Sex differences in health burdens across the lifespan in wild chimpanzees (

Background and Objectives: Understanding health and aging in one of our closest relatives, wild chimpanzees, provides key insights into the evolutionary origins of human disease risk. In humans, females often experience higher rates of disease than men despite having longer lifespans. Here we examine age- and sex- related patterns of health burdens in three communities of wild chimpanzees to investigate whether males exhibit health disadvantages, as predicted by life history trade-offs, or whether females exhibit health disadvantages in line with the health-survival paradox. Methodology: We analyzed 16 years of observational health data from the Kasekela and Mitumba communities of Gombe National Park, Tanzania, and the Kanyawara community of Kibale National Park, Uganda. We recorded clinical signs of respiratory illness, diarrhea, and injuries, along with annual cumulative health signs. We used generalized linear mixed models to examine the effects of sex and age on these measures while controlling for community differences and annual and seasonal patterns. Results: Respiratory clinical signs increased with age, but there were no sex differences. Males exhibited significantly increased likelihood of injuries and diarrhea with peaks in middle-aged years, and higher cumulative health burdens than females throughout adulthood. Conclusions and Implications: Our findings align with predictions from life history theory, suggesting that males prioritize reproductive effort over somatic maintenance, leading to greater health risks. The absence of a male-female health survival paradox in chimpanzees suggests that this pattern in humans is a derived trait, shaped by sociocultural, lifestyle, and environmental factors. These results highlight the importance of cross-species comparisons in understanding the evolution of health and aging.