Birth and the Newborn Infant

The high degree of dependency at birth and an inordinately slow rate of growth of human infants and children place demands on mothers and other caretakers that appear to far exceed those of other mammals, including our closest primate relatives. What role do gestation and birth play in producing these highly dependent and slow growing infants that require investment from a variety of caretakers and numerous life history trade-offs? This presentation will focus on energetic and biomechanical factors that converge at the time of birth to set the stage for an enormously expanded role of childrearing in human evolution. For example, human maternal metabolism approaches its limit after about nine months of gestating a rapidly growing fetus with an exceedingly hungry brain. This limit is among the constraints placed on infant developmental stage, requiring birth at a relatively immature point along the fetal-infant growth continuum. Additionally, a somewhat narrow and rigid pelvis offers further resistance to birthing an infant with more advanced brain and cranial development. These challenges, requiring birth of an immature and highly dependent infant, are met through the extensive and costly caretaking that characterizes our species.