Molar enamel thickness is a key feature in the study of hominid evolution. Our understanding of enamel thickness and distribution patterns, however, has so far been based mostly on the limited information available from physical cross sections of the crown. In this study, the 3-dimensional (3D) whole crown enamel distribution pattern was explored in 74 extant great ape and modern human molars. Serial cross sections obtained from microfocal X-ray computed tomography were used to generate digital molar reconstructions at 50 to 80 micron voxel resolution, each crown represented by two to five million voxels. Surface data of both enamel dentine junction (EDJ) and outer enamel were extracted to derive volumetric measures, surface areas, curvilinear distances, and whole crown radial thickness maps. Three-dimensional average enamel thickness (AET) was defined as enamel volume divided by EDJ surface area. In 3D AET relative to tooth size, Homo exhibited the thickest, Gorilla the thinnest, and Pan and Pongo intermediately thick enamel. This result differs from previous claims that molar enamel of Pongo is relatively thicker than that of Pan. The discrepancy between three and two-dimensional (2D) values of AET stems from a combination of local differences in within tooth enamel distribution pattern and EDJ topography between Pan and Pongo molars. It demonstrates that 2D AET is not an appropriate substitute or estimator of whole crown AET. Examination of whole crown 3D distributions of molar enamel revealed a pattern common to all four examined species, the “functional” side of the molar having thicker enamel than the opposite side. However, some unique aspects of each species were also apparent. While the Gorilla molar has relatively thin enamel throughout its crown, Pan molars are characterized by particularly thin enamel in the occlusal fovea, and Pongo molars by an accentuation of relatively thin basal and thick occlusal enamel. Human molars are characterized by relatively thick enamel throughout the crown, with relatively large contrasts between buccal and lingual, and between mesial and distal crown portions. The ancestral condition common to the four extant species can be estimated by interpreting molar enamel distribution patterns unique to each genus as likely to be derived. We hypothesize that the last common ancestor likely had intermediately thick enamel, without particular thickening (or thinning) of enamel either occlusally or basally.

Molar enamel thickness and distribution patterns in extant great apes and humans: New insights based on a 3-dimensional whole crown perspective

Functional ecology and evolution of hominoid molar enamel thickness: Pan troglodytes schweinfurthii and Pongo pygmaeus wurmbii.

At least 29 species of fossil primates have been referred to fruit, nectar, and/or exudate feeding dietary niches. Many studies have detailed the morphological correlates of fruit feeding in comparison to insectivory and folivory. In contrast, few studies have sought to differentiate the morphological correlates of fruit feeding from those of nectar and exudate feeding. This study investigates the differences between fruit, nectar, and exudate feeders using 22 cranial and dentary shape variables representing 28 species of living marsupials, bats, and primates. Discriminant function analysis is used to investigate the differences between these dietary categories using both the complete data set and a reduced data set composed of variables that might reasonably be available from fragmentary fossil material. The success rates of post-hoc classifications are 94 and 88%, respectively. These results demonstrate that it is possible to discriminate among fruit, nectar, and exudate feeders among fossil taxa with a reasonable degree of certainty using the data and techniques outlined here. Nectar feeders exhibit a unique combination of features that are associated with reduced masticatory strength and their role as pollination agents. Exudate feeder skulls and dentaries exhibit a combination of features that reflect the high stresses encountered by the anterior dentition through bark gouging behavior. Fruit feeders are morphologically diverse, exhibiting cranial and mandibular shape values that overlap with both nectar and exudate feeders. It is suggested that this diversity reflects the variety of physical properties represented among fruits, and the tendency for individual frugivore species to specialize on particular fruits.

http://www.bio.umass.edu/biology/dumont/Dumont_1997_American%20Journal%20of%20Physical%20Anthropology.pdf

Cranial shape in fruit, nectar, and exudate feeders: Implications for interpreting the fossil record

