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WHERE EVOLUTION AND
RELIGION MEET




j^M0 -THE MACMILLAN COMPANM
NEW YORK * BOSTON * CHICAGO * DALLAS
ATLANTA * SAN FRANCISCO
MACMILLAN & CO., LIMITED
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TORONTO




WHERE EVOLUTION AND
RELIGION MEET
BY
JOHN M. COULTER
Professor and Head of the Department of Botany
at the University of Chicago
and
MERLE C. COULTER
Assistant Professor of Plant Genetics
at the University of Chicago
Nrma Iork
THE MACMILLAN COMPANY
1924


All rights reserved




COPYRIGHT, 1924,
BY THE MACMILLAN COMPANY.
Set up and printed.
Published February, 1924.
Reprinted November, 1924.


Printed in the United States of America by
THE FERRIS PRINTING COMPANY, NEW YO0K.




CONTENTS
CHAPTER                                       PAGbE
I. INTRODUCTION...............              1
II. EVIDENCES OF EVOLUTION........         12
III. LAMARCK'S THEORY OF USE AND DISUSE... 23
IV. DARWIN'S THEORY OF NATURAL SELECTION.. 31
V. THE MUTATION THEORY OF DE VRIES..   46
VI. SOME OTHER THEORIES OF EVOLUTION....    55
VII. MODERN VIEWS ON EVOLUTION.......        68
VIII. INFLUENCE OF THE EVOLUTION IDEA....     78
IX. EVOLUTION AND RELIGION......... 98








WHERE EVOLUTION AND
RELIGION MEET
INTRODUCTION
No subject of science seems to be more misunderstood by those who are not biologists than the doctrine
of evolution. It has been discussed very freely by
those who are not informed, and in this way much
misinformation has been propagated. It has aroused
so much interest, not to say antagonism, that it seems
timely to explain it in terms that the general reader
can understand. The evolution of the material world,
called inorganic evolution, aroused wonder but not
apprehension; but when organic evolution came into
i prominence hostility was aroused, because such evolution involved man.
Why is it that so many people are opposed to the
idea of evolution? Clearly this is not because they are
in possession of critical evidence that refutes evolution,
for practically everyone who has devoted an adequate
amount of time and thought to a consideration of the
available evidence has become convinced that evolution is a fact. We must conclude, therefore, that those
who are opposed to evolution have no very definite
understanding of the subject, and base their disbelief
on prejudice.                                 i
i Why does this prejudice exist? Two reasons seem
to be mainly responsible. First, it is felt that evolution contradicts the Bible; and we cannot blame those j
1




2    WHERE EVOLUTION AND RELIGION MEET
who are opposed to evolution for this reason, for they
have been taught by those whom they have the greatest reason to trust that the Bible is to be relied upon
implicitly, and that to question it is sinful. Second,
it is the popular impression that evolution requires us
to believe that men have descended from monkeys;
and this is a shock to one's vanity, for we have a very
poor opinion of monkeys. For these two reasons, many
people have concluded that the evolution concept is
degrading, and hence they will have none of it.
We have no desire to criticise those who hold this
impression about evolution for the reasons indicated.
Their reactions are quite natural, but their information
has been incomplete, and those who base their conclusions on incomplete information are quite commonly
( in error. When one has been completely informed conk    cerning evolution, he realizes that it does not contradict
r   G the Bible in any serious way, but really teaches the
same fundamental truths from a different point of view.
Furthermore, the careful study of evolution is the very
thing which shows us that man could not have
descended from the monkeys or apes of today. Ages
ago the ancestors of man, monkey, and ape sprang
from a common source, and the same may be said of
all forms of animal life. Thge acqcouInt of how man and
all other forms of life emerged from such humbleTeginnings and radujalydl Qe   dinto the more  r-Te-         toa isoIar from degrading  Instead it
presents about the most ennobling and inspiIct —
cept t at we have.  nowing that t  STe
"present autoris wish to perform, in some measure, the
service of informing the public concerning the present
status of evolution.
There is a very significant fact bearing upon the
popular prejudice against evolution. Those who maintain that evolution is degrading, actually acknowledge
evolution, without recognizing the fact, and in their




