Fibular diaphyseal curvature of the Jomon population.

This study investigated differences in the fibular diaphyseal curvature between prehistoric Jomon hunter-gatherers and modern Japanese people. A total of 115 skeletal remains of 40 individuals from the Late/Final Jomon period (approximately 4300-2500 years BP) and 75 modern Japanese individuals were included in the analysis. The degree of anteroposterior and mediolateral diaphyseal curvature was measured based on digital photographs taken from the frontal and sagittal planes at every 5% diaphyseal region between the range of 20-80% of the fibular length. Fibular diaphyseal curvature was compared between both populations and sexes, and the correlation between fibular diaphyseal curvature with diaphyseal cross-sectional morphology and body size variables were confirmed. The results showed significant differences in the anteroposterior diaphyseal curvature between the Jomon and modern Japanese populations, and a significantly curved anterior direction was noted for Jomon males and females, compared with modern Japanese males and females. On the contrary, little populational difference was noted in terms of mediolateral diaphyseal curvature. The curvature of the fibular diaphysis showed less correlation with body size variables. Moreover, anteroposterior diaphyseal curvatures were correlated with diaphyseal robustness and had low correlation with diaphyseal shape. A relationship between anteroposterior curvature and diaphyseal cross-sectional morphology, an indicator of habitual activity, was confirmed. This suggests that the fibular curvature is possibly influenced by mechanical loading from daily activities as well.

Dorso-palmar elongation of the diaphysis of the third metacarpal bone in prehistoric Jomon people.

This study investigated cross-sectional morphological differences in the diaphysis of the third metacarpal bone (MC3) between prehistoric Jomon hunter-gatherers and modern Japanese people. Overall, 179 skeletal remains of 119 individuals (73 men and 46 women) from the Middle-to-Final Jomon period (3500 BC-500 BC) and 60 modern Japanese people (35 men and 25 women) were included in the analysis. Analyses were performed at the mid-shaft of the MC3 using linear measurement, elliptic Fourier analysis, and cross-sectional geometric properties. The standardized polar section modulus (ZpSTD) indicated sexual differences in both populations. The right MC3 was generally stronger than the left side. There was no populational difference in the ZpSTD in both sexes. In both men and women, the cross-sectional shape of the MC3 was relatively larger in the dorso-palmar direction than in the radioulnar direction in the Jomon population compared to the modern Japanese population. Sexual differences in cross-sectional shape were recognized only in the Jomon population, with the dorso-palmar elongation being greater in Jomon men than in women (particularly when comparing the left MC3). There was a significant side difference in the diaphyseal shape among Jomon women, with the right MC3 being relatively larger in the dorso-palmar direction. These findings were consistent, although skeletal remains of the Jomon population were excavated from different regions. Differences in the diaphyseal cross-sectional shape between populations suggest differences in habitual loading on MC3 associated with differences in subsistence behavior. Furthermore, differences in diaphyseal shape and strength between Jomon men and women suggest sexual division of labor, with men performing bimanual tasks and women performing unimanual tasks.

Diaphyseal cross-sectional geometry of the metatarsal bones in the Jomon population.

OBJECTIVES: This study aimed to investigate differences in the diaphyseal cross-sectional geometry (CSG) of the metatarsal bones (MTs) between two populations with different habitual activities: the Jomon hunter-gatherers and modern Japanese people. MATERIALS AND METHODS: We evaluated the first through fifth MTs of 117 skeleton samples: 59 (33 men and 26 women) were obtained from Late and Final Jomon period archeological sites and 58 (31 men and 27 women) were from modern Japanese people. CSG properties were calculated at the mid-shaft of the MTs and the relative values of the polar section modulus (Zp ) of each second-to-fifth MTs to first MTs were calculated. These variables were compared according to population and sex. RESULTS: Many of the CSG properties of MTs, except first MTs, were higher in the Jomon population than in the modern Japanese population for both sexes. Additionally, the relative values of the Zp of the MTs were higher in Jomon men and women than in modern Japanese men and women. Moreover, the Jomon population had sex-based differences in the ratio of the shape of third MTs and fourth MTs and the relative MTs value. Jomon women had elliptical third MTs and fourth MTs, and the relative Zp values of the third-to-fifth MTs to first MTs were higher in Jomon women than in Jomon men. DISCUSSION: Our result suggests that the habitual activity of the Jomon population placed heavy loads on the forefoot. This finding possibly relates to mediolateral forefoot loading that appears to be related to traversing uneven terrain.

