The effect of size variation on univariate assessments of morphological difference in human crania

The present research was undertaken to determine the contribution of general size to craniometric variation in two previously described Paleo-Amerindian series, and to evaluate the effect of size variation on univariate assessments of morphological difference between the two. The analysis was based upon 19 measurements of 81 crania representing the Iswanid and Fort Ancient Muskogid varieties. The results of principal components analysis indicate that the 19 measurements can be represented as five principal component variates. Inspection of component eigenvectors indicates that variation in body size accounts for 40% of the variation within the metric data. Analysis of covariance lends support to the hypothesis that this size variation contributes substantially to statistical tests of difference between the two groups based on Student's t.