Evolution of Developmental Plasticity of Soft Virtual Creatures in Changing Environments

The objective of this study is to elucidate the role of developmental plasticity in the adaptive evolution of organisms in response to environmental change. To achieve this, we evolved flexible two-dimensional voxel-type virtual creatures using Evolution Gym. We introduced a new voxel type, named developmental plasticity voxel, capable of expressing different phenotypes (i.e., voxel types) depending on environmental conditions, and evolved genes for morphology, behavior, and developmental plasticity. In an evolutionary scenario in which the fitness measure shifted from the distance moved to the right in the first half of generations to the distance moved to the left in the second half, we observed that developmental plasticity genes that evolved neutrally in the first half of the experiment exhibited diverse morphology and behavioral patterns when the environment changed. We also found that in the case where the evolutionary process was accelerated, the adaptive morphology and behavior emerged by making use of the existing morphology and plasticity to adapt to a new environment, and were further improved by the subsequent evolution process. This phenomenon is consistent with the concept of the plasticity-first hypothesis and exaptation.