Environmental factors exert considerable influence over processes of growth and development, and stress experienced in early life can have long-term consequences for health and mortality risk. It is therefore critical to understand when individuals are most vulnerable to stress exposures. Sensitive developmental windows (SDW) are periods in early life when energy needs are high, and developing tissues exhibit greater plasticity in response to stress. This doctoral dissertation project will examine evidence of plasticity in the human skeletal system using a SDW framework, in order to better understand how the timing of stress exposures in early life influence patterns of disease susceptibility and mortality risk over the lifespan. The intellectual impacts of this project will be the production of a novel framework in which to more clearly define the relationship between early life environments, biology, and health outcomes across the lifespan. Insights derived from this project about the lifetime impacts of developmental stress may inform research in human development and public health. The project will also facilitate training of undergraduate and graduate students in non-destructive methods of skeletal analysis that are broadly applicable across modern, historical, and archaeological contexts. This project will improve existing methods of identifying and interpreting evidence of plasticity in the skeletal system by examining a set of asymmetries in skeletal elements that capture an extended period of early child development. Evidence for plasticity will be measured through the SDW framework by calculating asymmetry indices in three skeletal samples that represent human populations engaged in different modes of subsistence, social organization, and diet (early farmers, prehistoric agriculturalists, and historic preindustrialists). These asymmetry indices will be compared across populations and assessed using childhood mortality rates, age-at-death and adult stature as covariates, so that the impact of plasticity on mortality risk over the lifespan can be evaluated. The methodology employed in this project involves non-destructive analysis of skeletal elements, providing an accessible approach to examining plasticity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.