Examined Lives: The Execution Hypothesis and the Evolution of Morality (Session 31)


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In his 2019 book The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution, Harvard anthropologist Richard Wrangham first distinguishes between reactive and proactive aggression. Reactive aggression is “hot” and impulsive; proactive aggression is “cold” and premeditated. Homo sapiens are low in reactive aggression, but high in proactive aggression. The execution hypothesis posits that reactive aggressive traits were selected against by targeted proactive aggression.  That is, coordinated proactive aggression eliminated “bullies” and “tyrants” in hunter-gatherer groups. This resulted in both self-domestication and docility (as reactive aggression was selected against) and morality (i.e.,conformity to group norms of altruism and cooperation to avoid the fate of the “tyrants.”)

Parochial altruism is the propensity to direct prosocial behavior toward members of one’s own group to a greater extent than toward those outside one’s group.

One book review summarized Wrangham’s execution hypothesis by saying:

“Wrangham challenges the popular hypothesis of parochial altruism as a possible venue that might have shaped … morality and cooperation. [The] parochial altruism hypothesis … does not explain why [reactive] aggression was reduced …  Parochial altruism is not present among hunter-gatherers [or chimpanzees]. It, therefore, cannot be the evolutionary reason for moral and cooperative behavior in groups.  Instead, Wrangham supports the execution hypothesis claiming that the selection against aggressivity occurred by coalitions cooperating and coordinating in killing the most antisocial individuals. … No other animal has experienced this pressure because only humans have developed complex linguistic abilities which in effect brought about the importance of gossip and moral behavior. If somebody was deemed as immoral or not following the norms established by the ruling coalition, he or she could be easily killed by the overwhelming power of a coordinated coalition able to punish the trespasser. Such a pressure made humans self-domesticated, making them more cooperative, more friendly, and less aggressive as a by-product of the self-imposed selection for docility. Executing aggressive alpha males then lead to the emergence of egalitarian hunter-gatherer societies.  Drawing on research into the evolution of morality, Wrangham expects group-directed moral behavior to be primarily about self-protection, parochial group benefits being only by-products that occasionally stem from it. In this sense, human morality evolved as a response to the fear of capital punishment imposed by the ruling coalition of men, which also explains why humankind has evolved the most complex group-related moral emotions."

Primary resource:

1. Participants are strongly encouraged to read Wrangham’s 2021 Ethics and Politics journal article  "The Execution Hypothesis for the Evolution of a Morality of Fairness”  (16 pages). The execution hypothesis may seem outlandish at first blush, so a good understanding of Wrangham’s arguments and evidence is essential for a fruitful discussion.

Other Resources:

2. April 6, 2019 Harvard Talk by Wrangham on YouTube, especially from minute 39:44 to 53:15 (about 14 minutes). The full talk is about 50 minutes (excluding the Q&A) and covers the entire book; the 14-minute section noted above discusses the execution hypothesis.

3. British Journal for the Philosophy of Science Book Review of The Goodness Paradox

4. New Yorker Book Review: Did Capital Punishment Create Morality?