This article introduces a new model of the relationship between growth and learning and tests a set of hypotheses related to the development of adult competency using time allocation, anthropometric, and experimental task performance data collected between 1992 and 1997 in a multiethnic community in the Okavango Delta, Botswana. Building on seminal work in life history theory by Hawkes, Blurton Jones and associates, and Kaplan and associates, the punctuated development model presented here incorporates the effects of both growth and learning (...) constraints on age-specific task performance. In addition, the payoff to investment in two forms of embodied capital, growth-based and learning-based, are examined in relation to features of the socioecology, including subsistence economy and family composition.The three main findings are:The development of adult competency in specific tasks entails a steplike relationship between growth- and experience-based forms of embodied capital in the ontogeny of ability acquisition.There is a trade-off between the acquisition of experience-based embodied capital in the form of skills and knowledge and immediate productivity among children. Time allocation to these alternatives is primarily determined by the short- and long-term costs and benefits to parents of investment in children’s embodied capital.The availability of laborers and the overall labor requirements of the household are major determinants of investment in alternate forms of embodied capital and resulting variation in children’s time allocation. The value of children’s labor to their parents is dependent upon the opportunity costs to engaging in other activities not only for the child in question but also for potential substitute laborers.These results have important implications for our understanding of the role of growth and learning in the evolution of the human juvenile period, as well as for our understanding of cross-cultural variation in child growth and development and patterns of work and play. (shrink)

Recent theoretical models suggest that the difference between human and nonhuman primate life-history patterns may be due to a reliance on complex foraging strategies requiring extensive learning. These models predict that children should reach adult levels of efficiency faster when foraging is cognitively simple. We test this prediction with data on Meriam fishing, spearfishing, and shellfishing efficiency. For fishing and spearfishing, which are cognitively difficult, we can find no significant amount of variability in return rates because of experiential factors correlated (...) with age. However, for shellfish collecting, which is relatively easy to learn, there are strong age-related effects on efficiency. Children reach adult efficiency more quickly in fishing as compared to shellfish collecting, probably owing to the size and strength constraints of the latter. (shrink)

Meriam children are active reef-flat collectors. We demonstrate that while foraging on the reef, children are significantly less selective than adults. This difference and the precise nature of children’s selectivity while reef-flat collecting are consistent with a hypothesis that both children and adults attempt to maximize their rate of return while foraging, but in so doing they face different constraints relative to differences in walking speeds while searching. Implications of these results for general arguments about factors that shape differences between (...) child and adult behavior and human life-histories are explored. (shrink)