Certain animals have not evolved to a point where they could survive and remain in good health without killing other animals for food. Genetic composition and habitat are two major factors. Still, when these factors are not obstacles, would these animals have the mental capacity to decide that killing other animals (for food) is wrong and change diets? It seems unlikely. If we humans understand that an animal, if at least, could have a right to life and happiness that we should not compromise and that the majority of us are able to live successfully (and without much trouble) maintaining a vegetarian diet, is it then our duty to? Would killing animals for food be permissible only when it is our only realistic option?