INTRODUCTION


3


life and actions give evidence that they find more
interest and inspiration in the evolution concept than
in anything else. Evolution is change; organic evolution is that type of change in which a living organism
(plant, animal, or man) becomes "better adapted to
the environment," develops and perfects the equipment with which the requirements of life are met. In
his life every man becomes interested in one or more
of a number of enterprises. The real reason that he
becomes interested in these enterprises and inspired
by them lies in the prospect of his own evolution.
Man always cherishes the hope that, in connection
with one or the other of these enterprises, he will
achieve what he calls "success." This success comes
only as the result of his better adaptation to the
environment, through his developing and perfecting
the equipment with which the requirements of life are
met. This is evolution, and it is this evolutionary
prospect that interests, inspires, and ennobles mankind. This may be illustrated by a few concrete
examples.
The human enterprise that seems to absorb more
attention than any other is the attainment of wealth.
The interesting and inspiring feature arises from the
prospect that one may change from a state of relative
poverty to one of relative wealth. In this project one
attains success through a better adaptation to the
environment, through the effort to develop and perfect the equipment with which he meets the requirements of life; for it can clearly be recognized that the
wealth that man strives to attain is an improved equipment with which to meet the requirements 'of life.
Through it all man has been interested and inspired
by an evolutionary project; for we all know that the
interest and inspiration come with the attainment of
riches rather than the mere possession of riches from
the start.




4  WHERE EVOLUTION AND RELIGION MEET


Another common human enterprise is the attainment of knowledge. Every student recognizes that
here also the real interest and inspiration lie in the
process of his own development, in the attainment of
knowledge rather than the mere possession of knowledge from the start. Again this is an evolutionary
project, a gradual development and perfection of an
equipment with which one can better meet the requirements of life.
An athlete is interested and inspired mainly by the
prospect of his development, in his change from a
condition of relatively less to relatively greater success
at some sport; and in any sport the spectators are
more interested in the evolutionary phase than in any
other feature. The great satisfying thrills come in
seeing some favorite athlete improve his technique,
in watching some team work and fight its way up
from a poor start to a final perfection and success. In
any single game we tend to cheer the side that is
behind, for we receive the most pleasure in witnessing
the evolutionary spectacle which presents itself when
the prospective loser struggles through to win out in
the end. What thrills us is the process of improvement, the evolution from an unsuccessful (poorly
adapted) to a successful (well adapted) position.
Others become devoted to the enterprise of attaining power (for example, political power) among their
fellow men. In this matter also the one who gets the
real interest and inspiration is the one who, from a
humble beginning, gradually works his way into a
commanding position. When we read either history
or fiction, we are far more thrilled by accounts of some
person who has undergone an evolution from obscurity
to prominence, than by accounts of one who merely
maintained, without further improvement, a commanding position that was bestowed upon him at the
start.




INTRODUCTION


5


In addition to these human enterprises in which the
goal to be attained is a rather definite one, there is
another common objective which we find running
through all of them, or sometimes standing out as an
enterprise by itself. This is the attainment of personal
efficiency. Whatever one is doing, he is usuaUy interested and inspired by the prospect of doing that
thing more efficiently. This involves considerable
effort devoted to practice and study, but there is
usually ample reward in the satisfaction one receives
from the realization that he is more efficient than before. This perfecting of personal efficiency plays a
large part in the lives of technicians, professional men,
and artists. As in the other cases, the interest and
inspiration arise from the prospect of becoming better
adapted to the environment, in developing and perfecting that equipment (personal efficiency) with
which one meets the requirements of life. Often this
improvement of personal efficiency is merely incidental
in interest to the attainment of wealth and power, but
sometimes we find a person interested merely in the
perfection of personal efficiency in itself. This last is
plainly seen in some artists and authors who get a real
satisfaction out of one of their works that bears witness
to improved efficiency, whether or not it may bring
them great wealth or fame.
Finally, there is that great human enterprise which
consists of the perfecting of one's character. In most
cases this is accomplished under the guidance of some
sort of formal religion. In this matter we can surely
recognize that the inspiring and ennobling feature lies
in the hope and prospect of the development and perfection of self along certain "evolutionary" paths that
have been outlined by those great thinkers who are
the authors of our religion. The inspiration that we
get when we "see the light" arises from our first clear
vision of this prospect and hope. In other cases people




