Theory 65/Population/Social evolution
Cooperation Needs Assortment
The claim
Cooperation among non-relatives is stable only when the ratio of benefit to assortment exceeds one, so high benefit cannot compensate for random mixing.
01Mechanism
Cooperators must interact preferentially with cooperators; assortment determines how much of the benefit returns.
02Prediction
Cooperation should track the ratio.
03Refutation
Cooperation tracking benefit alone would remove assortment.