...Since he had at the time the Origin was published no body of experimental evidence to support his theory, he fell back on speculative arguments. The argumentation used by evolutionists, said de Quatrefages, makes the discussion of their ideas extremely difficult. Personal convictions, simple possibilities, are presented as if they were proofs, or at least valid arguments in favor of the theory. As an example de Quartrefages cited Darwin's explanation of the manner in which a titmouse might become transformed into the nutcracker, by the accumulation of small changes in structure and instinct owing to the effect of natural selection; and then proceeded to show that it is just as easy to transform the nutcracker into the titmouse. The demonstration can be modified without difficulty to fit any conceivable case. It is without scientific value, since it cannot be verified; but since the imagination has free rein, it is easy to convey the impression that a concrete example of real transmutation has been given. This is the more appealing because of the extreme fundamental simplicity of the Darwinian explanation. The reader may be completely ignorant of biological processes yet he feels that he really understands and in a sense dominates the machinery by which the marvellous variety of living forms has been produced.
This was certainly a major reason for the success of the Origin. Another is the elusive character of the Darwinian argument. Every characteristic of organisms is maintained in existence because it has survival value. But this value relates to the struggle for existence. Therefore we are not obliged to commit ourselves in regard to the meaning of difference between individuals or species since the possessor of a particular modification may be, in the race for life, moving up or falling behind. On the other hand, we can commit ourselves if we like, since it is impossible to disprove our statement. The plausibility of the argument eliminates the need for proof and its very nature gives it a kind of immunity to disproof. Darwin did not show in the Origin that species had originated by natural selection; he merely showed, on the basis of certain facts and assumptions, how this might have happened, and as he had convinced himself he was able to convince others.
...Evolution, if it has occurred, can in a rather loose sense be called a historical process; and therefore to show that it has occurred historical evidence is required. History in the strict sense is dependent on human testimony. Since this is not available with respect to the development of the world of life we must be satisfied with something less satisfactory. The only evidence available is that provided by the fossils. ...What the available data indicated was a remarkable absence of the many intermediates required by the theory; the absence of the primitive types that should have existed in the strata regarded as the most ancient; and the sudden appearance of the principle taxonomic groups. ...The chronological succession of the fossils is also open to doubt, for it appears, generally speaking, that the age of the rocks is not determined by their intrinsic characteristics but by the succession of the strata. ...
...The modern Darwinian paleontologists are obliged, just like their predecessors and like Darwin, to water down the facts with subsidiary hypotheses which, however plausible, are in the nature of things unverifiable.
...I do not contest the fact that the advent of the evolutionary idea, due mainly to the Origin, very greatly stimulated biological research. But it appears to me that owing precisely to the nature of the stimulus, a great deal of this work was directed into unprofitable channels or devoted to the pursuit of will-o'-the-wisps. I am not the only biologist of this opinion. Darwin's conviction that evolution is the result of natural selection, acting on small fortuitous variations, says Guyenot, was to delay the progress of investigations on evolution by half a century. ...In his great work Growth and Form, D'Arcy Thompson remarked on the stultifying effect of Darwinian theory. `So long and so far as "fortuitous variation" and the "survival of the fittest" remain engrained as fundamental and satisfactory hypotheses in the philosophy of biology, so long will these "satisfactory and specious causes" tend to stay "severe and diligent inquiry," "to the great arrest and prejudice of future discovery."'
A long-enduring and regrettable effect of the success of the Origin was the addiction of biologists to unverifiable speculation. ...
The success of Darwinism was accompanied by a decline in scientific integrity. ...
...This situation, where scientific men rally to the defense of a doctrine they are unable to define scientifically, much less demonstrate with scientific rigour, attempting to maintain its credit with the public by the suppression of criticism and the elimination of difficulties, is abnormal and undesirable in science.
....The doctrine of evolution by natural selection as Darwin formulated, and as his followers still explain it, has a strong anti-religious flavour. ...
This general tendency to eliminate, by means of unverifiable speculations, the limits of the categories Nature presents to us, is the inheritance of biology from The Origin of Species. To establish the continuity required by theory, historical arguments are invoked, even though historical evidence is lacking. Thus are engendered those fragile towers of hypothesis based on hypothesis, where fact and fiction intermingle in an inextricable confusion. That these constructions correspond to a natural appetite, there can be no doubt. It is certain also that in the Origin Darwin established what may be called the classical method of satisfying this appetite. We are beginning to realize now that the method is unsound and the satisfaction illusory. But to understand our own thinking, to see what fallacies we must eradicate in order to establish general biology on a scientific basis, we can still return with profit to the source-book which is The Origin of Species.
W.R. Thompson, Introduction to The Origin of Species (E.P. Dutton & Co., New York, 1956).
