Sexual aggression in primates between males and females may be hardwired, and even be selected for through evolution. Researchers have found that male baboons that frequently harass, attack, and assault females are most likely to mate with them and have offspring, raising the possibility that this behavior is in effect encouraged.

It is not unknown for male primates to coerce, or in some cases force, females into having sex. Young male orangutans that are not yet old or strong enough to hold their own territories have been found to patrol the rainforest until they come upon a female on her own, where he will basically rape her. Male chimps also aggressively coerce females into mating.

It has always been a bit of a curiosity as to why males of promiscuous primate species tend to act aggressively towards members of the opposite sex, with a few alternate theories trying to explain it. Females of these species tend to have obvious signs such as swelling, indicating that they are fertile and ovulating, and try to encourage as many males to mate with them as possible.

As a limited resource, it has often been thought that the ovulating females held all the cards. But it may be that the females have less choice than was previously thought. “This study adds to growing evidence that males use coercive tactics to constrain female mating decisions in promiscuous primates, thereby questioning the extent of sexual freedom left for females in such societies and suggesting that sexual intimidation has a long evolutionary history in primates,” explained Alice Baniel, who conducted the study published in Current Biology.

It turns out that when it comes to male coercion within chacma baboons from Nambia, females that are harassed are more likely to then choose their attacker to mate with than other males that leave them alone. This makes the aggressive primates more successful than their mellower troop mates, and thus could be an indication that the behavior is selected for. Why the females put up with this is still not known, but the researchers speculate that they may go along with the confrontational males due to fear of injury if they refuse.

The team suggests that because this behavior is present in a range of different species of primates, it might be hardwired into the group. As apes ourselves, they then go on to float the notion that it may be playing a role in our behavior too, though other primatologists have countered, saying that implying this from the research carried out on baboons, however scientifically sound the study is, might be stretching the data a little too far.