More specifically, males that exhibited long-term aggressive behavior towards females, up to and including physical assaults, significantly increased their chances of mating with them at a later date.
Researcher Ian Gilby, an evolutionary anthropologist at Arizona State University, sounded slightly saddened by the findings. “It is certainly not a happy message”, he said.
Chimpanzees’ bullying: Increasing chances of fatherhood
“Males who directed aggression toward females at high rates were more likely to sire those females’ offspring than less violent males were. This effect was particularly strong for high ranking males [in the chimpanzee community],” Gilby added
Although chimpanzees are genetically closely related to humans, researchers were careful not to make sweeping conclusions on sexual violence in society.
Scientists worked in the Gombe National Park, Tanzania, from 1995-2011. They collected data on mating patterns and analyzed fecal matter in order to determine the paternity of 31 babies born over the course of the study.
According to Anne Pusey, an evolutionary anthropologist at Duke University, “the hypothesis is that females are intimidated by long-term aggression from the male so that they acquiesce or even solicit mating from the male when they are fertile, and avoid mating with other males in his presence for fear of further aggression from the male.”
The males used a variety of different behaviors to intimidate the females, including biting and striking them, which sometimes resulted in wounds. On other occasions the males would charge at the females and strike nearby foliage.
Chimpanzees’ bullying: A long process
The researchers have specified that the bullying did not immediately lead to mating, but rather a slow accumulation of aggressive behaviors over the period of two or three years influenced future mating patterns.
After experiencing male aggression for a sustained period of time, females actively looked to mate with those males that had subjected them to aggressive behaviors when they reached their time of peak fertility.
The scientists were quick to point out that the human-chimp evolutionary lineage separated around 7 million years ago.Scientifically speaking the mating systems of the two species are very distinct, despite the recent worrying trend towards sexual violence as a device for picking up women.
“Nevertheless, recognising the adaptive value of male-female aggression in chimpanzees may inevitably help us to understand, and hopefully prevent, similar behaviour among humans”, Gilby said.