In Rob Reiner’s 1992 film A Few Good Men, Jack Nicholson’s character — the battle-hardened Marine Colonel Nathan R. Jessup — is being cross-examined by Tom Cruise’s naive rookie Navy lawyer Lieutenant Daniel Kaffee, defending two Marines accused of killing a fellow soldier. He thinks Jessup ordered a “code red,” an off-the-books command to rough up a lazy Marine trainee in need of discipline, and that matters got tragically out of hand. Kaffee wants answers to specific questions about the incident. Jessup wants to lecture him on the meaning of freedom and the need to defend it: “Son, we live in a world that has walls. And those walls have to be guarded by men with guns. Who’s gonna do it? You? I have a greater responsibility than you can possibly fathom. You don’t want the truth. Because deep down, in places you don’t talk about at parties, you want me on that wall. You need me on that wall.”

The simple observation that we live in a world with walls — and have for the past 6,000 years of recorded history — implies that those walls are needed. The constitutions of states cannot completely alter the constitution of humanity. In my recently published book, The Science of Good and Evil, I present a theory on the evolutionary origins of morality in which I argue that humans evolved to be relatively moral and cooperative within groups and relatively immoral and competitive between groups. Natural selection created within-group amity and between-group enmity. The result is that we are, by nature, tribalistic; love thy neighbor has traditionally meant thy fellow in-group members. The long-term solution to many of our global problems, then, lies in expanding the circle of who we include as fellow in-group members.

Studies by anthropologists show that one of the prime triggers of between-group violence is competition for scarce resources. Once the carrying capacity of a group’s environment is exceeded, the demand for resources will exceed the supply, leading to between-group competition and war. Thus, one way to attenuate between-group violence is to increase the supply of resources to meet the demands of those in need of them. The nineteenth-century French economist Frederic Bastiat expressed it thusly: “Where goods do not cross frontiers, armies will.”

A case study can be found in the Yanomamö people of the Amazon, the so-called “fierce” people. There is good reason for the moniker because warfare has long been a part of Yanomamö life. As the anthropologist Napoleon Chagnon discovered, however, the Yanomamö are also sophisticated traders, and the more they trade the less they fight. The reason is that trade creates alliances.

If, as it is said, “the enemy of my enemy is my friend,” one of the primary means of protecting one’s group is to form alliances with other groups. Trade between groups is a powerful social adhesive. One village cannot go to another village and announce that they are worried about being conquered by a third, more powerful village, since this would reveal weakness. Instead, they mask the real motives for alliance through trade and feasting, and as a result not only gain military protection but insure inter-village peace. Most interestingly, even though each Yanomamö group could produce its own goods for survival, in fact they don’t; they set up a division of labor and system of trade. They do this not because they are nascent capitalists, but because they want to form political alliances with other groups, and trade is an effective means of so doing. The end result is that when goods cross Yanomamö frontiers, Yanomamö armies do not.

The point is this: trade evolved long before the state as a natural means of avoiding war. There is now archaeological evidence, for example, that over the past 200,000 years stone tools and other artifacts such as seashells, flint, mammoth ivory, and beads, were the objects of trade among our hominid ancestors, because they are often found hundreds of miles from where they were manufactured.
The psychology of trade probably has as much to do with forming alliances between individuals and groups as it does increasing the supply of resources, but the end result is the same: the cooperation that goes into making trade successful accentuates amity and attenuates enmity, leading to greater happiness and liberty for more people, in more places, more of the time.

Data from the neurosciences supports this thesis — cooperation leads to stimulation of the pleasure centers in the brain. Scientists at Emory University had 36 subjects play an exchange game while undergoing a functional magnetic resonance imaging (fMRI) brain scan. They found that the areas of the brains of cooperators that lit up were the same areas activated in response to such stimuli as desserts, money, cocaine, attractive faces, and other basic pleasures. Specifically, there were two broad areas dense in neurons that responded, both rich in dopamine (a neurochemical related to addictive behaviors): the anteroventral striatum in the middle of the brain (the so-called “pleasure center,” for which rats will endlessly press a bar to have it stimulated, even foregoing food), and the orbitofrontal cortex just above the eyes, related to impulse control and the processing of rewards. Tellingly, the cooperative subjects reported increased feelings of trust toward and camaraderie with their game partners.

