Showing papers in "Anthropological Science in 2008"

Root and canal morphology of human permanent teeth in a Sri Lankan and Japanese population

Abstract: The main purpose of this study was to investigate the root and canal morphology of Sri Lankan and Japanese permanent dentition. Two thousand Sri Lankan and 976 Japanese permanent teeth were examined. The number of roots in premolars and molars and the prevalence of C-shaped (gutter shaped) roots in mandibular second molars were recorded. Root canal morphology was studied using a clearing technique. The examination of root canal systems of the teeth was based on Vertucci’s classification. A higher prevalence of two-rooted maxillary first premolars was observed in Sri Lankans than in Japanese. Sri Lankan maxillary first and second premolars displayed a higher incidence of two canal and two apical foramina forms than those of Japanese. Canal morphology of mandibular first premolars showed higher occurrence of two canals with type V (1-2) canal configuration in Sri Lankans than in Japanese. In mandibular molars, Japanese presented with a higher incidence of three-rooted first molars and one-rooted second molars than Sri Lankans. C-shaped root was seen in 5.7% of Sri Lankan and 18.8% of Japanese second molars examined. In the distal root of mandibular first molars, Japanese showed a higher prevalence of two apical foramina with type IV (2) and additional canal forms than that of Sri Lankans. Japanese mandibular second molars exhibited a higher occurrence of one-root canal forms than that of Sri Lankans. In addition, mandibular incisors and canines of Sri Lankans showed a higher prevalence of two canals with type III (1-2-1) canal form than Japanese. Root and canal morphologies of Japanese and Sri Lankan people are consistent with those of people of East Asian and European (western Eurasia) origin, respectively. In human dentition, the differences of the internal canal morphology are more evident and constant than that of external root morphology among different population groups.

Sex determination using mastoid process measurements : standards for Japanese human skeletons of the medieval and early modern periods

Abstract: The purpose of this study was to develop new standards for determining the sex of fragmentary human skeletal remains. We measured height, width, and length of the mastoid process in medieval to early modern Japanese skeletons, from the Yuigahama-minami and Hitotsubashi sites, in order to provide a metric standard for the diagnosis of sex using the mastoid process. We calculated discriminant functions based on these measurements; the accuracy of sex classification was over 80% using a single variable, and reached 82–92% with two variables, mastoid height and width. This accuracy is equal to or better than that reported by some previous studies of sex determination using the cranium. However, when we examined intra- and interobserver errors in the mastoid process measurements, we found a high level of errors, and this highlights the difficulty involved in intraobserver repeatability and interobserver reproducibility. Our results imply that, in order to achieve reliable results of sex determination using the mastoid process, the measurement methods need to be carefully determined and executed.

Morphometric affinity of the late Neolithic human remains from Man Bac, Ninh Binh Province, Vietnam: Key skeletons with which to debate the two layer hypothesis

Abstract: The excavation of the Man Bac site (c. 3800–3500 years BP) in Ninh Binh Province, Northern Vietnam, yielded a large mortuary assemblage. A total of 31 inhumations were recovered during the 2004–2005 excavation. Multivariate comparisons using cranial and dental metrics demonstrated close affinities of the Man Bac people to later early Metal Age Dong Son Vietnamese and early and modern samples from southern China including the Neolithic to Western Han period samples from the Yangtze Basin. In contrast, large morphological gaps were found between the Man Bac people, except for a single individual, and the other earlier prehistoric Vietnamese samples represented by Hoabinhian and early Neolithic Bac Son and Da But cultural contexts. These findings suggest the initial appearance of immigrants in northern Vietnam, who were biologically related to pre- or early historic population stocks in northern or eastern peripheral areas, including Southern China. The Man Bac skeletons support the 'two-layer' hypothesis in discussions pertaining to the population history of Southeast Asia.

