There is a body of theory, most clearly delineated in recent years by V. Gordon Childe, concerning the importance of the appearance of Food-Production as a basic economic revolution. The domestication of plants and animals assured a stable food supply. Proper village life now came into being, and with it a completely new kind of technology. This latter depends on the fact that time now became available for pursuits other than that of simply collecting food. The theory holds it to be no coincidence that such crafts as architecture, pottery, weaving, and presently metallurgy make their appearance with the establishment of Food-production. These crafts make use of materials constructively, and in some cases actually change the physical or chemical properties of the materials. Such a technology was not characteristic of the preceding Food-gathering stage. The Food-producing revolution and the type of technology which attended it were at least the economic prerequisite for the appearance of civilization (in any useful sense of that word).