DARWIN'S NATURAL SELECTION.   Term Paper ID:21025 Click to get this paper

Essay Subject: Evolutionist's theory, historical/scientific background (Lamarckianism & Malthusianism, [The Origin of Species], influences, punctuated equilibrium.... More...

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Paper Abstract: Evolutionist's theory, historical/scientific background (Lamarckianism & Malthusianism, [The Origin of Species], influences, punctuated equilibrium. Paper Introduction: More than a century after his death, and four generations after the publication of his chief work, The Origin of Species, Charles Darwin remains possibly the most controversial scientist in the world. His name is inextricably associated with the debate (now a political and cultural one, not a scientific one) that continues to swirl around the theory of evolution, a theory that deeply shook the Western view of humanity and its place in the world. We conventionally speak simply of the theory of evolution, leaving off the explanatory phrase, "through natural selection." At most, perhaps, the general public has heard of "survival of the fittest"--an unfortunate phrase, since fitness in everyday usage is associated primarily with physical conditioning and athletic ability. "Survival of the most suited to its Text of the Paper: The entire text of the paper is shown below. However, the text is somewhat scrambled. We want to give you as much information as we possibly can about our papers and essays, but we cannot give them away for free. In the text below you will find that while disordered, many of the phrases are essentially intact. From this text you will be able to get a solid sense of the writing style, the concepts addressed, and the sources used in the research paper. But the training did notcreate those characteristics in the dog's offspring. The Origin of Species by Means of NaturalSelection. A number ofprominent scientists and other thinkers during the eighteenth century andthe first half of the nineteenth century--among them Charles Darwin'sgrandfather, Erasmus Darwin--had offered more or less detailed theories ofevolution (Clark, 1984, pp. There arevarieties of a given species, subtly adapted to different conditions, thatroutinely interbreed along the boundary between their home territories, butthe mixed varieties tend to remain confined to the boundary area, sincethey are less adapted than either of the base varieties to their respectivehome territories. Population was therefore continuallyoutstripping food supply, and was kept in check only by starvation, or byindirect mechanisms such as war and epidemics. Yet Lamarckianism held out promise tothem, as well. The Great Chain of Life took form during the Middle Ages, based on anintermixture of classical and Biblical ideas. In the faceof such catastrophic events, "natural selection" in the usual sense becomesalmost irrelevant; survival of the catastrophe is more a matter of sheerluck than of suitable adaptation. The principles of geneticselection were not known in Lamarck's day, and indeed were not generallyknown until long after Darwin's, when the pioneering work of Mendel wasrediscovered and disseminated at the turn of the twentieth century. On the other side, Darwin examined variation under domestication todemonstrate that the deliberate selection of breeders could, in fact,produce varieties that were as markedly different from the root stock asthe varieties found in nature. Charles Darwin did not invent the concept of evolution. Lamarckian evolution had only one crucial defect: it was demonstrablynot true (Edey and Johnason, 1989, p. The maturity with which both men handled this awkward situation is apleasant footnote in the history of science (Brackman, 198 ). New York: Times Books.Clark, R. But The Origin ofSpecies attached that brilliant idea to an exhaustive survey of evidence,and that evidence demanded either acceptance of the ideas it supported oran equally thorough effort at refutation. Indeed, we might say that the idea ofevolution was a natural development of a concept, the Great Chain of Life,that went back very far in Western tradition. Within a few decades, evolution through natural selection wasestablished as a fundamental paradigm of biological thought, the centralconceptual organizing principle of the science. Virtue, it seemed, was its own reward, at least inthe next generation. New York: Norton.