For several million years, humans got to where they wanted to go by one means: walking. This, of course, greatly limited the distance of travel and the amount of items that could be transported. Today, transportation is accomplished in the air, on land, and in water. It ranges from carts pulled by horses or oxen and dirt roads in Africa to the Concorde supersonic airplane that can travel from Paris to New York in four hours.

The first changes in transportation came about five to six thousand years ago in three areas: the introduction of boats, the domestication of wild horses, and the invention of the wheel. Horse domestication started about 6,000 years ago, probably occurring in several different parts of the world at about the same time. Riding astride the horse may have begun in Turkestan before 3,000 B.C. At about the same time, many historians believe the...