Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.

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Ryuichi Matsuda

Animal Evolution in Changing Environments, with Special Reference to Abnormal Metamorphosis: Bibliographical Excerpts


"Despite some apparent exceptions, it now has to be concluded that an environmentally modified phenotype could become heritable through the process of genetic assimilation, remaining at phase 1 or 2, or 3 or the latter. As I (Matsuda 1982) have discussed, the widely held belief that environmentally modified phenotypes are not heritable (and hence without evolutionary future) is misleading and it must be dismissed. The reason for the prevalence of this belief appears to have been a series of proposals and discoveries of important biological concepts that have confused biologists. Most prominently, the so-called Weismann theory was in accord with the idea of impossibility of inheritance of externally induced phenotypic changes. The theory states that only the germ plasm is continued from generation to generation, and therefore somatic (somatogenic of Weismann) modifications acquired during development by external influence cannot affect the germ plasm, and hence cannot be inherited. Against the possibility of transmission of somatic modification to the germ plasm, Weismann (1892, p. 393) asserted "we should have to assume the presence in all parts of the body a definite track along which somatic variation might be transferred back to the germ cells, in the germ plasm of which it would produce a corresponding change." This assertion was consistent with the Mendelian law of heredity that was discovered soon after, and the two theories together contributed to the development of neo-Darwinism, in which the external (environmental) influence on development is irrelevant to evolution. Further, Weismann's theory was also consistent with the central dogma of modern molecular genetics in which the relationship between the genotype and phenotype (i.e., the DNA to RNA to protein to phenotype sequence) is unidirectional and there is no mechanism by which the process could be reversed, and later repudiations of the "inheritance of acquired characters" (Dobzhansky 1970, Mahr 1976, Ayalo 1977) were based on this dogma. However, in these repudiations, as Matsuda (1982) pointed out, no distinction was made between the kinds of external agents causing modifications. In this connection, it is very important to point out here that Weismann (1892) actually recognized two kinds of somatogenic variations, namely, injuries and functional variations, and the variations depending on the so-called "influence of environment" which included mainly climatic variations. As his discussion shows, his refutation of the "inheritance of acquired characters" applied to the first two categories only. As this work abundantly shows, environmentally acquired characters can become heritable through the process of genetic assimilation, without requiring the reversal of genetic transcription and translation. Weismann found, with regard to the climatic influence, that when the pupae of the German form of a lycaenid butterfly Polymmatus phlaeas was exposed to much higher temperatures, none of the emerged adults resembled the darkest form of southern variety eleus. Further, a reverse experiment was made by subjecting caterpillars of the Naples form to very low temperature in rearing. The result was that none was as light colored as the ordinary German form. From these results Weismann concluded that German and Naples forms are constitutionally (genetically) distinct. Weismann (1892, p.401) said, 'A somatogenic character is not inherited in this case, but the modifying influence--temperature--affects the primary constituents of the wings in each individual, i.e. a part of the soma--as well as germplasm contained in the germ of animals.' Weismann (1892, p. 405) even went so far so to say, "In many animals and plants influences of temperature and environment may very possibly produce hereditary variations." Thus contrary to the prevailing belief, Weismann was a neo-Lamarckist, as Darwin was (1972, p. v.). In 1904 Weismann again referred to P. phlaeas in the same context, although he also referred to cases in which environmental impacts such as nutrition and climatic factors have not affected the germ plasm (e.g., alpine plants, plant galls). In fact, Weismann's theory as a whole was not inconsistent with the Baldwin effect (discussed in Chap. 5). However, what happened later was that his general statement of refutation of the inheritance of acquired characters alone was taken seriously, and it provided a strong theoretical basis for the development of neo-Darwinism." (Matsuda, Ryuichi (1987) Animal Evolution in Changing Environments, with Special Reference to Abnormal Metamorphosis. N.Y.: Wiley Press pp.40-41)

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