----------------------- 1 R. Had not successive generations of Europeans strivento acquire--and so pass on to their children--the valor of Crusadingknights, the thrift and industry of Reformation merchants, and thereasoning powers of Enlightenment philosophes? The process through which one species evolved into a distinctlydifferent species was far too gradual to be directly demonstrated. Itwas no longer quite sufficient to say that God, or the vital force,mystically drove life ever-upward. Many scientists, such as Georges Cuvier in France,rejected evolution and the Great Chain of Being alike as quasi-mysticalconcepts having no place in biological science (Appel, 1987). Yet all of thesedevelopments are essentially a superstructure built upon a Darwinianfoundation. Asthe lower branches of the ancient African trees were plucked bare, thelonger-necked ancestral giraffes were more likely to survive than theirshorter-necked cousins, and they handed down the tendency toward long necksto their descendents. (1989). As it was, however, the amassed evidence of The Origin ofSpecies was sufficient to persuade most biologists that this was the keythey had been looking for. If they could be Christianized and taught the virtues ofhard work and self-discipline, their descendents could one day attain theheights Europeans had already scaled. Wallace's paper set forth, in concise outline, the very theory overwhich Darwin had been laboring for two decades. If evolution was to become science, acausal explanation had to be offered. ReferencesAppel, T. The theory of evolution through natural selection would haveappeared when it did, with or without Darwin, but Darwin's exhaustive andcomprehensive work ensured its swift acceptance, and formed the foundationof modern biology. More than a century after his death, and four generations after thepublication of his chief work, The Origin of Species, Charles Darwinremains possibly the most controversial scientist in the world. All thenaturalists had available, apart from bones, was a "snapshot" of theprocess--the state of life as it is on Earth today. Before offering his insight to the world, Charles Darwin determinedthat he would subject it to close scrutiny. But the Newtonian revolution of the seventeenth century replaced theold static world with a new world view in which everything was naturally inmotion. One could cut off a rat's tail,but its offspring would have normal tails. Yet natural selection comes into its own again in the aftermath, as alargely barren earth is re-colonized by the survivors' descendents. But had the theory of evolution through natural selection appearedonly in outline form, it might have been many more years in winning generalacceptance. His nameis inextricably associated with the debate (now a political and culturalone, not a scientific one) that continues to swirl around the theory ofevolution, a theory that deeply shook the Western view of humanity and itsplace in the world. "On the tendency of species toform varieties; and on the perpetuation of varieties and species bynatural means of selection." In Evolution by Natural Selection (1958).Cambridge: Cambridge University, pp. Luck was probably the largest factor, but not the only one;other things being equal, the strong, the plucky, or the adaptable had asomewhat better chance of surviving than those who lacked thosecharacteristics. For most people (or animalsof any species), times were always hard (Edey and Johnason, 1989, pp. A., and Johnson, D. (198 ). New York: Modern Library. Thenatural implication of a "dynamic" chain of being was a sort of tree oflife, gradually sprouting upward from the primordial ooze, branchingoutward into all the varied species whose relative places in the tree theLinnaean taxonomists had determined, and finally culminating in thathighest and noblest flower: rational, bewigged, eighteenth-century Man. Moreover, in the course of the eighteenth century the notion ofprogress, of gradual but inexorable betterment, began to take hold inWestern thought. 22-26). Two years later, Darwin--having cut short his endlessamassing of evidence--published his full finding in The Origin of Species. The modern, long-necked giraffe thus evolved throughcountless generations of natural selection. 47ff), and spent the next twodecades amassing a great body of evidence, from the distribution of naturalspecies to the experience of pigeon-breeders, to develop and support hisargument. The modern picture of the history of life on earth, then, is of amore dramatic and chaotic history than Darwin envisioned, yet naturalselection continues to play a central role. (1858). Darwin showed that thesame was true of discovery. It was in its traditionalform a static hierarchy, a ranking of entities that extended from the"lowest" forms of life to "higher" living beings (such as the lion, king ofbeasts), through the various gradations of human beings from peasants tonobles to Popes, and thence on upward through the hierarchy of angels toGod. There are other varieties that can interbreed andproduce more or less viable offspring, but