American Journal of Biological Anthropology最新文献

Objectives: We evaluated the effects of four treatments for pathogen inactivation in bone tissue (ethanol storage, formalin fixation, gamma irradiation, and heat treatment via autoclave) on stiffness and anisotropy values in bone samples.

Materials and methods: Cortical bone samples from the humerus of 14 bovine specimens were subjected to Knoop microindentation analysis in longitudinal and transverse planes of section and four indenter orientations within each section. From each specimen, individual samples were assigned to one of five treatment conditions: 50% ethanol-saline solution, formalin immersion, gamma irradiation, autoclave, and buffered saline (controls). Each sample was microindented 100 times and the resultant stiffness data were analyzed by a resampled factorial analysis of variance.

Results: First- and second-order interactions as well as main effects of indenter orientation, treatment, and specimen were significant for both transverse and longitudinal sections, with the sole exception that indenter orientation-treatment interaction was nonsignificant for longitudinal sections. Interaction plots reveal that thermal (autoclave) and irradiation treatments depress stiffness values the most, while patterns of indentation stiffness at different orientations are relatively unaffected.

Discussion: Patterns of anisotropy are relatively unaffected by preservative treatments, but elastic modulus changes are consistent and unambiguous. Formalin and ethanol treatments are most comparable to controls and represent the best preservative media for mechanical testing. These options, however, are likely to be the least effective for ensuring the inactivation or sterilization of potentially contaminated samples.

Objectives: Facial width-to-height ratio (fWHR) has been widely investigated in the context of its role in visual communication, though there is a lack of consensus about how fWHR serves as a social signal. To better understand fWHR variation in a comparative context, we investigate the associations between fWHR and canine crown height (CCH) and body mass, respectively, among two chimpanzee subspecies (Pan troglodytes schweinfurthii, Pan troglodytes troglodytes) and bonobos (Pan paniscus).

Materials and methods: We collected landmark data from 3D surface models of 86 Pan cranial specimens to quantify fWHR and upper CCH, and to estimate body mass. We used Spearman's r and Kruskal-Wallis tests to test for significant relationships among variables, and to assess sexual dimorphism.

Results: There is an inverse relationship between fWHR and CCH in both sexes of Pan, however there are interpopulation differences in the relationship between fWHR and CCH among Pan taxa. Pan paniscus have relatively wide faces and small canine crowns, and wide faces in Pan t. schweinfurthii males may be driven by body size constraints. Pan troglodytes and Pan paniscus show fWHR dimorphism, and Pan paniscus have significantly higher fWHRs than do either Pan troglodytes subspecies.

Discussion: Our findings indicate that CCH and facial breadth may serve subtly different signaling functions among Pan taxa. Further research into the circumstances in which wide faces evolved among chimpanzees and bonobos will likely afford deeper insights into the function of relatively wide faces in the context of visual signaling among humans and our extinct hominin relatives.

Objectives: Socioeconomic status, past stress events, and other factors may contribute to the cumulative burden of physiological stress, which influences an individual's susceptibility to mortality and cause of death (COD). Here, we explore the association between skeletal evidence of stress and COD in the Hamann-Todd Osteological Collection (HTOC), a predominantly low socioeconomic status sample from the late 19th and early 20th century.

Materials and methods: Skeletal markers of stress including linear enamel hypoplasia (LEH), stature, and antemortem tooth loss (AMTL) were analyzed in 298 individuals in the HTOC. Recorded CODs were grouped into six broad categories and contrasted with stress indicators, ages-at-death, and demographic variables, using various parametric and non-parametric statistical tests.

Results: COD varied by socially ascribed race and sex within the sample. Overall, infectious diseases were more prevalent than degenerative diseases. Individuals that died of infectious diseases had significantly lower ages-at-death compared to degenerative diseases (p < 0.001). There was no association between LEH and COD (χ² = 4.449, p = 0.487). Stature varied significantly across COD categories for males (F = 2.534, p = 0.032), but not females (F = 1.733, p = 0.132). Controlling for age-at-death, AMTL prevalence was associated with COD (H = 18.53, p = 0.002), with cardiovascular disease being associated with higher prevalence of AMTL.

Discussion: These findings show that some skeletal stress indicators are associated with COD in the HTOC, but the causal pathways of these relationships are not clear. This study adds to growing bodies of literature exploring relationships between past stress events and susceptibility to mortality and long-term consequences of poor living conditions for past individuals.