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• Paige Williamson

Paige Williamson

Advisor: Maja Å eÅ¡elj

Fluctuating Dental Asymmetry and Great Ape Development

Fluctuating asymmetry (FA), which refers to differences in shape and/or size between the left and right side of the body, is an indicator of developmental instability and stress. While the body is still growing, conditions that require energy conservation (e.g., food scarcity, disease) usually manifest as a slowing down or interruption of growth across different tissues, to conserve limited resources for the most essential bodily processes. FA research in humans and non-human primates has primarily focused on the skeleton. In the dentition, more attention has been paid to defects known as linear enamel hypoplasia (LEH), which also correspond to periods of stress. Some research has detected fluctuating asymmetry in tooth size, however, no one has looked at perikymata, which are enamel growth increments visible on the tooth’s surface, and thus a constituent part of final tooth crown size.

Continuing the work started by Levi Raskin in his 2023 SSR project, and using a 3D scanned great ape skull sample from the Field Museum of Natural History, we will examine whether there is fluctuating asymmetry in perikymata counts and tooth crown diameters, and how it correlates with LEH. The scanned sample consists of 13 orangutans, 12 gorillas, 7 common chimpanzees and one bonobo, with 269 teeth cast. We will focus on permanent incisors and canines for which we have antimeres. The results will show whether FA in tooth size, if any, is correlated with LEH. Where perikymata counts for matching segments of crown height are available, the presence or absence of FA would indicate whether those differences are achieved through differential duration or rates of enamel secretion, respectively.