Trabecular architecture in the thumb of Pan and Homo: implications for investigating hand use, loading, and hand preference in the fossil record.

Objectives: Humans display an 85-95% cross-cultural right-hand bias in skilled tasks, which is considered a derived behavior because such a high frequency is not reported in wild non-human primates. Handedness is generally considered to be an evolutionary byproduct of selection for manual dexterity and augmented visuo-cognitive capabilities within the context of complex stone tool manufacture/use. Testing this hypothesis requires an understanding of when appreciable levels of right dominant behavior entered the fossil record.

Cortical bone mass and geometry: age, sex, and intraskeletal variation in nineteenth-century Euro-Canadians.

Objectives: This study seeks to understand the interaction of cortical bone strength and mass within individuals and across age-groups in male and female adults from a relatively active, long-lived nineteenth-century Euro-Canadian population.

Methods: Strength and relative cortical area are measured in paired femora (weight-bearing elements) and metacarpals (manipulative elements) from 139 adults (M = 82; F = 52). Sex and age patterns are tested using linear multiple regression and analysis of covariance.

Scaling VOI size in 3D μCT studies of trabecular bone: a test of the over-sampling hypothesis.

For comparative 3D microCT studies of trabecular bone, the use of a volume of interest (VOI) scaled to body size may avoid over-sampling the trabecular mass in smaller versus larger-bodied taxa and comparison of regions that are not functionally homologous (Fajardo and Müller: Am J Phys Anthropol 115 (2001) 327-336), though the influence on quantitative analyses using scaled versus nonscaled VOIs remains poorly characterized. We compare trabecular architectural properties reflecting mass, organization, and orientation from three volumes of interest (large, scaled, and small) obtained from the distal first metacarpal in a sample of Homo (n = 10) and Pan (n = 12). We test the null hypotheses that neither absolute VOI size, nor scaling of the VOI to metacarpal size as a proxy for body size, biases intraspecific analyses nor impacts the detection of interspecific differences.

Metacarpal trabecular architecture variation in the chimpanzee (Pan troglodytes): Evidence for locomotion and tool-use?

Trabecular architecture was assessed by 3D micro-computed tomography from spherical volumes of interest located within the head and base of metacarpals (MC) 1, 2, and 5 from n = 19 adult common chimpanzees. Two subspecies, West African Pan troglodytes verus from the Taï Forest, Côte d'Ivoire (n = 12) and Central African P. t.

A three-dimensional microcomputed tomographic study of site-specific variation in trabecular microarchitecture in the human second metacarpal.

Variation in trabecular microarchitecture is widely accepted as being regulated by both functional (mechanical loading) and genetic parameters, although the relative influence of each is unclear. Studies reporting inter-site differences in trabecular morphology (volume, number and structure) reveal a complex interaction at the gene-environment interface. We report inter- and intra-site variation in trabecular anatomy using a novel model of contralateral (left vs right) and ipsilateral (head vs base) comparisons for the human second metacarpal in a sample of n = 29 historically known 19th century EuroCanadians.

Articular constraint, handedness, and directional asymmetry in the human second metacarpal.

The hypothesis that functional adaptation of joint surfaces to mechanical loading occurs primarily through change in mass, density, and structure of subarticular trabeculae (the "articular constraint" model) is investigated through an analysis of directional asymmetry among three separate bone compartments in the human second metacarpal. Measures of midshaft cross-sectional geometry, osteometry of the distal epiphysis, and subarticular trabecular microarchitecture of the distal epiphysis (assessed by high-resolution microcomputed tomography) were determined for 29 paired male and female metacarpals from a well-preserved nineteenth-century Euro-Canadian historic cemetery sample. For each measure, asymmetry was quantified using both mean-difference and confidence-interval methods.

Population variation in second metacarpal sexual size dimorphism.

This paper contrasts levels of sexual size dimorphism in second metacarpal osteometric and geometric morphology in two bioculturally distinctive populations: 19th century Euro-Canadian settlers, and proto/historic central Canadian Inuit. Significant within-group sexual size dimorphism is found for all variables, though few show significant interpopulation differences. However, in every case the Euro-Canadian sample is more dimorphic than the Inuit sample.

Circumferential variation in human second metacarpal cortical thickness: sex, age, and mechanical factors.

Variation in cortical thickness (CT) in four quadrants of the human second metacarpal was investigated in a sample (100 males and 72 females, skeletal age 20 to 50+ years) from a 19th-century cemetery. Both left and right elements were studied (total N = 344). Multivariate analysis of covariance (MANCOVA) (for age, sex, and side, controlling for absolute size) was used to test the hypothesis of equality of thickness in the dorsal, palmar, medial, and lateral quadrants.

Prediction of cross-sectional geometry from metacarpal radiogrammetry: a validation study.

Regression models have been developed to adjust algebraic estimates of second metacarpal cortical bone geometry to actual values (as determined through invasive analysis). These models, derived from an archaeological sample of European origin, have high efficacy in predicting actual values but have not been validated on non-European samples. This paper reports a validation study for these models applied to a historic/proto-historic sample of Inuit from the central Canadian Arctic (n = 166; ages and sexes pooled as per the original study).

Second metacarpal cross-sectional geometry: Rehabilitating a circular argument.

Radiogrammetry of the second metacarpal has long served as a measure of normal and abnormal bone growth and aging, functional asymmetry, and fracture risk in osteoporosis. The method relies on algebraic interpretation (circular or elliptical models) of uni- or biplanar radiographic images. This paper tests the conformance of these models with actual measures of metacarpal geometric variation in a sample of 356 bones from an historic archaeological sample.

Bone loss, traditional diet, and cold adaptation in Arctic populations.

North American Inuit and Inupiat ("Eskimo") populations have been described as having a lower bone mass relative to Caucasians as a consequence of their traditional high-protein "acid-ash" diet. However, this bone buffering mechanism has also been implicated as a risk factor for osteoporosis in industrialized Caucasian populations, and one recent study has found a positive association between dietary protein, and bone mass in premenopausal women. The original studies documenting the Eskimo-Caucasian difference in aging bone loss do not consider the consequences of population variation in body composition, in particular lean body mass (LBM), which correlates with bone mass.