Nonmetric cranial variation in human skeletal remains associated with Okhotsk culture

Abstract: Population affinities and biological variation in human skeletal series associated with the Okhotsk culture from Hokkaido and Sakhalin Islands from the 5th to 12th centuries AD are investigated using 19 nonmetric cranial traits. The Okhotsk crania have a higher frequency of the supraorbital foramen than the Hokkaido Ainu and Jomon, while the frequency of the transverse zygomatic suture vestige in the Okhotsk is as high as in the Jomon. The mean measure of divergence between the northern and eastern Okhotsk cranial assemblages is small and insignificant. The method of Relethford and Blangero [Relethford J.H. and Blangero J. (1990) Human Biology, 62: 5–25] suggests that the eastern Okhotsk had a larger Rii value (distance from the centroid) and a lower observed variation than the northern Okhotsk, indicating that the eastern Okhotsk lost phenotypic variability. These results further reaffirm the affinity between the Okhotsk skeletal series and Northeast Asian series such as the Neolithic Baikalian and Amur. Finally, the results of analyses of nonmetric cranial variation demonstrate a close relationship between the Okhotsk, Ainu, and Jomon series that suggests that the Jomon and Ainu were closer to the Okhotsk than to other Northeast Asian series prior to any admixture.

Terminal Pleistocene human skeleton from Hang Cho Cave, northern Vietnam: implications for the biological affinities of Hoabinhian people

Abstract: An excavation at the cave site of Hang Cho in northern Vietnam resulted in the discovery of a terminal Pleistocene human skeleton in a relatively good state of preservation. The material culture from this site belongs to the pre-ceramic Hoabinhian period. An AMS radiocarbon date on a tooth sample extracted from this individual gives a calibrated age of 10450 ± 300 years BP. In discussions of the population history of Southeast Asia, it has been repeatedly advocated that Southeast Asia was occupied by indigenous people akin to present-day Australo-Melanesians prior to the Neolithic expansion of migrants from Northeast Asia into the area. Cranial and dental metric analyses were undertaken in order to assess the biological affinity of early settlers in this region. The results suggest that the Hang Cho skeleton, as well as other early or pre-Holocene remains in Southeast Asia, represent descendants of colonizing populations of late Pleistocene Sundaland, who may share a common ancestry with present-day Australian Aboriginal and Melanesian people.

Variability in stable isotope ratios in two Late-Final Jomon communities in the Tokai coastal region and its relationship with sex and ritual tooth ablation

Abstract: We analyzed stable carbon and nitrogen isotope ratios in a sample of human and nonhuman mammal bones excavated from the Yoshigo and Inariyama shell mounds of the Late-Final Jomon pe- riods in Aichi Prefecture, Japan, with a view to determining individual dietary differences. To inves- tigate possible reasons for the dietary variations identified, we related isotope ratios to sex and tooth ablation patterns. At both sites, large intra-site variations in δ 13 C and δ 15 N values were found, com- pared with other Jomon populations previously studied, suggesting higher than usual levels of dietary variability, and at both sites there was a positive correlation between δ 13 C and δ 15 N values. The diet of the Jomon people at both these sites had two main protein sources: marine (marine finfish and shell- fish) and terrestrial (C3 plants and terrestrial mammals) protein. The intra-site variability is probably explained by consumption of these resources in different proportions. Analysis of the Yoshigo shell mound data indicated that sex is one of the factors determining dietary difference. It was also found that individual differences in diet in Yoshigo males are greater than in females. This pattern was re- peated in the Inariyama shell mound data. Dietary differences were found to be related to ritual tooth ablation characteristics, particularly in males. At Inariyama, type 4I ritual tooth ablation was associated with comparatively greater dependency on terrestrial resources, while type 2C tooth ablation was as- sociated with greater dependency on marine resources. This may indicate that type 4I males engaged predominantly in hunting, and type 2C males in fishing, as a means of food acquisition. These results are possibly the earliest evidence of occupational differentiation in the Jomon people.

