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Papers - Kono, Reiko

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Mandibular tooth root size in modern Japanese, prehistoric Jomon, and Late Pleistocene Minatogawa human fossils

Suwa G., Fukase H., Kono R., Kubo D., Fujitakubo M.

Anthropological Science (Anthropological Science) 119 ( 2 ) 159 - 171 2011.10

Single Work, Accepted, ISSN 09187960

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.

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デジタル解析からみた港川人

河野　礼子

科学 80 ( 4 ) 378 - 380 2010

Single Work

Paleobiological implications of the Ardipithecus ramidus dentition.

Suwa G., Kono R., Simpson S., Asfaw B., Owen Lovejoy C., White T.

Science (Science) 326 ( 5949 ) 94 - 99 2009.10

Single Work, ISSN 00368075

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.

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The Ardipithecus ramidus skull and its implications for hominid origins.

Suwa G., Asfaw B., Kono R., Kubo D., Owen Lovejoy C., White T.

Science (Science) 326 ( 5949 ) 2009.10

Single Work, ISSN 00368075

The highly fragmented and distorted skull of the adult skeleton ARA-VP-6/500 includes most of the dentition and preserves substantial parts of the face, vault, and base. Anatomical comparisons and micro-computed tomography-based analysis of this and other remains reveal prs-Australopithecus hominid craniofacial morphology and structure. The Ardipithecus ramidus skull exhibits a small endocranial capacity (300 to 350 cubic centimeters), small cranial size relative to body size, considerable midfacial projection, and a lack of modern African ape-like extreme lower facial prognathism. Its short posterior cranial base differs from that of both Pan troglodytes and P. paniscus. Ar. ramidus lacks the broad, anteriorly situated zygomaxillary facial skeleton developed in later Australopithecus. This combination of features is apparently shared by Sahelanthropus, showing that the Mio-Pliocene hominid cranium differed substantially from those of both extant apes and Australopithecus.

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Tomographic analysis of the Daka calvaria

Gilbert W., Holloway R., Kubo D., Kono R., Suwa G.

Homo erectus: Pleistocene Evidence from the Middle Awash, Ethiopia (Homo erectus: Pleistocene Evidence from the Middle Awash, Ethiopia) 329 - 347 2009.02

ISSN 9780520251205

Accuracy and precision of CT-based endocranial capacity estimations: a comparison with the conventional millet seed method and application to the Minatogawa 1 skull.

DAISUKE KUBO, REIKO T. KONO, AIKO SASO, SOUICHIRO MIZUSHIMA, GEN SUWA

Anthropological Science (Anthropological Science) 116 ( 1 ) 77 - 85 2008.05

Single Work, ISSN 09187960

An increasing number of studies determine endocranial capacity (ECC) digitally using serial computed tomographic (CT) scan data. However, the multiple causes of errors inherent in such measurements and the resulting degree of accuracy have not yet been fully examined. In the present study, five observers estimated the ECCs of two modern human crania by segmentation of CT data (voxel size 0.380 mm) and by means of the conventional millet seed method. The ECC estimations were much more consistent in the CT-based (technical error, TEM = 1.4 cc) than the millet seed (TEM = 11.8 cc) methods. The estimated capacities also tended to be larger in the latter, suggesting possible systematic bias. Next, the causes and degree of error in the CT-based method were examined. Error due to size calibration of the CT images was no more than 3 cc (± 1.5 cc) per 1000 cc. Errors involved in delineating the endocranial cavity were evaluated as follows. First, we adopted a segmentation routine in which a single global threshold value was applied to most of the volume, and then supplemented locally by more appropriate values in the regions where the global value was insufficient. We then estimated the potential error introduced by choosing a global threshold value. We found this to be within 5 cc (per 1000 cc). This error range increased to 7.5 cc (per 1000 cc), when using a lower resolution data set (slice thickness 1.14 mm). Another source of interobserver error involves the blocking of foramina and canals, which we estimated to be less than 2 cc (per 1000 cc). Adding these various effects, our investigations indicate that ECC estimations based on high-resolution CT data are accurate to within ± 5 cc per 1000 cc. Finally, we reevaluated the ECC of the Minatogawa 1 skull to be 1335 cc (with a probable range of 1327-1343 ± 5 cc), considerably smaller than the originally reported value of 1390 cc obtained by the millet seed method. © 2007 The Anthropological Society of Nippon.

Enamel distribution patterns of extant human and hominoid molars: occlusal versus lateral enamel thickness.

