Man must eat in order to live. One of the most important concerns of man during his life on the earth has been to makecertain that he has enough food to eat when he needs it. 

Prehistoric (史前的）had little choice in what he ate. He ate what he could find: roots, eggs, fruits and the meat of smallanimals. Early man had no way to control his food supply. If there was no rain, or the weather was too hot or too cold,plants would not grow, and he would have little or no food. When he ate all the food in one place, he had to move to anotherregion for food. 

Man’s life changed when he learned to grow plants and to raise animals. He also learned to use fire to prepare his food.Later, he learned to make tools and weapons, and to make containers to store his food. Man could now live in one place andproduce his own food. So civilization (文明）began. Great civilizations slowly developed in regions where food wasplentiful — along the Nile River in Egypt, and by the Yellow River in China. 

The kinds of plants which are raised by man are different in each geographical region. In the colder regions very fewplants can be grown; in the warmer parts of the world great varieties of plants are found. In Asia, rice has become the mostimportant crop. In North America, the most important grains are wheat and com. In Europe and North Africa, wheat is themain crop. In the tropical (热带的）regions of the world，many kinds of fruit grow naturally or arc planted by man. 

With the development of methods of keeping food fresh, it became possible to send most food products from one partof the world to another. Today foods are kept fresh in many ways and sent all over the world. Man no longer depends on thefood he grows in his own area only.