In order to examine secular change in morphological skull and pelvic traits frequently used for sex estimation, score data of the five Walker (2008) traits (nuchal crest-NC, mastoid process-MP, glabella-G, supra-orbital margin-SO, mental eminence-ME) and the three Klales et al. (2012) traits (ventral arc-VA, subpubic contour-SPC, medial aspect of the ischio-pubic ramus-MA) were collected from 1,734 individuals of known sex and ancestry from multiple skeletal collections.
Temporal variation was assessed by comparing trait score frequencies between contemporary and historic samples using the Mann-Whitney U test. Significant differences between the modern and historic samples were found for the G (p=0.012) and left SPC (p=0.039) in black females and for G (p=0.008), left MP (p=0.012), and the SPC (p=0.037 left; p=0.002 right) in black males. In all cases, the contemporary black sample had significantly lower (i.e., more gracile) scores. In Whites, significant differences between temporal periods were found for the MP (p=0.000 left and right), G (p=0.000), and NC (p=0.03) in females and the NC (p=0.000) in males. All three traits of the pelvis were significantly different at the p>0.05 level for both white males and females. All traits exhibited significantly lower scores (i.e., more gracile) in the modern sample except for the NC which has more robust/higher scores in the modern white samples. Overall, there are patterned changes occurring in these skull and pelvic traits over time which can impact the utility of these traits for accurate sex estimation in bioarchaeological and forensic contexts. (publisher abstract modified)