Already in those days a sort of primitive trade had sprung up. Bronze and bronze weapons, and such rare and hard stones as jade, gold because of its plastic and ornamental possibilities, and skins and flax-net and cloth, were being swapped and stolen and passed from hand to hand over great stretches of country. Salt also was probably being traded. On a meat dietary men can live without salt, but grain-consuming people need it just as herbivorous animals need it. Hopf says that bitter tribal wars have been carried on by the desert tribes of the Soudan in recent years for the possession of the salt deposits between Fezzan and Murzuk. To begin with, barter, blackmail, tribute, and robbery by violence passed into each other by insensible degrees. Men got what they wanted by such means as they could.[59] § 6 So far we have been telling of a history without events, a history of ages and periods and stages in development. But before we conclude this portion of the human story, we must record what was probably an event of primary importance and at first perhaps of tragic importance to developing mankind, and that was the breaking in of the Atlantic waters to the great Mediterranean valley. The reader must keep in mind that we are endeavouring to give him plain statements that he can take hold of comfortably. But both in the matter of our time charts and the three maps we have given of prehistoric geography there is necessarily much speculative matter. We have dated the last Glacial Age and the appearance of the true men as about 40,000 or 35,000 years ago. Please bear that “about” in mind. The truth may be 60,000 or 20,000. But it is no good saying “a very long time” or “ages” ago, because then the reader will not know whether we mean centuries or millions of years. And similarly in these maps we give, they represent not the truth, but something like the truth. The outline of the land was “some such outline.” There were such seas and such land masses. But both Mr. Horrabin, who has drawn these maps, and I, who have incited him to do so, have preferred to err on the timid side.[60] We are not geologists enough to launch out into original research in these matters, and so we have stuck to the 40-fathom line and the recent deposits as our guides for our post-glacial map and for the map of 12,000 to 10,000 B.C. But in one matter we have gone beyond these guides. It is practically certain that at the end of the last Glacial Age the Mediterranean was a couple of land-locked sea basins, not connected--or only connected by a torrential overflow river. The eastern basin was the fresher; it was fed by the Nile, the “Adriatic” river, the “Red-Sea” river, and perhaps by a river that poured down amidst the mountains that are now the Greek Archipelago from the very much bigger Sea of Central Asia that then existed. Almost certainly human beings, and possibly even Neolithic men, wandered over that now lost Mediterranean valley.