Archaeological study of the social structure of the Jomon period has advanced through discoveries about the relative positions of graves, the presence or absence therein of accessories and grave goods, head orientations of corpses, types of tooth extraction, and so on. In recent years, research using anthropological information—both physical and biological—obtained from excavated human bones has begun to elucidate the social structures of that time. This approach is called bioarchaeology. In the analysis of the social structure of the Jomon period, bioarchaeology has three principal uses: to reconstruct burial subgroups by ¹⁴C dating of human bones; to estimate genetic relationships between adjacent human bones; and to estimate the proportion of migrants in the overall population. Here, I review the analysis of the cemetery of the Odake shell-mound as an example of bioarchaeological research while touching on the history of archaeological research of Jomon social structure.

Banjo-shuseki-bo, unique accumulations of human bones among Jomon collective secondary burials, have been found intensively in the Final Jomon Period Mikawa region of Aichi Prefecture. At the Hobi shell-mound site in Tahara City (c. 3000–2400 BP), two cases of banjo-shuseki-bo have been so far documented, referred to as Ichi-go-shuseki (Accumulation No. 1) and B-shuseki (Accumulation B). During the 2010–2013 excavations at the Hobi site, we discovered a new case of banjo-shuseki-bo (named Accumulation 2010) and retrieved all the bones (1331 samples). Here we report anthropological data from this unpublished sample and confirm the differences between the three accumulations (2010, No. 1, and B) and individual skeletons of primary burial origin from the same archaeological site. The Accumulation 2010 bones contained 13 individuals in total: eight adult males; one subadult (late adolescent) male; three adult females; and a 1.5-year-old child of undetermined sex, thus indicating a male-dominated group. It was also found that the body-part composition of Accumulation 2010 exhibited a site-specific bias, specifically skewed toward the lower limb bones such as the femur and tibia, almost equivalent to those of Accumulations No. 1 and B. In comparisons of the femur between the banjo-shuseki-bo human bones and individual skeletons, no systematic size differences were found in either sex; however, the male femora from the three (2010, No. 1, and B) accumulations showed a significantly/near-significantly greater pilasteric index than those of the individual skeletons. One possible explanation for why the femur pilasteric structure was so developed in the Hobi banjo-shuseki-bo males is that people who worked in physically demanding labor during their lives or a specific kinship group may have been chosen as the subjects of the banjo-shuseki-bo burials.

Many human skeletal remains of the Late–Final Jomon period have been found in shell-mounds on the Atsumi peninsula in Aichi Prefecture, Japan. Several types of burials have been found, such as mass burial and bone-gathering burials arranged like a square board (banjo-shuseki burial). In this study, strontium isotope analysis was performed to reveal the meanings of banjo-shuseki burials. The materials included 22 samples of tooth enamel and bones from the Hobi shell-mound, and 30 samples from the Ikawazu shell-mound. The concentration of calcium and strontium was measured, as were the strontium isotope ratios. The results indicated that the tooth enamel from the banjo-shuseki burial exhibited higher strontium isotope ratios than those of tooth enamel from the single burial in Hobi. The tooth enamel from the banjo-shuseki burial and a mass burial in Ikawazu included some individuals with higher strontium isotope ratios. These ratios were higher than the range of the values of human bone samples, modern plants around the sites, and the enamel of terrestrial animals, indicating the possibility that these people grew up in a different place to the sites where they were buried. The individuals in the banjo-shuseki burials may include immigrants who grew up in other areas or their diets incorporated food from other areas.

Ritual tooth ablation was a characteristic form of body expression for the prehistoric Jomon people. During the 2010–2013 excavation at the Hobi shell-mound site, Aichi Prefecture, Japan, a new case of secondary collective burial, banjo-shuseki-bo, was discovered, in which additional cases of ritual tooth ablation were present in human skeletal remains. Here we describe the morphology and tooth extraction status of individual mandibles, and assess the interindividual relationships on the basis of tooth crown diameter. Although a certain degree of kin relation was predicted among individuals from the new collective burial, which seems comparable to those found in modern Japanese twin pairs, almost the same degree of close kin relationship was detected in interindividual variation and in intersite variation with the neighboring Jomon sites.

A draft whole genome sequence of a Jomon woman from the Ikawazu shell-mound site has been reported recently. The adult woman, IK002, was excavated with a child, IK001. Because of the burial situation with the child located above the adult, the two individuals were thought to be a mother–child relationship. In this study, we conducted a target capture sequencing, and obtained 258-fold coverage of the complete mitochondrial (mt) genome sequence of IK001. Comparing the mtDNA nucleotide sequences of IK001 and IK002, we found these were unambiguously different from each other. Thus, the mitogenome sequence analysis clarified that both have a non-mother–child relationship. This result sheds new light on the relationship between burial and kinship in Jomon archaeology.

This paper discusses a probable case of pediatric mandibular osteomyelitis (OM) from the east Hokkaido Okhotsk (5th–13th century AD) site of Moyoro, Japan. The remains of a young child present an unusual mandibular lesion exhibiting two main features: (1) cortical thickening reflecting periosteal new bone formation, and (2) lytic alveolar destruction with associated antemortem tooth loss. The lesion was examined macroscopically, microscopically, and via computed tomography imaging. A differential diagnosis—considering lesion appearance, location, and the age of the child—is most consistent with OM, while alveolar and dental involvement suggest an odontogenic source such as an infected tooth germ. The infection appears to have been active at the time of death and chronic (i.e. of 4+ weeks) in duration, an interpretation supported by enamel hypoplastic evidence of physiological stress in the preceding 12–18 months. The lesion’s unique appearance highlights the diverse manifestation of OM, especially in the jaws and in the absence of modern therapeutic treatment. Despite being considered a relatively common condition among non-adult individuals in the past, surprisingly few cases of pediatric OM have been reported from archaeological contexts. This case, only the second documented on a mandible, contributes to the general paucity of paleopathological literature on OM.

Sexual dimorphism in a population varies over time due to temporal changes and data on this need to be updated regularly. Further, each population needs its own sex-discriminating anthropometric standards, which can be used on unknown skeletal remains of that population. Sex estimation of fragmented, buried, or burnt remains in which sex-discriminating morphological traits are often impossible to discern presents a huge problem for anthropologists, archaeologists, and forensic experts. The mandible—a strong bone usually found with other skeletal remains—is considered highly sexually dimorphic. In the current study, we investigated the reliability of mandibular dimorphism for sex estimation using 17 variables in the contemporary Indian population. The study included 385 adult mandibles of known sex and age collected from the two medical colleges in northern India. After the measurement of all variables, they were subjected to discriminant function analysis. All variables showed significantly larger dimensions in males except one. The most dimorphic variables included length measurements followed by height; breadth measurements were the least dimorphic. The gonion–gnathion length emerged as the most dimorphic parameter, with sexing of 79.5%. The stepwise and direct analysis resulted in 81.1% and 84.7% accuracy, representing the mandible as highly dimorphic. Factors that affect sexing accuracy and selection of the best variables are also explored and discussed.