October 4, 2019

Are Chimpanzees More Aggressive Than Humans?

by Matt Brunette

Aggression in humans has long been an interesting topic for scientists and anthropologists. Back in the 1960s, aggression between different groups was thought to be a uniquely human quality. However, research on our closest living relatives soon revealed that this wasn’t necessarily the case.

Dr. Jane Goodall’s ground-breaking work helped change the way we thought of chimpanzees, and ourselves, when she documented evidence of tool-use, hunting, and inter-group warfare among the chimps of Gombe. Her findings showed the world that chimpanzees can be just as aggressive and violent towards each other as humans. Since then, long-term studies of chimpanzee populations have yielded important findings on the possible origin of this aggressive behaviour.

Dr. Jane first observed chimps using tools. Later on she discovered their capacity for aggression and violence.

Scientists define two broad categories of aggression as proactive and reactive aggression. A key difference between human and chimpanzee aggression is that humans are found to have a greater inclination than other primates for proactive aggression – meaning aggression that is more thought-out or planned. Chimpanzees have been found to more often partake in reactive aggression, though proactive aggression does occur in some groups, particularly in cases of intergroup aggression and warfare.

As our closest living relatives, the similarities and differences between aggression in chimpanzees and humans can have important evolutionary implications about where our aggressive behaviours may have come from. Studying aggression in chimpanzees has therefore been an important topic of discussion among scientists and has resulted in two main opposing hypotheses regarding its origin. The first is that aggressive behaviour in chimpanzees is a naturally evolved behaviour that resulted in a competitive advantage and better reproductive success. The other hypothesis is that aggressive behaviour in chimpanzees is a result of human interference, with the expansion of human settlements and activities reducing chimpanzee habitat and raising the stress and tension of chimpanzee groups living closer together with fewer available resources.

A recent study by a group of primatologists assessed long-term data on aggressive behaviour in chimpanzees to examine which of the two hypotheses was best supported. Their findings indicated that aggressive behaviour in chimpanzees was more related to adaptive strategies, therefore suggesting an evolutionary origin. They believe that aggressive behaviours in chimpanzees likely resulted in benefits that ultimately led to better access to resources and improved the overall evolutionary fitness of the aggressor.

A key thing to keep in mind is that, just like humans, chimpanzees are not always aggressive, and the aggressive behaviours referenced above represent a small portion of daily chimpanzee behaviours. Chimpanzees spend much more of their time grooming, socializing, and foraging for food in non-aggressive ways. Ultimately, it should come as no surprise that our closest cousins are very similar to humans when it comes to aggression and aggressive behaviour.