It is known that a long stay of a person or animal on any one diet changes the secretory reaction of the glands to food stimuli, which is due to a change in the functional state of the food center. The food center is the formation of the central nervous system of humans and higher animals that regulates the intake of nutrients into the body and their processing in the digestive tract. The concept of a food center was introduced by I.P. Pavlov on the basis of his theory of conditioned reflexes. The work of the food center, due to the degree of satiety of the body and food irritants, causes the body to move for food, eating and secreting digestive juices. Like the respiratory center, the activity of the food center is periodic and regulated by changes in the chemical composition of the blood, stimuli associated with food intake, and agents acting on the interoreceptors of the alimentary tract, which in turn affect the brain. The so-called "hungry blood", that is, the blood of a person or animal a few hours after eating, excites the activity of the food center, and "well-fed blood", on the contrary, delays this activity. The food center consists of separate groups of cells located in various parts of the central nervous system, including the cerebral cortex. The food center is represented mainly by perceiving nerve cells, it is under the influence of other nerve centers and itself influences their activity. The change in the food base of ancient ancestors gradually led to changes in the digestive, nervous, and immune systems and served as an impetus for the formation of the II signaling system.
Since ancient times, fire has played a huge role in people's lives. Its use by man has become the cornerstone of the formation of a civilization that has its roots in the deepest antiquity. A group of archaeologists led by Francesco Berna from Boston University in the USA concluded in 2012 that man first began to use fire about 1 million years ago. Scientists came to this conclusion after discovering traces of hearths in the Vonderwerk cave in South Africa. Raw food held back the growth of brain volume in the ancestors of protohumans. Nutrient deficiencies in raw plant foods were the main cause of small brains in early human ancestors, confirming the key role of fire and "culinary arts" in human evolution, anthropologists say in an article published in Proceedings of the National Academy of Sciences also in 2012