Jenkin's nightmare

Jenkin’s nightmare ( “swamping argument” ) is a fundamental objection to Darwin’s theory of the gradual formation of new species by preserving the favorable trait by natural selection , put forward by the English engineer Jenkin . According to him, a useful feature accidentally appearing in an individual individual in a group of organisms ( populations ) will gradually be leveled by crossing with ordinary individuals. This logical difficulty has been overcome with the creation of population genetics .

In Jenkin’s article, the “swamp argument” was intended only to reinforce his erroneous belief that by means of natural (or artificial) selection, any sign can change only to a limited extent. In addition, he argued that after relieving pressure from natural or artificial selection, the population should return to its “natural” state. The “waterlogging argument” was put forward in order to show that a random deviation from the “norm” would not be able to cause changes in the population as a whole.

Content

History

In June 1867, Jenkin's article, The Origin of Species, was criticized in the journal North British Review , criticizing the idea of natural selection as a driving force for evolution ^[1] . The main point of Jenkin’s objection is the absorbing effect of free crosses . To understand its essence, suppose that an individual with a more successful trait appeared in the population than that of existing individuals. But she will be forced to interbreed only with individuals with “normal” characters. Therefore, after several generations, a successful new acquisition will inevitably be swallowed up by the “swamp” of usual signs ^[2] .

... Imagine a white man who was shipwrecked on an island inhabited by blacks ... Our surviving hero may become the king among them; he will kill a lot of black people in the struggle for survival; he will lead a lot of wives and children, while many of his subjects will live single and die single ... The qualities and abilities of our white man will undoubtedly help him live to a very old age, but even his long life is clearly not enough for anyone then one of his descendants in any generation became completely white ... In the first generation there will be several dozen smart young mulattos, whose mind will on average surpass the Negro. It will not surprise us that for several generations the throne will belong to more or less yellow skin ^[Kom. ^1] to the king; but can someone believe that the population of the entire island will gradually turn white or even yellow? ..
In our case, the sign fell into extremely favorable conditions conducive to its preservation - conducive, but still unable to fix and preserve it.
Original text
... Suppose a white man to have been wrecked on an island inhabited by negroes .... Our shipwrecked hero would probably become king; he would kill a great many blacks in the struggle for existence; he would have a great many wives and children, while many of his subjects would live and die as bachelors .... Our white's qualities would certainly tend very much to preserve him to good old age, and yet he would not suffice in any number of generations to turn his subjects' descendants white .... In the first generation there will be some dozens of intelligent young mulattoes, much superior in average intelligence to the negroes. We might expect the throne for some generations to be occupied by a more or less yellow king; but can any one believe that the whole island will gradually acquire a white, or even a yellow population ...? Here is a case in which a variety was introduced, with far greater advantages than any sport every heard of, advantages tending to its preservation, and yet powerless to perpetuate the new variety.
- Fleming Jenkin, “The Origin of Species” (1867) ^[3]

According to Jenkin, a useful trait could be preserved only if it occurred immediately in a large number of individuals and in a short period of time (in one generation). But then the idea of indeterminate and random variability loses its meaning, and one-sided and regular changes come into force ^[4] . Jenkin’s mistake was that the signs fixed by selection do not decrease when crossing, but are transmitted in full (the leveling effect of crossing does not exist), or are not transmitted at all, this is determined by crossing. Skin color in this case is a bad example, as it is a complex set of many mutations. But it prevented him from understanding ideological bias in assessing human races (which was the norm in the 19th century) - in fact, in the territory where the tribe of black Aborigines lives, it is their signs that are best for survival, while a white person will be a carrier of signs unfavorable for the area, in particular, he will suffer from sunburn, and it is also unlikely that he will be able to survive in an alien cultural environment.

Having familiarized himself with Jenkin’s objections, Darwin considered that their correctness “can hardly be questioned” ^[2] and called them “Jenkin’s nightmare”. In a letter to his friend the botanist Joseph Hooker dated August 7, 1869, Darwin wrote about Jenkin’s article: “You know, I felt very humiliated when I finished reading the article” ^[5] .

In the sixth edition of the Origin of Species , Darwin was forced to make a whole series of fundamental changes of a pro-Alaric character: increasing the role of a certain variability, recognizing its appearance immediately in a large number of individuals ^[2] , recognizing the great importance of the inheritance of acquired characters, etc. ^[1] ^[6]

Alfred Bennett's Objections

In 1870, in the journal Nature , an article was published by the first assistant editor of the journal, botanist Alfred William Bennett , entitled "Theory of Natural Selection from a Mathematical Point of View" ^[7] , which expressed ideas similar to Jenkin’s ideas. Their essence was as follows. Suppose that to obtain a useful trait requires 10 generations, and in each trait can be changed in 20 ways. In this case, to find a useful trait, it is necessary to sort out 20 ¹⁰ individuals. Let the number of individuals in the population not exceed 10 ⁶ . In this case, for the formation of a new trait, 10 ¹³ individuals, or 10 ⁷ generations, will be needed. Consequently, natural selection cannot be effective as a factor in the formation of new species.

