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Evolution and the Nature of Science98 •

On the Origin of Species

Charles Darwin (1859)

Introduction

When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distri-bution of the inhabitants of South America, andin the geological relations of the present to thepast inhabitants of that continent. These factsseemed to me to throw some light on the originof species—that mystery of mysteries, as it hasbeen called by one of our greatest philosophers.On my return home, it occurred to me, in 1837,that something might perhaps be made out onthis question by patiently accumulating andreflecting on all sorts of facts which could possi-bly have any bearing on it. After five years workI allowed myself to speculate on the subject, anddrew up some short notes; these I enlarged in1844 into a sketch of the conclusions, which thenseemed to me probable; from that period to thepresent day I have steadily pursued the sameobject. I hope that I may be excused for enter-ing on these personal details, as I give them toshow that I have not been hasty in coming to adecision.

My work is now nearly finished; but as it willtake me two or three more years to complete it,and as my health is far from strong, I have beenurged to publish this Abstract. I have more espe-cially been induced to do this, as Mr. Wallace,who is now studying the natural history of theMalay archipelago, has arrived at almost exactlythe same general conclusions that I have on theorigin of species. Last year he sent to me a mem-oir on this subject, with a request that I wouldforward it to Sir Charles Lyell, who sent it to theLinnean Society, and it is published in the thirdvolume of the Journal of that Society. Sir C. Lyelland Dr. Hooker, who both knew of my work—the

latter having read my sketch of 1844—honouredme by thinking it advisable to publish, with Mr.Wallace’s excellent memoir, some brief extractsfrom my manuscripts.

In considering the Origin of Species, it is quiteconceivable that a naturalist, reflecting on themutual affinities of organic beings, on theirembryological relations, their geographical distri-bution, geological succession, and other suchfacts, might come to the conclusion that eachspecies had not been independently created, buthad descended, like varieties, from other species.Nevertheless, such a conclusion, even if wellfounded, would be unsatisfactory, until it could beshown how the innumerable species inhabitingthis world have been modified, so as to acquirethat perfection of structure and coadaptationwhich most justly excites our admiration.Naturalists continually refer to external condi-tions, such as climate, food, etc., as the only pos-sible cause of variation. In one very limitedsense, as we shall hereafter see, this may be true;but it is preposterous to attribute to mere exter-nal conditions, the structure, for instance, of thewoodpecker, with its feet, tail, beak, and tongue,so admirable adapted to catch insects under thebark of trees. In the case of the misseltoe, whichdraws its nourishment from certain trees, whichhas seeds that must be transported by certainbirds, and which has flowers with separate sexesabsolutely requiring the agency of certain insectsto bring pollen from one flower to the other, it isequally preposterous to account for the structureof this parasite, with its relations to several dis-tinct organic beings, by the effects of externalconditions, or of habit, or of the volition of theplant itself.

The author of the ‘Vestiges of Creation’ would,I presume, say that, after a certain unknownnumber of generations, some bird had given birthto a woodpecker, and some plant to the misseltoe,and that these had been produced perfect as we

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now see them; but this assumption seems to meto be no explanation, for it leaves the case of thecoadaptations of organic beings to each other andto their physical condition of life, untouched andunexplained.

It is, therefore, of the highest importance togain a clear insight into the means of modifica-tion and coadaptation. At the commencement ofmy observations it seemed to me probable that acareful study of domesticated animals and of cul-tivated plants would offer the best chance ofmaking out this obscure problem. Nor have Ibeen disappointed; in this and in all other per-plexing cases I have invariable found that ourknowledge, imperfect though it be, of variationunder domestication, afforded the best and safestclue. I may venture to express my conviction ofthe high value of such studies, although they havebeen very commonly neglected by naturalists.

No one ought to feel surprise at muchremaining as yet unexplained in regard to the ori-gin of species and varieties, if he makes dueallowance for our profound ignorance in regardto the mutual relations of all the beings whichlive around us. Who can explain why one speciesranges widely and is very numerous, and why

another allied species has a narrow range and israre? Yet these relations are of the highestimportance, for they determine the present wel-fare, and, as I believe, the future success andmodification of every inhabitant of this world.Still less do we know of the mutual relations ofthe innumerable inhabitants of the world duringthe many past geological epochs in its history.Although much remains obscure, and will longremain obscure, I can entertain no doubt, afterthe most deliberate study and dispassionate judg-ment of which I am capable, that the view whichmost naturalists entertain, and which I formerlyentertained—namely, that each species has beenindependently created—is erroneous. I am fullyconvinced that species are not immutable; butthat those belonging to what are called the samegenera are lineal descendants of some other andgenerally extinct species, in the same manner asthe acknowledged varieties of any one species arethe descendants of that species. Furthermore, Iam convinced that Natural Selection has been themain but not exclusive means of modification.

On the Origin of Species by Means of Natural Selection.London. 1859.

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