Data from: When hawks give rise to doves: the evolution and transition of enforcement strategies

The question of how altruism can evolve despite its local disadvantage to selfishness has produced a wealth of theoretical and empirical research capturing the attention of scientists across disciplines for decades. One feature that has remained consistent through this outpouring of knowledge has been that researchers have looked to the altruists themselves for mechanisms by which altruism can curtail selfishness. An alternative perspective may be that just as altruists want to limit selfishness in the population, so may the selfish individuals themselves. These alternative perspectives have been most evident in the fairly recent development of enforcement strategies. Punishment can effectively limit selfishness in the population, but it is not free. Thus when punishment evolves amongst altruists, the double costs of exploitation from cheaters and punishment make the evolution of punishment problematic. Here we show that punishment can more readily invade selfish populations when associated with selfishness, whereas altruistic punishers cannot. Thereafter, the establishment of altruism due to enforcement by selfish punishers provides the ideal invasion conditions for altruistic punishment, effectively creating a transition of punishment from selfishness to altruistic. Thus, from chaotic beginnings, a little hypocrisy may go a long way in the evolution and maintenance of altruism.

尽管利他主义（altruism）相较于自私行为（selfishness）在局部层面处于劣势，利他主义如何得以演化这一问题，数十年来催生了大量理论与实证研究，吸引了跨学科科学家的广泛关注。在这一丰硕的研究成果中，有一个始终不变的核心观点：研究者们始终将目光投向利他者本身，以期找到利他主义遏制自私行为的内在机制。而另一种全新的研究视角则提出：正如利他者会试图抑制群体中的自私行为，自私个体自身或许也存在类似的动机。这类差异化视角在近年兴起的制裁策略（enforcement strategies）研究中体现得尤为鲜明。惩罚（punishment）能够有效遏制群体中的自私行为，但实施惩罚并非无成本。因此，当惩罚行为在利他者群体中演化时，欺骗者（cheaters）剥削带来的成本与惩罚实施的成本双重叠加，使得惩罚的演化进程面临诸多困境。本文研究表明，当惩罚行为与自私特质绑定时，其更易于入侵自私者群体；而利他型惩罚者（altruistic punishers）则无法实现这一点。在此之后，由自私型惩罚者（selfish punishers）实施制裁所催生的利他主义，将为利他型惩罚创造绝佳的入侵条件，最终推动惩罚行为完成从自私向利他的转型。由此可见，尽管演化初期充满混沌，些许伪善便可在利他主义的演化与维持过程中发挥至关重要的作用。