The most atrocious acts of violence humans commit have been in warfare. Through the course of human history we have left countless children orphaned and violently raped millions of women. We have found untold means to torture enemy combatants deliberately inflicting pain beyond what most living organisms may have experienced. We have displayed the skulls of our enemies as trophies in our homes, or worse, used them as cups to consume our beverages. It seems that few things we do are as morally depraved as our behavior in warfare.
Yet, it is not the egregious violence and moral depravity that makes human warfare stand out. Deliberately torturing others may be a special human quality, but there is ample violence, injury and pain endured by animals in the struggle to obtain resources, reproduce and avoid death.
What is truly shocking about human warfare is that large numbers of reproductively capable, unrelated, and unfamiliar individuals die in combat for benefits that are widely shared. From our closest living relative in the animal kingdom, to the highly cooperative eusocial insects—no animal cooperates in war in this manner.
Chimps raid neighboring communities, but in the several decades of observing them, no chimp in the attacking party has been killed. They only attack when they outnumber the opponent sufficiently so that the attackers are unscathed. And the chimps that gang up for a raid know each other well, as they hail from the same community.
Ants readily sacrifice their lives in inter-colony battles, but the ants that do so are sterile individuals. They are giving up their lives to increase the fitness of the reproductively capable queen they are genetically related to.
Reciprocity and relatedness suffice to explain chimp and ant wars. Human warfare calls for a novel explanation.
But does human warfare stand out in the animal kingdom if kings, states, and other centralized political institutions are taken out of the picture. Perhaps our weird behavior is a result of powerful rulers who can coerce us to do anything, including give up our lives.
Answering this question has taken me a place in East Africa where different pastoral societies wage wars for cattle, pastures and water. The Turkana, the people I work with, are egalitarian herders. They make a living in the semi-arid savanna of northwest Kenya by keeping cattle, camel, goat, and sheep, and seasonally moving to find pastures and water. Periodically they mobilize and raid other settlements to acquire cattle and pastures, and to take revenge for previous attacks.
These attacks give the impression that human warfare does indeed require a novel explanation. Turkana warriors are not coerced by any authority. Yet in some areas of the Turkana one out of five males die in warfare. Of the males who survive to adulthood, one out of two die in warfare.
You may be tempted to think that in an egalitarian small-scale society everyone is either a friend or relative, and so this is simply cooperation with one’s kith and kin. But this is not the case. The Turkana number a million people, and are divided into about two-dozen different sub-territories. On Turkana raids hundreds of men from different territories come together. For a typical warrior most of his fellow combatants are neither kin nor close associates. Many are strangers.
So, really, why do these men go on raids, trusting that the strangers they are fighting with will do their part?
Some may say it is obvious why these men participate in warfare. After all, cattle are food, wealth, and the path to marriage. And cattle have feet—drive them away and you can make a fortune overnight. Not only so, without a fight they would lose their territory, and what is life for a herder without good pastures? And lets not forget, it is reproductive-aged men wielding AK-47s who go on these raids. The mix of youth, testosterone, and firearms—how can war not transpire?
Yet, acknowledging these motives—cows, pastures, and firearms—gets us only so far. AK-47-wielding, young, unmarried men have plenty of reasons to have a dustup with other men of their community. They share pastures and water, and vie for the same women. Yet, in quarrels with each other, they put aside their AK-47s, and hash out disputes with their herding sticks and wrist blades.
If you think it is the desire for cows, then consider that there are cows everywhere. The neighboring family has cows, the settlement across the river has cows, and herders in distant Turkana settlements have cows. Yet, Turkana men pass up on these hundreds of thousands of cows, and instead will travel large distances until they reach the settlement of people who do not consider themselves Turkana, before they raid cattle.
And yes, territory is precious. But, remarkably, Turkana from one territory typically allow Turkana from other territories to graze in their pastures, and such sharing is especially common in the dry season when grass and water are scarce. Yet, if the Toposa encroach, the Turkana of the area will mobilize a retaliatory raid.
Earlier in this post I noted that warfare is where moral depravity seems to abound. But perhaps the question to ask is why we have moral concerns at all, and why they extend to an arbitrary set of people who are neither relatives nor friends. Why does a Turkana herder pass up on the cows of some distant stranger, to go and raid the cows of some other distant stranger? Why use sticks to fight with some people, and AK-47s to fight with others? Why let some strangers graze in your scarce pastures and kill others for venturing too close? And is that set of people we have moral concerns towards just arbitrary, or is there some logic to our moral inclusivity?
Answering this can help make sense of a lot of the violence that we want to understand and limit. It would be a place for evolutionary thinking to make a useful contribution. And it has. Over the last couple decades, the field of cultural evolution has developed a game-changing idea—the theory of cultural group selection. Posited originally by Peter Richerson and Robert Boyd 1, and honed further by Joseph Henrich 2, the theory reveals that the cultural capacity of humans creates conditions for group selection to occur. Not genetic group selection, but selection among culturally distinct groups. Peter Turchin has applied this theory to answer questions of human history such as why empires rise and fall 3, and how cooperative states emerged 4. My work on Turkana warfare provides empirical support for cultural group selection in a non-state society 5. Together with Matthew Zefferman I’ve posited that cultural group selection can subsume existing evolutionary theories of warfare and account for many of the bizarre features of human warfare 6.
There is more to be done to evaluate the theory of cultural group selection…but as of now the theory tells us that the moral sphere of humans readily extends to include culturally similar people. This is useful because it implies that we could possibly expand the moral sphere by creating perceptions of cultural similarity. Finding the common thread that connects disparate cultures may not be just a cliché, but an evolutionarily backed-up path to peace.
- Boyd, R. & Richerson, P. J. Culture and the evolutionary process. (University of Chicago Press, 1985).
- Henrich, J. Cultural group selection, coevolutionary processes and large-scale cooperation. J. Econ. Behav. Organ. 53, 3–35 (2004).
- Turchin, P. War and Peace and War: The Rise and Fall of Empires. (Plume, 2006).
- Turchin, P. Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth. (Beresta Books, 2015).
- Mathew, S. & Boyd, R. Punishment sustains large-scale cooperation in prestate warfare. Proc. Natl. Acad. Sci. 108, 1091–6490 (2011).
- Zefferman, M. R. & Mathew, S. An evolutionary theory of large-scale human warfare: Group-structured cultural selection. Evol. Anthropol. 24, 50–61 (2015).