In their primeval home and probably before the year B.C. 3000, they had
already acquired a fair degree of civilization. They built houses,
ploughed the land, and ground grain into flour for their baking. The
family relations were established among them; they had some social
organization and simple form of government; they had learned to worship
a god, and to see in him a counterpart of their tribal ruler.

From their upland farms they must have looked eastward upon yet higher
mountains, rising impenetrable above the snowline; but to north and
south and west they might turn to lower regions; and by degrees, perhaps
as they grew too numerous for comfort, a few families wandered off along
the more inviting routes. Whichever way they started, their adventurous
spirit led them on. We find no trace of a single case where hearts
failed or strength grew weary and the movement became retrograde, back
toward the ancient home. Spreading out, radiating in all directions, it
is they who have explored the earth, who have measured it and marked its
bounds and penetrated almost to its every corner. It is they who still
pant to complete the work so long ago begun.

Before B.C. 2000 one of these exuded swarms had penetrated India,
probably by way of the Indus River. In the course of a thousand years or
so, the intruders expanded and fought their way slowly from the Indus to
the Ganges. The earlier and duskier inhabitants gave way before them or
became incorporated in the stronger race. A mighty Aryan or Hindu empire
was formed in India and endured there until well within historic times.

Yet its power faded. Life in the hot and languid tropics tends to
weaken, not invigorate, the sinews of a race. Then, too, a formal
religion, a system of castes[8] as arbitrary as among the Egyptians,