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Self-domesticated by violence to be peaceful. And violent

In comparison to other species, humans are both surprisingly peaceful in their day-to-day interactions with unrelated conspecifics and unprecedently violent toward them when the situation requires it. A goodness paradox, as Wrangham (2019) dubs this strange relationship of humankind to violence, is the theme of his latest book attempting to comprise decades of research into a coherent theory of aggressive behavior focused on humans. Drawing on his expertise in primatology, Wrangham presents an evolutionary theory that not only expands contemporary thinking about human behavior but also challenges and refines several crucial notions of human evolution. A central distinction to the theory is that two types of aggression shape human behavior. Reactive aggression urges individuals to violently lash out against and mitigate provocative stimuli, while proactive aggression, on the contrary, allows humans to execute violence accordingly to premeditated plans, often in a ‘‘cold’’ manner, and sometimes on a horrendous scale. What creates the goodness paradox is that humans have a very low propensity for reactive aggression but are able to plan and coordinate aggression in a proactive manner very efficiently. Wrangham points out that the distinction is not a new one as research on aggression converges on this notion since the 1960s, but he engraves it into the evolutionary theory, connecting various findings into a grander explanatory framework. In the first half of the book, Wrangham focuses on the evolution of reactive aggression more closely, as it is the one that is widespread across species. Inspired by Belyaev, Ruvinsky, and Trut’s (1981) famous research on domestication, he lays out how selection for docility resulting in a domestication syndrome is a crucial condition for reducing aggressive reactivity to stimuli. Wild animals tend to be highly reactive and do not have visible features of docility like paedomorphism or increased proclivity to play and sex prolongated into adulthood, all by-products of the domestication syndrome. Wrangham argues that humankind became selfdomesticated and less reactively aggressive around the time it became Homo sapiens and lays out how conditions could have changed for that to happen. His answer is self-domestication—humans domesticated themselves through the punishment of overly aggressive individuals. At this point, Wrangham criticizes that contemporary thinking on human evolution omits the reduced reactivity as a critical point that makes us human. He, therefore, posits that reduced propensity to reactive aggression is at least just as a critical component founding the success of humankind as intelligence, cooperation, and social learning is, if not precursory to all of these standardly acknowledged components. Concomitantly, Wrangham also challenges the popular hypothesis of parochial altruism as a possible venue that might have shaped human aggressivity in relation to morality and cooperation. Parochial altruism hypothesis argues why cooperation was favored, which, however, does not explain why aggression was reduced. Claiming that the hypothesis is not able to explain the group-directed moral emotions and cooperative nature of humankind, he argues that because