Kohn (1980)

Theories to work by: rejected theories, reproduction, and Darwin's path to natural selection.

• January 1980 
• Studies in History of Biology 4:67-70

Intro

·         Não  é possivel reconstruir o processo de darwin como um caminho gradual em direção a origem pq isso força a ignorar aspectos importantes 68

·         Theoretical speculation, for Darwin, seems most often to be a matter of testing alternative explanations agaisnt deepley held criteria. In the case of reproduction, his “theory to work by” had to embody some aspect of reproduxtion that functions in all matings and that does not disrupt the hereditary structure of the organism. This is a simple criterion, it is also patentlu the principle of uniformity appleied to reproduction. Nevertheless, he applied it consistently once he becme a transformist. It determined which explanations he found acceptable and which he recected. 68

·         Rejetiou sel. Art. Pq n batia com o critério reprodutivo

Darwin as a creationist

·         Análise de Lyell e como as sps eram apresentadas ali. Ele era contra lamarck 69

·         Citação do geological notes 1835 lidando com a questão das “expectativas de vida” das sps. Espécies fixas imutáveis com pops estáveis e criadas. 70

·         Citação quanto a substituição dos animias na américa do sul. Sem catastrofismo devido ao gradualismo do registro fóssil, “sps may perish as well as individuals”. Tbm rola a menção das representative species (hare e agouti ocupando o mesmo “espaço” em lugares distintos) entretanto os dados geog´raficos eram utilizados aqui de maneira unicamente criacionista 70-1

·         In summary, then, this is Darwin’s point of departure in 1835. He was a convinced Lyellian, which means he was committed to 1 the immutability of species 2 local extinction and local creation as opposed to catastrophism 3 extinction proceeding gradually by the successive deaths of individuals 4 the concept of local species distribution. We find no stance taken on adaptation, but may presume that local species, such as the Cavia, were perfectly adapted. And, finally, he was committed to 5 the balance of nature as a standard of argumentation on species questions. 71-2

·         O carater especulativo teorico observacional permace. Seu framework teórico era emprestado de suas influencias. Nada de original. O crescimento do transformismo em darwin pode ser interpretado como sua luta contra o paradigma lyelliano.

Darwin becomes a transformist saltation and species senescence

·         No red notebook Darwin começa a mostrar sinais de transformismo oriundos dos problemas apresentados pela sua coleção.

·         Descrição do caso do avestruz [na vdd é uma ema]. Dois problemas: 1. Como não ocorre exclusão competitiva entre seres parecidos; 2. Sendo as sps tão próximas por tão súbitas e não graduais conforme Lamarck? (hipóteses – uma extinguir a outra não convenceu; mudança progressiva também não; logo considera-se mudança saltacional)73-5

·          Paralelamente a Macrauchenia oferecia um caso de extinção enquanto sua contraparte menor, o guanaco ou a lhama, sobreviveram. (hipóteses – extinção por mudança externa recusada; tempo finito das sps considerado) 75

·         Mecanismo até agr: senescência das sps e inosculação saltacional. 76

·         Senescência faz darwin questionar a adaptação perfeita dos organismos.

·         Crítica a Limoges que não teve acesso ao RN.

·         In summary, this is the status of Darwin’a thinking in the spring of 1837: 1. He is tentatively using transmutation as a working hypothesis. 2. He is shying away from gradual changes in circumstances as a framework for explaining transmutation. In other words, he is avoiding Lamarckian arguments 3. A) his mechanism for origin is saltation. B) he has considered descent from a common ancestor, i. e. the first fork of the branching phylogeny 4. He explains extinction, t least mass extinction, by species senescence. 5. He doubts close or perfect adaptation. 6 his relation to lyell and, by implicaton, to the portions of the natural theology tradition that lyell embodied, has shifted from one of docile disciple to harsh critic. 7. He relates reproduction to transmutation by trying to unite the diversity of asexual and sexual reproductive modes around the notion that  a species is but a single individual. 80-1

Darwin’s first explanatory theory: sexual reproduction as evolutionary mechanism

·         Ou Darwin’s sexual mechanism and island theory of transmutation.

·         Sumário dos cadernos 81-3

·         Estrutura do caderno B segundo Kohn: 1. The physical enironment has two properties a. it is constantly and gradually changing b it directly induces variability in living organism 2 variability has two properties a it is hereditary b it is adaptive 3 sexual reproduction is absolutely disticn from asexual reproduction a only in sexual reproduction do progeny show variability b only in sexual reproduction (crossing)  is variability spread to other members of the species 4 to survive, species must adapt to adapt means to be transformed 5 only by sexual reproduction, which incorporates adaptative hereditary variability can species be transformed.

