| Recent Review: |  | When on board H.M.S. 'Beagle,' as naturalist, I was much struck withcertain facts in the distribution of the inhabitants of South America,and in the geological relations of the present to the past inhabitantsof that continent. These facts seemed to me to throw some light on theorigin of species--that mystery of mysteries, as it has been called byone of our greatest philosophers. On my return home, it occurred tome, in 1837, that something might perhaps be made out on this questionby patiently accumulating and reflecting on all sorts of facts whichcould possibly have any bearing on it. After five years' work Iallowed myself to speculate on the subject, and drew up some shortnotes; these I enlarged in 1844 into a sketch of the conclusions,which then seemed to me probable: from that period to the present dayI have steadily pursued the same object. I hope that I may be excusedfor entering on these personal details, as I give them to show that Ihave not been hasty in coming to a decision.My work is now nearly finished; but as it will take me two or threemore years to complete it, and as my health is far from strong, I havebeen urged to publish this Abstract. I have more especially beeninduced to do this, as Mr. Wallace, who is now studying the naturalhistory of the Malay archipelago, has arrived at almost exactly thesame general conclusions that I have on the origin of species. Lastyear he sent to me a memoir on this subject, with a request that Iwould forward it to Sir Charles Lyell, who sent it to the LinneanSociety, and it is published in the third volume of the Journal ofthat Society. Sir C. Lyell and Dr. Hooker, who both knew of mywork--the latter having read my sketch of 1844--honoured me bythinking it advisable to publish, with Mr. Wallace's excellent memoir,some brief extracts from my manuscripts.This Abstract, which I now publish, must necessarily be imperfect. Icannot here give references and authorities for my several statements;and I must trust to the reader reposing some confidence in myaccuracy. No doubt errors will have crept in, though I hope I havealways been cautious in trusting to good authorities alone. I can heregive only the general conclusions at which I have arrived, with a fewfacts in illustration, but which, I hope, in most cases will suffice.No one can feel more sensible than I do of the necessity of hereafterpublishing in detail all the facts, with references, on which myconclusions have been grounded; and I hope in a future work to dothis. For I am well aware that scarcely a single point is discussed inthis volume on which facts cannot be adduced, often apparently leadingto conclusions directly opposite to those at which I have arrived. Afair result can be obtained only by fully stating and balancing thefacts and arguments on both sides of each question; and this cannotpossibly be here done.I much regret that want of space prevents my having the satisfactionof acknowledging the generous assistance which I have received fromvery many naturalists, some of them personally unknown to me. Icannot, however, let this opportunity pass without expressing my deepobligations to Dr. Hooker, who for the last fifteen years has aided mein every possible way by his large stores of knowledge and hisexcellent judgment.In considering the Origin of Species, it is quite conceivable that anaturalist, reflecting on the mutual affinities of organic beings, ontheir embryological relations, their geographical distribution,geological succession, and other such facts, might come to theconclusion that each species had not been independently created, buthad descended, like varieties, from other species. Nevertheless, sucha conclusion, even if well founded, would be unsatisfactory, until itcould be shown how the innumerable species inhabiting this world havebeen modified, so as to acquire that perfection of structure andcoadaptation which most justly excites our admiration. Naturalistscontinually refer to external conditions, such as climate, food, etc.,as the only possible cause of variation. In one very limited sense, aswe shall hereafter see, this may be true; but it is preposterous toattribute to mere external conditions, the structure, for instance, ofthe woodpecker, with its feet, tail, beak, and tongue, so admirablyadapted to catch insects under the bark of trees. In the case of themisseltoe, which draws its nourishment from certain trees, which hasseeds that must be transported by certain birds, and which has flowerswith separate sexes absolutely requiring the agency of certain insectsto bring pollen from one flower to the other, it is equallypreposterous to account for the structure of this parasite, with itsrelations to several distinct organic beings, by the effects ofexternal conditions, or of habit, or of the volition of the plantitself.The author of the 'Vestiges of Creation' would, I presume, say that,after a certain unknown number of generations, some bird had givenbirth to a woodpecker, and some plant to the misseltoe, and that thesehad been produced perfect as we now see them; but this assumptionseems to me to be no explanation, for it leaves the case of thecoadaptations of organic beings to each other and to their physicalconditions of life, untouched and unexplained.It is, therefore, of the highest importance to gain a clear insightinto the means of modification and coadaptation. At the commencementof my observations it seemed to me probable that a careful study ofdomesticated animals and of cultivated plants would offer the bestchance of making out this obscure problem. Nor have I beendisappointed; in this and in all other perplexing cases I haveinvariably found that our knowledge, imperfect though it be, ofvariation under domestication, afforded the best and safest clue. Imay venture to express my conviction of the high value of suchstudies, although they have been very commonly neglected bynaturalists.From these considerations, I shall devote the first chapter of