Evolution and man's place in nature

Preface

Ln this volume, I have undertaken discussion of the problem concerning Man’s Place in Nature. The discussion proceeds from the standpoint of Evolution of Organic Life, as maintained by Mr. Darwin, and by Mr. Alfred Russel Wallace. The main objects are to trace the evidence of man’s relation to the continuity of life on the earth, and to describe ■ the distinctive characteristics of human life itself.

Not without misgivings and apprehensions, have I undertaken this difficult task. Not without diffi¬ dence, do I now submit the outcome to criticism. I fully recognise the demand which science makes on the teachers of philosophy, and I here humbly offer a contribution towards its satisfaction. What¬ ever of failure may appear in this attempt, I may have succeeded in so far opening the way through the entanglements encompassing our higher biological problems. I am not without hope that these pages may carry help to many who have found it difficult to reconcile with acceptance of evolution, their

VI

PREFACE cherished convictions as to the responsibilities of rational life.

Since the publication of my work on The Relations of Mind and Brain, I have been closely occupied with the problem here discussed. During these years, I have been laid under deep obligation to many friends, whose valuable aid these prefatory lines enable me cordially to acknowledge. I have been specially indebted to my colleagues, Sir William Turner, Professor of Anatomy ; Professor Rutherford, Professor of Physiology; and Professor James Geikie, Professor of Geology. I owe grateful acknowledgment to Mr. George Brook, Lecturer on Embryology in the University, for important suggestions bearing on his department of research. Throughout my investigations, I have been constantly indebted to my son, Mr. William Leadbetter Calderwood, Director of the Marine Biological Laboratory, Plymouth. In connection with revisal of proofs, I have been under many obligations to Mr. Charles M. Douglas, my Class Assistant in the University.

My original plan included a series of illustrations in Comparative Embryology. I accordingly applied to Mr. Murray, Publisher, for use of the two illustrations on p. 10 in Darwin’s Descent of Man. In the kindest manner, and with the approval of Professor F.

PREFACE

Vll

Darwin, these illustrations were placed in my hands, a generosity which I greatly valued. Ultimately, however, it proved impossible for me to carry out my purpose in complete form, and T was led to prefer reference to authorities generally accessible. I desire im this way to indicate my sense of obligation to Mr. Murray, for the readiness with which he responded to my request.

H. CALDERWOOD.

Mh January 1893.

Chapter I Page

The Theory of Evolution has given occasion for a more searching discussion of the problem concerning Man’s Place in Nature. — Nature must be taken as a whole. — Man is the most conspicuous figure in an organised system of things. — 1 Nature ’ designates this system. — Man’s place can be ascertained only under full acknowledgment of the laws of evolution. — The presence of life on the earth is presupposed as an unexplained occurrence — Evolution cannot be a complete Natural History. —Evolution is the unfolding of life under the ‘ action ’ of Environment. —

The interaction of life and environment has led to results endless and varied. — These have generally, though not uni¬ formly, been progressive. — Human history must be traced within the world-history. — Darwin’s accumulated results apply much more to animal life than to human. — Limits of food

•

supply. — Adaptation of organism to its conditions. — Conflict, the inevitable condition of progress. — Large sacrifice of life, a uniform consequence. — Evolution illustrates laws of organic growth, persistence of sjoecies, and modifications of species. — Artificial selection, under domestication, illustrates the laws of Nature. — The accepted inductions of modern science call for extended interpretation of Nature. — An enlarged view of Cosmic Causes is a pressing want. — The laws of Heredity. — The problems of Embryology. —Man’s place, the most intricate of problems. — Its solution must largely aft'ect our theory of Nature. — In developing his theory, Darwin could not have done otherwise than give the chief place to animal life. —

Disadvantages of this, when proceeding to the problem of Man’s

ix

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PAGE

Place in Nature. — Difference of standpoint occupied by scientific men, and by those devoted to study of Mind. —

Two modes of Knowing. — Impossibility of the one mode of research passing into the field of the other. — What we are now seeking is the true conception of the Cosmic System, . 1-25

Chapter II

Need for clearing a pathway through Comparative Biology. — Relations of vegetable and animal life.— The physical basis of life. — No mechanical or chemical explanation of life available.

