No abstract

This study investigates changes in the prevalence of linear enamel hypoplasia (LEH) before and after the shift from irregular to regular provisioning in the Cayo Santiago rhesus monkey population. Prior to 1956, monkeys on this island colony did not receive consistent provisions, and were reported to be in poor health (Rawlins and Kessler [1986] The Cayo Santiago Macaques; Albany: State University of New York Press). A regular provisioning program, instituted in August 1956, resulted in the improved health of individuals and the growth of the population (Rawlins and Kessler [1986] The Cayo Santiago Macaques; Albany: State University of New York Press). LEH, a developmental defect of enamel, is a sensitive indicator of systemic physiological stress (Goodman and Rose [1990] Yrbk. Phys. Anthropol. 33:59-110). It was therefore hypothesized that the prevalence of LEH would be higher in monkeys who were irregularly provisioned than in monkeys who experienced regular provisioning. To test this hypothesis, teeth were examined for LEH in a sample of 181 female rhesus monkeys. The results support the hypothesis: the mean number of defects was statistically significantly higher in the preprovisioned group than it was in the postprovisioned one. When LEH prevalence was assessed using only defects occurring on antimeric pairs, the preprovisioned group again had a higher prevalence than the postprovisioned one, although the difference was not statistically significant, most likely because of the reduced sample size. The results of this study indicate that changes in LEH prevalence, at least in this population of rhesus monkeys, are associated with changes in nutritional status.

Fluctuating asymmetry (FA) represents non-directional deviations from perfect symmetry in morphological characters. Prenatal stressors contribute to the imprecise expression of symmetrical phenotypes and display of agonistic behavior in children and adults. Because prenatal stress affects neurological function and overt behavior, and FA is often used as a marker for prenatal stress, we hypothesized that high FA would be associated with elevated levels of human reactive aggression. Data were collected from 100 males and females (average age = 20.1) on FA of 11 bilateral traits (second, third, fourth, and fifth digit length, palm height, wrist diameter, elbow width, ear height, ear width, foot breadth, and ankle circumference). Additional relationships were also investigated among FA, testosterone (T), and type of provocation to test a comprehensive aggression model. Experimental participants solicited donations for a fictitious charity organization via telephone and selected follow-up letters after the calls. High FA and T values were independently associated with elevated reactive aggression (force of terminating the call) under low provocation in males, and under high provocation in females. In the absence of phenotypical markers, i.e., FA and T, sex differences in response to provocation disappeared and a "passive-aggressive" response emerged. Both males and females selected hostile follow-up letters, but showed low reactive aggression when terminating the call under high provocation. This pattern was reversed under low provocation. Taken together, these data suggest that individuals' phenotype and intensity of provocation are important determinants of individual and sex differences in aggression.

Fluctuating asymmetry (FA) represents random, minor deviations from perfect symmetry in paired traits. Because the development of the left and right sides of a paired trait is presumably controlled by an identical set of genetic instructions, these small imperfections are considered to reflect genetic and environmental perturbations experienced during ontogeny. The current paper aims to identify possible neuroendocrine mechanisms, namely the actions of steroid hormones that may impact the development of asymmetrical characters as a response to various stressors. In doing so, it provides a review of the published studies on the influences of glucocorticoids, androgens, and estrogens on FA and concomitant changes in other health and fitness indicators. It follows the premise that hormonal measures may provide direct, non-invasive indicators of how individuals cope with adverse life conditions, strengthening the associations between FA and health, fitness, and behavior.

No abstract