Major features of Sundadonty and Sinodonty, including suggestions about East Asian microevolution, population history, and late Pleistocene relationships with Australian aboriginals

The eight diagnostic morphological traits of the Sundadont and Sinodont divisions of the Mongoloid dental complex are identified. Intra- and intergroup variation for these crown and root features is plotted. The univariate frequency distributions provide useful evidence for several suggestions about East Asian prehistory, dental microevolution, and intergroup relationships. The case for local evolution of Sundadonty is strengthened by finding Australian teeth to be very similar to this pattern. Australian Aboriginal teeth are also generally like those of Jomonese and some Ainus, suggesting that members of the late Pleistocene Sundaland population could have initially colonized Sahulland as well as the continental shelf of East Asia northward to Hokkaido.     

长阳青铜时代与大同北魏朝代人类牙齿的形态变异

本文记述了湖北长阳县深潭湾青铜时代和山西大同市郊北魏朝代两处墓葬遗址出土的人类牙齿形态变异的状况,提供人们对牙齿形态种种变异的认识,探索非测量性牙齿特征在研究种族和人群之间关系中的意义。     

Metric analyses of an Early Holocene human skeleton from Gua Gunung Runtuh,Malaysia

A nearly complete human skeleton dating to the Early Holocene (epi-Paleolithic culture) excavated from Gua Gunung Runtuh, Malaysia, is described. Cranial, dental, and limb bone measurements are recorded on the skeleton, and compared with early and modern skeletal samples from Southeast Asia and Australia. The comparisons demonstrate that the Gua Gunung specimen is most similar to Australian Aborigines in dental and limb measurements, while the cranial measurements indicate a close affinity to Mesolithic samples from Malaysia and Flores. These findings further suggest that the Gua Gunung skeleton, as well as other fossils from Tabon and Niah, are representative of an early group of people who occupied Sundaland during the late Pleistocene, and may be the ancestors of Australian Aborigines. Some of the dental and limb bone measurements exhibited by the ancestors persist in Southeast Asian populations until the early Holocene. Differences in cranial traits have, however, accumulated since the late Pleistocene in Australian Aborigines and early Southeast Asian peoples. Am J Phys Anthropol 109:327–340, 1999. © 1999 Wiley-Liss, Inc.     

Prehistoric "fish-eaters" along the eastern Arabian coasts: dental variation, morphology, and oral health in the Ra's al-Hamra community (Qurum, sultanate of Oman, 5th-4th millennia BC)

The Ra's al-Hamra prehistoric fishermen lived in isolation on the Qurum rocky promontorium in Oman during the 5th-4th millennia BC. To date, they represent the most ancient and numerous human fossil group excavated from the Arabian peninsula. Like other contemporaneous archaeologically documented small communities along the desert Arabian coasts, they intensively exploited ocean resources and collected molluscs from nearby mangrove swamps. The present study analyzes aspects of dental anthropology (including crown variation, morphology, dental wear, and oral health), in 600 permanent teeth from 49 individuals of both sexes excavated at the Mesolithic RH5-site by the Italian Archaeological Mission in Oman from 1981 to 1985. In association with a general low degree of morphometric variation, the Ra's al-Hamra dental crowns show low sexual dimorphism and are consistently reduced in size. These features are unexpected in a preagricultural population, especially when these data are compared to other eastern African and near Middle Eastern prehistoric populations. These data are discussed within the general context of human dental structural reduction occurring during the post-Pleistocene and are interpreted according to the "increasing population density effect" model. There are other significant differences that characterize the Ra's al-Hamra dentitions with respect to both eastern and western prehistoric human groups. The frequency of numerous nonmetric crown traits supports the hypothesis that a microdifferentiation phenomenon occurred in this marginal area. The preliminary skeletal analysis and the palaeodemographic profile show that the Omani prehistoric fishermen were affected by genetic isolation and inbreeding as well as strong environmental stress. Because of the grit assimilated with dried fish and the high shellfish consumption, dental wear was extreme in all age groups at Ra's al-Hamra and occasionally was responsible for serious hematogenously spread infections. In spite of the great anthropological importance of ancient Arabian populations, very few studies on skeletal and dental samples have been completed. The present paper offers an odontological data set for future comparative research in the area.     

