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PubMed1980

Odontometric microdifferentiation of transplanted Mexican indian populations: Cuanalan and Saltillo.

This study documents odontometric variation in four populations of related genetic background. It is found that the transplanted populations of Cuanalan and Saltillo have undergone significant microdifferentiation in tooth size relative to the two home valley populations. The extent and direction of this microdifferentiation is seen as reflecting differential amounts of admixture from African and European sources in demographic subunits of the two transplanted populations. The dental variables found to discriminate significantly between populations are the same variables predicted to be evolutionarily labile by Butler's Field Theory. Principal component analysis confirms the presence of morphological fields in these data and supports the position that each class has a stable tooth, with stability decreasing with increasing distance from the key tooth. The importance of hybridization in determining which variables significantly discriminate between populations is confounded by the effects of development of the dentition in morphogenetic fields. These data suggest that odontometric data provide an adequate, if somewhat conservative, base from which to evaluate microdifferentiation of human populations.

Female↗
PubMed1980

Tooth size of Ticuna Indians, Colombia, with phenetic comparisons to other Amerindians.

This study reports an odontometric analyses of unadmixed, adult Ticuna Indians, Colombia, South America. This group is characterized by crown diameters intermediate in size relative to the known Amerindian range and, in turn, to the range in modern man. Sex dimorphism is absent in Ticuna tooth size; there is a strong retention of the MI > M2 size sequence. The Ticuna are compared multivariately to other Indian groups reported in the literature, using the size and shape coefficients of L.S. Penrose. Tooth size clusters the groups into small, medium, and large-toothed classes, but does not yield a pattern attributable to known genetic or historical affinities. Shape coefficients distinguish Indians from non-Indians (Caucasian, Negroid, and Australian samples), primarily on the basis of 11-12 proportionalities. Neither size nor shape discriminates between North and South American groups.

Adolescent↗
PubMed1980

Dental asymmetry as a measure of environmental stress in the Ticuna Indians of Colombia.

The magnitude of fluctuating dental asymmetry is reported for a marginally Westernized, horticultural Indian group, the Ticuna of the Region Amazonas, Colombia. Asymmetry is lower than in other Amerindian and Eskimo groups reported to date, which accords with the adequacy and reliability of traditional food sources and complements the claim that protein intake is at or above minimum requirements. Partitioning the variation by sex, arcade, dimension, and tooth discloses several statistically significant effects. Among these: 1) females are proportionately more asymmetric than males; 2) maxillary teeth are more asymmetric than their mandibular counterparts; 3) the mesiodistal dimension is less canalized than buccolingual width in the maxilla, but is more asymmetric in the mandible; and 4) the pattern of asymmetry corresponds closely with the morphogenetic gradients within each tooth field, suggesting that bilaterality provides an additional measure for disclosing underlying genetic and ontogenetic patterns in the dentition.

Adolescent↗
PubMed1980

The natural history of the helicoidal occlusal plane and its evolution in early Homo.

In modern man the pitch of the occlusal plane may vary along the tooth-row. When anterior cheek-teeth show a plane sloping upward palatally, whilst that on posterior cheek-teeth slopes upward buccally, there results a twisted or helicoidal occlusal plane (Ackermann). Several hypotheses have been proposed for the structural basis of the helicoidal occlusal plane. Campbell's proposal ('25) has gained widest acceptance, namely that the helicoid results from anteroposterior differences in upper and lower alveolar arch width. In the early 1960s, while studying the Olduvai hominids assigned to Homo habilis, the author noted changing occlusal slopes along the tooth-row and a slight helicoid, although these featues had not been noted in other early hominids. Subsequently, Wallace showed a total absence of the helicoid from South African australopithecines, and its presence in Swartkrans Homo, SK 45 and SK 80. Recent studies confirm the presence of the helicoid in all available specimens of H. habilis, including Stw 53 found at Sterkfontein in 1976. Hence, this trait may distinguish between Australopithecus and early Homo. Measurements of the maxillary arch widths have shown that, whereas in Australopithecus arch widths increase to a maximum at M3, in early Homo maxillary arch widths are greatest at M2. The decline in posterior maxillary arch width is part of a general reduction of that region. Thus despite striking elongation of premolars and M1 in early Homo, M2 and M3 are mesiodistally abbreviated. It is hypothesized that the onset of posterior arch reduction, with the appearance of a helicoid, was a structural and functional concomitant of the transition from the presumed australopithecine ancestor to H. habilis.

