Analysis of correlations between measures of skeletal development and dental mineralization in Pan troglodytes.

OBJECTIVES: This study seeks to assess the relationship between dental mineralization and skeletal development in chimpanzees (Pan troglodytes) and to evaluate the effect that differing numbers of ordinal and continuous variables have on correlation statistics, particularly in comparison with prior human studies. MATERIALS AND METHODS: This study evaluated epiphyseal fusion, dental mineralization, and growth in length of long bones using 145 juvenile chimpanzee skeletons housed in osteological collections at the Powell-Cotton Museum, the Museum of Central Africa, and the Adolph Schultz Collection. RESULTS: Correlations between multiple epiphyseal fusion sites and dental maturity scores for crown and root mineralization were produced using Pearson's r, Spearman's ρ, and Kendall's τ. Correlation statistics were produced using different subgroups of epiphyseal fusion sites and long bone lengths, and both summary and individual tooth development scores. DISCUSSION: Methodological considerations were discussed as differences in sample, measurement scale, and statistical technique had an effect on the outcome of correlations obtained. These results suggest that sampling and methodological differences between studies may affect the interpretation and comparison of correlation results, and that correlation strength differences between extant species must be considered before applying such results to questions in human biology and palaeoanthropology. Even after consideration of such factors, the correlation coefficient values for chimpanzees obtained in this study were generally stronger than those previously published in human studies, and may reflect differences in skeletal and dental developmental patterns between species. Am J Phys Anthropol 158:279-287, 2015. © 2015 Wiley Periodicals, Inc.

Patella measurements of South African whites as sex assessors.

This study uses metrical characteristics of the patella to derive population specific equations for sex determination in South Africa. Six measurements were taken from 120 normal and undamaged left patellae in a sample of known race, equally distributed by sex, obtained from the Raymond A Dart collection of human skeletons. These data were subjected to discriminant analysis. Maximum height and maximum breadth were selected in the stepwise analysis with an average accuracy of 83% in correct sex classification. Four functions were derived from the direct analysis with a range of average accuracy between 77% and 85%. While most individual variables showed high misclassification rates and may not be useful on their own, maximum height and maximum breadth have an average accuracy of 85 and 79%, respectively.

Dental development in chimpanzees (Pan troglodytes): the timing of tooth calcification stages.

Data are presented documenting the timing of tooth calcification for the left mandibular dentition (I1-M3) based on a cross-sectional series of intraoral dental X-rays from a sample of 118 captive chimpanzees. Mean, median, and midpoint ages of attainment; standard deviations (SD); interquartile ranges (IQR); and age ranges were calculated for the eight developmental stages of these teeth. Minor differences with previous studies of chimpanzee dental development were found (Anemone et al. [1991] Am. J. Phys. Anthropol. 86:229-241; Anemone and Watts [1992] J. Hum. Evol. 22:149-153), but the similarities with previous studies are more striking despite the differences in samples. In contrast to other pongid studies, sex differences in developmental timing were documented, particularly for the canine. Regression models for age estimation from dental maturity scores were also presented. This chimpanzee standard is compared with human standards to determine absolute and relative differences in the timing of crown and root calcification. The overall period of canine development in both species is nearly identical, although those for crown and root formation are markedly different--making this tooth the most distinctive feature between chimpanzee and human dental development periods. Although the molars demonstrate differences in the timing of crown and root calcification periods, they are more proportional than for other teeth. This contributes to the difficulties in distinguishing between "human" and "chimpanzee" patterns of molar development. The developmental differences discussed are placed in perspective with consideration to microstructural and morphological features of chimpanzee and human teeth, and to overall growth periods in these species.

Permanent tooth calcification in chimpanzees (Pan troglodytes): patterns and polymorphisms.

Tooth calcification is an important developmental marker for use in constructing models for early hominid life history, particularly for its application to the fossil record. As chimpanzees are commonly utilized in interspecific comparisons in such research, this study aims to improve available baseline data for tooth calcification patterns in chimpanzees (Pan troglodytes), and to quantify basic patterns and polymorphisms. We present an analysis of developmental patterns for the left mandibular dentition (I1-M3) based on intraoral radiographs obtained from a cross-sectional sample of chimpanzees (58 males, 60 females) housed at LEMSIP (NYU Medical Center) and Yerkes (Emory University). No significant differences with previous descriptions of the basic sequences of tooth calcification in chimpanzees were found, but variation in such patterns was documented for the first time. In the overall sequence, polymorphisms between the canine and the group (M2 P4 P3) reached significant levels. This is due to the relative delay in canine crown formation compared to other teeth. Differences in the basic sequence between males and females were recorded, but are due to minor shifts in the percentages of occurrence for polymorphic sequences which are common to both genders. Perhaps our most important findings are that a) different polymorphic sequences occur in tooth calcification and tooth emergence in chimpanzees, and b) developmental relationships among teeth fluctuate throughout tooth calcification. Thus, characterizations of dental developmental patterns based on particular stages of development cannot necessarily be extrapolated to other stages without supporting data.

Probit and survival analysis of tooth emergence ages in a mixed-longitudinal sample of chimpanzees (Pan troglodytes).

Tooth emergence data from a mixed-longitudinal sample of 58 chimpanzees of known age were analyzed using probit and survival techniques to produce median emergence ages, ranges of variability, and emergence sequences for primary and permanent teeth. Between-group comparisons were made to test for statistically significant differences in emergence ages. No such differences were found between right and left sides, or between maxilla and mandible, for any primary or permanent teeth. Male-female comparisons did demonstrate significant emergence-age differences for some teeth, although they were not always bilaterally symmetrical. More complete data are required to further clarify the nature of sex differences in tooth emergence in chimpanzees. Regression models for age prediction from the number of emerged teeth were generated and indicate that males achieve a given number of emerged teeth at a significantly later age than females. However, when fewer than five teeth have emerged, males are predicted to be younger than females. The sizable root mean square error values for these models suggest that this method of age prediction has limited usefulness owing to the amount of variability in timing of tooth emergence in chimpanzees. The implications of these data for studies on tooth emergence in early hominids are addressed.