Temporal change in nonmetric traits of indigenous peoples of the American southwest
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Abstract
This study seeks to distinguish the presence of secular change in contemporary nonmetric trait expression and explores the efficacy of morphological ancestry estimation with regards to North American indigenous groups. The study was conducted using cranial and mandibular trait data collected from two indigenous samples originating from the American Southwest: a pre-Contact sample from the American Museum of Natural History (n=150) and a modern sample from the New Mexico Decedent Image Database (n=100). To observe the modern sample, the RadiAnt DICOM viewer program was used to transform CT scan stacks into 3D models.
Pearson’s chi-square analyses were used to assess the presence of statistically significant difference between nonmetric trait expression between the two samples. The analyses produced significant p-values (≤0.05) in 22 of the 24 observed traits. Using binary logistic regression equations, four models were developed to assess which traits contributed significantly to predicting group membership: Model 1 combined cranial and mandibular traits, Model 2 used seven of Hefner’s (2009) 11 macromorphoscopic traits, Model 3 used only cranial traits, and Model 4 used only mandibular traits.
To evaluate the efficacy of an extant ancestry estimation method on indigenous sample, data from both the pre-Contact and modern samples were entered into the hefneR decision support system. The results indicate that the hefneR algorithm does not produce reliable ancestry estimates for either pre-Contact or modern indigenous samples; the samples received 14% and 11% correct classification, respectively. This study demonstrates that secular change has affected nonmetric trait expression in indigenous groups and that pre-Contact samples should not be used as proxies for modern populations.