Animals↗
PubMed1980

Middle Pleistocene hominids from Olduvai Gorge, northern Tanzania.

Cranial, dental, and mandibular remains of eight Olduvai hominids are described in detail. Four individuals were recovered in situ in Beds II to IV, while three more are most probably derived from Bed IV, the Masek Beds and the Lower Ndutu Beds. One specimen is of uncertain provenance. Deposits from which the fossils were collected range from late Lower Pleistocene to Middle Pleistocene in age. Of particular interest are three fragmentary lower jaws, which can be compared to mandibles of Homo erectus known from localities in Northwest Africa and China. Olduvai hominid 22, a nearly complete half mandible with crowns of P3-M2 in place, shares many anatomical features with fossils from Ternifine and Choukoutien. This individual is also similar to a jaw from the Kapthurin Formation west of Lake Baringo, Kenya. How best to interpret these comparisons is not clear, but in view of marked similarities between specimens representing geographically diverse populations from different time periods, it may be unwise to rely on mandibular evidence alone to document the presence of regional lineages. Gradual change and continuity within a sequence of Northwest African Homo fossils has been endorsed by many workers, but such hypotheses cannot be tested adequately with the fragmentary jaws available.

Algeria↗
PubMed1980

Heritability of deciduous tooth size in Australian aboriginals.

The contributions of genetic and environmental influences to observed variabiliy of deciduous tooth size were quantified in a group of Australian aboriginals. Phenotypic variability was partitioned into four components; between sides, between fathers, between mothers, and between offspring. Results suggested that about 58% of deciduous tooth-size variability was due to additive genetic variance and 15% to common environmental variance. It appears that additive genetic variance is similar in both deciduous and permanent dentitions, but that common maternal effects are more important in determining deciduous tooth-size variability.

Australia↗
PubMed1980

Complex segregation analysis of Carabelli's trait in a Melanesian population.

A complex segregation analysis was performed on Carabelli's trait on the upper first molar utilizing 358 nuclear families from the Solomon Islands of Bougainville and Malaita. Simultaneous estimation of three sources of variation by the method of maximum likelihood demonstrates a significant effect of shared sibling environment which accounts for over 19% of the variance in liability for the trait. In addition, a statistically significant major gene influence is discussed and suggestions for quantifying individual liability levels for this and other dental traits are outlined.

Black People↗
PubMed1980

Morphometric affinities of gigantopithecus.

Multivariate analyses, supplemented by univariate statistical methods, of measurements from mandibular tooth crown dimensions and the mandible of Gigantopithecus blacki, G. bilaspurensis, Plio-Plelstocene hominids, Homo erectus, and seven Neogene ape species from the genera Proconsul, Sivapithecus, Ouranopithecus, and Dryopithecus were used to assess the morphometric affinities of Gigantopithecus. The results show that Gigantopithecus displays affinities to Ouranopithecus and to the hominids, particularly the Plio-Plelstocene hominids, rather than to the apes. Ouranopithecus demonstrated dental resemblances to G. bilaspurensis and the Plio-Pleistocene hominids but mandibular similarities to the apes. Results of analyses of tooth and mandibular shape indices, combined with multivariate distance and temporal relationships, suggest that Ouranopithecus is a more likely candidate for Gigantopithecus ancestry than is Silvapithecus indicus. Shape and allometric differences between G. bilaspurensis and the robust australopithecines weaken the argument for an ancestral-descendant relationship between these groups. The results support the hypothesis that Gigantopithecus is an extinct side branch of the Hominidae.

Animals↗
PubMed1981

Allometric analysis of dental variation in a human population.

There exists an extensive literature that deals with interspecific allometry, eg, brain size-body size relationships among species. Yet comparatively little attention has been paid to intraspecific or static adult allometry. An intraspecific allometric analysis was conducted on the complete permanent dentition of a prehistoric American Indian population (N = 156). Mesiodistal and buccolingual measurements were logarithmically transformed and regressed on log transformations of femur length, an estimate of body size. When measurements of antimeric teeth were introduced together into common regressions on femur length, 20 of the 32 slopes were significantly different from zero. Thirty-one of the slopes ranged between zero and one and clustered between 0.2 and 0.4. Hence, negative allometry describes the tooth size-body size association, ie, taller individuals in general possess absolutely but not relatively larger teeth than shorter individuals. In addition, no significant sex differences for the regression slopes were observed. Though significantly correlated, tooth size and body size variables are too weakly associated to permit accurate predictions from regression equations. Evolutionary implications of intraspecific dental allometry are discussed.