How does trust translate to trade? At the Center for Neuroeconomics Studies at Claremont Graduate University, Paul Zak has demonstrated the relationship between oxytocin, trust, and economic prosperity. He argues that economists have shown how trust is among the most powerful factors affecting economic growth, and that since trust is directly related to neurological chemicals such as oxytocin, it is vital for national prosperity that the country maximize social interactions among its members, as well as members of other countries. Free trade is one of the most effective means of socializing, as is education, increased civil liberties, freedom of the press, freedom of association (most notably by increasing telephones and roads), and even a cleaner environment (people in countries with polluted environments show higher levels of estrogen antagonists, thereby lowering their levels of oxytocin and thus their feelings of trust).

Impoverished countries are poor, in part, because trust in the legal structures to protect business and personal investments are so low. Zak has even computed that “a 15 percent increase in the proportion of people in a country who think others are trustworthy raises income per person by 1 percent per year for every year thereafter.” For example, increasing levels of trust in the U.S. from its present 36 percent to 51 percent, would raise the average income for every man, woman, and child in the country by $400 per year, or $30,000 lifetime. It pays to trust.

Although extrapolating directly from neurochemistry to national economies is surely oversimplifying matters, what all this research tells us is that on one level we cooperate for the same reason we copulate — because it feels good. On a deeper evolutionary level, the reason cooperating feels good is because it is good for us, individually and as a species. Thomas Jefferson realized this in 1814: “These good acts give pleasure, but how it happens that they give us pleasure? Because nature hath implanted in our breasts a love of others, a sense of duty to them, a moral instinct, in short, which prompts us irresistibly to feel and to succor their distresses.”

How does trust and trade attenuate war and violence? In every case study of societies that made the transition from war to peace, there is a direct causal relationship between population size, ecological carrying capacity, and the availability and exchange of resources. The primary engine driving the shift in these ecological relationships is trade. When populations grow beyond the carrying capacity of their environments, they are forced into competition, which leads to war, which leads to alliances, which leads to trade, which leads to peace. In other words, the solution to war — that is, to move a society from a warlike existence to a peacelike existence — is not to be found in a particular type of government or religion or ideology or worldview; it is in a particular type of social process called trade. The evolutionary origin of trade may have been political alliances, but one of the unintended consequences is that trade produces a division of labor that generates more goods, for more people, more of the time.

This article was originally published in Toronto Globe and Mail.

Evolutionary biologist Jared Diamond of the University of California at Los Angeles once classified humans as the “third chimpanzee” (the second being the bonobo). Genetically, we are very similar, and when it comes to high levels of aggression between members of two different groups, as I noted in last month’s column on “The Ignoble Savage,” we also resemble chimpanzees. Although humans have a brutal history, there’s hope that the pessimists who forecast our eventual demise are wrong: recent evidence indicates that, like bonobos, we may be evolving in a more peaceful direction.

One of the most striking features in artificially selecting for docility among wild animals is that, along with far less aggression, you also get a suite of other changes, including a reduction in skull, jaw and tooth size. In genetics, this is called pleiotropy. Selecting for one trait may generate additional, unintended changes.

The most famous study on selective breeding for passivity began in 1959 by Russian geneticist Dmitri Belyaev of the Institute of Cytology and Genetics in Siberia. It continues today under the direction of Lyudmila N. Trut. Silver foxes were bred for friendliness toward humans, defined by a graduating series of criteria, from the animal allowing itself to be approached, to being hand fed, to being petted, to proactively seeking human contact. In only 35 generations the researchers produced tail-wagging, hand-licking, peaceful foxes. What they also created were foxes with smaller skulls, jaws and teeth than their wild ancestors.

The Russian scientists believe that in selecting for docility, they inadvertently selected for paedomorphism — the retention of juvenile features into adulthood — such as curly tails and floppy ears found in wild pups but not in wild adults, a delayed onset of the fear response to unknown stimuli, and lower levels of aggression. The selection process led to a significant decrease in levels of stress-related hormones such as corticosteroids, which
are produced by the adrenal glands during the fight-or-flight response, as well as a significant increase in levels of serotonin thought to play a leading role in the inhibition of aggression. The Russian scientists were also able to accomplish what no breeder had ever achieved before — a lengthened breeding season.

