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PubMed1983

Fluctuating asymmetry in molar dimensions and discrete morphological traits in Pima Indians.

Asymmetry in mesiodistal and buccolingual crown diameters and in eight morphologic crown traits of permanent first and second molars was analyzed in a large Pima Indian sample. Analysis of antimeric differences indicates no consistent evidence for directional asymmetry in Pima molars for either dimensions or morphologic traits. Second molars show greater degrees of metric and morphologic asymmetry than first molars. There is no conclusive evidence for either sex differences in magnitude of asymmetry or relationships between tooth size and morphologic asymmetry. Nonparametric correlations computed between asymmetry in crown dimensions and morphological traits show no significant interaction except where morphological trait development affected crown measurements. The distributions of antimeric differences for dimensional and morphologic traits demonstrate significant leptokurtic deviations from normality. This indicates fluctuating asymmetry in Pima Indians may result from several different sources of developmental variation.

Arizona↗
PubMed1983

Formation of the permanent dentition in Arikara Indians: timing differences that affect dental age assessments.

This report concerns one problem encountered with application of American white dental formation standards to age assessment of sub-adults of archaeological context. Dental ages for eight mandibular permanent teeth and maxillary central and lateral incisors of Arikara Indian immature skeletons were determined according to degree of crown or root mineralization. Ages assigned to the various teeth of the same individual were compared. They showed similarities as well as patterned differences. First premolar, second premolar, and mandibular incisor ages closely approximated one another. In relation to this complex, dental ages for maxillary incisors and mandibular second molars were older by 0.5 to 1.1 years. Developmental ages assigned to individuals on the basis of third molars showed relative advancement by more than 2 years. The systematic occurrence of these observations reflects more than just individual variability; it shows the presence of population differences in tooth-formation timing. Timing differences complicate assessment of dental ages needed for growth or demographic studies.

Aging↗
PubMed1983

The allometry of relative cusp size in hominoid mandibular molars.

The crown area (MCBA) and cusp areas of mandibular molars of Homo sapiens (M-1 = 131; M-2 = 71), Gorilla (M-1 = 25) and Pongo (M-1 = 24) were studied to determine whether the relative size of the mesial and distal cusps are related to overall crown size. Allometric trends were assessed by examining the correlation between relative cusp areas and MCBA and by calculating the slope of the regression line of log cusp area and log MCBA. With the exception of the metaconid in the Homo sapiens M-2S, the results of the intraspecific analyses provide little evidence of an allometric trend for relative reduction of the mesial cusps with increasing crown size. None of the samples provide consistent or reliable evidence of such a trend for the protoconid, nor do the M-1 samples provide evidence for such a trend for the metaconid. The evidence from the distal cusps is also mixed: positive allometry for the entoconid for the Homo sapiens M-2S and for the hypoconulid for the Homo sapiens M-1S, with no departure from isometry in either Gorilla or Pongo. The interspecific data provide no evidence of any trend for the mesial cusps to decrease or the distal cusps to increase in importance in larger teeth. If one accepts the proposition that the static allometric trends observed in this study are reasonable analogues for any allometric relationships within, or between, fossil hominid taxa, then the evidence presented above does not support the hypothesis that the reduction of the trigonid, which is observed in the "robust" australopithecines, is an allometric phenomenon.

Adult↗
PubMed1984

A metrical comparison of maxillary first premolar form.

In a study of maxillary right first premolar morphology, multivariate analysis showed varying degree of separation between four human ethnic groups depending upon the actual metrical profile included in the analysis. Such ethnic discriminations were not possible from visual inspection or univariate analysis of individual crown diameters. Although the interpretation of such ethnic contrasts remains obscure, this study demonstrated the potential of multivariate statistical techniques in the investigation of odontometric data.

Analysis of Variance↗
PubMed1984

Principal axis analysis of dental attrition data from two Australian Aboriginal populations.

Dental attrition scores from two distinct Australian Aboriginal populations were compared by principal axis analysis. The first group was composed of members of the Narrinyeri group who occupied the river basin and mouth of the River Murray. The second group consisted of members of the Kaurna tribe who occupied the coastal plain to the west of the Narrinyeri. The groups were isolated both physically and culturally and as a result differences in patterns of tooth wear might be expected. In the Narrinyeri sample, attrition tended to be more rapid in females for all but the anterior teeth. The only sex difference in the Kaurna was for the maxillary central incisors, which wore more rapidly in females. Interpopulation differences in the pattern of tooth wear were also evident. The incisors, canines, and premolars of Kaurna subjects tended to wear more rapidly, while the rate of posterior tooth wear tended to be greater in the Narrinyeri. The application of the principal axis method to quantitative attrition data provided a sensitive, objective evaluation of tooth wear. The reasons for the observed differences between the two groups are still not completely clear but may reflect both functional and morphological differences between groups.

