Selecting for evolvable representations

Evolutionary algorithms tend to produce solutions that are not evolvable: Although current fitness may be high, further search is impeded as the effects of mutation and crossover become increasingly detrimental. In nature, in addition to having high fitness, organisms have evolvable genomes: phenotypic variation resulting from random mutation is structured and robust. Evolvability is important because it allows the population to produce meaningful variation, leading to efficient search. However, because evolvability does not improve immediate fitness, it must be selected for indirectly. One way to establish such a selection pressure is to change the fitness function systematically. Under such conditions, evolvability emerges only if the representation allows manipulating how genotypic variation maps onto phenotypic variation and if such manipulations lead to detectable changes in fitness. This research forms a framework for understanding how fitness function and representation interact to produce evolvability. Ultimately evolvable encodings may lead to evolutionary algorithms that exhibit the structured complexity and robustness found in nature.