The Evolution of Society
We re-examine the evolutionary stability of the tit-for-tat (tft) strategy in the context of the iterated prisoner's dilemma, as introduced by Axelrod and Hamilton. This environment involves a mixture of populations of "organisms" which interact with each other according to the rules of the prisoner's dilemma, from game theory. The tft strategy is nice, retaliatory and forgiving, and these properties contributed to the success of the strategy in the earlier experiments. However, it turns out that the property of being nice represents a weakness, when competing with an insular strategy, but the reverse is also true, which means that tft is not an evolutionarily stable strategy. In fact, insular strategies prove to be better at resisting incursion. Finally, we consider the implications of this result, in terms of naturally occurring societies.