Criterion for Altruists selection. ( a) fixation probabilities π
(red squares) and π
(blue circles) as a function of selection pressure , for N
= 100 and . Values are obtained by numerically solving eq.(8). Solid lines are theoretical values (eqs. 13,14). Increasing N
are indicated by the arrow. (b) equilibrium selection pressure for which π
for multiple combinations of and , as a function of relative population increase, obtained numerically. The solid line is the theoretical value (eq.15).