Friday, May 10, 2013

Chapter XI deals with evidence from biogeography

Chapter XI deals with evidence from biogeography, starting with the observation that differences in flora and fauna from separate regions cannot be explained by environmental differences alone; South America, Africa, and Australia all have regions with similar climates at similar latitudes, but those regions have very different plants and animals. Sony VPCEH28FH/B battery The species found in one area of a continent are more closely allied with species found in other regions of that same continent than to species found on other continents. Darwin noted that barriers to migration played an important role in the differences between the species of different regions. Sony VPCEH28FJ/B battery The coastal sea life of the Atlantic and Pacific sides of Central America had almost no species in common even though the Isthmus of Panama was only a few miles wide. His explanation was a combination of migration and descent with modification. He went on to say: "On this principle of inheritance with modification, we can understand how it is that sections of genera, Sony VPCEH28FJ/P battery whole genera, and even families are confined to the same areas, as is so commonly and notoriously the case."[122] Darwin explained how a volcanic island formed a few hundred miles from a continent might be colonised by a few species from that continent. These species would become modified over time, but would still be related to species found on the continent, Sony VPCEH28FJ/W battery and Darwin observed that this was a common pattern. Darwin discussed ways that species could be dispersed across oceans to colonise islands, many of which he had investigated experimentally.[123] Chapter XII continues the discussion of biogeography. After a brief discussion of freshwater species, it returns to oceanic islands and their peculiarities; Sony VPCEH28FN/L battery for example on some islands roles played by mammals on continents were played by other animals such as flightless birds or reptiles. The summary of both chapters says: I think all the grand leading facts of geographical distribution are explicable on the theory of migration (generally of the more dominant forms of life), together with subsequent modification and the multiplication of new forms. Sony VPCEH29FJ/B battery We can thus understand the high importance of barriers, whether of land or water, which separate our several zoological and botanical provinces. We can thus understand the localisation of sub-genera, genera, and families; and how it is that under different latitudes, for instance in South America, the inhabitants of the plains and mountains, Sony VPCEH29FJ/P battery of the forests, marshes, and deserts, are in so mysterious a manner linked together by affinity, and are likewise linked to the extinct beings which formerly inhabited the same continent ... On these same principles, we can understand, as I have endeavoured to show, why oceanic islands should have few inhabitants, but of these a great number should be endemic or peculiar; Sony VPCEH29FJ/W battery Chapter XIII starts by observing that classification depends on species being grouped together in a multilevel system of groups and sub groups based on varying degrees of resemblance. After discussing classification issues, Darwin concludes: All the foregoing rules and aids and difficulties in classification are explained, Sony VPCEH2C0E battery if I do not greatly deceive myself, on the view that the natural system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and, in so far, all true classification is genealogical; Sony VPCEH2D0E battery that community of descent is the hidden bond which naturalists have been unconsciously seeking, Darwin discusses morphology, including the importance of homologous structures. He says, "What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, Sony VPCEH2E0E battery and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?"[126] He notes that animals of the same class often have extremely similar embryos. Darwin discusses rudimentary organs, such as the wings of flightless birds and the rudiments of pelvis and leg bones found in some snakes. Sony VPCEH2F1E battery He remarks that some rudimentary organs, such as teeth in baleen whales, are found only in embryonic stages. The final chapter reviews points from earlier chapters, and Darwin concludes by hoping that his theory might produce revolutionary changes in many fields of natural history. Sony VPCEH2H1E battery Although he avoids the controversial topic of human origins in the rest of the book so as not to prejudice readers against his theory, here he ventures a cautious hint that psychology would be put on a new foundation and that "Light will be thrown on the origin of man".[127] Darwin ends with a passage that became well known and much quoted: Sony VPCEH2J1E battery It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, Sony VPCEH2L9E battery have all been produced by laws acting around us ... Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; Sony VPCEH2M1E battery and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. Darwin's aims were twofold: to show that species had not been separately created, and to show that natural selection had been the chief agent of change. Sony VPCEH2M9E battery He knew that his readers were already familiar with the concept of transmutation of species from Vestiges, and his introduction ridicules that work as failing to provide a viable mechanism.Therefore the first four chapters lay out his case that selection in nature, caused by the struggle for existence, is analogous to the selection of variations under domestication, Sony VPCEH2N1E battery and that the accumulation of adaptive variations provides a scientifically testable mechanism for evolutionary speciation. Later chapters provide evidence that evolution has occurred, supporting the idea of branching, adaptive evolution without directly proving that selection is the mechanism. Sony VPCEH2P0E battery Darwin presents supporting facts drawn from many disciplines, showing that his theory could explain a myriad of observations from many fields of natural history that were inexplicable under the alternate concept that species had been individually created. Sony VPCEH2Q1E battery The structure of Darwin's argument showed the influence of John Herschel, whose philosophy of science maintained that a mechanism could be called a vera causa (true cause) if three things could be demonstrated: its existence in nature, its ability to produce the effects of interest, and its ability to explain a wide range of observations. Sony VPCEH2S9E battery The Examiner review of 3 December 1859 commented, "Much of Mr. Darwin's volume is what ordinary readers would call 'tough reading;' that is, writing which to comprehend requires concentrated attention and some preparation for the task. All, however, is by no means of this description, and many parts of the book abound in information, easy to comprehend and both instructive and entertaining." Sony VPCEH2Z1E battery While the book was readable enough to sell, its dryness ensured that it was seen as aimed at specialist scientists and could not be dismissed as mere journalism or imaginative fiction. Unlike the still-popular Vestiges, it avoided the narrative style of the historical novel and cosmological speculation, though the closing sentence clearly hinted at cosmic progression. Sony VPCEH3B1E battery Darwin had long been immersed in the literary forms and practices of specialist science, and made effective use of his skills in structuring arguments.[130] David Quammen has described the book as written in everyday language for a wide audience, but noted that Darwin's literary style was uneven: in some places he used convoluted sentences that are difficult to read; Sony VPCEH3D0E battery in other places his writing was beautiful. Quammen advised that later editions were weakened by Darwin making concessions and adding details to address his critics, and recommended the first edition.[137]James T. Costa said that because the book was an abstract produced in haste in response to Wallace's essay, Sony VPCEH3N1E battery it was more approachable than the big book on natural selection Darwin had been working on, which would have been encumbered by scholarly footnotes and much more technical detail. He added that some parts of Origin are dense, but other parts are almost lyrical, and the case studies and observations are presented in a narrative style unusual in serious scientific books, which broadened its audience. Sony VPCEH3N6E battery The book aroused international interest[140] and a widespread debate, with no sharp line between scientific issues and ideological, social and religious implications.[141] Much of the initial reaction was hostile, but Darwin had to be taken seriously as a prominent and respected name in science. There was much less controversy than had greeted the 1844 publicationVestiges of Creation, Sony VPCEH3T9E battery which had been rejected by scientists,[140] but had influenced a wide public readership into believing that nature and human society were governed by natural laws.[25] The Origin of Species as a book of wide general interest became associated with ideas of social reform. Its proponents made full use of a surge in the publication of review journals, Sony VPCZ21V9E battery and it was given more popular attention than almost any other scientific work, though it failed to match the continuing sales of Vestiges.[142] Darwin's book legitimised scientific discussion of evolutionary mechanisms, and the newly coined termDarwinism was used to cover the whole range of evolutionism, not just his own ideas. By the mid-1870s, evolutionism was triumphant.[141] Sony VPCZ21Q9E battery With the exception of a brief hint in the final chapter, Darwin had avoided the subject of human evolution. Despite this, the first review claimed it made a creed of the "men from monkeys" idea from Vestiges.[143] Human evolution became central to the debate and was strongly argued by Huxley who featured it in his popular "working-men's lectures". Sony VPCZ21M9E battery Darwin did not publish his own views on this until 1871.