Humans have more in common with their distant ancestors than previously realized, according to research published Sept. 18 in Nature by University of Minnesota researchers.

While it was once thought that chimps only became aggressive due to lack of resources, new research indicates that chimpanzees have an inclination towards violence which makes them natural-born killers.

Similar to humans, it is often the innocent, weak, or helpless animals who are the victims of this natural aggression. Dwindling resources did not seem to have an impact on chimpanzee violence.

Chimpanzees are our closest genetic relative next to bonobos. However, this aggression has not been observed in the bonobo population; even when human impacts are significant, bonobos do not exhibit violence towards each other.

The study was conducted by University of Minnesota researcher Michael L. Wilson, who collaborated with 29 co-authors all over Africa. The findings compiled five decades’ worth of information regarding simian behavior from from 18 chimpanzee communities and four bonobo communities.

The chimpanzee data is important for understanding how human behavior has evolved. High levels of violence among chimpanzee populations may indicate that early humans had a violent nature as well.

This research overturns a long-held theory that chimpanzees only act aggressively when disrupted by humans or faced with decreased resources. While movies like “Planet of the Apes” show chimpanzees living peacefully until disturbed by people, this doesn’t seem to be the case; they have an ingrained capacity for violence that is independent of human disruption.

Wilson’s research also has long-standing implications for chimpanzee conversation: “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. And for the sake of chimpanzee conservation, if human activities are causing chimpanzees to kill each other, we need to address that.”