Generative conception

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Generative conception

  1. 1. The GenerativeConception of SpeciesJohn S.WilkinsUniversity of QueenslandWhat I’m going to do - focus on modern period, and particularly the French and English naturalistsof the 18th and 19th Cs.
  2. 2. OutlineThe StandardView of the History of SpeciesEssentialismTypologyFixismSpecies as Similarity GenerationClassicalEarly Natural HistoryThe 18th and 19th CenturiesConclusionsOne Concept (in biology) many ConceptionsRun through an intensive fire of quotations (Churchill - intense versus intensive). This is because thestandard view that I’m going to contradict is so well established that if you know it you may think Iam making this up. We need them to establish what the early view of species actually was.
  3. 3. The StandardView:EssentialismMayrian essentialism:“Western thinking for more than 2,000 years after Platowas dominated by essentialism. For Plato and hisfollowers, variable classes of entities consist of imperfectreflections of a fixed number of constant, discontinuouseide or essences.In 1859 Darwin introduced the entirely new concept ofvariable populations composed of unique individuals.Toward a new philosophy of biology 1988:15
  4. 4. The StandardView:EssentialismAristotle fingered as the culprit as well, bySimpson, Mayr and Hull.Based on the use of eidos (= species or form)The Standard View developed over a period of about 15 years, beginning with the centenary of theOrigin in 1958
  5. 5. The StandardView:TypologyMayrian typology:Species types can mean species essences[TaNPoB, 407] separated by “bridgeless gaps”Ideal morphologists’ archetypes can bedescriptive“Type” plays a role that is somewhat tangential to our story here, except that in conflating thenotions of type and essence, Mayr managed to effectively relegate any use of types by pre-Darwinian biologists to evidence for his claim that essentialism was pre-evolutionary (and byimplication that any modern biologist who used types was anti-Darwinian.It should be noted this is not true, as even Darwin used types in his own systematics, and he had tomake an exception from the equation for the ideal morphologists in the early nineteenth century.
  6. 6. The StandardView:FixismMayrian fixismThese essences (natures, eide) are identical forall the members of a class or species.They areunchanging, all deviations being “accidents”.Thisphilosophy, of course, made evolutionimpossible. [TaNPoB, 186]Mayr and Hull hold that essentialism is the motive for fixity of species. Since essences cannot, bydefinition, change, if species had essences they wouold be fixed.
  7. 7. The StandardViewEssentialism ➔ Typology ➔ FixismSpecies have natures, definitions and are staticDarwin changed all that, with polytypy, historyand individuality.So, the issues that we will address today are that essentialism leads to fixism, that species haveessential natures that can be captured by definitions, and that it all changed with Darwin. I’m goingto argue that all three claims are in historical fact, false.To pre-empt a problem that some may have philosophically, I should note that arguments againstspecies essentialism in the modern literature do not rely upon this historical claim. As I will laterassert, essentialism *is* a problem in modern literature, which I am going to arbitrarily set as 1900,for reasons I will give then.What I am claiming here is that there is a shared conception, pretty much from Aristotle to themid-19th century, about species that was shaken loose only when the discussions of heredity tookplace at that time, and species were reconceived in terms of heredity. Now there are people who usethe metaphysical notions of essences, substance and form throughout this period to conceptualisespecies. This was the common heritage of western philosophy and it would be odd if they didn’t.What is odder still, though, is how *few* people apply these metaphysical notions, or anythingmuch resembling them, to natural history. I’m going to try to demonstrate that until 1900, peopleroutinely and overtly differentiated logical species which do have definitions from natural specieswhich have descriptions and diagnostic criteria.
  8. 8. Classical speciesAmbiguities about eidos/species and genos/genusThe role of generation of kindsGenesis 1AristotleEpicureanismMedieval (Frederick II)Distinction between logical species, and natural species not around until Ray.But distinction often made between “natural species” and “formal” species in logic.Use of terms indifferently depending on what the topic was.
