Classification and Biology

R.A. Crowson

• Editorial: Routledge
• Año: 2017
• ISBN:
  9781351528061
• Edición: 1
• Categoría: Sciences biologiques
• Categoría: Biologie

Classification of plants and animals is of basic interest to biologists in all fields because correct formulation and generalization are based on sound taxonomy. This book by a world authority relates traditional taxonomic studies to developments in biochemical and other fields. It provides guidelines for the integration of modern and traditional methods and explains the underlying principles and philosophy of systematics. The problems of zoological, botanical, and paleontological classifi cation are dealt with in great detail and microbial systematics briefly.

1
The Classification of the Sciences

For our purposes, science may be defined as the rational and objective study of the external universe by human beings. Whether the study of man himself is included as part of science will depend on how we interpret ‘human beings’ in this definition. If we regard humanity as in essence an assemblage of isolated individuals, then any one of them may regard the rest as part of the external universe and thus as ‘material’ for scientific study; on the other hand, if, as seems preferable to me, humanity is regarded as essentially one body and science as a collective rather than an individual function, we can hardly avoid maintaining in some form or other the traditional distinction between the sciences and the humanities. The problems of classifying human beings will not be considered in detail in this book, though it will appear that if the criteria developed for other animals were applied to our own case, the Chimpanzee, the Gorilla and perhaps the Orang-utan would join us in the genus Homo.

Classifying things is perhaps the most fundamental and characteristic activity of the human mind, and underlies all forms of science. The capacity of our brains to function as computers seems to have been a rather late discovery in human cultural history, there being no evidence that anything which could be called mathematics was developed before late Neolithic stages, up to perhaps 7,000 years ago—though doubtless simple counting of flocks and persons came considerably earlier. Even now, the human mind solves mathematical problems in quite a different manner from that adopted in mechanical computers. Confronted with the symbols ‘9 x 8’ the reader will doubtless recognise a portion of the multiplication table and instantly produce the answer ‘72’, whereas the procedure of a mechanical (or electronic) computer would amount to adding together, at very high speed, 9 groups of 8. In the same way, a more advanced mathematician, confronted with a complex differential equation, will seek some way in which it can be transformed, according to established rules, into a form for which there is a recognised technique of integration—to put it in another way, he will seek to ‘recognise’ it as a more or less disguised member of a classificatory group. The solution of any type of equation by an electronic computer is normally by ‘trying out’ a vast number of different values for the unknown (s) until it hits ones which give the right result—the human analogue would be to plot a graph of the function and find the roots thence. The human mind solves mathematical problems essentially by feats of classification.

Reasons for the primacy of classification as a function of the human mind are not difficult to imagine. Our ancestors were social as soon as (or before) they became human; they probably lived in more or less numerous and ordered groups and utilised a great variety of food materials. Effective group organisation would depend on the ability to recognise, and react appropriately to, a large number of other individuals and on the system of communication by means of language. The essential elements in language are nouns and verbs—the use of which involves the classification of things and of actions or events. Widely polyphagous feeding habits would be safe only for organisms which could learn to distinguish many kinds of eatable and uneatable things.

There have been many authorities who have asserted that the basis of science lies in counting or measuring, i.e. in the use of mathematics. Neither counting nor measuring can however be the most fundamental processes in our study of the material universe—before you can do either to any purpose you must first select what you propose to count or measure, which presupposes a classification. And no amount of mathematical treatment of your results can confer on them any greater reliability than there was in the classification by which you selected the things to count or measure. As we shall see, there have been recent attempts to bring numbers and mathematics into the actual process of classifying organisms, usually by way of counting the number of characters in common or differing between them. However, even if it were possible, as it would need to be if ‘numerical taxonomy’ were ever to become a scientifically rigorous process, to formulate an objective definition of a ‘unit character’, such a definition could only be formulated in terms of comparisons between suitable similar organisms—no conclusions about unit characters could be derived from the comparison of a cat with a mushroom. The ‘unit characters’ which are the basis of material taxonomy must be abstracted from a prior non-mathematical classification. Mathematics would thus appear as a possible method of refining an existing classification, not of constructing one de novo.

The sciences themselves may be classified in various ways. In an interesting article the Harvard philosopher, Tejera [188] wrote:

Classifications of the sciences in our time appear, on the whole, to be a matter of parcelling out different areas which it is assumed are to be investigated in the same way. We seem to have lost the sense that different sciences might not be the same in the amount of system or degree of explicitness of which they are capable, or that they might in fact differ in kind from other sciences. This is due to the speculative bias of Western civilization which, since Aristotle, has preferred and developed the sciences which he called theoretical and which today are called deductive.

