Browne 1980

 Bronwe 1980

·         he barely referred to his botanical statistics or the long sequence of calculations which he had undertaken from 1854 to 1858. He compressed and simplified these into a few meager paragraphs, giving his readers only six pages of statistical data to fill out the discussion of "variation under nature" in Chapter 11.2 By contrast, he had originally devoted over fifty tightly written folios, with further supplementary notes and tables, to the same theme in the "big species book," Natural Selection 53

·         botanical arithmetic (a term coined by Humboldt in 1815)7 consisted merely of counting up all the species in area A and all those in area B, and itemizing how many were held in common. 55

·         Depois Brown tornou popular o calculo da media de sps por genero 56

·         the "Sketch" and "Essay" he had asserted that very little variation was seen in a "wild state," and had repeated over and over again that "most organic beings in a state of nature vary exceedingly little."' 8 Consequently, he had relied on geological and geographical changes, either directly or indirectly (the latter by stimulating a reassociation of individuals into different patterns), to "unsettle the constitution" of wild animals and plants. These "unsettling" agents were presumed analogous to the supposed effects of domestication on the reproductive systems of organisms under any sort of cultivation. Now, however, by 1854, he was convinced that organisms in their natural state really did vary without any such "unsettling" forces. Such a discovery weakened Darwin's arguments as put forward in the "Essay" where he drew a close analogy between selection in the wild and under domestication. A change in circumstances in both cases was assumed to lead to a "certain plasticity of form," and the reproductive system was stimulated to produce variant offspring upon which the selective forces operated. The crucial link was that variants, in this scheme, arose only when the reproductive system was disturbed. When armed with the knowledge that varieties pop up in the wild with no reason for their origination, Darwin saw that the central analogy of his thesis was invalid [After he “began sorting notes” in 1854] he took up the problem of how a superabundance of variation in the wild bore on his previous statements about the origination of species, and how speciation and extinction occurred when there were no geological or geographical changes necessarily invoked by the theory. Why, if there was a great deal of variation in nature, did species become extinct? Surely their variability ought to permit modifications to suit changing environments. Reopening the question of extinction, he moved to study forms which vividly represented a past history of extinguishing action. He took up the topic of aberrance 59

·         It was, he thought, the size of a genus which made it appear to be aberrant […] So the aberrant groups were, in his eyes, plainly experiencing an extinguishing force that was removing species, one by one, from what must have once been a "normal" healthy complement of species. Despite any variability which aberrant forms may show in their structure, he concluded, they must eventually become extinct. 60-1

·         Gestalt, se grupos pequenos se extinguem grupos maiores com formas variants aumentam. 61 Mecanismos de unsettling e isolamento geográfico não eram mais necessários 62. A mudança seria explicada pela pangense e cross fertilization

·         1855-7 varieties as little species: if there were many variations in wild organisms (as the barnacle work showed to be the case) then there ought to be many varieties; if there were varieties, then he could expect to fid some that were more strongly differentiated from the parent that constituted "incipient" species; and one step further on, he might also expect to find pairs or triplets of closely allied species which were neither varieties nor fully fledged species, but were somewhere in between. 63

·         Yet working through his floras, following the example of Candolle, Darwin confirmed a slight but consistent tendency for the two characters of a great geographical range and a multiplicity of individuals to appear in the larger genera 64

·         Darwin made immediate use of these results in his chapter on geographical distribution for Natural Selection, composed during the earlier part of 1856 and revised occasionally thereafter to include new information […] Under the conviction that it was the big groups in nature that were more widely spread, Darwin could explain the origin of closely related yet geographically mutually exclusive "representative" species by asserting that as a species spreads out over a great area it will meet with different conditions, which stimulate local adaptations. He could also differentiate between genera that were small because of extinction among the ranks and genera that were small because they were at the start of their "life" by determining whether there were "discrete" or "close" species in them. The latter implied a "new" genus that was varying and producing more species, while the former indicated an "old" one that was gradually dying out through the extinction of first one and then another of its species, so rendering the existing forms rather distinct from one another. Furthermore, the same argument was applied to explain why some organisms were rare and others abundant, although here Darwin conceded that there were many additional factors which allowed, say, a plethora of individuals to be found in small (and supposedly "old") genera such as the earwig and platypus. Equally, he could explain the origin of markedly disjunct species by supposing them to be "remnants" left behind when a large and correspondingly widely spread genus died out. 65-6

·         Darwin tried to explain this idea [variation leading to accumulation of adaptations therefore forming new species] by relating the quality of adaptation to some physical attribute that genera might possess, such as the capacity to range widely over diverse terrains 66

·         By 1855-6 e, the introduction of a new and good adaptation to a satellite species at the edge of a large geographical range would lead to the formation of a new line of development and, ultimately, to the rise of a new genus and the demise of the old.

