Man was a foraging hunter–gatherer during the initial period of evolution. Later he started cultivating cereals and legumes and thus the transition from foraging to farming occurred. As a result, many of the useful wild plants have come under cultivation. Today, thousands of plant species are cultivated throughout the world for various uses. For most of those cultivated species, the wild populations exist in their natural habitats. However, there are some economically significant plants which are extinct in the wild, but survive only under cultivation due to their economical value.