This I think is largely true, but even today a genera], if confused, awareness of differences is manifest in such current phrases as ‘the physical sciences’, ‘the biological sciences’, ‘exact sciences’, ‘observational sciences’, ‘experimental sciences’, etc. Underlying all these there is, I think, a real and deep distinction, which commonly escapes recognition in its true form today. The most fundamental division among scientists is, I believe, that into natural historians and natural philosophers [37].

A scientist who seeks to explain the actual universe, or any (non-human) part of it, in detail as it is, in terms of its concrete history, can properly be called a natural historian—he is literally concerned with the history of nature. The natural philosopher on the other hand is devoted to the search for fundamental laws of the highest possible generality— laws which he hopes will apply throughout space and time. For the natural historian, the laws of natural philosophy are not ends in themselves, but tools for the understanding of the actual universe. The scientific work of the natural philosopher has its beginning and its end in the laboratory; the classic pattern is for some initial experimental result to suggest a hypothesis, which is elaborated in the study, and results in predictions which are finally verified (or falsified) in further laboratory experiments. A hypothesis in natural history on the other hand is (or ought to be) based in the first instance on some observed facts in nature, and though laboratory experiments may play an important part in its intermediate development, its final testing ground is again in nature itself.

The characteristic mode of thought of the natural philosopher is deductive reasoning from given postulates; if the results of the reasoning process prove not to be in accord with experimental evidence, he will consider that he has disproved one of the postulates. The mode of thought typical of the natural historian on the other hand is much more akin to that of Sherlock Holmes than to those of Newton, Einstein, Bohr or Rutherford. The individual steps in his arguments can rarely claim the infallibility of mathematical deduction, and he is as a rule suspicious of long chains of reasoning. Dealing in probabilities rather than certainties, his main intellectual skill lies in perceiving how a number of only moderately strong individual probabilities can be combined to produce an overall near certainty.

The distinction between these aspects of science is essentially one of human predilections—if you are predisposed to believe in uniformity, you will seek to explain away apparent differences in terms of underlying similarities, and if you become a scientist you will find your natural place as some kind of natural philosopher; if, on the other hand, you delight in the differentness and uniqueness of things, you might become as artist of some sort, or a natural historian.

The remark of Professor Oakeshott [146b] that ‘the Rationalist is always in the unfortunate position of not being able to touch anything, without transforming it into an abstraction; he can never get a square meal of experience’ is, in the scientific world, particularly applicable to the natural philosopher.

Tejera’s criticism of the one-sided natural-philosophical outlook occurs, significantly, in an article on ‘The Nature of Aesthetics’. The natural philosophers as a class show the speculative and deductive bias mentioned by Tejera, they are addicted to those philosophies which preach fundamental unity and which exalt the observing mind as against the natural universe; Platonism, Idealism, Monism, Positivism, and even Spiritualism, have all numbered their adherents among the physicists. Philosophising of this sort is comparatively rare among natural historians, whose private inclinations are more likely to be towards Aristotelean dualism, old-fashioned materialism, or Words-worthian pantheism.

The division of science into natural history and natural philosophy is not, of course, new; the very terms in which it is expressed derive from Bacon’s ‘De dignitate et augmentis scientiarum’ [7]. Bacon’s Ustoria naturalis corresponds almost exactly to natural history as we have defined it; for him it represented that part of science in which the faculty of memory (memoria) was dominant, whereas he considered reason (ratio) to be the dominant faculty within the sphere of philosophia naturalis. Bacon recognised that the distinction was one of predominance only, the part played by reason in natural history, like that of memory in natural philosophy, he recognised as vital even though it was subordinate. The third of Bacon’s fundamental human faculties, poesis or imagination, was also recognised by him as playing an essential part in both Ustoria naturalis and philosophia naturalis, though its sphere of dominance (creative art) lay outside the bounds of science altogether.

Bacon’s attribution of a dominant role to memoria in the domain of historia naturalis was no doubt just. The natural historian, like Sherlock Holmes, needs to have a memory richly stored with diverse and little-known information. Progress in natural history almost invariably results from the perception or intuition of a hitherto unsuspected connection between two pieces of information, no doubt the same basic process as Koestler’s ‘bisociation’ [118]; this is only likely to happen when both pieces of information are stored up in one and the same mind. Thus modern trends in education, which increasingly emphasise ‘principles’ rather than facts, are detrimental to natural history; this is one more manifestation of the excessive predominance of natural philosophy in current scientific attitudes.

