The direction of human evolution

Preface To New Edition

During the past few years, and especially within the past twelvemonth, there has been a remarkable recrudescence of the old theological opposition to the theory of evolution, especially as applied to man. In spite of the great amount of evidence which has been accumulating during the past half century with regard to the evolution of man, it is probable that nothing more ignorant, frenzied, or intolerant has ever been uttered against this theory than has appeared during the past year.

No scientific investigator of ten years ago would have thought it possible that the truth or falsity of any scientific theory would ever again be decided by appeals to the Bible, or that an attempt would ever again be made to determine by legislation what might be considered orthodox or heterodox science; and yet this has come to pass. An organization has been perfected among certain religious denominations for the purpose among other things of banishing modernism and particularly the theory of evolution from churches and schools. Its plan of campaign has been outlined in part as follows:

"In order to purify the institutions where modvi PREFACE TO NEW EDITION

ernism is taught we must discipline and reform these institutions. . . . Our universities, reeking with the unbeHef of an evolutionistic false philosophy, are the most dangerous centres in America. . . . Our government has undertaken to regulate business, but the hour has come to regulate our education. . . . The use of the evolutionary hypothesis must be abandoned. . . . The new theology and modernism must be separated from our institutions of learning. . . . This splendid organization could in all probability succeed in cutting off most of the financial support from these institutions, if not in actually bringing about their total destruction." *

Acting upon this last suggestion, bills have been introduced in certain State Legislatures forbidding the teaching of evolution or Darwinism, as applied to man, and in one instance such a bill came within one vote of being passed. Text-books that teach evolution, even as an incidental part of biology or geology, have been condemned and placed on the index prohibitus of this new Inquisition, and it is said that funds are being raised to endow and make perpetual this fight against evolution.

All this is done, we are told, to save the religious faith of the younger generation. Apparently the leaders in this movement do not realize that they, and not the evolutionists, are making it impossible

* From The Christian Century, April 28, 192 1.

PREFACE TO NEW EDITION vii

for young men and women who are intellectually enlightened to remain in their denominations. It is a dangerous thing for defenders of the faith to affirm, as these do repeatedly, that one cannot be a Christian and an evolutionist at the same time, for students of nature who find themselves compelled by the evidences to accept the truth of evolution will be apt to conclude that they must therefore count themselves as opponents of the churches. The worst form of infidelity is not disbelief in doctrines, whether theological or scientific, but disbelief in the ultimate triumph of truth. If evolution is false, it cannot be saved by science; if it is true, it cannot be destroyed by theology.

In general, the opponents of evolution have neither the technical ability nor even the desire to weigh critically the evidences for the truth of evolution. Properly to appreciate these evidences requires some first-hand knowledge of morphology, physiology, embryology, ecology, paleontology, and genetics. In science it is necessary to see and handle actual materials and processes in order to appreciate their significance, as all who have worked in laboratories know. The advice which Huxley gave to the "paper philosophers" of his day is still good advice: "Get a little first-hand knowledge of biology." But the opponents of evolution not only lack such first-hand knowledge, they usually have no desire to get it second-hand viii PREFACE TO NEW EDITION

from those who have studied nature. One of these denouncers of Darwin, when asked if he had ever read his books, repHed: '^I wouldn't touch them with a ten-foot pole." Neither facts, evidences, nor sweet reasonableness can penetrate such an armor. With very few exceptions, the whole scientific world long since was convinced of the truth of evolution, and every year which has passed since the publication of the "Origin of Species," in 1859, has added to the mountain of evidence, which has been piled up in its favor. It is fortunately not necessary here to review those evidences, for they may be found in almost every elementary text-book on biology, as well as in hundreds of treatises and scientific journals. These evidences are so numerous and come from so many sources that no intelligent man can study them at first hand and not be convinced of their importance. As a consequence there is probably not a single biological investigator in the world to-day who is not convinced of the truth of evolution. The fact that these evidences accumulate year after year, coming sometimes from fields which Darwin and his contemporaries never dreamed of, is still more convincing. Lord Kelvin, the great physicist, once said that any hypothesis or theory, if true, should find new support continually as knowledge advances. This is just what has happened in the case of evolution.