Body Height↗
PubMed1981

A differential environmental effect on human anterior tooth size.

Factor-analytic studies of human tooth size routinely exhibit separate factors for the mesiodistal and buccolingual dimensions of anterior teeth but a single factor each for premolar and molar size. This observed independence within the anterior field is shown to be attributable to a much larger effect of environmental factors on the buccolingual vs. the mesiodistal diameters, a significant cause of which may be calculus accumulation hitherto unrecognized in the relevant literature. The heritability of dental dimensions is also discussed.

Dental Calculus↗
PubMed1981

Maxillary first premolar angular differences between North American Indians and non-North American Indians.

A quantitative technique for obtaining angular data on human maxillary first premolar teeth is presented. Measurement indicates that North American Indian buccal cusps are either buccolingually compressed mesially, or expanded distally, or both, when compared with non-Indian teeth. Surprisingly, data on Chinese and Eskimo samples are similar to non-Indian teeth rather than Indian teeth. Similar techniques may be applied to the more complex multicusped molar teeth in order to extract quantitative data from them.

Asian People↗
PubMed1981

Developmental correlates of crown component asymmetry and occlusal discrepancy.

To improve our understanding of dental asymmetry, more anatomically discriminating measurements than maximum crown dimensions were used. The relation between antimeres and opponents in permanent first molar teeth of 192 twins were studied with respect to crown components measures. Several statistical methods were used to describe asymmetry and discrepancy of occluding units to correlate with developmental stress indicators such as zygosity, birth weight, and congenital disease. To varying degrees, developmental correlates are found to be associated with asymmetry. The amount of occlusal discrepancy seems to be a direct function of bilateral asymmetry. Heterogeneity of MZ-DZ total (among plus within pair) variances occurs fairly consistently for asymmetry but not for discrepancy, implying differential environmental influences between zygosities regarding asymmetry. Genetic variance estimates, designed to be unbiased by differences in environmental variances, are significant for cusp size but not for asymmetry. Our results suggest that asymmetry at the individual cusp level may be an indicator of developmental disruption and that environmental effects, particularly prenatal, may be greater for antimeric units than for occluding units.

Birth Weight↗
PubMed1981

Dimensional characteristics of the Filipino dentition.

This study concerns odontometric analysis of the Tagalog Filipinos in Manila, Philippines. Mesiodistal and buccolingual dimensions of the permanent dentition, a total of 56 variables, were studied in 100 males and 152 females. Results showed that their absolute tooth size was small. Relative tooth size, however, seemed to reflect their Southeast Asian Mongoloid origin. From univariate analysis, considerable male-female differences were shown in most of the variables studied. When correlation effects among the teeth were held constant through multivariate analysis, male-female distance was found to be small and substantial overlapping of the two multivariate distributions was evident. Only four variables could be shown by stepwise discriminant analysis to contribute significantly to the distance. Even the mandibular canine, as the strongest discriminator, could only account for 16.4% of the total multivariate distance. These contrasting findings for sex dimorphism in a set of teeth taken singly and taken jointly indicate that there are factors other than the teeth themselves that are expected to play important roles in determining overall male-female size differences in the set of teeth, and that these differences may not be as clear-cut as univariate analysis suggests.

Adolescent↗
PubMed1981

On the definition of variables in studies of primate dental allometry.

Cranial and dental measurements are taken on 253 adult female primates from 32 species. Regression equations are calculated to determine allometric relationships between anterior tooth size, posterior tooth size, and body size. When cranial length or skull length is used as the measure of general size, the results of the equations differ from when body weight is the reference dimension. Similarly, using different definitions of posterior tooth size (such as mandibular second molar length and maxillary postcanine area) alters results substantially. The same occurs with different definitions of anterior tooth size. It has been common in studies of primate dental allometry to generalize from the specific variables measured to broad functional interpretations. However, highly correlated variables cannot be substituted one for another in allometric analyses without important changes in the results of the equation. Interpretation of allometric data is more highly restricted to the precise variables measured in a particular study than has been generally recognized.

Animals↗
PubMed1981

Deciduous tooth dimensions in fetal rhesus monkeys from mothers with induced diabetes.

