Figure 1.

Evolved altruism levels for different targeting mechanisms. Plotted is the average number of donation instructions per type executed by organisms in the final populations of 50 trials (±1 s.e., often too small to distinguish). The maximum number of donations was capped at 100. (a) Targeting altruism based on kinship was selected for over two controls. (b) Targeting altruism based on high genetic similarity was favoured over targeting based on kinship. (c) Selection did not favour targeting altruism via a green beard mechanism (with an implicit threshold of 1, see text) over kin and similarity targeting. (d) Selection favoured a green beard mechanism with a threshold of 100 (the maximum number of donations allowed) over kin and similarity targeting. (e) Selection favoured identical beard colour targeting over kin and similarity targeting. Purple, kin; blue, random (rand); grey, neutral (neut); black, similarity (85%); light green, green beard (GB) (1); dark green, green beard (100); red, identical beard colour (IBC).