·         the three main elements of Darwin's views on divergence in its finished state. First and foremost was, of course, the notion that life was readily subdivided into different classes, orders, and families, which indicated a hierarchy of relationships that evolutionary theory had to explain. Life was for Darwin a branching affair. The second element of the three which went toward his principle, and the one which has been noted most often by historians for evident reasons, was the so-called rule of the division of labor. And the final element of the triptych was that concerned with large genera and the incidence of varieties, the "boiler-house" of the whole machine. To it briefly, there was the phenomenon of divergent lines, the mode by which they were formed, and the cause and effect attributable to them. Até 1856 eles eram separados

·         O primeiro element sempre esteve lá, mas até 1854 0 there is no evidence to suggest that Darwin as yet envisaged a special mechanism for this phenomenon other than natural selection. He appears to have thought that natural selection would preserve new - and hence different - modifications that would, in turn, give rise to a cluster of species and genera that were markedly distinct from the parent form The process was effected by the geographical scheme described in 1855 and 1856. Darwin thought that a new genus arose from the introduction of some favorable adaptation to a satellite species at the edge of the geographical range covered by any one large genus.. 70-1

·         [sobre o Segundo element] Darwin was certainly not ignorant of this notion after about 1851 or 1852. But he tried at first, and especially in 1855 when the idea of a division of labor appeared often in his notes, to relate this evidently "beneficial" diversification to a combined cause of competition and the absolute abundance of resources in any one area. A division of labor was not applied to the question of divergence of character, for Darwin already had an explanation for that in peripheral differentiation. It was applied instead to the problem of accounting for the difference in the amount of life which regions could support

·         In short, although this was clearly a passage elaborating on the phenomenon of a division of labor and the diversity of associations, there was here no talk of selection favoring the most

distinct variety which might appear. Nor did Darwin at this time put these thoughts about diversity into a temporal context to illuminate how he saw the branches of the "tree" of life sprout and grow away from the root stock. Instead, the division of labor was explained in terms of natural selection and served, in turn, to explain what we might call the "biomass" of an area. He went on to argue in the closing sentences of this piece that poor regions encouraged little interspecific competition and therefore tended to support remarkably uniform floras and faunas, such as heathlands, conifer forests, or freshwater biotas. The "fertile meadow," by contrast, supported "more life," not because this was how God or anyone else had envisaged it, but because there had been a great deal of "struggle." Hence competition and the idea of "resources" between themselves accounted for the "amount of life supported in a given area."

So it appears that the division of labor, useful as it undoubtedly was, was brought into the embrace of natural selection theory as it then stood. It did not stimulate a reconstruction of that theory, as is often assumed to have been the case. Although introduced into Darwin's thoughts in 1852, it did not then or subsequently (for a few years at least) mean the same thing as it represented in the final principle of divergence. It was, we might say, adapted to its immediate context. 72

·         (terceiro: variação) Although this was a process of accumulated differentiation or divergence from the original stock, Darwin did not - before mid-1857 - invoke a principle of divergence to explain such an action. Instead he believed, as already indicated, that natural selection alone took care of the process of increasing divergence from the norm. Natural selection "made" species by picking out those variations which were well adapted to the prevailing circumstances, and pushed them on and on in some one direction. Once again, there was no talk of selection actually favoring the most diverse variety which happened to appear in any series. 73

·         This addition [OF THE PRINCIPLE OF DIVERGENCE] was finished in the early summer of 1858 and inserted into Chapter VI, "On Natural Selection," which had originally been considered complete on March 31, 1857. The most obvious explanation for this action is that Darwin was in some way ignorant of - or at least uncertain or uneasy about - the subject matter of his interpolation 74

·         Without any explanation of divergence, Darwin did two things. He emphasized the role of competition, and described the availability of suitable "places" in the "polity of nature" for every step from varietal to specific rank. Competition for these "places" insured that only a "well-adapted" variety succeeded in occupying them, and that one form was always replaced (or rather, ousted) by another that was even more "well-adapted" or "better" organized. This process of replacement appeared to move in or tend toward certain directions, a phenomenon which Darwin had difficulty in explaining. Here he fell back on the phrase "expression of variation in a right direction" to indicate - in an unintentionally teleological manner - such a movement. It was a convenient if cumbersome phrase for the trends which he was later to call divergence of character. [right deviations could fill niches in nature] 74-5