thisAbstract to Variation under Domestication. We shall thus see that alarge amount of hereditary modification is at least possible, and,what is equally or more important, we shall see how great is the powerof man in accumulating by his Selection successive slight variations.I will then pass on to the variability of species in a state ofnature; but I shall, unfortunately, be compelled to treat this subjectfar too briefly, as it can be treated properly only by giving longcatalogues of facts. We shall, however, be enabled to discuss whatcircumstances are most favourable to variation. In the next chapterthe Struggle for Existence amongst all organic beings throughout theworld, which inevitably follows from their high geometrical powers ofincrease, will be treated of. This is the doctrine of Malthus, appliedto the whole animal and vegetable kingdoms. As many more individualsof each species are born than can possibly survive; and as,consequently, there is a frequently recurring struggle for existence,it follows that any being, if it vary however slightly in any mannerprofitable to itself, under the complex and sometimes varyingconditions of life, will have a better chance of surviving, and thusbe NATURALLY SELECTED. From the strong principle of inheritance, anyselected variety will tend to propagate its new and modified form.This fundamental subject of Natural Selection will be treated at somelength in the fourth chapter; and we shall then see how NaturalSelection almost inevitably causes much Extinction of the lessimproved forms of life and induces what I have called Divergence ofCharacter. In the next chapter I shall discuss the complex and littleknown laws of variation and of correlation of growth. In the foursucceeding chapters, the most apparent and gravest difficulties on thetheory will be given: namely, first, the difficulties of transitions,or in understanding how a simple being or a simple organ can bechanged and perfected into a highly developed being or elaboratelyconstructed organ; secondly the subject of Instinct, or the mentalpowers of animals, thirdly, Hybridism, or the infertility of speciesand the fertility of varieties when intercrossed; and fourthly, theimperfection of the Geological Record. In the next chapter I shallconsider the geological succession of organic beings throughout time;in the eleventh and twelfth, their geographical distributionthroughout space; in the thirteenth, their classification or mutualaffinities, both when mature and in an embryonic condition. In thelast chapter I shall give a brief recapitulation of the whole work,and a few concluding remarks.No one ought to feel surprise at much remaining as yet unexplained inregard to the origin of species and varieties, if he makes dueallowance for our profound ignorance in regard to the mutual relationsof all the beings which live around us. Who can explain why onespecies ranges widely and is very numerous, and why another alliedspecies has a narrow range and is rare? Yet these relations are of thehighest importance, for they determine the present welfare, and, as Ibelieve, the future success and modification of every inhabitant ofthis world. Still less do we know of the mutual relations of theinnumerable inhabitants of the world during the many past geologicalepochs in its history. Although much remains obscure, and will longremain obscure, I can entertain no doubt, after the most deliberatestudy and dispassionate judgment of which I am capable, that the viewwhich most naturalists entertain, and which I formerlyentertained--namely, that each species has been independentlycreated--is erroneous. I am fully convinced that species are notimmutable; but that those belonging to what are called the same generaare lineal descendants of some other and generally extinct species, inthe same manner as the acknowledged varieties of any one species arethe descendants of that species. Furthermore, I am convinced thatNatural Selection has been the main but not exclusive means ofmodification.CHAPTER 1. VARIATION UNDER DOMESTICATION.Causes of Variability.Effects of Habit.Correlation of Growth.Inheritance.Character of Domestic Varieties.Difficulty of distinguishing between Varieties and Species.Origin of Domestic Varieties from one or more Species.Domestic Pigeons, their Differences and Origin.Principle of Selection anciently followed, its Effects.Methodical and Unconscious Selection.Unknown Origin of our Domestic Productions.Circumstances favourable to Man's power of Selection.When we look to the individuals of the same variety or sub-variety ofour older cultivated plants and animals, one of the first points whichstrikes us, is, that they generally differ much more from each other,than do the individuals of any one species or variety in a state ofnature. When we reflect on the vast diversity of the plants andanimals which have been cultivated, and which have varied during allages under the most different climates and treatment, I think we aredriven to conclude that this greater variability is simply due to ourdomestic productions having been raised under conditions of life notso uniform as, and somewhat different from, those to which theparent-species have been exposed under nature. There is, also, Ithink, some probability in the view propounded by Andrew Knight, thatthis variability may be partly connected with excess of food. It seemspretty clear that organic beings must be exposed during severalgenerations to the new conditions of life to cause any appreciableamount of variation; and that when the organisation has once begun tovary, it generally continues to vary for many generations. No case ison record of a variable being ceasing to be variable undercultivation. Our oldest cultivated plants, such as wheat, still oftenyield new varieties: our oldest domesticated animals are still capableof rapid improvement or modification.It has been disputed at what period of life the causes of variability, |
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