  9. 9. AristotleCopulation takes place naturally between animals of the same kind [homogenesin]. However,those also unite whose nature is near akin and whose form [eidei] is not very different, if theirsize is much the same and if the periods of gestation are equal. In other animals such cases arerare, but they occur with dogs and foxes and wolves and jackals; the Indian dogs also springfrom the union of a dog with some wild dog-like animal.A similar thing has been seen to takeplace in those birds that are salacious, as partridges and hens.Among birds of prey hawks ofdifferent form [eidei] are thought to unite, and the same applies to some other birds. … Andthe proverb about Libya, that Libya is always producing something new, is said to haveoriginated from animals of different species [homophulē allēlois] uniting with one another inthat country, for it is said that because of the want of water all meet at the few places wheresprings are to be found, and that even different kinds unite [homogenē] in consequence.Of the animals that arise from such union all except mules are found to copulate again witheach other and to be able to produce young of both sexes, but mules alone are sterile, for theydo not generate by union with one another or with other animals.The problem why anyindividual, whether male or female, is sterile is a general one, for some men and women aresterile, and so are other animals in their several kinds, as horses and sheep. But this kind, ofmules, is universally so.The causes of sterility in other animals are several.[Generation of Animals II.8 746a29–746b22]Aristotle hardly ever speaks of anything we would now call species of organisms. He uses the termsgene (genera) and eide (species), because as logical concepts it depends very much on what isbeing discussed. If it is something differentiated out of a larger class of things, like organs, he willspeak of the “eidos” of the eye. If it is a class encompassing several subkinds, then he will use theterm “genos” or variants. His student Theophrastus, in the seminal work on botany, is less careful,and will indifferently use them even in the same paragraph, perhaps for stylistic reasons.Sometimes Aristotle, as in this passage, will use the term “eidos” simply to mean form.Of note here is that this passage ties kinds of organisms to their shared generative powers, viacopulation. He is not universal about this because he thinks a good many animals spontaneouslygenerate, but when they propagate normally, generative propensities are crucial to their kindness.Note that Aristotle is not, here, a species fixist. He allows in a widely quoted passage from Pliny toBuffon that new species can form via hybridisation. [Libya is Africa, apart from Egypt]
  10. 10. Epicurus/LucretiusIf things could be created out of nothing, any kind of things could beproduced from any source. In the first place, men could spring from the sea,squamous fish from the ground, and birds could be hatched from the sky;cattle and other farm animals, and every kind of wild beast, would bearyoung of unpredictable species, and would make their home in cultivatedand barren parts without discrimination. Moreover, the same fruits wouldnot invariably grow on the same trees, but would change: any tree couldbear any fruit. Seeing that there would be no elements with the capacity togenerate each kind of thing, how could creatures constantly have a fixedmother? But, as it is, because all are formed from fixed seeds, each is bornand issues out into the shores of light only from a source where the rightultimate particles exist.And this explains why all things cannot be producedfrom all things: any given thing possesses a distinct creative capacity. [On theNature ofThings Book I. 155-191]The atomists also had a generative conception of species. This passage from Lucretius is much laterthan Aristotle but most commentators think that he is faithfully reporting Epicurus’ views shortlyafter or even contemporaneous with Aristotle. Note that Epicurus, however, is denying spontaneousgeneration. This is the first clear statement of the generative conception.
  11. 11. MedievalRarely interested in natural species except fortheological homiliesExceptions:HerbalsAnimal Breeding TractsFrederick II (c1200) – keen falconer (De ArteVenandi Cum Avibus)Criticises Aristotle for credulityBirds are same species if they will interbreed
  12. 12. Frederick on speciesInter alia, we discovered by hard-won experience that the deductions of Aristotle, whomwe followed when they appealed to our reason, were not entirely to be relied upon,more particularly in his descriptions of the characters of certain birds.There is another reason why we do not follow implicitly the Prince of Philosophers: hewas ignorant of the practice of falconry – an art which to us has ever been a pleasingoccupation, and with the details of which we are well acquainted. In his work “LiberAnimalium” we find many quotations from other authors whose statements he did notverify and who, in their turn, were not speaking from experience. Entire conviction of thetruth never follows mere hearsay....[It] must be held, then, that for each species, and each individual of the species, Naturehas provided and made, of convenient, suitable, material, organs adapted to individualrequirements. By means of these organs the individual has perfected the functions needfulfor himself. It follows, also, that each individual, in accordance with the particular form ofhis organs and the characteristics inherent in them, seeks to perform by means of eachorgan whatever task is most suitable to the form of that organ.
  13. 13. Initial uses of speciesamong early naturalistsAndreas Cesalpino, 16thCThat according to the law of nature like always produces like and that whichis of the same species with itself. [Quaestionum peripateticarum, libriV, ch 13]We seek similarities and dissimilarities of form, in which the essence(‘substantia’) of plants consists, but not of things which are merely accidentsof them (‘quae accidunt ipsis’). [ch 14]Since science consists in grouping together of like and the distinction ofunlike things, and since this amounts to the division into genera and species,that is, into classes based on characters (differentiae) which describe thefundamental nature of the things classified, I have tried to do this in mygeneral history of plants, … [De plantis]What have we skipped over in the last 400 years? Universal language project, from Bacon to Wilkins,but not much natural history. The Reformation got in the way of a lot of natural history, and sciencetended to focus on other matters such as medicine and anatomy.Here it is clear that Cesalpino did think species had a kind of logical essence, but then, the idea of anatural species was not yet in play. Over the next century, the term species began to be widelyused, first by Bauhin and Fuchs, and eventually by Ray.