do not do so in nature.Finally, there are varieties--in fact, closely related species--whoseoffspring are not viable. The Survival of Charles Darwin. We conventionally speak simply of the theory of evolution, leavingoff the explanatory phrase, "through natural selection." At most, perhaps,the general public has heard of "survival of the fittest"--an unfortunatephrase, since fitness in everyday usage is associated primarily withphysical conditioning and athletic ability. But the introdution ofmutation did not alter the principle of natural selection; a mutated formsurvived and spread only if it was favorable, i.e., offered a selectiveadvantage to the individuals who exhibited it. J. But to the degree that someindividuals inherited these characteristics, they were more likely tosurvive, to hand down these same characteristics to their descendents. New York: RandomHouse.Darwin, C. A Delicate Arrangement: The Strange Case ofCharles Darwin and Alfred Russel Wallace. This concept, in and of itself, has nothing to do with evolution;indeed, it is anti-evolutionary, since every member of the chain is fixedin its own place. 24-25). Becausethe lower branches of the trees they fed off were easily denuded, theseearly giraffes stretched out their necks to reach higher branches. He regarded himself as nowhere near ready to present his theorywhen, in 1858, a young naturalist, Alfred Lord Wallace, sent a paper tohim. Boston: Little, Brown.Gould, S. The development of biology through the century since that time hasnot essentially altered this situation. W. According to Lamarck, the acquiredcharacteristics of parents could be handed down to their offspring (Edeyand Johanson, 1989, pp. Essentially, TheOrigin of Species attacked the problem of evolution through two lines ofargument and analysis, both rooted in the concept of inherited variation(Darwin, n.d.). Thesemust adapt through variation or mutation to fill the ecological niches leftempty by the prior extinctions, and the process of infilling itself opensnew biological niches. A number of notable scientists held out,notably Louis Agassiz, but the younger generation of students coming intothe field seem almost without exception to have adopted the Darwinianmodel. Stated by itself, evolution by natural selection is a strikinginsight, but the fact that it is striking, and seems to explain a greatdeal, does not prove that it is true. Thus speciation in nature did not requiredramatic and implausible jumps, but could emerge out of gradually wideningvariation, itself due to selective adaptation to differing environments. Deliberate selection through breeding wasobviously a much faster and more "efficient" process than natural selectionthrough differential rates of survival in the face of environmentalpressures, but the end result would be essentially the same; the variety ofa given species that was most adapted to a given environment wouldgradually supplant the root stock in that environment. It was only natural that the ideas of change and ofprogress should eventually be applied to the Great Chain of Being. 1859)________, and Wallace, A. Evolution through natural selection was abrilliant idea, and one that might be debated endlessly. But the gaps are filled by evolutionof new forms, not by successive colonizations of existing ones fromunburned areas. 3 -34). Only through proper training, it is true, could one find outif a given hunting dog had favorable characters. The process is roughly analogous, though on avastly longer time-scale, to the sequence by which an area devastated by aforest fire returns to climax state. pub. The Great Chain of Being was developed, indeed, at atime when the world was assumed to be essentially static; in Aristotelianphysics, for example, the only physics known to the earlier Middle Ages,the natural tendence of all objects was to come to rest once they reachedtheir natural place in the universe. Mostrecently, evidence has been found that some of the most dramatic events inthe history of terrestrial life--for example, the extinction of thedinosaurs--may have been very extreme instances of punctuated equilibrium,produced when the Earth's entire environment was drastically altered bycollision with a comet or asteroid (Gould, 1985, pp. A few people may have stumbled upon this idea before Darwin did, butDarwin was the first to develop it. This picture of the history of life could be called evolutionary, andit is a picture so consistant with the world view of the late eighteenthand early nineteenth centuries that we should not be surprised to findvarious evolutionary ideas being offered from the late eighteenth centuryon. The general ideaof natural selection was "in the air" in the mid-nineteenth century, justas the idea