EVOLUTION
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EVOLUTION
tion — that is the survival of the fittest variations —
was supposed to be transmitted and accumulated
through the principle of inlieritance. In this manner
Darwin defined and tried to establish the theory of
natural selection. Long after he had come to Down
he added an important complement to it. The for-
mation of new species implies that organic beings tend
to diverge in character as they become modified. But
how could this be explained? Darwin answered:
Because the modified offspring of all dominant and in-
creasing forms tend to become adapted to many and
highly diversified places in the economy of nature. In
short, according to Darwin, species are continuously
transformed " by the preservation of such variations
as arise and are beneficial to the being under its condi-
tions of life", that is, by the survival of the fittest,
which is to be considered
"not the exclusive", but
the "most important
means of modification".
As his studies and ob- servations progressed, Darwin lost his almost ex- clusive belief in his own theory, as he held it in 1859, and gradually adopted, at least as sec- ondary causes in the origin of species, the Lamarck factor of the inheritance of the effects of use and disuse and the Buriun factor of the direct acti:in of the environment, especially in case of the geographical isolation of species. As to the human species, Darwin was, as early as 1837 or 1838, of the opinion that it was likewise no special crea- tion, but a product of evo- lutionary processes. The numerous facts which, according to Darwin, might be adapted to sub- stantiate his views are contained in liLs work, "The Descent of Man" (1871). As a supplemen- tary work to "The Origin of Species ' ', Darwin published, in 1868, " The Variation of Animals and Plants under Domestication", which contains many valuable facts and theoretical discus- sions concerning variation and heredity. The princi- ple of natural selection Ls certainly a verj' useful factor in removing variations not well adapted to their sur- roimdings, but the action is merely negative. The main point (that is the origin and teleological develop- ment of useful variations) is left untouched by the theory, as Darwin himself has indicated. Moreover, no proof is brought forward that variations must ac- cumulate in the same direction and that the result must be a higher form of organization. On the con- trary, as we shall point out below, the experimental evidence of the post- Darwinian period has failed to substantiate Darwin's claim. It is, however, well to note that Darwin did not wish to ascribe the origin and survival of u-seful variations to chance. That word, he declares, is a wholly incorrect expression which iriorely serves to acknowlcrlge plainly our ignorance of the cause of each particular variation. Later on, it is true, he seems to have abandoned the idea of design. "The old argument", he .says in his "Autobiography" (1870) . . . " fails, now that the law of natural selec- tion has been di.scovered." Similarly, his belief in the existence of God, which was strong in him when he v.— 42
Charles Darw
wrote the "Origin", seems to have vanished from his
mind in the course of years. In 1874 he confessed:
"I for one must be content to remain Agnostic".
Of the nimierous friends of Darwin who contributed so much to the development and spread of his theories, we mention in the first place Alfred Russel Wallace, whose essay on natural selection was road before the Linnaean Society, in London, 1 July, 1858, together with Darwin's first essay on the subject. The main work of Wallace, "Darwinism, an E-xposition of the Theory of Natural Selection with Some of its Applica- tions" (1889), "treats the problem of the origin of species on the same general lines as were adopted by Darwin; but from the standpoint reached after nearly 30 years of discussion " In fact the book is a defence of piu-e Darwinism. Wallace, too, assumed the ani- mal origin of man's bodily structure, but, contrary to Darwin, he ascribed the origin of man's "intellec- tual and moral faculties to the unseen Universe of spirit" (Darwinism). ThomasH. Huxley (IS'JS- 1895) was one of the most strenuous defenders of Darwin's views; his book on "Man's Place in Na- ture" (1863) is a defence of man's "Oneness with the brutes in structure and in substance". Be- sic les ^^'allacc and Hu.xley, there were the geologist Sir t'harles Lyell, the zoologist Sir John Lub- bock, and the botanists Asa Gray and J. D. Hooker, who supported Darwin's theory almost from the beginning. Cjuaticfai^cs and Dana iic(c]iti'.l it in part, but ilrclaicil that there were no arginnents m favour of the animal origin of man. Spencer's views are not very much different from those of Darwin's later years. Natural se- lection is more aptly called by him " the survival of the fittest" (" Principles of Biology", 1898, I, p. 530). Trying to harmonize the Lamarckian and Darwinian factors of evolution, he was among the first to defend the so-called neo- Lamarckian theory, which insists upon the direct in- fluence of the environment and the inheritance of newly acquired characters.
Before we enter upon the last phase in the develop- ment of the evolution idea, it is necessary to devote some space to the extreme defenders of Darwinism in Germany. Ernst Haeckel, of Jena, is in some sense the founder of the science of phytogeny, which seeks at least by way of hypothesis, to determine the genetic relation of past and present species. In 1868 Darwin wrote to Haeckel : " Your boldness makes me some- times tremble ". This refers especially to the phylog- eny, which is in fact an aprioristic structure often contradicted, and at almost no point supported, by experiment and observation. The tetrahedral car- bon atom is; according to Haeckel, the external foun- tain head of all organic life. Through abiogenesis certain most primitive organisms are said to have been formed, such as "moners", which Haeckel described as unicellular beings without structure and without any nuclear differential ion. During ages of vmknown duration these simple masses of protoplasm have been
