Current Project
A multi-proxy study of weaning variation in wild apes
A key feature of human life history evolution, modern humans wean their infants ~2-3 years earlier on average compared to our closest living relatives. However, the evolutionary origins of early weaning in modern humans remain elusive. To address this problem, we initiated a collaborative and interdisciplinary research program that spans three of the world’s longest-term great ape study sites – Gombe chimpanzees, Virunga mountain gorillas, and Bwindi mountain gorillas. This research integrates data on suckling and feeding behavior, physical development, and fecal stable isotopes collected from individuals in life, and chemical characterization of their foods, with morphological and dental trace element analyses of associated skeletons from these populations and individuals after death. Specifically, we examine three questions. What factors influence variability in dietary transitions associated with weaning across living wild chimpanzees and gorillas? How do chemical proxies of weaning in biological tissues relate to behavioral and anatomical proxies of weaning? Finally, how reliably does variability in dental trace elements correspond to documented dietary histories at both the individual and population levels?
Bwindi mountain gorilla mother and infant, Nyakina and Musana. Photo courtesy of Dr. Martha Robbins.
These taxonomically and ecologically distinct ape populations offer unparalleled opportunities to better understand factors influencing variation in the weaning process in our closest living relatives. Further, by better understanding the reliability of proposed hard tissue proxies for reconstructing weaning in past contexts, this work will contribute towards a foundation for examining life history variation through time within these endangered great ape populations, and yield results of relevance for interpreting the fossil evidence of human life history evolution.
This NSF-funded research is a collaboration with the Dian Fossey Gorilla Fund International in Rwanda, the Bwindi Gorilla Project of the Max Planck Institute for Evolutionary Anthropology in Uganda, Franklin & Marshall College (Dr. E. Lonsdorf), The George Washington University (Dr. C. Murray), Arizona State University (Dr. I. Gilby), the Jane Goodall Institute and their collaborators in Tanzania, and partners in the USA including the Smithsonian Institution (Dr. M. Power, Dr. C. France) and New York University College of Dentistry (Dr. T. Bromage). This project is also supported by collaborations with national parks authorities and other partner institutions in these countries.
PhD student Meagan Vakiener, conducting research on Virunga mountain gorilla dental and plant food trace elements as part of her dissertation research.