His notes and manuscripts provide information about decades of individual scientific practice. The textual nature of these records make them particularly amenable to computational analysis. We trained topic models on the full texts of each reading, without using any information about his publications or additional historical metadata. Our starting point for answering these questions was the previously trained topic model of his readings, as we were interested in how the readings may have influenced the writings. Topic models represent each text as a blend of different topics, with each topic being a probability distribution over the words in the collection.
The models are statistically derived from a set of texts through joint inference of their word-topic and topic-document distributions. An initially random assignment of the words to the topics is revised iteratively until the assignment stabilizes using the same method used to train the original model. Because random starting points put the algorithm on different paths in the complex terrain, running the query sampling process multiple times leads to different topic distributions for the same text.
This variability in outputs is something to be understood and harnessed, not feared, supporting different perspectives on the text. Digital methods can augment existing debates in the humanities by providing different ways of looking at the text. We approach the diversity of the sampled results by applying a clustering algorithm to the topic distributions, using the silhouette method to choose the number of clusters.
Each cluster has a different highest-probability topic. These dominant topics characterize the primary interpretation of the text for each cluster. Inspection of the topics reveals that they are immediately applicable to The Origin. For example, pigeons T49 provide a significant example for Darwin. Because the topics fit to The Origin by query sampling are derived from the model of the readings, some of the words that have a high probability for a topic in the readings are likely not to appear in The Origin at all.
Likewise, some of the geographic terms prominent in T do not appear in the book.
The Foundations of the Origin of Species Two Essays written in 1842 and 1844
Indeed, T with terms related to forests and South Asian geography and culture presents an idiosyncratic view of The Origin. Falconer is mentioned six times in the first edition of The Origin , and related issues are discussed in passages such as this, from chapter Thwaites informs me that he has observed similar facts in Ceylon. We compared the writings to the readings and each other using an information-theoretic measure of cognitive surprise—Kullback-Leibler KL divergence 9 —used in our previous study and which has proven successful in various cognitive science applications.
KL divergence is an asymmetric measure, meaning that encountering B after A may generate a different amount of surprise than encountering A after B. Asymmetric measures are useful in many contexts: for example, travel time may be the more useful measure if it will take longer to climb a mountain than to go down it, even though the distance traveled in kilometers is the same. When a symmetric measure of distance between volumes is more appropriate, we use the symmetrical Jensen-Shannon distance JSD , which is derived from the KL divergence and satisfies the mathematical properties of a distance metric.
Darwin began drafting his theory long before he started organizing his notes in With two private essays written in and , it is a historical curiosity that he would wait until to publish his work, especially as immediately after finishing the second essay he wrote to his wife, Emma, with an addendum to his will concerning publication instructions should he die before finishing his work. Figure 2 shows that with respect to the set of readings at any given time, The Origin is significantly more divergent than either of the earlier essays, and that the essay is slightly more divergent from the readings than the version.
Writing to Lyell that same day, Darwin remarked on the impressive similarity to his earlier work:. I never saw a more striking coincidence. If Wallace had my M. Finally, we look at a manuscript originally discovered with the essay at the Darwin residence in , but which was not included in The Foundations of the Origin of Species in Comparing it using JSD, we find that the draft is further from The Origin than either the sketch or essay bottom of figure 3. Moreover, the essay is further from The Origin than the essay. Measurements and models alone do not yield historical explanations.
For historians, they require validation through traditional methods, including close readings of the texts. Finally, our findings about the distances among the undated draft, the two essays, and The Origin likewise motivates new close readings of them all, with the goal of understanding why the topic models locate the undated draft as closest to the essay yet furthest from The Origin. The statement in the Autobiography that the ms. May 18th went to Maer. June 15th to Shrewsbury, and on 18th to Capel Curig During my stay at Maer and Shrewsbury five years after commencement wrote pencil sketch of my species theory.
So far there seems no doubt as to being the date of the first sketch; but there is evidence in favour of an earlier date 2. Thus across the Table of Contents of the bound copy of the ms.
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I can only account for his mistake by the supposition that my father had in. It is worth noting that in his Autobiography p. However this may be there can be no doubt that is the correct date. Since the publication of Life and Letters I have gained fresh evidence on this head. A small packet containing 13 pp. A single unnumbered page written in pencil, and is headed "Maer, May , usless"; it also bears the words "This page was thought of as introduction. The back of this "useless" page is of some interest, although it does not bear on the question of date—the matter immediately before us.
