The biology of African apes provides an important comparative framework for interpreting the evolutionary unfolding of our own species, Homo sapiens. Understanding the ontogeny of our closest living relatives is critical, as evolutionary transformations in adult shape ultimately arise through changes in the timing and patterning of growth and development. However, our current knowledge of African ape skeletal ontogeny is deficient in two important respects. First, wild-shot museum specimens lack the single datum necessary for a comprehensive study of ontogeny: specimen age. Second, skeletal research on African apes invariably uses samples that are pooled at the subspecies, species, or even genus level. This work aims to rigorously quantify and compare the patterns of cranial ontogeny in African ape populations, utilizing two important new skeletal samples with known ages. Unlike most previous research, this study will use samples assigned to specific populations in order to characterize intraspecific variation in development. This work aims to answer the following questions: 1) how do African ape populations differ in their ontogeny? 2) to what degree do ontogenetic models based on pooled samples diverge from population-level ontogenies? 3) how does ontogeny mediate sexual dimorphism in Gorilla and Pan?, and 4) which aspects of anatomy provide insight into heterochronic relationships between extant taxa?