Examining Developmental Plasticity in the Skeletal System through a Sensitive Developmental Windows Framework

Abstract

The primary goal of this dissertation is to develop a methodological framework for identifying and interpreting evidence of developmental plasticity in the skeletal system. The Developmental Origins of Health and Disease (DOHaD) hypothesis posits that phenotypic-environmental interactions in early life modify morbidity and mortality risks throughout the lifespan. Biological systems exhibit varying degrees of plasticity throughout development and are responsive to environmental signals that provide essential information about present and future environmental challenges. Not all environmental signals are equally likely to impact development, and the timing, intensity, and duration of these signals may have significant implications for downstream phenotypic effects. Building on existing DOHaD approaches within skeletal biology, this dissertation uses the concept of sensitive developmental windows (SDWs) to link developmental stress embodied in the skeletal system with adult phenotypic outcomes related to growth and survivorship. By integrating theoretical concepts from developmental biology with methodological approaches from bioarchaeology, this dissertation represents a novel approach to exploring the relationship between stress and phenotypic variation in skeletal biology. It extends existing bioarchaeological approaches informed by DOHaD by 1) examining evidence of stress in skeletal elements that are sensitized to environmental feedback at different stages in the developmental lifecycle, and 2) correlating artifacts of developmental stress with downstream phenotypic outcomes and indicators of fitness. To test this approach, relationships between developmental stress, estimated stature and mortality risk were examined in the Turkey Creek Pueblo skeletal collection. The results of this dissertation suggest that in environments characterized by chronic stress, proximate signals of nutritional stress may have a stronger influence on growth potential than signals of early life stress. However, early life stress may influence trade-offs involving early life resilience and heightened mortality risk in adulthood. By framing stress as a potentially informative signal capable of contributing to adaptive phenotypic variation, methodological approaches informed by the SDW concept facilitate more nuanced analyses of stress-associated skeletal biomarkers and their relationship with indicators of “health” and wellbeing.