The study of history without a thorough knowledge of geography is almost as futile as the hope of interpreting the structure of the ape without thinking of his arboreal life.[139] Contour lines are of vast, often dominant, importance in the life of every nation. John Bull has been moulded, if not made, by his island. Italy could never be safe until its boundary followed the crest of the Alps. Great mountain chains mark limits, and river valleys are thoroughfares. Whoever holds Constantinople controls the trade of a boundless area. If this is true to-day, it must have been far more important in prehistoric times, when man had only begun to gain a certain degree of independence or mastery of nature. Culture was then very largely determined by position and routes of communication. The Alps and Pyrenees formed a long, impassable barrier between northern and southern Europe, broken only by the Rhone valley; and northern Europe was split into an eastern or middle and a western province by the Juras, the Vosges, and the forested Ardennes. Then, as now, the Pass of Belfort was the narrow opening, and Belgium, always the battle-ground of nations, the great thoroughfare between middle Europe and France. From the south, and to a certain degree from the west, middle Europe was not easy of access. But to the eastward there are few or no natural boundaries as it goes over into the great Russian plain, of which North Germany is practically a westward projection. We might possibly go farther and accept literally the somewhat exaggerated statement that all Europe is only a peninsula of Asia. Osborn has called attention to the fact that from Paleolithic to Neolithic time Europe gave rise to no new races.[140] The immigrants entered their new home with all their physical and mental characters already fixed or determined. The routes of migration of the successive waves of lower Paleolithic immigrants are still unknown. Remains of Chellean and Acheulean cultures are rich and widely distributed everywhere around the Mediterranean, especially in northern Africa, at this time well watered. The entrance of Neanderthal man into Europe may well have been from this direction.