— Testimony of Niigeli, Huxley, Bois-Reymond. — History of investigations as to protoplasm. — Professor Sir W. Turner’s sketch of it. — Structure of the cell. — How its life is propagated.

— The germ-cell, or egg, from which organic life springs. — Dis¬ tinctions of sex, and introduction of two hereditary principles in the origin of higher forms. — Organic apparatus, muscles, nerves, and nerve-centres. — Structure accounts for activity. —

The relations of species. — Extending differentiation. — Man’s place among the varied forms of life, . 26-37

Chapter III

Need for preliminary statement in order to prepare for more ex¬ tended inquiry. — The art of speaking illustrates man’s superiority. — The comparative method required, in order to set human life in contrast with lower forms. — Facts of consciousness are distinct from organic functions. — Superiority of human organism. — Resemblance of Anthropoid Apes to Man. — Primeval man and his place in Nature. — Stone implements, and their testimony. — Contrast between mechanism and mind. — Testimony of Embryology. — Testimony of Physiology.— Development of human organism from the egg. — Dawn of consciousness. — Two orders of life combined in one, and two

XI modes of observation needful. — Organic apparatus thrown into a secondary place. Thought taking precedence in the regula¬ tion of life. — Organism and Intellect co-operate. — Consequent complexity of human functions. — Physique has not its equiva¬ lent in mind ; nor has mind its equivalent in physique. — Self-directed activity under guidance of intelligence. — Animal passion placed under rational law. — Human organism subject not only to physical law, but also to moral law. — Rational life unexplained by science. — Man’s place in Nature is determined by his rational life, .

Chapter IV

The difference appearing in life’s relation to environment, con¬ sequent on possession of rational power. — Inductions based on food-supply do not hold in this case, as they do in the case of animals.— Interaction of organism and environment, though not broken, is modified. — Human life maintains its position all over the world. — How man modifies environment. — All rational life is greater than its surroundings. — Nevertheless, Nature makes large demands on human effort. — As the secrets of Nature are discovered, human dominion is being extended. — In animal life, adaptation is by change of structure ; in human life, by fresh inductions, and harmonious regulation of conduct. — Nature itself has become a larger thing by the appearance of rational life, . .

Chapter V

Persistence of species. —Variation, consequent on adaptation. — Laws of inheritance provide for persistence of species, along with transmission of variation. — Heredity secures preservation of structural gain. — Its basis is the physiological unit, or the

PAGE

38-69

70-83

XI]

PAGE

germ cell.— Nothing more marvellous in Nature than develop¬ ment of the germ cell. — Relation of embryonic life to the parent life. — Darwin’s theory of Pangenesis. — Weismann’s theory of continuity of germ-plasm through successive generations. — Neither theory seems completely to account for the facts. — Darwin is strong in natural history ; Weismann in histology. — Mental life presents an entirely new problem in Heredity —

Can intellectual powers be traced to the germ-cell ? — Close resemblance between the embryos of animals and of man. —

Can we account for hereditary transmission of mental char¬ acteristics ? — Difficulty as to where, when, and how mental phenomena first appear in individual history. — How far the vital relation between child and parents involves ‘ mental inheritance.’ — Embryonic life in its relations with mental life. — Knowledge an acquisition in individual history. Hence, evidence for heredity in mind belongs mainly to the borderland, where relations bodily and mental come together. — Uncertainties still cling to the mode, and to the extent, of mental variation possible in this way. — That there is a double problem in human history must be admitted, and this admisssion must make further demands on research, . 84-121

CHAPTER YI

Sensory discrimination belongs to all life ; rational discrimination belongs to man only. — Sensibility depends on the nerve system. This varies in degree according to the complexity of the nerve system. — Movement is correlated with sensibility. — Sensibility and motor activity belong to the human organism, exactly as to lower types of organic life. — Need for a sharp distinction be¬ tween sensibility and rationality. — Man interprets experience, so as to obtain a knowledge of things. This is the distinction of a rational life. The senses thus become instruments in the service of a higher power. — Rational life classifies acquired knowledge, classifying objects according to distinct species. This involves also discrimination of the facts of consciousness,

