We investigated the influence of squatting posture on 343 adult human tali and 227 adult tibiae of the early-modern period from Kumejima, Okinawa, Japan. The prevalence of medial squatting facets (malleolar and trochlear surface extensions) in the Kumejima series was as high as that in recent main-island Japanese. Right medial squatting facets were more frequent than left ones, especially in females. However, we found only lateral squatting facets at the lower end of the tibia in the Kumejima series, while the frequency was quite low, especially in females, among East Asians. This finding corresponded to the low frequency of lateral extension of the trochlear surface of the talus. The prevalence of these facets was significantly higher among males than among females, suggesting that males habitually assumed a squatting position more frequently than females did in the early-modern period. These studies suggested that peoples of the early-modern Kumejima Island did not have as many customs involving a squatting position as the early-modern and modern main-land Japanese.

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To identify similarities in morphological characteristics between the Jomon/Ainu and early to late historic inhabitants of the Tohoku region, we performed metric and nonmetric analyses of the cranial series of protohistoric Kofun from southern Tohoku and early modern Edo from northern Tohoku. The skulls of the eastern Japan Jomon, Hokkaido Ainu, and Kofun and Edo peoples in Kanto and northern Kyushu were used for comparison. Analyses based on Mahalanobis’ generalized distance (D²) and discriminant analyses were performed, using 18 cranial measurements. Nonmetric analyses were based on Smith’s Mean Measure of Divergence (MMD), computed using 6 cranial nonmetric traits, which are noted to have few interobserver errors and to be effective for discriminating between Japanese subpopulations. In both approaches for applying D² and MMD, the Ainu exhibit the most significant similarity to the Jomon, followed by the southern Tohoku Kofun. A clear geographical cline in cranial metric and nonmetric traits: Kyushu→Kanto→Tohoku→Hokkaido (Ainu/Jomon), was observed in both cases of the Kofun and Edo periods. A similar geographical cline was also noted in the results of discriminant analyses. Such geographical clines have suggested that the Kofun period inhabitants in northern Tohoku, not covered by the present study, were closer to the Jomon/Ainu group than those in southern Tohoku. Since the morphological difference between the ancient Japanese in the Tohoku region (Emishi as described in ancient documents) and the Jomon/Ainu is clinal, disputes over “the racial identification of ancient Emishi” of whether they were Ainu or Japanese, do not appear to be significant.

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Studies of the regional variation of morphological traits of Japanese are aimed at clarification of population history. Some metric traits of the modern Japanese show a concentric circular regional variation: the people in central Japan around the Kinki District are morphologically different from those in peripheral regions. The purposes of this study are to examine metric traits of early modern Japanese crania in the Kinki District and to clarify regional variation at this period. The materials measured here are composed of 34 male crania from the Sakai Kango Toshi and Kosenji sites (Sakai, Japan) in the late 17th to early 19th centuries. The Sakai crania which have brachicephalic and higher cranial vaults and higher and narrower faces than other contemporary ones suggest that a concentric distribution existed in the early modern period, and it continues to exist in the modern period.

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The periosteal dimensions, medullary area, and intra-cortical porosity of the femoral midshaft cross section were measured by using the recent Japanese materials (77 males, aged 20 to 81 years, and 39 females, aged 22 to 74 years), in order to further investigate age-related bone geometrical changes during adulthood. The midshaft cross sections were captured by micro-CT scanning. The samples were divided by age into three subgroups: YOUNG (20–49 years), MIDDLE (50–64 years), and OLD (65+ years). Differences among the subgroups were statistically examined by performing the t-test and Mann-Whitney U test. It was found that, in both sexes, there were no significant differences in the periosteal dimensions (the anteroposterior and mediolateral diameters and the total area) between YOUNG and MIDDLE and between YOUNG and OLD, indicating no femoral periosteal expansion during adulthood. In males there were no significant differences in the medullary area between YOUNG and MIDDLE and between YOUNG and OLD, while in females MIDDLE (P = 0.06) and OLD (P < 0.05) had the greater medullary area than YOUNG. The female medullary area tended to remain almost constant from their mid-20s to 40s and to increase remarkably from their 50s to 70s. These findings indicate a close relationship between menopause (decrease of female hormone) and increased endosteal resorption of femoral diaphysis. It was also found that in both sexes the intra-cortical porosity of older individuals tended to be greater than those of younger individuals, highly porous cross sections were observed particularly in females after the mid-30s. The results of the present study indicate that the functional adaptation compensating for age-related weakening of bone substance by periosteal expansion had not taken place in the recent Japanese femora, and that females have higher risk of age-related weakening of femoral diaphysis in comparison with males.

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