Characteristic high- and low-frequency dental traits in sub-Saharan African populations

In an earlier investigation (Irish [1993] Biological Affinities of Late Pleistocene Through Modern African Aboriginal Populations: The Dental Evidence [Ann Arbor: University Microfilms]), biological affinities of 32 sub-Saharan and North African dental samples were estimated using comparative analyses of 36 dental morphological traits. Marked dental homogeneity was revealed among samples within each of the two geographic regions, but significant interregional differences were noted. Assuming dental phenetic expression approximates or is an estimate of genetic variation, the present study of 976 sub-Saharan-affiliated Africans indicates they are not closely related to other world groups; they are characterized by numerous morphologically complex crown and root traits. Turner ([1984] Acta Anthropogenetica 8:23–78; [1985] in R Kirk and E Szathmary (eds.): Out of Asia: Peopling the Americas and the Pacific [Canberra: The Journal of Pacific History], pp. 31–78; [1990] Am. J. Phys. Anthropol. 82:295–318; [1992] Persp. Hum. Biol. 2/Archaeol. Oceania 27:120–127; [1992] in T Akaszawa, K Aoki, and T Kimura (eds.): The Evolution and Dispersal of Modern Humans in Asia [Tokyo: Hokusen-Sha Publishing Co.], pp. 415–438) reports that Northeast Asian/New World sinodonts also have complex teeth relative to Europeans, Southeast Asian sundadonts, Australian/Tasmanians, and Melanesians. However, sinodonty is characterized by UI1 winging, UI1 shoveling, UI1 double shoveling, one-rooted UP1, UM1 enamel extension, M3 agenesis, and three-rooted LM1. Sub-Saharan peoples exhibit very low frequencies of these features. It is proposed that the collection of dental traits which best differentiate sub-Saharan Africans from other worldwide samples includes high frequencies of the Bushman Canine, two-rooted UP1, UM1 Carabelli's trait, three-rooted UM2, LM2 Y-groove pattern, LM1 cusp 7, LP1 Tome's root, two-rooted LM2, UM3 presence, and very low incidences of UI1 double shoveling and UM1 enamel extension. This suite of diagnostic traits is termed the sub-Saharan African dental complex. Am J Phys Anthropol 102:455–467, 1997. © 1997 Wiley-Liss, Inc.     

Gaining New Insights into How Genetic Factors Influence Human Dental Development by Studying Twins

Many previous attempts to quantify the contribution of genetic factors to human dental variation using the classical twin design have been based on untested assumptions that lead to unreliable estimates of heritability. We have applied structural equation modelling to several different dental phenotypes in a sample of over 600 pairs of Australian twins, enabling the goodness-of-fit of the data to be tested against genetic models incorporating different components of genetic and environmental variance. Our results indicate that the contribution of additive genetic effects to phenotypic variation differs considerably between different dental traits. Heritability estimates for intercuspal distances of molar teeth and for incisal overbite and overjet are low to moderate in magnitude, whereas heritabilities for overall molar crown size and arch dimensions are moderate to high. We propose that after formation of the enamel knots during odontogenesis, the emerging pattern of molar cusps results from a cascade of local epigenetic events, rather than being under direct genetic control. Variation in molar crown size is explained best by a model incorporating additive genetic effects, as well as environmental influences that are both unique and common to co-twins. These environmental influences presumably operate in utero during the early stages of molar odontogenesis prior to crown calcification. The relatively low heritabilities noted for occlusal traits are consistent with the importance of masticatory activity and muscle function in determining the interrelationships between teeth in opposing dental arches. We believe that well-designed studies of twins, coupled with modern genome-scanning approaches, offer great potential to identify key “dental” genes and to clarify how these genes interact with the environment during development.     

