This chapter illustrates developmental similarities between species and suggests a canalization of cognitive maturational sequence, but not of maturational timing, that extends across species domains. Scheibel and Neville each focus on the maturation of the anatomical and physiological bases of language in relationship to hemispheric differences of language function. To the extent that neural maturation, the spontaneous activities of children and the child care activities of adults are genetically canalized processes within the human species, cross-cultural regularities of development are to be expected. To the extent that brain and behavioral maturation are plastic and genes and rearing conditions vary, behavioral maturation will also be expected to vary. The science of behavioral genetics has helped people to unravel the nature of behaviour-genetic interactions in the genesis of individual differences in animals. The biosocial approach examines interactions between behavior, evolution, and biological maturation from the multidisciplinary perspectives provided by cultural and biological anthropologists, zoologists, psychologists, sociologists and neuroscientists.