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biogenetic law,in biology, a law stating that the earlier stages of embryos of species advanced in the evolutionary process, such as humans, resemble the embryos of ancestral species, such as fish. The law refers only to embryonic development and not to adult stages; as development proceeds, the embryos of different species become more and more dissimilar. An early form of the law was devised by the 19th-century Estonian zoologist K. E. von Baer, who observed that embryos resemble the embryos, but not the adults, of other species. A later, but incorrect, theory of the 19th-century German zoologist Ernst Heinrich Haeckel states that the embryonic development (ontogeny) of an animal recapitulates the evolutionary development of the animal's ancestors (phylogeny).
a principle in living nature; formulated by the German scientist E. Haeckel (1866). It consists in the idea that individual development (ontogeny) is a short and rapid repetition (recapitulation) of the most important stages in the evolution of the species (phylogeny). Facts testifying to recapitulation (for example, the development of gill slits in the embryos of land vertebrates) were known before the appearance of C. Darwin’s evolutionary teachings. However, it was only Darwin (1859) who gave a natural-historical explanation for these facts by establishing that the developmental stages of embryos reproduce ancient ancestral forms. He regarded recapitulation as a fundamental principle of the evolution of the organic world. The theory of natural selection enabled Darwin to explain the contradictory combination of expediency of the structure of organisms and recapitulation of the characteristics of distant progenitors. In 1864 the German embryologist F. Müller reinforced the principle of recapitulation with data on the developmental history of Crustaceans. Two years later, Haeckel formulated the principle of recapitulation as the biogenetic law, at the same time giving a rough picture of Darwin’s concepts. The biogenetic law played an important role in biology; it stimulated evolutionary research in embryology, comparative anatomy, and paleontology.
A sharp and prolonged discussion developed over the biogenetic law. Its opponents either tried to interpret it in the light of mechanism or vitalism or they unconditionally rejected it. The Darwinists, in defending the biogenetic law, strove to deepen its content and to free it of schematism. They criticized the ideas of Haeckel, who erroneously divided the phenomena of embryological development into two unequal groups: palingeneses, which reflect the history of the species; and cenogeneses, which develop as an adaptation of the embryo to environmental conditions and which obscure or “falsify” the palingeneses. Haeckel’s initial notion of the direct order of reproduction of the historical stages of the species in the development of the individual proved to be unsound. It was shown (even by Haeckel himself) that heterochrony, heterotopy, embryonic adaptations, reduction, and other processes profoundly change the course of ontogeny, excluding the possibility of direct recapitulation of ancestral characteristics. The biogenetic law was newly illuminated by the theory of phylembryogenesis of the Russian biologist A. N. Severtsov. Severtsov regarded the phenomenon of recapitulation from the point of view of the principles of the evolution of ontogeny. He evaluated the biogenetic law as a consequence of evolution, which is realized by means of the extension (anabolism) of the terminal stages of ontogeny; he regarded cenogenesis, however, as a lawful path in the evolution of a species and as having a palingenetic character. Despite opinions that the biogenetic law was inapplicable to plants, a number of botanists cited examples of recapitulation in plants. A thorough analysis of the biogenetic law from the botanical standpoint was made by the Soviet scientist B. M. Kozo-Polianskii (1937); he proposed a formulation of the law of recapitulation taking into account the peculiarities of ontogeny and the individuality of plants. The subsequent progress of notions about recapitulation, which confirmed the limitations of Haeckel’s treatment of the biogenetic law, is associated with progress in evolutionary morphology and in experimental embryology and genetics, which are correlated in the teachings of I.I. Shmal’gauzen about the organism as a whole in individual and historical development.
REFERENCESDarwin, C. “Proiskhozhdenie vidov . . . .” Soch., vol. 3. Moscow, 1939.
Müller, F., and E. Haeckel. Osnovnoi biogeneticheskii zakon. Moscow-Leningrad, 1940.
Kozo-Polianskii, B. M. Osnovnoi biogeneticheskii zakon s botanicheskoi tochki zreniia. Voronezh, 1937.
Severtsov, A. N. Morfologicheskie zakonomernosti evoliutsii. Moscow-Leningrad, 1939.
Shmal’gauzen, I. I. Organizm kak tseloe ν individual’nom i isto richeskomrazvitii. Moscow-Leningrad, 1942.
Mirzoian, E. N. Individual’noe razvitie i evoliutsiia. Moscow, 1963.
M. G. IAROSHEVSKII