Australia↗
PubMed1984

A genetic model of dental reduction through the probable mutation effect.

A simulation approach is used in order to elucidate the nature of the hypothesized "probable mutation effect" as it applies to dental reduction in man. Computer-generated simulations of the accumulation of mutations in a human gene pool show the results of the proposed model under the influence of various parameters, as well as illustrating the nature of such genetic change through time. This approach supports a polygenic model of the probable mutation effect as a viable hypothesis for an explanation of the dental reduction which has occurred in some human populations over the last 40,000 years.

Humans↗
PubMed1984

Fluctuating dental asymmetry and measurement error.

Differences between the dimensions of left and right molar teeth are analyzed in the context of measurement error while considering the power of the F-Ratio. Molar teeth from two Nubian cemeteries, 24-S-46 and 21-R-2, excavated at Kulubnarti, Sudan, were initially measured, and then remeasured to obtain data for assessing fluctuating dental asymmetry and measurement error. As has been demonstrated by other investigators, the power of the F-Ratio for detecting small, but real differences, that might exist between antimeric dimensions when sample sizes are small, as they usually are with archeological materials, limits interpretation. In addition, an analysis of measurement error indicates that such error can have a confounding effect upon interpretations of the degree of fluctuating dental asymmetry that exists even in very large samples that exceed the size of typical archeological samples.

Humans↗
PubMed1984

Reduced tooth size in 45,X (Turner syndrome) females.

Mean values and variances of deciduous and permanent tooth dimensions were compared between 121 45,X (Turner syndrome) females and 171 control subjects to clarify the role of the X chromosome on dental development. Although deciduous molars tended to be smaller than normal in 45,X females, there was no evidence of a reduction in tooth size for deciduous anterior teeth. In the permanent dentition, all mesiodistal dimensions were significantly smaller in 45,X females but only some of the buccolingual dimensions were smaller. The findings for deciduous tooth-size may reflect a sampling effect related to the extremely high frequency of spontaneous abortion in 45,X individuals. Results for permanent teeth are consistent with the concept of a decrease in enamel thickness in 45,X females.

Dental Enamel↗
PubMed1986

Post-pleistocene changes in tooth root and jaw relationships.

Mandibles of 126 sexed skeletal specimens, from Near Eastern sites dating over the past 12,000 years were radiographed. From the radiographs obtained, digitised tracings were made of crown length (mesiodistal), root height and width, and corpus height mesial to the premolars and first and second molars. The data obtained were analysed using rank transformation procedures. The significance of unidirectional trends in relation to periods sampled was examined graphically and analytically through linear regression analysis of the ranks on the chronological scale, and Spearman's rank correlation was used to compare relationships between different parameters of individual teeth in different periods. Significant reduction was found in crown length between 12,000 B.P. and 6,000 B.P., but no further reduction was found between 6,000 B.P. and 1,000 B.P. Little change was observed in root size, but corpus height showed significant reduction over the past 6,000 years. The differences observed in the timing and extent of reduction in crown, root, and corpus height are associated with a low intrapopulation correlation between them.

Bicuspid↗
PubMed1986

Dental reduction in post-pleistocene Nubia.

Tooth size changes among Nubian archaeological populations dating from the Mesolithic through the Christian era, a period of approximately 12,000 years, are analyzed. Standard length and breadth dimensions of all permanent teeth from several cultural horizons are combined to form three large samples: Mesolithic, 10000-70000 B.C.; Agriculturalist, 3300-1100 B.C. (A-group, C-group, Pharaonic); and Intensive Agriculturalist, A.D. 0-1400 (Meroitic, X-Group, Christian). Such information not only fills a void in the knowledge of Nubian skeletal biology, but also provides a much needed African reference point for the comparison of tooth size data among anatomically modern Homo sapiens from various regions of the world. Changes in mean tooth size and associated t-tests reveal strong and significant reduction in dental size between the Mesolithic and Agriculturalist samples, followed by a continued although diminished trend of reduction for only the molar teeth between the two Agriculturalist groups. These patterns are best observed by examining tooth breadths, which are considered as the most reliable indicator of tooth size. Previously published odontometrics of the Nubian Mesolithic are briefly compared to the findings of this diachronic analysis of Nubian dental change.

Egypt, Ancient↗
PubMed1986

Dental metric assessment of the omo fossils: implications for the phylogenetic position of Australopithecus africanus.

