@Anonymous Coward:Reasonable, except even by defecting you haven't gained the substantially greater payoff that is the whole point of Prisoner's Dilemma. In other words, like he asks: what about the Babyeater children? I wouldn't know just how to quantify the 2 options-I believe that's the whole point of this series :) -but I wouldn't call it much better than what the Superhappy aliens offered, at least with the more "inclusive" altruistic concern that the humans in this illustration are supposed to have.