Are Humans Inherently Warlike?

Edward O. Wilson has written a book titled The Social Conquest of Earth.  In it he includes a chapter with the title War as Humanity’s Hereditary Curse.  He provides this summary:

“Our bloody nature, it can now be argued in the context of modern biology, is ingrained because group-versus-group was a principle driving force that made us what we are.  In prehistory, group selection lifted the hominids that became territorial carnivores to heights of solidarity, to genius, to enterprise.  And to fear.  Each tribe knew with justification that if it was not armed and ready, its very existence was imperiled.  Throughout history, the escalation of a large part of technology has had combat as its central purpose.”

One could argue that recent history (since about 14,000 years ago) was dominated by the founding of large settlements with permanent and collected assets that required protection.  Defense from predation by other groups often required collective military-like action—war essentially.  A similar organizational imperative arises when the desire is to acquire another group’s assets.  The development of fixed and long-lasting sites could be an inflection point in human history in which warlike behavior first began to be selected as a desirable trait.  Wilson will have none of that.

“It should not be thought that war, often accompanied by genocide, is a cultural artifact of a few societies.  Nor has it been an aberration of history, a result of the growing pains of our species’ maturation.  Wars and genocide have been universal and eternal, respecting no particular time or culture.”

Since the human species has been accumulating genetic characteristics for millions of years, it is a rather bold step to claim war as “universal and eternal.”  To support this contention, he turns to chimpanzees and their current behavior patterns for evidence that humans have always been warlike.  Did everyone follow that bit of logic?  Anthropologists believe that chimpanzees and what eventually became homo sapiens shared a common ancestor with the two species diverging about 6 million years ago.

“There is no certain way to decide on the basis of existing knowledge whether chimpanzee and human inherited their pattern of territorial aggression from a common ancestor or whether they evolved it independently in response to parallel pressures of natural selection and opportunities encountered in the African homeland.  From the remarkable similarity in behavioral detail between the two species, however, and if we use the fewest assumptions required to explain it, a common ancestry seems the more likely choice.”

What Wilson describes as our nearest neighbor, genetically, is actually the common chimpanzee, one of two chimp species.  About 1 million years ago a group of chimpanzees became physically isolated from the main body of the species and has evolved independently since that time.  This species is referred to as the Bonobo.  In one million years of separate evolution this chimp has evolved to possess quite different characteristics.

Bonobos have a much more peaceful temperament than the common chimpanzee.  They also have produced a society with a matriarchal tendency.  The alpha male seems to have responsibility for executing tasks, but the alpha female can refuse to follow his orders and the rest of the community will follow her lead.  In fact, the males seem to inherit their authority based on the rank of their mother.  One researcher referred to the alpha male as the general— who could be trumped by the alpha female who was the queen.  Perhaps the most unusual and interesting aspect of Bonobo society is the role of sex.  Someone was quoted as saying that if two groups of Bonobos would meet unexpectedly, it was more likely that an orgy would breakout rather than warfare.  The Bonobos, both male and female, are bisexual, very inventive, and very active.  They occasionally experiment with the missionary position and practice oral sex.  The offer of sexual activity seems to be associated with social bonding and seems to be given in much the same way we might provide a guest with a cup of coffee.

One could describe the social activity of the Bonobos as “human-like” and claim that they are the species that humans are most similar to and make whatever inferences one might wish.  It is easy to get drawn into the study of animal societies and try to draw conclusions about human nature.  The fact that these two lines of chimpanzees could develop so differently over the course of a million years might lead one to conclude that humans could also go off in their own unique direction over a period of six million years.  We are what we are, and we have no one to blame but ourselves.

In any event, Wilson presents a picture in which human society evolved by adapting to the need to continually fight to protect resources or steal them from other bands of humans.  The enhanced social skills we developed relative to the other apes were driven by the need to coordinate actions by males in this quasi-military activity.  He assumes that this need for aggressive behavior persisted throughout prehistory as well as recorded history.  He turns to investigations of primitive hunter-gatherer societies as the only way to guess at what life and society might have been like for our ancestors many millennia ago.  He concludes that the data support his view.

Sarah Blaffer Hrdy is an evolutionary anthropologist (Wilson is best known as an entomologist) who looks at data from hunter-gatherer societies and draws an entirely opposite conclusion.  She describes her views on what has driven our social evolution in Mothersand Others: The Evolutionary Origins of Mutual Understanding.  She might describe Wilson’s conclusions as those one might expect from a male who anticipates a male-dominated history.  She then proceeds to develop a theory that Wilson might claim was one that might be expected from a female anticipating a history heavily dependent on female developments.  Let us hope that Hrdy is the one who is correct.

If one must explain the human tendency for warlike behavior, one should also have to explain why sharing evolved as such a peculiarly human attribute.  Chimps fight but they do not share. 

“Why would sharing with others, even strangers, be so automatic?  And why, in culture after culture, do people everywhere devise elaborate customs for the public presentation, consumption, and exchange of goods.”

“Gift exchange cycles like the famous ‘kula ring’ of Melanesia, where participants travel hundreds of miles by canoe to circulate valuables, extend across the Pacific region and can be found in New Zealand, Samoa and the Trobriand Islands”

There were never large numbers of early humans during most of the evolutionary history in Africa.  The fact that other ape-like versions came and went likely meant that humans spent some time on the verge of extinction themselves.  A species struggling to survive probably consisted of small bands totally focused on the need to find food.  Would animals in such a state be likely to wish to expend their meager energy learning how to kill others, or be more likely to devise means of collaborating with others?

