Discontinuity in Evolution: How Different Levels of Organization Imply Pre-Adaptation

Abstract

this paper allowing the genotype to determine the development of the nervous system during all individual lifetime and making the developmental process sensitive to the external environment. We believe that this is a very promising direction that simulative models should pursue. A direction that for example may shed some light on fundamental questions like: how and in which conditions phenotypic plasticity has evolved? Biological systems can be described at various hierarchical levels. For example, an organism can be described at the genetic level, at the neural level, at the behavioral level, and at the fitness level. Each level determines the structure of the organism at the successive level but not all changes that occur at a certain level cause corresponding changes at higher levels. Since only part of the structure at each level (the functional part) is responsible for determining the structure at successive levels, only changes that affect these functional parts can cause changes at successive levels. If we examine the lineage of the best individual of the last generation in an evolutionary simulation with growing neural networks and we compare the two Os in each parent/offspring pair we see that different levels change at different rate. While at the genetic level almost all offspring differ from their parents, the probability that the two members of a pair differ at higher levels gradually decreases as one ascends levels. This implies that most of the mutations do not affect the fitness level and as a consequence should be considered nonadaptive or neutral. However, these mutations may produce changes at other levels and this can have long term consequences for the evolutionary process