Charles Darwin's Origins of Species outlined

We found this faithful rendition of Charles Darwin's book. But, Christians must read Darwin's book in whole in order to refute it. Although we have an outline don't let that substitute your studies on Origins of Species.

The Argument of the Origin of Species

The Origin of Species is Darwin's best-known book and is widely available in modern reprints. It should be noted, however, that in response to numerous criticisms Darwin undertook constant revisions between the book's first appearance in 1859 and the sixth edition of 1872. The later editions thus differ considerably from the first, and the last edition contains an additional chapter (chapter 7) dealing with objections to the theory. These changes tend to obscure the original argument and the first edition is thus by far the clearest expression of Darwin's insight. A facsimile of this edition is available and also a concordance, although many modern reprints unfortunately follow the text of the sixth edition. All references below are to the first edition unless otherwise stated.

Introduction: This leads the reader directly to the question of adaptation which Darwin sees as the central problem of evolution. He argues briefly that Lamarckism cannot explain all cases of adaptation and points out that the simple progressionism of the Vestiges does not even address the question of how species become adapted to their environment. From the start Darwin makes it clear that he will be offering a new mechanism to explain the origin of species by adaptation,

The main text of the Origin of Species can be divided into three parts:

Chapters 1-5 outline the theory of natural selection,

Chapters 6-9 (6-10 in the sixth edition) deal with the many objections that Darwin foresees will be raised against his theory, and

the concluding chapters (10-14 in the first edition, 11-15 in the sixth) show how a wide range of otherwise inexplicable phenomena can be illuminated by the theory of common descent by adaptive modification.

I.

Chapters 1-5: outline the theory of natural selection

Chp1: Variation under Domestication: Chapter 1 begins by stressing that animal and plant breeders have been able to produce immense changes within domesticated species. Darwin was convinced that the analogy with artificial selection was the best way of helping his readers to understand how nature might be able to produce similar changes by an equivalent selective process. Almost immediately we encounter Darwin's pre-Mendelian theory of variation and inheritance. Like the notebooks of the 1830s, the Origin of Species is pervaded by a way of thinking about reproduction which is quite alien to modern biology. There is no direct equivalent of the modern belief that the population contains a reservoir of genetic variability, each gene being transmitted as a unit from one generation to the next. Instead, Darwin argues that individual variation is due to the direct effect of changed conditions on the reproductive process. This, he believes, will explain why domesticated species exhibit more variability than wild ones. Further details are given in chapter 5, "Laws of Variation," where he insists that all changes of structure are caused, even though we do not know the cause and speak of them as being due to chance (131-2). In this chapter Darwin admits a minor role for Lamarckism, although he insists that most of the variability is undirected.

In his discussion of variation under domestication, Darwin moves from a general account of the "random" variation in domesticated species to the work of the animal breeders who exploit that variation to produce significant changes. He goes to some length to show that we cannot draw a rigid distinction between the production of new breeds by man and the appearance of new species in nature. Artificial breeds do not invariably tend to revert to some fixed "natural" form for their species. The diversity of pigeon breeds is enormous, and Darwin argues that, if the different breeds were shown to an ornithologist who did not know that they were domesticated, he would classify them as belonging to distinct species, perhaps even distinct genera. What, then, is the explanation of man's ability to produce such enormous changes in a species? "The key is man's power of accumulative selection: nature gives incessant variations; man adds them up in certain directions useful to him" (30).

Chp. 2: Variation under Nature: In chapter 2 Darwin asks whether the variation which serves as the raw material of selection exists in wild populations. He admits that there may be much less variation in the wild because--according to his theory--wild species exist under "natural" conditions which do not disturb the reproductive process. But individual differences do occur and even the most important structures are subject to variation, as evidence of which Darwin cites studies by John Lubbock which had demonstrated major variations in the patterns of the nervous system within a single insect species. "These individual differences are highly important for us, as they afford materials for natural selection to accumulate, in the same manner as man can accumulate in any given direction individual differences in his domesticated productions" (45).

