Recent fossil records have suggested that human erect bipedal locomotion started in Africa probably more than 6 million years ago. However, debate continues regarding how locomotion was acquired by our prehuman ancestors. Fossils and the genetic traits of recent humans and animals cannot answer this question directly. Therefore, the present paper reviews acquisition models of human bipedalism and explanations regarding how humans acquired bipedalism based on a comparative kinesiology of contemporary mammal species. Nonhuman primates are adequate models of human bipedal acquisition because of not only the phylogenetically close relationship with humans, but also the trend toward hindlimb dominance and orthograde positional behavior in daily life. Although dissimilar to the erect bipedalism seen in humans, nonhuman primates adopt bipedal positional behavior in the wild. All nonhuman primates use the arboreal environment, but some groups of species utilize the ground predominantly. Compared with relatively terrestrial nonhuman primates, relatively arboreal primates show more similarities with humans in their bipedal locomotion. Comparisons among primate species and between nonhuman primates and nonprimate mammals indicate that human-like bipedal characteristics are strongly related to arboreal life. Our prehuman ancestors likely started and adapted to bipedal locomotion while living in trees; this process is referred to as the generalized arboreal activity model. When humans began terrestrial locomotion, they likely performed proficient bipedalism from the first step. The generalized arboreal activity model presented here does not contradict the fossil records.
This paper examines periodontal disease as well as other oral health indicators of the Jomon population in order to understand variations in their lifestyle and their response to dietary diversity. The oral conditions of three Jomon populations in Late Jomon period are evaluated using two periodontal indicators, namely the distance measured between the cement–enamel junction to the alveolar crest (CEJ-AC distance), and the degree of inflammation of the alveolar septum. The incidence of affected individuals with moderate to severe periodontal disease ranges from 31.8% to 38.6% based on the evaluation of the CEJ-AC distance, and from 38.4% to 66.0 % based on the interdental septum morphology, respectively. Comparisons of the inter-site difference (which includes that between coastal and inland populations) and sex differences were conducted with a combined dataset of the periodontal and oral health indicators (caries, antemortem tooth loss, wear, and chipping). The results indicated that inter-site and inter-sex differences are smaller in the cases with periodontal disease than in those with caries and antemortem tooth loss. In particular, almost no difference was found in the periodontal conditions between the coastal and inland sites. Although previous studies have indicated the effect of occlusal wear on the CEJ-AC distance, the results of the multivariate analysis show that the inflammation of the interdental septum is more relevant than the occlusal wear. In addition, the sex difference was significant compared to the inter-site difference, and each sex difference within a site showed a common trend. Detected inter-site and sex differences are discussed and assumed to be associated with bioarchaeological background.
Linear enamel hypoplasia (LEH) is a useful indicator of childhood health. This study aimed at investigating whether there was any diachronic change in LEH occurrence during the Edo period (1603–1867). The Edo period, which experienced no major transition in subsistence and had no large-scale contact with foreign population, did undergo various social changes that could have affected childhood health status. The skeletal remains of 144 adult individuals recovered from seven burial sites in Tokyo were examined. Based on historical records and archaeological evidence, these individuals were divided into two time-period groups, the early Edo period and the late Edo period. Each group was then subdivided into the two age-at-death groups of young and old. The late Edo period groups were also divided into coffin-type groups, which reflect their social status. Comparison of general prevalence, frequency distribution, and the mean number of LEHs observed per tooth revealed that the individuals of the late Edo period groups of any coffin type tend to have fewer LEHs than those of the early Edo period groups, and significant differences were found either in the frequency distribution or in the mean number of LEHs per tooth. Considering the possible factors that could affect the result, such as age-at-death distribution and social status, the observed difference between the time periods can be attributed to diachronic change, which is assumed to be due to improvements in childhood health status during the Edo period. This assumption is compatible with historical evidence suggesting that the living environment in the city of Edo was improving in the 17th century and stabilized in the 18th century as a result of the establishment of basic infrastructure and improvements in public safety. The findings of this study will help us understand childhood health status in a changing society.
