Epigenesis


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Related to Epigenesis: Epigenetics

epigenesis

[‚ep·ə′jen·ə·səs]
(embryology)
Development in gradual stages of differentiation.
(geology)
Alteration of the mineral content of rock due to outsideinfluences.

Epigenesis

 

(geology), various natural changes in sedimentary rocks after their formation. The term was proposed in 1901–06 by the German geologists R. Beck and R. Stelzner.

In 1940 the Soviet geologist L. V. Pustovalov used the term “epigenesis” for the stage of lithogenesis immediately following diagenesis (seeDIAGENESIS and LITHOGENESIS). In 1957, N. B. Vas-soevich, supported by N. M. Strakhov, N. V. Logvinenko, and others, demonstrated that the term “epigenesis” is the antonym of “syngenesis” and is one of the loosely used terms; it is used to denote any secondary changes in sedimentary rocks, both cata-genetic and supergene changes (seeCATAGENESIS and SUPERGENE PROCESSES). V. N. Kholodov classified (1970) the processes associated with the action of infiltrating mineralized waters and gas emanations on sedimentary rocks as epigenesis.

Epigenesis leads to the formation of a special group of epigenetic deposits, which are most characteristic of the radioactive, nonferrous, and rare-earth metals.

REFERENCES

Vassoevich, N. B. “O terminologii, primeniaemoi dlia oboznacheniia stadii i etapov litogeneza.” In Geologiia i geokhimiia, vol. 1 (7). Moscow, 1957.
Strakhov, N. M. Osnovy teoriilitogeneza, vol. 1. Moscow, 1960.
Kholodov, V. N. “O terminakh, primeniaemykh pri izuchenii vtorichnykh izmenenii osadochnykh porod.” Lilologiia i poleznye iskopaemye, 1970, no. 6.

Epigenesis

 

the theory that the embryonic development of an organism is a process of successive new formations.

Epigenesis opposes the theory that various primordial structures are present in the sexual cells of the embryo. The conflict between the supporters of epigenesis and those of preformation has existed throughout the history of biology. Some scientists— including Aristotle, W. Harvey, J. Blumenbach, and H. Driesch—defended epigenesis from an idealistic vitalist standpoint. Others—including R. Descartes, P. L. M. de Maupertuis, G.-L. L. de Buffon, and C. F. Wolff—defended the theory from a mechanist-physical standpoint. The theory that prevailed in a given era was determined by the level of knowledge about fertilization and embryogeny. The widespread acceptance of epigenesis in the middle of the 18th century, due mainly to the work of C. F. Wolff, contributed to the progress of embryology.

Advances in cytology during the 1870’s and 1880’s gave rise to many theories of heredity that rejected epigenesis. The conflict between epigenesis and preformism was especially acute with respect to the mechanics of development. The development of genetics led to the final rejection of the theory of pure epigenesis. The primitive concept of development as a process of complete new formation dependent solely on external or nonphysical factors gave way to the modern theory of genetic information that determines the patterns of ontogeny. However, the actual development of an organism is subjected within the limits of the norm of reaction to greater or lesser change under the influence of internal and external factors. In the light of these ideas, attempts at substantiating epigenesis from the standpoint of cybernetics by W. M. Elsasser and others have proved futile. The assumption of a dualism between preformed molecular-biological genetic structures and supposedly exclusive epigenetic processes of development is equally unacceptable. Modern biology regards the realization of hereditary information in the development of an organism as a single interdependent process.

REFERENCES

Gaisinovich, A. E. K. F. Vol’f i uchenie o razvilii organizmov: [V sviazi s obshchei evoliutsiei nauchnogo mirovozzreniia]. Moscow, 1961.
Apter, M. Kibernetika i razvitie. Moscow, 1970.
Davidson, E. Deistvie genov v rannem razvilii. Moscow, 1972. (Translated from English.)

A. E. GAISINOVICH

References in periodicals archive ?
Personajes de la importancia de Charles Bonnet, Albrecht von Haller (que abandono la epigenesis por el preformacionismo) o Lazaro Spallanzani abrazaron esta filosofia embriologica.
Evolution by epigenesis: farewell to Darwinism, neo- and otherwise.
(15) According to the theory of epigenesis, which is one of two classical biological doctrines, an organism develops, right from the embryonic stadium, through a successive differentiation of new parts.
Endosymbiosis in sponges: relevance for epigenesis and evolution.
They are weak on cognition, and perhaps in combining notions of self-organization and epigenesis.
noted that such bio-inspired systems can be partitioned along three axes, corresponding to the three processes mentioned previously: phylogeny (evolution), ontogeny, and epigenesis (learning); they dubbed this the POE model.
In 1852, Spencer published "The Development Thesis" and "A Theory of Population," the former denying special creation (and advocating evolution) and the latter principally famous for his use of the expression "survival of the fittest." In "On Manners and Fashion" (1854), he first used the term "evolution" as a means of transcending the biological denotation of words like "epigenesis" and the "anthropocentric meaning" of words like "progress." The first edition of Principles of Psychology (1855) asserted that "life under all its forms has arisen by a progressive, unbroken evolution; and through the immediate instrumentality of what we call natural causes." While Spencer continued to work out evolutionary ideas that he began to formulate in the 1 840s, he still lacked a synthesis.
first exhibits in 1919 what turns out to be the most compelling piece of circumstantial evidence regarding her epigenesis, given the significance of that year in the history of rocket science.
Did Akenside extend his medical studies of embryology into an ontological theory, or did he embrace an embryological theory of epigenesis, in opposition to the dominant theory of preformationism, because it was consistent with his prior theological commitments?
Preformation was the rival explanation of generation to epigenesis, by which the parts of the fetus grew gradually during pregnancy.
To this end, along with a whole series of refashionings of old terms such as epigenesis, co-evolution or reification, they straightaway offer their own brand new word, culturgens: "a device of behaviors, mental facts [mentifacts], and manufactured objects [artifacts], together designated culturgens (from the Latin cultura, culture, geno produce, pronounced kul'tur jens)."(37) Clearly, the authors prefer this word to the terms already forged by colleagues to designate more or less the same thing.
Against this preformationist view and its powerful clerical support, Buffon proposed his own, empirically based theory that, if not a complete account of epigenesis (the assembly of the embryo from substances in the fertilized egg), was nevertheless a rational and courageous step toward it.