Why War? From the Pleistocene to the Present: an Anthropological Perspective

In: Public Anthropologist
R. Brian Ferguson Professor of Anthropology, Rutgers University, Newark, NJ, USA

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Editorial and opinion pieces speculate (or proclaim) about the foundations of war, the curse of humanity. Here is another perspective, backed by forty years of anthropological research, on origins, causes, variations, and meanings of war, and their contemporary implications.


Editorial and opinion pieces speculate (or proclaim) about the foundations of war, the curse of humanity. Here is another perspective, backed by forty years of anthropological research, on origins, causes, variations, and meanings of war, and their contemporary implications.

Since the Vietnam era, I’ve worked on my own anthropological perspective on war.1 It pushes in two directions: addressing the question of human nature and war, whether people have an evolved predisposition to kill outsiders; and developing a general theory of war, from why war exists, to varying cultural patterns of war, to decisions for specific wars. This is a distillation of the perspective, an anthropological editorial on war.2

On human nature, many argue or simply assume that people – or men – are evolutionarily programmed to fatally divide some “them” from some “us,” (while acknowledging cultural overlays and situational variations). Are men born somehow inclined in some way to kill outsiders, the “them” of reproductive competition? Obviously, we are capable of war, and often choose it. The question is whether evolution tilts us in that direction. I say no.

Humanity’s unique evolutionary advantage is an absence of innate social proclivities, together with omnivorously learning intelligence. Plasticity is the bed of culture, humanity’s adaptive dimension. Culture in motion, constrained by practical realities and responding to exogenous inputs, makes history. The confluence of all, socially and symbolically processed, creates immediate circumstances for actual war. This is the realm of agency, which includes personalities of leaders, where “us vs. them” is constructed, framing choices for peace or war.

Neo-Darwinian innatism is a platform supported by three pillars: “tribal” warfare, war signs in the archaeological record, and war-like behavior by chimpanzees. I’ve examined all three.

“Tribal,” as in “people are tribal,” is a foggy notion, often taken to mean that people naturally cleave to their own kind against outsiders. Not so. Paleolithic artifacts show uninterrupted stylistic continuities at continental scale – one big people. Holocene archaeology finds geographic differentiations of artifacts, associated with social networks across landscapes, but with mixing on peripheries and without indication of bounding. Much later, with states in the picture, clear tribal borders arise from economic, political, and military processes within tribal zones – where indigenous peoples are metamorphized but not administered by states. In contemporary societies, us/them is entirely situation-dependent. What “us” are you?

If war wells up from human nature it should be present throughout the archaeological record – and so it is claimed. Hardly. War leaves clues in bones, settlements and tools. Typically, signs of war do not appear in very early archaeological sequences – although individual and non-lethal violence are not rare. Common claims of 15–25% violent death across archaeology come from cherry picking unusually violent situations; and/or imagining that later finds exemplify earlier times. Looking at all reports across wide regions shows that evidence of war appears and becomes common after millennia without. Broadly, war signs appear following preconditions of increasing sedentism, population density, and concentrated material valuables. These enable other preconditions of social bounding, hierarchy, and elite trade, often lumped together as “complexity” – and possibly also heightened patriarchy. Climate reversals fostered much war, though not in simple ways. More brightly, there are independent preconditions of peace, which nurture non-militaristic social trajectories even up to states. These are developed by Fry:3 cross-cutting social webs, structured group interdependence and cooperation, values that promote peace and stigmatize violence, and legitimate authorities who can rein in impetuous attacks and oversee ways and means of conflict resolution. In the southern western Mediterranean Levant from 13,000 to 3,200 bc, these preconditions and peace seem to prevail.

To avoid confusion, war is not attendant upon agriculture or states. Settled complex and equestrian hunter gatherers often made war. Initial domestication can be followed by many centuries without war, and much social elaboration, up to states. Still, over time agriculture and states went along with more war.

With societal evolution of scale and complexity, preconditions of war proliferated, and war spread. Just before European explorations, the one-two climate punch of the Medieval Warm flipping into the Little Ice Age, c. 1350 A.D., greatly intensified war across the Americas and Pacific basin (at least). With colonialism, Western or otherwise, tribal zone dynamics always transformed, often intensified, and sometimes created war among indigenous peoples – not just in resistance, but in how and why they made war on each other. Pharaonic Egypt expanding into the Southern Levant c. 3200 bc may be the earliest warrified tribal zone, with millennia of peace quickly transformed into a cauldron of war. Violent-ized colonial contact situations are commonly misunderstood as a Hobbesian state of nature.

Wars in expansionist peripheries are fought according to rules and scripts of local culture; and simultaneously embedded in over-all social organization and responsive to immediate local history – like all wars. Take the famed “fierce people,” Yanomami as described by Napoleon Chagnon.4 Men fighting to avenge wrongs or over women is consistent with local values, but neither is predictive of actual war. Antagonistic interests in acquiring new commodities-become-necessities, starting with steel tools, do predict actual war, times of peace vs times of collective violence, who attacks, and who is attacked. Those antagonisms erupt in fights “about” women, revenge, thefts, insults, status, or sorcery. Chagnon’s claim that Yanomami killers have heightened reproductive success is utterly refuted. Yanomami warfare is not Darwinian.

