Alfred russel wallace essay
While he was in the Malay Archipelago, the sale of specimens had brought in a considerable amount of money, which had been carefully invested by the agent who sold the specimens for Wallace. Although Lyell could not agree, he urged Darwin to publish to establish priority.
Although it contained no mention of any possible mechanisms for evolution, this paper foreshadowed the momentous paper he would write three years later. The medallion was unveiled on 1 November Inat the urging of many of his friends, including Darwin, Philip Sclaterand Alfred NewtonWallace began research for a general review of the geographic distribution of animals.
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Now it is clear that what takes place among the individuals of a species must also occur among the several allied species of a group,—viz. I wrote a letter to him in which I said that I hoped the idea would be as new to him as it was to me, and that it would supply the missing factor to explain the origin of species. We have also here an acting cause to account for that balance so often observed in nature,—a deficiency in one set of organs always being compensated by an increased development of some others—powerful wings accompanying weak feet, or great velocity making up for the absence of defensive weapons; for it has been shown that all varieties in which an unbalanced deficiency occurred could not long continue their existence. When two populations of a species had diverged beyond a certain point, each adapted to particular conditions, hybrid offspring would be less well-adapted than either parent form and, at that point, natural selection will tend to eliminate the hybrids. The numbers that die annually must be immense; and as the individual existence of each animal depends upon itself, those that die must be the weakest—the very young, the aged, and the diseased,—while those that prolong their existence can only be the most perfect in health and vigour—those who are best able to obtain food regularly, and avoid their numerous enemies. Our quickly fattening pigs, short-legged sheep, pouter pigeons, and poodle dogs could never have come into existence in a state of nature, because the very first step towards such inferior forms would have led to the rapid extinction of the race; still less could they now exist in competition with their wild allies. It is, as we commenced by remarking, "a struggle for existence," in which the weakest and least perfectly organized must always succumb. Reflect on the enormous multiplying power inherent and annually in action in all animals; reflect on the countless seeds scattered by a hundred ingenious contrivances, year after year, over the whole face of the land; and yet we have every reason to suppose that the average percentage of each of the inhabitants of a country usually remains constant. Both checks probably concur. Pre-Darwinian ideas about evolution It was Darwin's genius both to show how all this evidence favored the evolution of species from a common ancestor and to offer a plausible mechanism by which life might evolve. His family, like many Wallaces, claimed a connection to William Wallace , a leader of Scottish forces during the Wars of Scottish Independence in the 13th century. On the Tendency of Varieties to depart indefinitely from the Original Type. He explained the apparent stability of the human stock by pointing to the vast gap in cranial capacities between humans and the great apes. On the average all above one become food for hawks and kites, wild cats and weasels, or perish of cold and hunger as winter comes on. A pigeon breeder selected individual birds to reproduce in order to produce a neck ruffle.
He provided maps that displayed factors, such as elevation of mountains, depths of oceans, and the character of regional vegetation, that affected the distribution of animals.
He left London in to live with William and work as his apprentice for six years.
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Each new variety or species, when formed, will generally take the place of, and thus exterminate its less well-fitted parent. The most vigorous and healthy males, implying perfect adaptation, must generally gain the victory in their contests. In this way every part of an animals organization could be modified exactly as required, and in the very process of this modification the unmodified would die out, and thus the definite characters and the clear isolation of each new species would be explained. The book was not only a best seller but also one of the most influential scientific books of all time. Wallace also hoped to gather evidence of the transmutation of species. On 18 June , Darwin received the essay from Wallace. Wallace taken in Singapore in In , Wallace returned to England, where he moved in with his sister Fanny Sims and her husband Thomas. A recently discovered mechanism, which is likely to be more important than the others combined, is infections with viruses, which integrate their DNA into their hosts. Why, as a general rule, are aquatic, and especially sea birds, very numerous in individuals? Darwin, and sent to him with the expressed wish that it should be forwarded to Sir Charles Lyell, if Mr. An antelope with shorter or weaker legs must necessarily suffer more from the attacks of the feline carnivora; the passenger pigeon with less powerful wings would sooner or later be affected in its powers of procuring a regular supply of food; and in both cases the result must necessarily be a diminution of the population of the modified species. Lyell who Wallace had never been in contact with was one of the most respected scientists of the time and Wallace must have thought that he would be interested to learn about his new theory because it explained the evolutionary "law" which Wallace had proposed in his paper. Bowler , have suggested the possibility that in the paper he mailed to Darwin, Wallace was not discussing selection of individual variations at all but rather group selection. An origin such as is here advocated will also agree with the peculiar character of the modifications of form and structure which obtain in organized beings—the many lines of divergence from a central type, the increasing efficiency and power of a particular organ through a succession of allied species, and the remarkable persistence of unimportant parts such as colour, texture of plumage and hair, form of horns or crests, through a series of species differing considerably in more essential characters. If now we have succeeded in establishing these two points—1st, that the animal population of a country is generally stationary, being kept down by a periodical deficiency of food, and other checks; and, 2nd, that the comparative abundance or scarcity of the individuals of the several species is entirely due to their organization and resulting habits, which, rendering it more difficult to procure a regular supply of food and to provide for their personal safety in some cases than in others, can only be balanced by a difference in the population which have to exist in a given area—we shall be in a condition to proceed to the consideration of varieties, to which the preceding remarks have a direct and very important application.
This is strikingly proved by the case of particular species; for we find that their abundance in individuals bears no relation whatever to their fertility in producing offspring.
Besides this natural means of selection, by which those individuals are preserved, whether in their egg, or larval, or mature state, which are best adapted to the place they fill in nature, there is a second agency at work in most unisexual animals, tending to produce the same effect, namely, the struggle of the males for the females.
Lyell and Hooker's arrangement relegated Wallace to the position of co-discoverer, and he was not the social equal of Darwin or the other prominent British natural scientists.
This was a stopgap measure until William, his oldest brother, was ready to take him on as an apprentice surveyor.
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