It seems to be an outline of the Essay or sketch of , consisting of the titles of the three chapters of which it was to have consisted. The reasons for and against believing that such races have really been produced, forming what are called species. The division of the Essay into two parts is maintained in the enlarged Essay of , in which he writes: "The Second Part of this work is devoted to the general consideration of how far the general economy of nature justifies or opposes the belief that related species and genera are descended from common stocks.
We may now return to the question of the date of the Essay. I have found additional evidence in favour of in a sentence written on the back of the Table of Contents of the ms. The sketch of is written on bad paper with a soft pencil, and is in many parts extremely difficult to read, many of the words ending in mere scrawls and being illegible without context.
It is evidently written rapidly, and is in his most elliptical style, the articles being frequently omitted, and the sentences being loosely composed and often illogical in structure. There is much erasure and correction, apparently made at the moment of writing, and the ms. The whole is more like hasty memoranda of what was clear to himself, than material for the convincing of others.
Many of the pages are covered with writing on the back, an instance of his parsimony in the matter of paper 1. This matter consists partly of passages marked for insertion in the text, and these can generally though by no means always be placed where he intended. But he also used the back of one page for a preliminary sketch to be rewritten on a clean sheet. These parts of the work have been printed as footnotes, so as to allow what was written on the front of the pages to form a continuous text.
A certain amount of repetition is unavoidable, but much of what is written on the backs of the pages is of too much interest to be omitted. Some of the matter here given in footnotes may, moreover, have been intended as the final text and not as the preliminary sketch. When a word cannot be deciphered, it is replaced by:— illegible ,the angular brackets being, as already explained, a symbol for an insertion by the editor.
More commonly, however, the context makes the interpretation of a word reasonably sure although the word is not strictly legible. Such words are followed by an inserted mark of interrogation? Lastly, words inserted by the editor, of which the appropriateness is doubtful, are printed thus variation? Two kinds of erasure occur in the ms. One by vertical lines which seem to have been made when the 35 pp. I have not been quite consistent in regard to these: I began with the intention of printing in square brackets all such erasures.
But I ultimately found that the confusion introduced into the already obscure sentences was greater than any possible gain; and many such erasures are altogether omitted. In the same way I have occasionally omitted hopelessly obscure and incomprehensible fragments, which if printed would only have burthened the text with a string of illegible s and queried words. Nor have I printed the whole of what is written on the backs of the pages, where it seemed to me that nothing but unnecessary repetition would have been the result.
Darwin, The foundations of the Origin of species- Contents and Introduction
In the matter of punctuation I have given myself a free hand. I may no doubt have misinterpreted the author's meaning in so doing, but without such punctuation, the number of repellantly crabbed sentences would have been even greater than at present.
In dealing with the Essay of ,1 have corrected some obvious slips without indicating such alterations, because the ms. The sections into which the Essay of is divided are in the original merely indicated by a gap in the ms. I might equally well have made sections of what are now subsections, e. Selection p. But since the present sketch is the germ of the Essay of , it seemed best to preserve the identity between the two works, by using such of the author's divisions as correspond to the chapters of the enlarged version of With this exception the ten sections of the Essay of correspond to the ten chapters of that of The Origin of Species differs from the sketch of in not being divided into two parts.
But the two volumes resemble each other in general structure.
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Both begin with a statement of what may be called the mechanism of evolution,—variation and selection: in both the argument proceeds from the study of domestic organisms to that of animals and plants in a state of nature. This is followed in both by a discussion of the Difficulties on Theory and this by a section Instinct which in both cases is treated as a special case of difficulty. If I had to divide the Origin first edition into two parts without any knowledge of earlier ms. VI, Difficulties on Theory. A possible reason why this part of the argument is given in Part I of the Essay of may be found in the Essay of , where it is clear that the chapter on instinct is placed in Part I because the author thought it of importance to show that heredity and variation occur in mental attributes.
The whole question is perhaps an instance of the sort of difficulty which made the author give up the division of his argument into "two Parts when he wrote the Origin. From this point onwards the material is grouped in the same order in both works: geographical distribution; affinities and classification; unity of type and morphology; abortive or rudimentary organs; recapitulation and conclusion. In enlarging the Essay of into that of , the author retained the sections of the sketch as chapters in the completed presentment. It follows that what has been said of the relation of the earlier Essay to the Origin is generally true of the Essay.
In the latter, however, the geological discussion is, clearly instead of obscurely, divided into two chapters, which correspond roughly with Chapters IX and X of the Origin. The fact that in , seventeen years before the publication of the Origin, my father should have been able to write out so full an outline of his future work, is very remarkable.
