The Washington PostDemocracy Dies in Darkness

Humans evolved to be peaceful. Why are we still so violent?

Rachel Newcomb is an anthropologist and the Diane and Michael Maher Distinguished Professor of Teaching and Learning at Rollins College. She is the author of “Everyday Life in Global Morocco.”

In the past century, millions of humans have died at the hands of other humans through mass genocides, serial killings, wars and nuclear devastation. As a rule, however, people today are markedly less violent than our distant ancestors. In “The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution,” Harvard anthropologist Richard Wrangham takes the reader through the most current knowledge about human evolution to explain why people have developed into relatively docile creatures while retaining a capacity for acts of unspeakable violence. “How,” he asks, “could our domesticated qualities and our capacity for terrible violence be reconciled?”

The question of how humans came to be domesticated — at the will of a deity? independently, as some sort of evolved trait? — has plagued philosophers and scientists for hundreds of years. Wrangham addresses this question by assessing fascinating evidence from studies of primates, foxes, domesticated animals and hominid fossils to reconstruct the process of our domestication as a species.

Chimpanzees and bonobos, which inhabit neighboring terrain in Congo and are genetically similar, provide useful living examples of animals that share much of our DNA and exhibit humanlike emotions and behavior. But while bonobos are relatively peaceful creatures, chimpanzees exhibit no scruples about killing friends, lovers and even infants. In this way, Wrangham argues, chimpanzees and bonobos demonstrate the violence and peacefulness that coexist in humans. But how did they evolve so differently? In part, chimpanzee violence enabled them to compete with gorillas for resources, whereas the bonobos lived in an area with abundant foliage and little competition. Because violent bonobos were not necessary to the evolution of the species, they became more domesticated. Following the principles of evolution, natural selection would favor a reduction in what Wrangham calls “reactive aggression,” i.e. “an immediate response to an imminent threat that involves anger, fear, or both.” This domestication would have evolved in response to the situation, not at the hands of another being, whereas aggressiveness would have been a more useful trait for chimpanzees.

But is there a way to go beyond mere theory and observe the process in action? A Russian experiment with foxes underway since 1959 provides one interesting example. Soviet geneticist Dmitri Belyaev selected a population of silver foxes and bred those exhibiting friendliness and a lack of fear of humans. Within 35 generations, almost 80 percent of these foxes were as tame as dogs. Presumably dogs underwent similar domestication processes that transformed them from wild wolves into household companions. Might humans, Wrangham asks, have undergone a similar process? What clues could be found in the environment, and in deep history, to show why domestication in humans might have been evolutionarily favorable?

In addition to becoming tamer, domesticated animals tend to change physically as well, which Belyaev witnessed in the silver fox population. Wrangham has studied embryonic development for clues as to why domesticated animals often have smaller bodies, white spots on their foreheads, floppy ears or curly tails, traits almost never found in animals in the wild. As species become more domesticated, their form changes to resemble that of juveniles of their species. Humans changed as well, from broader bodies with thicker bones and wide faces to lighter forms with narrower features. The difference in the body size of men and women also declined.

Wrangham surveys the considerable literature on human social organization studied by anthropologists over the past 200 years. Before people settled into large-scale agricultural societies, with bigger populations and the complex bureaucratic systems needed to govern them, we were foragers, hunting and gathering our food and living in small, highly mobile groups. A popular myth is that foraging groups were peaceful until colonialism took away their mobility and restricted their traditional way of life, and that our capacity for great violence did not develop until we were in settled agricultural communities. But Wrangham cites numerous small-scale societies where brutal violence against other groups was the norm. He shows that in part, fear of the punishment meted out by governments in settled societies has gone a long way toward curbing violent impulses, such as murderous revenge raids on neighboring tribes.

Still, aside from fear of law, punishment or even divine retribution, what gives most humans a basic sense of morality, the kind of impulse that leads people to help a stranger in need, or at the very least to avoid responding in a murderous rage every time they have a dispute? The author asserts that the capacity for cooperation is an important characteristic that allowed our species to flourish. He contrasts us with Neanderthals, who died out 35,000 years ago after living in Europe for half a million years, until Homo sapiens arrived about 43,000 years ago. Wrangham suggests that Neanderthals’ cognitive inability to cooperate with one another and pass on the cultural knowledge necessary for survival may have led to their demise, especially once they came into competition for resources with the invading Homo sapiens.

“The Goodness Paradox” pieces together findings from anthropology, history and biology to reconstruct a vivid and comprehensive history of how humans evolved into domesticated creatures. Some readers may find it challenging at times to follow the detailed scientific explanations of topics such as neural-crest migration, an embryonic process that contributes both to reduced reactive aggression and to the seemingly random markings such as white patches that characterize domesticated animals. Nevertheless, the end result is rewarding, as “The Goodness Paradox” presents a complex but convincing perspective on how good and evil may have come to co-exist in our unique species.

By Richard Wrangham

Pantheon. 377 pp. $28.95