Turns out that not all of the bad things in the world are the fault of humanity. A new study published this week in Nature shows that murder among chimpanzees isn’t related to human activities, as some researchers theorized.
Previously, scientists had speculated that chimpanzees' murderous behavior was related to humans interfering in the chimpanzee community, either by facilitating habitat loss or altering feeding patterns, pushing the chimpanzees to the murderous brink.
But really, it’s not all about us.
The many researchers (30 are listed as authors) compiled observations made on 18 chimpanzee groups over the course of fifty years. They found 152 murders—58 of which scientists witnessed first-hand. Most of the killers and victims were males, and usually the victims were killed by multiple assailants—the median ratio of killer to soon-to-be-corpse was 8 to 1.
The BBC reports that the frequency of killings didn’t seem to be dependent on human interference at all:
Instead, it was basic characteristics of each community that made the biggest difference: the number of males within it, and the overall population density of the area.
These parameters link the violence to natural selection: killing competitors improves a male chimp's access to resources like food and territory - and crucially, it will happen more frequently when there is greater competition from neighbouring groups, and when the males can patrol in large numbers, with less risk to their own survival.
The researchers also looked at the rates of bonobo on bonobo crime in four groups over the same period of time and found only one incident of suspected murder. Apparently, bonobos live up to their peaceful reputation.