killing comes naturally to these humanzees because the females prefer high-status aggressive males as mates..,

npr |  Although he adheres to the chimps-as-natural-born-killers theory in the book Demonic Males — finds cause for optimism when it comes to the ability of humans to change their own violent tendencies.

In observing bonobos (the closely related but less-violent cousins of chimpanzees), Wrangham observed peaceful communities based on a power-sharing arrangement between males and females. Chimps, by contrast, live in patriarchal groups where dominant males run roughshod over compliant females.

The reason for the difference, he concludes, is sex selection. Female chimps select aggressive males as mates; female bonobos don't.

"The example of the bonobos reminds us that females and males can be equally important players in a society," Wrangham is quoted in Harvard Magazine as saying. "And by giving us a model in which female action works in suppressing the excesses of male aggression, the bonobos show us that in democracies like our own, women's voices should be heard more than they are."