The question of the origins of the Jomon population is examined by Campbell’s predictive approach, a method using ‘typicality probability’ which is currently the best way of comparing a single specimen with a reference population. Among the five Pleistocene fossils compared with a Late/Final Jomon sample from the Tohoku district, the analysis based on 13 cranial measurements revealed that Keilor from Australia was more likely a member of the Jomon population than Minatogawa I from Okinawa and Liujiang from southern China. Although, from a chronological viewpoint, it is not possible for Keilor to be an ancestor of the Jomon, these results suggest that the Australian Late Pleistocene population, or their ancestors, should also be considered when seeking the origins of the Jomon.
The Late Pleistocene human fossils recovered from the Minatogawa fissure in Okinawa Island are important in understanding the population history of the Japan archipelago. Based on high-resolution laser scanning, we conducted a three-dimensional (3-D) topographic evaluation of the glabellar and superciliary regions of the Minatogawa and Jomon crania. We aimed to address the question of whether the glabellar morphology of the Minatogawa crania can be seen as a possible ancestral condition of the Jomon people, or whether it more likely represents a distinct morphological pattern. In addition to comparative descriptions and evaluations of the visualized topography, we conducted principal components and cluster analyses using a data set of approximately 240 points located within a confined glabellofrontal area. Results indicate that the male Minatogawa I exhibits a distinct rhomboid to ovoid glabellosuperciliary prominence, in the form of an undifferentiated swollen structure that encompasses both glabellar and superciliary arch regions. Unlike the Jomon condition, this leads to a lack of concave inferolateral contour of the prominence and the virtually complete obliteration of bilateral superciliary expression. The Minatogawa II and IV female crania also exhibit the same morphological pattern at weaker levels. On the other hand, absolute glabellar projection of Minatogawa I is not as great as the developed Jomon examples. This indicates that it is the pattern that is distinctive of Minatogawa, rather than glabellar prominence itself.
The Late Pleistocene fossil human remains (individuals I–IV) of Minatogawa, Okinawa Island are important in addressing the population history of the Japanese archipelago and in understanding evolution of Homo sapiens in eastern Asia. This study is the first on Minatogawa I’s endocranial morphology, based on micro-computed tomography (micro-CT). We digitally reconstructed the Minatogawa I endocast, and created its physical model using a three-dimensional printer system. We compared the Minatogawa I endocast with available H. sapiens and archaic Homo endocasts. We found that Minatogawa I exhibits key derived endocranial features of H. sapiens, such as a highly elevated parietal, endocranial widening confined to a relatively anterior position, and a narrow internal occipital crest. The short, wide, and low proportioned Minatogawa I endocranium lies metrically at the margins of the modern human ranges of variation of this study. The Minatogawa I endocast exhibits a slightly underdeveloped frontal region with marked parasagittal ridges, a weak endocranial parietal boss, and a strong temporal bulge. It differs from Liujiang in the strong expression of these features as well as in overall metric proportions. A weak endocranial parietal boss and a strong temporal bulge are shared by Skhul V and Qafzeh 9, and may represent a primitive condition for H. sapiens in general.
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.
Although dental size and morphology have contributed to population history studies in Japan, little attention has been paid to root size and dimensions. We report here computer tomography (CT)-based metrics of mandibular tooth roots in modern Japanese, Holocene Jomon, and Late Pleistocene Minatogawa human fossils (15000–20000 BP). Our results confirmed that, in terms of both mesiodistal cervical diameters and root lengths, the Jomon is overall smaller-toothed, with summed mesiodistal cervical diameters 4% smaller than in the modern Japanese. However, no significant differences were found in the M1, in both cervical diameter and root length. These results are comparable to the crown size differences reported in the two populations. There were no significant differences in root proportions (root length relative to cervical diameter) between the Jomon and the modern Japanese in each tooth element from I1 to M1, while an allometric root length reduction was observed in the M2 and M3 of the modern Japanese. This reflects distinct patterns of dental reduction in the two populations. The Late Pleistocene Minatogawa fossils were found to have larger cervical diameters and root lengths than either the modern Japanese or the Jomon, in some respects approximating the large-toothed Australian and/or earlier Late Pleistocene Homo sapiens conditions. This indicates a largely conservative dental system retained in the Minatogawa fossils, distinct from the Jomon condition.
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.
In the present study, we estimated age at death of extinct deer (Cervus astylodon) excavated from two Late Pleistocene sites in Okinawa Island (the Hananda-Gama Cave and Yamashita-cho Cave I sites) from degree of molar wear. This was done using a regression equation of extant sika deer of known age, and deriving an age estimation equation based on M3 crown height applicable to fossil specimens. We then reconstructed mortality profiles using 45 and 88 individuals of the Hananda-Gama and Yamashita-cho assemblages, respectively, and compared the profiles with those of extant and archaeological (Jomon period) sika deer (C. nippon) populations. The reconstructed age profiles of both sites were strikingly different from the living and hunted Jomon period profiles in relative abundance of old adults. They were more similar to the attritional mortality profiles of the extant sika deer that died by natural causes (i.e. not by human or animal predation), but showed a further shift towards older age. Combined with the fact that there is no fossil evidence of medium- to large-sized carnivores on Okinawa Island during the Late Pleistocene, our results suggest that C. astylodon populations had extended longevity because of low predatory pressure, including that by Paleolithic human hunters.
The Minatogawa IV cranium is one of three well-preserved Late Pleistocene Homo sapiens crania from the Minatogawa fissure site, Okinawa Island. This cranium is more damaged than Minatogawa I and exhibits some clear post-mortem distortion. We reconstructed the endocranium of this specimen after correcting the distortion and breakage by combining digital and manual restoration procedures, and established a reliable estimate for its endocranial volume (ECV) to be around 1170 cc. As with the case of Minatogawa I, this result confirmed the suggestion of previous work that the Minatogawa series has small ECVs compared with modern Japanese and Jomon populations. Some dental and osteological conditions, such as heavy tooth wear as well as Harris’s lines of the long bones, suggest a possibility that the small ECV of the Minatogawa people as well as their short stature might have been caused in part by a stunting of growth due to undernutrition and possibly a microevolutionary adaptation to the food-limited insular environments.