ing to the north and east of the Assyrian and Babylonian empires. We have already spoken of the arc-like dispersion of the Nordic Aryan peoples to the north of the Black and Caspian Seas; it was probably by this route that the Aryan-speaking races gradually came down into what is now the Persian country, and spread, on the one hand, eastward to India (? 2000 to 1000 B.C.), and on the other, increased and multiplied in the Persian uplands until they were strong enough to assail first Assyria (650 B.C.) and then Babylon (538 B.C.).
There is much that is not yet clear about the changes of climate that have been going on in Europe and Asia during the last 10,000 years. The ice of the last glacial age receded gradually, and gave way to a long period of steppe or prairie-like conditions over the great plain of Europe. About 12,000 or 10,000 years ago, as it is reckoned now, this state of affairs was giving place to forest conditions. We have already noted how, as a consequence of these changes, the Solutrian horse hunters gave place to Magdalenian fishers and forest deer hunters; and these, again, to the Neolithic herdsmen and agriculturists. For some thousands of years the European climate seems to have been warmer than it is to-day. A great sea spread from the coast of the Balkan peninsula far into Central Asia and extended northward into Central Russia, and the shrinkage of that sea and the consequent hardening of the climate of south Russia and Central Asia was going on contemporaneously with the development of the first civilizations in the river valleys. Many facts seem to point to a more genial climate in Europe and western Asia, and still more strongly to a greater luxuriance of plant and vegetable life, 4000 to 3000 years ago, than we find to-day. There were forests then in south Russia and in the country which is now Western Turkestan, where now steppes and deserts prevail. On the other hand, between 1500 and 2000 years ago, the Aral-Caspian region was probably drier and those seas smaller than they are at the present time.
We may note in this connection that Thotmes III (say, the fifteenth century B.C.), in his expedition beyond the Euphrates, hunted a herd of 120 elephants in that region. Again, an Ægean dagger from Mycenæ, dating about 2000 B.C., shows a lion-hunt in progress. The hunters carry big shields and spears, and stand