Evolution And Lamarck: Lamarck: The Theory Of Transformation

Jean Baptiste de Lamarck’s Examples of the Use & Disuse of Organs

Stephen Foster, Ph.D.

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Biology —>J. B. de Lamarck>


In Zoologie PhilosophiqueLamarông chồng argued that khung determined function & that the more an organ is used, the larger it grows: “The frequent use of any organ, when confirmed by habit, increases the functions of that organ, leads to its development and endows it with a size và power which it does not possess in animals which exercise it less” (original emphasis; 216). Decreased use has the opposite effect: “The permanent disuse of an organ, arising from a change of habits, causes a gradual shrinkage và ultimately the disappearance and even extinction of that organ” (original emphasis; 210). Zoologie Philosophique provides examples of these laws of evolution and devolution:

In the teeth of the right-whale, which was supposedly completely destitute of teeth, M. Geoffroy has nevertheless discovered teeth in the jaws of the foetus of this animal. The professor has discovered moreover in birds the groove sầu in which the teeth should be placed, although they are no longer lớn be found there…..The Proteus, an aquatic reptile allied lớn the salamanders, và living in deep dark caves under the water, has….only vestiges of the organ of sight, vestiges which are covered up & hidden in the same way. <213>

We find . . . that the bird of the water-side but which does not lượt thích swimming and is yet in need of going to lớn the water"s edge lớn secure its prey, is continually liable to sink inlớn the mud. Now this bird tries to act in such a way that its toàn thân should not be immersed in the liquid, và thus makes its best efforts to lớn stretch và lengthen its legs. The long established habit acquired by this bird and all its race of continually stretching and lengthening its legs, results in individuals of this race becoming raised as though on stilts, & gradually obtaining long, bare legs, denuded of feathers up khổng lồ the thighs and often higher still. <216-17>

Lamarông chồng is often incorrectly said lớn have sầu claiming that the giraffe grew long legs & neck in order khổng lồ browse the leaves of trees. In reality this was a caricature based on Charles Lyell"s bình luận in volume II of his Principles of Geology. Lamarck actually wrote the following:

It is interesting to observe the result of habit in the particular shape and size of the giraffe (Camelo-pardalis): this animal….is known lớn live in the interior of Africa where the soil is nearly always arid and barren, so it is obliged to live on the leaves of trees and lớn make constant efforts to reach them. From this habit long maintained in all its race, it has resulted that the animals fore legs have sầu become longer than its hind legs, and that its neck is lengthened to such a degree that the giraffe, without standing on its hind legs attains a height of 6 meters (nearly trăng tròn feet).

He discussed the kangaroo in more detail & noted the ways in which different parts of the body toàn thân had either grown or reduced in consequence of habitual use or disuse:

This animal, which carries its young in a pouch under the abdomen, has acquired the habit of standing upright, so as lớn rest only on its hind legs and tail, & of moving only by means of a succession of leaps; during which it maintains its erect attitude in order not to lớn disturb its young. And the following is the result:1. Its forelegs, which it uses very little & on which it supports itself for only a moment on abandoning its erect attitude, have never acquired a development proportional to that of the other parts, & have remained meagre, very short and with little strength.2. The hind legs, on the contrary, which are almost continually in action either for supporting the body toàn thân or for making leaps, have sầu acquired great development and have become very large và strong.3. Lastly, the tail, which is in this case much used for supporting the animal & carrying out its chief movements, has acquired an extremely remarkable thickness & strength at its base.These well known facts are surely quite sufficient khổng lồ establish the results of habitual use on an organ or any other part of animals. <219>

In the same section he described many other examples including the retractable claws of cats, the long necks of geese and some ducks, the positions of eyes on the top of the head in flatfish, the lack of limbs in snakes, the webbed feet of aquatic mammals & birds, & the arms of sloths, many of which were lớn re-appear in Origin of Species and other volumes by Charles Darwin.

