Kaia Tombak

When food availability is constrained during the lean season, animals will prioritize achieving their target intake for certain nutrients over others. Recent studies have revealed an intriguing divergence in hominid nutritional ecology: chimpanzees, orangutans, and humans prioritize protein intake, while mountain gorillas prioritize energy intake. This suggests that protein prioritization is the ancestral hominid metabolic strategy, but such an interpretation depends on the assumption that macronutrient prioritization is under phylogenetic inertia rather than being adaptable to local nutrient availability. We aim to study macronutrient prioritization in two key great ape species for which such data are lacking: the western lowland gorilla (Gorilla gorilla) and the bonobo (Pan paniscus). Lowland gorillas feed more on fruit than mountain gorillas do, and bonobos rely more on herbaceous vegetation than do chimpanzees. If each species follows their congeners in nutrient prioritization, our study will indicate that this trait is under phylogenetic inertia and that protein prioritization is likely an ancestral hominid trait and the probable metabolic strategy employed by all species of Homo. If, however, we find macronutrient prioritization to vary more flexibly with nutrient availability in the habitat, various species and populations of Homo may have differed in their nutrient requirements and constraints.