Archaeological evidence indicates that dogs appeared in Japan at least 9300 years ago, during the Jomon period. The Jomon period dogs (Jomon dogs) retained the morphological characteristics of ancient domestic dogs throughout the Jomon period, possibly due to their geographical isolation from continental dogs. Therefore, we expect them to retain the genetic characteristics of ancient domestic dogs. To explore this possibility, we determined the mitochondrial genomes of five Jomon dogs, including one of the oldest dogs in Japan (7400–7200 cal BP), and seven late-8th-century Japanese dogs (Suwada dogs). We analyzed these sequences with 719 mitochondrial genomes of ancient and modern canids. The dog mitochondrial DNA (mtDNA) sequences have been grouped into six clades (haplogroups A–F), and clade A comprises six sub-clades (sub-haplogroups A1–A6). Classification of the Jomon dogs’ mtDNA haplotypes revealed that these dogs belong to a nested A2/A3 sub-haplogroup not shared by other modern or ancient samples. The mtDNA sequences of Jomon dogs form a monophyletic clade which is sister to the A3 sub-clade in the phylogenetic trees. Network analysis showed that the Jomon dogs’ mtDNA sub-clade diverged close to the base of the A2 and A3 haplotype network, which was centered by an ancient dog from South China. The Jomon dog mtDNAs diverged from A3 (~11500 years ago) soon after the A2 and A3 divergence (~12800 years ago), indicating early divergence of the Jomon dogs’ sub-clade. These results suggest that the Jomon dogs were possibly introduced into the Japanese archipelago 11500–9300 years ago. The mtDNAs of late-8th-century dogs were more diverse and were different haplogroups than that of Jomon dogs, suggesting that other haplogroups likely replaced the haplogroup of Jomon dogs through the introduction of dogs that accompanied the migration of people into Japan in later periods.

The axial and appendicular skeleton of Japanese macaques (Macacca fuscata) trained to adopt bipedal posture and locomotion display a number of functionally related external and internal macro- and micromorphological changes, including site-specific cortical and trabecular bone adaptations. In this study we use high-resolution microtomography scanning to analyse the three-dimensional distribution of the trabecular architecture of the proximal femur and proximal tibia of Sansuke, a male individual trained in bipedal performances for eight years, as well as five wild individuals. The distribution and architecture of trabecular bone in the femoral head of Sansuke is distinct from that found in wild M. fuscata individuals, with a unique bone reinforcement around the region of the fovea capitis. Conversely, wild individuals exhibit two pillar-like, high-density structures (converging in an inverted cone) that reach distinct regions of the posterior and anterior surfaces of the femoral head. For Sansuke’s proximal tibia, contrary to previous observations from the corticotrabecular complex distribution at the plateau, our results do not show a more asymmetric distribution between medial and lateral condyles with a medial reinforcement. Additionally, relative bone volume in this region is not significantly higher in Sansuke. However, we observed a slightly more medially placed bone reinforcement in the lateral condyle compared with the wild individuals as well as a slightly higher trabecular bone anisotropy in the medial than in the lateral condyle not observed in the wild individuals. These analyses provide new evidence about the nature and extent of functionally related adaptive arrangements of the trabecular network at the coxofemoral and the knee joints in individuals recurrently experiencing atypical load.

The development of the modern industrialized food production system has resulted in a homogeneous human diet worldwide. However, it is not clear whether a developed food production system led to a homogenized human diet also in ancient societies. Due to the lack of large archaeological datasets, we know little about the chronological trends and ancient circumstances of dietary homogenization. Here we compiled carbon and nitrogen stable isotope ratios, indicators of palaeodiet, of adult human skeletons from premodern mainland Japan (AD 1603–1868, n = 318) to investigate chronological changes in diet. Comparison with datasets from Japan in modern, premodern (Edo), and foraging (Jomon) periods showed that the human diet was rapidly homogenized isotopically in modern times. Premodern people in Japan typically obtained dietary proteins from C3 crops and fish, and the establishment of agriculture created a new isotope dietary niche compared with the foraging period. Dominant protein contributions from agricultural C3 crops cultivated with organic fertilizers and/or rice that are grown in paddy fields with denitrification increased premodern human nitrogen isotope ratios without increasing their carbon isotope ratios. Diet differed according to the social status of individuals or the availability of foods, and a unique diet can be seen in people in higher social classes such as the Shogun family. Meta-analysis of stable isotope ratios of archaeological human skeletons enables a comprehensive understanding of human dietary change through time and regional variations.

We studied linear enamel hypoplasia (LEH) in cranial series representative of Eurasian farmers with divergent lifestyles and natural environments: Siberian Russian settlers and Joseon dynasty people. The teeth of Siberian settlers and Joseon people of the 16^th–19^th centuries were examined in this study. We inspected specimens to detect signs of LEH, and the intergroup prevalence was statistically compared. The proportions of LEH were compared by age and sex across each group. Statistical analysis was performed with R software. Russian settlers’ LEH incidence per individual was 4.1% (3/73), whereas that of the Joseon people was 61.5% (56/91). In the case of LEH per tooth, Russian settlers and Joseon Koreans exhibited rates of 1.9% (24/1297) and 16.8% (336/2001), respectively. The statistical difference in the incidence of LEH between the two groups was highly significant (per individual: P = 9.188 × 10^–14; per tooth: P < 2.2 × 10^–16). The prevalence of LEH was observed to be much higher in the Joseon population than in the West Siberian settlers. In conclusion, we hypothesize that East Asian people’s physiological stress in childhood was far higher than that of Russian settlers. Historical LEH frequency on the Eurasian continent was truly diverse, possibly due to divergent stress conditions affecting different groups of people.

Numerous studies have shown that human dentition traits vary both between and within populations. However, there is still little knowledge about how dental tissue proportions differ between modern human groups. In this study, two samples of European and African individuals were compared to assess the possible differences and similarities present in the dental tissue dimensions of their permanent canines. For this purpose, the volumes and surface areas of the coronal dentine and pulp complex and the enamel cap of 127 canines were measured by microcomputed tomography. The results show the existence of interpopulation variability in the dental tissue pattern of both samples, which is mainly due to the presence of a larger enamel component in the African population, while dentine seems to play a less critical role in the differences described between both dental samples. We also observed a similar pattern of sexual dimorphism in the dental tissue proportions of European and African canines, but in this case, the intrapopulation variability was mainly due to the presence of a greater dentine component in males. Therefore, because the dimensions of dental tissues vary at both inter- and intrapopulation levels in modern human groups, our results highlight the importance of selecting comparative samples that are geographically mixed and sex-balanced for future paleoanthropological investigations on dental tissue patterns of extinct and extant species to avoid overestimating or underestimating any possible similarities or differences.