The discovery of Australopithecus afarensis has led to new interpretations of hominid phylogeny, some of which reject A. africanus as an ancestor of Homo. Analysis of buccolingual tooth crown dimensions in australopithecines and Homo species by Johanson and White (Science 202:321-330, 1979) revealed that the South African gracile australopithecines are intermediate in size between Laetoli/hadar hominids and South African robust hominids. Homo, on the other hand, displays dimensions similar to those of A. afarensis and smaller than those of other australopithecines. These authors conclude, therefore, that A. africanus is derived in the direction of A. robustus and is not an ancestor of the Homo clade. However, there is a considerable time gap (ca. 800,000 years) between the Laetoli/Hadar specimens and the earliest Homo specimens; "gracile" hominids from Omo fit into this chronological gap and are from the same geographic area. Because the early specimens at Omo have been designated A. afarensis and the later specimens classified as Homo habilis, Omo offers a unique opportunity to test hypotheses concerning hominid evolution, especially regarding the phylogenetic status of A. africanus. Comparisons of mean cheek teeth breadths disclosed the significant (P less than or equal to 0.05) differences between the Omo sample and the Laetoli/Hadar fossils (P4, M2, and M3), the Homo fossils (P3, P4, M1, M2, and M1), and A. africanus (M3). Of the several possible interpretations of these data, it appears that the high degree of similarity between the Omo sample and the South African gracile australopithecine material warrants considering the two as geographical variants of A. africanus. The geographic, chronologic, and metric attributes of the Omo sample argue for its lineal affinity with A. afarensis and Homo. In conclusion, a consideration of hominid postcanine dental metrics provides no basis for removing A. africanus from the ancestry of the Homo lineage.

Animals↗
PubMed1986

Morphometrics of the anterior dentition in strepsirhine primates.

Size variations in the anterior dentition were analyzed for 26 species of strepsirhine primates. The upper and lower incisor rows of strepsirhines, like those of anthropoid primates, scale isometrically with body size. Within the order Primates, strepsirhines exhibit the smallest incisors relative to body size, followed in increasing size by tarsiers, platyrrhines, and catarrhines. If the lateral teeth of the indriid toothcomb are interpreted as incisors and not canines, correlations between mandibular tooth size variables and body weight are maximized. The upper incisors of strepsirhines are extremely small and frequently widely separated, most likely to minimize occlusion with the toothcomb. Species deviations for assorted size variables of the anterior dentition generally fail to reflect functional variations in the use of the anterior teeth; some of the variables, however, do reflect taxonomic differences within the Strepsirhini. Although toothcomb size variations among extant strepsirhines are more readily interpreted in terms of gum feeding and bark scraping than they are in terms of grooming, anterior dental morphology as a whole is more easily explained by a grooming hypothesis when existing models of toothcomb origins are considered.

Animals↗
PubMed1986

Fluctuating dental asymmetry as a measure of odontogenic canalization in man.

Fluctuating odontometric asymmetry was evaluated in 202 Lengua Indians and in 125 contemporary caucasoids using Euclidean map analyses, rescaled asymmetry values, and Naperian logarithmic transformations. Both populations showed bimodal distributions of canalizing ability, with significantly more Lengua Indians being less well canalized. Student t-tests indicated that significant interpopulation differences in rescaled asymmetry values centered around maxillary mesiodistal dimensions. Analyses of variance failed to show significant levels of sexual dimorphism in the magnitude of asymmetry for both populations. It is concluded that even in a relatively stress-free population, there exist some individuals who are less well canalized than others. When a population is subjected to elevated levels of parasitic and nutritional stress, the number of less-well-canalized individuals increases significantly.

Dental Pulp Cavity↗
PubMed1987

Upper pleistocene fossil hominids from Sri Lanka.

Between 1978 and 1983 hominid skeletal remains were collected from the cave sites of Batadomba lena and Beli lena Kitulgala in Sri Lanka (formerly Ceylon). These are the most ancient specimens of anatomically modern Homo sapiens found thus far in South Asia, radiocarbon dates placing them in the Upper Pleistocene. Morphometric analysis of the remains of some 38 individuals from the two sites indicates that these populations were characterized by medium stature, moderate to pronounced cranial and postcranial robusticity, medium-size permanent tooth crown measurements, prognathic alveolar facial proportions, and low incidence of osseous and dental pathological conditions. Comparisons of these ancient Sri Lankans with other prehistoric skeletal series from South Asia and elsewhere support the hypothesis that muscular-skeletal robusticity was a significant physical adaptation of earlier hunting-foraging populations. A trend towards reduction of sexual dimorphism and development of more gracile body form and smaller teeth appears to have accelerated with the socioeconomic transition to food-production strategies involving agriculture and pastoralism and refinement of technologies for food procurement and preparation, as documented by morphometric studies of later prehistoric inhabitants of South Asia.