Much of chapter 2 is devoted to a very different method of demonstrating the variability of wild species. Darwin points to the fact that many species are known to form fairly distinct and permanent races or "varieties" adapted to the local conditions in certain parts of their territory. Naturalists had been quite willing to assume that such varieties were formed by common descent from a single ancestral form, yet there was often disagreement as to whether a particular form was a variety or a distinct species. Darwin argues that the confusion arises because varieties are merely an intermediate step in the production of new species: "a well-marked variety may justly be called an incipient species" (52). The term "species" is thus an arbitrary one: a species is just a strongly marked variety that the majority of experienced naturalists agree to call a species. Once this point is accepted the barriers supposedly separating species have been broken down and the way is cleared for transmutation to be used to explain the production of all new forms of life.

Chp. 3: Struggle for Existence: Chapter 3 introduces this concept which arises from the tendency of all species to over-reproduce. If more are born than can possibly survive, there must be competition to see which individuals will get enough of the scarce resources to keep themselves alive. Darwin is quite clear that this idea has its origins in the "principle of population" that Malthus applied to human society: "It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage" (63). The force of this argument is based on numerical calculations designed to show the potential rate of population increase that must be checked by the shortage of resources.

The struggle is most severe between members of the same species, or between closely related varieties, because here the individuals are competing for exactly the same resources. Many different factors determine who shall live and who shall die. Often the elimination takes place among the young; sometimes shortage of food is critical but often it is predators which keep the population down. Darwin emphasizes the complex web of interactions between species, each being held in check by others which prey upon it or upon which it preys. Many readers of the Origin of Species were impressed by his emphasis on the complex network of living relationships even if they did not accept the theory of natural selection. Darwin admits that behind 'the face of nature bright with gladness' there is a scene of constant struggle. Yet he was anxious not to create too harsh an image of nature. He wished to imply that his theory modified, but did not challenge, the prevailing belief that nature had been created by a wise and benevolent God. The last thing he wanted was for people to see his book as the basis for an amoral view of nature. He thus ends his chapter on the struggle for existence with the following words:

When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply. (79)

Chp. 4: Natural Selection: Chapter 4 contains Darwin's main description of his mechanism. After reminding his readers of the power of artificial selection and of the dependence of the wild organism on its environment, he goes on:

Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection. (80-81)

Darwin contrasts nature's powers with those of mankind, stressing how much more effective will be the scrutiny of nature. He points out that natural selection acts only to improve the organisms' ability to cope with their environment and thus tries to persuade his readers that, whatever the apparent harshness of natural selection, we can nevertheless see it as a force promoting the improvement of living things.

Reproduction rather than survival is the crucial factor of course, a point illustrated in the section on 'Sexual selection' in which Darwin argues that any character useful in obtaining a mate will become highly developed. The antlers of deer and the bright colours of many birds are explained by the fact that the mating habits of the various species allow those males with well-developed secondary sexual characters to attract more females.

Darwin explains that the extinction of some forms will be inevitable in a world governed by natural selection. Species will often be exterminated by competitors, thus in effect leaving room for the more successful species to multiply. At the end of chapter 4 he includes a long discussion of the process of divergence by which a single original form can give rise to a family of descendants, each of which will become more specialized for its own way of life and which may itself subdivide. Natural selection will always favour increased specialization even in a stable environment. He gives a diagram to illustrate the process - a classic example of an evolutionary tree. Significantly, Darwin's tree has no central trunk or 'main stem' of evolution. No one branch can be singled out as the main line of development because each is adapting in its own way to the environmental changes it encounters in the course of its migrations. There is no way in which the human race can be seen as the goal towards which the evolution of the whole animal kingdom has been striving.

II.

