Body Size Interactions with Pubic Symphysis Age-at-Death Estimation: A Critical Analysis of Senescence of the Pubic Symphysis Components

Biological anthropologists struggle with accuracy and precision during age-at-death estimation when attempting to correlate biological age with chronological age, especially in older adults. Research has shown that intrinsic and extrinsic factors can cause this discrepancy. Anthropologists have recently found that body size may affect age-at-death estimation, with larger individuals being more commonly overaged and smaller individuals being underaged (Merritt, 2019; Wescott and Drew, 2015). This study elaborates on previous work in three ways. First, by applying Hartnett’s (2010) pubic symphysis phase method as the age-at-death estimation method used, which has not been assessed for body size interactions and is likely more robust in application compared to past methods. Secondly, utilizing a component method as specific components involved in age-at-death estimation involving the pubic symphysis are likely tied to variations in body size more closely than others. Lastly, differentiating by sex as males likely have a stronger relationship with body size than females during skeletal age estimation.

Adults from the Bass Donated Skeletal Collection (N=371) were assessed for age-at-death estimation accuracy using Hartnett’s method. Using Kruskal-Wallis tests and logistic regression, the results showed that when applying Hartnett’s pubic symphysis method, there is no observed difference in age-at-death estimation due to body size variables like body mass and BMI; however, there was a difference dependent on sex. Males were underaged more frequently when categorized as having an underweight BMI and more likely to be overaged when they had a larger body mass than slighter individuals. Body size may not interact with Hartnett’s method due to other contributing factors of aging that overshadow body size when applying this method. Of the pubic symphysis components assessed within this study, billowing and bone quality were related to body size differences, especially in males. Larger individuals displayed advanced billowing morphological qualities more often, while bone quality exhibited more advanced scores in smaller individuals. The results of this study demonstrate the improvements to the past pubic symphysis methods made by Harnett created better applicability of the method to any body size, requiring a reassessment of which methods are used in anthropology.