Barbara J. King at the TLS:
What was the driving force that made us human, akin to but separate from other apes and our evolutionary cousins such as the Neanderthals? In The Goodness Paradox, the anthropologist Richard Wrangham approvingly quotes Frederick the Great in pointing to “the wild beast” within each man: our nature, he argues, is rooted in an animal violence that morphed over time to become uniquely human. When male human ancestors began to plot together to execute aggressive men in their communities, indeed to carry out such killings through what Wrangham calls “coalitionary proactive aggression”, they were launched towards full humanity.
Proactive aggression is premeditated, a feature that sets it apart from reactive aggression, which is impulsive, a response to some immediate threat. Hot emotion drives reactive aggression: someone insults you and you respond with a swing at their jaw.