Agronomic analyses of soil dynamics in Africa have been found to be too simplifying and lacking any perspective on the critical role of farmers. Yet soil degradation is widespread and serious, and in many cases cannot be remedied by low levels of external inputs. To explain the fate of African soils, we use the co-evolutionary approach that critics of simple agronomic analyses propose, focusing especially on the interaction between short-term local and long-term global processes. From the late 19th century, industrialisation has broken the endogenous relation between population and prices that until then had facilitated gradual agricultural intensification. At the same time, Africa's evolution in the world system reproduced social structures that hindered more rapid transformations because they precluded a mass eviction of farm workers. Keywords: Soil degradation, Nutrient depletion, Agricultural production, Farming systems, Price policies.