Doctoral Dissertation Research: Weaned Age Variation and Trace Element Distributions in Primate Teeth

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For our human ancestors, a shift toward earlier age at weaning may have contributed to higher reproductive success and population growth. However, the evolutionary context of this adaptive shift is not fully understood, in part because of methodological constraints in obtaining evidence of weaning from the fossil record. This doctoral dissertation project will analyze chemical signatures preserved in the teeth of wild mountain gorillas to determine how those signatures may be related to weaning and socioecological factors. Findings from this project could then serve as a foundation for applying this approach to the human fossil record. This project will include scientific training and mentorship of students, including individuals from groups underrepresented in STEM fields. It will also bolster research collaborations, support public science outreach and education, and inform ongoing primate conservation efforts. The investigators will test a developing method for reconstructing the timing of early-life dietary transitions from the distribution of calcium-normalized strontium and barium intensities in teeth, and to investigate weaning age variation within a single well-documented wild population of Virunga mountain gorillas from Volcanoes National Park in Rwanda. The chemical signature of mountain gorilla food resources will be characterized in order to provide a context for interpreting variation in enamel and dentine barium and strontium intensities. Estimated weaned age from trace element analysis will then be compared to longitudinal records on wild mountain gorilla diet and suckling. The following questions will be addressed: 1) How well do trace element distributions in teeth correspond to behavioral observations of suckling and other metrics for determining weaning age (e.g., interbirth interval)? and 2) How does the weaning chemical signature vary within a wild mountain gorilla population? The ability to partner behavioral and chemical data from individuals in this population represents a unique opportunity to test an emerging methodology for recovering relatively high resolution evidence of weaning in the human fossil record.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.