Xlll

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and their classification. — Rational power is self-critical. — Re¬ sponsibility for our thoughts. — Experimental psychology deals with the mechanism of thought, explaining only organic processes which are the expression of thought, feeling, and purpose. It cannot explain the thought-process itself. All that is carried into the physiological laboratory belongs to the physics of thought and action. — Observing, interpreting, selfcorrecting, classifying, belong exclusively to Mind. — Knowledge is the interpretation of individual experience. — Our treatment of the problems of existence lies quite beyond the functions of the sensori-motor system, and the action of nerve centres. —

Each intelligent being is a freeman who takes possession of his own inheritance in the earth. — What he is, he is as a thinker, who must think for himself. —Testimony of thinkers of opposite schools, for a twofold life, physical and rational. — G. H. Lewes, Helmholtz, Herbert Spencer, Hallam. — All rational exercise involves consciousness, and responsibility for self-directed thought, and for self-regulated action. — Inadequacy of ‘mole¬ cular processes’ as an explanation of reflection. — The Mind cannot think without knowledge of itself, and of its own pro¬ cedure, . 122-144

Chapter VII

Facts as to animal intelligence should be taken at their highest value, in support of evolution. — Wallace’s summary of Darwin’s conclusions. — Knowledge of animal intelligence is in¬ direct. — Interpretation of sensory impression is the mark of intelligence. — The appearance of this power involves the theory of evolution in difficulty. — The higher mammalia possess intelli¬ gence. — How shall we account for its origin? — The dog, horse, monkey, and ape are included. — Generalised knowledge is un¬ attained by animal intelligence. — Two types of Mind, a lower and a higher. — Interpretation of sensory impression cannot be attributed to animals low in the scale of organism. Yet many of these have sensory apparatus quite in advance of the higher mammalia. — Darwin does not consistently restrict to the

XIV

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higher mammals. — The inquiry is thus involved in confusion.

— The argument from special’ sensibility must be withdrawn.

So must the argument from brain structure. — A more rigid separation of sensory experience from intelligent discrimination required. — Difference between physical function and mental action in human life. — Need for more exact use of terms. — The dog taken as test of animal intelligence.

A searching inquiry as to Instinct is needful. — Animal con¬ duct impossible to us by the use of our intelligence, cannot be referred to intelligent power. — A truer conception of Nature will be reached by more successful interpretation of Instinct.

— Illustrations of Instinct.— Food-supply. — Provision for the young. — Much of the testimony for evolution drawn from In¬ stinct must be abandoned. Such surrender is a clear gain to the theory. — Instinct stands apart from intelligent power. It is most remarkable in lower forms of life.

The ant, the dog, and man placed in contrast. — A further test is supplied by domestication. — Use of signs is the effective test. — Superiority of the dog to the ape, results from long training of the former. — Human agency and animal co-operation. — The lower the animal, the more difficult to direct its activity. — Our intervention for co¬ operation with animal activity. — In the work of insects, under¬ standing comes wholly from man. — In working with the dog, or horse, understanding comes from the animal also. — Training of animals, a test of intelligence. — Need for constant regard to their sensibilities in order to apply this test. — Interpretation of signs is the utmost point reached. There is no search for know¬ ledge, nor is there an independent intelligence guiding action.

— Difference between training and educating. — How far can ‘ideas’ be conveyed to animals? . 145-256

Chapter VIII

The aim is to trace the activities of the rational agent. — Wallace's treatment of mathematical, musical, and artistic faculties. — Aim here is to deal with actions common to men , and with the

XV

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manifestation of rational power in the progress of the race.

— Conception of a self-regulated life. — Government of bodily activity. — Rational power and physical, correlated. — The higher functions of human life belong to consciousness. — Rational interest in environment. — Work ruled by reason. — Modified action of environment inhuman history. — Severance of the two forms of action, physical and mental. — Activity of mind is not continuous with activity of nerves. — Consciousness of reflection, and of self-determination of conduct. — How Biology is placed in view of these facts. — Insufficiency of a theory of Evolution. —

The limits of discovery offer no defence against this conclusion. — Duality of life in man. — Our certainty as to the two sets of facts, the organic and the spiritual. — A view of the rational powers. — ‘ Man’s dignity’ appears in control of the animal nature. — Man’s degradation appears in neglect of this control.

