Evolutionary developmental psychology examines development through the lens of evolutionary theory. We first discuss adaptations of infancy and childhood, including ontogenetic, deferred, and conditional adaptations. The important ontogenetic adaptations reviewed include neonatal imitation and cognitive immaturity during childhood. Sex differences in play style as deferred adaptations are also discussed. Conditional adaptations, with children adjusting their developmental trajectory as a function of early life conditions, are examined from the perspective of life history theory. We then provide a framework for how adaptations develop, discussing evolved probabilistic cognitive mechanisms, evolved information-processing mechanisms that are expressed in a probabilistic fashion in each individual in a generation based on the continuous and bidirectional interaction over time at all levels of organization, from the genetic through the cultural. We provide examples of evolved probabilistic cognitive mechanisms from the domains of infant face perception, social learning, prepared fears, and tool use. Adaptations are central to an evolutionary psychological explication, and understanding how such adaptations develop enhances our understanding of adaptations.