Earliest Indonesian facial and dental remains from Sangiran, Java: a description of Sangiran 27

Abstract: Sangiran 27 represents the only facial skeleton of Homo erectus so far known, and is thought to have derived from the earliest Pleistocene sediments of the Sangiran Formation, Java. We here describe in detail this cranial specimen, and provide comparisons with broadly contemporaneous fossils of western Asia and Africa. Sangiran 27 is a highly mineralized partial cranium with a wellpreserved postcanine maxillary dentition, and includes portions of the face and anterior vault that have undergone substantial postmortem crushing and deformation. We consider that the Ar/Ar dates on bracketing tuffs provide an age estimate of between 1.58 and 1.66 Ma for the cranium, making it highly relevant to the identity and adaptations of the earliest hominids dispersing from Africa. Based on anatomical comparisons, Sangiran 27 is best considered a member of H. erectus. However, Sangiran 27 exhibits a more robust morphology than the broadly contemporaneous fossils from Dmanisi, Republic of Georgia and Turkana region, Kenya, while it shares some dental similarities with the Dmanisi 2282 specimen.

Secular trend in body height and weight of Turkish adults

Abstract: The secular change in body size across generations provides information about public health changes and living conditions over time. In this study, secular height and weight changes in the adult Turkish population for the years between 1884 and 2006 were analyzed. The study was based on a contemporary cross-sectional survey conducted in Ankara, Turkey, on 1215 (703 males and 512 females) healthy adults. Historical data sets were obtained from previous surveys. Between 1884 and 2006, the mean height of Turkish males increased by 11.94 cm (0.98 cm/decade). The height increase was 6.59 cm (0.96 cm/decade) for females between 1937 and 2006: the mean weight increase was 15.78 kg for males and 14.12 kg for females during this same 69-year period. Although the mean height of Turkish males was within the range of the variations in European countries during the 1880s, Turkish males and females today are shorter and lighter than people in the United States and several European countries. In the first half of the 20th century, periods of sudden decreases, and subsequent recoveries, were identified. However, in the last three decades the positive secular change has accelerated rapidly due to modest improvements in the socio-economic prosperity of Turkey, and it can be concluded that further positive changes may be expected in the near future.

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

Abstract: 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.

Did the Jomon people have a short lifespan? Evidence from the adult age-at-death estimation based on the auricular surface of the ilium

Abstract: The demography of the Jomon people was first systematically investigated by Kobayashi ([1967] Journal of the Faculty of Science, The University of Tokyo, Section V, 3: 107–162). His lifetable analysis indicated that Jomon life expectancy at the age of 15 was only 16 years. However, recent advances in palaeodemography have questioned whether the reconstruction of demographic parameters from skeletons actually reflects the real mortality patterns of past populations. The purpose of this study is to test the hypothesis that palaeodemographic data from skeletal remains represent an appropriate adult mortality profile. If the hypothesis is the case, the mortality profile of the Jomon people implied the heavy work-load resulting in the unusually high mortality schedule. If it is not the case, on the other hand, Kobayashi’s data had been distorted by the errors of adult age-at-death estimation. This study examined well-preserved auricular surfaces of 86 individuals, which are individuals aged 15 years and above. Age estimation of the auricular surfaces was performed using two techniques: the original method of Lovejoy et al. ([1985] American Journal of Physical Anthropology, 68: 15–28) and the revised method of Buckberry and Chamberlain ([2002] American Journal of Physical Anthropology, 119: 231–239). The results indicate important findings on the mortality profile of the Jomon people. First, the revised estimation has older age distributions, with the majority of individuals over 65 years of age. Second, the revised estimation increases the life expectancy at the age of 15 from 16 years to 32 years. The present data lead to the conclusions that the revised method improves the accuracy of age estimation for elderly adults, and that the Kobayashi’s estimation does not represent the real mortality profile. These findings will have great effects on the life history reconstruction of the Jomon people.

Population history of the northern and central Nansei Islands (Ryukyu island arc) based on dental morphological variations : gene flow from North Kyushu to Nansei Islands

Abstract: This study investigates dental morphological variations among the modern inhabitants of Tanegashima Island and Okinawa Main Island of the Nansei Islands (Ryukyu island arc), which is the southern gateway of the Japanese archipelago. Temporal variations within Tanegashima Island and regional variations of the northern half of the Nansei Islands were used to study population history. The late Aeneolithic Yayoi to protohistoric Kofun populations (c. 0–700 AD) of Tanegashima was found to be similar to the native Japanese populations, such as the Neolithic Jomonese (c. 10000–300 BC) and Hokkaido Ainu; however, the modern population of Tanegashima was similar to the migrant Japanese populations such as the post-Jomon people (c. 300 BC–present time) of the Japanese main islands. Using statistically sufficient materials, this study confirmed that a substantial change had occurred from the prehistoric to the modern period in Tanegashima Island. It is suggested that temporal change occurred in Tanegashima over approximately 1000 years after substantial change (c. 300 BC) in the Japanese main islands. The delay in temporal change in Tanegashima indicates that dispersal of migrant populations from northern Kyushu to its southern end occurred at a time remarkably later than the northeastward dispersal of migrant populations to central Honshu Island. Furthermore, the geographical cline extending from North Kyushu to Okinawa Main Island via Tanegashima Island suggests southward gene flow from North Kyushu to the central Nansei Islands via the northeast end of the Nansei Islands.

Pathology of deciduous teeth in the samurai and commoner children of early modern Japan

Abstract: The strict class system in place during the Edo (early modern) period in Japan is thought to have encompassed customs that differed between the samurai (ruling class) and commoners. This study found that in samurai children, deciduous caries occurred only in maxillary incisors at 0.5–2 years of age and did not occur in the mandibular incisors and canines at 3–5 years of age. Conversely, in commoner children, deciduous caries occurred in all maxillary teeth and mandibular molars at 0.5–2 years of age and in all maxillary and mandibular teeth at 3–5 years of age. In commoner children, deciduous caries was seen in tooth types that have a low incidence of deciduous caries in modern Japanese. The present results show that deciduous carious lesions appear earlier and more frequently in the commoner children compared to the samurai children, probably because of differences in lifestyle between the two groups. There was no significant difference in the incidence of enamel hypoplasia in the deciduous dentition between samurai and commoner children, suggesting that the two classes had broadly comparable nutrition. In our previous study using the same skeletal series, similar results between samurai and commoners were found with respect to caries and enamel hypoplasia prevalence of the permanent dentition. Many of the samurai adults had slick polished teeth, which we believe were caused by regular brushing of the teeth in the samurai class. Such a custom might have functioned to prevent dental caries not only in the permanent dentition, but also in the deciduous dentition. Thus, oral hygiene practices in the samurai class are thought to have functioned to prevent dental caries not only in adults but also in children.

Kiik-Koba 2 and Neandertal axillary border ontogeny

Abstract: The significance of morphological variation in the axillary border among Pleistocene and recent humans has been considered for nearly a century, with the high frequency of the dorsal sulcus pattern in the Neandertal lineage receiving particular attention. Although usually considered an epigenetic trait, or phylogenetic marker, the variation has also been related to functional demands on the shoulder region. The Kiik-Koba 2 infant Neandertal scapula, as one of the developmentally youngest ones known, exhibits a smooth ventral surface, a ventral displacement of the lateral margin, a prominent dorsal bar, and a dorsolateral sulcus along the border. This configuration is best seen as an incipient dorsal sulcus pattern, and given the young age-at-death of Kiik-Koba 2, supports the epigenetic trait interpretation of the morphological variation.

