   Advocates of optimality models often argue that building and testing such models provides the best way to identify and discover evolutionary constraints, and that these constraints can then be used to build better optimality models (Amundson 1994, Seger and Stubblefield 1996). Many biologists that analyze the evolution of development or “evo-devo” use a different set of molecular and morphological investigative techniques to uncover robust and important developmental constraints (see, e.g., Müller and Newman 2003, Kirschner and Gerhart 2005). They object that the concept of optimality is a poor tool for answering their research questions. The recognition of two kinds of constraints resolves this dispute. We see then that optimality modeling usually entails the incorporation of or the discovery of constraints on adaptation, whereas studies of evolution and development investigates constraints on form. A full understanding of evolutionary history requires a synthesis of these approaches.