26 



NA TURE 



{Nov. 12, 1885 



''EVOLUTION WITHOUl NATURAL 

 SELECTION " 



Evolution without Natural Selection; or, The Segrega- 

 tion of Species without tlie Aid of the Darwinian 

 Hypotliesis. By Charles Dixon. (London : R. H. 

 Porter, 1885.) 



^''HE title of this little book is misleading. Far from 

 offering any account of evolution without natural 

 selection, the author habitually ascribes to natural selec- 

 tion the lion's share of the work, only reserving a few odds 

 and ends of small detail as results ascribed by him to 

 other agencies. Such odds and ends have reference 

 almost exclusively to minute differences of coloration in 

 allied species of birds — the argument being that these 

 differences are too minute to count for anything in the 

 struggle for existence, and therefore cannot have been 

 due to survival of the fittest. Now, although Mr. Dixon 

 has presented in a brief and very readable form a con- 

 siderable number of most interesting facts upon this 

 head, they cannot be said to have any bearing upon the 

 Darwinian hypothesis. For even if it were conceded, 

 for the sake of argument, that all the cases given of slight 

 variation in allied species are without utilitarian signific- 

 ance (although this would be a large concession), we 

 should still be well within the four corners of Darwinism. 

 It is the very essence of the Darwinian hypothesis that 

 it only seeks to explain the apparently purposive varia- 

 tions, or variations of an adaptive kind ; and, therefore, 

 if any variations are taken to be non-adaptive, ex liypo- 

 tlicsi they cannot have been due to natural selection. 

 ISut as such variations are, even upon the showing of our 

 author himself, for the most part rare and always trivial, 

 they may be freely presented to the anti-Darwinians 

 without any loss to Darwinism. Indeed, Mr. Darwin 

 himself has clearly recognised the occurrence of such 

 trivial specific characters, and observes that if they are 

 '■ really of no considerable importance in the struggle for 

 life, they could not be modified or formed through 

 natural selection." But it is no part of the theory of 

 natural selection that it should necessarily occupy the 

 whole field of possible causation in the genesis of species. 

 It is surely enough if it be taken to explain all cases of 

 adaptation; and this, if we understand him aright, Mr. 

 Dixon is prepared to allow. Thus, for example, he 

 says : — " We can therefore understand how the modifica- 

 tions which many species have undergone, through clim- 

 atic and other causes, have been taken advantage of 

 when they began to he of service ; although at the time 

 the modifications took place they were not of the slightest 

 use I " The note of admiration here seems to imply, in 

 accordance with the whole tone of his book, that the 

 writer considers this view to be in some way an important 

 emendation of Darwinism. But, in point of fact, it is 

 Darwinism pure and simple. For Darwin is most express 

 in affirming that natural selection cannot be supposed 

 the original cause of variation, being only called into 

 play when the variations, as Mr. Dixon says, begin to 

 be of service. What these original causes of variation 

 may be is a distinct question, and one which it remains 

 for the future to answer. For, as we shall immediately 

 proceed to show, Mr. Dixon has not Ijeen successful in 

 furthering the solution. 



The influence on which he chiefly relies is that of iso- 

 lation, and he has gathered a number of interesting facts 

 whereby to justify his opinion. It is needless to say that 

 this opinion also is quite in harmony with Darwinian 

 teaching ; for when a section of a species is geographic- 

 ally isolated, the constituent members of it are virtually 

 confined to a world of their own whereon to begin a new 

 course of history, and being thus cut off" from interbreed- 

 ing with the main stock, there is nothing remarkable in 

 the fact that, under sii^h circumstances and in some cases, 

 the history of the isolated section should not run perfectly 

 parallel with that of the main stock. This, indeed, is 

 Mr. Dixon's own view, and we should have no criticism 

 to offer upon it, if, on the one hand, he did not present it as 

 anti-Darwinian, and if on the other hand he had been more 

 clear in distinguishing between a condition and a cause. 

 He everywhere speaks of isolation as the cause of minute 

 specific characters ; whereas it is obvious that at best it 

 can only be the condition to the operation of causes, the 

 nature of which it apparently does not occur to him to 

 suggest. 



Another agency invoked by the writer as a direct cause 

 of variation is climate. But here again his views cannot 

 be said to be anti-Darwinian, save in so far as they 

 appear to err on the side of exaggeration. For even Mr. 

 Spencer — who, by the way, ought to have been men- 

 tioned by Mr. Dixon as having long ago argued in 

 favour of such direct causes of variation — would scarcely 

 go so far as to attribute to climatic influences variations 

 of a protective kind. This, however, is done by Mr. 

 Dixon ; but he maintains a judicious silence upon the 

 closely-allied topic of mimicry. Yet such remarks as the 

 following apply with even more force to the facts of 

 mimicry' than to those of protection : — " If the colour was 

 donned from protective motives, to escape some special 

 enemy, it seems impossible not to believe that the species 

 would have become exterminated long before the pro- 

 tective colour reached a beneficial degree of development.' 

 Does Mr. Dixon believe that the exquisite details of form 

 and colour whereby an insect is made to resemble a leaf 

 can reasonably be ascribed to climatic influences ? If not, 

 what becomes of his argument touching the much less 

 remarkable cases of protective colouring ? 



There still remains one other criticism of a general 

 kind which it seems impossible to avoid making. On 

 p. 7 it is said : " Natural Selection is probably the most 

 potent agent in the evolution of new species only at such 

 times when the earth is undergoing violent changes. . . . 

 We can conceive how, as soon as violent changes once 

 more pervade the world, the struggle for life will be 

 infinitely greater than it is now. Then species will be 

 matched against species, race against parent form, or 

 race against race ; all Nature will be thrown into a kind 

 of chaos ; and then Natural Selection will adjust the 

 disordered balance," &c., &c. 



Now, this passage, which appears to be intended as 

 conciliatory to Darwinism, is the only really anti- 

 Darwinian passage in the essay. For not only are the 

 views expressed by it in direct contradiction to the now 

 universally-.accepted teaching of uniformitarianism, but 

 they equally run counter to the emphatic contention of 

 Darwin, that the great merit of his theory consists in its 

 agreement with that teaching. Not in chaos or in 



