Facial characteristics of the prehistoric and early-modern inhabitants of the Okinawa islands in comparison to the contemporary people of Honshu

Abstract

Modern inhabitants of the Okinawa islands have been supposed to represent a relatively close genealogical connection to the prehistoric Jomon and the indigenous Ainu, when compared with people living on Japan’s main island (Honshu). However, several previous studies have also clarified some morphological facial traits discernible between the early-modern Okinawans and the Jomon of Honshu. In the present study, to further evaluate the Jomon–Okinawan relationship, we compared facial forms between skeletal samples from the Okinawa islands and Honshu, both in the Jomon and early-modern periods. Results of the comparisons showed that the Okinawa Jomon tended to possess a flatter interorbital region than the Honshu Jomon, but most measurements did not significantly differ between the two Jomon groups. This confirms that people sharing both Jomon culture and fundamental facial features lived throughout almost the entire Japanese archipelago, including the Okinawa islands. Results also demonstrated that the early-modern Okinawans had a significantly lower and broader face with transversely broader and flatter interorbital region than the early-modern Honshu Japanese. Such facial characteristics of the early-modern Okinawans qualitatively matched those of the Okinawa Jomon. However, compared with the Okinawa Jomon, the early-modern Okinawans exhibited an absolutely taller/narrower face and a further flatter nasal root. This could stem in part from a certain amount of population flow from surrounding regions during historic periods, as suggested by many earlier studies. Nevertheless, the results obtained in this study indicate that, comparatively, modern Okinawan people have retained physical traits including facial forms of the Jomon who survived in the same southernmost islands of the Japanese archipelago. Geographical variations of modern Japanese phenotypes should also be accounted for partly by those of the ancestral Jomon characteristics that were manifested by the end of the Jomon period.