Theory of neutral evolution

As molecular biological data gradually accumulated, it began to be clear that some important evolutionary processes occur beyond the direct influence of selection. Molecular biological techniques enabled study of these evolutionary processes. As a consequence, the relevant areas gradually began to penetrate into textbooks on evolutionary biology and thus into the general consciousness of biologists. Neutral evolution was the first to become an object of the interest of evolutionary biologists, i.e. evolution occurring as a consequence of genetic drift. Sewall Wright was the first to study the aspect of random fixation of selectionally neutral traits. However, molecular biology was the first to demonstrate what an important biological phenomenon this actually is. All indications suggest that incomparably more traits become fixed in evolution through genetic drift than through selection. It is true that the most interesting traits, i.e. adaptive structures, are fixed exclusively through natural selection. On the other hand, genetic drift can be of fundamental importance in the formation of biological diversity and possibly also in speciation. The Japanese biologist and geneticist, Motoo Kimura (1924–1994), made the greatest contribution to elaboration of the theory of neutral evolution. It was found in the study of molecular evolution that interactions of drift with selection are of great importance in the evolution of molecular traits. At the present time, this extensive area is the subject of the theory of “almost neutral evolution” (Ohta 1993; Ohta 1996)) and also the theory of genetic draft (Gillespie 2000; Gillespie 2001)).

            Evolutionary drives are another important mechanism that was discovered in direct connection with the development of molecular biology. Research has shown that some alleles are fixed in the population, not because they increase the chances of survival of their bearers in competition with other individuals, but because they are capable of preferentially spreading in the genome of an individual and amongst sexually reproducing organisms, as well as in the gene pool of the population, at the expense of other alleles. Molecular drive was described by Dover (Dover 1986); other types of evolutionary drives have been studied within the context of individual, mostly narrowly oriented studies by a number of authors {5957, 435, 3200, 4530, 8645}, so it is difficult to designate specific persons as the authors of the particular concepts.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more