  14. 14. Robert HookeBut to refer this Discourse of Animals to their properplaces, I shall add, that though one should suppose, orit should be prov’d by Observations; that several ofthese kinds of Plants are accidentally produc’d by acasual putrifaction, I see not any great reason toquestion, but that, notwithstanding its own productionwas as ‘twere casual, yet it may germinate andproduce seed, and by it propagate its own,that is, a new Species. [Micrographica 1665]While discussing the spontaneous generation of organisms, still believed in at this time, Hookemakes some passing comments that indicate the generative conception was still in play.
  15. 15. John Ray’s 1686definitionIn order that an inventory of plants may be begun and a classification of themcorrectly established, we must try to discover criteria of some sort fordistinguishing what are called “species”.After long and considerableinvestigation, no surer criterion for determining species has occurred to methan the distinguishing features that perpetuate themselves inpropagation from seed.Thus, no matter what variations occur in theindividuals or the species, if they spring from the seed of one and the sameplant, they are accidental variations and not such as to distinguish a species …Animals likewise that differ specifically preserve their distinct speciespermanently; one species never springs from the seed of another nor viceversa. [Historia plantarum generalis.The Latin of the definition is Nulla certioroccurit quam distincta propagations ex semine.]… the number of species being in nature certain and determinate, as is generallyacknowledged by philosophers, and might be proved also by divine authority,God having finished his works of creation, that is, consummated the number ofspecies in six days. [Letter]
  16. 16. Linnaeus’ lack ofessentialismNever defined “species” – seemed to rely on RayHowever, some hints:Species are most constant, since their generation is atrue continuation. [Species constantissimae sunt, cumearum generatio est vera continuatio. Systema naturae,1735]There are as many varieties as there are differentplants, produced from the seed of the same species.[Varietates tot sunt, quot differentes plantae ex ejusdemspeciei semine sunt productae. Philosophia Botanica 1751]
  17. 17. Maupertuis: the manwho invented evolutionCould we not explain in this manner [of fortuitouschanges] how the multiplication of the most dissimilarspecies could have sprung from just two individuals?They would owe their origin to some fortuitousproductions in which the elementary parts [ofheredity] deviated from the order maintained in theparents. Each degree of error would have created anew species, and as a result of repeated deviations theinfinite diversity of animals that we see today wouldhave come about. [Systèm de la Nature 2:164, 1743]Pierre-Louis Moreau de Maupertuis (1678-1759) was an interesting man. He devised what we now know as the principle of leastaction, and showed that the earth was flattened. Some other things he did, however, changed biology forever.In 1735, the first edition of Linnaeus Systema Naturae was published. Linneaus put out at least 13 editions of this in hislifetime, and the famous 10th edition was adopted in the 19th century as the "gold standard" - if Linnaeus named a species,that was its name thereafter, and if not, then the first person to name it after the 10th edition, published in 1758, got the credit.In the course of the work, and other books such as the Fundamenta Botanica, Linnaeus defined species asThere are as many species as the Infinite Being produced diverse forms in the beginning. [Species tot sunt diversae quotdiversas formas ab initio creavit infinitum Ens, Fundamenta botanica No. 157, 1736]He repeated similar statements in his work elsewhere. This, of course, is a definition of what we might call stasis rather than of"species". Linnaeus, following John Ray, held that species never changed from how they were created.Typically, we think this was overturned by Darwin, or, if we have read Darwins own "Historical Sketch", added to the thirdedition of the Origin, we might think that evolution was invented by Lamarck. But in fact the first view of evolution in a scientificcontext was devised by Maupertuis, in the context of the Generation Debates that preceded the rise of genetics. Maupertuisnoted that polydactyly, in the form of an extra finger on each hand, was passed on from generation to generation in a particularfamily in a 3:1 ratio, and each parent equally contributed. This, mark you, was 120 years before Mendel. In a text publishedfinally as Venus physique (the physical Venus) in 1743, he speculatedCould we not explain in this manner [of fortuitous changes] how the multiplication of the most dissimilar species could havesprung from just two individuals? They would owe their origin to some fortuitous productions in which the elementary parts [ofheredity] deviated from the order maintained in the parents. Each degree of error would have created a new species, and as aresult of repeated deviations the infinite diversity of animals that we see today would have come about. [Systèm de la Nature2:164, quoted in Terrell 2002:338]We should not make too much of this - Maupertuis was not really aware of the need for a population of individuals with geneticvariance, but it is clear that he allowed there to be two processes - variation in heritable traits that arose by lucky chance, whichwe would call an advantageous mutation, and diversification of species from common ancestors. Unlike Lamarck, who thoughteach species arose individually from nonliving matter, and subsequently changed in ways that were more or less predetermined,Maupertuis has species arising by the inheritance of mutations, and diversifying, in a manner very similar to Darwin. He lacks atheory of selection, but in some ways