With Asia, as we shall presently see, it has been different, especially in historic times. There has been no impenetrable barrier between : the inhabitants of Asia have been able to throw themselves into Europe, not without some difficulty, of course, but the feat has been possible, and it has been accomplished.
It is probable, however, that in prehistoric times, after man's appearance on the earth, conditions were somewhat different. It is probable that the north of Europe was colder even than it is now, that over Great Britain and Ireland, Norway and Sweden, the north of Russia and Germany, and over all the seas between, there lay for ages a great mass of ice. South and east of this ice-sheet was a great sea, of which the Caspian and the Sea of Aral are now the remnants. Southward were con ditions other than those we know. It is probable that the Sahara was not such an utter desert as now, but had a moister climate. Also there is some evidence to show that the Mediterranean was not so much of a barrier between Africa and Europe, possibly because the land connections were more continuous. Thus, on the one hand, Europe was more directly connected with Africa and less directly connected with Asia than is now the case, and, on the other, the north of Europe was even less habitable for early peoples than it became in later times.
Whatever the cause, it is almost certain that in early prehistoric times men of the same race wandered over all the land northward from tropical Africa, but they had little, if anything, to do with men from Asia. To the north, as the life was harder, fewer men roamed. But of this time we have no record ; there is no history, and it is scarcely to be wondered at ; the factors were absent which so controlled man's thoughts and actions that he was stimulated to advance. The possibility of advance also was largely lacking. As long as there was no desert, there was no history worth the name.
When modern climatic conditions began to come into existence, the men of this more or less homogeneous race who inhabited Euro-Africa were divided from each other by three barriers, and it may be that the three were but manifestations of one phenomenon.
(a) The way from Asia somehow became more open, and a race of men, keeping to the highlands of Asia Minor, the Balkans and the Alps, drove a wedge, as it were, of highlanders between the lowlanders on either side.
(b) The Mediterranean became more of a barrier than it had been.
(c) The desert conditions in the Sahara became more marked, and the greatest barrier of all was established.
These three barriers divided the original race into four sets of men, who, exposed to climatic and other geo graphical influences, have gradually by adaptation to environment changed and fixed their characteristics.
(a) In the north were the Teutonic peoples, at first comparatively few in number, and undarkened by excessive exposure to the effect of the sun's rays.
(b) South of the Alpine highlands was a race which, under blue skies and beautiful natural surroundings, is distinguished by the exquisite taste for form and colour which has been developed.
(c) Shut in between the Mediterranean and the desert are the Berbers, who under hard conditions have been little able to develop, and the Egyptians, who have responded to the stimulus of the yearly rhythm in the supply of water.
(d) South of the Sahara are the Negroes, black and able to withstand a powerful sun.
Of the great land south of the Sahara we shall speak later. Of the lands between the Sahara and the Alps we have already spoken. It is to the land north of the Alps that we must now look.
With the change in the climatic conditions not only did southern Africa become a land apart, but Europe was thrown open to influences from Asia.
Maps of Euro-Asia show a great band of high ground along its eastern, southern and western borders. Within, and shut off from the sea on every side except the frozen north, is a great plain roughly triangle-shaped, little of it higher than 600 feet above sea-level. This is the great plain of the world. We have already noticed the essential difference between highland and lowland, and seen that in Western Europe the very diversity of feature has had its effect on history. Here the point to be noticed is that the conditions are the same over vast areas. Notice what these conditions are. This plain is remote from the sea. Not only is it remote, but a belt of high ground intervenes. Thus breezes from the sea have lost the greater part of their moisture ere they reach it : over the whole area rainfall is scanty, and little but grass will grow, so it is a steppeland. The remoteness from the sea has another result; with little moisture in the air either to temper the heat of the sun when he shines or retain the heat when he has withdrawn, the climate is everywhere one of extremes.