Until recently and for two decades, I researched in the chimpanzees literature. (My current work is on the origins of gangsters in New York City.) In primatology it is held as fact that male chimps innately tend to war-like behavior: patrolling boundaries, sneaking into neighbors’ territory; and if several of them catch a solo stranger male, they kill it. Theoretically, this reduces competition for resources and females.

I reach very different conclusions in Chimpanzees, War, and History. By examining each and every reported instance of deadly violence within its historical context, the book empirically substantiates that human disruption leads to killing, notwithstanding pronouncements that this view is archaic political correctness, dead and buried. In fact, intergroup adult killing is rare, and almost always occurs where violence is directly connected to local human impact.

A second hypothesis is that other killings of infants and within-group adults, are political: display or payback, which occurs in circumstances often but not necessarily connected to human disturbance. People and chimps cannot share an urge to kill inherited from our last common ancestor, because chimpanzees don’t have it. They and bonobos, like humans, are flexible and adaptable in social relations.

Yet two unbridgeable gulfs separate what chimps do from human warfare, two essential contrasts. These categorical differences add species-specific framing to my long developed general theory of war – part systemic and causal, part cognitive and agentic.

As a cultural materialist, I sort cultural phenomena into three dimensions. Infrastructure: people as physical beings, including demography, technology, labor, and ecology. Structure: people as social beings, including social, economic, political, and military institutions and relations. Superstructure: people as conscious beings, with normative world views, histories, symbols, beliefs, values, and emotions. Theoretically, these dimensions comprise a nested hierarchy of progressively more limiting constraints, framing more specific fields of causal autonomy, with systemic interactions and feedbacks within and across dimensions, leading to probabilistic outcomes that are highly responsive to particular local history and circumstances.

This paradigm applies to war in many ways. In social evolutionary perspective, it addresses the beginnings of war, and why egalitarian mobile foragers generally don’t make war. Holistically applied, the paradigm clarifies exactly how Western contact transformed some Yanomami, from their subsistence to world view, making them seem “fierce.” Cross culturally, it organizes systematic comparison, as in the consequences of war across Amazonia; and war and society among ancient and medieval states and as compared to non-state peoples. That comparison highlights emergent Structural differences of state militarism – compulsion, armies, logistics, policy, and dedicated social institutions usually seeking more resources and control. The casual paradigm is expandable, as recently done to address issues of masculinity and war.

The other side of my general theory – and the second essential contrast with chimpanzees – is cognitive and agentic, relating to decision-makers’ perceptions and beliefs that lead to war. Decisions express an essentially human duality: universal practical self-interest, and highly particular local understandings. Egocentrically, both refract through prisms of internal social position – what external posture works for me, including how I’m doing at home? In war as in all life, people are practical, but within powerful normative constraints. Thus, across tribal zones, indigenous war patterns are practically similar, but within entirely different symbolic and moral worlds. When war seems advantageous for those with influence or power, it is justified in terms of local cultural values. Perceived self-interest and norms come together, through what I call moral conversion.

I took this general perspective to modern civil wars, what are misleadingly labeled ethnic or sectarian. They are not about folk custom or theology, but about politics and power. I label them identerest. The neologism avoids common-language, primordialist implications and indicates a complex fusion of identities and interests, in recently constructed identerest groups, led by self-serving identerest entrepreneurs, who promote identerest polarization and violence to advance their own interests. They manipulate endlessly variable combinations of ethnicity, region, tribe, lineage, religion, class, generation and gender, and drape them all in poisonous historical narratives replete with grievance, invoking deeply powerful identity symbols. They weaponize the sense of self. Think Yugoslavia, Rwanda, Rohingya, Trump, Putin.

My goal here is brevity, a 15 minute opinion piece. So, I will close with an earlier condensation of my topical findings, “Ten Points on War,” (which applied to the U.S. wars of the 2000s).

  • #1 Our species is not biologically destined for war.

  • #2 War is not an inescapable part of social existence.

  • #3 Understanding war involves a nested hierarchy of constraints.

  • #4 War expresses both pan-human practicalities and culturally specific values.

  • #5 War shapes societies to its own ends.

  • #6 War exists in multiple contexts.

  • #7 Opponents are constructed in conflict.

  • #8 War is a continuation of domestic politics by other means.

  • #9 Leaders favor war because war favors leaders.

  • #10 Peace is more than the absence of war.

After recent work on masculinity and war, I add two.

  • #11 When war exists, gender roles and schema are adapted to war making.

  • #12 War shapes masculinity and masculinity shapes war.


The original essay was prepared for presentation at Sciences Po Kuwait Program: The Stakes of Peace and War: Diplomacy, Anthropology, Climate and Conflict, Paris, March 5, 2020.


Theoretical elaboration and supporting evidence are provided in my publications, which are available as pdfs on my webpage, except for Yanomami Warfare: A Political History, and Chimpanzees, War, and History: Are Men Born to Kill?,


Fry, D. (2012) Life Without War. Science, 336: 879–884. Fry, D. (2021) Societies within peace systems avoid war and build positive intergroup relations. Humanities and Social Sciences Communications, 8(17): 1–9.


Chagnon, N. (1968) Yanomamö: The Fierce People.

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