·         With a principle of divergence [] He could state that it was not "niches" or "places" that determined which variety should survive. The forms which escaped extinction did so because they were the most different [] Darwin did not have to talk of there being a readymade number of ecological niches waiting for the newly modified variants to come along and occupy them. On the contrary, he could claim that modified forms were so different from those previously in existence that they automatically created their own "places," where none had been before, on the rare occasions when they could not simply oust a lesser variant from its home. Since it was the most extreme variety which survived, the overall construction of the population would tend to become more diversified and, under the rule of the division of labor, several lines of modification would be encouraged. Hence the "amount of life" supported by any one region would become ever more diverse and complex. In sumrnary then, Darwin's initial attempt at this sixth chapter (completed March 1857) was focused on the question of explaining diverging lines of evolution - a "right direction" - without any idea of a principle which might invoke selectional advantages for those forms which happened to be most different from the ancestral stock 76

·         Darwin's idea of "large" was throughout his earlier statistics in reality simply a statement of "bigger than." He seemed to have no concept of any absolute largeness or bigness. Lubbock undoubtedly seized on these discrepancies and pointed out that Darwin was calculating relative largeness when his conclusions spoke of some real difference in size. Lubbock therefore abolished all connotations of relativity and substituted a division of the given population into two halves, one containing all the truly large genera and one the small. Now, even if people quibbled with Darwin over his definition of "large," at least he had defined it in unequivocal terms. The central question therefore remained the same one that Darwin had posed in earlier computations: Do varieties (or commonness or wide range) occur in the larger genera? But it was rephrased by Lubbock to insure that it was rigorously answered 80

·         Briefly, then, the story line runs as follows. Despite an early awareness of the phenomenon, Darwin did not see the need for a principle to explain divergence until some time between composing the "Essay" and the Origin. The recent publication of Natural Selection shows that Darwin possessed precisely the same concept of divergence in the spring of 1858 as he had in 1859, because he added a long section on this topic to his original Chapter VI, "On Natural Selection." From internal analysis of the first draft of this chapter, completed in March 1857, it appears that Darwin did not at this earlier time have any fixed notion of a "'principle" per se, although he was trying to account for the same phenomena by using only natural selection. However, as demonstrated earlier, he did possess all the elements of a "principle" in his intellectual repertoire, although these too were correlated with natural selection. Therefore, he did not have the principle in March 1857, and he did have it in the spring of 1858. We can make a further refinement of this statement by drawing in the two letters which Darwin wrote to Hooker and Gray, describing his "principle of divergence" in scant detail, during the late summer of 1857. These were dated August and September, respectively.84

·         On July 14 Lubbock introduced Darwin to a new way of doing his botanical calculations and caused Darwin to reject all that had gone before as "the grossest blunder." Momentarily startled and dismayed by this unwelcome revelation, Darwin refused to relinquish the conclusions which he had come by so conscientiously and prepared to start again. The changes which Lubbock encouraged him to make forced him to look not at the relative size of genera but at the absolute "bigness" or "smallness" that each presented. He had formerly been content to put forward results where "large" was merely a question of being bigger than the standard - as four was bigger than two - and so he called any genus large as long as it possessed more species than the control. Now, however, in July, Lubbock made him contrast absolutely large genera of a predetermined size with correspondingly small ones. This change in emphasis made Darwin shift his gaze to focus on the success which large genera so evidently enjoyed. He suddenly saw that it was not just variation and the fortuitous production of "good" adaptations which induced large genera to produce yet more and more species, but it was also their potency. Large genera really were more successful than the small. They were, in fact, the very acme of success, being more widespread and more abundant in individuals than their smaller confreres, and also turning out more varieties within which more "good" adaptations were likely to emerge. Large genera were the winners, and their size was a definite statement about their superior position in life. In a biblical turn of phrase, Darwin asserted that "in the great scheme of nature, to that which has much, much will be given." It was this notion of success and its corollary of "winner takes all" which allowed Darwin to collect and fuse together points that had up till then been separate entities in his mind. All at once things fell into place. Insofar as we can decide what may have been going on in anyone's mind, this reassortment of details can be reconstructed as follows. Through Lubbock's ministrations, Darwin suddenly recognized that large genera had more advantages than most. This was why they were widespread and numerous in individuals. Where before he had spoken only of forms being "better" adapted to their surroundings, here he had real advantages to deal with. The varieties which were produced in such numbers from the larger genera should also be superior, if his ideas about the inheritance of characters were true. Moreover, natural selection told him that "good" variations were preserved, so what happened to this wealth of superior variants? Here, he invoked the division of labor, which permitted any number of individuals to coexist as long as they were more or less distinct from one another. He was therefore confronted with a vision of many superior variants vying with each other for "places" in the economy of nature, and with the rule that only the most diversified set of individuals would manage to live together; from this state of affairs he could ascend easily to the proposal that it was the most distinct or extreme variety which was favored by natural selection. Once he had an association between the notions of "advantage" (that is, success) and "diversification," everything else followed. If selection was tending to push varieties away from one another in morphological or behavioral terms, then it must also be forcing species to develop along lines of modification that diverged from one another. Darwin could now quite clearly see that a large genus would eventually fragment into several smaller groups of species by a splitting action, and not from the pronounced superiority of a single species which then eliminated its congeners. A large genus broke into two or three sets of species, each one of which was characterized by a markedly distinct modification. But in the course of time, as he must have been aware, this sequence of growth, splitting, and growth would gradually add to the number of genera on the earth unless there was some extinction going on. The power of extinction was thus called in to maintain a semblance of balance in the history of living beings, and he reasoned that forms which were not sufficiently extreme or different must fail to reproduce their kind. Hence, by a circuitous route, Darwin arrived back at the same proposition with which he had started: that it was the most distinct form of life that was favored by natural selection. Such a revisitation may have reinforced the truth of this maxim in his own mind, for had he not reached exactly the same point from two directions - the preservation of "good" varieties and the elimination of the "bad"? 84-86