Lamarông chồng was aware that the mummified animals which had been studied in Egypt by Geoffroy St. Hilaire during the Napoleonic expedition showed that little or no change had taken place in these species over two or three thousand years, & that this seemed to contradict his case for change.

"I do not refuse to lớn believe sầu in the cthua trận resemblance of these animals with individual of the same species living to-day…..It would indeed be very odd if it were otherwise…..Indeed there is nothing in the observation now cited which is contradictory to the principles which I have phối forth on this subject; or which proves that the animals have existed in nature for all time; it proves only that they inhabited Egypt two or three thousvà years ago; and any man who has any habit of reflection và at the same time of observing the monuments of nature"s antiquity will easily appreciate the import of a duration of two or three thousand years in comparison with it.

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Hence we may be sure that this appearance of the stability of the things in nature will by the vulgar always be taken for reality…….. Everything seems lớn hyên ổn khổng lồ be stable in the planet which he inhabits…. Magnitudes are relative sầu both in space và time: let man take that truth to heart and he will then be more reserved in his judgements on the stability which he attributes khổng lồ the state of things that he observes in nature. <42-43>

He was also aware of the very long duration of geological time:

Every qualified observer knows that nothing on the surface of the earth remains permanently in the same state. Everything in time undergoes various mutations, more or less rapid depending on the nature of the object và the various conditions…… Naturalists who did not perceive sầu the changes undergone by most animals in course of time tried to lớn connect the facts connected with fossils, as well as the commotions known to have sầu occurred in different parts of the earth"s surface, by the supposition of a universal catastrophe which took place on our globe. They imagined that everything had been displaced by it, and that a great number of species then existing had been destroyed.

Unfortunately this facile method of explaining the operations of nature, when we cannot see their causes, has no basis beyond the imagination which created it, and cannot be supported by proof…… in all nature"s works nothing is done abruptly, but that she acts everywhere slowly and by successive stages; and on the other h& that the special or local causes of disorders….can account for everything that we observe on the surface of the earth, while still remaining subject lớn nature"s laws and general procedures. <45, 46>

From these principles he concluded that evolution of species had taken place & that the fossil record provided the necessary evidence to lớn prove sầu it.

Lamarông chồng & Man

Others before Lamarông xã had suggested that mankind và the great apes shared a comtháng ancestor, but he was the first lớn compare the anatomical features of the skeleton of a chimpanzee with that of a human, and in 1815 concluded that they did nội dung a common ancestry. This shocked many at the time, not least Georges Cuvier và most educated people in France và the rest of Europe, who strongly opposed the idea because it undermined Christian teaching on the uniqueness of mankind among mỏi animals. When William Lawrence published very similar views in 1819 in his Lectures on Comparative Anatomy he was forced to lớn withdraw it from sale because of the hostile reaction from those in power who threatened lớn remove sầu hlặng from his posts as a doctor at Bridewell & Bethlem hospitals. His book, which was published many times in the size of pirated editions, was read by medical students at Edinburgh in the 1830s when Charles Darwin attended lectures there. The controversy concerning the comtháng ancestry of mankind & the great apes continued inlớn the middle decades of the nineteenth century when the leading British anatomist Richard Owen clashed with Thomas Huxley, including at the Oxford meeting of the British Association for the Advancement of Science in 1860. The dispute was not resolved until the middle of the 1860s when Huxley và others were able khổng lồ finally prove that the anatomy of the great apes & mankind really did point khổng lồ a comtháng descent from earlier primates.

Lamarông chồng was the first modern scientist to lớn state the theories of the reality và history of evolution và he made an important contribution to lớn the ecological theory on the processes of evolution. It is a comtháng misperception that the theory of evolution is a theory on the process of evolution: it is not because there are many processes which cause & contribute khổng lồ it. According khổng lồ S. Lovtrup, an eminent embryologist: "No other person ever made a greater contribution to lớn the study of evolution" than J. B. Lamarông xã.