This chapter of the handbook proposes a developmental ethics, an organic moral theory grounded in (1) humanity’s deep evolutionary history, (2) the malleability of the child’s neurobiological structures that undergird moral functioning, and (3) the influence of cultural practices on neurobiological development. The chapter addresses the following questions: What kind of creature are we? What qualities do we need to live a full life? What kinds of capacities make each a proper member of the species? What influences our development? Answers center around perhaps the most critical influence on human development, our species’ evolved nest. In humanity’s ancestral context, nestedness is a lifelong experience with particular import in early life. Moral virtue emerges from holistically coordinated physiological, psychological, spiritual systems oriented toward holistic communal harmony, social attunement, receptivity, and interpersonal flexibility. Understanding how the evolved nest scaffolds biopsychosocial and moral development reveals why antisocial behavior is so pervasive in modern Western culture – and it provides a baseline for redesigning society to promote prosociality.