e contributory circumstance, we find that
for the evolution of mankind it is large areas like Eurasia which afford
the greatest number and variety of these naturally segregated habitats,
and at the same time the best opportunity for vast historical movements.

[Sidenote: The struggle for space.]

Evolution needs room but finds the earth's surface limited. Everywhere
old and new forms of life live side by side in deadly competition; but
the later improved variety multiplies and spreads at the cost of less
favored types. The struggle for existence means a struggle for space.[296]
This is true of man and the lower animals. A superior people, invading
the territory of its weaker savage neighbors, robs them of their land,
forces them back into corners too small for their support, and continues
to encroach even upon this meager possession, till the weaker finally
loses the last remnant of its domain, is literally crowded off the
earth, becomes extinct as the Tasmanians and so many Indian tribes have
done.[297] The superiority of such expansionists consists primarily in
their greater ability to appropriate, thoroughly utilize and populate a
territory. Hence this is the faculty by which they hasten the extinction
of the weaker; and since this superiority is peculiar to the higher
stages of civilization, the higher stages inevitably supplant the lower.

[Sidenote: Area an index of social and political development.]

The successive stages of social development--savage, pastoral nomadic,
agricultural, and industrial--represent increasing density of
population, increasing numerical strength of the social group, and
finally increasing geographical area, resulting in a vastly enlarged
social group or state. Increase in the population of a given land is
accompanied by a decrease in the share which each individual can claim
as his own. This progressive readjustment to a smaller proportion of
land brings in its train the evolution of all economic and social
processes, reacting again favorably on density of population and
resulting eventually in the greatly increased social group and enlarged
territory of the modern civilized state. Hence we may lay down the rule
that change in areal relations, both of the individual to his decreasing
quota of land, and of the state to its increasing quota of the earth's
surface is an important index of social and political evolution.
Therefore the rise and decline not only of peoples but of whole
civ