Chapters 6-9 [6-10 in the sixth edition]: The many objections that Darwin foresees will be raised against his theory

[6]: [Miscellaneous Objections to the Theory of Natural Selection]: The additional chapter [6] added to the last edition includes Darwin's response to critics who had indeed expressed and extended the problems he had anticipated.

Chp. 6: Difficulties on Theory: With chapter 6 [7] we move into the central section of the Origin of Species in which Darwin attempts to defend his idea against the objections he foresees will be raised against it.

1) The first problem in chapter 6 is that of the lack of transitional forms between known species. This is an important point because it is often assumed that a theory of continuous evolution must imply that there are no gaps between species. Darwin argues that this is not the case if evolution is a branching divergent process. Divergence takes place through the continued extermination of the less specialized forms and thus the intermediates do not survive through to the present. In his view, "species come to be tolerably well-defined objects, and do not at any one period present an inextricable chaos of varying and intermediate links" (177).

2) The next problem is the origin of species with peculiar habits or structures. How, for instance, could a non-flying mammal evolve into a bat--surely the intermediate forms would have limbs that were not well adapted either for walking or for flying? Here Darwin appeals to the existence of flying squirrels with varying abilities to glide from tree to tree. These confirm that the intermediate state between legs and wings is viable, thus illustrating the route selection may have taken in the creation of the more perfect wings of bats. Darwin notes that species do indeed change their habits, as witnessed by certain kinds of woodpeckers that do not live in trees and web-footed geese that do not live in water. These examples are inexplicable on the assumption that God creates every species perfectly adapted to its way of life, but are to be expected if species are constantly trying to find new ecological niches to exploit and if evolution takes some time to adjust a species to a new way of life.

3) Darwin also refers to the problem of explaining the evolution of a highly complex structure such as the human eye. He notes that in the invertebrates there are creatures with eyes of varying degrees of complexity, showing that intermediate stages in the development of vision can be of benefit to the species. He admits that, if one could find a complex organ for which no intermediate states were conceivable, his theory would have to be rejected, but insists that no such organs are known. Another problem is the existence of organs of little apparent importance. If natural selection works only by seizing upon advantageous variations, then surely all characters must be adaptive. Yet many naturalists were convinced that species possess useless characters. Darwin responds to this problem by suggesting that we may often underestimate a structure's usefulness. The giraffe's tail seems to be used as a fly-flapper, which appears rather trivial until one recollects that in some parts of the tropics the distribution of large mammals is critically determined by their vulnerability to insect pests.

Chp. 7: Instinct: Chapter 7 [8] deals with, a topic of particular interest to Darwin because he was convinced that evolution must be able to explain animal behaviour. The Lamarckians had an obvious explanation of instinct as a learned habit that had gradually been built into the species' hereditary constitution. But Darwin notes that this will not explain the instincts of neuter insects. He was convinced that natural selection can act on instincts just as it can act on physical characters. There is variation within the instinctive behaviour of any particular species, as shown by the fact that man has been able to eradicate the dog's instinctive tendency to attack sheep. Thus selection will be able to enhance a useful instinct by seizing upon useful variations. The case of neuter insects is explained by the fact that selection can act on families as well as individuals: insects with a tendency to produce some useful but neuter types among their offspring would survive better as the founders of colonies.

Chp. 8: Hybridism: In chapter 8 [9], Darwin deals with what many critics saw as a fatal objection to his theory. Varieties formed within the same species can be cross-bred with one another, but on the traditional view any attempt to hybridize distinct species will always fail. Darwin counters this argument by showing that the supposed absolute distinction between varieties and species is not as clear-cut as was popularly supposed. He cites extensive evidence to show that varying degrees of sterility are encountered in efforts to cross-breed different species of plants. If the species are closely related, there will often be a small degree of fertility in the hybrid offspring. His conclusion is that, far from being a fatal objection to his theory, a close study of hybridization confirms that there is no sharp distinction between varieties and species. As two related forms diverge further from one another in the course of evolution, their ability to interbreed gradually diminishes and eventually falls to zero, that is, absolute sterility.

