Evolutionary developmental psychology is a discipline that has the potential to integrate conceptual approaches to the study of behavioral development derived from psychology and biology as well as empirical data from humans and animals. Comparative research with animals, and especially with nonhuman primates, can provide evidence of adaptation in human psychological and behavioral traits by highlighting possible analogies (i.e., similar function, but independent evolution) or homologies (i.e., inheritance from a common ancestor) between human traits and similar traits present in animals. Data from nonhuman primates have played a crucial role in our understanding of infant attachment to the caregiver as a developmental adaptation for survival. Primate and human data are also consistent in suggesting that female interest in infants during the juvenile years may be a developmental adaptation for reproduction that facilitates the acquisition of maternal skills prior to the onset of reproduction.