The influence of skeletal size on age-related criteria from the pelvic joints in Portuguese and North American samples

Estimating age of death for adult skeletons with accuracy is still one of the chief predicaments in bioanthropology. It has been recognized that methods’ inaccurate results from the lack of a better understanding of the ageing process and associated confounding factors. In the present study was investigated if body size (measured by stature, body mass, robusticity and articulation size) affects age-related morphological criteria of the pubic symphysis, auricular surface of the iliac and acetabulum. Adult individuals of both sexes with age at death superior to 17 years old were analysed from the Identified Skeletal Collection from the University of Coimbra (Portugal), and the William Bass Donated Skeletal Collection (USA). Three levels of analysis were followed to evaluate joints degeneration: individual traits, components (weighted linear clustering of correlated traits) and a composite score (sum of all the scores across all characters). Furthermore, stature, body mass and robusticity were computed through femoral measurements, and the surface area of the pelvic joints were calculated from three-dimensional digital polygon objects created with a white light scanner. A logistic regression analysis was carried out, showing especially body mass, stature and joint surface area affect some of the morphological criteria at the pelvic joints. Robusticity has a minimum effect on the pelvic joints metamorphosis. Results suggest that smaller individuals tend to age slower, with the transition from a “younger” to an “older” stage occurring at an older age compared with bigger individuals. Different patterns were obtained between population samples, possibly due to body size and age distributions differences between collections, or due to the complex and variable effect body size has in bone degeneration. The present research shows that body size influences the pelvic joints age-related criteria, which is important to incorporate in future age at death estimation methods.