Geoscience Reference
In-Depth Information
The first civilizations
Ancient civilizations emerged on the floodplains of large rivers in several parts of the world
between 3,500 and 5,500 years ago. The appearance of the Sumerian, Egyptian, and Harap-
pan civilizations along the alluvial valleys of the Tigris-Euphrates, the Nile, and the Indus
respectively was due in large part to the key benefits offered by their rivers: an abundant
supply of fresh water, fertile alluvial soils, and a ready transport corridor for trade and trav-
ellers. In each case, the society's reliance on its river was emphasized by the arid location,
making inhabitants particularly dependent upon a reliable flow of water for agriculture and
their continued existence in a desert environment. All three river systems are exotic: rising
in areas with more humid climates which maintain their perennial flow through the desert.
One theory linking many of the factors involved in the emergence of these first civilizations
suggests that the central organization required to manage irrigation in desert areas also al-
lowed complex societies to evolve as large numbers of people congregated to live in the
same place. This tendency led eventually to the creation of the first cities and what are
popularly thought of as the first civilizations. Each of these three early river-based civiliza-
tions developed its own ways of diverting and channelling water, growing and storing food.
Systems for writing, making laws, and many other hallmarks of civilization also emerged
separately in these three regions. This theory of 'hydraulic civilizations' suggests that the
deliberate manipulation and regulation of their rivers by these early societies was an inher-
ent and necessary precondition of civilization.
Another idea takes the links between these early complex societies and their rivers a step
further, to suggest that the nature, character, and longevity of the civilization was in part
a reflection of the nature of its river. The Tigris-Euphrates, Nile, and Indus are all large,
exotic river systems, but in other respects they are quite different. The Nile has a relatively
gentle gradient in Egypt and a channel that has experienced only small changes over the
last few thousand years, by meander cut-off and a minor shift eastwards. The river usually
flooded in a regular and predictable way. The stability and long continuity of the Egyptian
civilization may be a reflection of its river's relative stability. The steeper channel of the
Indus, by contrast, has experienced major avulsions over great distances on the lower Indus
Plain and some very large floods caused by the failure of glacier ice dams in the Himalay-
an mountains. Likely explanations for the abandonment of many Harappan cities, includ-
ing Mohenjo Daro, take account of damage caused by major floods and/or the disruption
caused by channel avulsion leading to a loss of water supply.