6  WHERE EVOLUTION AND RELIGION MEET


may be making a conscientious effort to perfect their
own characters according to some informal code that
they have figured out for themselves, rather than to
follow the doctrines of formal religion. In either case
one strives constantly to improve his character and
personality through attainment of such personal
qualities as courage, temperance, and unselfishness.
This is evolution. The achievement of these high aims
involves a better adaptation to the environment, a
development and perfection of the equipment with
which one meets the requirements of life. Here the
environment is made up mainly of those other human
beings with whom we come in contact, and the requirements of life are for a more sympathetic and effective
cooperation with our fellow men.
It is this same great evolutionary principle which
runs through all human enterprises, which provides
the interest and inspiration which we feel for these
enterprises. In every case the prospect which engages
our attention, which thrills us and stimulates us to
our best efforts, is the gradual improvement of ourselves, our institutions, our communities, or our
nations toward the goal of perfect adaptation or adjustment to the surrounding conditions. The real
significance of that fascinating idea, "success," lies in
the evolutionary implication. It is really true, therefore, that mankind, instead of holding a natural prejudice against evolution, actually recognizes it as the
most interesting, inspiring, and ennobling concept of
all. The same fundamental evolutionary principles
which underlie all human enterprise apply also to the
whole history of living organisms on the earth, from
the very simplest beginnings to the rather highly perfected organisms of today, with man as the culminating achievement, the most perfect organism of all.
The general meaning of organic evolution is that
the plant and animal kingdoms have developed in a




INTRODUCTION


7


continuous, orderly way, under the guidance of natural
laws, just as the solar system has evolved in obedience
to natural laws. Scientific men who stand for this
idea must not be regarded as attacking any creed regarded as sacred. They are simply desirous of proving what is true and useful. Their one thought is to
discover the truth, and their method is to observe the
facts that will help to disclose the truth. From these
facts they draw certain conclusions, which at the time
seem consistent with the facts and explain them.
Later, additional facts may show that the proposed
explanations are inadequate, but the facts remain to
be explained. Much misunderstanding has arisen
from confusing fact with its attempted explanation.
It should be kept clearly in mind that the fact of
evolution is one thing, and any proposed explanation
is a very different thing. All of the proposed explanations may prove inadequate, and still the fact remain
to be explained.!For example, the rotation of the
earth is a fact, Nut it was a long time before any
adequate explanation was offered. It is very common
to confuse evolution with what is called Darwinism,
which is simply a name given to Darwin's explanation
of the fact of evolution, one of a number of explanations that have been offered, no one of which may be
adequate to explain all the facts. Of course we must
first show that evolution is a fact, and then try to
explain it, but the two processes must not be confused.
It has been too often claimed, when some explanation
has proved insufficient, that biologists have given up
belief in evolution. Belief in evolution is the working
basis of all biologists today, and the discovery that
some explanation is inadequate does not induce disbelief in the fact, but is a triumph of biological investigation, which is continually "on the way" toward an
adequate explanation.
The purpose of this book is not to unsettle the faith




8  WHERE EVOLUTION AND RELIGION MEET


of anyone in some creed that has proved satisfactory
and stimulating to him. We are not seeking to make
converts to a belief in the doctrine of evolution. The
purpose is simply to give some information that may
prove interesting and useful, and that will serve to
correct a good deal of misinformation that is current.
In other words, we shall try to give trustworthy information, and leave it to the reader to draw his own
conclusions. It is simple justice to develop a mutual
understanding as to certain gross misconceptions that
have crept into the mind of the general public in
reference to evolution.
To believe without adequate information is the impulse of those who are unreasonable. It is not characteristic of those who want the facts before belief is
reached. We are assuming that our readers will be
interested in the evidences of evolution, and will read
with an open mind rather than with preconceived
notions. The story we shall tell is not fiction, but
actual history with which one should become familiar.
The fascination of this history is not that it is all
pleasant, any more than is human history, but that it
portrays continual progress. In other words, the story
has an attractive outcome.
It is well to understand what is meant by the scientific attitude of mind, an attitude that has been developing with the progress of science. It is an attitude
that seeks to extend the domain of human knowledge,
by facing problems frankly and trying to solve them.
In the first place, the scientific spirit is a spirit of
inquiry. In our experience we encounter a vast body
of established belief in reference to all important subjects. Nothing seems more evident than that all this
current belief which we encounter falls under two
heads; the priceless result of generations of experience,
and heirloom rubbish. Toward this whole body of belief the scientific attitude of mind is one of unprej



