Effects of Several Bioinspired Methods on the Stability of Coevolutionary Complexification

We study conditions for sustained growth of complexity in an abstract model of parasitic coevolution. Previous research has found that complexification is hard to achieve if the evolution of the symbiont population is constrained by the hosts but the evolution of the hosts is unconstrained, or, more generally, if the task difficulty is much higher for the symbionts than for the hosts. Here we study whether three bio inspired methods known from previous research on achieving stability in coevolution (balancing, niching, and reduced resistance) can restore complexification in such situations. We find that reduced resistance, and to a lesser degree niching, are successful if applied together with truncation selection, but not if applied together with fitness proportional selection.