Maupertuis should be called the Last Common Ancestor of all evolutionists.One point that is important to note here is that almost as soon as species fixity became the widespread opinion (with Linnaeus -although Ray had put it out there earlier, it wasnt until Linnaeus became popular, mostly among botanists at first, that speciesfixity became the standard view, contrary to many popular histories of biology), evolutionism was offered as an alternative.Theres a good reason for this. Prior to Ray, nobody thought much about whether species were fixed or not. Aristotle held theycould be formed by crossbreeding, and that there were deviations from the "proper" mode of a species. Right through themiddle ages and early renaissance, there was a continuing view that species were wobbly sorts of things, and in the 18thcentury it became a fashion to gather species deviants - monsters and curiosities, as they were called - in cabinets to show tofriends. It is simply false that species were always held to be fixed. But evolution, in the sense of a historical series of changes
  18. 18. Buffon – non-hybridisinganimals (mules)We should regard two animals as belong to the samespecies if, by means of copulation, they can perpetuatethemselves and the likeness of the species; and we shouldregard them as belonging to different species if they are incapable ofproducing progeny by the same means.Thus the fox will be known to be adifferent species from the dog if it proves to be a fact that from the matingof a male and female of these two kinds of animals no offspring is born;and even if there should result a hybrid offspring, a sort of mule, this wouldsuffice to prove that fox and dog are not of the same species – inasmuchas this mule would be sterile (ne produirait rien). For we have assumedthat, in order that a species might be constituted, there wasnecessary a continuous, perpetual and unvaryingreproduction (une production continue, perpétuelle, invariable) – similar, ina word, to that of other animals. [Histoire naturelleVol. 2 (1749), 10]
  19. 19. John Hunter 1787The true distinction between different speciesof animals must ultimately, as appears to me, begathered from their incapacity of propagatingwith each other an offspring capable again ofcontinuing itself by frequent propagations: thusthe Horse and Ass beget a Mule capable ofcopulation, but incapable of begetting orproducing offspring.
  20. 20. Jussieu... species, [a term] wrongly used in the past, nowmore correctly defined as the perennial successionof like individuals, successively reborn bycontinued generation. [Genera plantarum secundumordines naturalis disposita (1789)...in one species are to be assembled all vegetativebeings or individuals that are alike in the highestdegree in all their parts, and that are always similar[“conformia”] over a continued series of generations...
  21. 21. Lamarck – fixed essenceSpecies: in botany as in zoology, a species is necessarilyconstituted of the aggregation of similar individuals whichperpetuate themselves, the same, by reproduction. I understandsimilarity in the essential qualities of the species, because theindividuals which constitute it offer frequently accidentaldifferences which give rise to varieties and sometimes sexualdifferences, which belong however to the same species, as themale and female hemp, in which all the individuals constitutethe cultivated hemp.Thus, without the constant reproductionof similar individuals, there could not exist a true species.[Encyclopedie Methodique,Vol. 2, 1786]
  22. 22. Lamarck – no such thing asspeciesIt is not a futile purpose to decide definitely what we mean by the so-called speciesamong living bodies, and to enquire if it is true that species are of absolutely constancy, asold as nature, and have all existed from the beginning just as we see them to-day; or if as aresult of changes in their environment, albeit extremely slow, they have not in the courseof time changed their characters and shape.…Let us first see what is meant by the name of species.Any collection of like individuals which were produced by others similarto themselves is called a species.This definition is exact: for every individual possessing life always resembles very closelythose from which it sprang; but to this definition is added the allegation that theindividuals composing a species never vary in their specific characters, and consequentlythat species have an absolute constancy in nature.It is just this allegation that I propose to attack, since clear proofs drawn fromobservation show that it is ill-founded.[Zoological philosophy 1809]
  23. 23. Lamarck – ... justparents and childrenThus, among living bodies, nature, as I have already said,definitely contains nothing but individuals which succeed oneanother by reproduction and spring from one another; but thespecies among them have only a relative constancy and are onlyinvariable temporarily. ...Nevertheless, to facilitate the study and knowledge of so manydifferent bodies it is useful to give the name species to anycollection of like individuals perpetuated by reproductionwithout change, so long as their environment does not alterenough to cause variations in their habits, character and shape.[Zoological philosophy 1809]
  24. 24. HeredityLewes 1856 review onlinehttp://scienceblogs.com/evolvingthoughts/2007/06/lewes_on_heredity_in_1856.phpShift from Generation to HeredityShift from similarity to fertilityHybridism from Interspecies to Within-SpeciesShift from Terata toVariance
  25. 25. ConclusionsThe Generative Conception ruled fromAristotle to Just Before DarwinAristotle was almost always not the source forthe use of the term after about 1700“Biological” (Reproductive Isolation)Conceptions occur from 1740 or so, dealingwith the existence of mulesPre-Darwinians were good observers

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