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SCIENCE! has given us a glimpse into the possible origins of the renowned human female mate preference for jerkboys of varying jerkitude.

Male sexual aggression: What chimps can reveal about people

Male chimpanzees that wage a campaign of sustained aggression against females sire more offspring than their less violent counterparts, new research finds.

The results suggest that such nasty behavior from males evolved because it gave the meanest males a reproductive advantage, said study co-author Ian Gilby, a primatologist at Arizona State University in Phoenix.

This chimpanzee behavior could also provide some insight into the roots of sexual aggression in men.

“It is possible that in our early ancestors there may have been an adaptive value to male aggression against females,” Gilby said.

Chimps aren’t the only closest living ape relatives of humans (bonobos and gorillas are the others), but their present-day characteristics could help shed light on deeply embedded human sexual behavior that is resistant to shorter term cultural or ecological changes.

But sexual aggression in male chimpanzees isn’t directly parallel to rape, because it typically takes place at times distant from copulation. Female chimps also mate with multiple males anyway, Gilby said..

To understand the roots of this behavior, Gilby and his colleagues recorded instances of male-on-female violence in a troop of chimpanzees living in Gombe Stream National Park in Tanzania. The researchers studied violence that occurred both when the females were sexually receptive, or swollen, and when they were not. The team then compared that information with paternity tests on all the offspring born since 1995.

Chimps have a strict male dominance hierarchy, and more-dominant males generally engage in a greater amount of gendered aggression. But even when taking this into account, the team found that aggression increased a male’s chances of siring offspring — regardless of whether the chimp was more or less dominant.

The sustained intimidation in which chimps engage, which has some parallels to human behaviors such as stalking or domestic violence, is a form of mate guarding. The behavior may make female chimps less likely to sneak off with a partner of her choosing during her most fertile times, Gilby said.

So male aggression isn’t primarily about coercing sex from females. It’s a mate guarding strategy, similar to the violence that lunkhead alpha human males may occasionally visit upon their in-demand hottie girlfriends (cf., Chris Brown). And according to this study, that mate guarding aggression has a genetic payoff, so it would be selected over genes for “niceguy” supplication and everlasting tenderness.

Obviously, this isn’t the whole human story, as niceguys are still with us, and women don’t fall for jerks all the time every time. But there is clearly an observable female preference for jerkboys that has no parallel in a male preference for jerkgirls. Think of a jerkboy bell curve, and place women on it. At the far left, you find good girls who never go for men with even a hint of jerkish characteristics, in the middle are the majority of women who like their men best when they exhibit some jerkboy flair, and at the far right of the bell curve are your women who fall in love with serial killers and prisoners.

There is no such equivalent bell curve for men.

The study explains why men might have evolved a taste for flashing gang signs of intimidating assholery upon lovers, but what about women’s taste for receiving that assholery with open legs? One can surmise that a “jerkboy gene” which improved men’s reproductive fitness (in an environment where reproduction wasn’t thwarted by cheap and easy contraception) would, over generations, ride sidesaddle with a “jerkboy loving gene” in women that improved the reproductive fitness of those women who acquiesced to, or even sought out, the very special lessons in love that jerks are fond of teaching. It’s a variant on the sexy sons hypothesis; call it the sexy sonofabitch hypothesis.


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