論文

The purpose of this paper is to clarify the endocranial and postorbital morphologies of the terminal Pleistocene Minatogawa people, and obtain insights into their evolutionary background and genealogical relationships. The Minatogawa I and IV crania were compared with 83 Homo sapiens specimens (including 19 prehistoric Jomon). Metric comparative analyses and observational evaluations revealed that the two Minatogawa endocrania are characterized by a common suite of features (or tendency), including a small endocranial volume, relatively low endocranial shape, distinctly broad temporal region (qualitatively associated with the strong temporal bulge), weak parietal boss, and weakly swollen frontal bulge. Postorbital constriction was confirmed to be strong, relative to both upper facial breadth and maximum cranial breadth. Partial correlation analysis and bivariate comparisons were performed to examine the possible associations of Minatogawa's strong postorbital constriction. The results suggest that constriction relative to the face is predominantly due to a large facial breadth (frontal endocranium not so narrow in Minatogawa I), and also in part to strong neuro-orbital disjunction, while constriction relative to the posterior cranium is largely attributable to endocranial shape. Comparisons with modern/recent H. sapiens materials and limited but informative outgroup specimens (Skhul V, and an example of Homo erectus, Daka) suggests that some of the features characteristic of Minatogawa are possibly ancestral retentions of early H. sapiens (e.g. strong temporal bulge, marked postorbital constriction relative to the face), while others are probably derived population features (e.g. a small endocranial volume, weakly swollen frontal bulge, marked postorbital constriction relative to the posterior cranium). In overall endocranial proportions, the Jomon tend to lie closer to Minatogawa than does the modern Japanese, but such morphologies were also found in individuals of other populations, and thus the similarity does not necessarily support the hypothesis of Minatogawa-Jomon genealogical closeness. © 2012 The Anthropological Society of Nippon.

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. © 2011 The Anthropological Society of Nippon.

© 2015 Elsevier Ltd. Previous analyses of dental size in Gigantopithecus blacki indicated marked sexual dimorphism and a trend towards increasing size through time. These studies were based on a sample of over 700 teeth from five localities excavated prior to 1990. Since then, 12 additional cave sites have been discovered in southern China, yielding hundreds of isolated teeth of G. blacki. Most of these sites are well dated by a combination of biochronology and absolute dating methods, so we now have a much better understanding of the chronology of G. blacki. Here, we reexamine the degree of sexual dimorphism and the question of dental size increase through time in G. blacki based on the expanded collections now available. Our results show that sexual dimorphism is not as marked as indicated in previous studies and confirm earlier analyses suggesting that the postcanine teeth of G.blacki tend to become larger through time from the beginning of the Early Pleistocene to the Middle Pleistocene.

The thickness of mammalian tooth enamel plays a prominent role in paleontology because it correlates with diet, and thicker enamel protects against tooth breakage and wear. Hominid evolutionary studies have stressed the importance of this character for over 30 years, from the identification of "Ramapithecus" as an early Miocene hominid, to the recent discovery that the earliest hominids display molar enamel intermediate in thickness between extant chimpanzees and Australopithecus. Enamel thickness remains largely unexplored for nonhominoid primate fossils, though there is significant variation across modern species. Despite the importance of enamel thickness variation to primate evolution, the mechanisms underlying variation in this trait have not yet been elucidated. We report here on the first quantitative genetic analysis of primate enamel thickness, an analysis based on 506 pedigreed baboons from a captive breeding colony. Computed tomography analysis of 44 Papio mandibular molars shows a zone of sufficiently uniform enamel thickness on the lateral surface of the protoconid. With this knowledge, we developed a caliper metric measurement protocol for use on baboon molars worn to within this zone, enabling the collection of a data set large enough for genetic analyses. Quantitative genetic analyses show that a significant portion of the phenotypic variance in enamel thickness is due to the additive effects of genes and is independent of sex and tooth size. Our models predict that enamel thickness could rapidly track dietary adaptive shifts through geological time, thus increasing the potential for homoplasy in this character. These results have implications for analyses of hominoid enamel thickness variation, and provide a foundation from which to explore the evolution of this phenotype in the papionin fossil record. © 2004 Wiley-Liss, Inc.

A Homo erectus calvarium [Sambungmacan 4 (Sm 4)] was recovered from Pleistocene sediments at Sambungmacan in central Java. Micro-computed tomography analysis shows a modern human-like cranial base flexion associated with a low platycephalic vault, implying that the evolution of human cranial gobularity was independent of cranial base flexion. The overall morphology of Sm 4 is intermediate between that of earlier and later Javanese Homo erectus; apparent morphological specializations are more strongly expressed in the latter. This supports the hypothesis that later Pleistocene Javanese populations were substantially isolated and made minimal contributions to the ancestry of modern humans.

© 2016 Macmillan Publishers Limited. All rights reserved. The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma). Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So'a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ∼0.7 Ma, these fossils now constitute the oldest hominin remains from Flores. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.

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. © 2009 The Anthropological Society of Nippon.

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 largetoothed 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. © 2011 The Anthropological Society of Nippon.

