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Randomness in Natural Selection and Species as Islands in a “Vast Sea of Conceivable Arrangements”

Wolf-Ekkehard Lönnig

(Chelonoidis_nigra)_El_Chato_Reserve,_Santa_Cruz_Galapagos_)pic._c.JPG

Editor’s note: Dr. Lönnig is a retired geneticist at the Max Planck Institute for Plant Breeding Research in Germany.

Stephen Meyer and Richard Dawkins have been engaged in a disagreement on randomness in natural selection. How shall we adjudicate it? First, I wrote in an encyclopedia article several years ago on “The Reproductive Powers of Living Beings and the Survival of the Fittest1:

Dobzhansky’s 1937 work Genetics and the Origin of Species is generally viewed as the crystallization point for the origin and growth of the modern synthesis or neo-Darwinian theory of evolution (Lönnig, 1999a). There is hardly a better example to illustrate the key message (and, at the same time, the weaknesses) of the modern theory of natural selection than the following quotation from this pioneering work of Dobzhansky (p. 149):

With consummate mastery Darwin shows natural selection to be a direct consequence of the appallingly great reproductive powers of living beings. A single individual of the fungus Lycoperdon bovista produces 7 x 1011 spores; Sisymbrium sophia and Nicotiana tabacum, respectively, 730,000 and 360,000 seed; salmon, 28,000,000 eggs per season; and the American oyster up to 114,000,000 eggs in a single spawning. Even the slowest breeding forms produce more offspring than can survive if the population is to remain numerically stationary. Death and destruction of a majority of the individuals produced undoubtedly takes place. If, then, the population is composed of a mixture of hereditary types, some of which are more and others less well adapted to the environment, a greater proportion of the former than of the latter would be expected to survive. In modern language this means that, among the survivors, a greater frequency of carriers of certain genes or chromosome structures would be present than among the ancestors…

For agreement on and further documentation of the principle of natural selection, see the group of authors cited above, beginning with Bell (1997). However, in the 1950s, French biologists, such as Cuénot, Tétry, and Chauvin, who did not follow the modern synthesis, raised the following objection to this kind of reasoning (summed up according to Litynski, 1961, p. 63):

Out of 120,000 fertilized eggs of the green frog only two individuals survive. Are we to conclude that these two frogs out of 120,000 were selected by nature because they were the fittest ones; or rather — as Cuenot said — that natural selection is nothing but blind mortality which selects nothing at all?

Similar questions may be raised for the 700 billion spores of Lycoperdon, the 114 million eggs multiplied with the number of spawning seasons of the American oyster, for the 28 million eggs of salmon and so on. King Solomon wrote around 1000 BC: “I returned, and saw under the sun, that the race is not to the swift, nor the battle to the strong,…but time and chance happeneth to all of them” (KJV 1611).

If only a few out of millions and even billions of individuals are to survive and reproduce, then there is some difficulty believing that it should really be the fittest who would do so. Strongly different abilities and varying environmental conditions can turn up during different phases of ontogenesis. Hiding places of predator and prey, the distances between them, local differences of biotopes and geographical circumstances, weather conditions and microclimates all belong to the repertoire of infinitely varying parameters. Coincidences, accidents, and chance occurrences are strongly significant in the lives of all individuals and species. Moreover, the effects of modifications, which are non-heritable by definition, may be much more powerful than the effects of mutations which have only “slight or even invisible effects on the phenotype” (Mayr 1970, p. 169, similarly 1976/1997; see also Dawkins, 1995, 1998), specifying that kind of mutational effects most strongly favored for natural selection and evolution by the neo-Darwinian school. Confronting the enormous numbers of descendants and the never-ending changes of various environmental parameters, it seems to be much more probable that instead of the very rare “fittest” of the mutants or recombinants, the average ones will survive and reproduce.

Second, combine these points with Dawkins’s statement in his book Climbing Mount Improbable on species as islands “in a vast sea of conceivable arrangements” (1996, p. 88-89):

Organisms are extremely complicated and sensitively adjusted pieces of machinery. If you take a complicated piece of machinery, even one which is not working all that well, and make a very large, random alteration to its insides, the chances that you will improve it is very low indeed.

…A small random change may improve it; or, if it makes matters worse, it will still not move too far from the correct arrangement. But a very large random change has the effect of sampling the gigantic set of all possible rearrangements. And the vast majority of all possible arrangements are wrong.

…Turning to living creatures, I wrote in The Blind Watchmaker that however many ways there may be of being alive, it is certain that there are vastly more ways of being dead…If you think of all possible ways of arranging the bits of an animal, almost all of them would turn out to be dead; more accurately they’d mostly never be born. Each species of animal and plant is an island of workability set in a vast sea of conceivable arrangements most of which would, if they ever came to existence, die” [italics by Dawkins].

Combining these two points — (1) the questions on natural selection and (2) species as islands “in a vast sea of possible arrangements” — one may indeed raise the question of whether the origin of all the forms of specified and irreducible complexity continually detected in species and higher systematic categories are really explained by mutation and selection alone.

As for further questions on natural selection (to what extent natural selection really exists in nature, population genetics, the neutral theory, selection limits, the law of recurrent variation, Popper’s recantation and several further intriguing topics), please see the article referred to below.

References:

(1) Lönnig, W.-E. (2001): Natural Selection. Pp. 1008-1016 in W. Edward Craighead and Charles B. Nemeroff (eds.): The Corsini Encyclopedia of Psychology and Behavioral Science. Third Edition (2001), Volume 3, pp. 1008-1016. John Wiley & Sons, New York. See also here.

Image: Galápagos tortoise, by David Adam Kess [CC BY-SA 4.0], via Wikimedia Commons.