eturns had for its
corollary a law of increasing moral insight. In this case, geographic
conditions worked through the medium of direct economic effects to more
important political and ethical results.

The roots of geographic influence often run far underground before
coming to the surface, to sprout into some flowering growth; and to
trace this back to its parent stem is the necessary but not easy task of
the geographer.

[Sidenote: Time element.]

The complexity of this problem does not end here. The modification of
human development by environment is a natural process; like all other
natural processes, it involves the cumulative effects of causes
operating imperceptibly but persistently through vast periods of time.
Slowly and deliberately does geography engrave the subtitles to a
people's history. Neglect of this time element in the consideration of
geographic influences accounts equally for many an exaggerated assertion
and denial of their power. A critic undertakes to disprove modification
through physical environment by showing that it has not produced
tangible results in the last fifty or five hundred years. This attitude
recalls the early geologists, whose imaginations could not conceive the
vast ages necessary in a scientific explanation of geologic phenomena.

The theory of evolution has taught us in science to think in larger
terms of time, so that we no longer raise the question whether European
colonists in Africa can turn into negroes, though we do find the recent
amazing statement that the Yankee, in his tall, gaunt figure, "the
colour of his skin, and the formation of his hair, has begun to
differentiate himself from his European kinsman and approach the type of
the aboriginal Indians."[28] Evolution tells the story of modification
by a succession of infinitesimal changes, and emphasizes the permanence
of a modification once produced long after the causes for it cease to
act. The mesas of Arizona, the earth sculpture of the Grand Canyon
remain as monuments to the erosive forces which produced them. So a
habitat leaves upon man no ephemeral impress; it affects him in one way
at a low stage of his development, and differently at a later or higher
stage, because the man himself and his relation to his environment have
been modified in the earlier period; but traces of that earlier
adaptation survive in his maturer life. Hence man's relation to his
environment must be looked at through the perspective