1. Division of Human Evolution Studies; Graduate School of Medicine, Hokkaido University; Hokkaido 060-8638 Japan
2. Division of Anthropology; Department of Biological Science; Graduate School of Science, The University of Tokyo; Tokyo 113-0033 Japan
3. Department of Human Biology and Anatomy; Graduate School of Medicine, University of the Ryukyus; Okinawa 903-0215 Japan