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AN INTERESTING AND SIGNIFICANT ADDITION TO EVOLUTIONARY THEORY,
This review is from: The Genetical Theory of Natural Selection (Paperback)
Ronald A. Fisher(1890-1962) was an English geneticist, and one of the founders of population genetics. In the Preface to this 1930 book, he states, "The present book, with all the limitations of a first attempt, is at least an attempt to consider the theory of Natural Selection on its own merits." He articulates a number of principles such as, "The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time."
He states that Natural Selection "affords a rational explanation of structures, reactions and instincts which can be recognized as profitable to their individual possessors. It affords no corresponding explanation for any properties of animals or plants which, without being individually advantageous, are supposed to be of service to the species to which they belong." He further argues, "the widely observed fact that mutations are usually recessive should not lead us to assume that this is true of mutations of a beneficial or neutral character."
However, he also admits, "A mutation, even if favorable, will have only a very small chance of establishing itself in the species if it occurs once only. If its selective advantage is only 1 per cent, it may well have to occur 50 times, but scarcely in mature individuals as many as 250 times before it establishes itself in a sufficient number of individuals for its future prospects to be secure."
He is nevertheless optimistic about the possibilities of variation: "It has not so often been realized how very far most existing species must be from such a state of stagnation, or how easily with no more than one hundred factors a species may be modified to a condition considerably outside the range of its previous variation, and this in a large number of different characteristics." He holds that "In this way it is by no means a supposition to be excluded as impossible that a character first manifested equally by the two sexes should, by the action of natural selection, later become sex-limited in its appearance."
Fisher was also a fervent believer in Eugenics; the last five chapters of the book offer Fisher's thoughts on "Reproduction in relation to social class," "Conditions of Permanent Civilization," "race-mixing," etc. He suggests that the decline of civilizations is related to lowered fertility of the upper classes. These ideas will certainly limit the appeal of his book to a modern reader.