isolation--Protection of an island environment--Islands as places of
refuge--Islands as places of survival--Effects of small area in
islands--Economic limitations of their small area--Dense population of
islands--Geographic causes of this density--Oceanic climate as
factor--Relation of density to size--Density affected by a focal
location for trade--Overflow of island population and colonies to the
mainland--Precocious development of island agriculture--Intensive
tillage--Emigration and colonization from islands--Recent emigration
from islands--Maritime enterprise as outlet--Artificial checks to
population--Polyandry--Infanticide--Low valuation of human life.


CHAPTER XIV. PLAINS, STEPPES AND DESERTS

Relief of the sea floor--Mean elevations of the continents--Distribution
of relief--Homologous reliefs and homologous
histories--Anthropo-geography of lowlands--Extensive plains unfavorable
to early development--Conditions for fusion in plains--Retardation due
to monotonous environment--Influence of slight geographic features in
plains--Plains and political expansion--Arid plains--Nomadism--Pastoral
life--Pastoral nomads of Arctic plains--Historical importance of steppe
nomads--Mobility of pastoral nomads--Seasonal migrations--Marauding
expeditions--Forms of defense against nomad depredations--Pastoral life
as a training for soldiers--Capacity for political organization and
consolidation--Centralization versus decentralization in
nomadism--Spirit of independence among nomads--Resistance to
conquest--Curtailment of nomadism--Supplementary agriculture of pastoral
nomadism--Irrigation and horticulture--Scant diet of nomads--Effects of
a diminishing water supply--Checks to population--Trade of
nomads--Pastoral nomads as middlemen--Desert markets--Nomad