Hunter-Schreger band orientation in interproximal enamel of modern human molars with complex morphological traits

A recent paper concerning characteristic groove-shaped wear in interproximal attritional facets of Neandertal posterior teeth correlated groove formation with deep enamel structural traits (Villa & Giacobini, 1995). Further studies were carried out on modern human teeth in order to evaluate a possible correlation between deep enamel structure and some crown complex morphological features. Seventy-five isolated molars from medieval and recent ossuaries as well as five molars recently extracted for therapeutic purpose were examined using scanning electron and optic microscope ground sections of interproximal enamel. The results showed possible correlations between deep enamel structural characteristics (i.e., Hunter-Schreger band verticalization) and some crown complex traits (i.e., occlusal groove pattern, mesial and distalfovea, mesial and distal accessory tubercules, interproximal marginal ridges). Observations reported in this study showed a significantly higher frequency of Hunter-Schreger band verticalization in lower molars with an occlusal complex pattern (i.e. primitive fissure pattern “Y” or “+”). This observation suggests a positive correlation among crown complex traits (which occur frequently in Neandertal teeth) with deep enamel structural characteristics. In addition, analysis of teeth grouped according to individual showed crown morphological traits and deep enamel structural characteristics corresponding to the same individual. This observation supports a genetic basis in occlusal shape and microstructural dental traits.     

Dental morphology of the early Hoabinian, the Neolithic Da But and the Metal age Dong Son civilized peoples in Vietnam

The early Hoabinian, the Neolithic Da But and the Dong Son (early Metal age) civilized peoples in northern Vietnam were investigated based on dental morphology and were compared with specimens from surrounding Northeast and Southeast Asia including Australians and Melanesians. In both the metric and nonmetric tooth traits, the Hoabinian and Da But specimens had dental features similar to the prehistoric Southeast Asians and the Australo-Melanesians, but also had partially Northeast Asian characteristics. On the other hand, the Northeast Asian features become distinct in the dentition of the Dong Son people, which have close ties with the modern Vietnamese. Thus, the Vietnamese, as well as the other modern Southeast Asians and Japanese, are considered to be a blend of indigenous Southeast Asians who are closely related to the Australo-Melanesian lineage, and migrants from Northeast Asia.     

A new Late Eocene primate from the Krabi Basin (Thailand) and the diversity of Palaeogene anthropoids in southeast Asia

According to the most recent discoveries from the Middle Eocene of Myanmar and China, anthropoid primates originated in Asia rather than in Africa, as was previously considered. But the Asian Palaeogene anthropoid community remains poorly known and inadequately sampled, being represented only from China, Myanmar, Pakistan and Thailand. Asian Eocene anthropoids can be divided into two distinct groups, the stem group eosimiiforms and the possible crown group amphipithecids, but the phylogenetic relationships between these two groups are not well understood. Therefore, it is critical to understand their evolutionary history and relationships by finding additional fossil taxa. Here, we describe a new small-sized fossil anthropoid primate from the Late Eocene Krabi locality in Thailand, Krabia minuta, which shares several derived characters with the amphipithecids. It displays several unique dental characters, such as extreme bunodonty and reduced trigon surface area, that have never been observed in other Eocene Asian anthropoids. These features indicate that morphological adaptations were more diversified among amphipithecids than was previously expected, and raises the problem of the phylogenetic relations between the crown anthropoids and their stem group eosimiiforms, on one side, and the modern anthropoids, on the other side.     

