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It's not just man that wages war - chimpanzees do too.

Research has discovered that the apes are inherently violent, with males in particular proving to be the most aggressive of the sexes.

The study suggests that violence has deep evolutionary roots, and is not a modern man-made phenomenon.

Researchers from the University of Minnesota studied 18 chimp and bonobo communities over a period of 50 years. The communities experienced varying degrees of human interaction. Researchers discovered 152 instances of killings by chimpanzees, and the majority of violent attackers, and victims of attack, were male

Of all of the world's animals, humans and chimpanzees are among the few to engage in attacks on other members of their own species.

Primatologists and anthropologists have debated the concept of warfare for decades, with some saying increased gains and benefits of killing off competitors opens up access to key resources such as food or mates.

In contrast, others have argued warfare is a result of human impact on chimpanzees - such as habitat destruction or food provisioning - rather than adaptive strategies.

But the latest research by ape experts at the University of Minnesota has found that lethal violence between chimps indicates this is normal adaptive behaviour - and not one that has emerged in response to humans.

A team of 30 researchers studied 18 chimp and bonobo communities over a period of 50 years.

The communities experienced varying degrees of human interaction and influence.

Researchers discovered 152 instances of killings by chimpanzees. 

The key findings indicate that a majority of violent attackers, and victims of attack, were male. 

This information is consistent with the theory that these acts of violence are driven by adaptive fitness benefits, rather than human impacts. 

There was only one suspected killing in four bonobo communities compared to the 152 in 15 chimp communities.

Variation in killing rates was unrelated to human contact, but did increase in larger populations and groups with a high number of males. 

Michael Wilson, of Minnesota University who has studied chimps deep in the Congo forests for 14 years, said: 'This is an important question to get right.

'If we are using chimpanzees as a model for understanding human violence we need to know what really causes chimpanzees to be violent.'

Dr Morgan added: 'Wild chimpanzee communities are often divided into two broad categories depending on whether they exist in pristine or human disturbed environments.

The findings are consistent with the theory acts of violence among chimpanzees, and in particular males, are driven by adaptive fitness benefits, rather than human impacts. Variation in killing rates was unrelated to human contact, but did increase in larger populations and groups with a high number of males

'In reality however human disturbance can occur along a continuum and study sites included in this investigation spanned the spectrum. 

'We found human impact did not predict the rate of killing among communities.

'The more we learn about chimpanzee aggression and factors that trigger lethal attacks among chimpanzees the more prepared park managers and government officials will be in addressing and mitigating risks to populations particularly with changing land use by humans in chimpanzee habitat.'

Professor Joan Silk, of Arizona State University, reviewed the results for the journal and said they should put the debate to rest - but will 'probably not be enough to convince everyone.' 

The findings are published in Nature