Oxytocin Pathways and Human Evolution

This presentation examines the hypothesis that Homo sapiens, with their high level of dependence on social behavior and cognition, could not have evolved without the neuropeptide, oxytocin. Oxytocin pathways - which include oxytocin, the related peptide vasopressin, and their receptors - are at the center of physiological and genetic systems that permitted the evolution of the human nervous system and allowed the expression of contemporary human sociality. Unique actions of oxytocin pathways, including the facilitation of birth, lactation, maternal behavior, extended periods of nurture, genetic regulation of the growth of the neocortex, and the maintenance of the blood supply to the cortex, were necessary for primate encephalization. In general, oxytocin permits the high levels of emotional sensitivity and attunement necessary for rearing a human child. Under optimal conditions oxytocin may create a physiological metaphor for safety, experienced as sensations and emotions, which are fundamental to human social behaviors. Together these form a substrate for the emergence of human intellectual development and eventually complex societies and cultures.