If living beings had appeared as a result of an act of creation, then there would be no hormones. In all machines, mechanisms, and devices designed and built by humans, the control circuits consist only of mechanical parts and electrical circuits. Not a single artifact, a product of human activity, has a regulatory system using chemicals that would spread throughout the unit and change the activity of a particular node. But living organisms are a product of evolution. The first living creatures appeared in water, and their vital activity was regulated by chemicals dissolved in the environment, partially penetrating into a living cell and being produced inside this cell. These regulatory substances cannot be called hormones, but the very principle of regulation using substances dissolved in liquids, that is, humoral regulation, appeared simultaneously with the emergence of life on Earth. There were still a billion years left before the appearance of information transmission using neural elements. It should be noted that the division into nervous and humoral regulation is conditional. A nerve impulse is transmitted from one neuron to another and from neuron to executing cell using chemicals that we call transmitters, or mediators. In addition, nerve endings do not fit every cell. The endings of nerve cells “serve” entire groups of cells: a mediator released from the nerve endings spreads through the interstitial fluid. Or, for example, the mediator of the sympathetic nervous system, norepinephrine, is released into the walls of the capillaries of muscle tissue and spreads with the bloodstream, acting as a real hormone. What is the difference between humoral regulation and nervous regulation? Hormones are substances secreted by specialized cells that are distributed through the body through the bloodstream and interact with target cells. The fundamental differences between nervous and humoral regulation become clear. Firstly, the neural signal is directional, but the humoral signal is not. Regulation of the contractile activity of skeletal muscles is possible, of course, only with the help of the nervous system — how else to ensure the subtle movements of our fingers, tongue, lips, vocal cords? But when it is necessary to increase, say, the supply of glucose to all cells of the body, hormones cope with this task remarkably effectively. Secondly, the nervous signal is fast, and the humoral signal is slow. Some environmental changes require an immediate response, while others do not. And thirdly, the humoral signal is long—lasting, while the nervous signal is short-lived. Some environmental changes require persistent changes in the activity of the entire organism or individual systems, and in these cases humoral regulation is more effective than nervous regulation. It should be emphasized that from the fact that neural regulation is much younger than humoral in evolutionary terms, it does not follow at all that evolution is aimed at reducing the role of humoral regulation, in particular the role of hormones, and increasing the role of nervous regulation. Humoral regulation becomes more complicated in the course of evolution. In fish, the same hormone performs many functions, for each of which mammals have developed specialized hormones. In the course of evolution, the number of types of hormone receptors increases and histohematic barriers become more complex. In conclusion, we note that engineering has not yet realized not only the principle of humoral regulation of functions. Many other achievements of evolution have not yet been used in technology. For example, all electrical appliances operate on the principle of “on/off”, zero or one. And in the nervous system of living organisms, there is a process of inhibition. By the way, we appreciate Ivan Mikhailovich Sechenov not for his materialistic views, as is often written in textbooks, but for discovering the process of central inhibition. It can be assumed that the creation of braking circuits will significantly increase the efficiency of cybernetic systems. Author: Dmitry Zhukov, Doctor of Biological Sciences, Associate Professor of Physiology, Senior Researcher at the Laboratory of Comparative Genetics of Behavior at the Pavlov Institute of Physiology of the Russian Academy of Sciences.