Deciduous dental morphology and the biological affinities of a late Chalcolithic skeletal series from western India

Morphological variations of the dental crown and roots provide valuable data for determining the genetic affinities and evolutionary adaptedness of prehistoric human skeletal populations. This paper documents morphological variations of a sample of deciduous teeth from the late Chalcolithic farming village of Inamgaon (1600-700 B.C.) in western India. Hanihara's (1963) grading system of deciduous dental traits was employed in assessing the degree of expression of shovel-shape of incisors, cusp number of upper and lower first molars, hypocone variation, Carabelli's trait, cusp number of lower second molars and the protostylid. Turner's (1970) classification was used to determine presence and size of accessory cusps: entoconulid (C-6) and metaconulid (C-7). Comparative evaluation of the Inamgaon deciduous dental data is hampered by the absence of data for dental features of living and prehistoric South Asian populations. Many of the traits observed in the Inamgaon series exhibit a frequency of occurrence intermediate between figures characteristic of the "Mongoloid" dental complex and the "Caucasoid" dental complex.     

Fossil horses from "Eohippus" (Hyracotherium) to Equus, 2: rates of dental evolution revisited

Rates of dental evolution are calculated for four upper first molar (M¹) characters of 26 ancestral-descendant species pairs of Cenozoic horses from North America. On average, crown height evolved significantly more rapidly (= 0.104 darwins, d) than did occlusal dimensions (length and width; = 0.045 d and 0.047 d, respectively). As might be expected, low-crowned Eocene and Oligocene horses ( Hyracotherium through Mesohippus ) exhibit relatively slow rates of dental evolution. During the major early Miocene adaptive shift from browsers to grazers ( Parahippus to Merychippus ), only crown height evolved rapidly. Advanced Miocene-Pliocene three-toed hipparions and one-toed equines are generally normal, or horotelic, in their rates of dental evolution. The most rapid rates are exhibited in Miocene browsing anchitheres and the dwarf genus Pseudhipparion. Horses do not show the very high rates of dental evolution reported elsewhere for Paleogene mammals. The traditional notion of horses being a prime example of rapid morphological evolution as seen from the fossil record is not corroborated by the data presented here.     

Dental perspectives on the population history of Southeast Asia

This article uses metric and nonmetric dental data to test the "two-layer" or immigration hypothesis whereby Southeast Asia was initially occupied by an "Australo-Melanesian" population that later underwent substantial genetic admixture with East Asian immigrants associated with the spread of agriculture from the Neolithic period onwards. We examined teeth from 4,002 individuals comprising 42 prehistoric and historic samples from East Asia, Southeast Asia, Australia, and Melanesia. For the odontometric analysis, dental size proportions were compared using factor analysis and Q-mode correlation coefficients, and overall tooth size was also compared between population samples. Nonmetric population affinities were estimated by Smith's distances, using the frequencies of 16 tooth traits. The results of both the metric and nonmetric analyses demonstrate close affinities between recent Australo-Melanesian samples and samples representing early Southeast Asia, such as the Early to Middle Holocene series from Vietnam, Malaysia, and Flores. In contrast, the dental characteristics of most modern Southeast Asians exhibit a mixture of traits associated with East Asians and Australo-Melanesians, suggesting that these populations were genetically influenced by immigrants from East Asia. East Asian metric and/or nonmetric traits are also found in some prehistoric samples from Southeast Asia such as Ban Kao (Thailand), implying that immigration probably began in the early Neolithic. Much clearer influence of East Asian immigration was found in Early Metal Age Vietnamese and Sulawesi samples. Although the results of this study are consistent with the immigration hypothesis, analysis of additional Neolithic samples is needed to determine the exact timing of population dispersals into Southeast Asia.     

The dentition of New Britain West Nakanai Melanesians. VIII. Peopling of the pacific

The dental crown morphology and size of 48 male West Nakanai, New Britain, Melanesians is described and compared with other Pacific and Asian dental samples. The West Nakanai dentition is like those of other Melanesians, much less like those of Polynesians and Micronesians, and very dissimilar to teeth of modern and Neolithic Southeast Asians. It is suggested that the origin of the modern Melanesian dental pattern (large but simplified teeth) was probably in Melanesia, not Southeast Asia as the orthodox view of a Hoabinhian-Australmelanesian relation claims.     

