Variation in Tibial Morphology of Three Arikara Skeletal Populations

The tibiae of the Arikara, a Northern South Dakota Plains Indian group, are analyzed to establish the biological affinities. The sample size is 232 tibiae representing 153 individuals. Three archaeological sites from the vicinity of Mobridge, South Dakota are represented, and they date between A.D. 1600-1832. Both univariate and multivariate statistical analyses are used to analyze the data.

The results indicate that intragroup variation follows a uniform pattern allowing the identification of common elements of tibial morphology. Age-related changes occur in several variables for the Larson group for which two ex-explanations are offered for consideration. No side differences occur in any variable of the Larson group. As expected, sex differences occur in practically every variable of all three groups. This indicates that size and shape variables of the tibia are good indicators of sex.

The results of the intergroup variation indicate that there are significant site differences. No temporal patterns are identified for site differences. These results agree with several Arikara craniometric studies, but they do not agree with all other Arikara postcraniometric studies. Perhaps the use of a larger variable set is responsible for the samples displaying group heterogeneity.

The differences in sexual dimorphism among the three Arikara groups indicate that genetic agents rather than environmental agents are responsible for the changing patterns of sexual dimorphism. One temporal pattern is identified for the female differences, and this pattern may be associated with the temporal patterns identified by Puskarich (1984) in the female Arikara pelvis.

In the future, analyses of the tibia should use larger variable sets that include cross-sectional geometric variables in order to prove or disprove the biomechanical explanations presented here.