关于在自然界中解释的合作和自我牺牲以及在人类中，继续辩论。本文表明了一种思考这个着名问题的新方法。我认为，对于一个进化的生物学家以及量化的社会科学家，两个球员在捕食者面前的三角形的三角形（在2-1个情况下拍摄）是理解这些现象的基本概念构建。我展示了如何在捕食者的存在下，合作均衡合理地出现完全自私的代理商。If we examine the dynamics of such a model, and bias the lead player (ball possessor with pass/shoot i.e. cooperate/defect dilemma) in the selfish direction by only an infinitesimal amount, then, remarkably, the trajectories of the new system move towards a cooperative equilibrium. I argue that "predators" are common in the biological jungle but also in everyday human settings. Intuitively, this paper builds on the simple idea – a familiar one to a biologist observing the natural world but perhaps less so to social scientists – that everybody has enemies. As a technical contribution, I solve these models analytically in the unbiased case and numerically by an O(h5) approximation with the Runge-Kutta method.