PREFACE TO NEW EDITION ix

The opponents of evolution make much of the fact that it is only a theory or an hypothesis, but in this respect evolution does not differ from any other great generalization of science. The evidences for the major transformations in the evolution of man are not personal demonstrations, since they do not fall within the lifetime of a single individual, but they are the same sort of evidences as those for mountain building, stream erosion, glacial action, or any other secular change. Those who urge as an objection to evolution that it is only a theory neglect to say that their own views as to the origin of man can be dignified by no higher title. As between evolution and special creation we have to choose between two theories or hypotheses, and it is merely a question of evidence as to which is the more probable. All the evidence available supports the theory of evolution, it continually receives fresh support from new discoveries, it is not contradicted by any scientific evidence. Can the supporters of the theory of special creation say as much ?

Uncertainty among scientists as to the causes of evolution has been interpreted by many nonscientific persons as throwing doubt upon its truth. It is plain that the causes are complex and that they have not yet been fully discovered; it is even probable that some of the proposed causes are erroneous and will have to be abandoned. But

X PREFACE TO NEW EDITION

the same may be said with regard to the causes of gravitation, light, electricity, chemical affinity, life, or any other natural phenomenon. It is not fair or honest to quote the doubts of scientists regarding the causes of evolution as if they constituted an abandonment of the theory itself, especially when these same scientists in the same connection affirm that no informed person can doubt the truth of evolution. The fact of evolution is no longer in question among men of science; present uncertainty and doubt concern only the factors or causes. The problem of cause is never finally solved by science, for no sooner is one cause discovered than it gives rise to questions concerning the cause of this cause. Strange as it may seem, it is only with regard to supernatural phenomena that the causes are supposed to be fully known ! But, of course, this is due merely to the fact that no attempt is made to analyze such phenomena or causes.

If only the opponents of evolution could learn anything from past attempts to confute science by theology or the Bible, they would be more cautious. Such attempts have promoted neither science nor religion, as the controversies over the shape of the earth, its position in the universe, and its age abundantly demonstrate; and the case is not different with regard to the origin and development of life upon the earth. Scientific investi-

PREFACE TO NEW EDITION xi

gators and productive scholars have long since accepted evolution in the broadest sense as an established fact. Science now deals with the evolution of the elements, of the stars and solar system, of the earth, of life upon the earth, of various types and species of plants and animals, of the body, mind, and society of man, of science, art, government, education, and religion. In the light of this great generalization all sciences, and especially those which have to do with living things, have made more progress in the last century than in all the previous centuries of human history. Even progressive theology has come to regard evolution as an ally rather than as an enemy. The defenders of religion can only do their cause harm by bringing against this great generalization of science sentimental objections or supposed theological difficulties. The wiser course would seem to be to recognize the fact that scientific truth can be established only by scientific methods, and to attempt to readjust theological beliefs to advancing knowledge. If the human species, no less than all others, has come into existence by a process of evolution, what are the prospects for the future ? May we look forward to endless progress, or do present signs indicate that the human race has reached its climax? Toward what form of social organization is evolution leading ? What are the tendencies in the field of ethics and religion?

xii PREFACE TO NEW EDITION

Certainly no more important questions than these confront the human race, and, although it is impossible to give a final answer to any one of them, it is possible in the light of present tendencies and past principles of evolution to see at least dimly and in ghostly outline the mighty shadows and shapes of the future. It is in this spirit only, and not with the vain imagining that any human being can predict particular events which depend upon so many factors as are involved in the evolution of a race, that attention is invited in this book to the direction of human evolution.

E. G. C.

Preface To First Edition

The lectures which constitute this volume were given at the University of North Carolina in May, 1920, under the terms of the "John Calvin McNair Lectureship on the mutual bearings of science and religion upon each other." One or two of them were also delivered at Northwestern University, Mt. Holyoke College, Western University, and the University of Texas.