河野　礼子

Bulletin of the National Museum of Nature and Science, Series D (Anthropology) 34 1 - 9 2008

Single Work

A new species of great ape from the late Miocene epoch in Ethiopia

SUWA Gen, KONO Reiko T., KATOH Shigehiro, ASFAW Berhane, BEYENE Yonas

Nature (Nature) 448 ( 7156 ) 921 - 924 2007.08

Joint Work, ISSN 00280836

With the discovery of Ardipithecus, Orrorin and Sahelanthropus, our knowledge of hominid evolution before the emergence of Pliocene species of Australopithecus has significantly increased, extending the hominid fossil record back to at least 6 million years (Myr) ago. However, because of the dearth of fossil hominoid remains in sub-Saharan Africa spanning the period 12-7 Myr ago, nothing is known of the actual timing and mode of divergence of the African ape and hominid lineages. Most genomic-based studies suggest a late divergence date - 5-6 Myr ago and 6-8 Myr ago for the human-chimp and human-gorilla splits, respectively - and some palaeontological and molecular analyses hypothesize a Eurasian origin of the African ape and hominid clade. We report here the discovery and recognition of a new species of great ape, Chororapithecus abyssinicus, from the 10-10.5-Myr-old deposits of the Chorora Formation at the southern margin of the Afar rift. To the best of our knowledge, these are the first fossils of a large-bodied Miocene ape from the African continent north of Kenya. They exhibit a gorilla-sized dentition that combines distinct shearing crests with thick enamel on its 'functional' side cusps. Visualization of the enamel-dentine junction by micro-computed tomography reveals shearing crest features that partly resemble the modern gorilla condition. These features represent genetically based structural modifications probably associated with an initial adaptation to a comparatively fibrous diet. The relatively flat cuspal enamel-dentine junction and thick enamel, however, suggest a concurrent adaptation to hard and/or abrasive food items. The combined evidence suggests that Chororapithecus may be a basal member of the gorilla clade, and that the latter exhibited some amount of adaptive and phyletic diversity at around 10-11 Myr ago. ©2007 Nature Publishing Group.

Asa Issie, Aramis and the origin of Australopithecus

White T., WoldeGabriel G., Asfaw B., Ambrose S., Beyene Y., Bernor R., Boisserie J., Currie B., Gilbert H., Haile-Selassie Y., Hart W., Hlusko L., Howell F., Kono R., Lehmann T., Louchart A., Lovejoy C., Renne P., Saegusa H., Vrba E., Wesselman H., Suwa G.

Nature (Nature) 440 ( 7086 ) 883 - 889 2006.04

Single Work, ISSN 00280836

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominids such as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, the probable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awash study area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are from chronometrically controlled stratigraphic sequences and date to about 4.1-4.2 million years ago. They include diagnostic craniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These new fossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus and Au. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving either replacement or accelerated phyletic evolution. © 2006 Nature Publishing Group.

A micro-CT based study of linear enamel thickness in the mesial cusp section of human molars: reevaluation of methodology and assessment of within-tooth, serial, and individual variation.

GEN SUWA, REIKO T. KONO

Anthropological Science (Anthropological Science) 113 ( 3 ) 273 - 289 2005.12

Joint Work, ISSN 09187960

Enamel thickness was investigated in the mesial cusp section of 167 unworn human molars by means of non-destructive micro-CT based methodology. Serial sections of the entire crown were taken at a voxel resolution of 28 microns, and the initial volume data set of each molar was standardized in orientation to obtain a vertical section that accurately contains the dentine tips of the two mesial cusps. Enamel thickness at the cusp tips, occlusal basin, and lateral crown face was measured in the mesial cusp section and in sections offset from that section by 0.6 mm. We found that thickness at the cusp tips may be overestimated in offset sections by up to about 1 mm, and those of the occlusal basin overestimated or underestimated by up to about 0.5 mm. We also found that maximum 'radial' thickness of the lateral crown face was least affected by section position, usually with discrepancies of less than about 0.1-0.2 mm. In all serial positions in both upper and lower molars, a 'functional' (lingual in uppers and buccal in lowers) to 'non-functional' side gradient in enamel thickness was observed in cusp tip, occlusal basin, and lateral crown face enamel, with the exception of the characteristically thin enamel at the protoconid and paracone cusp tips. Serial differences in thickness were seen between the thinner M1 and the two posterior molars in many but not all measures of thickness, the pattern of which appears to be influenced by the thin M1 mesiobuccal cusp enamel. Individual variation of maximum lateral thickness, the least variable measure of thickness, was found to be substantial (a 30-60% range) even with serial and buccolingual positions controlled. Correlation between whole crown average enamel thickness and maximum lateral thickness was high, indicating that the latter is a potentially useful predictor of overall enamel thickness of the molar crown. The present results indicate that interspecific comparisons of enamel thickness must be made with careful attention to positional placement of thickness measures, potential serial differences, and intraspecific variation. © 2005 The Anthropological Society of Nippon.

Effects of molar crown orientation to measures of lateral enamel thickness in the mesial cusp section.

