Investigation of Craniofacial Morphological Variation at Sully (39SL4)

Elizabeth Rose Agosto, The University of Montana

Abstract

This study utilizes a theoretical framework of modern quantitative population genetics to identify factors contributing to the morphological variability between multiple, geographically distinct burial areas associated with the Sully village site (39LS4) in the Middle Missouri region of South Dakota. In particular three burial areas at Sully (A, D, and E) provide adequate samples for assessing intra-site variation. It has been a long-held belief that the observed morphological variability between burials areas is due to temporal sequencing; however, this explanation lacks hard craniometric and archaeological support. This study reassesses the assumption of temporal sequencing through the investigation of post marital residence patterns. The practice of matrilocality and village endogamy has been reported for the Arikara in ethnohistoric accounts; this pattern was investigated using a geometric morphometric approach in conjunction with standard statistical analyses. Three dimensional coordinate data from 20 craniofacial landmarks from 69 Sully burials attributed to the Extended Coalescent and 305 burials from Extended Coalescent and Post-Contact Coalescent cemeteries from Anton Rygh (39CA4), Mobridge (39WW1), Larson (39WW2), Black Widow Ridge (39ST203), Leavitt (39ST215), Cheyenne River (39ST1), and Indian Creek (39ST15) are examined to assess the factors contributing towards the phenotypic variation at Sully. The coordinate data were translated, rotated, and scaled via generalized Procrustes analysis permitting the inclusion of both males and females in the samples and fitted coordinates were subjected to principal component analysis. The resulting principal components were used as variables in three tests of homogeneity: Zhovotovsky’s F-ratio, Wishart’s bootstrap, and a nonparametric bootstrap; these tests failed to detect the expected pattern of post marital residence, but found that the phenotypic variability at Sully is no greater than that of the temporally constricted village site Larson. Canonical variate analysis of the projected coordinates indicates that the inhabitants of the Sully site may have been patrilocal and participated in a complex system of mate exchange between Arikara villages. Evidence from this study suggests that the observed differences in morphology between the Sully burial areas can most likely be attributed to differential levels of inter-village admixture and not their temporal separation.