The target article offers a game-theoretical analysis of primitive intergroup aggression (i.e., raiding) and discusses difficulties in achieving peace. We argue the analysis does not capture the actual strategy space, missing out “do-nothing.” Experimental evidence robustly shows people prefer doing nothing against out-group members over cooperating with/attacking them. Thus, the target article overestimates the likelihood of intergroup aggression.

We focus on the implications of De Dreu and Gross's findings for the evolutionary perspective on out-group aggression and in-group cooperation. Although their experimental protocols are potentially useful in determining the origins of out-group aggression in humans, they so far provide inconclusive evidence only. We suggest ways of furthering our understanding of the connection between parochial cooperation and intergroup conflict.