Initially, agriculture was just an art, summed up by gathering, hunting and gathering, but the sedentarization of man and the increase in population forced the application of visa techniques, leading to a vertical and horizontal agricultural revolution. This linear approach, often described as "top-down", is based, on the one hand, on the (at least implicit) conviction that the experimental station is in essence the place where technical models of progress are developed, and, on the other, on a clear and strict division of roles between the various players: It was up to researchers to design these new models, and up to extension workers to find suitable ways of passing them on to the farmers, who were responsible for applying them.