Herbert Spencer, in his pamphlet The Classification of the Sciences [176], makes the same distinction very explicitly, with a threefold division of science into Abstract Science (= Mathematics), Abstract-Concrete Science (=philosophia naturalis) and Concrete Science (=historia naturalis). Spencer, who had psychological theories of his own, did not follow Bacon’s correlation of different kinds of science with different human faculties. He was at pains to make it clear that his division of the sciences was in conflict with the teachings of August Comte, whose doctrine of a natural, logical and historical sequence of the sciences in the order Mathematics—Astronomy—Physics—Chemistry—Physiology—Botany—Zoology has had a very wide influence lasting up to the present time. Comte’s seriation of the sciences, it will be noted, significantly ignores Geology.

More recently than Spencer and Comte, the German philosopher Wilhelm Windelband, in his ‘Geschichte und Naturwissenschaft’ [208], distinguished between what he called Nomothetic and Idiographic sciences. A nomothetic science was, for Windelband, one whose ultimate aim was the formulation of laws of the utmost possible generality, and in the thinking of whose practitioners the tendency to abstraction (i.e. Bacon’s faculty of ratio) predominated; idiographic sciences on the other hand aim at the fullest possible understanding of actual things and events, and their practitioners make much use of a faculty which Windelband called ‘Anschaulichkeit’ (usually translated as intuition). Idiographic science obviously corresponds to historia naturalis, though Anschaulichkeit can hardly be equated with memoria; in Baconian terms it might represent a synthesis ofpoesis and memoria.

A more recent author who has used the phrase ‘natural history’ in a rather similar sense is Teilhard de Chardin [186b], who wrote: ‘s’il fallait trouver un nom général à la Science speculative, telle qu’elle tend à se constituer par l’alliance des disciplines les plus abstruses et les plus raffinés de notre siècle, il conviendrait sans doute de l’apeller l’Histoire Naturelle du Monde’.

A similar distinction was made by Bergson, who distinguished philosophically between ‘laws’ and ‘genera’. He pointed out that ancient science was more concerned with genera than with laws, leading to a confusion of the physical with the vital. He goes on to point out that ‘There is the same confusion in the moderns, with this difference, that the relation between the two terms is inverted: laws are no longer reduced to genera, but genera to laws; and science, still supposed to be uniquely one, becomes altogether relative, instead of being, as the ancients wished, altogether at one with the absolute. A noteworthy fact is the eclipse of the problem of genera in modern philosophy. Our theory of knowledge turns almost entirely on the question of laws: genera are left to make shift with laws as best they can. The reason is, that modern philosophy has its point of departure in the great astronomical and physical discoveries of modern times. The laws of Kepler and of Galileo have remained for it the ideal and unique type of all knowledge.’ If natural philosophy is the science of laws, natural history might be defined as the science of genera.

Natural philosophy, as we have defined it, will include physics and chemistry only. The twentieth century ‘take-over’ of chemistry by physics is popularly believed to have been final and total, but in this as in many other respects popular opinion has been misled by propaganda. It is, in fact, very far from being the case that all phenomena studied by chemists are quantitatively predictable in terms of the fundamental laws of physics; for example, no physicist could calculate, from fundamental physical laws alone, whether, when two given solutions of metallic salts are mixed together in a test-tube, a precipitate will form or not. There is as yet no rigorous theory of the liquid state, nor of solubility. A chemist might be able to make reasonably accurate forecasts of the solubilities of hitherto unprepared compounds, but this would be on a basis of empirical chemical generalisations, not laws of physics. In its continued reliance on empirical generalisations, chemistry shows some similarity to natural history, but the fact that the elements and compounds with which it deals either exist or could in principle be prepared anywhere and at any time in the universe, takes it out of the domain of history and places it in the same category as physics.

The fact that in one branch of astronomy—Celestial Mechanics— predictions of a high degree of accuracy can be made on the basis of physical laws has had the result that in the common mind astronomy is often separated from the rest of natural history and considered as an ‘exact science’ akin to physics. Yet the fact that the earth has its moon whereas the similar-sized planet Venus has none is no more to be deduced from the laws of physics than is the difference between a primrose (Primula vulgaris) and a cowslip (Primula veris). Generalisations about Cepheid variable stars have the same logical status as ones concerning Rodentia, reversed faults, cold fronts, or Compositae, and quite a different one from laws of physics.

