Soichiro Kusaka

Homogeneous diet of contemporary Japanese inferred from stable isotope ratios of hair.

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of −19.4 ± 0.6‰ and 9.4 ± 0.6‰ (mean ± SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1‰, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C3 and C4 plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved.

Carbon isotope ratios of human tooth enamel record the evidence of terrestrial resource consumption during the Jomon period, Japan

OBJECTIVE Archaeological remains strongly suggest that the Holocene Japanese hunter-gatherers, the Jomon people, utilized terrestrial plants as their primary food source. However, carbon and nitrogen isotope analysis of bone collagen indicates that they primarily exploited marine resources. We hypothesize that this inconsistency stems from the route of protein synthesis and the different proportions of protein-derived carbon in tooth enamel versus bone collagen. Carbon isotope ratios from bone collagen reflect that of dietary protein and may provide a biased signal of diet, whereas isotope ratios from tooth enamel reflect the integrated diet from all macronutrients (carbohydrates, lipids, and proteins). METHODS In order to evaluate the differences in inferred diet between the archaeological evidence and bone collagen isotope data, this study investigated carbon isotopes in Jomon tooth enamel from four coastal sites of the Middle to Late-Final Jomon period (5,000-2,300 years BP). RESULTS Carbon isotope ratios of human teeth are as depleted as coeval terrestrial mammals, suggesting that C3 plants and terrestrial mammals were major dietary resources for the Jomon people. Dietary dependence on marine resources calculated from enamel was significantly lower than that calculated from bone collagen. The discrepancy in isotopic ratios between enamel and collagen and the nitrogen isotope ratio in collagen shows a negative correlation on individual and population levels, suggesting diets with variable proportions of terrestrial and marine resources. CONCLUSION This study highlights the usefulness of coupling tooth enamel and bone collagen in carbon isotopic studies to reconstruct prehistoric human diet. Am J Phys Anthropol 158:300-311, 2015.

Ecological and cultural shifts of hunter-gatherers of the Jomon period paralleled with environmental changes

OBJECTIVES Holocene hunter-gatherers adapted to climatic and environmental changes over time. Carbon and nitrogen stable isotope analysis of human skeletal remains from the Inariyama shell mound of the Final Jomon period have revealed large dietary variations in the population. This study analyzed radiocarbon dates of these individuals to test temporal changes in diet and its relationship with tooth ablation. MATERIALS AND METHODS Twenty-nine human skeletal remains from Inariyama were included in this study. Extracted bone collagen samples were purified to graphite. Then, radiocarbon dating of these samples was performed using the accelerator mass spectrometer. RESULTS The radiocarbon ages of Inariyama ranged about, 3,230-2,140 cal BP and showed three peaks of occupation. In the early and late phases, terrestrial resource consumption and incisor extraction were observed, while marine resource consumption and canine extraction were observed in the middle phase. DISCUSSION These temporal changes of diet and tooth ablation types occurred in parallel with climatic cooling and environmental change and help reveal how Holocene hunter-gatherers adapted to the changing environments.