陕西陇县战国时代人类牙齿形态特征

本文记述了陕西县出土的战国时代人类牙齿形态特征。数据对比和统计分析显示：与华北新石器时代人类相比,陇县人类牙齿形态特征除具有典型蒙古人种的共同特点外,与现代华北人更为接近。作者认为在近一万年内华北地区人类在体质特征上经历了某种规律性的演化过程,其表现特点是朝向现代华北人的方向转变。这一过程反映了东北亚地区人类在这一特定时间内体质特征的微观演化趋势。     

Evolutionary correlations of polycyclic shoot growth in Acer (Sapindaceae)

Two strategies have evolved in understory trees in relation to light availability: maximization of light capture and shade tolerance. In the genus Acer, light capture is favored by a suite of traits maximizing twig thickness and leaf size and minimizing the density of branching in the crown. In contrast, shade tolerance is enhanced by minimizing crown area, crown volume, and total leaf area per unit height. Maples with polycyclic shoot growth (i.e., successive flushes of shoot growth separated by a resting phase within the same vegetative period) may benefit from the prolonged growth by growing more and increasing total leaf area; thus we hypothesize that polycyclism is evolutionarily correlated with the suite of traits related to light capture. We tested this hypothesis using different phylogenetic trees to explore correlations between polycyclism and both suites of traits. Polycyclism was correlated with the suite of traits maximizing light capture, suggesting that polycyclic maples are "optimists" (i.e., they make vigorous vertical extensions in rich light) and monocyclic maples are "pessimists" (i.e., they wait in the dark understory until a gap is opened). Both strategies have been described for different floras, and interestingly, polycyclic species recruit over a wider range of environments than the monocyclic species.     

Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis

Mandibular premolars are increasingly used in taxon-specific diagnostic analyses of hominins. Among the principal difficulties in these evaluations is the absence of discrete, discernible, and comparable anatomical structures for rigorous quantitative assessment. Previous research has addressed either internal crown surface features (such as cusps and fossae) or the morphology of the crown outline. In the present paper, we integrate both types of information in the examination of morphological variation of lower P4s (n = 96) among various fossil hominin species with an emphasis on genus Homo. We use a set of 34 2D landmarks combining coordinate data from four classical dental landmarks on the occlusal surface and 30 sliding semilandmarks of the crown outline. Our results indicate that external shape variation is closely related to the configuration of the occlusal morphological features and influenced by dental size. The external and internal shapes of P4 are polymorphic but still useful in depicting a primitive-derived gradient. The primitive pattern seems to have been an asymmetrical contour with a mesially displaced metaconid, development of a bulging talonid, and a broad occlusal polygon. The trend toward dental reduction during the Pleistocene produced different morphological variants with a reduced occlusal polygon and decreased lingual occlusal surface in later Homo species. Homo heidelbergensis/neanderthalensis have fixed plesiomorphic traits in high percentages, whereas in modern humans a symmetrical outline with a centered metaconid and talonid reduction evolved.     

Modern human origins: continuity, replacement, and masticatory robusticity in Australasia

Morphological evidence for a Multiregional (MR) model of human origins is suggested by a series of “linking traits” seen in the crania of late Javanese Homo erectus from Ngandong and anatomically modern Australian crania. A few studies that consider the genetic, structural, or functional aspects of these regional traits suggest their appearance is heavily influenced not by shared phylogeny but by a common “strong” masticatory pattern. Using dental occlusal areas, external mandibular metrics, internal biomechanical properties of the mandibular corpus measured from CT scans, and nonmetric traits associated with the attachment of masticatory muscles, we test the hypothesis that Australians exhibit evidence of a “strong” masticatory pattern. We use a mixed-sex comparative human sample (n = 415) that includes precontact Alaskans from Point Hope and the Aleutian Islands, Californians, Peruvians, an urban forensic sample, and the late Pleistocene Afalou-Taforalt sample. In comparison with recent humans known to exhibit such patterns, Australian mandibles show none of the expected changes related to producing and dissipating heavy occlusal loads. This is true regardless of whether external or internal mandibular dimensions are considered, albeit Australians show large occlusal areas and relatively large section modulus indices. Thus, a prime functional argument proposed for the origin of some Australian regional features is not supported by these data.     

