Have We Evolved for War?

Robert Barrett, PhD
5 min readMar 17, 2024
Photo by Антон Дмитриев on Unsplash

The mother wept as she recalls the fateful day her family was executed in front of her home. After the death squad members had shot each of her family members, they arrived at her. She recounts, to my interview team, how the gun barrel was pressed against her forehead, and then — nothing — but laughter. Pulling away, they hoped to leave her alive and in anguish to bury her children. She cried out and followed the gunmen, grabbing the barrel of the rifle and holding it to her head, begging them to end her life and her suffering. They refused — instead choosing to leave her in psychological agony.

This horrific story, and many more like it, were told during my doctoral field research in central Nigeria. For the mother, it was the first time she had spoken of that day.

The gunmen in this case, who have never been brought to justice were boys and men of all ages — all male — who were quick to embrace violence and death. Did women fight? No, but they supported it, pushing their husbands out the door because of the social fallout should their husbands not fight alongside their neighbours. Women also helped by spreading secret messages of attacks using songs in the marketplace. Recruiting of fighters was done in public, to maximize social pressure — applauding the so-called warriors who joined and shaming those men who did not.

Those who fought were promised land, status, wealth, and security. Those who did not fight would be banished.

Are humans uniquely violent?

One of the most significant studies of its kind, published in Nature, investigated the rate of interpersonal killing among 1024 species of mammals. Looking at extensive family trees — their phylogenetic history — the investigators analyzed 600 human societies dating back to the Neolithic era. The results revealed that 2% of all human deaths can be attributed to conspecific violence, a statistic comparable to other primates. The conclusion of this study was that there is nothing special about our large brains or our civilization that have made us especially peaceable — among mammals, we are about as violent as it gets.

If we define war as the killing of over 1000 people, the world has been at war for 92% of recorded history.

Thucydides wrote of a horrific plague that killed a quarter of all Athenians in 430 BCE. Now thought to have been typhus or smallpox, the plague was a catalyst for rapid social decline. Thucydides wrote that men (specifically), “not knowing what would happen next to them, became indifferent to every rule of religion or law”. The beast within is a common theory that suggests we are rapacious and self-serving animals who are kept at bay by self-imposed rules.

In 1986, a group of biologists, psychologists, and anthropologists gathered to issue the Seville Statement on Violence. Their conclusion, after much deliberation, was that humans are not inherently violent. Yet, this statement has not done much to quell the mystery of why humans are so uniquely warlike.

Especially violent animals, like humans, tend to have two significant attributes. They are very social and very territorial. Both ingredients together prove deadly. For example, whales and elephants are extremely social but not overly territorial. Humans also exhibit “surplus killing”, which is killing for the fun of it. Sure, house cats will play with their rodent victims and canines will hunt for sport to teach their young ones survival skills, but we humans are rather unique amongst mammals for our capacity to inflict harm onto one another.

While wars tend to be violent, there is an argument that they need not be. As Clausewitz wrote, “The conqueror is always a lover of peace; he would prefer to take over our country unopposed”, illustrating that wars can be tools to achieve political ends and not solely as a means of committing violence.

War as an evolutionary strategy.

When humans started to form agricultural communities instead of nomadic hunter-gatherer tribes — about 10,000 years ago during the Neolithic Period — it also provided opportunity for strongmen to raid and take over these settlements. These marauders were often patrilineal clans, meaning a large group of related men. As one can imagine, these thugs would have ensured they had first pick of the community’s women. We see genetic evidence of this.

In our modern online world, the “territory” we seek to defend may well be political ideas and worldviews.

5000–7000 years ago, we see a significant narrowing of Y-chromosome variation, with approximately 1 male for every 17 females. This indicates a strong polygynous effect, in which a few men get all the women. We all know the story of how Genghis Khan’s famous DNA circulates amongst a large portion of the world’s population — by some estimates, around 16 million men. There are other such genetically dominant lines, pointing to the role bands of related men had in conquering lands — and women. A Harvard University study has revealed that modern Europeans may have descended from just three Bronze Age warlords.

The Genetic Effect of War.

What happens when such men not only dominate communities but also our gene pool? Do we carry genetic information that favours war and conquer? Thus far, we have not found a specific “war gene”, nor have we identified a single instinct for war, but our social affinity for themes around dominance and submission, which are hardwired into our subconscious, lend support to the idea that we have, at minimum, evolved to employ conflict and conquer as strategy for securing resources and procreation. By virtue of the fact that the majority of us carry the genetic material of warlords and their dominant patrilineal thuggery, one wonders if this fuels our dark fascination with competition and war?

Today, we are beginning to see greater social and political fracturing and also increased frustration among younger generations over their economic future, access to resources, and the stalling of traditional life-course events, like dating, marriage, and family. To what extent these frustrations may trigger some form of ancestral defence mechanism to fight remains to be seen, but there is certainly a sense that disruptions to our social fabric are leading us toward a greater threat of conflict. In our modern online world, the “territory” we seek to defend may well be political ideas and worldviews. The study of peace and war must consider that we may have a lust for conflict that is baked into our very DNA.

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Robert Barrett, PhD
Robert Barrett, PhD

Written by Robert Barrett, PhD

Dr. Robert Barrett is the author of the bestselling book, HARDWIRED: How Our Instincts to Be Healthy Are Making Us Sick. (Published by Springer Nature).