Parasites and disease can act as strong selective forces in primate evolution by inflicting substantial costs on reproduction and survival. Geladas are infected by a multitude of parasites, including the larval stage of the tapeworm Taenia serialis (a major driver of death for female geladas; Schneider-Crease et al. 2017) and a number of gastrointestinal helminths. Our ongoing research harnesses genomic and immunological tools to understand how the social environment during infancy shapes susceptibility and disease. We examine the roles of social relationships, trauma, and anthropogenic habitat change in immunological development and lifetime health outcomes, and use these findings as a foundation from which to understand variation in susceptibility and disease in humans.