vation, lowlands develop no surface features beyond low hills and
undulating swells of land. Uniformity of life conditions, monotony of
climate as of relief, except where grades of latitude intervene to chill
or heat, an absence of natural boundaries, and constant encouragement to
intercourse, are the anthropo-geographic traits of lowlands, as opposed
to the arresting, detaining grasp of mountains and highland valleys.
Small, isolated lowlands, like the mountain-rimmed plains of Greece and
the Aegean coast of Asia Minor, the Nile flood-plain, Portugal, and
Andalusia in Spain, may achieve precocious and short-lived historical
importance, owing to the fertility of their alluvial soils, their
character as naturally defined districts, and their advantageous
maritime location; but while in these restricted lowlands the telling
feature has been their barrier boundaries of desert, mountains and sea,
the vast level plains of the earth have found their distinctive and
lasting historical importance in the fact of their large and unbounded
surface.

Such plains have been both source and recipient of every form of
historical movement. Owing to their prevailing fitness for agriculture,
trade and intercourse, they are favored regions for the final massing of
a sedentary population. The areas of greatest density of population in
the world, harboring 150 or more to the square kilometer (385 to the
square mile), are found in the lowlands of China, the alluvial plains of
India, and similar level stretches in the Neapolitan plain and Po
Valley, the lowlands of France, Germany, Holland, Belgium, England and
Scotland. Such a density is found in upland districts (660 to 2000 feet,
or 200 to 600 meters) bordering agricultural lowlands, only where
industries based upon mineral wealth cause a concentration of
population. [See maps pages 8, 9, 559.]

[Sidenote: Extensive plains unfavorable to early development.]

The level or undulating surface of extensive lowlands is not favorable
to the early development of civilization. Not only do their wide extent
and absence of barriers postpone the transition from nomadism to
sedentary life, but their lack of contrasting environments and
contrasted developments, which supplement and stimulate, puts chains
upon progress. A flat, monotonous relief produces a monotonous
existence, necessarily one-sided, needing a complement in upland or
mountain. To the pioneer settlers in the lowlands of Missouri the Oza