In his Autobiography 1 he writes of the Essay, "But at that time I overlooked one problem of great importance This problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified. But at p. The passage referred to is: "If any species, A , in changing gets an advantage and that advantage A will go on beating out other forms, it might come that A would people the earth,—we may now not have one descendant on our globe of the one or several original creations 1.
What I wrote 2 on this subject in is I think true: "Descent with modification implies divergence, and we become so habituated to a belief in descent, and therefore in divergence, that we do not notice the absence of proof that divergence is in itself an advantage. The fact that there is no set discussion on the principle of divergence in the Essay, makes it clear why the joint paper read before the Linnean Society on July 1, , included a letter 3 to Asa Gray, as well as an extract 4 from the Essay of It is clearly because the letter to Gray includes a discussion on divergence, and was thus, probably, the only document, including this subject, which could be appropriately made use of.
It shows once more how great was the importance attached by its author to the principle of divergence. I have spoken of the hurried and condensed manner in which the sketch of is written; the style of the later Essay is more finished.
The 1842 “Sketch” and 1844 “Essay”
It has, however, the air of an unconnected ms. It has not all the force and conciseness of the Origin , but it has a certain freshness which gives it a character of its own. It must be remembered that the Origin was an abstract or condensation of a much bigger book, whereas the Essay of was an expansion of the sketch of It is not therefore surprising that in the Origin there is occasionally evident a chafing against the author's self-imposed limitation.
Whereas in the Essay there is an air of freedom, as if the author were letting himself go, rather than applying the curb. This quality of freshness and the fact that some questions were more fully discussed in than in , makes the earlier work good reading even to those who are familiar with the Origin. The writing of this Essay "during the summer of ," as stated in the Autobiography 1 , and "from memory," as Darwin says elsewhere 2 , was a remarkable achievement, and possibly renders more conceivable the still greater feat of the writing of the Origin between July and September It is an interesting subject for speculation: what influence on the world the Essay of would have exercised, had it been published in place of the Origin.
The author evidently thought of its publication in its present state as an undesirable expedient, as appears clearly from the following extracts from the Life and Letters , vol. I have just finished my sketch of my species theory. If, as I believe, my theory in time be accepted even by one competent judge, it will be a considerable step in science. I wish that my sketch be given to some competent person, with this sum to induce him to take trouble in its improvement and enlargement.
I give to him all my books on Natural History, which are either scored or have references at the end to the pages, begging him carefully to look over and consider such passages as actually bearing, or by possibility bearing, on this subject. I wish you to make a list of all such books as some temptation to an editor. I also request that you will hand over to him all those scraps roughly divided into eight or ten brown paper portfolios. The scraps, with copied quotations from various works, are those which may aid my editor.
I also request that you, or some amanuensis, will aid in deciphering any of the scraps which the editor may think possibly of use. I leave to the editor's judgment whether to interpolate these facts in the text, or as notes, or under appendices. I consider that for this the editor is bound to get the sketch published either at a publisher's or his own risk. Many of the scraps in the portfolios contain mere rude suggestions and early views, now useless, and many of the facts will probably turn out as having no bearing on my theory.
As the editor must be a geologist as well as a naturalist, the next best editor would be Professor Forbes of London. The next best and quite best in many respects would be Professor Henslow. Dr Hooker would be very good. The next, Mr Strickland 1. If none of these would undertake it, I would request you to consult with Mr Lyell, or some other capable man, for some editor, a geologist and naturalist. The following note seems to have formed part of the original letter, but may have been of later date:. Without an editor will pledge himself to give up time to it, it would be of no use paying such a sum.
The idea that the sketch of might remain, in the event of his death, as the only record of his work, seems to have been long in his mind, for in August, , when he had finished with the Oirripedes, and was thinking of beginning his "species work," he added on the back of the above letter, "Hooker by far best man to edit my species volume. August I have called attention in footnotes to many points in which the Origin agrees with the Foundations.
One of the most interesting is the final sentence, practically the same in the Essays of and , and almost identical with the concluding words of the Origin. I have elsewhere pointed out 2 that the ancestry of this eloquent passage may be traced one stage further back,—to the Note Book of I have given this sentence as an appropriate motto for the Foundations in its character of a study of general laws. It will be remembered that a corresponding motto from Whewell's Bridgewater Treatise is printed opposite the title-page of the Origin of Species.
Mr Huxley who, about the year , read the Essay of , remarked that "much more weight is attached to the influence of external conditions in producing variation and to the inheritance of acquired habits than in the Origin.