Download PDF by Alfred Russel Wallace: Contributions to the Theory of Natural Selection: A Series

By Alfred Russel Wallace

ISBN-10: 1108001548

ISBN-13: 9781108001540

Alfred Russel Wallace (1823-1913) is considered the co-discoverer with Darwin of the speculation of evolution. It was once an essay which Wallace despatched in 1858 to Darwin (to whom he had committed his most famed ebook, The Malay Archipelago) which impelled Darwin to post a piece of writing on his personal long-pondered conception concurrently with that of Wallace. As a vacationing naturalist and collector within the a long way East and South the USA, Wallace already vulnerable in the direction of the Lamarckian concept of transmutation of species, and his personal researches confident him of the truth of evolution. at the e-book of at the beginning of Species, Wallace grew to become one in every of its so much well-known advocates. This moment, corrected, variation (1871) of a chain of essays released in e-book shape in 1870, indicates the advance of his considering evolution, and emphasises his admiration for, and help of, Darwin's paintings.

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Now, the hypothesis of Professor Forbes is essentially one that assumes to a great extent the completeness of our knowledge of the whole series of organic beings which have existed on the earth. This appears to be a fatal objection to it, independently of all other considerations. It may be said that the same ob- THE INTRODUCTION OF NEW SPECIES. 23 jections exist against every theory on such a subject, but this is not necessarily the case. The hypothesis put forward in this paper depends in no degree upon the completeness of our knowledge of the former condition of the organic world, but takes what facts we have as fragments of a vast whole, and deduces from them something of the nature and proportions of that whole which we can never know In detail.

The same causes continuing in action, the parent species would next suffer, would gradually diminish in numbers, and with a recurrence of similar unfavourable conditions might also become extinct. The superior variety would then alone remain, and on a return to favourable circumstances would rapidly increase in numbers and occupy the place of the extinct species and variety. Superior Varieties will ultimately Extirpate the original Species. The variety would now have replaced the species, of which it would be a more perfectly developed and more highly organized form.

Variations in unimportant parts might also occur, having no perceptible effect on the lifepreserving powers; and the varieties so furnished might run a course parallel with the parent species, either giving rise to further variations or returning to the former type. All we argue for is, that certain varieties have a tendency to maintain their existence longer than the original species, and this tendency must make itself felt; for though the doctrine of chances or averages can never be trusted to 38 ON THE TENDENCY OF VARIETIES TO DEPART on a limited scale, yet, if applied to high numbers, the results come, nearer to what theory demands, and, as we approach to an infinity of examples, become strictly accurate.

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Contributions to the Theory of Natural Selection: A Series of Essays by Alfred Russel Wallace

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