1. Department of Legal Medicine, Toho University School of Medicine, Tokyo, Japan
2. Center for Accelerator Mass Spectrometry, Yamagata University Advanced Analysis Center, Yamagata, Japan
3. National Agriculture and Food Research Organization, Tsukuba, Japan
4. Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Chiyoda, Japan
5. Research Institute for the Dynamics of Civilizations, Okayama University, Okayama, Japan
6. Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan