A quantitative investigation of irregular cuspules in human maxillary permanent molars

The frequency of occurrence of anomalous cusps or tubercles on human upper first molars was investigated in seven racial populations using moiré contourography, which permits the three-dimensional measurement of minute cusps. Tubercles on the mesial marginal ridge were more frequently found in Mongoloid populations (Japanese and Eskimo) than in others. The frequency of the protoconule was high in Eskimos and Negroids (Bantu and San). The lingual paracone tubercle (mesial cusp) showed a particularly high frequency in Australian aborigines. The metaconule was rare or absent in all of the populations. Caucasoid groups (Dutch White and Asiatic Indian) showed generally low frequencies of all these abnormal tubercles, especially the distal accessory cusp (C5). Racial differences in the frequencies of occurrence may offer a key to understanding the adaptive significance of these traits and human microevolution. Confusion in nomenclature for upper molar tubercles is also discussed.     

Chimpanzees as an outgroup for the examination of human dental evolution

In the assessment of human origins, chimpanzees (Pan troglodytes, henceforth called Pan) represent the best hominoid outgroup for comparisons. Such an outgroup roots the "anatomically modern" human population cluster, or continuum. This study incorporates chimpanzees into a worldwide modern human database of quantified complete tooth variables (approximately 30 per tooth; e.g., root, pulp, enamel) in an attempt to develop a more accurate phylogeny of the hominoid continuum, with only intervening extinct hominids missing. Canonical discriminate analysis was performed mainly among Liberian common chimpanzees and global samples of humans. The first canonical variable explained 70% of the total variance and showed a tight cluster of humans, with chimpanzees as a distant outgroup. Within the human community, first non-San Bushman, sub-Saharan Africans and Andamanese, and then, close in, Australian aborigines were positioned towards Pan. Their relative orientation suggested an African human origin with the first branch within sub-Saharan Africa: sub-Saharan Africans and San Bushmen. Next, Andamanese Negritos, and then Australian aborigines, formed the early first surviving modern human lineage to leave Africa. Thin enamel and big teeth with relatively large roots characterized Pan nonmolar teeth. Humans showed a generalized sexual dimorphism for all teeth, with males having bigger teeth, bigger relative roots, and thinner enamel than females, while only Pan canines had significant and impressive sexual dimorphism. Interestingly, Pan molars were not larger than human molars. The data suggest that although hominids underwent two dental macroevolutionary events, the lineage leading to modern humans only experienced anterior tooth-size reduction. The suggested evolutionary significance of the observed total tooth variation is discussed.     

Relationships between age and dental attrition in Australian aboriginals

Tooth wear scores (ratios of exposed dentin to total crown area) were calculated from dental casts of Australian Aboriginal subjects of known age from three populations. Linear regression equations relating attrition scores to age were derived. The slope of the regression line reflects the rate of tooth wear, and the intercept is related to the timing of first exposure of dentin. Differences in morphology between anterior and posterior teeth are reflected in a linear relationship between attrition scores and age for anterior teeth but a logarithmic relationship for posterior teeth. Correlations between age and attrition range from less than 0.40 for third molars (where differences in the eruption and occlusion of the teeth resulted in different patterns of wear) to greater than 0.80 for the premolars and first molars. Because of the generally high correlations between age and attrition, it is possible to estimate age from the extent of tooth wear with confidence limits of the order of +/- 10 years.     

Australian aborigines represent the first branch from Eurasian antecedents: odontometric evidence

Most genetic data suggest that Australian aborigines and Southeast Asians associate, but their relative evolutionary relationship has remained obscure. Historically, the study of tooth crown variables has been important in establishing phylogenetic relationships. Through the quantification of whole tooth structure (GDP), including root, pulp, and enamel, a likely Eurasian phylogeny emerged from a canonical discriminant analysis of the microevolution among the populations. The analysis suggested that in modern human evolutionary history, Australian aborigines are the best representative extant population (first branch) from an unknown antecedent Eurasian founder population. The next branch from the Asian-based antecedent population was Caucasoids. Within the resident antecedent East Asian population, Southeast Asians then evolved, followed by a branch that lead to antecedent east Central Asians. Mongolians and all Native Americans independently evolved from this antecedent east Central Asian population. The relatively short morphogenetic separation between two areas that have been isolated for great periods of time, i.e., Australian aborigines and Native Americans, suggests that their association is not due to gene flow.     

Is the complexity of the human sagittal suture related to the size of the temporal muscle?

We have tested the hypothesis that temporal muscle size determines the degree of interdigitation of the human sagittal suture by comparing male and female skulls of Europeans and Australian aborigines. Temporal muscle length, area of the temporal aperture and estimated muscle volume were greater in males than in females of each racial group. Sexual dimorphism of the complexity of the sagittal suture was not confirmed in either race. However, the suture was less complex in aborigines than Europeans despite the volume of the temporal muscle being larger in the former group. We conclude, therefore, that although the morphology of the sagittal suture is an epigenetic character, it is not mechanically influenced by muscle size. A simple quantitation of suture form may however be useful in assigning unknown skulls to a particular race.     

Malocclusion in the Kwaio, a Melanesian group on Malaita, Solomon Islands

In the present investigation, a number of occlusal variables which contribute to malocclusion were quantified among the Kwaio people of Malaita, Solomon Islands. Angle classification, overjet, overbite, openbite, crossbite, rotation, crowding, and spacing were assessed from dental casts of 180 persons (94 males, 86 females) who had complete permanent dentitions anterior to the first molar. Males had significantly more overjet and mandibular incisor crowding than females, and significantly less posterior openbite and mandibular canine-premolar spacing. The frequency of openbite, rotation of maxillary teeth, and crowding of anterior teeth increased with advancing age. The frequency of posterior crowding decreased after age 30. Spacing, in general, increased with advancing age. In the distribution of the Angle classes of occlusion, the Kwaio resembled Australian aborigines living in technologically primitive circumstances.     

Dental wear in the Libben population: Its functional pattern and role in the determination of adult skeletal age at death

Modal patterns of occlusal attrition are presented for the Libben population based on a sample of 332 adult dentitions. Maxillas and mandibles were reviewed independently by seriation prior to assessment of complete dentitions. The Spearman rank order coefficient for upper and lower dentitions was.96. Wear patterns are very similar to those reported by Murphy (1959a: Am. J. Phys. Anthropol. 17:167–178) for Australian aborigines. There were no significant sexual differences in wear rate. Dental wear is concluded to be a highly reliable and important indicator of adult age at death for skeletal populations if seriation procedures are employed.     

Coronal breadth of human primary anterior teeth

Original data for mesiodistal diameter of deciduous anterior teeth on 180 White children show: (1) mean size is smallest for the lower central incisor and largest for the upper canine, (2) means from combining widths on the left anterior teeth of each arch are larger in the maxilla than the mandible by 4.0 mm, (3) individual differences for widths of the upper central and lateral incisors extend from one child with these teeth of similar size to another child with the central incisor larger than the lateral by 2.3 mm, and (4) anterior tooth correlations are positive, varying from r = 0.4 for upper canine width with width of lower central incisor, to r = 0.8 for combined widths of left anterior teeth in the maxilla with combined widths of their antagonists. Comparative findings are drawn from investigations on Australian aborigines, South African Bushmen, Liberian Negroes, Tristan da Cunha islanders, Japanese, Japanese-Negro admixtures, Japanese-White admixtures, White groups living in several parts of Europe, and North American Whites. Among these ethnic groups, Australian aborigines have the largest deciduous anterior teeth. Composite means on each sex for North American Whites show boys to have slightly larger anterior deciduous teeth than girls.     

Variation in enamel development of South African fossil hominids

Dental tissues provide important insights into aspects of hominid palaeobiology that are otherwise difficult to obtain from studies of the bony skeleton. Tooth enamel is formed by ameloblasts, which demonstrate daily secretory rhythms developing tissue-specific structures known as cross striations, and longer period markings called striae of Retzius. These enamel features were studied in the molars of two well known South African hominid species, Australopithecus africanus and Paranthropus robustus. Using newly developed portable confocal microscopy, we have obtained cross striation periodicities (number of cross striations between adjacent striae) for the largest sample of hominid teeth reported to date. These data indicate a mean periodicity of seven days in these small-bodied hominids. Important differences were observed in the inferred mechanisms of enamel development between these taxa. Ameloblasts maintain high rates of differentiation throughout cervical enamel development in P. robustus but not in A. africanus. In our sample, there were fewer lateral striae of Retzius in P. robustus than in A. africanus. In a molar of P. robustus, lateral enamel formed in a much shorter time than cuspal enamel, and the opposite was observed in two molars of A. africanus. In spite of the greater occlusal area and enamel thickness of the molars of both fossil species compared with modern humans, the total crown formation time of these three fossil molars was shorter than the corresponding tooth type in modern humans. Our results provide support for previous conclusions that molar crown formation time was short in Plio-Pleistocene hominids, and strongly suggest the presence of different mechanisms of amelogenesis, and thus tooth development, in these taxa.     

Studies on agenesis in the permanent dentition

Tooth dimensions in 104 males and females with agenesis of one or more permanent teeth, other than third molars, have been examined. The amounts of size reduction from normal in mesiodistal and buccolingual tooth diameters appear to be independent. Also some apparent differences from normal tooth size variability were noted. Interestingly, first molars and canines, both considered to be stable components of the dentition, showed significant variability in tooth size. In addition the incidence of individual tooth agenesis within this sample was noted and maxillary lateral incisor was most frequently absent in both sexes.     

Alpha-globin gene markers identify genetic differences between Australian aborigines and Melanesians.

Australian aborigines exhibit a number of alpha-globin cluster rearrangements involving both alpha- and zeta-globin genes. alpha+-Thalassemia (-alpha/) in this population is heterogeneous and includes the 3.7 types I, II, and III gene deletions. The alpha alpha alpha/ and zeta zeta zeta/ rearrangements are each found in association with two haplotypes, indicating origins from at least two separate DNA crossover events. Differences in alpha-globin cluster rearrangements and in haplotypes between Australian aborigines, Papua New Guinea highlanders and island Melanesians, are consistent with multiple colonizing events into Australia.     

军都山古代人群牙齿磨耗及其饮食

以军都山墓地为代表的"玉皇庙文化"系中国北方青铜时代的一支具有鲜明地方特色的少数部族文化。本文对军都山墓地出土人骨牙齿标本作牙齿磨耗状况分析,试图为其饮食结构和社会经济形态的探讨提供线索。结果显示:军都山古代人群中,相同年龄组的男女两性牙齿磨耗差异不大;前部牙齿磨耗轻于后部臼齿,第一臼齿磨耗最重;臼齿磨耗样式大多呈现"正常平匀"式,臼齿磨耗角度大多较小,两者均随年龄而变化但没有显著的性别差异。经与其他样本组的对比认为军都山古代人群牙齿磨耗的特点可能与其社会经济农牧兼营的性质有关,推测动物性食物(肉食)可能在军都山古代人群主要饮食结构中占据重要比例,并包含有一定的农业经济成分。不同游牧人群牙齿磨耗程度差异较大,只有结合了磨耗形态及其他信息才有可能更切实地反映其饮食状况。     

Dentition of a mesolithic population from Wadi Halfa, Sudan

The dentition of a Mesolithic population (8,000–11,000 years old) from Wadi Halfa, Sudan, can be characterized as morphologically complex, massive and relatively free from pathology except that associated with extreme wear. Maxillary incisors show shoveling. All of the maxillary molars show some development of the hypocone. Supernumerary cusps appear frequently. Almost one-half of the second lower molars observed show distally located third cusps. Over one-half of the maxillary third molars show an extra cusp. A high percentage of mandibular molars show six cusps. Overall the teeth from this population compare favorably in size with those of an Australian aborigine tribe and are slightly larger than the teeth of the Neanderthaloids from Skūhl. The teeth show wear of a degree greater than that found in present day Eskimo or Australian aborigine groups. This data may be interpreted as indicating that this Mesolithic group was subjected to rigorous selective pressures favoring large and/or morphologically complex teeth. This pressure was apparently intensive wear, presumably caused by the inclusion of large amounts of grit in the diet through the eating of vegetable food macerated on coarse grinding stones.     

The Aymara of Western Bolivia. II. Maxillofacial and dental arch variation

Maxillofacial and dental arch dimensions of the Bolivian Aymara population are age and sex dependent. Interpopulational comparisons reveal these dimensions to differ from those seen in Aleuts, Australian aborigines, and Swedes, but to be similar to those of the indigenous Taiwanese. Finally, these dimensions are not the same in Aymara of unmixed ancestry, and Mestizos residing in the same villages.     

Albumin — vitamin D-binding protein haplotypes in Asian-Pacific populations

Summary We have determined the various haplotypic combinations between alleles as well as restriction fragment length polymorphisms of two linked genetic markers, albumin and vitamin D-binding protein or group-specific component, in a number of Asian-Pacific populations. Using the partial maximum likelihood method, we constructed a phylogenetic network from the haplotype frequencies to assess relationships among the populations sampled. No systematic linkage disequilibrium was detected between most of the combinations, suggesting a lack of operation of any selection pressure at the two loci. The phylogenetic analysis confirmed the known interrelationships among various populations in the Asian-Pacific region. The Australian aborigines clustered closely with the non-Austronesian-speaking highlanders from Papua New Guinea, as expected. Similarly, the Austronesian-speaking Polynesians, Micronesians, and the Southeast Asians branched off together as a separate group. The position of the Austronesian-speaking Tolais from New Britain with respect to other populations from the Southwest Pacific was anomalous. The Tolais revealed a strong affinity with the Australian aborigines, which is inexplicable. The populations from China formed a tight cluster with other populations from the Asian-Pacific region. Genetic interrelationships of these populations with the white Australians were remote, which is in accordance with the known affinities of various human racial groups.     

Genetic variation in mitochondrial DNA from some aboriginal Australians

Mitochondrial (mt) DNAs from 17 aboriginal Australians, predominantly from the coastal region of the Northern Territory were isolated and digested with four four-base restriction endonucleases, two of which revealed variation between samples. The observed fragment patterns were used directly in parsimony analyses of phylogenetic relationships between the samples, and were also converted to estimates of the number of substitutions per nucleotide position between samples (delta), which estimates were then used in distance analyses of phylogeny. The inferred fragment patterns of the completely sequenced 'Cambridge' human mtDNA were also included in these analyses. No strong evidence of geographic variation was found, consistent with previous findings of Australian aborigines and other humans generally, although the most divergent sample was one of two from Sydney, indicating that further work is desirable. The estimate of mean difference between samples (diversity), 0.0017 +/- 0.0003 (mean +/- 95% confidence interval), is significantly lower than that reported previously for humans generally.     

Distinct Modes of Transmission of Tuberculosis in Aboriginal and Non-Aboriginal Populations in Taiwan

Tuberculosis incidence among aborigines is significantly higher than for Han Chinese in Taiwan, but the extent to which Mycobacterium tuberculosis (MTB) strain characteristics contribute to this difference is not well understood. MTB isolates from aborigines and Han Chinese living in eastern and southern Taiwan, the major regions of aborigines, were analyzed by spoligotyping and 24-loci MIRU-VNTR. In eastern Taiwan, 60% of aboriginal patients were ≤20 years old, significantly younger than the non-aboriginal patients there; aborigines were more likely to have clustered MTB isolates than Han Chinese (odds ratio (OR) = 5.98, p<0.0001). MTB lineages with high clustering were EAI (54.9%) among southern people, and Beijing (62.5%) and Haarlem (52.9%) among eastern aborigines. Resistance to first-line drugs and multidrug resistance (MDR) were significantly higher among eastern aborigines (≥15%) than in any other geographic and ethnic group (p<0.05); MDR was detected in 5 of 28 eastern aboriginal patients ≤20 years old. Among patients from the eastern region, clustered strains (p = 0.01) and aboriginal ethnicity (p = 0.04) were independent risk factors for MDR. The lifestyles of aborigines in eastern Taiwan may explain why the percentage of infected aborigines is much higher than for their Han Chinese counterparts. The significantly higher percentage of the MDR-MTB strains in the aboriginal population warrants close attention to control policy and vaccination strategy.     

Molar size sequence in Australian Aboriginals

Percentage frequencies for molar size sequence of first and second molars were calculated in a group of contemporary Australian Aboriginals using mesiodistal and buccolingual dimensions, as well as crown areas. Comparisons were made between sexes, arches, and dimensions within the Aboriginal groups and also between Aboriginal data and those published for other populations. The frequencies of the M2 > M1 molar size sequence in the Aboriginals fell within the range of frequencies reported for other contemporary populations. Differences in the frequencies of the M2 > M1 sequence between the sexes and between arches, together with the relatively high frequency of asymmetry in molar size sequence within Aboriginals, supported the notion that local environmental conditions acting during odontogenesis, together with differential responses to other environmental influences, play an important role in determining observed patterns of molar tooth size.     

Measurements of tooth wear among Australian aborigines: II. Intrapopulational variation in patterns of dental attrition

The possible implications of variations in dental attrition patterns have necessitated a detailed assessment of the types, ranges, and causes of tooth wear. Hear we employ measurements of postcanine occlusal wear facets from a sample population of extant Australian aborigines. A principal components analysis was applied as a tool in determining common types of attritional patterns. It was concluded that the range of intrapopulational variation in dental wear patterns must be attributed to a multiplicity of sources in addition to such commonly cited causes as dietary variations, gender, age, and developmental eruption sequences.     

Paternal genetic structure of Hainan aborigines isolated at the entrance to East Asia

Background

At the southern entrance to East Asia, early population migration has affected most of the Y-chromosome variations of East Asians.

Methodology/Principal Findings

To assess the isolated genetic structure of Hainan Island and the original genetic structure at the southern entrance, we studied the Y chromosome diversity of 405 Hainan Island aborigines from all the six populations, who have little influence of the recent mainland population relocations and admixtures. Here we report that haplogroups O1a* and O2a* are dominant among Hainan aborigines. In addition, the frequency of the mainland dominant haplogroup O3 is quite low among these aborigines, indicating that they have lived rather isolated. Clustering analyses suggests that the Hainan aborigines have been segregated since about 20 thousand years ago, after two dominant haplogroups entered East Asia (31 to 36 thousand years ago).

Conclusions/Significance

Our results suggest that Hainan aborigines have been isolated at the entrance to East Asia for about 20 thousand years, whose distinctive genetic characteristics could be used as important controls in many population genetic studies.