Twin research design, involving comparisons of similarities in monozygotic (MZ) and dizygotic (DZ) twin pairs, has enabled researchers to quantify the relative contributions of genetic and environmental factors to variation in many dental traits. In this study we analyzed peg-shaped tooth form of the maxillary lateral incisor, divided into the size and shape elements by the macroscopic observation. We compared the lateral incisor between the right and left sides, and between twins. The concordance ratios in which the reduced expression was found on both sides and both twins were calculated. The concordance ratio between twins was larger in MZ than in DZ, but an environmental factor was considered to be strongly related because the ratio was 50–60%. Since the concordance ratio was larger in the size element than in the shape, it is thought that hereditary factors strongly influenced the tooth size. In recent studies the differences between MZ twins is more focused rather than the similarities. The differences in this dental trait may also be explained by epigenetic influences.

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In this paper, the author summarizes the basic principles for analyzing the environments surrounding human remains given the excavated condition of bones, based on the idea that disparities in bone movement arise depending on whether the environment surrounding a body at the time of its burial was “filled” or “unfilled” (Nara, 2007). The author refers to the environments surrounding human remains from the time of their burial to the completion of skeletonization as either “filled” or “unfilled,” and, by presenting instances in which unfilled environments transform into filled environments during the course of skeletonization, the author notes the need to view environmental change in terms of time. Furthermore, it is considered that two patterns exist for “partially unfilled environments” in which a portion of the remains are unconcealed: conditions occurring in a transformation of an unfilled environment into a filled environment (such as landslides, etc.), or conditions occurring at the time of the burial of the body due to factors such as wrapping, etc. In addition, the author proposes a methodology that allows for the differentiation of each pattern as well as the re-creation of specific environmental changes by studying the excavated condition of human bones in view of temporal change. The author tested this methodology against 42 sets of human bones from the middle to late Jomon period unearthed at the Kitamura Site, conducting an analysis of the environment surrounding said remains. First, it was demonstrated that sinkage occurs even in filled environments due to decomposition of the body, that bones move depending on their burial position, and that pottery covering the face or the stone under the head were factors in bone movement. The results were that clearly discernable human bones made up 95.2% of the test specimens, and that the majority of analyses of environments surrounding human remains utilizing bones were valid.

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Histomorphological investigation of fragmentary osteal remains is a useful technique for human and nonhuman animal bone identification. Several burnt bone fragments of the ancient Heian period were unearthed from the Asahiyama (2) site in Aomori Prefecture. The bone fragments were so small that species identification was impossible by gross anatomy alone. For the purpose of discrimination between human and nonhuman bones, microscopic observations and bone histomorphometry were performed for four samples of diaphyseal cross-sections of limb bones from the Asahiyama (2) site. Limb bones of humans, bear, horse, swine, sika deer, Japanese serow, and cattle were prepared for comparison. The results of histomorphometric analyses of human and nonhuman materials showed that the Haversian canal area (H.Ar) and the proportion of the Haversian canal area to the osteon area (H-On index) of humans were significantly larger than those of nonhumans, so these variables were efficient indicators for distinguishing human from nonhuman bones. In view of bone shrinkage by burning, three bone samples from the Asahiyama (2) site were considered to be human bones. The other sample was also similar to human bones, but the possibility of it being a horse bone could not be ruled out. The osteal remains were estimated to be cremated human bones, and as such indicated that the cremation custom existed in the Aomori district in the ancient Heian period.

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[in Japanese]

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