Premature weaning can result in poor infant developmental outcomes and increased infant mortality; however, the social conditions that lead to premature weaning and its consequences are still poorly understood. The central goal of this project is to examine how stressful social conditions linked to the immigration of new adult males and/or poor maternal condition influence the likelihood of premature weaning, and, in turn how premature weaning then influences infant growth, gut microbial colonization, and the development of the immune system in a nonhuman primate model. Given the importance of early weaning as a hallmark of human evolution, developing comprehensive longitudinal models of this early life transition are valuable. In addition, the findings may serve as an animal model for understanding the costs and benefits of truncated or extended breastfeeding in modern humans. The project will provide rigorous scientific training to at least one post-doctoral fellow and several graduate and undergraduate students. The PIs will also engage in public outreach at local and international levels, contributing to scientific education and conservation efforts both domestically and abroad.
This project examines the links between social factors, variable weaning strategies, and infant growth and immune system development in geladas. It draws on both cross-sectional and longitudinal data collected from infants aged 0-2.5 years to address the following goals: (1) Determine how social factors related to stressful demographic changes and/or maternal condition influence the timing of nursing cessation; (2) Identify how earlier weaning relative to infant size is related to stunted postnatal growth, altered gut microbial diversity and composition, and the concentration of urinary neopterin, a biomarker for cellular inflammation. Geladas are ideal for this research because their social system is characterized by frequent and stressful social upheavals that disrupt infant development and can even lead to infant mortality. Further, gelada females form strong dominance hierarchies that determine access to food, thus allowing researchers to address how social factors linked to poor maternal nutrition are associated with variable weaning strategies. Together, these attributes make geladas an excellent model system in which to study premature weaning. This study will be one of the first to integrate innovative methods in isotopic/elemental chemistry, genomics, endocrinology, and digital photogrammetry to examine the causes and consequences of premature weaning in wild primate infants, thus identifying some of the key mechanisms bridging early life social adversity to long-term developmental and health. Student trainees will have the opportunity to learn methods in behavioral data collection as well as various wet lab methods to characterize the composition of the gut microbiome and define weaning by the amount of milk vs. plant-origin carbon and nitrogen found in noninvasively collected fecal samples.
