This unifying and stimulating national task of utilizing and controlling the water was the same task which in various forms prompted the early civilization of the Hoangho and Yangtze basins, India, Mesopotamia, Persia, Peru, Mexico, and that impressive region of prehistoric irrigation canals found in the Salt, Gila River, and upper Rio Grande valleys.[616] Here the arid plateaus of the Cordilleras between the Pueblo district and Central America had no forests in which game might be found; so that the Indian hunter had to turn to agriculture and a sedentary life beside his narrow irrigated fields.  Here native civilization reached its highest grade in North America.  Here desert agriculture achieved something more than a reliable food supply.  It laid the foundation of the first steady integration of wandering Indian hordes into a stable, permanently organized society.  Elsewhere throughout the North American continent, we see only shifting groups of hunter and fisher folk, practising here and there a half nomadic agriculture to supplement the chase.

The primitive American civilization that arose among the Pueblo Indians of New Mexico and Arizona, the only strictly sedentary tribes relying exclusively on agriculture north of the Mexican plateau, was primarily a result of the pressure put upon these people by a restricted water supply.[617] Though chiefly offshoots of the wild Indians of the northern plains, they have been markedly differentiated from their wandering Shoshone and Kiowa kindred by local environment.[618] Scarcity of water in those arid highlands and paucity of arable land forced them to a carefully organized community life, made them invest their labor in irrigation ditches, terraced gardens and walled orchards, whereby they were as firmly rooted in their scant but fertile fields as were their cotton plants and melon vines;[619] while the towering mesas protected their homes against marauding Ute, Navajo and Apache.[620] This thread of a deep underlying connection between civilization and the control of water can be traced through all prehistoric America, as well as through the earliest cultural achievements in North Africa and Asia.

[Sidenote:  Economy of the water:  fisheries.]

The economy of the water is not confined to its artificial distribution over arid fields, but includes also the exploitation of the mineral and animal resources of the vast world of waters, whether the production of salt from the sea, salt lakes and brine springs, the cultivation of oyster beds, or the whole range of pelagic fisheries.  The animal life of the water is important to man owing not only to its great abundance, but also to its distribution over the coldest regions of the globe.  It furnishes the chief food supply of polar and sub-polar peoples, and therefore is accountable for the far-northern expansion of the habitable world.  Even the reindeer tribes of Arctic Eurasia could hardly subsist without the sea food they get by barter from