Among 18 NIH probands with anosmia and hypogonadotropic hypogonadism (AHH), seven had affected relatives and three had consanguineous parents. Both sexes were equally affected and parents were phenotypically normal. Parental age was not increased. Cleft lip and palate occurred in both eugonadal and hypogonadal persons, a previously reported association that may represent variable expression of AHH. Diabetes mellitus, usually insulin-dependent, was frequent in probands and their families. Other common traits included obesity, cryptorchidism, and hearing loss. All probands were chromosomally normal. The frequency of some dermatoglyphic traits of probands differed from normal, but no trait was unique to AHH. Segregation analysis of our proband sibships was consistent with a hypothesis of autosomal-recessive inheritance with variable expression. However, genetic heterogeneity was apparent when previous reports of familial AHH were surveyed. An X-linked or male sex-limited autosomal-dominant form with unilateral renal agenesis, mental retardation, and hypotelorism has been observed. The infrequent reports of direct male-to-male transmission limit characterization of an autosomal-dominant form of AHH. Our phenotypic analysis suggests that the traits of mental retardation, renal anomalies, hypotelorism, diabetes, and hearing loss may help to distinguish various forms of AHH, whereas cryptorchidism, clefts, and obesity appear in several types of families. At present, genetic counseling is dependent upon establishing inheritance pattern after examination for the known associated anomalies.

The syndrome of anosmia with hypogonadotropic hypogonadism: A genetic study of 18 new families and a review

Variability of fingerprint ridge density in a sample of Spanish Caucasians and its application to sex determination

Digital and palmar dermatoglyphics were collected from 360 male and 360 female seven year old Caucasians from the greater Boston area. All participants were screened and found to be free of minor anomalies or chronic diseases. All individuals with I.Q. scores below 70 were also excluded. The results were presented in such a way as to give information on bilateral symmetry as well as overall frequencies of the various dermatoglyphic features. The results were compared with those of the corresponding sample of seven year old normal male and female Negrose of the accompanying report.



A review of the distribution of the dermatoglyphic features in different Caucasian populations has also been presented and the overall dermatoglyphics of the Caucasians were discussed in reference to the distribution of the same features in the other major “racial” groups.



The method of collection and selection of the subjects, described in the text, makes this set of data unique and one of the most suitable for use as controls in studying the dermatoglyphics of the individuals with diseases or congenital anomalies.

The dermatoglyphics of American Caucasians

Extract: In previous reports the subclassifications for the terminations of the G line of the palm and for the interdigital palmar areas have been described. These subclassifications, as well as those of Cummins and Midlo for the hypothenar and thenar/I areas, were applied to anthropologic data and showed strong bilateral and racial polymorphism. The present study is an effort to determine the usefulness of these methods in investigations of clinical data. A well defined anomaly, Down's syndrome, which has known dermatoglyphic peculiarities, was chosen for this test. The study involved 145 male and 120 female patients and 108 male and 114 female control subjects. All subjects were unrelated Caucasians. Significant differences between the patient and control subjects were encountered in the subclassifications of the C line terminations and in the hypothenar area patterns. Significant differences were observed in the frequency of patterns in the thenar/I area as well as the expected differences in the simial lines. Sydney line frequencies showed no significant differences. Speculation: The results of the present study suggest that the subclassifications of the palmar patterns and the G line terminations are of value in the investigation of clinical data by offering further diagnostic criteria not revealed by gross dermatoglyphic evaluation.

/pdf/palmar-dermatoglyphics-of-down-s-syndrome-revisited-459voa9mc0.pdf

Palmar Dermatoglyphics of Down's Syndrome: Revisited

Digital and palmar dermatoglyphics of 184 male and 224 female normal American Negroes were evaluated for digital patterns, digital ridge counts, palmar patterns, palmar main line terminations, accessory triradii and palmar creases. All subjects were seven year olds examined and found free of chronic or other genetic diseases. The results were presented for the left and right hand separately as well as in terms of bilateral symmetry. The present results were for the most part comparable to those of the African and other American Negro groups reported earlier. The distributions of the various dermatoglyphic features among the Negroes taken as a group were compared to those of the other racial groups and their differences were discussed.

Florence S. Steinberg

Papers

The dermatoglyphics of American Caucasians

Palmar Dermatoglyphics of Down's Syndrome: Revisited

The dermatoglyphics of American Negroes.