A Critical Analysis of the Use of Non-Metric Traits for Ancestry Estimation among Two North American Population Samples

The use of diverse morphological features, or traits, of the skeleton for the estimation of ancestry remains an important part of the forensic anthropologist’s toolkit for medico legal death investigations. Research into the estimation of ancestry has an equally long history and use in anthropology. This study re-evaluates the classic techniques historically used to estimate ancestry within the United States in human crania with emphasis to the possible inclusion of secular change in the prevalence of traits when comparing well documented modern skeletal material population to a comparable sample of an earlier period.

The aim of this study was to critically analyze the use of twenty-seven previously established nonmetric cranial traits associated with ancestry estimation among North American population samples: American Blacks and Whites. This work evaluates the relative utility of each trait alone as well as assesses the potential influence of short term evolution, or secular change, on the distribution and expression of each trait. Crania (n=441) were used from three sources: The William M. Bass Donated Collection (n=190) and LSU (n=34) provided the modern sample and The Robert J. Terry Collection (n=217) for a historic sample. For each trait, frequencies were tabulated and chi square tests (p > 0.05) conducted to assess significant change between populations and for secular change between the two groups. This study demonstrates that it is possible to discern statistically significant differences between the two groups in some traits while not in others. Secular change was observed in both the mid-facial region of the crania as well as traits typically regarding as reflecting cranial robusticity.