— Difference between man and animal. — ‘ Degeneration ’ in man.

— Heredity as it bears on responsibility. — Characteristics of moral life. — Conscience bears witness for an ideal. — Judgment of our own conduct and of the conduct of others. — Recognition of the Supernatural. — Comparative Religion. — Christianity re¬ garded as a historical religion, influential in the life of the race.

— Agnosticism a negative, rather than a positive influence. — The limits of human knowledge. — Life’s close. — Witness for a Future State. — Sacredness of human life. — Christian thought as to the Future. — Results of the survey of the whole field of Com¬ parative Biology. — Significance of Evolution. — Distinctiveness of human life, . 257-342

Index,

343-352

Chapter I

For scientific thought, the most obvious need is an adequate representation of man’s place in nature. The general acceptance of Darwin’s theory of Evolu¬ tion gives force to the demand for discussion of this problem. Whatever differences of opinion as to this theory may still exist, few naturalists can feel reluct¬ ant to acquiesce in Wallace’s statement that Darwin ‘ did his work so well that “ descent with modification” is now universally accepted as the order of nature in the organic world.’1

Acknowledging this, there is need for fuller study of man’s place in nature. The distinctive features of human life must be depicted, and must thereafter be interpreted in relation to the wide range of natural history. This task can be successfully accomplished only by regarding Nature as a whole, — a unity con¬ stituted by the most intimate correlation of all its parts. If man’s place is to be thus studied, it must

1 Darwinism, by Alfred Russel Wallace, Pref. v.

A be with the patience of which Darwin set an impres¬ sive example in his observation of lower forms of life.

In treating of man’s position, we regard him as the most conspicuous figure in a thoroughly organised system. It is impossible to contemplate human life as a thing apart or isolated. We must study man as related to the general scheme of Nature. By ‘Nature’ I mean the whole system of things in the midst of which we pass our lives. ‘Nature ’is often placed in contrast to ‘ Man,’ — and so the term may at times be used here, — but in the structure of the main argument ‘Nature’ includes man and his efforts. In developing the argument, it will be re¬ quisite to include things familiar to all, along with the latest results of scientific research. Only thus can we have a solid basis for extended investigation as to man’s place.

Further, as indicating provisionally the attitude assumed, I hold that no reasonably successful ac¬ count of the universe can be presented, which does not accept the more general conclusions of Darwin, along with results of more recent research, which have at once sustained, and in some degree modified, his theoretic conclusions. Whatever limitations are to be assigned to the theory, we must at least grant that a law of Evolution has had continual application in the world’s history. How much is involved under this law may still afford matter for large debate ; nevertheless, it is generally agreed that a more ac¬ curate conception of the history of things has been obtained as the result of the researches in which Charles Darwin and Alfred Russel Wallace have led the way.

How the appearance of life is to be explained is matter of conjecture. So far as the investigations of natural historians suggestive must speak of the 'origin’ of life, not of its ‘ Evolution.’ Evolution supposes existence : Evolution, in the history of organism, pre¬ supposes organic life. There was a lower form from which a higher had been evolved. Biological progress results from the fact that life, in each of its forms, moves towards the perfection of its kind. In natural history, therefore, life is taken as existing, a reality already present, given at some earlier stage in the world’s history. Evolution cannot be a complete natural history ; at most it is a scientific account of later stages in the history of the universe. Darwin saw this, and stated his position quite clearly, claiming one or more primordial forms. Huxley puts the posi¬ tion strongly against spontaneous generation : ‘ The

fact is, that at the present moment there is not a shadow of trustworthy direct evidence that abiogenesis does take place, or has taken place, within the historic period during which existence on the globe is re¬ corded.’1 Nageli, a high authority as to vegetable life, holds that among known living beings there are none which could have arisen by abiogenesis.2 The presence of life supplies the scientific basis on which Darwin rests, when observation leads him to this de¬ claration : — ‘ I view all beings, not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited.’ 3

3 Origin of Species, pop. ed,, p. 402.

If only this implication be recognised, that the origin of life lies behind its evolution , we need not linger to conjecture how many primordial forms it may be necessary to admit, nor need we inquire as to the history of the appearance of these. Specu¬ lative questions may be left in abeyance for the present. They will assert themselves in good time, though they are held in reserve at this early stage. For commencement, we are restricted to the history of the existing. Afterwards, speculative thought may claim its rights.

