While high civilizations were growing up in Mesopotamia, Egypt, and the Aegean, continental Europe was still recovering from an ice age. Though the glaciers had retreated, the high passes that led across the Alps from the favoured Mediterranean to the interior were still virtually closed by snow. The tundras and steppes where the men of the Old Stone Age had hunted the reindeer were now for the most part covered with a dense forest fostered by the damp climate then ruling. Through the belt of forest and mountain that fenced off northern and western Europe early man could not easily penetrate. To reach Britain or Denmark he must take ship and face the perils of the Atlantic in a dug-out canoe or some only slightly superior craft. But one moving road leads right into the heart of the continent. From the Black Sea to Bavaria the Danube opens out a passage way far safer than the stormy Atlantic. Moreover it leads into territories where the uncongenial primeval forest did not grow so densely nor so inhospitably as on the coasts or highlands.

Large tracts in Central Europe are covered with a deep deposit of fine wind-born dust that had formed during the dry ice ages. This aeolian soil termed “löss” is unfavourable to the growth of heavy timber, incidentally it provides ideal agricultural land.