The evolution of learned and innate behavior: Contributions from genetics and neurobiology to a theory of behavioral evolution

In recent years, ethologists and psychologists have become increasingly interested in the evolution of the ability to learn and in the relationship between innate and learned behavior. However, recent discussions of behavioral evolution have not adequately incorporated contemporary knowledge of nervous system development and structure. Most discussions are based on the following assumptions: (1) That innate behaviors are programmed by specific genes; (2) that learning requires a larger, more flexible nervous system than does innate behavior; and (3) that the ability to learn is phylogenetically more recent than innate behavior. This paper reviews information about nervous system development and the neurobiology of plasticity and learning that questions the validity of these assumptions. It is hypothesized that behavioral flexibility is phylogenetically primitive and that learned behavioral adaptations may commonly precede innate forms of the same behaviors. The role of genetic assimilation in behavioral evolution is discussed.