[The problem of the stability of living systems and its evolutionary and morphofunctional bases]

Stability of the living matter is not only a morphological problem, but also a physiological-behavioral problem. Analysis of data accumulated in this field is the topic of this study. Contradicting the existing assumptions, it has shown that the taxonomic stability is not a casuistic phenomenon, but an important independent and widespread law of evolution providing for conservation without modification of the structures and functions for sometimes tens and hundreds millions of years. This is the first publication of the concept of the material substratum of this phenomenon. The study has established that the stability of the orders of mammals persisting despite the variability of the somatic organs in many representatives, and conservation of this separation even in case of transition into the aquatic habitat are due to the regulating mechanism represented by the nervous system of animals and man. This is, in particular, reflected in the specific structural and physiological mechanisms on the subcortical and cortical levels (visual system and neocortex). The study questions the concept of the origin of mammals from a single root of primary insectivorous ancestors on the basis of the discovered cytoarchitectural differences in the visual system and neocortex, and also the most recent paleontological data. In view of that the author emphasizes the independent principle of cytoarchitectural organization of the above brain formations in each order, and their stable separation during the established paleontological history. This phenomenon is interpreted as a major evidence of the principle of stability in the evolution process.