Commerce The primary requirement of man has always been production of food and shelter. The earliest production was growing and grinding of grain. Next was the creation of building materials; then weaponry to defend the surpluses created. The power of falling water, and of wind, augmented that of man and animal in the grinding of grain and in the production of other materials. When more was created than needed, it was desirable to trade the surpluses of one area for differing kinds in others and commerce came into being. The easiest form of transportation in early times was by water and the great Eurasian rivers, along with the Mediterranean and Indian Oceans, became the first heavily used trade routes. It was found that the same breezes driving the wind mills also propelled the vessels. The hoisting and trimming of sails simplified the movement of cargoes. The clustering of urban populations at sea and river ports took warehouses and other commercial buildings higher and brought the means of moving cargo between storage and marketing buildings that were built ever higher to conserve precious urban space. Efficient means of lifting were developed to move materials between producers and users by hoists, cranes and lifts as well as ships, barges and road vehicles. Eventually, mountains of earth were moved to create canals upon which barges could move throughout Europe, America and China and locks were built to raise and lower craft and speed the transport of commercial goods.