The Epigenetic Theory of Evolution (ETE) is one of the modern evolutionary theories based on epigenetic data. The main principles of the epigenetic theory of evolution were formulated in 1987 by M. A. Shishkin on the basis of the ideas of I. I. Schmalhausen and K. H. Waddington [1] . The theory considers a holistic phenotype as the main substrate of natural selection, and selection not only captures useful changes, but also takes part in their creation.
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The currently accepted synthetic theory of evolution (STE) suggests that the primary changes in the body are mutations that cause phenotypic changes, and those, in turn, undergo natural selection, fixing useful mutations and eliminating harmful ones. Unlike STE, the epigenetic theory of evolution postulates the primacy of phenotypic changes and their inverse effect on the genotype .
As is known, the genotype does not have a definite effect on the phenotype. The latter is the result of the combined action of the genotype and environmental conditions. In addition, internal biochemical mechanisms often allow the body to neutralize the effects of adverse mutations, so that a normally functioning organism can develop from an embryo with a potentially harmful mutation. These observations allowed supporters of ETE to suggest that the fundamental influence on heredity is exerted not by the genome , but by the epigenetic system (ES) - a combination of factors affecting ontogenesis .
According to the concept of ETE, the general organization of ES is transmitted from ancestors to descendants, which forms the body during its individual development, and selection leads to stabilization of a number of consecutive ontogenesis, eliminating deviations from the norm ( morphosis ) and forming a stable development trajectory ( creod ).
The evolution of ETE is the transformation of one creode into another under the disturbing influence of the medium. In response to indignation, ES destabilizes, as a result of which it becomes possible to develop organisms along deviating development paths, and multiple morphoses arise. Some of these morphoses receive a selective advantage, and over the next generations of their ES develops a new stable development path, a new creod is formed. In other words, morphoses possessing selective advantages stimulate the occurrence of mutations that genetically fix favorable changes that have arisen in the body.
The problems touched by epigenetic theory are very close to those dealt with by the rapidly developing evolutionary developmental biology in Western countries. Both concepts largely arose independently, but if Shishkin directly points to the work of Schmalhausen, then in the English literature his works are not so well known, although the Evo-Devo concept is largely based on similar principles [2] [3] [4] .
Critique of Theory
Since the field of application of epigenetic theory coincides with that in synthetic theory , STE and ETE can be considered as alternative theories. But at the same time, the methodological approach of these theories is different, and therefore they can be considered complementary. [five]
Notes
- ↑ Shishkin M. A. Individual development and evolutionary theory // Evolution and biocenotic crises. - M .: Science, 1987.
- ↑ Khlebovich V.V. Discrete adaptive norms: mechanisms and role in evolution // Proceedings of the Zoological Institute of the Russian Academy of Sciences. Appendix No. 1. - 2009. - S. 219-231 .
- ↑ Vorobyova E.I. Evo-devo and the concept of evolution of ontogenesis of I.I. Schmalhausen // News of the Russian Academy of Sciences. Biological Series. - 2010. - Issue. 2 . - S. 141-148 .
- ↑ Vorob'eva EI Evo-devo and the II Schmalhausen concept of the evolution of ontogeny // Biology Bulletin. - 2010 .-- T. 37 , no. 2 . - S. 106-113 . - DOI : 10.1134 / S1062359010020032 .
- ↑ Pozdnyakov A. A. Criticism of the epigenetic theory of evolution // Journal of General Biology. - 2009. - T. 70 , no. 5 . - S. 383–395 .