tage of a reserve
territory for future growth.[107] This was the case of Kursachsen and
Brandenburg in the sixteenth century, and of the United States
throughout its history. But beside the danger of inherent weakness
before attack, a condition of relative underpopulation always threatens
a retardation of development. Easy-going man needs the prod of a
pressing population. [Compare maps pages 8 and 103 for examples.]

[Sidenote: Land and food supply.]

Food is the urgent and recurrent need of individuals and of society. It
dictates their activities in relation to their land at every stage of
economic development, fixes the locality of the encampment or village,
and determines the size of the territory from which sustenance is
drawn. The length of residence in one place depends upon whether the
springs of its food supply are perennial or intermittent, while the
abundance of their flow determines how large a population a given piece
of land can support.

[Sidenote: Advance from natural to artificial basis of subsistence.]

Hunter and fisher folk, relying almost exclusively upon what their land
produces of itself, need a large area and derive from it only an
irregular food supply, which in winter diminishes to the verge of
famine. The transition to the pastoral stage has meant the substitution
of an artificial for a natural basis of subsistence, and therewith a
change which more than any other one thing has inaugurated the advance
from savagery to civilization.[108] From the standpoint of economics, the
forward stride has consisted in the application of capital in the form
of flocks and herds to the task of feeding the wandering horde;[109] from
the standpoint of alimentation, in the guarantee of a more reliable and
generally more nutritious food supply, which enables population to grow
more steadily and rapidly; from the standpoint of geography, in the
marked reduction in the per capita amount of land necessary to yield an
adequate and stable food supply. Pastoral nomadism can support in a
given district of average quality from ten to twenty times as many souls
as can the chase; but in this respect is surpassed from twenty to
thirty-fold by the more productive agriculture. While the subsistence of
a nomad requires 100 to 200 acres of land, for that of a skillful farmer
from 1 to 2 acres suffice.[110] In contrast, the land of the Indians
living in the Hudson Bay Territory in 1857 averaged 10 square miles per
capita; th