INTRODUCTION


9


udiced inquiry. The spirit which resents inquiry into
any belief is the narrow spirit of dogmatism. The
childhood of the race accumulated much which its
manhood is compelled to lay aside, and the world needs
a thorough going over now and then of its stock in
trade. Such work cannot be done all at once, or once
for all. Science is continuously at work sorting over
this heritage from the past, refuting and discarding
those ideas which are false, confirming and preserving
those which are true.
Such a spirit is diametrically opposed to intolerance,
and it can find no common ground with those who confidently claim that all of our institutions and beliefs
have reached their final expression. It is not the spirit
of unrest, of discomfort, but the evidence of a mind
whose every avenue is open to the approach of the
truth from every direction. Like the tree, it is rooted
and grounded in the eternal truths that the past has
revealed, but is stretching out its branches and everrenewed foliage to the air and sunshine, and taking
into its life the forces of today.
For fear of being misunderstood, we hasten to say
that this beneficent result of scientific training does
not come to all who cultivate it, any more than the
Christ-like character develops in all those who profess
Christianity. We regret to say that even some who
bear great names in science have been as dogmatic as
the most rampant theologian. But the dogmatic
scientist and theologian are not to be taken as examples of the "peaceable fruits of righteousness," for
the general ameliorating influence of religion and of
science is none the less apparent.
In the second place, the scientific spirit demands a
real connection between an effect and its claimed
cause. People in general do not appreciate how many
factors may be involved in a given result. The prevailing belief among the untrained is that any result




10   WHERE EVOLUTION AND RELIGION MEET
may be explained by some single factor operating as
a cause. An enthusiast discovers some one thing which
he regards, and which perhaps all unprejudiced and
right-thinking people regard, as an evil in society, and
straightway this explains for him the whole of our
present unhappy condition. This particular tare must
be rooted up immediately, without any thought as to
the possible destruction of the plants which we must
cultivate. This habit of considering only one factor
when perhaps scores are involved, indicates a very
primitive and untrained condition of mind. This is
where political demagoguery gets in its most unrighteous work, and preys upon the gullibility of the
untrained; and is the soil in which the noxious weeds
of destructive socialism, charlatanism, and religious
cant flourish.
In the third place, the scientific spirit keeps one
close to the facts. There seems to be abroad a notion
that one may start with a single well-attested fact, and
by some logical machinery construct an elaborate system and reach an authentic conclusion. The result is
frequently bad, even when the fact has an unclouded
title; but it happens too often that great superstructures have been reared on a fact that is claimed rather
than demonstrated. Facts are like stepping stones.
So long as one can get a reasonably close series of
them, he can make progress in a given direction; but
when he steps beyond them he flounders. As one
travels away from a fact, its significance in any conclusion becomes more and more attenuated, until
presently the vanishing point is reached, like the rays
of light from a candle. A fact is really influential only
in its own immediate vicinity; but the whole structure
of many a system lies beyond the vanishing point.
Such "vain imaginings" are delightfully seductive to
many people, whose life and conduct are even shaped
by them.




INTRODUCTION                11
The ideals of science may be summarized as follows:
They are first, to understand Nature, that the boundaries of human knowledge may be extended, and man
may live in an ever-widening horizon; second, to apply
this knowledge to the service of man, that his life may
be fuller of opportunity; and third, to use the method
of science in training man, so that he may solve his
problems and not be their victim.




