The ‘‘Habitat Theory’’ by Elisabeth S. Vrba offers an insightful perspective on the connection between paleoclimate and hominin evolution. However, approaches to test this theory precisely using faunal evidence are lacking. Refined δ13C values offer promising grounds to test this theory. This thesis refines (normalizes and corrects) δ13C values from modern African Great Apes, and demonstrates the efficacy of stable carbon isotope ecology to test postulates of the Habitat Theory. The mean for all refined 13C values is -14.8. This reflects a predominantly C3 feeding and forest-adapted lineage. Habitat patterns explain 88% of the variation in refined δ13C values; genus explains 5%; species level explains 51%; and subspecies explains 55% of the variation. Refined δ13C values also show that most populations are significantly different from each other. Tracing δ13C value patterns from fossil fauna promises to provide insights on the connection between paleoclimate and hominin evolution.