Anthropometry↗
PubMed1987

Comparative study of mesiodistal crown diameters and arch dimensions between indigenous British and Pakistani immigrant populations.

Over the last two decades, the United Kingdom has seen an increase in the number of immigrants from the Indian subcontinent, mainly Pakistan. The amount of information that is available regarding parameters such as mesiodistal crown diameters and dental arch dimensions is, however, somewhat limited for this population. An investigation was carried out to compare corresponding mesiodistal crown diameters and arch dimensions between samples of the indigenous British population in Leeds (England) and the Pakistani immigrant population living in Rochdale (England). Measurements were taken from dental casts. The results showed that there were no significant differences between the two ethnic groups in corresponding mesiodistal crown diameters or arch dimensions. Data are provided for the Pakistani immigrant population in Britain.

Adolescent↗
PubMed1988

A principal components analysis of human odontometrics.

It has long been recognized that tooth crown diameters in hominoids are all positively intercorrelated one with another. This study reports on sex-specific correlation matrices derived from 2,650 individuals from the Solomon Islands, Melanesia. Mesiodistal and buccolingual diameters of all permanent teeth from one side are used, excluding third molars. Analysis discloses significant sex dimorphism in the strengths of the intercorrelations, with females being better integrated. Principal components analysis (PCA) provides an objective means of data reduction (shown here to be preferable to simple size summation methods) and decorrelation of the resulting linear combinations. Four components are extracted (with results being virtually identical in the two sexes) and arguments are put forth that varimax rotation to "a simpler solution" may be counterproductive. Before rotation, the four components are 1) overall size, 2) buccolingual widths contrasted with mesiodistal lengths, 3) anterior (I,C) contrasted with posterior (P,M) teeth, and 4) premolars contrasted with molars. Most of the explained (shared) variance (63%) extracted by PCA is in overall size of the dentition. There is a strong urge to view the results of these principal components analyses as reflective of biologically and genetically meaningful entities.

Female↗
PubMed1989

Small tooth sizes in a nineteenth century South Carolina plantation slave series.

Sub-Saharan African (and derived) populations typically exhibit larger mean tooth crown diameters than whites in spite of considerable population variability. We report on a 19th century series of American black slaves from a single cemetery near Charleston, South Carolina, that possessed notably smaller crown sizes. Analysis identifies a characteristic set of differences compared to caucasians, including retention of large maxillary lateral incisors and disproportionately large premolars and molars. Regression of principal components scores (derived from the mesiodistal diameters) on the sum of all diameters (used here as a measure of overall tooth mass) confirms a basic ethnic difference between black and white odontometrics: significantly more of the tooth mass is apportioned to the cheek teeth (premolars, molars) in blacks than whites. The difference (expressed as residuals from linear regression on tooth mass) holds for the several groups assessed here despite considerable intergroup variability in tooth sizes. Potential explanations for the notably small diameters of this plantation series are speculative, but may involve kin-based divergences and/or reflect the natural intergroup differences extant in the African slave sources.

Adult↗
PubMed1989

Allocation and discrimination based on human odontometric data.

This study contrasts the confidence with which individuals may be grouped and then re-allocated on the basis of odontometric data. These data are derived from the mesiodistal and buccolingual diameters of 202 Lengua Indians of Paraguay (100 males, 102 females), 125 Caucasoid schoolchildren (59 male, 66 female), and 206 Negroes (106 male, 100 female). Multivariate intergroup discrimination is effected by means of canonical and stepwise discriminant analysis, whilst allocation is evaluated by means of posterior and typicality probabilities. Bias is reduced by means of a jackknifing procedure. High levels of discriminatory confidence (each Wilk's Lambda, P less than 0.01) are matched by high percentage correct classification (Caucasoid, 67.4-75.0%; Negro, 71.0-77.3%; Amerindian, 65.2-78.1%). However, these results are not matched by allocatory procedures: only 21.7% of caucasoids, 21.4% of Negroes, and 28.8% of Amerindians could be re-allocated with probabilities in excess of 80%. It is concluded that while multivariate discriminant techniques may be usefully employed in the separation of different populations, individuals may not be assigned with the same degree of confidence, even with an a priori knowledge of their group membership.

Analysis of Variance↗