The evolution of pelvic osteology and soft tissues on the line to extant birds (Neornithes)

Substantial differences in pelvic osteology and soft tissues separate crown group crocodylians (Crocodylia) and birds (Neornithes). A phylogenetic perspective including fossils reveals that these disparities arose in a stepwise pattern along the line to extant birds, with major changes occurring both within and outside Aves. Some character states that preceded the origin of Neornithes are only observable or inferable in extinct taxa. These transitional states are important for recognizing the derived traits of neornithines. Palaeontological and neontological data are vital for reconstructing the sequence of pelvic changes along the line to Neornithes. Soft tissue correlation with osteological structures allows changes in soft tissue anatomy to be traced along a phylogenetic framework, and adds anatomical significance to systematic characters from osteology. Explicitly addressing homologies of bone surfaces reveals many subtleties in pelvic evolution that were previously unrecognized or implicit. I advocate that many anatomical features often treated as independent characters should be interpreted as different character states of the same character. Relatively few pelvic character states are unique to Neornithes. Indeed, many features evolved quite early along the line to Neornithes, blurring the distinction between 'avian' and 'non-avian' anatomy.     

Genetic structure of a tribal population, the Yanomama Indians. XIII. Dental microdifferentiation.

Data are presented on the frequency of the following eight dental traits in 635 Yanomama and 65 Makiritare Indians: upper central incisor rotation or winging, shoveling of maxillary incisors, maxillary molar hypocone reduction, Carabelli's trait, mandibular molar cusp number, mandibular molar cusp pattern rotation of second lower premolar, and pattern of second lower premolar cusps. Yanomama dentition is unusual in the high frequency of six cusps on the mandibular molars. There is marked dental microdifferentiation between villages; significant agreement was observed between a matrix of pairwise "dental distances" based on six morphological traits and corresponding matrices based on 11 genetic systems and on geographic location.     

Human remains from the Pleistocene-Holocene transition of southwest China suggest a complex evolutionary history for East Asians

Background

Later Pleistocene human evolution in East Asia remains poorly understood owing to a scarcity of well described, reliably classified and accurately dated fossils. Southwest China has been identified from genetic research as a hotspot of human diversity, containing ancient mtDNA and Y-DNA lineages, and has yielded a number of human remains thought to derive from Pleistocene deposits. We have prepared, reconstructed, described and dated a new partial skull from a consolidated sediment block collected in 1979 from the site of Longlin Cave (Guangxi Province). We also undertook new excavations at Maludong (Yunnan Province) to clarify the stratigraphy and dating of a large sample of mostly undescribed human remains from the site.

Methodology/Principal Findings

We undertook a detailed comparison of cranial, including a virtual endocast for the Maludong calotte, mandibular and dental remains from these two localities. Both samples probably derive from the same population, exhibiting an unusual mixture of modern human traits, characters probably plesiomorphic for later Homo, and some unusual features. We dated charcoal with AMS radiocarbon dating and speleothem with the Uranium-series technique and the results show both samples to be from the Pleistocene-Holocene transition: ∼14.3-11.5 ka.

Conclusions/Significance

Our analysis suggests two plausible explanations for the morphology sampled at Longlin Cave and Maludong. First, it may represent a late-surviving archaic population, perhaps paralleling the situation seen in North Africa as indicated by remains from Dar-es-Soltane and Temara, and maybe also in southern China at Zhirendong. Alternatively, East Asia may have been colonised during multiple waves during the Pleistocene, with the Longlin-Maludong morphology possibly reflecting deep population substructure in Africa prior to modern humans dispersing into Eurasia.