Ecological correlations between neurocranial and limb bone measurements: toward the solution of the brachycephalization problem

Abstract

As a step toward clarifying the causes of brachycephalization, ecological correlations, i.e. inter-group correlations, between neurocranial and limb bone measurements were investigated using Spearman’s rank correlation coefficient on the basis of 24 male and 23 female samples from prehistoric, historic and modern Japanese populations. It was found that there were significant ecological correlations common to males and females between cranial length and some thickness measurements of the radius, ulna, femur, and tibia, but no consistent correlations between cranial breadth and any limb bone measurements. These findings are compatible with one of the tendencies seen in previous intra-group analyses, and suggest that brachycephalization or dolichocephalization associated with cranial length may have been partly caused by diachronic change in the degree of development of skeletal muscles. This, in turn, may have occurred in accordance with diachronic changes in quality and quantity of available nutrition, physical activity, etc.