Dental diseases of human skeletal remains from the early-modern period of Kumejima Island, Okinawa, Japan

Abstract: Human skeletal remains from the early-modern period (17th-19th centuries AD) of Kumejima Island, the Ryukyu Islands, were examined for dental disease, including dental caries, linear enamel hypoplasia (LEH), antemortem tooth loss (AMTL), and dental calculus. The materials used in this study consisted of 386 adult individuals, 105 male, 89 female, and 192 of unknown sex. The high- est rate of dental caries occurred in the adult females. Female physiological events, such as pregnancy and menopause, as well as differences in food preference may have led to this sex difference, as suggest- ed by isotopic analysis. The high incidence of AMTL in the older females indicate that the actual rate of dental caries must have been even higher. There were no significant differences in the rate of dental caries between prehistoric foraging and early-modern farming Ryukyu Islanders, probably because of similar dietary composition of C3 plant and fish. Adult females tended to be more affected by LEH, indicating that they experienced greater physiological stress during early childhood.

Frequency of mandibular tori in the present-day Japanese

Abstract: The frequency and morphology of mandibular tori and the correlations between their development and environmental factors (number of teeth, degree of crowding, degree of dental attrition) were examined in plaster casts of present-day Japanese dental patients and students. A total of 224 patients (118 males aged 13–77, average age 50; 106 females aged 15–81, average age 49) and 113 students (60 males aged 17–36, average age 20; 53 females aged 18–29, average age 19) were included in the examinations. Before the examinations, we defined a new torus grading system with four categories. There were no statistically significant differences between males and females and between the left and right sides in the distribution of torus classes and positions. Palpable tori were found in 76.6% of patients and 72.0% of students. Perceptible tori were found in 70.3% of patients and 58.0% of students. Tori were most frequently found below the first and second premolars. In students, the torus class and size negatively correlated with the degree of crowding and positively correlated with the degree of dental attrition. In patients, torus class and size positively correlated with the degree of dental attrition, the number of teeth, and age. From these results, we suggest that mandibular tori are promoted by masticatory stress and other factors correlated with age.

Extremely high fertility of a sedentarized Bedouin clan in south Jordan: a genealogical-demographic approach to long-term change

Abstract: A Bedouin-origin clan with extremely high fertility in south Jordan sedentarized in a village in 1948. In this paper, based on our genealogical-demographic data collected from this clan, we elucidate the long-term demographic change that this clan has undergone. Our results highlight differences in fertility indicators among the early (1950–1969), middle (1970–1989), and late (1990–2004) periods. In particular, the total marital fertility rate (TMFR) was 4.756, 9.852, and 9.146, respectively, and the total fertility rate (TFR) was 3.589, 7.214, and 5.189, respectively. Taking age-specific indicators into account, the increase in TFR or TMFR from the early to the middle periods was attributable to increased rates of childbirth among middle-aged and older women, presumably associated with improvements in maternal nutrition and increased demand for children as agriculture labor, while the decrease in TFR from the middle to the late periods was caused by a delay in females’ age at marriage and an increase in the number of unmarried females. The fertility of this clan has been high, especially in the late period, and it is estimated that its population will double by 2030, implying the urgent necessity to reduce fertility to prevent overpopulation that threatens the people’s subsistence adaptation.

Severe developmental defects of enamel in a human skeleton of the Final Jomon age from the Nakazawahama shell-mound, Iwate, Japan

Abstract: In an adult human skeleton of the Final Jomon age excavated at the Nakazawahama shell-mound in Iwate Prefecture, northeastern Japan, grooved enamel defects (about 2 mm in width) were observed circumferentially around the dental crowns of the upper left central incisor, upper right lateral incisor, and upper right canine. Observations of the crown surface using a stereomicroscope and evaluations of soft X-ray images revealed severe developmental defects of enamel (DDEs), having the characteristics of both enamel hypoplasia and enamel hypocalcification caused by systemic metabolic stresses. We estimated that these defects were formed at the age of late 1 year. This is the first report on such severe enamel defects in a Jomon skeleton.

