D. Troy Case

Sex Determination from Hand and Foot Bone Lengths

ABSTRACT: Numerous studies have addressed sex estimation from the hands and feet with varying results. These studies have utilized multiple measurements to determine sex from the hands and feet, including measures of robusticity (e.g., base width and midshaft diameter). However, robusticity measurements are affected by activity, which can disguise underlying patterns of sexual dimorphism. The purpose of this study is to investigate the utility of length measurements of the hands and feet to estimate sex. The sample consists of white females (n=123) and males (n=136) from the Terry Collection. Discriminant function analysis was used to classify individuals by sex. The left hand outperformed both the right hand and foot producing correct classification rates exceeding 80%. Surprisingly, the phalanges were better sex discriminators than either the metacarpals or metatarsals. This study suggests that length measures are more appropriate than robusticity measures for sex estimation.

Os intermetatarseum: A heritable accessory bone of the human foot

The os intermetatarseum is a relatively common accessory bone of the human foot located at the tarsometatarsal border between the first and second metatarsals. It can occur as an independent ossicle or as an osseous spur projecting from the proximal ends of the first two metatarsals, or the distal end of the first cuneiform. To determine the frequency of this congenital defect in native North American groups and East Asians from Japan, the skeletons of 846 Native Americans and 125 modern Japanese and Ainu were examined for the presence of the os intermetatarseum. The North American skeletons are from archaeological sites in various parts of Canada and the United States, including the Arctic coast, the Subarctic, the Aleutian Islands, the Northern Plains, the Illinois River area, and the Southwest. Overall frequencies ranged from no occurrence among the Arctic samples to 8% of individuals from Pecos Pueblo. Second metatarsal spurs occurred in particularly high frequencies among American Indians, whereas the East Asians were only found to have os intermetatarseums associated with the first cuneiform. Because pedigrees have shown the os intermetatarseum to be an inherited defect, its high frequency among some Native Americans may be due, in part, to a higher degree of genetic relatedness among the individuals in the North American samples than among the relatively modern East Asians.

Sexual Dimorphism in the Tarsal Bones: Implications for Sex Determination

Abstract:  An accurate determination of sex is essential in the identification of human remains in a forensic context. Measurements of some of the tarsals have been shown to be sexually dimorphic by previous researchers. The purpose of the present study is to determine which dimensions of the seven tarsals demonstrate the greatest sexual dimorphism and therefore have the most potential for accurate sex determination. Eighteen measurements of length, width, and height were obtained from the tarsals of 160 European‐American males and females from the William M. Bass Donated Skeletal Collection. These measurements were made using a mini‐osteometric board. Logistic regression analyses were performed to create equations for sex discrimination. All measurements showed significant sexual dimorphism, with the talus, cuboid, and cuneiform I producing allocation accuracies of between 88 and 92%. Combinations of measurements provided better accuracy (88.1–93.6%) than individual measurements (80.0–88.0%).

Determination of sex from the metacarpals in a Thai population

Determination of sex using metacarpals was carried out on a sample of 249 skeletons from a Thai population (154 males and 95 females), ranging in age from 19 to 93 years. Six measurements were taken on each metacarpal, namely maximum length, medio-lateral base width, antero-posterior base height, medio-lateral head width, antero-posterior head height and mid-shaft diameter. Binary logistic regression equations were calculated for determining sex from these measurements. All metacarpals from both sides produced at least one equation that correctly allocated the skeletons with 80% or greater accuracy. In a comparative test using only individuals with no missing measurements (n=196), the most accurate equations for each metacarpal on the right side had pooled allocation accuracies ranging from 85.2% to 89.3%, with the best equation based on three measurements from the 5th metacarpal. On the left side, the most accurate equations for each metacarpal ranged from 83.2% to 89.8% correct allocation, with the best equation based on three measurements of the 2nd metacarpal. When the allocation accuracy for each sex is considered in addition to the pooled accuracy, the best equations involve the same three measurements of the 5th metacarpal on the right side, but shift to three measurements of the first metacarpal on the left side, with a pooled accuracy of 88.3%. The results of this study suggest that metacarpals can be used quite reliably for sexing in forensic contexts in Thailand.

Dermatoglyphics from All Chinese Ethnic Groups Reveal Geographic Patterning

Completion of a survey of dermatoglyphic variables for all ethnic groups in an ethnically diverse country like China is a huge research project, and an achievement that anthropological and dermatoglyphic scholars in the country could once only dream of. However, through the endeavors of scientists in China over the last 30 years, the dream has become reality. This paper reports the results of a comprehensive analysis of dermatoglyphics from all ethnic groups in China. Using cluster analysis and principal component analysis of dermatoglyphics, it has been found that Chinese populations can be generally divided into a southern group and a northern group. Furthermore, there has been considerable debate about the origins of many Chinese populations and about proper assignment of these peoples to larger ethnic groups. In this paper, we suggest that dermatoglyphic data can inform these debates by helping to classify a Chinese population as a northern or southern group, using selected reference populations and quantitative methods. This study is the first to assemble and investigate dermatoglyphics from all 56 Chinese ethnic groups. It is fortunate that data on population dermatoglyphics, a field of physical anthropology, have now been collected for all 56 Chinese ethnic groups, because intermarriage between individuals from different Chinese ethnic groups occurs more frequently in recent times, making population dermatoglyphic research an ever more challenging field of inquiry.

