Abstract
A polyvagal perspective clarifies the neurobiological and biobehavioral shifts that occurred during evolutionary transition from asocial reptiles to social mammals. This transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions. This innovation enabled social behavior to function as a neuromodulator that could efficiently regulate and optimize autonomic function to support homeostatic processes. This journey is highlighted by the phylogenetic transition during which the autonomic nervous system was repurposed to suppress defensive strategies to support and express sociality. The product of this transition was an autonomic nervous system with capacities to self-calm, to spontaneous socially engage others, and to mitigate threat reactions in ourselves and others through social cues. Thus, social behavior became embedded with specific neurobiological processes that had capabilities to support homeostatic functions leading to optimized health, growth, and restoration. Polyvagal Theory emphasizes sociality as the core process in mitigating threat reactions and supporting mental and physical health.