The Plough represents the complete transition from gathering to farming, and it is one of the critical Advances, in that it allows Cities to build Farms, which sustain larger Populations.
The cultivation of plants for food dates back thousands of years, but frequently the ’cultivation’ was little different from simple gathering. Once men began materially altering the conditions under which the plants grew, however, the importance of agriculture as a source of food outstripped all earlier methods. Primary among the changes made were planting crops in separate and distinct fields that had been prepared by breaking up the soil and watering it. The major technological construction that allowed this was the plough. Since early ploughs were made almost entirely of wood, hard evidence for its first introduction is largely missing. Evidence of copper-faced wooden ploughs first appears in Mesopotamia around 4000 BC. The first pictorial evidence of ploughs in use, drawn by oxen, is from Egypt about 2500 BC. The original ploughs were much earlier, because early cities relying on the concentrated agriculture made possible by ploughing had already existed for several thousand years by that time.