Master of Arts
Stock, Jay T.
This study interrogates the relationship between early life environmental variability (measured through birth weight and age at menarche), and adult phenotypic outcomes in female athletes and non-athletes from the United Kingdom. Using anthropometric, and 3D body surface scan analysis, patterns of phenotypic variation were interpreted in a life history context. Significant correlations between birth weight, stature, and bi-iliac breadth were observed. Age at menarche had significant correlations with linear growth and body composition measures in both Pearson and Canonical Correlation analyses. Crural index was found to be negatively correlated with limb segment SA:Vol in opposition to the expectations of Allen’s rule, a result that requires further investigation. Overall, variation in age at menarche was related to adult phenotypic variation, specifically linear skeletal growth, which may allow the development of regression equations that estimate life history variables in bioarchaeological populations, which would aid in more accurate interpretations of the past.
Summary for Lay Audience
This study aims to investigate the relationships between variation in early life stress and nutrition and its impact on shaping variation in the adult phenotype (the amalgamation of observable physical characteristics, relating to the environmentally dependent expression of an individual’s genetic code). It has been shown that children who are underweight at birth and/or who experience stressful or nutrient-restricted childhoods often have adverse developmental outcomes. This is reflected in their life history strategy (the individual timing and manifestation of specific developmental processes and milestones unique to a species) such that they mature earlier (often resulting in reduced stature), with an underdeveloped beta cell mass, and are more likely to develop a centralized fat distribution. These factors contribute to the manifestation of metabolic and cardiovascular diseases in adulthood. The role of early life variation in the manifestation of the life history strategy itself, and subtle variation in physical characteristics is less well understood.
In the following study, the physical characteristics of modern human females are examined through the use of anthropometrics, 3D body surface scans, and bioimpedance and subsequently compared to the early life indicator variables birth weight and age at menarche to better understand how variation in an individual’s life history is reflected in their phenotype as it relates to reproduction, growth, and maintenance processes. Pearson correlation analyses were used to determine the directionality and degree of shared variance between phenotypic characteristics. Canonical correlation analyses were then used to determine the variable contributions of birth weight and age at menarche to variation in linear growth and body composition variable groups. Overall, age at menarche was shown to contribute more to phenotypic variation than birth weight.
This research is relevant both to understanding the effects of early life environmental variation in the manifestation of certain phenotypes in modern humans but also in better understanding the lived experiences of ancient humans. The clarification of the connection between different outcome characteristics in a modern population can aid in the interpretation of variation in skeletal populations, aiding researchers in developing more robust reconstructions of life in the past.
Atkinson, Laura Ann Hope, "The impact of energetic trade-offs on the developmental trajectory and life history strategy of Homo sapiens: The modern human female phenotype" (2022). Electronic Thesis and Dissertation Repository. 8450.