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

Abstract

Objectives: Differences in facial height and breadth between Okinawa Islanders and mainland Japanese have been reported in previous craniometric and somatometric studies. This study using three-dimensional (3D) images aimed to identify more detailed characteristics of facial morphology in each population.Methods: Using a hand-held 3D scanner, we obtained 60 facial surface images each from Okinawa Islanders and mainland Japanese. Twenty-one landmarks were plotted on a computer and 27 measurements of distances and angles between the landmarks were taken. Statistical analyses such as t test, principal component analysis (PCA), regression analysis, and discriminant analysis were performed to identify sex and regional differences, the patterns of facial features, factors explaining the facial patterns, and other features. Results: Okinawa Islanders showed lower facial and nasal heights than mainlandJapanese. Furthermore, we identified larger protrusions of the glabella and nasal root in Okinawa Islanders than in mainland Japanese. In the PCA, we observed components of facial shape patterns. These components mainly represented facial size (PC1), facial depth (PC2), the prominence of the glabella and nasal root (PC3), and facial breadth (PC4). We identified that the population difference is strongly associated with PC3. Conclusions:This study quantitatively identified differences in the facial morphology between Okinawa Islanders and mainland Japanese using 3D digital images, with special emphases on the differences in the nasal height and the prominence of the glabella and nasal root.

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

“…In this study, it was confirmed that the Ryukyuan people have a smaller height in the upper and midfacial region compared with the mainland Japanese; it was also confirmed that the height of the lower face was almost identical between the two groups (Pietrusewsky, 1999;Dodo et al, 2000;Fukase et al, 2012;Miyazato et al, 2014). Less prominent nasal bones (rhinion) were observed in the Ryukyuan females; this finding corresponded to previous findings regarding male crania from the early-modern period where more detailed analyses had revealed that the Ryukyuans have nasal bones curved on the sagittal section (Fukase et al, 2012).…”

“…Although a study of 3-D facial surface images indicated that the Ryukyuans have a larger glabellar protrusion than the mainland Japanese (Miyazato et al, 2014), our findings did not detect this difference based on any single measurement, probably because we used different baselines and because females have less distinctive features than males. However, results from our multivariate analyses may have suggested such a characteristic in the Ryukyuans; specifically, the glabella' t-radius (#102) showed a relatively large negative correlation at a loading of -0.577 with PC5, and PC5 showed smaller scores in Ryukyuan females than in mainland females; notably, the loadings for nasion' t-radius (#98) and subnasale' t-radius (#101) were -0.385 and 0.057, respectively.…”

“…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.…”

“…Miyazato et al (2014) have reported that, as a result of a stepwise discriminant analysis based on 27 measurements of 3-D facial surface images, two variables that represent facial height and glabella protrusion can be used to assign an individual to the population of origin (Ryukyuan or mainland Japanese) with cross-validated accuracies of 80.0% (males) and 66.7% (females). Compared with the previous study, the present study resulted in more accurate prediction of population membership for each individual by means of comprehensive measurements that include both hard and soft tissues.…”

“…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.…”