河野　礼子

Bulletin of the National Science Museum, Series D (Anthropology) 31 11 - 22 2005

Single Work

Molar enamel thickness and distribution patterns in extant great apes and humans: new insights based on a 3-dimensional whole crown perspective

REIKO T. KONO

Anthropological Science (Anthropological Science) 112 ( 2 ) 121 - 146 2004.08

Single Work, ISSN 09187960

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.

Genetics and the evolution of primate enamel thickness: A baboon model

Hlusko L., Suwa G., Kono R., Mahaney M.

American Journal of Physical Anthropology (American Journal of Physical Anthropology) 124 ( 3 ) 223 - 233 2004.07

Single Work, ISSN 00029483

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.

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Plio-Pleistocene terrestrial mammal assemblage from Konso, southern Ethiopia

Suwa G., Nakaya H., Asfaw B., Saegusa H., Amzaye A., Kono R., Beyene Y., Katoh S.

Journal of Vertebrate Paleontology (Journal of Vertebrate Paleontology) 23 ( 4 ) 901 - 916 2003.12

Single Work, ISSN 02724634

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.

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Homo erectus calvarium from the Pleistocene of Java

Baba H., Aziz F., Kaifu Y., Suwa G., Kono R., Jacobs T.

Science (Science) 299 ( 5611 ) 1384 - 1388 2003.02

Single Work, ISSN 00368075

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.

Comparison of intercusp distances between mandibular molars of Pan troglodytes and Homo sapiens

河野　礼子

Bulletin of the National Science Museum, Series D (Anthropology) 29 1 - 10 2003

Single Work

A three-dimensional analysis of enamel distribution patterns in human permanent first molars

Kono R., Suwa G., Tanijiri T.

Archives of Oral Biology (Archives of Oral Biology) 47 ( 12 ) 867 - 875 2002.12

ISSN 00039969

The morphology of the enamel cap and the thickness of the enamel of human molars are regarded as closely related to function. Previously, enamel thickness has been studied in specific sections only, not the distribution patterns of the entire crown. Here, the three-dimensional distribution pattern of the enamel of human permanent first molars was examined with a newly developed system. A distinctive pattern of enamel thickness common to all the individuals examined was found, regardless of the variation in absolute enamel thickness among individuals. It was confirmed that the lingual faces of upper molars and the buccal faces of lower molars have thicker enamel than the other crown faces. Moreover, in lower molars, enamel was significantly thicker at the hypoconid than at the protoconid crown face. The distal face tended to exhibit thicker enamel than either mesial or lingual faces, owing to the thicker hypoconulid enamel. It is suggested that the gradients of thickness within a molar are not necessarily manifested according to direction, but are the result of cusp-specific patterning. The distribution of enamel in the occlusal fovea was found to correspond to the morphology of the outer enamel surface, with the exception of the distinctly thin enamel at and near the tip of the mesiobuccal cusps in both upper and lower molars. The thickness of the enamel in that region might therefore be related to developmental timing or the topography of the enamel-dentine junction, rather than to functional demand. When viewed from a whole-crown, three-dimensional perspective, enamel thickness patterns are in part, but not entirely, explained as an adaptation to functional demand. © 2002 Elsevier Science Ltd. All rights reserved.

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A refined method of measuring basal crown and Cusp areas by use of a three-dimensional digitizing system

Suwa G., Kono-Takeuchi R.

Anthropological Science (Anthropological Science) 106 ( SUPPL. ) 95 - 105 1998.12

ISSN 09187960

In measuring basal crown and cusp areas of molars, one must determine a standard reference plane on which the projected measurements are made. In this paper, we present a new three-dimensionally based system which enables an objective determination of crown orientation. This is done by combining five laser scanned images of a molar taken occlusally and from four oblique angles to form a composite three-dimensional representation of the entire molar crown surface. Using this digitized data set, we derive a standard occlusal orientation that maximizes projected occlusal surface area. We can also choose other orientations for projection, such as those defined by the cervical line or cusp apices. Crown and cusp areas were measured in each of these orientations and compared for discrepancies on a mandibular first molar of Australopithecus afarensis. We found that orientations differ by more than 10 degrees, resulting in large discrepancies in cusp area values. It is concluded that, to enable reliable interpretation of cusp area data, whatever orientation methods used should be carefully chosen and rigidly followed.

A new method of evaluating enamel thickness based on a three-dimensional measuring system

Kono-Takeuchi R., Suwa G., Kanazawa E., Tanijiri T.

Anthropological Science (Anthropological Science) 105 ( 4 ) 217 - 229 1997.10

ISSN 09187960

In order to describe molar enamel thickness more accurately, a new measurement method using a laser triangulation system has been developed and its repeating accuracy was tested. The method was then applied to investigate the changing pattern of lateral enamel thickness along the distal protoconid crest. The results indicated that lateral enamel thickness at different sections tends to be comparable in relation to distance from the dentine tip. We expect this method to become an effective tool to investigate not only thickness of enamel but also its three-dimensional morphology.

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