The major divisions of natural history, as here defined, are Astronomy, Geology, Meteorology, Virology, Bacteriology, Botany and Zoology. Sociology and Psychology are excluded as being concerned with Humanity rather than Nature; they are more closely bound up with History, Politics and Art than with the natural sciences. Our divisions are, of course, concerned only with pure science; technology and applied science (Engineering, Electronics, Agriculture, Medicine, etc.) stand outside the scheme; their methods may be those of science, but their aims belong in the sphere of Humanity. It is currently fashionable to associate together, under the name Biology or biological Sciences’, Virology, Bacteriology, Botany and Zoology, on the grounds that certain phenomena—particularly the basic structure and mode of replication of nucleic acid molecules—are common to all of them. Though this is no doubt true, it is also true that the numbers, diversity and organisational complexity of plants and animals are sufficient to make both Botany and Zoology fully worthy to rank as independent sciences, and they will be so treated in this book.

The laws of natural philosophy claim to be both universal and exhaustive—anything that happens in the universe is supposed to be in principle explicable in terms of them. If this is so, it may be asked, what need is there for natural history at all? Should not the physicists be capable of explaining and predicting all natural phenomena? The best test case for these questions is perhaps to be found in meteorology. All the basic phenomena of weather—heat conduction and convection, evaporation and condensation of water, absorption of radiation, electrostatic charge and discharge, winds, etc.—are strictly controlled by known physical laws. Mankind has a great interest in the reliable forecasting of the weather—-why do we not see meteorological prediction taken over by a group of physicists and converted into an ‘exact science’? The recently publicised attempts to apply electronic computers to weather forecasting do not, it must be made clear, involve the taking over of meteorology by physics—the programming of such computers is based on empirical laws of weather forecasting, not on laws of physics.

It is, I believe, the intrinsic limitations of the human mind which render us incapable of making an exact science of meteorology. That such limitations exist is only grudgingly, if at all, admitted by the leading scientists of our day. The most eminent zoologists believe that the brain of man originated merely as an improvement on that of other anthropoids, and that it reached its present structure in serving the simple needs of a Stone Age society; it seems very strange to me that, accepting such postulates, they are so unwilling to admit any limitations of the power of this organ in themselves. In physics, these limitations are most clearly revealed in our inability in general to solve, and often even to formulate, mathematical equations describing the behaviour of systems of three or more mutually influencing components. Given all the parameters of such a system at a given instant, and the precise rules governing the interaction of its components, neither physicists nor any other human beings could in general calculate the precise condition of the system at a specific future instant. The classical manifestation of this is in astronomy, where the behaviour of systems of three or more massive bodies, each moving under the combined gravitational influence of the others, can be predicted only by methods of successive approximation which are laborious and never produce an exact result. If some problems of this type can be tackled by means of analogue computers, this does not really affect the argument. In meteorology, the variables involved in weather are mostly mutually-influencing, and certainly more than three.

The following two paragraphs, quoted from an article by Professor Hayek [87], make the same point very explicitly:

It is, indeed, surprising how simple, in these terms—i.e. in terms of the number of distinct variables—appear all the laws of physics, and particularly of mechanics, when we look through a collection of formulae expressing them. On the other hand, even such relatively simple constituents of biological phenomena as feed back or cybernetic systems, in which a certain combination of physical structures produces an overall structure possessing characteristic properties, requires for its description something much more elaborate than anything describing the general laws of mechanics.

Probably the best illustration of a theory of complex phenomena, of great value though i...

Índice

• Cover
• Halftitle Page
• Title Page
• Copyright Page
• Preface
• Contents
• 1. The Classification of the Sciences
• 2. The Function of Classification in Natural History
• 3. The Species in Biological Systematics
• 4. Classification Below the Species Level
• 5. Classification Above the Species Level
• 6. The Classification of Fossils
• 7. On Classificatory Characters, and Their Correlation
• 8. The Classificatory Use of Non-Structural Characters
• 9. Phylogeny as the Basis of Classification
• 10. Hosts, Parasites and Classification
• 11. Geographical Distribution and Classification
• 12. Heredity and Chromosomes in Relation to Evolution and Classification
• 13. Phylogenetic Evidence from Nucleic Acids and Proteins
• 14. The Systematic Value of Characters of Immature Stages
• 15. Numerical Taxonomy
• 16. The Non-Congruence Principle
• 17. Some Special Classificatory Problems
• 18. Taxonomic Research
• 19. The Practical Problems of Phylogenetic Classification
• 20. Zoological and Botanical Nomenclature
• 21. The Practical Work of the Present Day Systematist
• 22. Epilogue: The Future of Systematics
• Bibliography
• Index