The topic chosen for this series is one in which the bearings of science upon religion are most vital, namely, the origin and destiny of the human race. I shall attempt to present certain conclusions of science regarding the evolution of man, and shall venture to draw from these conclusions certain inferences with regard to the future of the human race, but I have no desire to force others to accept these conclusions or inferences.

The spirit of science is freedom to seek and to find truth, freedom to hold and to teach any view for which there is rational evidence, recognition that natural knowledge is incomplete and subject to revision, and that there is no legitimate compulsion in science except the compulsion of evidence.

The method of science is to proceed from observa-

XIV PREFACE TO FIRST EDITION

tions to tentative explanations which are then tested by further observations and experiments, thus reaching general explanations or theories. Scientific theories are not mere guesses but are based upon careful, detailed observations, but where time and space forbid entering into details, as is true in these lectures, only general conclusions can be given. On the other hand the philosophical and religious deductions which are based upon scientific theories must necessarily be still more tentative, and it is hoped that the reader will take this for granted even though it is not always expressly stated.

The aim of real science, as well as of true religion, is to know the truth, confident that even unwelcome truth is better than cherished error, that the welfare of the human race depends upon the extension and diffusion of knowledge among men, and that truth alone can make us free.

It is not my intention to argue the truth of the general theory of organic evolution; the day for this is passed. Evolution in the widest sense is accepted by most men of science, and the evidences for it need not be recalled here. Nor do I propose to present in detail the evidences for the evolution of man; this has been done in many other places and need not be repeated here. My purpose is rather to consider the course of past evolution only in so far as it bears upon the present and to apply

PREFACE TO FIRST EDITION xv

the principles which have guided evolution in the past to the present and future evolution of the human race. In doing this I hope not only to deal with a phase of the subject which will be more immediately practical and profitable than a mere consideration of past evolution would be, but which also may avoid many controversies, for whatever our views may be as to the past evolution of man there is general belief in the present and future development and evolution of the human race.

Finally, in considering the bearings of evolution upon government and religion, I realize that I am dealing with subjects which are generally regarded as quite outside the field of biology. However, I am convinced that nothing which concerns man is wholly foreign to the fundamental principles of life and evolution, and that the future progress of mankind depends upon a rational application of the principles of science to all human affairs. Everywhere intellectual classes are breaking away from old traditions; everywhere old faiths are being critically examined; everywhere evidence is demanded in place of authority, and the times call for a restatement of the reasons for the faith that is in us.

The recent cataclysm which has swept over the world, the perils of civilization, the threatenings of revolution and Bolshevism and the wide-spread recrudescence of emotionalism, irrationalism, and xvi PREFACE TO FIRST EDITION

selfishness have caused all thoughtful people to look anxiously to the future. Many persons believe that our civilization, like other civilizations of the past, is showing signs of degeneration and decay, that throughout the world the less intelligent and more selfish elements of society are coming to control government, industry, and education, while the best elements are dying out or are losing control. Others look forward with alarm to increasing conflicts between the races of mankind, to a "Rising Tide of Color in the Struggle for World Supremacy,"* and to elimination of the finest types in "The Passing of the Great Race." f

Chesterton says that the World War put a stop to aU our talk about human evolution, but this is certainly not true. Never before have the problems of the future evolution of man, whether progressive or retrogressive, been so insistent and absorbing, and never before has it been so important for men to get a comprehensive and steady view of human evolution and of human destiny.

Certain portions or abstracts of these lectures have been printed in Princeton University Lectures ^ Scribner's Magazine, the Yale Review, and the Methodist Church Congress Series. I am indebted to these publications for permission to rewrite and enlarge these portions for this volume. I wish also

* Stoddard, Lothrop, New York, 1920. t Grant, Madison, New York, 1918.

PREFACE TO FIRST EDITION xvii

to express my obligations to Dr. J. H. McGregor of Columbia University for the photograph of his restorations of primitive men, which is reproduced in the frontispiece, and to some of my colleagues for

friendly advice and criticism.