II


EVIDENCES OF EVOLUTION
WHEN we consider the vast array of animals and
plants found in nature today, the question very naturally arises in our minds, "How have these many different types of living organisms come into existence;
what has been their origin?" This question may be
answered in one of two ways.
(1) Some would say that each of the different types
of animals and plants had a distinct origin of its own.
This assumption would force us to believe that at some
time in past history there suddenly appeared upon this
planet the first lion. As to what may have produced
this lion, or what materials went into the make-up
of the beast, these questions are not clearly answered. It is simply assumed that there was in existence some force which could produce in this abrupt
manner a fully developed lion where no lion had
existed before. In other words, the lion was suddenly
produced by "special creation." As an event quite
distinct from this first one, there appeared in a similar
way the first tiger. Still another event was the sudden
appearance of the first leopard, and so on for every
one of the many types of animals and plants that we
see around us today. Each was produced quite
separately, so that no two types are in any way related to one another. The agent which acted to bring
about these results, the method of the creations, and
the materials used are not explained.
(2) Others would answer the question as to the
12




EVIDENCES OF EVOLUTION


13


origin of the animals and plants of today in quite a
different manner. We are perfectly certain of the fact
that today, and for as long as man can remember,
individual animals and plants have come into existence in only one way, through descent from other
animals and plants. The parent begets the offspring
by means of a process of reproduction, and we have
every reason to believe that this same process has been
repeated innumerable times in the past, throughout a
period of countless thousand of years. During this
time there has been ample opportunity for some of
the descendants of the original individuals gradually
to become modified so that they no longer are exactly
like their original ancestors.
For example, there was in existence, many thousands
of years ago, a single type of cat-like animal. One
group of its descendants very gradually, through the
lapse of countless generations, became modified into
the lion of today. Another group of descendants of
this same ancestral type, through very gradual changes
that occurred during the course of thousands of years,
finally developed into the tiger. Still another line of
descent from this same beginning resulted in the
leopard of today. Hence all of the various types of
cat-like animals that we see today are really related,
for they have all sprung from the same source, a common ancestor that lived some time in the dim past.
According to these same principles, it is believed
that all animals and all plants are the descendants of
one or a very few original types that existed in the
past. Throughout the ages there have been taking
place gradual changes among the many descendants
of the original types, a process of "evolution" has been
going on, and it is in this way that we may account
for the existence of so many different types of plants
and animals today.
It is this second view that has been accepted by




14 WHERE EVOLUTION AND RELIGION MEET
scientific men. Special creation, they believe, is much
less reasonable, much less successful in fitting the
known facts of nature, than the evolution concept.
For many years biologists have been discovering additional bits of evidence which demonstrate that evolution is the true story of the past history of our animals
and plants. Such an enormous mass of evidence has
by this time been accumulated that, in scientific circles,
evolution is regarded no longer as a mere theory, but
as an established fact.
We shall present some of this evidence, and see why
it is that scientific men are convinced of the truth of
evolution. The evidence is obtained from some of the
actual facts of nature, facts which become very significant if we accept the evolution concept, but which
are quite meaningless if we do not. By no means all
of the available evidence will be discussed, for it requires considerable training in biology to appreciate
some of the lines of evidence.
EVIDENCE FROM ANIMAL STRUCTURES
When we make an examination of the organs and
tissues of that vast array of animals which are
equipped with back-bones, we find that there is one
general body plan which prevails through all of them.
The skeletons of the horse, the dog, the cat, and of
man show a fundamental similarity, and differ only
in certain minor details. Certain bones may in some
cases be relatively longer or thicker or have a slightly
different general outline, but for practically every bone
in one of these types we find a corresponding bone in
the others, and the general plan of arrangement is
essentially the same. The same feature appears in
connection with the other tissues also. A muscle has
the same fundamental make-up in each case, shows
the same method of attachment to the bones, and
functions according to the same principles. Certain