·         Darwin conclui reprodução é a causa final da vida pois permite variação e adaptação, morte elimina os traços negativos

·         Sobre a constância das sps em longos trechos – Merely by framing a question int erm s of the containment of any sort of superabundance, Darwin was taking a step toward natural selection. Surgida da aplicação das observações domésticas a natureza 88

·         1  darwin recognizes sexually produced variability as a force though a force that might be containe 3 this recognition may have channeled his yhought in a selectionist direction by bringin him to search for mechanisms of containment 3 this research was initiated because his sex based mode olf variability which is derived from horticulture, did not fit his view of limited bariability in nature. 88-9

·         Problema da consistência das sps mesmo com variação em ambientes contíguos resolvido com blending inheritance no cruzamento. In blending, when individuals cross, the variations generated by sex are eventually distributed among the inhabitants of the “country”. Hence, the apparent constancy of species. 89-90

·         It is important to remember that for Darwin in 1837, and indeed in 1859, blending does not stop evolution. It is responsible for the containment, not the eradication, of variability. Blending and crossing simply distribute an unstanchable supply of variability that the species requires in order to change, given a “world subject to cycle of change” (B2:3). Indeed, blending is quite compatible with Darwin’s vision of transformism. Species appear to be constant, but they are changing slowly all the time. […] 90

·         Now this was the first part of Darwin’s position on formation of new species, in July 1837. The view of transmutation we get from this is of an insensible gradation of species over time=what we might today call phyletic evolution. The net effect is Lamarckian in the limited sense that the formation of new species is a gradual linear process, occurring over a long lapse of time. Just the sort of gradualism Darwin rejected in RN, now had become plausible within his sexual mechanism. 90

·         Isolamento e inbreeding são o suficiente para alterar a raça. 90

o   In Darwin’s new model, isolation replaced blending as a mechanism of containment. This is an extremely important trnasiiton, beacue no only was the containing element, it was now numbers (“increase slowly”), not vairants, that were contained.  91

·         Predadores também foram considerados para contenção 91

·         Isolamento promove a multiplicação acelerada das sps e funcionava como defesa para a transmutação (Lyell e os domésticos egípcios discutido detalhadamente). 92

·         What the isolation model, im sum, permitted Darwin to do was to transform Lyell’s (and his contemporaries’) deviation from type into a formula for derivation from type. 92

·         Duas propostas de especiação portanto: origem direta por acumulaão de variações e por isolamento. Isolamento servia para separar populações e acelerar o processo de especiação. Ambas as propostas eventualmente se fundem [não sei se isso é tão claro assim]. 94

·         Árvore ou coral resultante da biogeografia e reprodução.

·         Discussão sobre o conceito inicial de Darwin quanto a adaptação: é maniqueísta, não competitivo; interespecífico; adaptação como processo (Lamarck) e como estado de ser (lyell, paley); há uma segregação entre caracteres hereditários e adaptativos mas com conexão (explica caracteres inuteis).

·         Ironically, in na importante sense, that Darwininims of 1837 was not far removed from the Lamarckism of 1809. 98

·         […] In July 1837, his solution was to accept perfect adaptation, with the revisions we have already pointed out, but also to hold that not all characters participate in making the organism adapted. This further revision was dictated by the fact that thransformism must account not only for change but also for the accumulation of change . the organism’s survival in the present depended on its perfect adaptation, but the organism’ constitution also reflected its past. Hence, some ancient characters, which were once adaptive (i.e. were ‘necessary to one forefather’ b14),becom invariant ‘due to hereditary taint’ (b46). The effect of this formulation was to remove anything but perfectly adaptive characters from the forefront of darwin’s attempt to explain evolutionary change […]. 99

·         Extinção como resultado do equilíbrio natural do mundo para compensar superabundância da origem, ainda interespecífico no entando, portanto sem ênfase na luta pela vida. Também derivado de Lyell, mas invertido.

·         Kohn considera o que foi apresentado no caderno b como uma primeira teoria. Tendo a concordar.

·         Vários comentários sobre a tese de Limoges, Vorzimer, Gruper, Mayr e Ghiselin e outros autores quanto às interpretações desses escritos primitivos.

Darwin without Malthus: the sexual theory repeated and extended.

·         Darwin usava reprodução como uma metáfora para sua teoria reprodutiva de transmutação de três formas 1. Metáfora para filogenia 2. Simultaneamente como o primeiro e como uma alusão a teoria sexual da descendência. 3. Como alusão a sua teoria de descendência por geração. 115

·         Analogias entre indivpiduos e sps continuam pós 1837 como 1. Recasting the analogy between individual life span and species extinction into a larger analogy between reproduction and the origin fo species (i.e. golden pippin). 2. Analogies between indivudals and species based on the balance of nature (sps geram a si msms em falta de oportunidades adaptativas). 3. Analogies between family lineages and phylogeny (famílias individuais como analogia as categoriais taxonômicas) 116

·         O mecanismo sexual continuou a ser usado por dariwn

·         Em 1838 ainda havia problemas com adaptação. Darwin achava que ele surgia quando havia oportunidade 123

·         Exemplo de seleção sexual ainda em 1838 com um leve indíco de struggle. 124

·         Inércia hereditária. Quanto mais tempo a característica na sps mais ela fica fixada. Se algo fica mto fixado para responder as mudanças então a sps é extinta 127

·         The principle that habit precedes structure is the logical parallel to and chronological ransformation of Darwin’s separation of adaptation and heredity, applied to habit. Behavioral changes that meet new conditions and exploit new opportunities, as in the situation of “fish being excessively abundant & tempting the Jaguar to use its feet in swimming” (C62-63), were but the first outposts of adaptation. After the vanguard of changed habit would follow in time the structures, the morphological contrivances, and the hereditary insticnts to support and perfect the adaptation. But such structures, such permanent and characteristic features of the species, must be fixed in heredity. 131-2

·         Hibridação produz monstruosidades. Hibridity is a disruptive event and hence a rare, anomalous one in nature. Hence it was excluded as an adaptive mechanism.

