Relative chronology of the Minatogawa and the Upper Minatogawa series of human remains from Okinawa Island, Japan

A series of human fossils, the so-called 'Minatogawa Man' material, unearthed from the fissure site at the Minatogawa limestone quarry on Okinawa Island, is well known as the best preserved Pleistocene human remains in Japan. Another series of 'Upper Minatogawa' human remains was also recovered from the same fissure site. Although the Upper Minatogawa series was supposed to be derived from higher horizons than the Minatogawa series, and this supposition was provisionally supported by the fluorine dating of bones, the chronological and/or stratigraphical relationships of individual human specimens have nevertheless not been clarified. Here we report newly obtained data on the relative chronology of the Minatogawa and the Upper Minatogawa series by additional element analyses (strontium and barium) of bones, and draw the following inferences: (1) the Upper Minatogawa human remains are younger than the Minatogawa human remains (i.e. 'Minatogawa Man') as a group; (2) however, a wider age range is implied for the 'Minatogawa Man' series, and some of the specimens such as Minatogawa IV and maybe Minatogawa II are comparable in age to the Upper Minatogawa series. Thus, the 'Minatogawa Man' series may not comprise a single chronological group, although they may be of one morphological group. We also discuss the geological age of the Minatogawa fossil assemblages, and address preliminary palaeoanthropological implications concerning the population history of the Japanese archipelago in the Late Pleistocene.