EVIDENCES OF EVOLUTION


15


muscles are in some cases more highly developed than
in others, but the set of muscles with which the animal
is provided is essentially the same in each case. The
same similarity of body plan appears in connection
with the nature, arrangement, and method of functioning of blood-vessels, glands, nerves, and even in connection with the very highly specialized tissues of the
brain. One who makes a study of these facts finds it
much easier to believe that all of these animals are
the modified descendants of one original ancestral type,
which possessed this general body plan, than to believe
that each had a separate origin as the result of special
creation.
There is another feature, frequently encountered in
the study of animal structures, that provides a rather
striking form of evidence for evolution. In many
animals there appear certain organs which are clearly
underdeveloped and useless. There is a type of snake
that possesses hind limbs. These structures, however,
are so underdeveloped as to be scarcely visible from
the outside, and are never used in any way by the
snake that possesses them. The whale is endowed
with the same apparatus of the internal ear as are
those of our higher animals which live upon the land.
This apparatus is adapted to hearing in air. In the
whale it is very much reduced and degenerated and
is not used for hearing. The eye provides the power
of sight to those animals that live in the light. Animals
that spend their lives in dark caverns frequently possess degenerated eyes which are utterly useless to them.
There appear countless examples of such underdeveloped and useless organs among the many members
of the animal kingdom.
How can such things be accounted for on the basis
of special creation? When these animals were created,
why should they have been equipped with organs that
were of no use to them? The evolution concept, how



16 WHERE EVOLUTION AND RELIGION MEET
ever, provides a ready interpretation for these matters.
The underdeveloped and useless structure which we
find in one animal is represented by an organ which is
fully developed and very useful in another animal.
The two types of animals are related, are descended
from a common ancestor. The common ancestor was
endowed with the organ in question in its fully developed and useful condition. Some of the descendants
retained this organ in the same condition. Another
line of descendants, however, encountered changed
conditions of life, such that this particular organ was
no longer useful. As a result the organ was allowed
to dwindle away in successive generations until it had
reached a very much reduced condition.
This interpretation would be applied as follows to
the examples which were used. The snake descended
from an ancestor which had functional hind limbs, but
had dispensed with the use of the limbs for so many
generations that they had degenerated almost to the
vanishing point. The whale is a relative of our higher
land animals. The original common ancestors, which
lived on land, possessed an ear which was adapted to
hearing in the medium of air. The whale, submerged
for countless generations in the waters of the sea,
gradually lost the use of this ear, so that its various
parts degenerated. Similarly the blind animals of dark
caverns are the modified descendants of forms which
lived in the light and possessed fully developed eyes.
It can be seen, therefore, that these underdeveloped
and useless organs, "vestigial structures" as they are
commonly called, find their significance, their interpretation, only in the evolution concept.
Still one more phenomenon, often encountered in the
study of animal structures, provides very impressive
evidence for evolution. The subject of "embryology"
considers the development of animal bodies from the
egg to the adult condition, noting every stage in the




EVIDENCES OF EVOLUTION


17


process. In many cases these developing bodies (embryos) show structures that disappear before maturity,
but often these are structures that persist in other
animals and are features of the adult body. It is hard
to imagine why structures appear in the embryo, only
to disappear, unless in ancestral forms these structures
persisted and were used. In other words, it is impossible adequately to account for such cases on the basis
of special creation; the only reasonable interpretation
is that which is provided by the evolution concept.
In some cases, usually in our very highest animals,
the developing embryo exhibits quite a series of these
structures that disappear before maturity. The very
young embryo will possess temporarily a structure
which appears in the adult body of a very remote ancestor. This structure will then be lost, and the older
embryo will exhibit some other temporary structure.
In this second case the structure is one which appears
in the adult body of a more recent ancestor. By means
of a series of this sort, the developing embryo may
summarize the evolutionary history of the race. The
young human embryo exhibits the gills of an ancient
fish-like ancestor. Soon these disappear, and the older
embryo develops a tail. How can such things be explained by special creation? Is it not evident that this
provides a record of our evolutionary descent?
The conclusions suggested in this case are really the
same as those derived from the vestigial structures
mentioned before as occurring in adult bodies. In fact,
these temporary structures of the embryo are merely
vestiges that have disappeared from the adult body,
but still linger in the embryo.
It can be seen, therefore, that a study of animal
structures provides three strong lines of evidence for
evolution: the evidence from comparative anatomy,
the evidence from vestigial structures of adult bodies,
and the evidence from the temporary vestigial struc



