The Direct Aktion Of Enviroment and Evolution [Unduh pdf]

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Ebook Title : The Direct Aktion Of Enviroment and Evolution

Ebook Thickness	: 25 Page
Language	: English

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When Darwin was leaving England for a cruise in the Beagle he was warned by one of his friends that he must not let himself be influenced by what he might see in Nature in favour of the variability of the species. ‘None of these French theories,’ he was told (I quote from memory), which meant: ‘Nothing of the ideas of Buffon, Lamarck, and Geoffroy Saint-Hilaire, according to whom the direct action of the ever-changing conditions of life originated the infinite variety of vegetable and animal forms peopling the globe.'

Darwin carefully observed Nature and studied its life, and he felt the spell of ‘the French ideas.’ And both in 1842, when he wrote a first sketch of his conceptions about evolution,[5] and in 1859, when he published his Origin of Species, where he insisted upon the dominating part played in the evolution of new forms by Natural Selection, he indicated at the same time the part that is played by the Buffon-Lamarckian factor the Direct Action of Environment. Lyell even reproached him with the ‘Lamarckism’ of the Origin of Species. However, at that time Darwin postponed a thorough discussion of the subject to a work on Variation, for which he was collecting materials. Only nine years later he published the first part of this work; but in the meantime, already in the third edition of the Origin of Species, he felt bound to introduce important matter dealing with the direct action of environment. His great work on Variation, as well as the sixth edition of Origin of Species, contained, in fact, a straightforward recognition of the importance of the environment-factor in the evolution of new species. He did not hesitate to admit that in certain cases ‘definite’ and ‘cumulative’ variation under the influence of environment could be so effective for originating new varieties and species adapted to the new environment, that the role of Natural Selection would be

quite secondary in these cases.

The reasons for such a modification of opinion were acknowledged by Darwin himself. In the ‘fifties there were no works dealing on a scientific basis with variation in Nature; while Experimental Morphology, although it had been recommended already by Bacon, was called into existence after the appearance of Darwin’s work. Still, the new data, rapidly accumulated in these two branches of research after 1859, were such as to convince Darwin of the importance of the direct action of environment, and he frankly acknowledged it.