Ontogeny of limb proportions in late through final Jomon period foragers

Abstract

This study reports on developmental patterning in the intralimb indices of Late/Final Jomon period (4000-2300 BP) people. Jomon foragers represent the descendants of migrants from Northeast Asia, who arrived in the Japanese Islands around 20,000 BP. Among adults, Jomon brachial indices are elevated and similar to warm adapted, low latitude people, while crural indices are intermediate and similar to people from moderate latitudes. Two hypotheses regarding the development of intralimb indices among Jomon period foragers are tested: (1) intralimb indices of Jomon people maintain predicted ecogeographic relationships over ontogeny; (2) greater evolvability will be observed in the brachial index, while greater developmental constraint will be observed in the crural index. Changes in intralimb proportions in a Jomon skeletal growth series are compared to those in two contrasting samples: Inuit from Point Hope (cold adapted) and Nubians from Kulubnarti (warm adapted). A quadratic equation best describes the ontogeny of brachial and crural indices, with high indices in infancy followed by a decline in childhood and an increase in adolescence. Despite these shifts, ecogeographically predicted differences and similarities in the indices are maintained between samples throughout ontogeny. In addition, radial relative to humeral length is significantly less correlated than tibial relative to femoral length. These results suggest genetic conservation of intralimb indices over the course of development. However, radial and humeral lengths are less correlated than tibial and femoral lengths among Jomon subadults and adults, potentially suggesting greater evolvability of the brachial index and more developmental constraint on the crural index.