E. G. C.

Contents

PAGE

Preface to First Edition xiii

I. PATHS AND POSSIBILITIES OF HUMAN EVOLUTION

I. Introduction 3

A. The Law of Continuity 7

B. The Principles of Evolution ... 9

1. evolution is TRANS-rORMATION AND

NOT NEW-FORMATION 9

2. EVOLUTION IS TRANSFORMATION OF

GERMPLASM AND NOT OF DEVELOPED

BODIES OF ANIMALS OR PLANTS . . lO

3. INFLUENCE OF ENVIRONMENT ON EVO-

LUTION II

INHERITANCE OF ACQUIRED CHAR- ACTERS . 13

4. SOCIAL INHERITANCE 14

C. The Results of Evolution .... 15

1. diversity 15

2. adaptation .;..,... l6

(a) the PATHS of progress .... 18

(b) progress most rapid at first . 19

II. The Past Evolution of Man 25

III. Modern Races of Men ...... 31

IV. The Peopling of the Earth . . . . .36 V. Hybridization of Races 47

XX CONTENTS

PAGB

VI. Present and Future Evolution of Man . 54

A. Physical Evolution 54

EUGENICS i . 56

B. Intellectual Evolution 65

C. Social Evolution 69

D. Man's Conquest of Nature .... 77

VII. Will there Be a Higher Animal than Man ? 79

II. EVOLUTION AND DEMOCRACY I. The Biological Foundations of Society

A. Physical, Intellectual, Social Evolu tion not Antagonistic , . .

B. Social Progress Means Greater Spe cialization and Co-operation

C Society Founded on Instincts .

II. Progress in Human History . . . III. The Biological Bases of Democracy

88 90

IV. Personal Liberty vSi Social Organization 112

V. Democratic Equality vs. Hereditary Inequality 127

VI. Universal Fraternity vs. National and

Class Antagonisms 134

Conclusion 155

III. EVOLUTION AND RELIGION

I. The Nature of Religion 161

A. Cosmic Mysteries 162

CONTENTS xxi

MCE

B. The Problem or Evil 163

C. The Inner Conflict 165

D. The Function of Religion .... 166

II. The Evolution of Religion , . . . . 169

ni. The Conflict between Theology and Science 178

rv. Nature and the Supernatural .... 185

A. Popular Misconceptions of Nature

AND THE Supernatural .... 186

B. Scientific Conception of Law , . . 193

C. Supernaturalism in Religion . . . 197

V. Evolution vs. Creation . . . . . .202

VI. Evolution and the Biblical Account . . 206

VII. Is Evolution Atheistic? 209

VIII. Evolution and the Doctrine of Design . 218

IX. The Nature of Man 230

X. The Religion of Evolution 237

A. Progress through Struggle .... 237

B. Ethnocentric rather than Egocentric 240

C. The Outcome of Evolution .... 245

PATHS AND POSSIBILITIES OF HUMAN EVOLUTION

Introduction

Until about fifty years ago it was generally believed, even by scientists, that man had been recently and miraculously created, and that he stood apart from the rest of nature in solitary grandeur. It was thought that the whole past history of man and even of the earth and stellar universe had been a very brief one, dating back only to about 4,000 years B. C, or approximately 200 human generations, and many persons confidently expected that the future would be even shorter. It is an interesting fact that until very recent times the instability of nature and its approaching end were deeply impressed on most minds. Prophets looked forward to a speedy end of the world; poems were written on "The Last Man"; various sects prepared their ascension robes and waited for the comet to strike the earth or the eternal trumpet to sound; and even those who did not prepare often believed and trembled.

