New primate study challenges assumptions about human violence

A new primate study challenges a longstanding assumption about violence.

For decades, researchers, philosophers and politicians have debated whether violence is inherent in humans or chiefly shaped by environment and upbringing. An international research team has now examined evidence from the primate world and reached a finding that casts doubt on many simple answers.

The old idea: a straightforward scale from conflict to killing

A familiar picture holds that violence starts with a shove, progresses to a slap and then a punch, and, if the spiral continues, can ultimately end in death. On this view, violence resembles a dial: turn it up far enough and everyday aggression becomes extreme horror.

The researchers are now taking that picture apart. They argue that it oversimplifies both the biological and social realities.

The new study suggests that frequent minor disputes do not automatically mean a species is prone to lethal violence.

Many theories have long treated aggression as a single trait. If an animal species frequently scuffles and makes threatening noises, the reasoning goes, it must also resort to more extreme measures more often. Plausible as that sounds, the latest analysis finds that the data do not support it.

The study: comparing 100 primate species

The team, led by evolutionary biologist Bonaventura Majolo of the University of Lincoln, looked beyond humans to the wider primate family: monkeys, apes and ourselves.

For 100 species, the researchers gathered behavioural data on five distinct forms of aggression, including:

• Frequent, non-lethal conflicts in everyday life
• Attacks within an individual's own group
• Violence between different groups
• The killing of adult rivals
• The killing of young animals, or infanticide

The team wanted to establish whether these behaviours rise together along a shared scale of aggression, or whether, biologically speaking, they follow separate paths.

A surprising finding: severe violence breaks the pattern

The analysis revealed a clear pattern: species with frequent minor clashes do not necessarily display high levels of severe, lethal violence. In reality, the supposed scale running from harmless behaviour to extremes breaks down.

Lethal violence appears to follow its own rules, rather than simply representing the highest point on a general scale of aggression.

Some types of lethal aggression do show a moderate relationship with one another. Species in which infanticide occurs, for example, sometimes also display other extreme behaviours. In most cases, however, there was no direct link with everyday disputes.

The researchers believe these patterns indicate that different forms of aggression can arise in different ways and develop independently.

What the findings do and do not say about humans

The study does not seek to declare humans “peaceful”. Instead, it calls for a more precise view. In this light, the question “Are we violent by nature?” is too narrow.

If everyday conflict and extreme violence rely on different biological mechanisms, a general league table of “aggressive species” makes little sense. The researchers explicitly warn against such rankings.

It is not meaningful to rank humans according to how “aggressive” their species is overall. The background to everyday disputes is fundamentally different from that of mass violence.

For public debate, this means that jumping from a rough culture of argument to an allegedly “brutal nature” of human beings overlooks crucial differences. Crossing the threshold to killing appears to require particular triggers and conditions, not merely a little more everyday anger.

How social structures shape primate aggression

The researchers place particular emphasis on lifestyle and environment. Primate species differ greatly in the ways they live together:

• Some have strict hierarchies with clearly defined ranks.
• Others form loose associations with shifting alliances.
• Still others live largely solitary lives and rarely encounter members of their own species.

These differences affect when and how conflicts escalate. Groups with a fixed hierarchy may experience frequent minor jostling and threatening gestures without anyone being seriously injured. Both the rules and the boundaries are clear.

Lethal violence is more likely where competition is exceptionally intense, for example over scarce food, desirable territories or reproductive partners. What matters in those circumstances is not whether a species generally appears “quarrelsome”, but whether particular conditions make it more likely to cross a dangerous threshold.

Biology alone cannot explain human violence

The data suggest that human violence cannot simply be inferred from the animal world. Genes and evolutionary history provide only part of the puzzle.

Culture, legal systems, social norms, economic conditions and political structures are at least as important. They can restrain extreme violence or, in the worst cases, organise it, as in wars, genocides or gang crime.

The study therefore suggests viewing violence less as an innate constant and more as the product of complex interactions between:

• Biological predispositions
• Social structures and power relations
• Economic pressure and scarce resources
• Norms, upbringing and legal frameworks

Why everyday disputes are not automatically dangerous

There is also a practical implication for daily life: if low and high levels of aggression do not sit on a simple scale, we can rethink how we handle conflict. An argument between partners, a heated office debate or a shove on the Underground is not, in itself, a warning of an outbreak of extreme violence.

Many forms of aggression help establish boundaries, clarify status or negotiate access to resources without anyone suffering serious harm.

Among primates, humans included, a controlled and limited confrontation can even relieve tension. The crucial question is how groups manage such conflicts: are there rules, mediators and ways to step aside? Or do frustration and inequality build up until they erupt?

What researchers mean by “aggression”

In everyday speech, aggression can suggest a “bad character” or someone who is “malicious”. In behavioural biology, the term is more neutral: it covers any deliberate action that harms, or is intended to harm, another individual, from a threatening look to a lethal attack.

The study shows that these actions are better divided into types than placed under one umbrella. In practical terms, preventing violence requires different approaches for different forms:

• For everyday conflicts, clear rules, communication training and fair structures can help.
• For organised, lethal violence, power, ideology and systematic dehumanisation play a larger part.

Treating both as the same thing means missing opportunities for prevention. Programmes that improve how people argue will not by themselves prevent a civil war. Measures against crime do not automatically put an end to bullying in school playgrounds.

What this means for policy and society

A more nuanced perspective opens up new possibilities for policy and prevention. If lethal violence is not simply an “escalated form” of everyday anger, different problems need different responses.

Governments can, for instance, target conditions that fuel extreme violence: high inequality, uncontrolled access to weapons, militias that glorify violence and toxic ideals of masculinity. At the same time, education and the media can encourage a constructive culture of disagreement that channels aggression into harmless outlets rather than making it taboo.

The new study also offers a hopeful perspective: if violence is not a fixed feature of human nature, there is more room for change. Biology may set limits, but it does not determine how societies must deal with conflict.