[144] The naturalism of natural selection conflicted with presumptions of purpose in nature and while this could be reconciled bytheistic evolution, other mechanisms implying more progress or purpose were more acceptable. Sony VPCZ13Z9E/X battery Herbert Spencer had already incorporated Lamarckism into his popular philosophy of progressive free market human society. He popularised the termsevolution and survival of the fittest, and many thought Spencer was central to evolutionary thinking. Scientific readers were already aware of arguments that species changed through processes that were subject to laws of nature, Sony VPCZ13V9E/X battery but the transmutational ideas of Lamarck and the vague "law of development" of Vestiges had not found scientific favour. Darwin presented natural selection as a scientifically testable mechanism while accepting that other mechanisms such as inheritance of acquired characters were possible. Sony VPCZ13X5003B battery His strategy established that evolution through natural laws was worthy of scientific study, and by 1875, most scientists accepted that evolution occurred but few thought natural selection was significant. Darwin's scientific method was also disputed, with his proponents favouring theempiricism of John Stuart Mill's A System of Logic, Sony VPCZ13V9E battery while opponents held to the idealist school of William Whewell's Philosophy of the Inductive Sciences, in which investigation could begin with the intuitive truth that species were fixed objects created by design.[146] Early support for Darwin's ideas came from the findings of field naturalists studying biogeography and ecology, including Joseph Dalton Hooker in 1860, Sony VPCZ13M9E/X battery and Asa Gray in 1862. Henry Walter Bates presented research in 1861 that explained insect mimicry using natural selection. Alfred Russel Wallace discussed evidence from his Malay archipelago research, including an 1864 paper with an evolutionary explanation for the Wallace line. Sony VPCZ13M9E/B battery Evolution had less obvious applications to anatomy and morphology, and at first had little impact on the research of the anatomist Thomas Henry Huxley.[149] Despite this, Huxley strongly supported Darwin on evolution; though he called for experiments to show whether natural selection could form new species, and questioned if Darwin'sgradualism was sufficient without sudden leaps to cause speciation. Sony VPCZ138GA battery Huxley wanted science to be secular, without religious interference, and his article in the April 1860 Westminster Review promoted scientific naturalism over natural theology,[150][151] praising Darwin for "extending the domination of Science over regions of thought into which she has, as yet, hardly penetrated" and coining the term "Darwinism" as part of his efforts to secularise and professionalise science.[152] Sony VPCZ12Z9E/X battery Huxley gained influence, and initiated the X Club, which used the journal Natureto promote evolution and naturalism, shaping much of late Victorian science. Later, the German morphologist Ernst Haeckel would convince Huxley that comparative anatomy and palaeontology could be used to reconstructevolutionary genealogies. Sony VPCEH16EF/B battery The leading naturalist in Britain was the anatomist Richard Owen, an idealist who had shifted to the view in the 1850s that the history of life was the gradual unfolding of a divine plan.[154] Owen's review of the Origin in the April 1860 Edinburgh Review bitterly attacked Huxley, Hooker and Darwin, but also signalled acceptance of a kind of evolution as a teleological plan in a continuous "ordained becoming",Sony VPCEH16EG/W battery with new species appearing by natural birth. Others that rejected natural selection, but supported "creation by birth", included the Duke of Argyll who explained beauty in plumage by design.[155] Since 1858, Huxley had emphasised anatomical similarities between apes and humans, contesting Owen's view that humans were a separate sub-class. Sony VPCEH16EH/W battery Their disagreement over human origins came to the fore at the British Association for the Advancement of Science meeting featuring the legendary 1860 Oxford evolution debate.[156] In two years of acrimonious public dispute that Charles Kingsley satirised as the "Great Hippocampus Question" and parodied in The Water-Babies as the "great hippopotamus test", Sony VPCEH16EN/B battery Huxley showed that Owen was incorrect in asserting that ape brains lacked a structure present in human brains.[157] Others, including Charles Lyell and Alfred Russel Wallace, thought that humans shared a common ancestor with apes, but higher mental faculties could not have evolved through a purely material process. Darwin published his own explanation in the Descent of Man (1871). Sony VPCEH17FG/B battery Evolutionary ideas, although not natural selection, were accepted by German biologists accustomed to ideas of homology inmorphology from Goethe's Metamorphosis of Plants and from their long tradition of comparative anatomy. Bronn's alterations in his German translation added to the misgivings of conservatives, but enthused political radicals. Sony VPCEH17FG/L battery Ernst Haeckel was particularly ardent, aiming to synthesise Darwin's ideas with those of Lamarck and Goethe while still reflecting the spirit of Naturphilosophie.[68][160] Their ambitious programme to reconstruct the evolutionary history of life was joined by Huxley and supported by discoveries in palaeontology. Sony VPCEH17FG/P battery Haeckel used embryology extensively in his recapitulation theory, which embodied a progressive, almost linear model of evolution. Darwin was cautious about such histories, and had already noted that von Baer's laws of embryology supported his idea of complex branching.