Among the biological and behavioral foundations of humanness is the fact that we give birth to extremely undeveloped and dependent infants that require large investments in time and energy for 12–15 years. The consequences of this for an understanding of human evolution have often been alluded to but never fully explored.  This symposium examines the constraints on gestation, birth and infancy including both the costs and benefits with regard to obstetrics, energetics, cognition, thermoregulation and locomotion.  Presentation topics include:  What is undeveloped about human infants and how does their developmental state compare with other primates?  What is the state of neurological development of human infants in their first year of life?   What factors account for the relative immaturity of human infants at birth?  Contributors explore: anatomical effects on obstetrics, metabolic restraints on how long a woman can gestate a large-brained and large-bodied fetus, placental and immune factor challenges, and a premium on learning outside the womb while the brain is growing rapidly. 

Additional questions derive from exploring the idea that key human characteristics distinguishing us from other primates (such as our reliance on culture and alloparenting) owe a significant debt to the helpless infant.  What role did the need to carry helpless infants contribute to the evolution and refinement of bipedalism?   Did language emerge to facilitate contact between mothers and helpless infants?   Did the need to care for vulnerable infants lead to paternal, grand-maternal and cooperative parenting?   This costly developmental pattern is unprecedented among primates and relates to other distinctive aspects of our biology and behavior.  We examine both the costs and benefits of giving birth to such immature offspring and propose that infant helplessness and human social and cultural adaptations evolved hand-in-hand.