A morphological study on the growth patterns of ancient people in the northern Kyushu-Yamaguchi region, Japan

This study investigated the growth patterns of morphometric features of ancient people determined from historic and prehistoric skeletal remains. Subadult skeletons from the Yayoi, medieval, and modem periods were used. The age of each skeleton was estimated from dental formation standards. Measurement methods followed standard anthropological methodology established for the adult skeleton. Quadratic regression formulae that showed the highest coefficient of determination were chosen to evaluate plausible growth patterns. The results are as follows. (1) The neurocranium of the medieval people showed a possible difference in growth pattern compared with the modem people. The cause of this difference is discussed in relation to brachycephalization. (2) In all the groups studied here, over the course of growth, the height of the lower facial region increases much more than that of the upper facial region. With this change, the contour of the orbit changes into a relatively wider-lower shape, and the contour of the nasal cavity shifts with age from a relatively wider-lower to a narrower-higher condition. (3) In all the groups studied here, over the course of growth, the nasal bones become more curved transversely. However, the angle of the frontal process of the maxilla, which forms the lateral sides of the nasal bones, changes only slightly, if at all. (4) Secular differences in mandibular morphology related to chewing stress emerge at an older age than do the regional differences of the Yayoi people's facial morphology, an effect that is probably related to genealogy. (5) Analysis of femur length suggests that the Yayoi people in the northern Kyushu and Yamaguchi region experienced less growth disruption than did the other people studied here.