The primary goal of the present volume is to incorporate the extensive literature on behavioral flexibility in evolutionary biology and behavioral ecology into the canon of primatology in order to advance the Hamiltonian unification program within the Primate Order. My own conceptual frame- work, however, emphasizes the importance not only of optimization of genetic benefits but also of benefits to the phenotype,reflectingWest-Eberhard’s (2003) notion of the phenotype as a “bridge” between genotype and environment.