It should be noted that Jenkin’s objections were based on a continuous theory of heredity ^[2] . The discovery of the discreteness of the hereditary material allowed us to overcome Jenkin’s nightmare. Genetics has shown that the gene of the trait may not undergo natural selection while in a recessive state, however, new problems have also been discovered here by the biologist Haldane (see Haldane's dilemma ). Although a new useful trait does not disappear without a trace in the gene pool of a population, its distribution in it can be a very long process, and success is not guaranteed at all ^[8] .

According to F. G. Dobrzhansky , S. S. Chetverikov was the first to refute Jenkin’s arguments ^[9] ^[5] .

Formal Expression

\operatorname {Var} (z_{\text{o}})=\operatorname {Var} (z_{\text{m}}+z_{\text{f}})/2={\frac {1}{2}}\operatorname {Var} (z_{\text{parents}}),

{\ displaystyle \ operatorname {Var} (z _ {\ text {o}}) = \ operatorname {Var} (z _ {\ text {m}} + z _ {\ text {f}}) / 2 = {\ frac { 1} {2}} \ operatorname {Var} (z _ {\ text {parents}}),}

^[ten]

where z is an integer conditionally denoting the hereditary "value" of an individual / trait ( Eng. phenotypic value of an individual ): z _m - mother, z _f - father, z _o - descendant; the larger the number, the more useful the attribute. Var ( z ) is the degree of variation of the trait.

In nineteenth-century biology, it was believed that the father’s hereditary material is quantitatively mixed with the mother’s hereditary material, giving rise to a descendant (the theory of fused heredity, blending inheritance ). In other words, the heredity of the descendant was presented as the " arithmetic mean " of the hereditary material of the father and mother. For example, a plant with a red flower and a plant with white give birth to a plant with a pink flower; a tall father and short mother gives birth to a child of medium height, etc. Jenkin’s calculations show that, if the theory of fused heredity is admitted, the speciation described by Darwin cannot occur, since the random “useful” hereditary material will be eliminated with each generation dilution in unaltered hereditary material.

Neither Darwin nor Jenkin knew about the work of Gregor Mendel (1866), according to which signs are inherited by each individual corpuscle, ^[11] ^[4] ^[12] . The Russian writer and paleontologist Kirill Yeskov , however, thinks differently: “... An exhaustive solution to the paradox formulated by Jenkins (as in the text) , Darwin held in his hands in the most literal sense of the word. This solution, consisting in the discreteness of the hereditary code, was written in black and white in the book of the founder of genetics, Mendel, which Darwin read (this is reliably known) - but did not appreciate it at all ... ” ^[13] . But it should be remembered that Mendel ’s main scientific work “Versuche über Pflanzenhybriden” is not a “book”, as Eskov believes (Mendel was not the author of books), but a relatively small article ^[14] .

Comments

↑ In the 19th century The "yellow" race was seen as a mixture of white and black.

Notes

↑ ¹ ² Yu. V. Tchaikovsky. Evolution. Vol. 22
↑ ¹ ² ³ ⁴ “Jenkin’s Nightmare” (Russian) . Darwin Museum. Date of treatment November 3, 2017. Archived on March 8, 2016.
↑ Jenkin, Fleming . The Origin of Species . North British Review, June 1867, vol. 46. P. 277-318
↑ ¹ ² V.I. Nazarov . Non-Darwin Evolution, p. 65
↑ ¹ ² Takhtadzhyan, Armen . Darwin and the modern theory of evolution // Darwin . The origin of the species. St. Petersburg: Nauka, 2001. p. 519
↑ V.I. Nazarov . Non-Darwin Evolution, pp. 65-66
↑ Bennett, Alfred William. The Theory of Natural Selection from a Mathematical Point of View // Nature. - 1870. - No. 3 (10 November 1870) . - S. 30–33 . - DOI : 10.1038 / 003030a0 .
↑ V.I. Nazarov . Non-Darwin Evolution, p. 66
↑ Dobzhansky Th. Sergei Sergeevich Tchetverikov, 1880-1959 // Genetics, 1967, vol. 55, n. 1. P. 1-3
↑ Bruce Walsh . Lecture 1. Introduction to Mendelian and Molecular Genetics
↑ Did Darwin have a copy of Mendel's paper? "In view of the lack of that evidence, and the circumstances described above, we do not believe that CD had a copy of Mendel's original paper"
↑ Gregor Mendel - biography (unopened) (inaccessible link) . Date of treatment January 11, 2009. Archived February 6, 2009.
↑ Yeskov, K. Yu. Monkey_Process.ru: Evolution mastday! Archived November 7, 2012 on the Wayback Machine // Computerra , April 4, 2006
↑ Mendel, Gregor. 1866. Versuche über Plflanzenhybriden. Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47 ( English translation of Mendel's article )

Links

The full text of the original article by Fleming Jenkin “The Origin of Species” (1867) (in English) // Victorian Texts in the Victorian Web
Scanned pages of Jenkin’s original article in North British Review (1867) // The Complete Works of Charles Darwin Online
Bulmer, Michael. Did Jenkin's swamping argument invalidate Darwin's theory of natural selection? // The British Journal for the History of Science (2004), 37: 3: 281-297 Cambridge University Press
Yu. V. Tchaikovsky . Jenkin’s nightmare, or The Tale of an Engineer Biologists Can't Forget (Unavailable Link) // Chemistry and Life , No. 12, 1978. Page 108-117
D.A. Shabanov. Monkeys, dogmas and “Jenkin’s nightmare” // Computerra , May 11, 2006