This in a thousand variations has been one of the main stories in history for the last seventy centuries or more. In the first history that we can clearly decipher we find already in all the civilized regions a distinction between a non-working ruler class and the working mass of the population. And we find too that after some generations, the aristocrat, having settled down, begins to respect the arts and refinements and law-abidingness of settlement, and to lose something of his original hardihood. He intermarries, he patches up a sort of toleration between conqueror and conquered; he exchanges religious ideas and learns the lessons upon which soil and climate insist. He becomes a part of the civilization he has captured. And as he does so, events gather towards a fresh invasion by the free adventurers of the outer world.[102] § 2A [Illustration: A very early Sumerian stone carving showing Sumerian warriors in phalanx] This alternation of settlement, conquest, refinement, fresh conquest, refinement, is particularly to be noted in the region of the Euphrates and Tigris, which lay open in every direction to great areas which are not arid enough to be complete deserts, but which were not fertile enough to support civilized populations. Perhaps the earliest people to form real cities in this part of the world, or indeed in any part of the world, were a people of mysterious origin called the Sumerians. They were neither Semites nor Aryans, and whence they came we do not know. Whether they were dark whites of Iberian or Dravidian affinities is less certainly to be denied.[103] They used a kind of writing which they scratched upon clay, and their language has been deciphered.[104] It was a language more like the unclassified Caucasic language groups than any others that now exist. These languages may be connected with Basque, and may represent what was once a widespread group extending from Spain and western Europe to eastern India, and reaching southwards to Central Africa. These people shaved their heads and wore simple tunic-like garments of wool. They settled first on the lower courses of the great river and not very far from the Persian Gulf, which in those days ran up for a hundred and thirty miles[105] and more beyond its present head. They fertilized their fields by letting water run through irrigation trenches, and they gradually became very skilful hydraulic engineers; they had cattle, asses, sheep, and goats, but no horses; their collections of mud huts grew into towns, and their religion raised up towerlike temple buildings. Clay, dried in the sun, was a very great fact in the lives of these people. This lower country of the Euphrates-Tigris valleys had little or no stone. They built of brick, they made pottery and earthenware images, and they drew and presently wrote upon thin tile-like cakes of clay. They do not seem to have had paper or to have used parchment. Their books and memoranda, even their letters, were potsherds.