[159] Asa Gray promoted and defended Origin against those American naturalists with an idealist approach, Sony VPCEH17FG/W battery notably Louis Agassiz who viewed every species as a distinct fixed unit in the mind of the Creator, classifying as species what others considered merely varieties. Edward Drinker Cope and Alpheus Hyatt reconciled this view with evolutionism in a form of neo-Lamarckisminvolving recapitulation theory.[160] Sony VPCEH17FJ/W battery French speaking naturalists in several countries showed appreciation of the much modified French translation by Clémence Royer, but Darwin's ideas had little impact in France, where any scientists supporting evolutionary ideas opted for a form of Lamarckism.[71] The intelligentsia in Russia had accepted the general phenomenon of evolution for several years before Darwin had published his theory, Sony VPCEH18FA/B battery and scientists were quick to take it into account, although the Malthusian aspects were felt to be relatively unimportant. The political economy of struggle was criticised as a British stereotype by Karl Marx and by Leo Tolstoy, who had the character Levin in his novel Anna Karenina voice sharp criticism of the morality of Darwin's views. Sony VPCEH18FF/B battery There were serious scientific objections to the process of natural selection as the key mechanism of evolution, includingKarl von Nägeli's insistence that a trivial characteristic with no adaptive advantage could not be developed by selection. Darwin conceded that these could be linked to adaptive characteristics. Sony VPCEH18FG/L battery His estimate that the age of the Earth allowed gradual evolution was disputed by William Thomson (later awarded the title Lord Kelvin), who calculated that it had cooled in less than 100 million years. Darwin accepted blending inheritance, but Fleeming Jenkin calculated that as it mixed traits, natural selection could not accumulate useful traits. Sony VPCEH18FH/P battery Darwin tried to meet these objections in the 5th edition. Mivartsupported directed evolution, and compiled scientific and religious objections to natural selection. In response, Darwin made considerable changes to the sixth edition. The problems of the age of the Earth and heredity were only resolved in the 20th century.[60][161] Sony VPCEH18FJ/B battery By the mid-1870s, most scientists accepted evolution, but relegated natural selection to a minor role as they believed evolution was purposeful and progressive. The range of evolutionary theories during "the eclipse of Darwinism" included forms of "saltationism" in which new species were thought to arise through "jumps" rather than gradual adaptation, Sony VPCEH18FJ/P battery forms of orthogenesis claiming that species had an inherent tendency to change in a particular direction, and forms of neo-Lamarckism in which inheritance of acquired characteristics led to progress. The minority view of August Weismann, that natural selection was the only mechanism, was called neo-Darwinism. Sony VPCEH18FJ/W battery It was thought that the rediscovery of Mendelian inheritance invalidated Darwin's views. While some, like Spencer, used analogy from natural selection as an argument against government intervention in the economy to benefit the poor, others, including Alfred Russel Wallace, Sony VPCEH19FJ/B battery argued that action was needed to correct social and economic inequities to level the playing field before natural selection could improve humanity further. Some political commentaries, including Walter Bagehot's Physics and Politics (1872), attempted to extend the idea of natural selection to competition between nations and between human races. Sony VPCEH19FJ/P battery Such ideas were incorporated into what was already an ongoing effort by some working inanthropology to provide scientific evidence for the superiority of Caucasians over non white races and justify European imperialism. Historians write that most such political and economic commentators had only a superficial understanding of Darwin's scientific theory, Sony VPCEH19FJ/W battery and were as strongly influenced by other concepts about social progress and evolution, such as the Lamarckian ideas of Spencer and Haeckel, as they were by Darwin's work. Darwin objected to his ideas being used to justify military aggression and unethical business practices as he believed morality was part of fitness in humans, and he opposed polygenism, Sony VPCEH1AJ battery the idea that human races were fundamentally distinct and did not share a recent common ancestry. The book produced a wide range of religious responses at a time of changing ideas and increasing secularisation. The issues raised were complex and there was a large middle ground. Developments in geology meant that there was little opposition based on a literal reading of Genesis, Sony VPCEH1E1E battery but defence of the argument from design and natural theology was central to debates over the book in the English speaking world. Natural theology was not a unified doctrine, and while some such as Louis Agassiz were strongly opposed to the ideas in the book, others sought a reconciliation in which evolution was seen as purposeful. Sony VPCEH1J1E battery In the Church of England, some liberal clergymen interpreted natural selection as an instrument of God's design, with the cleric Charles Kingsley seeing it as "just as noble a conception of Deity".