Like the foxes, humans have become more agreeable as we’ve become more domesticated. Whereas humans are like chimpanzees when it comes to between-group aggression, when it comes to levels of aggression among members of the same social group, we are much more like peaceful, highly sexual bonobos. Harvard University anthropologist Richard W. Wrangham proffers a plausible theory: as a result of selection pressures for greater within-group peacefulness and sexuality, humans and bonobos have gone down a different behavioral evolutionary path than chimps have.

Wrangham suggests that over the past 20,000 years, as humans became more sedentary and their populations grew, selection pressures acted to reduce within-group aggression. This effect can be seen in such features as smaller jaws and teeth than our immediate hominid ancestors, as well as our year-round breeding season and prodigious sexuality; bonobos were once called the “pygmy chimpanzee” because of their paedomorphic features. (Emory University psychologist Frans B. M. de Waal has documented how bonobos in particular use sexual contact as an important form of conflict resolution and social bonding.) Wrangham also shows how Area 13 in the human limbic frontal cortex, believed to mediate aggression, more closely resembles in size the equivalent area in bonobo brains than it does that same area in chimpanzees.

A plausible evolutionary hypothesis suggests itself: limited resources led to the selection for within-group cooperation and between-group competition in humans, resulting in within-group amity and between-group enmity. This evolutionary scenario bodes well for our species — if we can continue to expand the circle of whom we consider to be members of our in-group. Recent conflicts are not encouraging, but in the long run there is a trend toward including more people (such as women and minorities) within the in-group deserving of human rights.

In 1670 English poet John Dryden penned this expression of humans in a state of nature: “I am as free as Nature first made man … /When wild in woods the noble savage ran.” A century later, in 1755, French philosopher Jean-Jacques Rousseau canonized the noble savage in Western culture by proclaiming that “nothing can be more gentle than he in his primitive state, when placed by nature at an equal distance from the stupidity of brutes and the pernicious good sense of civilized man.”

From the Disneyfication of Pocahontas to Kevin Costner’s eco-pacifist Native Americans in Dances with Wolves and from postmodern accusations of corruptive modernity to modern anthropological theories that indigenous people’s wars are just ritualized games, the noble savage remains one of the last epic creation myths of our time. Science reveals a rather different picture of humanity in its natural state. In a 1996 study University of Michigan ecologist Bobbi S. Low analyzed 186 preindustrial societies and discovered that their relatively low environmental impact is the result of low population density, inefficient technology and lack of profitable markets, not conscious efforts at conservation. Anthropologist Shepard Krech III, in his 1999 book The Ecological Indian, shows that in a number of Native American communities, large-scale irrigation practices led to the collapse of their societies.

Even the reverence for big game animals that we have been told was held by Native Americans is a fallacy — many believed that common game animals such as elk, deer, caribou, beaver and especially buffalo would be physically reincarnated, thus easily replaced, by the gods. Given the opportunity to hunt big game animals to extinction, they did. The evidence is now overwhelming that many large mammals went extinct at the same time that the first Americans began to populate the continent.

Ignoble savages were nasty to one another as well as to their environments. Surveying primitive and civilized societies, University of Illinois anthropologist Lawrence H. Keeley, in his 1996 book War before Civilization, demonstrates that prehistoric war was, relative to population densities and fighting technologies, at least as frequent (measured in years at war versus years at peace), as deadly (determined by percentage of deaths resulting from conflict) and as ruthless (judged by the killing and maiming of noncombatants, women and children) as modern war. One pre-Columbian mass grave in South Dakota, for example, yielded the remains of 500 scalped and mutilated men, women and children.

In Constant Battles, a recent and exceptionally insightful study of this concept, Harvard University archaeologist Steven A. LeBlanc quips, “Anthropologists have searched for peaceful societies much like Diogenes looked for an honest man.” Consider the evidence from a 10,000-year-old Paleolithic site along the Nile River: “The graveyard held the remains of 59 people, at least 24 of whom showed direct evidence of violent death, including stone points from arrows or spears within the body cavity, and many contained several points. There were six multiple burials, and almost all those individuals had points in them, indicating that the people in each mass grave were killed in a single event and then buried together.”

