The Flexible Balance of Evolutionary Novelty and Memory in the Face of Environmental Catastrophes

We study the effects of environmental catastrophes on the evolution of a population of sensory-motor agents with individually evolving mutation rates, and compare these effects in a variety of control systems. The evolution of mutation rates must balance (i) the need for evolutionary “novelty,” which pushes mutation rates up, and (ii) the need for evolutionary “memory,” which pushes mutation rates down. We observe that an environmental catastrophe initially shifts the balance toward evolutionary novelty and causes mutation rates to evolve upwards. Then, as the population adapts to the new environment, the balance shifts back toward evolutionary memory and the mutation rate falls. These observations support the hypothesis that second-order evolution of the mutation maintains a flexibly shifting balance between evolutionary novelty and memory.