The history of agricultural research and development (R&D) has never been static. Its philosophies, concepts and principles continue to change and to impact on present-day practices. It is imperative to understand and draw lessons from the old and new perspectives, which inform agricultural R&D processes and policy formulation in developing countries. The interest of this paper is, therefore, to draw relevant lessons that can explain the dynamics,of the innovation systems at the grassroots in sub-Saharan Africa in particular.