Disagreement over war-like behaviour in the species centres on the role humans play in fuelling chimpanzee violence. One line of thought claims that warfare is spontaneous, allowing competitors to be killed and increasing access to food and mates. Another holds that human encroachment on chimpanzee habitats leads to warfare, as food provisions are disrupted.
New research holds that the role of human activity on chimpanzee wars has been overplayed and the study is a direct response to claims otherwise. ‘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,’ said lead researcher Michael Wilson from the University of Minnesota.
‘Humans have long impacted African tropical forests and chimpanzees, and one of the long-standing questions is if human disturbance is an underlying factor causing the lethal aggression observed,’ said co-author David Morgan, who has studied chimpanzees in the Republic of Congo for 14 years.
The research brought together 30 ape experts who looked at 50 years of studies from 18 chimpanzee communities, each with varying degrees of human influence. Central to the research was a pattern analysis of 152 chimpanzee killings. The majority were found to be male-on-male attacks, a pattern consistent with adaptive fitness behaviour rather than human influence.
‘Wild chimpanzee communities are often divided into two broad categories depending on whether they exist in a pristine or human-disturbed environments,’ added Morgan. ‘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 affect the rate of killing among communities.’
Although chimpanzee communities are divided between those with human contact and those in pristine conditions for research purposes, human interference can occur at any time. Despite this, the research found that human impact did not predict the rate of killing among communities.
‘The more we learn about chimpanzee aggression and factors that trigger lethal attacks, the more prepared park managers and government officials will be in addressing risks to populations, particularly with changing land use by humans in chimpanzee habitat,’ said Morgan.