Molar enamel thickness is a key feature in the study of hominid evolution. Our understanding of enamel thickness and distribution patterns, however, has so far been based mostly on the limited information available from physical cross sections of the crown. In this study, the 3-dimensional (3D) whole crown enamel distribution pattern was explored in 74 extant great ape and modern human molars. Serial cross sections obtained from microfocal X-ray computed tomography were used to generate digital molar reconstructions at 50 to 80 micron voxel resolution, each crown represented by two to five million voxels. Surface data of both enamel dentine junction (EDJ) and outer enamel were extracted to derive volumetric measures, surface areas, curvilinear distances, and whole crown radial thickness maps. Three-dimensional average enamel thickness (AET) was defined as enamel volume divided by EDJ surface area. In 3D AET relative to tooth size, Homo exhibited the thickest, Gorilla the thinnest, and Pan and Pongo intermediately thick enamel. This result differs from previous claims that molar enamel of Pongo is relatively thicker than that of Pan. The discrepancy between three and two-dimensional (2D) values of AET stems from a combination of local differences in within tooth enamel distribution pattern and EDJ topography between Pan and Pongo molars. It demonstrates that 2D AET is not an appropriate substitute or estimator of whole crown AET. Examination of whole crown 3D distributions of molar enamel revealed a pattern common to all four examined species, the "functional" side of the molar having thicker enamel than the opposite side. However, some unique aspects of each species were also apparent. While the Gorilla molar has relatively thin enamel throughout its crown, Pan molars are characterized by particularly thin enamel in the occlusal fovea, and Pongo molars by an accentuation of relatively thin basal and thick occlusal enamel. Human molars are characterized by relatively thick enamel throughout the crown, with relatively large contrasts between buccal and lingual, and between mesial and distal crown portions. The ancestral condition common to the four extant species can be estimated by interpreting molar enamel distribution patterns unique to each genus as likely to be derived. We hypothesize that the last common ancestor likely had intermediately thick enamel, without particular thickening (or thinning) of enamel either occlusally or basally.

© 2013 Elsevier Ltd and INQUA. Gigantopithecus blacki is a typical member of the Stegodon-Ailuropoda faunal complex (sensu lato) that inhabited southern China or, more broadly, mainland Southeast Asia during the Early and Middle Pleistocene. Current evidence indicates that the giant ape became extinct during the Middle Pleistocene. Recently, new remains of Gblacki and associated mammalian fossils have been unearthed from a karst cave site, Hejiang Cave, in Chongzuo City, Guangxi, South China. The age of the Gigantopithecus-bearing depositional unit is estimated to be 400-320ka using 230Th-234U disequilibrium U-series dating of flowstone samples bracketing the deposits. These finds document the latest occurrence of Gigantopithecus and provide potential insights regarding its extinction. Comparisons of dental dimensions between the Hejiang G. blacki remains, more than four hundred isolated teeth from Early Pleistocene localities, and over ninety isolated teeth from local drugstores show that the Hejiang teeth are slightly larger in their buccolingual dimensions. In addition, the crowns of the three unerupted upper premolars differ from those of all of the other Gigantopithecus material in having more complex crenulations. The differences in dental dimensions and morphology are possibly reflective of dietary responses to environmental changes that eventually led to the extinction of Gigantopithecus.

The Middle Awash Ardipithecus ramidus sample comprises over 145 teeth, including associated maxillary and mandibular sets. These help reveal the earliest stages of human evolution. Ar. ramidus lacks the postcanine megadontia of Australopithecus. Its molars have thinner enamel and are functionally less durable than those of Australopithecus but lack the derived Pan pattern of thin occlusal enamel associated with ripe-fruit frugivory. The Ar. ramidus dental morphology and wear pattern are consistent with a partially terrestrial, omnivorous/frugivorous niche. Analyses show that the ARA-VP-6/500 skeleton is female and that Ar. ramidus was nearly monomorphic in canine size and shape. The canine/lower third premolar complex indicates a reduction of canine size and honing capacity early in hominid evolution, possibly driven by selection targeted on the male upper canine.

Mammalian fossils of the Konso Formation (southwestern Main Ethiopian Rift) derive from stratigraphic intervals dated to between 2.0 Ma and younger than 1.3 Ma. Systematic paleontological collecting resulted in almost 8, 000 identifiable mammalian specimens representing 8 orders, 22 families, and more than 68 species including Australopithecus boisei and Homo erectus. Despite geographic proximity to the Turkana Basin (approximately 200 km), aspects of the Konso fauna are distinctive, with its 1.9–1.7 Ma assemblage showing some degree of endemism. Bovids Megalotragus, Parmularius altidens, Parmularius eppsi, Menelikia, and Pelorovis, all common at Turkana and/or Olduvai, are rare or absent at Konso, while Parmularius cf. pandatus, Simatherium, and Notochoerus n. sp. of the Konso assemblages are the youngest known records of these taxa in eastern Africa. The dominant suid of this assemblage is Kolpochoerus majus, a previously poorly known taxon. Subsequent to circa 1.7 Ma, an influx of external elements occurred, possibly related to a general East African trend of climatic drying between 1.8 and 1.6 Ma. The post-1.5 Ma Konso fauna is characterized by apparently immigrant dry grassland adapted bovids, such as Damaliscus niro and Parmularius angustieomis. Metridiochoerus compactus, Metridiochoerus hopwoodi and Metridiochoerus modestus are common in the 1.5 to 1.3 Ma levels at Konso, whereas the latter two suids are rare at Turkana. The post-1.5 Ma Kolpochoerus limneteslolduvaiensis of Konso is morphologically more conservative than time-equivalent Turkana specimens. The post-1.5 Ma Konso Elephas rechi represents an evolutionary grade immediately preceding the fully advanced E. rechi rechi condition. © 2003 by the Society of Vertebrate Paleontology.