<p>This article examines the evolution of the principles of symmetry and asymmetry, which are the most fundamental properties of the external and internal structure of metazoans, or multicellular organisms. The evolutionary prerequisites and advantages of the emergence of bilaterally symmetrical animals are grounded in logic, noting that bilateral symmetry is not dominant in the internal structure of the body, and that the structure of internal organs obeys its own laws – structure is determined by function. The increasing asymmetry in the morphophysiological evolution of one vital organ, the heart, ensuring the separation of the flows of highly oxygenated arterial blood and venous blood and leading to the emergence of warm-bloodedness, is demonstrated in detail. It is emphasized that the decisive factor in the evolutionary success of vertebrates is the morphophysiological evolution of the central nervous system, characterized first by the emergence of lateralization and then by functional asymmetry of the cerebral hemispheres. In <i>Homo sapiens</i>–humans – functional asymmetry reaches its maximum development due to the localization of speech centers and auditory-verbal functions in the left hemisphere (for right-handers and most left-handers), which determines its dominance in conscious activity. Data are presented showing that disruption of functional asymmetry of brain, with a leading deficit of right-hemisphere functions, is a key risk factor for the development of various types of deviant or “atypical” behavior.</p>