·         Saltações e monstruosidades não contribuam tbm. Pois... the hereditary constitution of the organism is so constructed as to constrain the magnitude of change possible in any generation. Excessive variation is repugnant to nature and to Darwin.

·         […] Darwin did not formulate the theory of natural selection by constructing an analogy between the process of artificial selection and the mechanism of transmutation in nature. [….] I would onl add the fact that in at least wight instances in the C and D notebooks Darwin made this rejection very explicit [e em d107]. 138

·         A analogia existia mas n era útil pois não explicava a sobrevivência das formas na natureza.

·         We have seen that Darwin rejected hybridity, marked variation, and artificial selection as disruptive alterations of the normal processes of sexual reproduction. In a sense, they are all monstrous and Darwin speaks of them in this way, this is the negative side of his reproductive criterion. From this we have inferred that he would consider as acceptable only those reproductive phenomena that were normal. A positive statement of the criterion would be that the workable theory myst be based on reproductive evnts that occurred in each mating and that were consistent with slow, small adaptive changes to a gradually chaingin environment. Both sexual theory which we have examined in the past two section, and natural selection fulfill these requirement. Thy both utilize the trifling variarions that occur in every mating. And natural selection is further based on the most commonplace of all reproductive phenomena: simple multiplication.

·         Interms o the use Darwin made of reproduction, the trhansition between the early b notebook and the discovery of natural selection inD is amovement between two stable states, punctuated by occasional rejections of destabilizing alternatives. Ido not maintain that the reproductive criterion was the only operative one. Reproduction alon could not explain adaptation, a lesson Darwin slowly learned. Nevertheless , as I have tried to shoe, suca criterion did exist for him, and it accounts in part for the particular path his development took 140

·         Malthus: pessimista e “materialização” do homem, conflito oposto ao otimismo de paley. Pulo do gato é perceber a luta intrasps 142-3

·         Ler Malthus fez Darwin questionar o equilíbrio natural (consequencia em sua visão sobre extinção e adaptação); introduz competição intrasps; e adaptação

o   In natural theology, the adaptation of species was like fitting a round peg into a neatly preordained round hole. For Lyell, the holes were always changing shape and the species showed some flexibility. Ford Darwin, after Malthus, adaptation became a matter of sharp-edged wedges pounded into narrow cracks. Adaptation was no longer a temperate, quiescent process. It became the result of a fierce contest that differentiated among the well adapted, where even “a grain of sand turns the balance.” 145-6

·         Até ler Malthus, Darwin até tinha exemplos de competição intra sps e inter, mas não compreendia os efeitos produndos dela na origem das spsp. 148

·         Paradoxo do percebimento 149-50

·         RN mostra o rebelious act e isolamento intelectual de Darwin 151

o   Let us consider the ways in which this theory, which we have called sexual theory, precluded a sensivity to struggle. First of all, like speies senescence and saltation, it relied on inherent transformist tendencies. The “mechanism” at the core of the sexual theory was the ad hoc assumption that the variation observed in species is automatically adaptive. If adaptation to environmental change is an expression of a species’ inherent tendencies, what need is there to dwell on extrinsic phenomena such as the struggle between individuals? Thus, the central principle of Darwin’s prevailing theory was in itself an important impediment.

o   Other aspects of darwin’s position operated in the same direction. Most important is the fact that his explanation of transformism was on longer in such violent opposition to the orthodox perception of nature. By July 1837, he had calmed down and had accepted, once afain, important parts of the old view. In particular, he had made his peace with Lyell’s explanation of extinction. This put Darwin in the position of adhering to explanations of extinction and origin that were qualitatively different. He had come to accept that th causes of extinctionwere extrinsic: the product of the action of the environment on the organism; whereas, he treated the process of adaptation as a harmonious entrainment between the intrinsic tendency to vary and the mutable face of the earth. He had also made his peace with the concept of perfectadaptation by making imperfect adaptation a function of hereditary fixation. This interpretation deflected his attention from an issue that could have led to awareness of differential adaptation. Once again the self consistent internal structure of his theory built a wall to realizing the importance of struggle.

o   In summary, I think the paradox of realization can be explained by the joint action of two forces: 1 the coherence of darwin’s nonselectionisti theory and hence the power it held ober him; 2 the specific elements of darwin’s theory and of his fundamental assumptions that focused his attention away from struggle.

o   […] My conclusion is that the formulation of these explanations gave him practice in the art of theory making. It is this process of constructing theory after theory that Is important. Since Darwin did not spontaneously realize the importance of struggle, despite his long consciousness of the phenomenon, this practice was apparently the only form of preparation that could have brought him to understand natural selection. 152-4.