[169][170] In the second edition of January 1860, Darwin quoted Kingsley as "a celebrated cleric", and added the phrase "by the Creator" to the closing sentence, which from then on read "life, Sony VPCEH1J8E battery with its several powers, having been originally breathed by the Creator into a few forms or into one".[171] While some commentators have taken this as a concession to religion that Darwin later regretted,[57] Darwin's view at the time was of God creating life through the laws of nature,[172][173] and even in the first edition there are several references to "creation".Sony VPCEH1L0E battery Baden Powell praised "Mr Darwin's masterly volume [supporting] the grand principle of the self-evolving powers of nature".[175] In America, Asa Gray argued that evolution is the secondary effect, or modus operandi, of the first cause, design,[176] and published a pamphlet defending the book in terms of theistic evolution, Natural Selection is not inconsistent with Natural Theology. Sony VPCEH1L8E battery Theistic evolution became a popular compromise, and St. George Jackson Mivart was among those accepting evolution but attacking Darwin's naturalistic mechanism. Eventually it was realised that supernatural intervention could not be a scientific explanation, and naturalistic mechanisms such as neo-Lamarckism were favoured over natural selection as being more compatible with purpose.[165] Sony VPCEH1L9E battery Even though the book had barely hinted at human evolution, it quickly became central to the debate as mental and moral qualities were seen as spiritual aspects of the immaterial soul, and it was believed that animals did not have spiritual qualities. This conflict could be reconciled by supposing there was some supernatural intervention on the path leading to humans, Sony VPCEH1M1E battery or viewing evolution as a purposeful and progressive ascent to mankind's position at the head of nature.[165] While many conservative theologians accepted evolution, Charles Hodge argued in his 1874 critique "What is Darwinism?" that "Darwinism", defined narrowly as including rejection of design, was atheism though he accepted that Asa Gray did not reject design. Sony VPCEH1M9E battery Asa Gray responded that this charge misrepresented Darwin's text.[181] By the early 20th century, four noted authors of The Fundamentals were explicitly open to the possibility that God created through evolution,[182] but fundamentalism inspired the American creation–evolution controversy that began in the 1920s. Sony VPCEH1S0E battery Some conservative Roman Catholic writers and influential Jesuits opposed evolution in the late 19th and early 20th century, but other Catholic writers, starting with Mivart, pointed out that early Church Fathers had not interpreted Genesis literally in this area.[183] The Vatican stated its official position in a 1950 papal encyclical, which held that evolution was not inconsistent with Catholic teaching. Sony VPCEH1S1E battery Various alternative evolutionary mechanisms favoured during "the eclipse of Darwinism" became untenable as more was learned about inheritance and mutation. The full significance of natural selection was at last accepted in the 1930s and 1940s as part of the modern evolutionary synthesis. During that synthesis biologists and statisticians, including R. A. Fisher, Sony VPCEH1S8E battery Sewall Wright and J.B.S. Haldane, merged Darwinian selection with a statistical understanding of Mendelian genetics.[163] Modern evolutionary theory continues to develop. Darwin's theory of evolution by natural selection, with its tree-like model of branching common descent, has become the unifying theory of the life sciences. Sony VPCEH1S9E battery The theory explains the diversity of living organisms and their adaptation to the environment. It makes sense of thegeologic record, biogeography, parallels in embryonic development, biological homologies, vestigiality,cladistics, phylogenetics and other fields, with unrivalled explanatory power; it has also become essential to applied sciences such as medicine and agriculture. Sony VPCEH1Z1E battery Despite the scientific consensus, a religion-based political controversy has developed over how evolution is taught in schools, especially in the United States.[188] Interest in Darwin's writings continues, and scholars have generated an extensive literature, the Darwin Industry, about his life and work. Sony VPCEH24FX/B battery The text of Origin itself has been subject to much analysis including avariorum, detailing the changes made in every edition, first published in 1959,[189] and a concordance, an exhaustive external index published in 1981.[190]Worldwide commemorations of the 150th anniversary of the publication of On the Origin of Species and the bicentenary of Darwin's birth were scheduled for 2009.[191] Sony VPCEH24FX/L battery They celebrated the ideas which "over the last 150 years have revolutionised our understanding of nature and our place within it".Sony VPCEH24FX/P battery,Sony VPCEH24FX/W battery,Sony VPCEH25EG/B battery

No comments:

Post a Comment