Cultivation, history, origin, and distribution of cultivated plants.

A large number of plants used by man for a special purpose have not changed as a result of human activity. Others, especially food-plants, know a long history of improvement. They are cultivated for centuries or millennia and changed to such an extend that they probably could not survive under natural conditions anymore. At first, improvement resulted from selection, with variable success. Later, specific interbreeding resulted in better products, and today genetic modification is a tool for improvement. The aims of these improvements were various: higher yields as result of a higher tolerance for restricting environmental factors like temperature, precipitation and wind; decrease of losses as a result of early falling of grains; and a higher resistance against diseases.
On the other hand, there has been an important improvement of the quality of food and products. Nutritional value, storage qualities, smell and taste, as well as fibre length or sugar content, have been improved markedly. At the same time, many useful plants were taken to places far outside their natural area of distribution (origin). After the discovery of America in 1492 a large number of plants were introduced into Europe by the early explorers and vice versa. Later, plants were imported into the new colonies for economical purposes.

Early men throughout the ages recognised and used a great number of plant species. As long as humans have existed they have tried to make plants serve their needs. The quickest way to do so takes place in our times and with modern techniques. Today, for the first time in history, plants are altered in a very short period of time by exchanging genetic material between species. Varieties with a higher resistance against diseases, a higher yield, or with an altered structure or taste, appear on the market frequently. For instance, in the US the major part of soy beans and maize is genetically modified. In the Netherlands varieties of tomatoes are developed with a new texture of the flesh and taste. However, not everybody is happy with this development. Genetically modified plants like soy and maize are used in hundreds of products without notice to the customer. Supporters point out the economic benefits, opponents emphasize that long-term effects of genetic modifications are unknown. The discussion between supporters and opponents will not come to an end soon; neither will the practice of genetic engineering.