Articular surface defects in the third metatarsal and third cuneiform: nonosseous tarsal coalition.

Frequencies of articular surface defects on the third metatarsal and third cuneiform, seen as pits of varying sizes on the plantar one third of the tarsometatarsal articular face, were investigated in skeletal populations from North America and Japan, as well as in gibbon, orangutan, chimpanzee, and gorilla skeletons. The apes did not exhibit the defects, although the number of observed specimens of each type was small. The newly presented human frequencies corresponded well with those from other published sources. The defects appeared both unilaterally and bilaterally, with no apparent sex or side biases. Statistical tests between the various populations found that, in general, geographically close populations had more similar frequencies of the defect. Possible etiologies for the defect were investigated, including biomechanical influences, degenerative arthritis, infection, trauma, and a developmental condition known as tarsal coalition, which proved to be the best explanation. Tarsal coalition results from the failure of a joint space to form properly during fetal growth. It can occur between any two adjacent bones of the foot. Several clinically important coalitions, whose presence interferes with normal walking, are known. However, coalition between the third metatarsal and third cuneiform has not been reported in the clinical literature, suggesting that the defect causes little or no foot dysfunction. Tarsal coalition is thought to have a strong genetic component, suggesting that the pit defect may be useful as a skeletal nonmetric trait, as others have stated.

Evidence of Prehistoric Scalping at Vosberg, Central Arizona

Four crania recovered during the 1970 Arizona State University field school season at a prehistoric site in Vosberg, Arizona show parallel clusters of cut marks characteristic of scalping with a stone knife. These victims were identified during a general survey of the Vosberg skeletons for evidence of trauma and pathology. The discovery of these four victims in the same atypical burial context provides clues to the nature of the scalping custom in the American Southwest prior to European contact and brings the total number of prehistoric scalping victims reported from the Southwest to 15 individuals. Perimortem depressed fractures in two of the crania, and the presence of a stone arrow point within the chest of one of the skeletons, indicates that the scalping of these individuals was the result of violence rather than medicinal or ritual treatment.

Sex estimation from the talus in a Thai population

Previous research on sex estimation from the tarsals has shown that the talus is the most sexually dimorphic tarsal bone in most populations. In order to assess the sexing potential of the talus in a Thai population, 252 skeletons (126 male, 126 female) from the Chiang Mai University Skeletal Collection were measured. The sample represents Thai people who come from the local Chiang Mai area and who died within the past ten years. Ten measurements were taken on the left and right tali from each skeleton. Seven of these measurements are similar, or identical, to measurements used by other researchers. Three experimental measurements were also taken. Logistic regression equations were calculated for each measurement, and for pairs of measurements. The individual measurements were also examined using ROC analysis. Averaging the results from both sides, the individual measurements with the highest correct allocation accuracies based on logistic regression analysis were trochlear length (88.2%), trochlear breadth (87.3%), talar length (85.5%), and inferior articular surface length (84.5%). The ROC results followed a similar pattern, with Area Under the Curve values as follows: trochlear length (0.952), inferior articular surface length (0.937), trochlear breadth (0.935), and talar length (0.914). When pairs of measurements were considered by means of logistic regression, four equations produced predicted allocation accuracies greater than 90% - three from the right talus, and one from the left. The highest accuracy on both sides resulted from a combination of the two most sexually dimorphic individual measurements of trochlear length and trochlear breadth. Together, they produced predicted allocation accuracies of 91.3% on the right side, and 91.4% on the left side. Unlike many past studies that have found talar length to be the most sexually dimorphic measurement of the talus, our study found trochlear length and breadth to be the most accurate measurements for distinguishing the sexes. Researchers developing sexing equations for use with other populations should consider including trochlear length and breadth in their analyses.

Determination of sex from the proximal hand phalanges in a Thai population

A sample of 249 skeletons (154 males, 95 females) from the Chiang Mai University Skeletal Collection was studied to investigate the potential of proximal hand phalanges as indicators of sex among individuals from the Chiang Mai province of Thailand. The sample ranged in age from 19 to 93 years. Six measurements were taken on each proximal phalanx: maximum length, medio-lateral base width, antero-posterior base height, medio-lateral head width, antero-posterior head height and maximum mid-shaft diameter. The measurements were then subjected to ROC analysis as well as binary logistic regression to assess the relative correct allocation accuracy for each bone, and for different combinations of measurements from each bone. All proximal phalanges from both sides exhibited greater than 87% correct allocation accuracy for at least one logistic regression equation that included only two or three measurements. When the sample was limited to individuals with no missing measurements (n=209) in any of the phalanges, the most accurate equations for each proximal phalanx ranged from 87.6% to 92.3%, with the most accurate equation based on two measurements from the left 1st proximal phalanx, and the next most accurate from three measurements of the left 2nd proximal phalanx. The results suggest that proximal phalanges produce better allocation accuracies than metacarpals among modern individuals from Thailand.

The Evolutionary Origin and Population History of the Grauer Gorilla

Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; ∼28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas-which currently occupy a geographic range more than ten times the size of that of mountain gorillas-imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeographical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction.