Are Humans Inherently Warlike?

Elephant seal males batter each other to death during the breeding season. Only the largest, and most aggressive, males get to breed. These sire male offspring who are bigger and more aggressive than average.

So much for elephant seals! What about humans? Anthropologists studying the Yanomami tribe inhabiting the banks of the Orinoco River in South America told a similar story.

The Yanomami Story

The Yanomami are an indigenous people who make their living by a combination of food production in forest gardens, hunting, and gathering. They were studied by anthropologist Napoleon Chagnon who published a widely read ethnography of the group in 1968.

Chagnon's research concluded that, like elephant seals, men who are highly aggressive produce more offspring. If so, then their belligerent tendencies would be propagated to their offspring, making men in that society highly warlike.

Chagnon reported that men who had killed another individual in battle fathered more children. This interpretation was widely promoted by evolutionary psychologists because it seemed to confirm the value of genetic determinism in human societies.

However, subsequent researchers were unable to confirm Chagnon's findings, suggesting that there were problems with the original study. Despite apparent problems, the original research was highly influential in promoting the narrative that humans are inherently warlike and that our belligerent tendencies are the product of gene selection. This interpretation encounters a number of logical difficulties.

Are Humans Inherently Aggressive?

As a previously uncontacted people, the Yanomami were a prized resource for evolutionary anthropologists who often portrayed them as representatives of the lives of our subsistence ancestors across hundreds of millennia.

Yet, the Orinoco is not the Garden of Eden. Instead of being purely hunter–gatherers, the Yanomami are food producers. They are not of the Stone Age either, given the presence of trade goods such as metal cooking pots and steel tools, not to mention modern clothing like t-shirts and shorts. Their activities, including warfare, are increasingly influenced by the encroachment of state governments who are eager to appropriate their land.

The genetic theory of aggression is also problematic. While a person's genetic makeup may predispose them to aggression, our behavior is a function of many situational factors in addition to the familial and social environment in which we grow up. Genetic influences may also be indirect with greater size and strength predisposing some individuals to violence, for instance.

Problems With the Genetic Theory of Yanomami Warfare

Individual predispositions are not a promising explanation for group-level aggression. If we want to understand why people go to war, we must ask what they lack that a rival group possesses.

Warfare involves competition over resources that are valued and defensible.¹ This could be fertile land, or mineral resources, or access to water.

In the Yanomami case, there is a chronic scarcity of women. This reflects an unusual pattern of very many more males being born combined with greater female infanticide—hence, their pattern of raiding neighboring villages and abducting their women as wives.

While the genetic theory of Yanomami aggression clearly does not stand up, even if it did, it could tell us virtually nothing about our bellicosity as a species.

The Origin Myth

Yanomami warfare tells us about the causes of warfare in their society. It tells us little about warfare in our species as a whole. This is because their way of life, involving food cultivation, is comparatively recent. They are not representative of the early hunter–gatherer societies that accounted for much of our history as a species.

This is not a trivial issue because these earlier societies were not warlike. If one goes back in time a mere 12,000 years, there is no evidence of any warfare in the archaeological record.

This is not to say that there was no violence, but this was interpersonal and was not organized as a group-level activity.²

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Most societies experience interpersonal aggression. Much of this is related to sexual competition, whether this takes the form of male violence against women or fights between male rivals over a mate (to cite the most common causes of damaging aggression).

Humans are certainly capable of physical aggression, and this could be prevalent in simple hunter–gatherer societies. Yet, we are not inherently warlike. Group-level aggression is a feature of more complex societies. It only occurs if there is something worth fighting over, whether this is land, minerals, precious objects, or any other scarce and valuable resource that may be taken, and defended, through warfare.