Lactation constitutes a major focus for research in international health because of its dramatic impact on child survival; evolutionary biology has investigated lactation as an important aspect of parenting strategy, with implications for understanding parent-offspring conflict. These perspectives are brought together in an attempt to develop integrated models for an issue of key international health concern: the duration of exclusive breast-feeding and the timing of weaning. This analysis highlights the relevance of evolutionary theory for practical problems in public health, and (...) it suggests the utility of public health outcomes for addressing evolutionary questions. (shrink)

Previous research addressing the association between leisure and happiness has given rise to the hypothesis that informal social activities might contribute more to happiness than solitary activities. In the current study, we tested how the two types of leisure—social and solitary—contribute to a person’s subjective sense of well-being. For the empirical estimate, we used four consecutive quarters of data collected from 533 people over the age of 16, from 13 Tsimane’ hunter-farmer villages in the Bolivian Amazon. Results suggest that only (...) social, not solitary, leisure has a positive and statistically significant association with subjective well-being. The association between solitary leisure and subjective well-being was negligible or negative. Future research should focus on emic definitions of social and solitary time, for solitary time might not always be equivalent to leisure and productive group activities might substitute for social leisure. (shrink)