The characteristic mid-shaft cross-sectional shape of the ulna in Jomon hunter-gatherers.

OBJECTIVES: The Jomon people were hunter-gatherers who inhabited the Japanese archipelago between 10,000 BC and 300 BC. Here, we focus on the mid-shaft cross-sectional shape of the ulna in the Jomon population and compare it with modern Japanese people. MATERIALS AND METHODS: Jomon specimens, including 32 males and 22 females, were excavated from shell mound sites in the Pacific and Seto inland coastal area of Honshu island in the Japanese archipelago dated to the Late-to-Final Jomon phase (between 2,000 BC and 300 BC). Mid-shaft ulna cross-sectional shapes were compared with modern Japanese specimens (25 males, 21 females) using standard linear measurements and elliptic Fourier analysis (EFA). Differences from both sides of this element were compared using predicted handedness. RESULTS: Linear measurements and EFA results show that ulna shape of both sexes within the Jomon population are relatively larger in the antero-posterior direction and have more developed posterior borders than modern Japanese males and females. No significant differences were observed between Jomon sexes based on the predicted dominant side, but differences were evident in the predicted nondominant side. At the same time, bilateral differences were recognized in Jomon females, because of a lower level of posterior border development in the predicted nondominant side compared to the dominant side. DISCUSSION: Shape differences between Jomon people and modern Japanese can be explained by variation in the habitual loading of the ulna. Sexual dimorphism in ulna shape within the Jomon population suggests division of labor differences.

Morphological features of the fibula in Jomon hunter-gatherers from the shell mounds of the Pacific coastal area.

OBJECTIVE: The Jomon, one of the ancestral populations of modern Japanese, were hunter-gatherers inhabiting the Japanese archipelago from 11,000 to 300 BC. We evaluated changes in the diaphyseal morphology of the fibula from the middle to the final phase of the Jomon period, compared to the morphology of other historical and modern populations from the Japanese archipelago, to elucidate temporal changes in habitual activities and possible division of labor among males and females. MATERIAL AND METHOD: Jomon specimens of 107 males and 97 females were obtained from the shell mounds of the Pacific coastal area of East Japan, distinguishing between middle (3,000-2,000 BC) and late-final (2,000-300 BC) phases of the Jomon period. Mid-shaft morphology of the fibula and tibia were compared to morphological measurements of specimens from Yayoi (37 males, 28 females), medieval (56 males, 56 females), early modern (51 males, 50 females), and modern (125 males, 68 females) periods. RESULT: Largest values of fibular areas and relative fibular-to-tibial areas were identified in males from the late-final Jomon phase, compared to the middle Jomon phase and after the Yayoi period. These period-specific differences in fibular area were smaller in females, with the largest between-sex difference identified in the late-final Jomon phase. DISCUSSION: Results confirm a change in the habitual activity pattern of males in the late-final phase. Males of the late-final Jomon phase likely did more long-distance traveling to the inland/mountainous region, as part of an ecological change that occurred during the middle to the late-final Jomon phase. Am J Phys Anthropol 160:708-718, 2016. © 2016 Wiley Periodicals, Inc.

Severe erosive polyarthritis in a human skeleton dated to the early modern period of Japan.

A human skeleton apparently afflicted with severe polyarthritis was unearthed from an early modern grave at the Tamukai site in the northernmost part of Honshu in Japan. The bones, likely from a late middle-aged male, showed severe resorptive lesions and ankylosis in many of the peripheral joints. Lesions were found in both bilateral and symmetrical distributions, sometimes accompanied by juxta-articular osteoporosis. Differential diagnoses included either rheumatoid arthritis, psoriatic arthritis, or leprosy, with psoriatic arthritis being the most likely. Whatever the final diagnosis, the identification of arthritis mutilans is clear. Because some bones were missing and a mixture of characteristics of both types of arthritis was evident, it was impossible to make a definitive diagnosis. However, this case is valuable for the severity of the lesions and the rarity of erosive polyarthritis found in archaeological skeletons from an Asian site.