LeBlanc’s survey reveals that even cannibalism, long thought to be a form of primitive urban legend (noble savages would never eat one another, would they?), is supported by powerful physical artifacts: broken and burned bones, cut marks on bones, bones cracked open lengthwise to get at the marrow, and bones inside cooking jars hacked so that they would fit. Such evidence for prehistoric cannibalism has been uncovered in Mexico, Fiji and parts of Europe. The definitive (and gruesome) proof came with the discovery of the human muscle protein myoglobin in the fossilized human feces of a prehistoric Anasazi pueblo Indian. Savage, yes. Noble, no.

Roman statesman Cicero noted, “Although physicians frequently know their patients will die of a given disease, they never tell them so. To warn of an evil is justified only if, along with the warning, there is a way of escape.” As we shall see in part two of this column, there is an escape from our disease.

Another battle has broken out in the century-long “anthropology wars” over the truth about human nature. Journalist Patrick Tierney, in his book dramatically entitled Darkness in El Dorado: How Scientists and Journalists Devastated the Amazon, purportedly reveals “the hypocrisy, distortions, and humanitarian crimes committed in the name of research, and reveals how the Yanomami’s internecine warfare was, in fact, triggered by the repeated visits of outsiders who went looking for a ‘fierce’ people whose existence lay primarily in the imagination of the West.”

Tierney’s bête noir is Napoleon Chagnon, whose ethnography Yanomamö: The Fierce People is the best-selling anthropological book of all time. Tierney spares no ink in painting him as an anthropologist who sees in the Yanomamö a reflection of himself. Chagnon’s sociobiological theories of the most violent and aggressive males winning the most copulations and thus passing on their genes for “fierceness,” Tierney says, is merely a window into Chagnon’s own libidinous impulses.

Are the Yanomamö the “fierce people”? Or are they the “erotic people,” as described by French anthropologist Jacques Lizot, another of Tierney’s targets? The problem lies in the phrasing of the question. Humans are not easily pigeonholed into such clear-cut categories. The nature and intensity of our behavior depend on a host of biological, social and historical variables. Chagnon understands this. Tierney does not. Thus, Darkness in El Dorado fails not just because he didn’t get the story straight (there are countless factual errors and distortions in the book) but because the book is predicated on a misunderstanding of how science works and of the difference between anecdotes (on which Tierney’s book is based) and statistical trends (on which Chagnon’s book depends).

To be sure, Tierney is a good storyteller, but this is what makes his attack on science so invidious. Because humans are storytelling animals, we are more readily convinced by dramatic anecdotes than by dry data. Many of his stories enraged me … until I checked Tierney’s sources myself.

For example, Tierney accuses Chagnon of using the Yanomamö to support a sociobiological model of an aggressive human nature. Yet the primary sources in question show that Chagnon’s deductions from the data are not so crude. Even on the final page of his chapter on Yanomamö warfare, Chagnon inquires about “the likelihood that people, throughout history, have based their political relationships with other groups on predatory versus religious or altruistic strategies and the cost-benefit dimensions of what the response should be if they do one or the other.” He concludes: “We have the evolved capacity to adopt either strategy.” These are hardly the words of a hidebound ideologue bent on indicting the human species.

The fourth edition of Chagnon’s classic carries no subtitle. Had he determined that the Yanomamö were not “the fierce people” after all? No. He realized that too often people “might get the impression that being ‘fierce’ is incompatible with having other sentiments or personal characteristics like compassion, fairness, valor, etc.” As his opening chapter notes, the Yanomamö “are simultaneously peacemakers and valiant warriors.” Like all people, the Yanomamö have a deep repertoire of responses.

My conclusion is that Chagnon’s view of the Yanomamö is basically supported by the evidence. His data and interpretations are corroborated by many other anthropologists. Even at their “fiercest,” however, the Yanomamö are not so different from many other peoples around the globe. Yanomamö violence is certainly no more extreme than that of our Paleolithic ancestors, who appear to have brutally butchered one another with abandon. If recorded history is any measure of “fierceness,” the Yanomamö have got nothing on Western “civilization.”

Homo sapiens are the erotic-fierce people, making love and war too often for our own good. Fortunately, we now have the scientific tools to illuminate our true natures and to help us navigate the treacherous shoals of surviving the transition from a state society to whatever comes next.