Late Pleistocene modern human mandibles from the Minatogawa Fissure site, Okinawa, Japan: morphological affinities and implications for modern human dispersals in East Asia

The Late Pleistocene modern human skeletal remains from the Minatogawa Fissure site, Okinawa, are important because of their exceptional completeness. This paper presents the first detailed morphological description of the five mandibular specimens from Minatogawa, which probably belong to two male and two female individuals (two of the five specimens likely belong to the same male individual). Intensive metric and non-metric comparisons with the mandibles of the Jomon Holocene hunter-gatherers from mainland Japan indicate that the Minatogawa mandibles are different from the Jomon condition in many respects: a tendency toward alveolar prognathism, relatively rounded chin morphology, low anterior corpus heights, a large mental foramen, a small ramus, etc. The Jomon mandibles show chronological and geographic variations in some of these traits, but the morphology of Minatogawa is distinct even if such variations are taken into consideration. These observations caution against uncritical acceptance of the traditional view that supposes genealogical relationships between Minatogawa and Jomon. Some characteristics of the Minatogawa mandibles (e.g. alveolar prognathism and relatively small ramus) are shared with Australo-Melanesians, among other modern human populations. Based on these findings, we hypothesize that the Minatogawa people were derived from prehistoric Southeast Asian populations with Australo-Melanesian affinities.