ABSTRACT
This chapter describes the emergence of the developmental phase of childhood, as defined by an extended period of nutritional and social dependence beyond weaning, within the evolutionary trajectory of humankind. Evolutionary medicine is a relatively new field at the junction where insights from evolutionary biology clarify medical observations. Evolutionary biologists lay special emphasis on the idea that natural selection acts on phenotypes, not on genes, and that people represent a series of phenotypes. The chapter explains the Life history theory is a theory within physical anthropology which studies and seeks to explain the energy balance of an organism over its life course. The new stage of childhood emerged as a strategic life history response in early Homo habilis society under the imperative to nurture the immature baby within a family structure of cooperative parenting. In this context of evolutionary anthropology, the onset of childhood is defined as the time of weaning from breast-feeding, hence infancy becomes shortened.
