Why humeri of the Jomon people are so thick?: Imprications from its inter-site variation

Abstract

Human limb bone shafts grow thicker in response to activity levels experienced by individuals. This knowledge can be used to reconstruct lives of prehistoric people. Previous studies demonstrated that limb bone thickness of the Jomon people, prehistoric hunter-gatherer-fishers in Japan, vary with period and location. However, further tests are required for these observations because of the relatively small samples analyzed, insufficient examinations of inter-site differences and inter-observer errors in measurements, and the lack of control of possible effect of bone size on its thickness. In the present study, by analyzing relative shaft thickness and focusing on inter-site variability, we examine spatiotemporal variation in humeral shaft thickness using a sample of 1003 prehistoric individuals from various sites in the Japanese Archipelago (from Okinawa to Hokkaido), which includes 797 Jomon individuals. The results show that the humeral thickness increased from the Initial Jomon phase onward; the Jomon humeri are thicker in coastal populations than in inland plain populations; inter-site variation is present even among the coastal groups from the same chronological phase; and the patterns of inter-site variation are different between males and females. Of particular interest is the outstanding thickness seen in the males from the Hobi shellmound site located at the tip of the Atsumi Peninsula. We hypothesize that this was caused by not only fishing in the outer sea, but also active marine transportation by rowing boats.