Biological distance at the Ryan Mound site.

ABSTRACT

OBJECTIVES: The Ryan Mound site in California spans 2000 years and has been utilized in over 200 studies. The Ryan Mound has been assumed to be a culturally and, therefore, a biologically continuous population over time. This study attempts to determine whether adults at the Ryan Mound consisted of a continuous population over the span of three temporal periods by using nonmetric skeletal traits. MATERIALS AND METHODS: Thirty-eight nonmetric cranial traits and four nonmetric post-cranial traits were scored on adults. Trait correlations were assessed for sex and age using chi-square and Fisher's exact tests. For bilateral traits, data were recorded for both sides, but only results from the left side are reported. Most data were recorded as present or absent. Twelve traits had scores that had more than two nominal categories, which were converted to binary values to enable mean measure of divergence (MMD) statistical analyses. RESULTS: After data reduction, 36 traits remained. Using these traits, standardized MMD analyses revealed that the oldest temporal period and the most recent temporal period individuals were significantly different. CONCLUSION: This study illustrates the importance of testing for biological continuity. Nonmetric studies provide a way to examine relationships within a sample to determine biological continuity. For the Ryan Mound, new populations may have moved into the region early on as part of the Meganos intrusion, or new populations may have moved into the region later, between AD 1500 and AD 1800. Comparative data from nearby sites further support the Meganos intrusion theory.