wish, an innate thirst for blood, or a territorial imperative. There are good evolutionary reasons for the members of an intelligent species to try to live in peace. Many computer simulations and mathematical models have shown that cooperation pays off in evolutionary terms as long as the cooperators have brains with the right combination of cognitive and emotional faculties.76 Thus while conflict is a human universal, so is conflict resolution. Together with all their nasty and brutish motives, all peoples display a host of kinder, gentler ones: a sense of morality, justice, and community, an ability to anticipate consequences when choosing how to act, and a love of children, spouses, and friends.77 Whether a group of people will engage in violence or work for peace depends on which set of motives is engaged, a topic I will pursue at length in later chapters.
The Blank Slate: The Modern Denial of Human Nature Page 9