The generative entrenchment of an entity is a measure of how much of the generated system depends upon the presence or activity of that entity. It has been demonstrated that entities with higher degrees of generative entrenchment tend to be more conservative in evolutionary changes of such systems. Models of complex structures incorporating the effects of generative entrenchment have demonstrated their relevance in analyzing and explaining a variety of developmental and evolutionary phenomena. Dr. Wimsatt and Mr. Jeffrey Shank will extend prior simulations and analyses of a variety of cases and problems and investigations of a number of results on the evolution of gene control networks, extending not only their own work but that of S. A. Kauffman and others to investigate the influence of different degrees of generative entrenchment on the behavior of these networks and their evolution. Since virtually any system exhibits differential degrees of generative entrenchment among its parts and activities, these studies and results have in addition broad potential application for theoretical, simulation, and experimental analyses of developmental programs and their significance for evolution, macroevolutionary change, the innate-acquired distinction and investigations using it in linguistics and cognitive psychology, developmental constraints, and constraints on the evolution of complex adaptations and scientific change.