Chp. 9: On the Imperfection of the Geological Record: In Chapter 9 Darwin anticipates objections to his commitment to the belief that evolution always takes place slowly and gradually. He was aware that this did not seem to be supported by the fossil record which generally shows new species appearing abruptly with no sign of an evolutionary ancestry. He argues that the discontinuity is a result of the record's imperfection and not an indication that species really are introduced suddenly. He points out (280) that it would be a mistake to look for simple intermediates between two related forms; they will have diverged from a common ancestor that would not have been an exact intermediate between its later descendants. But even this more complex kind of relationship is seldom found in the record, and Darwin insists that we should not expect to find all the steps in evolution preserved in the rocks. Fossilbearing rocks are only laid down in certain circumstances, and thus long periods of time will have passed between the deposition of strata that now seem consecutive. Even when we have a continuous sequence of depositions, evolutionary changes may often have taken place in isolated parts of a species' range where fossils are not being laid down (a point amplified in the modern theory of punctuated equilibrium).

A related problem concerns the abrupt appearance of whole groups of living things at certain points in the record. The most obvious example of this is what we now know as the "Cambrian explosion" the sudden appearance of all the basic modern types at the beginning of the Cambrian era. (Note that in the first edition Darwin places this in the Silurian--the geological nomenclature was disputed at the time.) Darwin argues that the imperfection of the record also accounts for these episodes. There must have been vast periods of time before the Cambrian when life was evolving but from which so far no fossils had been found. Perhaps the continents were positioned differently so long ago, and most of the fossil-bearing rocks from that age are sunk beneath the modern oceans. All that Darwin could do was to express the hope that some fossils from the pre-Cambrian rocks would eventuall~, be found to fill in the gap.

III.

Chapters 10-14 [11-15]: a wide range of otherwise inexplicable phenomena can be illuminated by the theory of common descent by adaptive modification.

Chp. 10: On the Geological Succession of Organic Beings: Chapter 10 [11] continues the discussion of the fossil record but Darwin now moves onto the offensive so that his concluding chapters can present the positive case for evolution. Here he argues that, if we make allowances for the imperfection of the record, the known fossils are distributed just as one would expect on the basis of a theory of common descent. Palaeontologists were generally agreed that in any sequence of fossil formations the intermediate forms in time were intermediate in character. Owen and others had also shown that ancient types often seemed to 'fall between' the more distinct modern forms. Thus the pigs and camels could now be united into a single group by including fossils which were intermediate in character. To Darwin it was obvious that these ancient types were the generalized ancestors from which the more specialized modern forms had evolved.

Chp. 11: Geographic Distribution: This and the next chapter deal some of the evidence that converted Darwin himself to a belief in evolution. In Chapter 11 Darwin insists that the differences between the Old and New World faunas cannot be explained in terms of climate since both areas share the same range of physical conditions. The ostrich of Africa and the rhea of South America are superficially similar, but when examined carefully each is seen to be characteristic of its own continent. The chief determinant of geographical distribution is the barriers which exist to free migration, of which the oceans are the most important in the case of land animals. Conversely, dry land creates an obvious barrier to the migration of marine forms. Darwin argues that a successful species will spread out as far as it can, adapting to the local conditions it encounters, until it meets an impassable barrier. Thus on his theory it is to be expected that major barriers to migration will define unique groups of species.

Chp. 12: Geographic Distribution (Continued): In Chapter 12 Darwin also discusses the process by which oceanic islands such as the Galapagos are populated, bringing in his own studies of how seeds and eggs can occasionally be transported across wide stretches of ocean.

