Pace Two 



EVOLUTION 



February, 1928 



How Charles Darwin and Alfred A. Wallace 



Discovered Evolution 



By Alexander Goldenweiser 



ON the 18th of June, 1858, Charles Darwin received a 

 letter from Alfred Russell Wallace, then naturaliz- 

 ing in far-away lands. The letter contained a paper by 

 Wallace "On the Tendency of Varieties to Depart Inde- 

 finitely from the Original Type." On the same day Dar- 

 win wrote to his friend Lyell, the geologist, expressing 

 the fear that he, Darwin, had been "forestalled". 



The fact of the matter was that Darwin himself had 

 for years been interested in the problem the solution of 

 which had come to Wallace in a moment's "flash of 

 insight". And Wallace's flash corresponded to Darwin's 

 own — he also had thought of "natural selection' as the 

 process by means of which new species arose. 



Now Darwin was in a quandary. He hesitated to pub- 

 lish, fearing unfairness to Wallace, but he was not in- 

 different to the prestige and fame which his own findings 

 deserved and were certain to earn. Finally he was pre- 

 vailed upon by his frinds, Lyell, Hooker, the botanist, 

 and Huxley, the biologist, to have both papers presented 

 at a meeting of the Linnaean Society. On July 1st. 1858, 

 a report was read to the Society by its Secretary con- 

 sisting of Wallace's paper, an extract from Darwin's 

 sketch written in 1814 — thus definitely establishing his 

 priority — and part of Darwin's letter to Asa Grey, the 

 naturalist, written in 1857. 



The theory of natural selection was launched on its 

 path which was to prove thorny but ultimately triumph- 

 ant. Darwin went to work at once on his book which was 

 finally off'ered to the public on November 24th, 1859, 

 under the title "The Origin of Species by Means of 

 Natural Selection, or the Preservation of Favoured Races 

 in the Struggle for Life". The full data embodying the 

 results of Darwin's painstaking investigations were not 

 published until eight years later (1868) in his two vol- 

 ume work on "The Variation of Animals and Plants un- 

 der Domestication". Finally in 1871 Darwin followed 

 this up with his "Descent of Man" in which the argu- 

 ment, heretofore including only the lower animals, was 

 extended to man. 



What then was this theory of natural selection, ar- 

 rived at independently by two scientists, one working 

 with wild nature, the other inspired by the same observa- 

 tions but experimenting subsequently with domesticated 

 breeds? 



The initial observation made by Wallace and Darwin 

 was this: They found that species of animals or birds 

 placed by nature in spots of relative isolation, such as 

 islands, while preserving enough similarity to their con- 

 tinental relatives to make their original identity recogniz- 

 able, varied in diff^erent directions thus developing new 

 species. This discovery, certain as a fact but so far in- 

 explicable, disposed of the then prevailing idea of the 

 immutability of species, an idea supported by scientific 

 authority and strongly entrenched in theological dogma. 



Both Darwin and Wallace were now certain of the 

 fact of variation. It remained to discover a mechanism 

 by means of which it could be explained. Darwin's ap- 

 proach was through controlled experimentation, notably 

 with pigeons. By interbreeding slight variants in size, 

 form or coloration, he succeeded in producing a large 

 variety of new forms, which, when subsequently mated 

 with individuals of the same peculiarities, proved to 

 breed true, that is to preserve the recently acquired traits. 

 Here Darwin was the selecting agency. The problem re- 

 mained unsolved so long as no corresponding principle 

 was found which would operate with similar results in 

 nature. 



While continuing his experiments and pondering over 

 the results Darwin received a hint from Malthus' famous 

 essay "On Population" in which Malthus argues that 

 whereas population increased in a geometrical ratio, food 

 supply increased in an arithmetical ratio. A situation 

 was therefore found to arise in which not enough food 

 would be available for all the hungry mouths. 



In applying this notion to the conditions found in 

 wild nature Darwin finally hit upon the idea that wild 

 life in nature was to be thought of as a struggle — a 

 struggle for life, for substance — in which those in some 

 way better adjusted to their environment — "the fittest", 

 the "favored races" — survived, lived longer, left more 

 progeny among whom the traits of size, shape, color, etc., 

 which had favored the parent animals were likely to be 

 represented to the same or even greater extent. The 

 others — the less favored ones — having briefer lives and 

 leaving fewer offspring, ultimately died out. 



In this way it came about, for example, that arctic 

 bears, foxes, or hares developed white coloration which 

 was foreign to their ancestors, that the Bengal tiger who 

 lived in tall grass wears stripes — a protective device de- 

 creasing his visibility — , that the predatory cats — the 

 tiger, leopard, jaguar, panther, wild cat, — have sharp 

 powerful incisors, long fine disappearing claws, and can 

 see at night, that numerous insects are in color or in 

 shape so much like the grass, bark, branch, they live 

 in or on as to be practically invisible, and so on and 

 on through the entire range of animal kingdom. 



It must be noted here that the theory of natural selec- 

 tion took such initial variations for granted and then 

 attempted to account for their propagation by the purely 

 external process of selective survival. But whence the 

 variations? And how account for their inheritance and 

 enhancement? Tlie problem of initial variations Darwin 

 never solved; with the problem of heredity he dealt in 

 his theory of Pangenesis. 



Of this theory, of the reception accorded the hypothesis 

 of natural selection and of the valiant battles fought in 

 its name by Darwin's friend, Thomas H. Huxley, I shall 

 write in the next issue. 



