From the north-west, then, into Northern India have streamed by ones and twos, by thousands and hundreds of thousands, immigrants and merchants, exiles and conquerors. Some have stopped on this threshold. Assyrian and Greek, long before the days of Alexander, had reached this land and come no farther. Alexander marched his armies into the heart of the Punjab, but the unknown conditions made his soldiers mutiny, and he retired. Others, however, both before and after Alexander, from the north-west frontier have spread to a greater or less extent over the whole of India.
The sea, too, is a way open to all who have been trained to use it, so that, as far back as we can trace, the peninsular part of India has been influenced by sea peoples ; to a slight extent in the earlier periods by the more civilized men of the dry west and the ruder folk of the wet east, but in the later years the organizing forces have come from overseas, first from the south round the Cape, and then from the west.
Those peoples, then, coming from north, west and from the sea have, on the one hand, usually brought something higher than was already there, and, on the other, have tended to destroy such civilization as they found, and to displace to some extent the earlier inhabitants of India.
It is natural that the earliest aboriginal peoples should exist in the hilly forest and jungle belt which stretches across the northern part of the Dekkan. Here they find not only protection against newcomers, but food to keep them alive. Those forests are similar to the forests of Europe in that they afford protection, but differ from them in this, that while life could be pre served in the colder European forests only by the exercise of forethought and the taking of trouble, and it paid to clear portions of the forest and to settle, in those Indian jungles the bare necessaries are easily obtained, and there is little stimulus to advance.
To disturb those aboriginal peoples the stream of humanity was flowing from the north-west even before the dawn of history, whether from the great plain or from the Iran plateau we do not know. These first corners in time were in part driven south-eastwards, and in part absorbed by successive waves of races of different stocks who certainly came from the north during the three thousand years from 2500 B.c., and
who gradually established themselves in the northern plain of India, leaving the Dekkan from the forest belt southwards to those who had preceded them. Thus the natural differences between northern plain and southern plateau have been intensified by the fact that each is inhabited by peoples with different characteristics.
Among those peoples organization of a kind occurred, more effective in the north, where kingdoms stood for 300 years, less effective in the south ; but our information is significantly lacking. The very absence of informa tion indicates a want of continuous organization in any one place. What is fairly clear is that men with different characteristics lived and organized themselves in ordered communities, and that the differences largely depended on geographical conditions. The northern plain is not all one. In the south-east, Bengal, it is wet and naturally jungle-covered; in the north-west, the Punjab, it is dry ; and in the west, Sind, it is drier still, so that the Indus is like the Nile and receives no tributaries in its lower course. Between these two extremes lies an area roughly corresponding to the old Middle Land, now the North-West Provinces, whose rainfall is sufficient for man's needs, but not excessive. This is the region where to this day are the greatest numbers of people in cities and in the country.
By A.D. 600 these three areas were more or less effec tively organized by three groups of people ; but though the three regions exist and are markedly different, they shade imperceptibly into one another, and neither between each nor within each are there any natural frontiers, since the inhabitants do not look on the rivers as boundaries, but as channels of communication and beneficent suppliers of water. Hence friction is almost unavoidable except under a stable central govern ment. The stable central government did not exist, and an active source of unrest was to be found in the continual inroads of steppe peoples, those Huns, Tatars and Scythians who in the Far East caused the same unsettled conditions directly or indirectly. For a time, union in the face of a common danger could, and did, take place, but the bond was not strong enough to be permanent.