own land, and encroachments upon neighboring territory necessitated by
growth. Back of all such movements is natural increase of population
beyond local means of subsistence, and the development of the war spirit
in the effort to secure more abundant subsistence either by raid or
conquest of territory.

[Sidenote: Evolution of the Historical Movement.]

Among primitive peoples this movement is simple and monotonous. It
involves all members of the tribe, either in pursuit of game, or
following the herd over the tribal territory, or in migrations seeking
more and better land. Among civilized peoples it assumes various forms,
and especially is differentiated for different members of the social
group. The civilized state develops specialized frontiersmen, armies,
explorers, maritime traders, colonists, and missionaries, who keep a
part of the people constantly moving and directing external expansion,
while the mass of the population converts the force once expended in the
migrant food-quest into internal activity. Here we come upon a paradox.
The nation as a whole, with the development of sedentary life, increases
its population and therewith its need for external movements; it widens
its national area and its circle of contact with other lands, enlarges
its geographical horizon, and improves its internal communication over a
growing territory; it evolves a greater mobility within and without,
which attaches, however, to certain classes of society, not to the
entire social group. This mobility becomes the outward expression of a
whole complex of economic wants, intellectual needs, and political
ambitions. It is embodied in the conquests which build up empires, in
the colonization which develops new lands, in the world-wide exchange of
commodities and ideas which lifts the level of civilization, till this
movement of peoples becomes a fundamental fact of history.