connection to individual nghts; we have cut out morality as the governor. This suite of transformations, enabled by our promiscuous brain, allowed us to occupy a unique position within the animal kingdom as large scale killers.
Chimpanzees only kill adults when there are many attackers against one victim, with the vast majority of kills focused on individuals outside of their own group; most kills within the group are aimed at infants, where the costs to the attacker are low. Though humans also kill members of enemy groups when there are many against one —a pattern that is common among hunter-gatherers and other small- scale societies — we depart from this narrow pattern in terms of numbers and the array of potential victims. When humans kill, we go at it with many against many, one against one, and even one against many, including as victims both those outside of our group and those within, young and old, same and opposite sex, and mating partner and competitor.
Add the chimpanzee’s adaptive capacity for coalitionary killing to the promiscuous capacity of the human brain, and we arrive at a uniquely aggressive species, one capable of inflicting great harm on others in any context. Though the modern invention of scud missiles and stealth bombers undoubtedly enriched our capacity to kill on a large scale by putting distance between killers and victims, these weapons of mass destruction were not necessary. Today, we need only travel back a few years to 1994 to witness the machete genocides of Rwanda, a painful memory of our capacity to wipe out close to a million people in 100 days with hand to hand combat. This is excessive harm, enabled by our ability to use denial to minimize the perceived costs of killing another person and to motivate the anticipated benefits. Denial turns down the heat of killing another and turns us into callous predators.
Evolutionary changes in the connections to the brain’s reward system provided a second, cost- offsetting step, allowing us to move into novel arenas for harming others. When an animal wins a fight, the reward circuitry engages, providing a physiological pat on the back and encouragement for the next round. This same circuitry even engages in anticipation of a battle or when watching winners. The reward system is important as it motivates competitive action in situations that are costly. There is one situation, however, where the reward system is remarkably quiet, at least in all social animals except our own: detecting and punishing those who attempt to cheat and free-ride on others’ good will.
Punishment carries clear costs, either paid up front in terms of resources expended on physically or psychologically attacking another, or paid at the end if the victim fights back or retaliates. These costs can be offset if punishers and their group benefit by removing cheaters or teaching them a lesson. Among animals, punishment is infrequently seen in vertebrates, especially our closest relatives the nonhuman primates. When it is seen, the most common context is competition, not cooperation. Like lethal killing, then, punishment in animals tends to be restricted to a narrow context. Like lethal killing, punishment in
animals is psychologically monogamous.
Hauser Prologue. Evilution 13
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