Add to ORKGWhy are people inclined to build friendships and maintain durable, nonreproductive relationships? Previous computational modeling work on the evolution of commitment in repeated exchange showed that being largely unconditionally cooperative in committed relationships is more viable than conditional cooperation based on fair reciprocity (e.g. Tit for Tat). But this work did not conduct a sufficiently strict test of the viability of commitment because it did not allow for the spontaneous emergence of "smart cheaters" who take advantage of the tolerance of commitment players. We extend previous studies with the possibility of randomly mutating strategies under evolutionary pressures, and give a much larger coverage of an infinite strategy spac...