Granting that Evolution supplies the key to a large part of the natural history of life on the earth, pro¬ gress has not been by a single grand movement, as when the tidal wave rises in the ocean, or as when the course of the river has been determined by the configuration of the valley. The law of Evolution has, indeed, had constant application, but it has not worked precisely the same results in all cases. En¬ vironment has presented varying conditions, and the consequence has been endless diversity in the history of life itself. The laws providing for evolution have, however, operated so constantly, that we should not seriously err, if we were to depict the history of life as a unity, representing a constant and world-wide pro¬ gress. Still, adaptation to environment has been fruitful of varieties. Though ‘ the struggle for existence ’ has not been by any means uniform, it has been sufficiently general to rank as a formative cause. Exact estimates of its efficiency will bring us to re¬ stricted areas of food-supply, or areas more or less crowded with competitors ; but the struggle does not disappear even when food is abundant, and demand comparatively small. As life has multiplied on tlieeartli, however, demand has increased, and struggle has become more serious. World-history runs through this widely extended conflict. Immense sacrifice of life is the consequence ; but in the midst of all, and by means of struggle occasioning death very widely, advance of life has been gained, so that it is reason¬ able to speak of ‘survival of the fittest’; and thereby improved species have appeared.

Human history must be traced within this world-history. Humanity is not exempt from the conditions of progress described. For the members of our race, as for the lower animals, it has proved true that variety of surroundings, more or less favourable, has presented variety of result, as in the history of different tribes and nations. What is required, therefore, for an adequate representation of Man’s place in Nature is a more searching scrutiny of his relation to the general laws of existence.

Wide and careful as was the research of Darwin, his accumulated results have much more bearing on animal life, and even on lower types of that, than on human life and character. Exact conclusions are unattainable as to the number of lines of biological advance, and the variations within these lines. That there has been general advance is beyond dis¬ pute ; but as the risks to life are many, there are possibilities of reverse by deterioration. It is accord¬ ingly needful to allow for manifold deviations. Mr. Herbert Spencer has properly emphasised this in saying that : ‘ Organisms may vary not only in re¬

spect of their structures, but in respect of their ten¬ dencies to do this or the other, in all kinds of ways,

— many or most of the ways at variance with welfare.’ 1

The general history of the evolution of life on the earth presents these two marked phases. First , Life finds in environment provision for its continuance and growth. Life thus shows dependence on an inferior order of existence. Second , Life, in unfolding, adapts itself to environment, thereby illustrating its superiority. Life is the key to progress ; conflict is an inevitable condition of life, and out of this conflict comes general advance. However attractive the result, there is something startling in the fact that sacrifice of life belongs to the conditions of progress. Whatever the moral difficulty here, — and it is par¬ ticularly great as illustrated in the bitter experience of men encountering the evils of ‘ over-competition,’ — there can be no doubt that a law of sacrifice is in¬ cluded among the conditions of progress. Within the history of the world’s advance, there lies con¬ tinually a history of enfeeblement and death. Evil attends on the good. However great the gain in the world’s history, suffering and sacrifice still continue. Biology is fruitful of ethical perplexities. Yet, through all this mixture of good and evil, there is provision for general advance, in the persistence of life. The inherent tendency to progress, belonging to life in every form, is the mainstay for thought in seeking interpretation of Nature. The conditions of the material world, of organic life, and of moral life combined, provide for the history of an orderly universe, the growing understanding of which brings

1 Letter to Dr. Martineau, in Appendix to his Types of Ethical Theory , 3d ed. vol. ii. p. 570.

ever-increasing reward to scientific research. For organic life, c warmth, air, light, moisture, food,’ are ‘ the mightiest impulses which determine the manifold variety of the forms of living beings.’ 1 When from organic form we pass to the ethical character in man, thought proves a grander agency by which a nobler life unfolds in the world. Through all this, the law of heredity provides at once for transmission of variations, and for further advance. Nature, taken in its highest aspects, appears as a living unity, with a history ever unfolding in fresh acquisitions. Scientific controversies, however wide in import, have at least a common basis in unchangeable laws of progress, ever deepening their impress on the face of Nature. Darwin and Wallace, Weismann and Eimer are severed on points of large significance ; but they are agreed as to the main laws of acquisition, and of in¬ heritance securing the world’s advance.