Chp. 13: Mutual Affinities of Organic Beings: Chapter 13 allows Darwin to develop the explanatory power of his theory to the full. He picks out a number of phenomena encountered by naturalists in their efforts to classify species and demonstrates that they are explicable only in terms of a theory of common descent. The basic system of classification entails the grouping of similar species into genera, the genera themselves into families and so on. By uncovering these relationships naturalists were seeking what was called a 'Natural System' of classification - but Darwin now asks what this system is supposed to be. Is it the plan of the Creator, as many exponents of natural theology liked to claim? Darwin insists that to assume the existence of an underlying divine plan adds nothing to our knowledge of natural relationships. His theory alone can explain why species are grouped together: the natural system is an expression of evolutionary relationships, in effect a cross-section of the evolutionary tree.

Darwin next turns to embryology, noting that the embryos of different animals often show a much greater degree of resemblance than the adults. This, he believes, can be explained on the assumption that adaptive modifications are produced mostly by changes in the later stages of growth, leaving the early pattern of development unchanged. For Darwin, the embryo represents the species in a less modified state and thus helps to reveal its natural relationships. In some cases the embryo may actually resemble ancestral forms that can be discovered in the fossil record (449-50). But this is a far cry from the so-called, 'recapitulation theory' in which the development of the human embryo is supposed to repeat the whole pattern of evolution revealed by the fossil record. Darwin had no interest in the idea of a linear pattern of development leading up to mankind as the goal of creation, and hence no interest in using the growth of the human embryo as a model for the "main line" of evolution.

Finally, Darwin turns to the topic of rudimentary or atrophied organs. Many species have such organs, which are of no apparent use and which often never develop beyond a vestigial stage. Creationists must explain such structures as necessary "for the sake of symmetry' or ,to complete the scheme of nature," but Darwin once again insists that to invoke a divine plan of nature is no explanation at all. The evolutionist has an obvious explanation since he can show that the rudimentary organs are relics of once useful structures, now declining because the changing habits of the species have rendered them superfluous. Heredity preserves the structure to some extent but it gradually decays because natural selection will favor those individuals who do not waste their energy growing useless structures.

Chp. 14: Recapitulation and Conclusions: In chapter 14 Darwin sums up the general implications of his new approach. He looks to the younger generation of naturalists in the hope that they will be able to throw off the prejudices that commit many experienced workers to creationism. He now reveals how far he is prepared to extend his theory. The basic similarities between all living things lead him to infer that "all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed" (484). The latter phrase seems to imply that the original creation of life was by divine miracle. It is not at all clear that Darwin really believed this, but he knew that biologists such as Pasteur had demolished the claim that life was now being produced by spontaneous generation. Perhaps conditions were different in the early periods of the earth's history, but Darwin had no interest in trying to explore the ultimate origins of life. Spontaneous generation was seen as an inherently materialistic hypothesis and he thus felt it safer to leave open the possibility of a supernatural origin.

Darwin expresses the hope that evolutionism will bring about a revolution in natural history as scientists begin to explore the theory's applications. In particular he notes that "Light will be thrown on the origin of man and his history" (488). This is not the only reference to changes within the human race in the Origin of Species, but it is the only absolutely unequivocal statement of Darwin's belief that his theory will account for the origins of mankind from a lower form. He was well aware that the extension of the theory to mankind would provoke controversy because it would threaten the traditional view that our mental powers lift us onto a higher plane than the animals. He hoped to minimize the resulting outcry by refusing to discuss human origins in detail but felt that he had to include at least this brief indication of his beliefs.

To offset this dangerous implication, Darwin concludes with an effort to convince his readers that the theory can be reconciled with traditional beliefs about the relationship between God and nature. He argues that it is better to think of the Creator governing the world by law rather than by arbitrary miracles and suggests that 'as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection' (488-9)

There can be no direct trend leading towards mankind, but we can be sure that the overall effect of natural selection is progressive and hence that the human race is the outcome of a process established by its Creator. Natural selection follows inevitably from the laws of reproduction and is thus the best way for God to ensure progress in so complex a world.

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; 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. (490)

 

 

-------------------------------------------------------------------------------------

Home

 

 

Hosted by www.Geocities.ws

1