Biosocial effects of oxytocin in vertebrates: From hormonal reproductive functions to parochial altruism

Oxytocin is an ancient neuropeptide with a wide range of functions. Over hundreds of millions years of evolution, the functional role of oxytocin and its homologues expanded from initially providing effective reproduction to consolidating partner relationships in monogamous species, family groups of cooperatively breeding species and diverse complex relationships within social groups characterized by parochial altruism traits. In different classes of vertebrates, the expansion of the scope of oxytocin actions could evolve independently, and today the most complete spectrum of functional effects of oxytocin is studied in mammals. The review gives a brief analysis of the functional role of oxytocin and its homologues in vertebrates based on modern research with an emphasis on its effects on social behavior.