Flexi Says: Many plant species which produce fruits, seeds, leaves, or other palatable or useful products to humans have been artificially selected and cultivated for centuries. Examples of such plants include rice, peanuts, and many other varieties of plants. This process helped both the plant species and humans to coevolve. The cultivated plants have a survival advantage, and humans, in turn, benefit from the plant products. For plants that are not useful to humans, there has always been a risk of becoming extinct due to overgrazing by animals, disease, or other natural causes.