Growth of height and leg length of children in Beijing and Xilinhot, China

Abstract: A number of papers on the growth of Chinese children have been published in local journals in China in the Chinese language. However, we noticed that height and weight are the main focus of these studies. Because leg length relative to height is of interest in human biology, the current study focuses on the growth of this proportion. Two groups of Chinese children were investigated: 587 boys and 625 girls in Beijing in 1997 aged 6-18 years, and 579 boys and 615 girls in Xilinhot, Inner Mongolia, in 2005 aged 7-18 years. Height and leg length (iliospinal height) were measured, and the ratio of leg length to height was calculated for each child. Mean distance curves and spline-smoothed yearly increment curves were obtained. In order to clarify the difference between the two groups of Chinese children, data from Japanese children were adopted as a control. The Beijing children were taller than the Xilinhot children, but no difference was detected in leg length between them. The ages at 'take-off and 'peak' obtained on the yearly increment spline-smoothed curve of height in the Xilinhot children boys were 1.2-1.8 years earlier, respectively, than those of the Beijing boys. In the girls, these two ages were almost the same in the two cities, although the 'peak' was 1.8 cm greater in the Xilinhot girls. Leg length in the boys was almost the same in both Beijing and Xilinhot. In the girls of the Xilinhot group, leg length was greater after puberty. Consequently, the ratio of leg length to height was greater in the Xilinhot children than the Beijing children. It is suggested, in China, that socioeconomic factors influence growth of height to a greater extent than growth of leg length, and that leg length and leg length relative to height might be controlled by a genetic factor.

A computer simulation study on the causal relationship between walking and physical malfunctions in older adults

Abstract: The purpose of the present study was to investigate the causal relationship between walking pattern and physical malfunction using a computer simulation method with a biomechanical walking model. In this computer simulation, the musculoskeletal system was represented by a three-dimensional 14-rigid-link model and 60 muscle models. Muscular forces were controlled by a neuronal system model consisting of 16 pairs of neural oscillators. In the computational experiment, five types of walking models were constructed: an intact model, a delayed response model, a weak muscle model, an inclined posture model, and a joint contracture model. These malfunction factors were hypothesized to have a causal relationship with walking characteristics in older adults. The simulation revealed that the delayed response in the neuronal system was primarily related to walking stability. In addition, the weakening of muscles was strongly related to the reduction of the walking step length. The inclined posture and joint contracture also influenced the walking pattern, but not significantly. The use of such a computer simulation method is essential in order to clarify the causal relationship between body function and walking pattern in older adults.

Possible steatopygia in prehistoric central Japan : evidence from clay figurines

Abstract: It is proposed that the so-called ‘protruding buttock’ figurines from Middle Jomon central Japan may be representations of steatopygia. The distribution of these figurines is associated with archaeological evidence for high population densities and possible intensive use of wild yams (Dioscorea japonica). Given the low fat content of these yams, it is suggested that nutritional stress in the diet of Middle Jomon hunter-gatherers of the Chubu highlands may be consistent with the fat accumulation on the buttocks apparently represented in the ‘protruding buttock’ figurines.

The Pacific lineage (2E) of JC polyomavirus is prevalent in Sumba Island, Eastern Indonesia

Abstract: Recent studies have identified a Pacific lineage (2E) of JC polyomavirus (also designated as JC virus or JCV) that occurs in both Island Southeast Asia and Oceania, but not in mainland Asia. It has been postulated that this lineage traveled with Austronesian-speaking people who are now spread throughout Island Southeast Asia and Oceania (excluding Australia and inland and southern New Guinea). However, to date, the 2E lineage has been identified in Southeast Asia only in populations of the Philippine islands. Here we report that a high incidence of the 2E lineage was detected in the people of Sumba Island, eastern Indonesia.