The individual-count method of bilateral nonmetric traits has been widely used despite its apparent defects in both theory and practice. Logically, its use means adopting the false concept of ‘two thresholds’ based on the single-liability model. This conceptual defect can create actual problems, including that of conventional ‘tetrachoric correlation.’ The correlation coefficient calculated by formally applying the tetrachoric procedure to the individual-count frequencies is mathematically meaningless because there exists no true liability and threshold that can explain such data. Moreover, it considerably underestimates the correlation if it is used as the estimate of the correlation between the individual-specific components of liability because it neglects the contribution of the inter-side component in the variance of total liability. Two statistical methods are proposed to estimate the correlation coefficient between inter-individual components of liability and its confidence interval. Some selected data from the database published by Ossenberg on the Internet were used to illustrate the utility of the new methods and to examine the problem of the conventional method. The method of estimation of the correlation between the inter-individual components of liability based on the combination of two dual-liability models provided, as a by-product, substantial support for the standard threshold model based on data. Because the conventional ‘tetrachoric correlations’ proved to seriously underestimate the correlations, the results of almost all studies using Mahalanobis distances based on nonmetric traits so far published may require re-evaluation. It is also argued that a fundamental problem exists in the use of the individual-count method itself. Adopting an incorrect method for maintaining comparability is a vicious cycle. It is necessary to emphasize improving the reliability of future studies based on true statistics rather than keeping the comparability between less reliable results based on the false concept of threshold.
Cranial vault thickness is a widely studied variable in physical anthropology. However, direct physical measurements are difficult to assess in complete skulls, where the endocranial surface is not easily accessible for standard callipers. Computed tomography represents the best alternative, but is expensive and not always available for many field or museum samples. In this study we present a method for the measurement of cranial vault thickness based on magnetism. We measured bone thickness at 71 points of the vault in 30 human skulls with the use of a portable magnetic calliper, which offers a simple, direct, non-invasive, and cost-effective methodology. Magnetic measures were compared with physical measures sampled with a traditional spreading calliper, and error analysis was assessed. Thickness distribution was evaluated and represented in bidimensional maps after spatial interpolation. The two types of callipers provide the same results, suggesting that the magnetic calliper can be used in those situations in which a traditional calliper is not applicable. In accordance with previously published data, the most variable and thickest bones in our sample were the frontal and the occipital bones, and cranial vault thickness distribution follows a pattern of increasing thickness from lateral regions of the vault to the sagittal plane. The magnetic calliper is a reliable and effective tool to measure cranial thickness in those cases in which the endocranial surface is not easily accessible, and where expensive technology cannot be employed for economic or practical reasons.
Recent studies suggest that acquired syphilis evolved in the Old World from a non-sexually transmitted treponeme originating in the New World during early European expansion and colonization. However, when and via which route the bacteria were introduced into Asia remains uncertain. This study examined the first paleopathological evidence of syphilitic infection in an individual from the 19th century AD in South Korea. The individuals from a site identified as the middle and late Joseon period were examined for the presence of the skeletal lesions that are indicative of an acquired syphilitic infection. Direct macroscopic observation of the skeletal remains was conducted alongside radiological analysis. One individual displayed extensive pathologies throughout the cranial and postcranial skeleton. Treponematosis is the only disease that best explains the pattern of lytic cranial lesions and widespread bilateral symmetrical periosteal new bone of the postcranial elements. To date, paleopathological evidence of treponemal disease in Asia is severely limited. In this regard, this study provides meaningful data for studying the history of infectious disease in Asia. This study represents the only known archaeological case in South Korea.
Recent studies have revealed that the Jomon people are considerably genetically different from any other population, including modern-day Japanese. This gives rise to an intriguing question: when after the Jomon era did this drastic change of genetic features occur? The Shomyoji shell midden site in Kanagawa, Japan can provide some clues to address this question. The skeletons buried at this site include some that are more recent than the Jomon-era skeletons with whom they are almost contiguously buried. We tested the genetic continuity of the Shomyoji shell midden people by analyzing mitochondrial DNA (mtDNA). Our results show that the mtDNA haplogroups of the Kofun and Heian skeletons vastly differ from those of the Jomon skeletons. This finding implies that the genetic conversion of the Japanese people may have occurred during or before the Kofun era, at least at the Shomyoji site. To confirm this hypothesis, nuclear genome analysis of the Shomyoji people is considered promising.
The relationship between calcaneal size and body mass in extant primates and other land mammals is examined using regression analyses to provide simple equations for estimating the body mass of extinct primate and land mammal species based on the calcaneus. The results imply that among the linear calcaneal dimensions, the calcaneal width at the talar articular surfaces (CA2) is likely the best body mass estimator for land mammals (including primates), and the width of the posterior talar articular surface (CA3) appears to be relatively good body mass estimator for primates. The equation with a 95% prediction interval for estimating the body mass (BM, in g) using CA2 (in mm) for land mammals is: BM = exp(2.928 × ln CA2 + 0.981 ± 0.772) × 1.076; the corresponding equation using CA3 (in mm) for primates is: BM = exp(2.555 × ln CA3 + 3.536 ± 0.641) × 1.067.