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Equation 15 · Part 1 · Why We Punish Strangers: The Evolution of Human Cooperation

Symbol w_p

wp<cw_p < c
wpw_p

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wpw_p is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

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wpw_p is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

The passage around this formula

which falls as the residual pool of defectors, 1 - x - y , shrinks. Once a group happens to reach a state where wp<cw_p < c. punishing costs less at the margin than plain, unpunishing cooperation does, and ordinary within-group selection stops working against the punishing type in that group. If groups that reach this state also out-compete or out-reproduce groups that never do — amplified, the authors argue, by cultural transmission mechanisms such as conformist imitation of locally common strategies, which are not available to purely genetic evolution — group-level selection can carry punishment, and the large-scale cooperation it sustains, to frequencies individual selection alone…

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