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Evolved altruism levels for different green beard thresholds. Plotted is the average number of donations executed per organism for different threshold values (T) of the donate-threshold-gb instruction (averaged from the final populations of 50 trials per treatment ±1 s.e., often too small to distinguish). Organisms evolved to perform enough donations to surpass the threshold and thus qualify to receive altruism, but did not perform substantially more than T donations.
