In 1997, I argued that with the loss of Piaget's theory as an overarching guide, cognitive development had become disjointed and a new metatheory was needed to unify the field. I suggested developmental biology, particularly evolutionary theory, as a candidate. Here, I examine the increasing emphasis of biology in cognitive development research…

Play has been difficult to define because it is an aspect of many activities rather than of just a specific kind of activity. Classic theorists such as Piaget and Vygotsky emphasized representational play as play in its purist form, but both immediate and ultimate functions of play can be discerned in simple physical activity play. (Author)

Proposes that humans may have evolved a special sensitivity to certain types of social information during rough-and-tumble play that facilitates social cognition. Describes the cognitive benefits of physical play as providing a break from demanding intellectual tasks and hypothesizes that physical play is related to gender differences in spatial…

Considers areas of consensus from commentaries, including the value of an evolutionary perspective and the utility of exploring variations in physical activity play. Examines areas of debate, including the nonplay-play distinction, functions of rough-and-tumble play, and the opportunities of juveniles for exercise training. Calls for more directed…

Responds to Maccoby's and Hinde's commentaries on the Belsky, et al. article in this issue. Highlights several points of concurrence and disagreement. Draws attention to the potential benefits of asking questions about proximal and ultimate causation simultaneously and, thus, the need for child developmentalists to think about both the how and why…

Maintains that the "getting into shape" hypothesis of explaining the inverted-U distribution of exercise play across age is likely incorrect. Argues that the biological study of human physical activity play, as recommended by Pellegrini and Smith (1998), will reveal whether physical activity play represents an example of…

Argues that an evolutionary account provides insight into developmental function and individual differences. Outlines some assumptions of evolutionary psychology related to development. Introduces the developmental systems approach, differential influence of natural selection at different points in ontogeny, and development of evolved…

Comments on Belsky, Steinberg, and Draper's article in this issue. Offers three likely reasons for adaptation of human behavior. Argues that Belsky, et al. use only two of these reasons in their proposed evolutionary theory of socialization. Suggests that an evolutionary approach is useful if it integrates diverse facts, aids clinical practice,…

Argues that an evolutionary perspective can unite the study of species-typical development and individual variation. Provides examples from the domains of personality, social, and intellectual development. Maintains that understanding the ways in which genes and environments work together helps developmentalists identify children who need…