The great lines of evidence for Evolution of organism are broadly marked. The laws of growth for in¬ dividual life come first in importance ; persistence of species bears its testimony for inheritance ; modifica¬ tions of species tell of the moulding power of environ¬ ment ; the records of artificial selection, under the advantages of domestication, throw a broader light over the provisions of Nature, whether the records tell of enduring, or of temporary, deviations from the normal type. When human intelligence comes on the field, selecting and regulating results in animal life, we see still more vividly that progress is the law of Nature.

1 Organic Evolution as the Result of the Inheritance of Acquired Char¬ acters , by Dr. G. Eimer, translated by J. T. Cunningham, p. 22.

Natural History, extended by records of domestica¬ tion, opens the gateway into a large field of inquiry, where, since man belongs to Nature, the ‘artificial’ is only an additional phase of the natural. Variation artificially induced presents the results of superadded observation and direction by rational life; and this has been so widely extended, as to be essential to the system of things interpreted by science. Human Reason and Will have proved large factors in the earth’s history. Through long ages, the highest life has been a directing power in the world, determining the history of subordinate forms. Natural and arti¬ ficial selection have been combined in preparation of the system of organised existence with which we are familiar. The world now is an inheritance from all that the world has contained. This implies ‘ natural selection ’ in its larger sense. The ‘ art ’ employed by man, itself belongs to Nature. This enables him by selection of conditions to facilitate, and even to intensify, the action of ‘ Nature.’ ‘Arti¬ ficial selection ’ is not extra naturam. The dis¬ tinction between natural and artificial is of obvious value to us, but there is no cleavage in Nature itself.1

Our accepted inductions need to be harmonised by extended interpretation of Nature. The history of the theory of Evolution carries this lesson written broadly over many of its pages. While strict observa¬ tion has done vast service, analogy has been allowed more than its legitimate share of influence ; not unfrequently the particular has been unduly over-

1 Not without reason does Spinoza protest against the tendency to treat of man as if his life were imperium in imperio. Ethics 1. Appendix.

shadowed by the general. Not easdy is a full sight of cosmic causes obtained. Deliverance from danger of hasty induction must be worked out by persistent re¬ search, and unshrinking criticism. Division of labour among naturalists, will provide for attention to every order of life in our further study of the scheme of existence. Advance in science deepens our con¬ viction of the marvellous intricacy of Nature’s methods. Slowly we shall come to learn how tem¬ porary uses are served, while some advance is beingmade towards a general end. ‘ As individuals grow, so the whole world of organic forms has grown up from simple beginnings;’1 and even so, a complex system of law is now working for much grander results in ages to come.

If we are truly to know, and, thereafter accurately to interpret according to knowledge, we must be contented with a slow elaboration of results. While analogies supplied by individual growth are valuable, the complex conditions affecting life over the wide world carry us far beyond analogical inference. The conception which a theory of Evolution has made possible, needs to be sustained by deeper research as to the cosmic causes, and to be guarded specially against the fallacy which would find in the less the cause of the greater. Too readily do we speak of the lower producing the higher, tending to overlook the primary truth, that only the mature life produces the germ, organic life thus testifying by law of heredity that the greater produces the less. However sur¬ prising it be that a microscopic germ contains within it the promise of the normal characteristics of the

1 Organic Evolution, Eimer.

species, the efficiency of the mature life cannot be overlooked. The law of inheritance has these two sides of application ; transmission is the condition of inheritance. While, then, imagination gathers aid from the unfolding germ, it must figure things in harmony with the grand truth, that potentiality within the germ depends for its action upon poten¬ tiality operating beyond itself.