·         Under this interpretation of Darwin's work before the Origin, the emergence of a principle of divergence can be seen as the last leg of a long inquiry into the general issue of divergent evolution. Over this period Darwin approached the question from a number of angles: at times he thought the problem was solved; at others it ballooned out in a disturbing and temporarily uncontrollable fashion, forcing him to reevaluate previous arguments, to gather new information or reinterpret the old, and to provide reformulated explanations. It was a see-saw existence. Many of the phenomena of divergent evolution noted by Darwin through the years 1837-1840 found an explanation in the sketches of 1842 and 1844. Having dealt with these facts to the best of his ability, Darwin turned to a study of barnacles, no doubt to corroborate his writings in various ways. There, a whole new range of evidence was disclosed, obliging him to return to the thesis of 1844 in order to expand and alter his lines of reasoning. Divergent evolution surfaced as one of the more significant difficulties in need of a solution. In the immediate postbarnacle years he may well have explained divergence through using the concept of a division of labor, as many historians believe. But the issue was not closed. In the light of unlimited variation in nature Darwin undertook numerical studies of varieties, species, and genera, to determine the "source" of new species. Over a period of months (from 1854 to the end of 1856) this botanical arithmetic indicated that large genera were more "fertile" than the small. Darwin, never one to leave a fact unexplained or a question unasked, noted that if a "fertile" genus produces more and more species, these species will merely remain variations on a single theme unless divergence intervenes. How could the genus split into several genera? At first, before the beginning of 1857, he answered this question with a somewhat hazily formulated scheme of geographical isolation, depending for the most part on results drawn from his arithmetical calculations bearing on the wide geographical areas covered by species-rich and variable genera. Yet when he came to order these thoughts into a written synopsis for the "big species book," then firmly under way, the argument failed him. The "expression of variation in a right direction" still lacked an adequate explanation. As he was endlessly turning the problem over during the first six months of 1857, a relatively trivial event, not immediately concerned with divergence although intimately connected with his numerical studies, caused Darwin to stop in his tracks. The reorganization of his arithmetic stimulated a reorganization of the issue of divergence. The various pieces of the puzzle were reassociated and reassembled in mid-1857, producing the much-vaunted "'principle." Its explanatory power was great and Darwin was eager to provide proper substantiation; he delayed the revision of the long manuscript until the arithmetical basis of the concept was fully examined, and then hurriedly wrote up his ideas. The "principle of divergence" was emphatically part of Darwin's theory by early 1858.  88-89

·         If there is any message from this sequence of events, it is that Darwin's theories changed and evolved as he himself grew older and more mature, and that the "Essay" and Natural Selection - and indeed, the Origin as well - represent only his considered opinion on the problem of species at a given point in time. There is no good reason to believe that Darwin's ideas were static from the "Essay" onward, and no good reason to reject the possibility that the meaning of certain key concepts changed and developed during the following years 89