This procedure, however, has a double disadvantage. It obscures development because it moves against the current of time; and it fails to describe, first of all, the conditions under which the civilization took shape—in other words, its prehistoric antecedents. Now I am not prepared to attempt a definition of the distinction between prehistory and history in general terms, for even within the ancient Near East the distinction is problematical.[37] I shall simply use the term “prehistory” to denote the period preceding the emergence of Egyptian and Mesopotamian civilization, and shall discuss first the climatic conditions in the Near East at that time and then the form of society which prevailed before the events with which we are primarily concerned took place. At present the arable lands of Egypt and Western Asia are embedded in large tracts of desert. But it seems that in the Ice Age the pressure of cold air over Europe compelled the Atlantic rain storms to travel east by a more southerly track so that the whole area from the west coast of Africa to the Persian mountains was a continuous belt of park and grassland. In Algeria and southern Tripolitania hunters of the Old Stone Age engraved images of elephants, buffaloes, and giraffes on rocks now surrounded for hundreds of miles by an arid waste where life is utterly impossible. Paleolithic implements have been found on the high desert which flanks the Nile valley, and in Syria, Palestine, and Kurdistan. Carved tools found in Palestine (Fig. 1, A, B) and the engravings from North Africa find close parallels in the splendid engravings and paintings from the caves of southern France and northern Spain.