ABSTRACT
It is evident all degrees of food selection exist, from the insect which eats only one species of plant, to the cow which eats almost all green herbs (with some notable exceptions, however), and the slug which also eats most anything. This phenomenon is comparable to the peculiar behavior of some phytophagous insects that reject imported plants, a phenomenon to be explained later, called "xenophobia." Similar food selection patterns exist among all living things. It is exemplified in some species of vertebrates (for example, insectivores, and Galapagos finches) narrowly adapted to various specialized ecological food niches. If the authors think about it, food available to humans depends on geography, climate, and season. Before the diversification of agriculture, the main sources of protein differed greatly among the countries: beef in Europe, sheep in the Middle East and other Arab countries, pork in the Far East, fish in Japan, insects in Thailand, and lizards, snakes, and frogs among Australian aborigenes.
