Kin-Selection: The Rise and Fall of Kin-Cheaters

We demonstrate the existence of altruism via kin selection in artificial life and explore its nuances. We do so in the Avida system through a setup that is based on the behavior of colicinogenic bacteria: Organisms can kill unrelated organisms in a given radius but must kill themselves to do so. Initially, we confirm results found in the bacterial world: Digital organisms do sacrifice themselves for their kin—an extreme example of altruism—and do so more often in structured environments, where kin are always nearby, than in well-mixed environments, where the location of kin is stochastically determined. Having shown that helping one's kin is advantageous, we turn our attention to investigating the efficacy and implications of the strategies of kincheaters, those who receive help from kin but do not return it. Contrary to the expectations of current theory, we find that kin-cheaters outcompete kin-altruists. Our results cause us to question the stability of strategies that involve altruism between kin. Knowing that kin-altruism persists in biological systems, however, we search for, and find, conditions that allow kin-based altruism to persist in evolving systems despite the presence of kin-cheaters.