of evolution had been "in the air" in the eighteenth. The Cuvier-Geoffroy Debate: French Biology in theDecades Before Darwin. He formulated the outline ofthe theory about 1837 (Clark, 1984, pp. Mediocre blood-stock,exquisitely trained and encouraged, produced mediocre descendents; superiorblood-stock, left entirely untrained, but bred to equally superior stock,produced superior descendents. (1987). Suppose, to take the most familiarexample, that the ancestral giraffe had a neck of ordinary length. But to most of us, "evolution" simply means that human beingsare descended from apes--itself a slight misunderstanding, since bothhumans and modern apes are descendents of a mutual ancestor that is itselfnow extinct. To the degree that strength, drive, or adaptability wereacquired characteristics, they would have no effect on future generations,since Lamarckianism had been proven wrong. Lamarckian evolution had delightful implications that went far beyondthe necks of giraffes. In examining variation in nature, Darwin showed that thedistinction between species was not, in fact, hard and fast. The theory of evolution through natural selection would mostcertainly have appeared, even without Darwin; indeed, it would haveappeared at the same time, since it was Wallace's independent developmentof the theory that prompted his and Darwin's joint paper. (no date). The key wasproduced by the most dismal theorist of the "dismal science" of economics:Thomas Malthus. It stood to reason thatcontemporary Europeans, so endowed, should have more of all these qualitiesthan Red Indians or Hottentots. Such an explanation was proposed by Jean Babtiste Lamarck toward theend of the eighteenth century, and Lamarckianism became the best-known pre-Darwinian theory of evolution. But it is not simply evolution in and of itself, but thetheory of natural selection--and the evidence he amassed to demonstrate it--that were at the heart of Darwin's contribution to biological science. Lamarckianism had also been astriking insight that explained a great deal, but it did not stand up toclose scrutiny. "Survival of the most suitedto its environment" would be a more accurate, if less pithy expression ofthe concept. C. (orig. In sodoing, they caused their offspring to be born with slightly longer necks,until the ultimate result was the giraffe of today. Malthus held that human (and animal) populationspotentially increased at a geometric rate, whereas food supply increasedonly at an arithmetic rate. As wehave seen, the economist Malthus had provided an important conceptualcontribution, and evolution through natural selection was in effect anapplication to the natural world of economic ideas about competition.Indeed, Darwin frequently used the phrase "economy of nature;" the sameconcept is now expressed by the term ecology. Once genetics was more fully understood,it was realized that major steps in speciation might owe more to favorablemutations than to the regular process of variation. 26). New York: Oxford.Brackman, A. But the description above, though evolutionary, does not offer atheory of evolution--a mechanism through which evolution takes place. (1984). Blueprints: Solving the Mysteryof Evolution. Thomas Edison is supposed to have said that invention was one percentinspiration and ninety-nine percent perspiration. (1985). The development was, indeed, morecrucial to the ultimate acceptance of the theory than was the insightalone. Natural selection has alsobeen applied downward, to competition among genes, and upward, tocompetition among entire ecological communities. C. The Flamingo's Smile: Reflections in NaturalHistory. A great many refinements have beenintroduced, or at least debated. 257-79.Edey, M. Butanimal breeders had long since discovered certain principles of breedingfor desired characteristics, and acquired characteristics played no part inthe process. 417-26). The "punctuated equilibrium" school has called into question theDarwinian assumption of steady gradualism in the differentiation ofspecies, by suggesting that most speciation takes place during relativelyshort intervals following some major alteration of the environment. Lamarckianism was thus discredited, and the question of evolutionremained at an impasse. A jointpaper was written and published, and the theory of evolution throughnatural selection was at least presented to the scientific world (Darwinand Wallace, 1858). Malthusianism had an implicit consequence that was not immediatelyrecognized. Which individuals survived in (perpetual) hard times, andwhich died? If this paper is not what you are looking for, you can search again: Search for: or Click here to request an essay written just for you.

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