What a revolution has occurred in our conception of man and nature during the past few years ! Science has taught us something of the wonderful stability of nature, something of the continuity and eternity of natural processes, something of the universality of natural law, something of the immensity of time and space. There is no longer any doubt among scientists that man is descended from animal ancestors. There is no longer any serious question among leading biologists and anthropologists that not only the body, but also the mind and society of man are the products of evolution. For a time there was a tendency to admit the truth of evolution so far as man's body was concerned, but to deny it in respect to his mind and society. But this position was satisfactory to no one. Neither the evolutionist nor the special creationist could be satisfied with such a divided origin for man, and more recent work on the psychology and society of different races of men and of animals below man has shown the same sort of evidence for the evolution of human intellect and society as for the evolution of the body. Man, then, in his entirety is regarded by science as the product of evolution. His actual origin goes back not to Adam and Eve and the Garden of Eden, 6,000 years ago, but to more primitive races of men, and then to prehuman ancestors, and in the end to the earliest forms of life upon the earth. Between us and these earliest forms there has been an unbroken line of descent, an uninterrupted stream of life through all the ages.

And this enormously long past history leads us to beUeve that the future will be equally long. It has been customary to look upon evolution as a process which flourished mightily "in the dark backward and abysm of time" but which has practically come to an end to-day. But evolution looks forward as well as backward. The eternal laws of nature will not cease to operate to-day or to-morrow. We are creatures of a day; our lives are mere points in the great curve of evolution; what changes the future may have in store for the human race no man can clearly foresee. And yet one who stands on the shore and sees the curve of the sky and sea can, in imagination, extend this arc until it circles the globe, and he feels the earth beneath him rolling through space. From a few observations an astronomer can calculate the whole orbit of a comet and predict when it will return, perhaps hundreds or thousands of years hence. And so, although we catch but glimpses of great processes which come out of eternity and go into eternity, we can project the great principles of past evolution into the future and venture upon a scientific prophecy of "What mankind shall be."

It was the peculiar ability of Darwin to see nature in four dimensions — length, breadth, depth, and duration. He observed the activities of earthworms for a season, and then calculated the agricultural and geological importance of worms acting through many years. He observed the minor variations of animals and plants, and then saw the evolutionary significance of such changes when extended throughout geological time. He saw the great destruction of weak and ill-adapted plants and animals each year, and projecting this process backward through the ages found a natural explanation for the wonderful fitness of organisms.

One who stands on the brink of the Grand Canon and reflects on the duration of time necessary for a stream of water to have cut this vast chasm in the solid rock, and then thinks of the still longer time during which these rocks were being laid down as sediments beneath the sea, has a measuring-rod which may be used in estimating the duration of the evolutionary process. One who views man, not as the creation of a few years ago, but as the product of vast series of prehistoric ages — such a one only can take the long view with regard to the human race, not only as to the past but also as to the future.

There is increased breadth of view and accuracy of judgment and increased confidence and satisfaction in the long view of the human race as contrasted with the short view. One who has in mind the whole course of evolution and of human history will not be deceived into thinking that local eddies and back currents are the main stream. One who recalls what the human race has come up from will not yield to despair over the present crises of civilization. 'Even the selfishness, stupidity, and irrationality of men will not cause him to forget the advances of the past nor to lose faith in the future. The long view of human history is not only the sane and rational one, but it is also the hopeful view.

It is often said that science deals only with the past and present and leaves the future to prophets and seers. This is true with regard to many details the causes of which are numerous and complex. But on the other hand it is possible to predict general tendencies and phenomena which will result from fundamental principles and causes. The details of the future evolution of man no one can predict, but the outcome of the general principles of evolution may be predicted, for we have confidence that these principles are constant and that they will continue to operate in the future as in the past. What are these principles?

