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.

Comparative analysis of facial morphology between Okinawa Islanders and mainland Japanese using three‐dimensional images

“…These characteristics have also been emphasized in several craniometric studies (Hsu, 1948;Ikeda, 1974;Fukase et al, 2012). We observed that the angle of Ac(m)-Se-Prn is larger in Okinawa Islanders than in mainland Japanese but that the nasal prominence (Prn-RP) is not much different between the populations.…”

“…In studies of early modern crania, it has also been reported that the bizygomatic, biorbital, and mandibular breadths are broader in crania from the Okinawa Islands than those from mainland Japanese (Hsu, 1948;Fukase et al, 2012). Therefore, a broad face has generally been considered to be a characteristic of Okinawa Islanders.…”

“…However, Fukase et al (2012) recently pointed out that Ryukyuan faces are not flat from the lateral view when compared with mainland Japanese faces. Although the Jomon and the Ainu have a larger simotic subtense, i.e., more prominent nasal root, than mainland Japanese and the Ryukyuans, the difference in the simotic index between mainland Japanese and the Ryukyuans is likely to result from the larger simotic chord in the Ryukyuans than in mainland Japanese (Yamaguchi, 1973;Dodo et al, 2000;Hanihara, 2000;Fukase et al, 2012). Consequently, Okinawa Islanders have a broader nasal bone and simultaneously larger depth from the eye to the nasal root In the PCA, we observed components of facial shape patterns.…”

A comparative study of craniofacial measurements between Ryukyuan and mainland Japanese females using lateral cephalometric images

“…The craniofacial morphology of ancient and modern people in the Japanese archipelago has been well studied (von Baelz, 1911;Ikeda, 1974;Brace and Nagai, 1982;Hanihara, 1991;Ishida, 1992;Pietrusewsky, 1999;Dodo et al, 2000;Higa et al, 2003;Fukumine et al, 2006;Haneji et al, 2007;Toma et al, 2007;Fukase et al, 2012;Miyazato et al, 2014). Such studies have revealed that craniofacial features, including dental characteristics, show regional differences even within Japan, especially between the mainland Japanese, Ryukyu Islanders, and Ainu.…”

“…Fukase et al (2012) have pointed out that the crania of earlymodern Ryukyu Islanders have, on average, a lower facial height, a broader interorbital space, and sagittally more curved nasal bones than those of the modern mainland Japanese. Based on 3-D facial surface images of living subjects, Miyazato et al (2014) have found that the Ryukyuan people have more prominent glabella and nasal roots, as well as lower facial and nasal heights.…”