What About Natural Selection?

Our purpose is to discuss: (1) The difference between evolution and nat­ural selection; (2) the place of natural selection in nature; (3) its relation to creationism.

By HAROLD W. CLARK, Professor of Biology, Pacific Union College

Because Darwin propounded the idea that natural selection was the principle agent in the evolution of living things, many have drawn the conclusion that natural selection does not exist in reality, but only in the imaginations of the evolutionists. Our purpose is to discuss:

(1) The difference between evolution and nat­ural selection ; (2) the place of natural selection in nature ; (3) its relation to creationism. In the first place, what is natural selection? Al­most any biology textbook will give a good definition. Here is what one popular author says :

"Every living species is continually producing a multitude of individuals many more than can all survive, varying more or less among themselves and all competing against each other for food and a place in the sun. On the whole, nature will let the better fitted ones live more abundantly, and she will kill off the less happily constituted. The weaker will go by the wall; they will not breed so much ; the stronger and their offspring will prevail."

When Darwin published his "Origin of Spe­cies" in 1859, it was bitterly attacked by op­ponents and ardently supported by friends. Many, both friends and foes, confused natural selection with evolution, and this confusion con­tinues even in our own day. We need to study the problem carefully and dispassionately to see whether we can separate the facts from unwarranted inferences.

"Darwin did not initiate the doctrine of organic evolution. But by careful and scientific procedure, he persuaded the scientific world, once and for all, that many diverse organic forms are of common descent and that species are inconstant and in some cases impossible of definition. Moreover, he di­rected scientific attention to the occurrence of vari­ation, to its persistence, and to the question of its origin and its fate."2

"Despite its [Darwin's book] great value and stimulating character and despite the conviction that it carried, its arguments are frequently fallacious. It often confuses two distinct themes. On the one hand there is the question whether living forms have, or have not, an evolutionary origin. On the other hand is the suggestion that natural selection is the main factor in evolution. These themes can be and should be discussed independently. In the 'Origin' they are inextricably confused."

It is principally against natural selection as an evolutionary agent, not against natural se­lection itself, that most scientific argument has been directed. Perhaps the clearest statement of the problem has been made in the following words :

"I may challenge the adherents of the strictly Darwinian view, which we are discussing here, to try to explain the evolution of the following features by accumulation and selection of small mutants : hair in mammals, feathers in birds, segmentation of arthropods and vertebrates, the transformation of the gill arches in phylogeny, including the aortic arches, muscles, nerves, etc.; further, teeth, shells of mol­lusks, ectoskeletons, compound eyes, blood circula­tion, alternation of generations, statocysts, ambula­cral system of echinoderms, pedicellaria of the same, cnidocysts, poison apparatus of snakes, whalebone, and,' finally, primary chemical differences like hemo­globin, hemocyanin, etc. Corresponding examples from plants could be given."

Goldschmidt's challenge gives added signifi­cance to the statements of Dewar, who claims:

"It may be held that each kingdom originated is an independent creation, or that each phylum, or class, or order, or family, or genus, is an independent cre­ation, which may have undergone differentiation or evolution since its origin."5

To these points we might add one from another eminent authority.

"Evolution and natural selection are probably to a great extent independent. . . . Evolution goes on in what one may call the downward direction and from family to variety. . . . The family, consisting probably of one genus and one species, is probably first created"6 and differentiates downward into fur­ther genera and species.

Only a brief analysis of these statements is necessary to show that :

I. Natural selection is not synonymous with evo­lution.

2. Natural selection cannot account for the major groups of plants and animals.

3. It is scientific to believe in the creation of these major groups.

4. Differentiation within such major groups as the family may produce genera and species, and this process is what has popularly been termed "evolu­tion."

Where, then, does natural selection play its real role in nature, if not in "long-range evo­lution," or the origin of major groups? Dob­zhansky, in his "Genetics and the Origin of Species," gives several examples, among which we might note:

1. Fumigation of red scale in citrus orchards in California, which must be increased in degree bcause of the increasing resistance of the pest to the poison gas.

2. Similar methods in the control of the codling moth in various parts of the country.

3. Changes in resistance of wheat to rust.

4. Survival of races of ladybird beetle due to color changes.

5. Adaptation of plants to different levels in the Sierra Nevada Mountains.

6. Adaptive values of certain sea-cliff and sand-dune species.

7. Variation in local races of dandelions which enabled them to resist climatic changes.

8. Relation between pelage of pocket mice and the color of the soil.

9. Adaptation of fruit flies to the climatic condi­tions in different parts of the world.

10. Relation between physiological reactions of certain marine forms and the temperature of the waters.'

These are only a few of the examples cited. Anyone reading the chapter "Selection" will be convinced of the reality of natural selection. Many other cases could be given. It was in the light of these facts that I recently made the following statement:

"It is one thing to observe change in color, size, etc., but an entirely different matter to postulate changes in body form, structure of vital organs, and the like, sufficient to produce new types of animals. This latter kind of change is necessary if the Dar­winian theories are to be applied to the origin of new types."'

It would seem quite evident from these -var­ious citations that while natural selection can have no place in the origin of the major groups, it may have a very important place in separa­tion of mutations that may result in the pro­duction of smaller groups such as species and subspecies.

Let us not waste our energies trying to deny one of the most obvious scientific truths ; rather let us realize natural selection does play a part in nature. We can show quite conclusively from good authority that it is insufficient to explain the major trends of "evolution," but is operative only in the smaller groups of plants and animals. By so doing we shall avoid the scientific error that comes from attempting to deny the obvious. On the other hand, we may turn the tables and challenge the evolutionist to show why the creationist viewpoint may not be as readily accepted as that of the evolutionist.

References

1 Wells, Huxley, and Wells, "The Science of Life" (1934), P. 429.

2 C. Singer, "The Story of Living Things" (1931), p. 297.

3 Id., p. 298.

4 R. Goldschmidt, "The Material Basis of Evolu­tion" (9940), p. 6.

5 D. Dewar, "Difficulties of the Evolution Theory" (1931), P. 5.

6 J. C. Willis, "The Course of Evolution" (1940), p. 191.

T. Dobzhansky, "Genetics and the Origin of Species" (2d ed., 1941), PP. 186-222.

8 H. W. Clark, "Genes and Genesis" (1940), p. 50.

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By HAROLD W. CLARK, Professor of Biology, Pacific Union College

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