A. The Law of Continuity

"To understand what has happened, and even what will happen, we have only to examine what is happening." This is what has been called the "Law of Continuity" — or more accurately the "Doctrine of Uniformity," namely, the belief that nature is uniform and her processes continuous, that the laws of cause and effect, of gravity, of conservation of matter and energy, of thermodynamics, chemical affinity, life and death, heredity, development, and evolution are the same yesterday, to-day, and forever. The astronomer, physicist, and chemist believe that laws of gravity, light, electricity, and the combinations and dissociations of chemical elements are the same to-day as when the "morning stars first sang together." The biologist believes that the animals which lived and reproduced on the shores of the Paleozoic seas had protoplasm and cells, nuclei and chromosomes, and that their nutrition, reproduction, embryonic development, senescence, and death were essentially the same as in the animals we now study at our marine laboratories; that the Mendelian laws of inheritance, variation, and evolution applied to the earliest living things as well as to the latest. All science is based upon the fundamental belief that in natural laws ** there is neither variableness nor shadow of turning." Variableness in events (not in laws), and even what we call chance, are not capricious but are themselves governed by law; they are merely the results of new combinations of existing factors or causes. We have applied this principle of continuity and uniformity to the past evolution of the universe, to the stars, solar system, and earth, to the evolution of animals and plants, and even of man; and in the light of what is happening now have been able to Judge what has happened in the past. And where the factors involved are not too numerous we can apply this principle to the future and determine what will happen in time to come; and, even where it is not possible to predict with certainty particular events because of the complexity of the factors involved, it is yet possible to determine future tendencies and Dossibilities.

B. The Principles of Evolution

I. Evolution Is Trans-formation and Not New-formation

Evolution consists in new combinations of the elements of which organisms are composed and not in the formation de novo of such elements. Nowhere in nature, neither in the living nor in the lifeless world, is there such a thing as creation out of nothing. Every new thing is formed by new combinations of things already present. In chemistry and physics these are the atoms or the electrons of which the atoms are composed; in biology they are the organs, cells, chromosomes, the hereditary characters, inheritance units, or the molecules of which such units are composed. Evolution does not consist in the creation de novo of molecules, units, characters, organs, or functions, but rather in new combinations of these.

At the same time it must be recognized that new combinations give rise to new quaUties. When lO PATHS AND POSSIBILITIES

hydrogen and oxygen combine they produce something which is different from either, and when different hereditary units combine they produce characters unhke those of the parents; even in the formation of new hereditary units, or what are now called mutations, we have only new combinations of the elements of which such units are composed. This formation of new qualities as the result of new combinations of the same old elements may be called, following Bergson, "creative evolution," but it is important to remember that it does not differ essentially from the similar phenomenon in chemistry and physics which is known as "creative synthesis," and that it results merely from new combinations, that it is transformation and not new-formation.

2. Evolution Is Transformation of Germplasm and Not of Developed Bodies of Animals or Plants

The only living bond between successive generations is found in the germ cells, which extend back from us without a break to our earliest progenitors, and any evolutionary changes which are to transform races or species must take place in these germ cells. The body may undergo great changes as the result of environment, use or disuse, or other causes, but the body is mortal — it develops and dies in each generation — whereas the germ cells are, potentially at least, immortal. Consequently

PATHS AND POSSIBILITIES ii

changes in heredity are due to changes in the immortal germplasm rather than in mortal bodies; and evolution, which is based on changes in heredity, consists in the evolution of germplasm rather than of developed organisms.

In spite of much controversy, due largely to lack of clear thinking, it is now practically certain that characters acquired by the mortal body are not inherited; that is, are not transmitted to the germplasm. Evolutionary changes are not first wrought in developed bodies but in germplasm.

3. Influence of Environment on Evolution

All theories as to the causes of evolution agree in ascribing more or less importance to the influence of environment. Lamarckism maintains that changes in individuals are caused directly by changes in environment, and that these individual changes are inherited and thus bring about racial changes. Darwinism teaches that "variations of every sort are caused by changed conditions of life," but that those which are injurious are quickly eliminated while only those which are beneficial, that is, well adapted to environment, persist and constitute the building materials of evolution. The mutation theory of de Vries teaches that variations are of two distinct kinds: first, fluctuations which are changes in the developed organism and are not inherited; and second, mutations which are changes in the germplasm and are inherited. Fluctuations are caused chiefly if not entirely by changes in environment, and while the causes of mutations are not known with certainty it seems most probable that they also are to be found in environmental influences — meaning by environment everything which surrounds the inheritance units or genes of the germplasm. These mutations appear without reference to whether they are valuable or injurious; as a matter of fact probably only one out of a thousand is beneficial, but those which are injurious are eliminated by the environment. Consequently the direction of evolution has to a certain extent been determined by the environmental conditions.