Without transportation, there could be no trade. Without trade, there could be no towns and cities. Towns and cities are traditionally the  16   of civilization. Therefore, transportation helps make civilization  17    .Throughout most of the prehistoric period, people lived by hunting, fishing,and  18  wild plants. They had no beasts of burden, wheeled vehicles, or roads. People travele  19   and carried their infants and belongings strapped to their backs or heads. Loads too heavy for one person to carry were strapped to a pole and carried by two people.  20  , people learned that they could drag loads along the ground on sledges.During late prehistoric times, people began to build sledges with runners.When people developed agriculture and began to establish   21  settlements,trade between settlements started to develop, which created a need for better 22  of transportation. The donkey and the ox, which had been tamed for food products and farm work, helped   23  this need. The use of donkeys and oxen as beasts of burden enabled people to  24  heavier loads than they could before.People also began to develop water transportation during prehistoric times.They built rafts of such   25  as logs or reeds. Later, people learned   26  to make dugouts and canoes. People paddled these early craft with their hands or propelled them with paddles or  27  .The wheel was invented about 3500 B.C and sailboat about 3200 B.C.Wheeled vehicles and sailing vessels  28  transportation. But the speed of transportation improved only   29  over the centuries.Inventors produced the first engine-  30   vehicles during the late 1700’s and the early 1800’s. This development marked the beginning of a revolution in transportation that has continued to the present.

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