Caregiving relationships as evolutionary and developmental bases of obligation.

Obligation as defined by Tomasello requires mutually capable parties, but one-sided caregiver relationships reveal its developmental and evolutionary precursors. Specifically, "coercive" emotions may prompt protective action by caregivers toward infant primates, and infants show distress toward caregivers when they appear to violate expectations in their relationships. We argue that these early social-relational expectations and emotions may form the base of obligation.