When the first hunters and gatherers became farmers some 10,000 years ago, they started out with only a few crops and crop varieties. Through careful selection of the best seeds and propagating material, and exchange with other farmers, it became possible to develop these few varieties into many different varieties. In addition, new crops were found in the wild that could be cultivated. Through the continuous management and innovation by farmers over thousands of years, the few initial crops and varieties evolved into an inconceivable wealth of crop diversity. Some 7,000 crop species have been cultivated or collected by humans for food (Wilson, 1992, 275), and the estimated number of distinct varieties of some of these crops exceeds 100,000 (FAO, 1998, 18).1