Severtsov, Aleksei

Born Sept. 11 (23), 1866, in Moscow; died there Dec. 19, 1936. Soviet biologist. Academician of the Academy of Sciences of the USSR (1920) and of the Academy of Sciences of the Ukrainian SSR (1925). Son of N. A. Severtsov.

In 1890, Severtsov graduated from Moscow University, where he had been a student of M. A. Menzbir. He became professor at the University of Iur’ev (now the University of Tartu) in 1899 and at the University of Kiev in 1902. From 1911 to 1930 he was a professor at Moscow University. In 1930, Severtsov played a prominent role in the establishment of a laboratory of evolutionary morphology at the Academy of Sciences of the USSR; the laboratory was reorganized in 1935 as the Institute of Evolutionary Morphology and Paleozoology (now the A. N. Severtsov Institute of Evolutionary Morphology and Animal Ecology of the Academy of Sciences of the USSR).

Severtsov won worldwide recognition with major works dealing with metamerism of the head (1891–1901), the origin of the paired extremities of vertebrates (1900, 1908, 1926), and the evolution of lower vertebrates (1916–27). In his work on phytogeny Severtsov sought to correlate the results of studies in comparative anatomy and embryology with paleontological findings, stressing the need for studying the structure, development, and functional significance of all systems. He proposed that the pentadactyl extremity originated from an extremity having seven to ten rays, which in turn originated from the mul-tiradial fin of ancient fishlike forms.

Severtsov was the founder of evolutionary animal morphology. He clarified biological and morphophysiological progress and regression and founded the study of the types (moduses) of phylogenetic correlations (coordinations) and phylogenetic changes in organs and functions. Severtsov established the basic directions along which biological progress is achieved: aromorphosis and idioadaptation. Aromorphosis is the increase in the metabolic activity of an organism, and idioadaptation is the individual adaptation to the conditions of existence.

Central to Severtsov’s theoretical work was the study of the interrelationships between individual and historical development. He developed the theory of phylembryogenesis, according to which evolution is accomplished through changes in the course of ontogeny. Severtsov summarized the laws of evolution in his monograph The Morphological Laws of Evolution (German edition, 1931; revised and expanded Russian edition, 1939). Severtsov was the founder of the Soviet school of evolutionary morphologists. The Severtsov Prize was established in 1969.