Preferential expression of linear enamel hypoplasia on the sectorial premolars of rhesus monkeys (Macaca mulatta)

Abstract

Three hundred and sixty rhesus macaque specimens at the Caribbean Primate Research Center were examined for evidence of linear enamel hypoplasia (LEH). A previously unreported intertooth pattern in LEH was observed. Defects occur preferentially on the sectorial premolar of both males and females. Relative to other teeth, the sectorial premolar exhibits more prominent defects and is more likely to exhibit multiple defects. This pattern is unlike the human intertooth LEH pattern and unlike patterns previously reported for monkeys and apes. These observations are discussed in the context of factors thought to influence the intertooth distribution of LEH in humans and in nonhuman primates. The authors reject crown height, the timing of crown development, and the duration of crown formation as factors contributing to the observed pattern and favor an explanation involving enamel thickness, perikymata spacing, and/or prism orientation.

Interpreting sex differences in enamel hypoplasia in human and non-human primates: Developmental, environmental, and cultural considerations

“…The higher frequencies of LEH in female versus male rhesus monkeys (Guatelli-Steinberg and , based on matching LEH defects on any antimeric pair, reflects the fact that male lower P3s are affected by heavier wear than those of females. The wear differential combined with the fact that the lower P3 is preferentially affected by LEH in this sample (Guatelli-Steinberg and Lukacs, 1998), results in a higher female incidence of LEH relative to males. The sex difference in LEH incidence is not apparent when individuals with worn lower P3s are removed from the analysis.…”

“…EH incidence. Statistically significant differences in the incidence of EH are evident in two of the eight studies (Guatelli-Steinberg and Lukacs, 1998;Newell, 1998). The higher frequencies of LEH in female versus male rhesus monkeys (Guatelli-Steinberg and , based on matching LEH defects on any antimeric pair, reflects the fact that male lower P3s are affected by heavier wear than those of females.…”

“…Relative to the number and diversity of EH studies conducted in humans, the literature on EH in non-human primates is sparse. Colyer published initial findings on non-human primate EH in 1936; however, extensive research on this topic did not begin until the mid 1980s (Eckhardt, 1992;Eckhardt et al, 1992;Eckhardt and Protsch von Zieten, 1993;Guatelli-Steinberg, 1998;Guatelli-Steinberg and Lukacs, 1998;Lukacs, 1999b (in review); Crovella, 1991, 1992;Newell, 1998;Skinner, 1986b;Skinner et al, 1995;Skinner and Guatelli-Steinberg, 1997;Stottlemire, 1998;Vitzthum andWikander, 1988, Zhang, 1987). Twenty studies reporting EH frequencies were examined for information regarding sex differences.…”

“…Within primate populations, there appears to be variation in sexbiased parental investment related to the dominance rank of mothers (Hrdy, 1987); however, none of these eight studies addresses this issue with behavioral data. Indications of stress other than EH are also not included in these studies, although minimal stress can be inferred in the provisioned Cayo Santiago rhesus population (Guatelli-Steinberg and Lukacs, 1998) and potential sources of disease have been identified for African ape samples (Skinner, 1986;Skinner et al 1995).…”

“…In Al-Abassi's (1997) study, it seems that there is a cultural preference for daughters. Two studies in humans (Lukacs and Pal, 1993;Douglas et al, 1997) and two studies in non-human primates (Guatelli-Steinberg and Lukacs, 1998;Newell, 1998) involve statistically significantly higher expression of EH in females than males (although for Guatelli-Steinberg and , this difference is not biologically significant as it results from a wear differential).…”