Sherry Nelson

Research

I am currently involved in a project to determine timing of weaning through isotopic analyses of urine from mother-infant chimpanzee pairs at Kibale National Park, Uganda. Weaning is a process whose timing is critical to understanding the energetic trade-offs of reproduction from the mother’s point of view, and the energetic requirements of morphological, cognitive, and behavioral development from the infant’s. Stable isotope analyses from mother-infant pairs will allow us to monitor infants’ weaning transitions from a diet of mother’s milk to solid foods.  We will then compare weaning schedules to timing of first molar (M1) eruption.  Weaning, M1 eruption, and near completion of brain growth have been heralded as some of the few isochronic relationships in primate life history, yet both humans and chimpanzees are exceptions to this rule.  Humans wean their infants long before first molar eruption. Chimpanzees, however, continue to breastfeed well after their offspring erupt first molars and complete most of their brain growth. By combining isotopic measurements of weaning, growth measurements in offspring, and energetic measurements of mothers, our study will be the first to address why chimpanzee mothers continue to nutritionally invest in offspring past brain growth.  Given the use of M1 eruption as a life history marker in hominin evolution, understanding what M1 eruption means in terms of maternal energetics and infant development is critical.

Bio

I am an Associate Professor in the Department of Anthropology.  I completed my Ph.D. at Harvard University where I reconstructed the paleoecology of Sivapithecus, a Miocene ape from Pakistan.  My research focuses on the interaction of climatic, vegetation, and faunal changes in the fossil record, particularly with respect to ape and hominin paleoecologies.  I use stable isotopic analyses to reconstruct paleohabitats, climates, and diets. To better reconstruct the past, I also work with modern ecosystems including a modern chimpanzee site in Uganda.  My goal is to have a direct comparison between fossil and modern data to better interpret fossil ape and hominin adaptations.  Much of my work focuses on Miocene apes with a goal of determining whether they had habitat requirements similar to those of modern apes and thereby understand what role changing climate played in their extinction.  If fossil apes differed in their habitat and dietary requirements from modern apes, then how, with similar body and brain sizes as well as life history regimes, could they ecologically afford to exploit harsher habitats?  I also conduct isotopic analyses of fossil equids because they are essential to understanding the expansion of grasslands in the Miocene as well as changes in climate such as increasing seasonality.