Don’t Sweat the Small Stuff–Examining Dental Evidence of Stress in a Gombe Chimpanzee (Pan troglodytes schweinfurthii)
Open AccessSimilar to trees forming rings as they grow, teeth record the passage of time through the deposition of enamel in microscopic layers that permanently document the cadence of daily and longer-period growth rhythms (Bromage & Dean 1985, Bowman 1991). When examined histologically, these layers can be used to establish an absolute chronology of development (Bowman 1991, Lemmers et al. 2021, Smith 2008). Additionally, it is hypothesized that physiologically stressful life events can be observed as atypical lines that record disturbances of the tooth’s normal secretory cell activity (Bowman 1991, Dirks et al. 2002, Lemmers et al. 2021, Smith 2008, Witzel et al. 2008). These disruptions in enamel matrix secretion can be observed internally within the enamel, as accentuated incremental lines (Smith 2008, Witzel et al. 2008). This thesis evaluates the hypothesis that stress events impact dental development by analyzing the teeth of an individually known female chimpanzee (Pan troglodytes schweinfurthii), Sherehe, from Gombe Stream National Park, Tanzania. I integrate long-term behavioral and health observations of this individual with investigation of dental histology from her naturally accumulated skeleton, to determine the chronology and severity of stress-related impacts on early life development. The specific aim of this study was to document the chronology of accentuated lines in the first molar, canine, and third molar and test whether their timing coincided within +/- 4 days of documented life history events that I expect to be stressful. The results of this study revealed six documented behavioral events that coincided with accentuated lines. This included the only documented behavioral event related to the process of weaning, and the only two documented events related to hunting behaviors. However, the majority of recorded behavioral events were categorized as aggression and, with the exception of three such events, did not correspond to accentuated lines in this individual, suggesting that many aggressive interactions may not contribute to stress severe enough to impact enamel formation. Further investigation is necessary to reveal more about the complexity of these disturbances in enamel development, but this study offers a careful examination of one individual chimpanzee to deepen our understanding of stressors that can be observed as accentuated lines in the teeth.
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Hillegas_gwu_0075M_16407.pdf | 2023-11-14 | Open Access |
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