Why were there not any sustained increases in material productivity of human labor back before 1500?

Since improved technology quickly ran aground on resource scarcity. As human populations grew the stocks of natural resources known had to be distributed up among more and more people: miners had to use lower-quality metal ores, farmers had to farm lesser-quality agricultural land and forests vanished. Who alive today has ever seen one of the cedars of Lebanon? In place of technological progress resource scarcity meant that efficiency of labor was little if any greater in 1500 A.D. than in 1500 B.C.