Detection of millet use by isotope analysis of dentine collagen and enamel apatite in human teeth from the Last Jomon to Yayoi period

Abstract

To investigate the dietary shift that occurred during the transition from the Jomon to Yayoi period which saw the arrival of agriculture in Japan, we performed isotope analysis and radiocarbon dating on human tooth dentine and enamel excavated from archaeological sites in Gunma and Nagano Prefecture. Carbon and nitrogen stable isotope analysis of collagen extracted from dentine showed an average increase of 4.2‰ in δ¹³C between samples from Early Jomon and Last Jomon /Yayoi samples, while δ¹⁵N remained low with no significant change. A major candidate for the cause of this shift is C4 plants, represented by millets, that have a high δ¹³C and low δ¹⁵N. Carbon stable isotope analysis of enamel, on which plants have a more prominent effect compared to collagen, also showed an average increase of 5.2‰. These results suggest the adoption of millet in the Last Jomon to Yayoi period. Further examination that takes the variation of diet-to-eater isotopic spacing between herbivores and carnivores into consideration is in progress, in pursuit of a more quantitative evaluation of millet use.