Although evolutionary perspectives have grown in prominence in the strategy and organizations literatures, the nature and operation of the selection processes at work have received very little attention. The chapter proposes a simple model of organizational evolution designed to examine how selection processes influence the evolution of organizational productivity and fitness. A series of experiments examine how the nature of the selection process and the level of selection pressure influence the population-wide level of fitness and productivity over time. The results show that the distinction between subset selection from successor selection has important consequences. Furthermore, the results reveal that it is crucial to consider how selection operates on actual phenotypic properties while identifying the underlying genotypic properties that are transmitted in processes of organizational replication. Researchers should carefully consider how these processes and properties are expressed in populations of social organizations.