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Fowler: Altruistic punishment and the origin of cooperation

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Fowler. 2005. Altruistic punishment and the origin of cooperation. Proceedings of the National Academy of Sciences.

In Brief

Altruistic punishment refers to my willingness to inflict a costly sanction on somebody, even if their offense was not specifically targeted at me.

Using evolutionary game theory, Fowler shows that it would be feasible for altruistic behavior to evolve under the given conditions. The question isn't why the behavior emerges, but why it persists.

The game is not a prisoner's dilemma. It is a stag hunt with an exit option. Either I hunt alone for rabbit or with the group for a stag.

Main Point:

Recent evidence shows humans are willing to engage in altruistic punishment, voluntarily paying the cost to punish non-cooperators. But if altruistic punishment provides benefits for non-punishers and is costly to punishers, how could it have evolved? Fowler creates an evolutionary model that shows how an altruistic punisher can enter a system and soon dominate the population. Punishment can only enforce pay-off improving strategies though, unlike the folk theorem conclusion.


In a large population individuals have a choice between cooperating for a public good or defecting and trying to get that good on their own. Instead of joining a hunting group to get a woolly mammoth individuals can pursue rabbits on their own. Evolutionary models show that if the benefits of cooperation can be seen to be greater than the individual effort payoff, individuals in the system will begin to compare their own payoff to that of others (Fowler uses a common algorithm for this comparison process) and then choose the higher payoff choice, cooperation. But as this group gets too large, free riders start to enter the system.

If a single altruistic punisher is introduced into the system (perhaps a random mutation), the payoffs for individual participants in the system will change such that the system will trend towards all punishers.


Altruistic punishment can be evolutionarily favorable. Fowlers model shows how this can theoretically be the case. This speaks to the Fehr and Fischbacher piece on social norms by providing a theoretical explanation for its maintenance in the population.