The Human First Metatarsal in Bioarchaeological Research: New Insights into Human Variation and Bone Health Research from Kellis 2, Dakhleh Oasis, Egypt (50-450CE)

Objectives: This research tests the efficacy of using the human first metatarsal (MT1) in bioarchaeological research, specifically to investigate human variation (nonmetric traits and sexual dimorphism) and skeletal health (Osteo-Volumetric Density and µCT analysis) in antiquity. To date, this bone has had limited applications in bioarchaeology. Materials and Methods: This study used human remains from the Kellis 2 (K2) cemetery, located in the Dakhleh Oasis, Egypt (50-450CE). Specifically, 377 MT1s, representing 212 individuals were used to investigate human variation and osteo-volumetric density (OVD) in the K2 skeletal population. Additionally, skeletal health was further assessed in a female sub-sample (n=44) of the population using µCT analysis. µCT imaging of the MT1s was conducted using eXplore speCZT scanner, and analyses were done in MicroView with the Advanced Bone Analysis Application software add-in (Version 2.1.2, GE Healthcare Biosciences, London, ON) Results: The intermetatarsal facet had a prevalence of 28% in the K2 skeletal population. Moreover, significant sexual dimorphism was observed for MT1 metrics, and logistic regression models could predict the sex of an individual from K2 between ~80-90% of the time. The novel OVD method was found reliable/reproducible through intra-/inter-observer statistical analyses. The OVD patterns differed significantly between males and females, as well as between age-cohorts. The inverse relationship between age and the estimated OVD in K2 females was much more pronounced than was seen in K2 males. Additionally, an inverse relationship between biological age and the standard measures associated with bone strength/architecture using µCT analyses was observed for the female sub-population. The T-scores of individuals previously diagnosed with osteoporosis (based on age and fractures) were significantly below the mean of the “healthy” population using both OVD and µCT analyses of the MT1. Conclusions: The first metatarsal is a suitable element for the study of human variation and skeletal health in antiquity. Although not an area normally associated with osteoporosis related fractures, this research shows that the MT1 is not spared from age-related bone loss, and may prove useful for investigating skeletal health when the more traditional elements are not available