“The sporadic success and frequent failures of big-game hunters is a chronic challenge for hungry families among traditional hunter-gatherers.  One particularly detailed case study of South American forgers suggests that roughly 27 percent of a time a family would fall short of the 1,000 calories of food per person per day needed to maintain body weight.  With sharing, however, a person can take advantage of someone else’s good fortune to tide him through lean times.  Without it, perpetually hungry people would fall below the minimum number of calories they needed.  The researchers calculated that once every 17 years, caloric deficits for nonsharers would fall below 50 percent of what was needed 21 days in a row, a recipe for starvation.  By pooling their risk, the proportion of days that people suffered from such caloric shortfalls fell from 27 percent to only 3 percent.”

This example was meant to illustrate how obviously beneficial it would be to share rather than to attempt to steal by force.  Such aggression might have been a short-term solution, but it would have been a long-term disaster. 

Hrdy also provides a compelling example of how this sharing became ritualized.  She describes research by Polly Wiessner of an African Bushman tribe called the Ju/’hoansi and the exchange networks they formed that were referred to as hexaro.

“Some 69 percent of the items every Bushman used—knives, arrows, and other utensils; beads and clothes—were transitory possessions, fleetingly treasured before being passed on in a chronically circulating traffic of objects.  A gift received one year was passed on the next.  In contrast to our own society where regifting is regarded as gauche, among the Ju/’hoansi it was not passing things on—valuing an object more than a relationship, or hoarding a treasure—that was socially unacceptable.”

“In her detailed study of nearly a thousand hxaro partnerships over thirty years, Wiessner learned that the typical adult had anywhere from 2 to 42 exchange relationships, with an average of 16.  Like any prudently diversified stock portfolio, partnerships were balanced so as to include individuals of both sexes and all ages, people skilled in different domains and distributed across space.  Approximately 18 percent resided in the partner’s own camp, 24 percent in nearby camps, 21 percent in a camp at least 16 kilometers away, and 33 percent in more distant camps, between 51 and 200 kilometers away.”

According to Hrdy, the critical step in human evolution—and human survival—was when human women began to share responsibility for taking care of young children.  At one time females were much smaller than males.  If they were to grow larger and accommodate the growing human brain size they would have to be able to gather more food than they could when encumbered by a child.  In a sense, they developed a capability to leave an infant at childcare while they went off to work.  This meant that the woman would also return the favor when others needed the same service.  The ability to socialize these agreements and accommodate others’ needs and feelings requires an ability to sense emotions and express empathy that was way beyond anything other apes were capable of.

“From a tender age and without special training, modern humans identify with the plights of others and without being asked, volunteer to help and share, even with strangers.  In these respects, our line of apes is in a class by itself.”

“This ability to identify with others and vicariously experience their suffering is not simply learned: It is a part of us.”

In Hrdy’s scenario, we did not develop into creatures capable of great civilizations because our bigger brains allowed us to develop the necessary social skills, it was the development—starting over a million years ago—of social skills required for survival that made possible the evolution of the large-brained human.

While Hrdy would recognize that there are hunter-gatherer tribes that are aggressive and do seem to behave in a fashion similar to common chimpanzees, she would disagree with referring to such tendencies as “universal and eternal.”

Patricia S. Churchland provides yet another perspective in her book Touching a Nerve: The Self as Brain.  She devotes a section to discussing the question “Is genocide in our genes?”

“To claim that genocide is in our genes on the grounds that humans do commit genocide would be like saying that we have genes for reading and writing because humans do read and write.  This latter we know to be wrong.  Writing and reading were invented a mere 5,000 years ago and were made possible by other, more general capacities that we have, such as fine motor control in our hands and the capacity for detailed pattern recognition.”

Acting aggressively and even murderously can be triggered by social and environmental signals.  People go to war because they have been convinced that it is beneficial to their society.  Acting in such a way as to benefit society is the selected attribute (through natural selection) not violence itself.

“From all that we now know, human warfare was not as such selected for biological evolution.  It may have been, like reading, a cultural invention that exploited other capacities.”

It is difficult to believe the notion that violent aggressive behavior is “universal and eternal” in humans.  There is too much contradictory data.  It seems more likely that the growth of agriculture and animal domestication about 14,000 years ago triggered variations in natural selection and conceivably generated humans with a greater tendency to resort to violence to attain their desires.

Churchland provides us an example of how powerful natural selection can be in certain circumstances.  It seems that fruit flies exhibit aggressive behavior.

“Geneticists Herman Dierick and Ralph Greenspan selectively bred aggressive fruit flies for even more aggressive behavior.  After 21 generations, the male fruit flies were 30 times more aggressive than the wild-type flies.  Just like breeding dogs.”

If we take 21 human generations as being about 500 years, then during a long period when survival meant being skilled as a warrior, one might expect a more warlike human to emerge.  On the other hand, 500 years when being warlike was a disadvantage—and could get you killed, or at least removed from the gene pool—would lead one to suspect a more cooperative and sympathetic human to emerge.  If there were a million years of evolution, how many attributes would be selected and then deselected—and how many times.

As we continue to change the social and physical environment in which we live, who knows what natural selection might be doing to us. 

We are not who we were and we are not who we will be—but at least we are not universally and eternally warlike.