Why human aggression and lethal violence may have different roots

People often think of violence as a sliding scale: a shove becomes a punch, and a punch eventually leads to something much worse. The idea seems straightforward, even logical.

New research, however, suggests that this assumption may not stand up, at least not in the way people have long understood it.

A closer examination of human behaviour and that of our nearest animal relatives reveals a more complicated picture. The everyday conflicts most people experience do not necessarily point towards extreme violence; they may have entirely different roots.

How aggression really works in primates

For years, scientists have investigated the origins of violence. Is it embedded in us by evolution, or is it shaped by culture and environment?

Many theories have treated aggression as a single trait. Under that view, a species displaying frequent low-level aggression should also have higher rates of lethal violence.

The new research challenges this assumption. It suggests that forms of aggression are not all alike: some may have little in common beneath the surface, even when they initially appear related.

The study was led by Professor Bonaventura Majolo of the University of Lincoln, alongside Dr Samantha Wakes and Professor Marcello Ruta. The team took a broad view of aggression across species.

Rather than studying humans alone, the researchers examined patterns throughout the primate family, including monkeys, apes and humans.

What the data revealed

The team analysed behaviour in 100 primate species, examining five distinct types of aggression. These ranged from everyday conflicts to lethal attacks, including the killing of adult rivals and infanticide.

The findings did not support the usual assumptions. Species that frequently displayed mild aggression were no more likely to engage in deadly violence. The expected connection was absent.

Instead, the data indicated that lethal behaviours tend to follow a separate path, shaped by different pressures and conditions.

Although some forms of lethal aggression were moderately linked to one another, they had little connection with the more common, low-level conflicts.

Rethinking human nature

The findings address a long-running debate: are humans naturally violent, or does our environment shape our behaviour?

“Understanding the evolutionary roots of violence is important not only for biology but also for how we think about human behaviour,” said Majolo, a professor of social evolution.

“Our study shows that the evolution of aggression follows more complex patterns than what earlier models proposed.”

“It is biologically inaccurate to rank species on the basis of their general propensity for aggression and that we need a more nuanced approach when discussing whether humans are inherently violent.”

This view changes the discussion. If everyday aggression and lethal violence are not closely connected, describing a species, or humans, as simply “violent” may miss the point.

Aggression is more complex

Aggression takes many forms. A brief argument, a territorial display and a fight over resources may appear similar, but the reasons behind them can differ significantly.

Social structure plays an important part among primates. Some species live in close-knit groups with clear hierarchies, while others have less rigid systems.

Access to food, mates and territory can all affect behaviour, but these factors do not influence every form of aggression equally.

This helps explain why lethal violence does not simply develop from everyday conflict. It may depend on particular triggers, such as intense competition or specific social pressures, rather than a general tendency towards aggression.

Not all aggression leads to violence

The study lends support to the idea that biology alone cannot explain human violence. Nor can violence be reduced to a simple scale running from mild to extreme behaviour.

Instead, the findings point to a more layered understanding: different forms of aggression may have evolved for different reasons.

Some may help individuals navigate social life, while others emerge in rare and intense circumstances.

The research does not resolve the debate, but it changes its terms. Treating violence as a single trait, it suggests, may lead us in the wrong direction.

A more careful approach that distinguishes everyday conflict from extreme acts could bring us closer to understanding why humans behave as they do.

The full study was published in the journal Evolution Letters.