Lewis Mumford (1895-1990), The City in History
(New York: Harcourt Brace Jovanovich, Inc., 1961), p. 5:
Human life swings between two poles: movement and settlement. The
contrast between these modes may be traced back to the original break
between the mainly free-moving protozoa that formed the animal kingdom
and the relatively sessile organisms that belong to the vegetable kingdom.
The first, like the oyster, sometimes become overadapted to a fixed position
and lose the power of movement; while many plants free themselves in some
degree by underground rootings and above all, by the detachment and
migration of the seed. At every level of life one trades mobility for security,
or in reverse, immobility for adventure. Certainly, some tendency to settle
and rest, to go back to a favored spot that offers shelter or good feeding
exists in many animal species; and, as Carl O. Sauer has suggested, a
propensity to store and settle down may itself be an original human trait.