Agrarian societies transition into industrial societies when less than half of their population is directly engaged in agricultural production. Such societies started appearing because of the Commercial and Industrial Revolution which can be seen beginning in the Mediterranean city-states of 1000-1500 C.E. As European societies developed during the Middle Ages, classical knowledge was reacquired from scattered sources, and a new series of maritime commercial societies developed again in Europe. The initial developments were centered in Northern Italy, in the city-states of Venice, Florence, Milan, and Genoa. By about 1500 a few of these city-states probably met the requirements of having half of their populations engaged in non-agricultural pursuits and became commercial societies. These small states were highly urbanized, imported much food, and were centers of trade and manufacture to a degree quite unlike typical agrarian societies.