Across psychology, archaeology, and evolutionary biology, a growing body of peer-reviewed evidence is dismantling one of the oldest assumptions about human nature: that people are hardwired for violence. New work from the University of Lincoln in the United Kingdom, led by Callum Thomas, directly challenges the idea that humans evolved to be uniquely aggressive or inherently more likely to kill rivals. As the Lincoln team notes in its recent overview, the traditional “killer ape” narrative is increasingly hard to square with the data emerging from skeletal remains, comparative mammal studies, and modern behavioral genetics.
Ancient Bones Tell a Different Story
One of the strongest lines of evidence comes from a large-scale bioarchaeological analysis in Nature Human Behaviour that assembled a long-run dataset of cranial trauma and weapon-related wounds from excavated skeletons across the Middle East. Spanning roughly 12,000 to 400 BCE, the sample covers the transition from mobile foraging to settled agriculture and early states. Instead of a flat, unchanging pattern of brutality, the researchers found that rates of lethal and non-lethal violence rose and fell sharply over time and varied by region.
Some eras were relatively peaceful, with low levels of skeletal trauma; others saw spikes associated with social upheaval or political consolidation. That variability matters because it cuts against the claim that lethal aggression is a stable trait baked into human biology. If violence were truly innate and constant, trauma rates should look broadly similar across millennia and geographies. They do not. The record instead suggests that external conditions (resource stress, emerging hierarchies, trade networks, and population density) shaped when and where violence surged.
This perspective aligns with social-scientific work summarized by psychologists who argue that shifting norms, institutions, and incentives are powerful drivers of aggression. As one analysis of the evidence on human violence notes, the historical record increasingly points to behavior that is “highly responsive to external influences rather than an inherent predisposition.”
Humans Are Not Outliers Among Mammals
Another pillar of the “naturally violent” view is the idea that humans stand out among mammals for killing their own kind. A comparative phylogenetic analysis in Nature directly tested that claim by estimating the proportion of deaths caused by same-species lethal violence across hundreds of mammal species, then using evolutionary relationships to infer a baseline expectation for humans. The result, around 2% of deaths, places humans squarely within the range predicted by their lineage, not dramatically above it.
Crucially, the study compared this phylogenetic baseline with actual rates observed in archaeological, historical, and ethnographic records. In some contexts, such as certain early states or periods of intense warfare, human lethal violence exceeded the 2% expectation. In others, including many small-scale societies and modern nation-states with strong institutions, it fell well below. The pattern is not one of uniformly high aggression but of wide swings depending on social organization, governance, and cultural norms.
Building on this work, a synthesis in Theory and Society argues that the long-run trajectory of violence is best described as an “inverted U.” Violence appears to have risen with the emergence of agriculture, property, and early political complexity (when there was more to fight over and fewer constraints on rulers) before declining again under different institutional arrangements, such as more centralized states, legal systems, and international norms. Rather than a straight line from savagery to civility or a flat line of constant brutality, the evidence points to a contingent, non-linear curve.
Feuds, Not Wars, Among Foragers
Popular accounts often lean on images of prehistoric hunter-gatherers locked in perpetual tribal warfare. To test that assumption, a cross-cultural study in Science examined lethal events specifically among mobile forager band societies. The authors carefully coded cases as homicides, feuds, accidents, or organized war. Most incidents turned out to be personal disputes, revenge killings, or intra-group conflicts rather than coordinated raids between distinct groups.
This distinction matters because it challenges the notion that warfare is a default human condition. Small-scale violence among foragers, while real and sometimes devastating, does not automatically equate to organized war in the modern sense. Ethnographic work by Douglas Fry and colleagues, including studies of nomadic bands, reinforces this point: projecting contemporary state-level warfare backward onto small, flexible groups distorts both the archaeological and anthropological record.
These findings do not imply that foragers were peaceful utopians. Rather, they show that the forms violence takes are deeply shaped by social scale and structure. When there are no standing armies, permanent fortifications, or large stores of wealth, lethal conflict tends to revolve around interpersonal grievances and small coalitions, not massed battle lines.
The Nataruk Debate Shows Science in Action
Some of the most dramatic evidence cited for ancient warfare comes from the roughly 10,000-year-old remains at Nataruk in West Turkana, Kenya. The original research team, writing in Nature, described multiple individuals with severe cranial and skeletal trauma, including embedded stone points, and interpreted the site as a snapshot of inter-group conflict among foragers. The image of bound, battered bodies left unburied on a lakeshore quickly entered public debates about human nature.
However, a subsequent brief communication challenged several pillars of that interpretation. The critics questioned whether all the remains were truly contemporaneous, raised doubts about the claim that the individuals had been intentionally left unburied, and argued that the trauma patterns did not unambiguously indicate warfare rather than, for example, episodic interpersonal violence or other catastrophic events. The back-and-forth over Nataruk illustrates how high-profile finds are subject to rigorous scrutiny, and how interpretations of early violence can shift as new analyses emerge.
For the broader question of whether humans are “naturally” warlike, the key point is not that Nataruk shows no violence. It clearly does. But even in one of the most cited cases, the leap from lethal conflict to organized warfare is contested. The evidence for systematic, large-scale war among Pleistocene and early Holocene foragers remains more ambiguous than many headlines suggest.
Genetics Offers No Simple “Violence Gene”
If humans were biologically programmed for aggression, one might expect geneticists to have identified clear molecular culprits by now. Yet systematic meta-analyses in Molecular Psychiatry found that decades of candidate-gene studies on aggression and related traits failed to produce robust, replicable associations. Early excitement about specific variants (sometimes sensationalized as “warrior genes”) has largely faded as larger samples and stricter methods revealed inconsistent or negligible effects.
Behavioral genetic studies using twin and adoption designs do indicate that roughly half of the variation in aggressive behavior can be attributed to genetic influences in both children and adults, as summarized in reviews for the National Institutes of Health. But that heritability appears to be highly polygenic and context-dependent. Thousands of variants of tiny effect interact with environments ranging from childhood adversity and social inequality to cultural norms and legal sanctions. Genes shape sensitivity, temperament, and impulse control, but they do not dictate a fixed level of violence.
Extreme cases underscore this complexity. The 2021 review of the Las Vegas mass murderer Stephen Paddock, cited in the University of Lincoln’s discussion of aggression, noted that no clear abnormality was found in his brain, and the authors suggested that a definitive biological explanation may never emerge. Such tragedies highlight that focusing narrowly on individual pathology or hypothetical “killer genes” risks obscuring the broader social, psychological, and situational factors that enable violence on a large scale.
Rethinking “Human Nature”
Taken together, these strands of evidence do not paint a picture of humans as saints. People are clearly capable of cruelty, organized killing, and atrocity. But they also show remarkable capacities for cooperation, empathy, and restraint. The archaeological record reveals long stretches of relative peace; comparative mammal data place humans within an expected range rather than off the charts; forager studies emphasize feuds over formal wars; and genetics offers no simple blueprint for bloodshed.
What emerges instead is a view of violence as a flexible, context-sensitive part of human behavior, one that can be amplified or dampened by institutions, inequality, norms, and opportunities. That conclusion is less dramatic than the claim that we are doomed by our biology, but it is far more consistent with the data. More importantly, it carries a different moral and political implication: if violence is not fixed by nature, then changing the conditions that foster it is not only possible, but essential.
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*This article was researched with the help of AI, with human editors creating the final content.
