Comparison of population structure in Ohio's Late Archaic and Late Prehistoric periods

Previous studies of population structure among prehistoric groups in the Oh io valley region have shown that hunting-gathering populations exhibited a different structure than horticultural populations. Among both Late Archaic hunter-gatherers and Late Prehistoric horticulturists, covariance structur es for cranial metrics were found to be homogenous within the populations, but the Late Archaic subpopulations showed little differentiation while the Late Prehistoric subpopulations exhibited a marked differentiation. Biodis tance based on cranial discrete trait frequency showed similar patterns, bu t in the Late Archaic discrete trait distance was associated significantly with the geographical distance separating populations. The present investig ation is an extension of the previous studies increasing the Late Prehistor ic sample (n = 8 samples and n = 341 individuals) and using the Harpending- Ward model, modified for use with multivariate quantitative data, to estima te the effects of differential gene flow and the amount of differentiation within populations. Results of the present analyses indicate that different iation among subpopulations, measured by minimum F-ST, was greater in the L ate Prehistoric compared to the Late Archaic period. However, for both peri ods the minimum Fs, is comparable to values found for historic native popul ations of the northeast woodlands. Analysis of differential gene flow in th e Late Archaic period indicates that geographically peripheral populations were affected more by external gene flow than more central populations. Lat e Prehistoric populations exhibit a very complex pattern of differential ge ne flow. We discuss the latter pattern in terms of proposed culture change in the Late Prehistoric period of Ohio. (C) 2000 Wiley-Liss, Inc.