Thirty-four measurements of the deciduous dentition in 21 fetal rhesus monkeys from diabetic mothers (FDM) and 36 nondiabetic fetuses were compared in order to assess the effects of induced maternal diabetes on the teeth of third-trimester fetuses. After exclusion of 14 variates due to significant age-related variation, univariate statistical analysis suggested a trend toward smaller teeth in the FDMs. Multivariate discriminant function analysis indicated not only a clear separation between the two groups, with molar breadths and some incisor length and breadths serving as the best discriminators, but also that the deciduous dental dimensions in FDMs are smaller than in nondiabetic fetuses.

Animals↗
PubMed1981

Sexual dimorphism in two subspecies of Ethiopian Baboons (Papio Hamadryas) and their hybrids.

Sexual dimorphism in mammals has been related to such variables as absolute body size, ecology, and various aspects of social behavior. Attempts to relate dimorphism to any of these variables have necessarily used small heterogeneous samples to represent the relevant species. We are concerned by the inevitable exclusion of any measure of variability in dimorphism and the consequent impossibility of assessing the significance of observed interspecific differences. In this paper we describe aspects of sexual dimorphism in anubis, hamadryas, and hybrid baboons from Ethiopia. Samples are large enough to permit a measure of intrapopulational variability. Hamadryas baboons are more dimorphic than anubis in epigamic features, but not in postcanine dentition, nor, contrary to previous reports, in body weight or canine tooth size. Hybrid males are more hamadryas-like and hybrid females more anubis-like, as would be predicted by the proposed mechanism for the establishment of the hybrid zone, namely the capture of anubis females by hamadryas males.

Animals↗
PubMed1982

The morphogenetic triangle: a new conceptual tool for application to problems in dental morphogenesis.

A hypothetical mathematical model of human dental crown height attainment during morphogenesis was developed. The model is based on well-known histologic stages of tooth development from initiation to crown completion, with special emphasis on the dynamics and life-cycle of the cells of the inner enamel epithelium. From three temporal events (P, initiation of proliferation; D, initiation of differentiation; C, crown completion), and crown height (H) measured at the dentino-enamel junction, a morphogenetic triangle PDZ can be constructed where Z = coordinates of H and C at the time of crown completion. The slope of lines PZ and DZ represent average proliferation rate (Rp) and average differentiation rate (Rd) of the inner enamel epithelium, respectively, during crown formation. From data available in the literature, and based on morphogenetic triangle principles, Rp and Rd were calculated for the deciduous and succedaneous dentitions. A strong positive correlation between Rp and Rd was observed throughout the 20-tooth series (r = 0.996); however, Rp and Rd showed moderately strong negative associations with H, P, D, C, and the intervals between PD, PC, and DC. The smaller deciduous tooth in each deciduous:permanent pair was associated with faster Rp and Rd, and shorter intervals between initiation of proliferation, initiation of differentiation, and crown completion. The data generated in this analysis of a hypothetical dentition, while not definitive, provide new insights and a theoretical basis for a broader understanding of the basic mechanisms involved in the attainment of certain tooth dimensions during morphogenesis.

Dental Enamel↗
PubMed1982

Japanese tooth size: past and present.

Mesial-distal and buccal-lingual crown measurements were made on male and female samples of recent Japanese teeth from three locations, Fukuoka, Kyoto, and Tokyo, and for Hokkaido Ainu and Koreans. Similar data were collected for prehistoric Middle-to-Late Jomon Japanese and from Yayoi specimens representing the first agriculturalists to appear in Japan. From a tooth-by-tooth comparison of cross-sectional areas, it was shown that the modern Japanese samples did not differ from one part of Japan to another. Korean tooth size also is not significantly different from Japanese, while Ainu have the smallest teeth recorded in Asia. The Yayoi who brought rice to Japan about 300 B.C. came in with teeth that were the same size as Chinese Neolithic teeth. They encountered a resident Jomon population whose teeth were 10% smaller. From tooth size measures alone, it is most economical to suggest that, if the rates of reduction observed elsewhere in the world applied in Japan, the recent Ainu would best be regarded as the direct descendants of the Jomon, while the modern Japanese are the results of in situ reduction from the incoming Yayoi. Other aspects of craniofacial morphology suggest that some Jomon was incorporated by the Yayoi. The modern Japanese, then, while predominantly derived from the Yayoi, would include a Jomon component.

Asian People↗