18 WHERE EVOLUTION AND RELIGION MEET
tures of the developing embryo. A study of plant
structures would reveal evidence of a similar sort, but
in that case the evidence would be less striking, for the
illustrations would be less familiar to the reader.
EVIDENCE FROM THE GEOLOGIC RECORD
During the early history of the earth, the continents
of olden times were traversed by a network of rivers.
These rivers were scouring away at the land surfaces
and carrying the resulting mud along with them. At
the mouths of the rivers, where the current was suddenly checked, this sediment was deposited. Year after
year this continued, until vast quantities of mud were
accumulated in such places. Eventually, through the
pressure of materials above, this mud became transformed into rock. In this way were produced the sedimentary rocks of an early geologic age. During later
ages rocks continued to be formed in the same manner
and the sedimentary rocks of a later age were always
deposited on top of the sedimentary rocks of a preceding age. Today we find many layers of these sedimentary rocks, and we know that the sequence of
the layers from bottom to top represents the historic
sequence of the geologic ages, from the earliest times
down to the present.
Now when the mud was deposited, very frequently
there were deposited with it the dead bodies of certain
plants and animals which inhabited the earth at that
time. These bodies, imbedded in the mud, often became petrified, so that they were preserved when the
mud changed to rock. Even when the plant and animal
bodies were not successfully petrified, they often left
behind them casts or impressions which persisted when
the mud hardened. So it is that today, upon breaking
open the sedimentary rocks, we encounter the fossil
remains of those plants and animals that inhabited the
earth at the time that the rocks were being formed.




EVIDENCES OF EVOLUTION


19


Very often these fossils consist of mnere fragments,
but in other cases they are surprisingly perfect. They
have been studied very carefully, and in this way the
plants and animals of one age have been compared
with those of another. If evolution is true, this geologic record should bear testimony to the fact, and
should reveal a definite story of the successive steps
that have taken place in the past evolution of our
plants and animals.
In this matter our expectations have been more
than realized. This impressive record of the rocks
shows that during the earliest known period plants
and animals lived that were entirely unlike those of
today. In the next period, different kinds of plants
and animals appeared, usually some of the old kinds
holding over. As period succeeded period, new kinds
of plants and animals appeared, and the old kinds disappeared, until, in the later fossils, resemblances to the
present plants and animals can be recognized. These
resemblances gradually increased, until finally, without any sensible break, our present plants and animals
appeared. In short, a tremendous stretch of history
confirms the evolutionary idea that plants and animals
have been changing from the first, and that the modern
forms are the modified descendants of these earlier
forms. Probably the geological record comes as near
being a demonstration of the fact of evolution as anything could be short of an actual experiment.
One of the classic examples is provided by the evolutionary history of the horse. In the rocks of an
early geologic age there appear fossils of an interesting
animal which had five toes and was only about eleven
inches in height. Among the fossils of the next succeeding age is an animal very much like this first one,
except that it is a little larger and has lost some of its
toes, having now only four toes on the front feet and
three on the hind feet. As we pass successively through




20 WHERE EVOLUTION AND RELIGION MEET
the ages we find a clear line of descent from these
original forms. Gradually the descendants become
larger, their limbs being elongated and their total
weight increased. At the same time they lose their
toes, until finally only the middle digit on each foot
is preserved, with but tiny vestiges of some of the
others. Along with these changes many others are
taking place. The grazing mechanism is perfected;
the head and neck gradually elongated and some of the
teeth equipped with complex grinding surfaces. As a
final culmination of this long line of descent, there
appears the horse of today. It is a clear story from
the beginning, demonstrating how the horse has descended through a series of gradual modifications from
an original ancestral type that was quite different.
What is true of the horse can be demonstrated as
well for a number of other animals. Long lines of
descent through the geologic ages can be traced for the
elephants, the camels, and even man, though in this
last case, as might be expected, the record covers a
shorter period of time. What can be shown for animals
can be shown for plants also. How can this geologic
record be accounted for on the basis of special creation?
What could be more clear testimony to the fact of
evolution?
EVIDENCE FROM CULTIVATED PLANTS AND DOMESTICATED
ANIMALS
From the evidence that has been considered up to
this point, man concludes that evolution has taken
place in the remote past. We shall now consider certain situations in which man has actually seen evolution taking place during the recent past.
When man first started to practice agriculture, he
chose for this purpose some of the wild plants and
animals that were the best suited to his needs. During
the centuries which followed, these types of plants and




EVIDENCES OF EVOLUTION


21


animals gradually became changed, gradually became
better suited to man's needs. Just how these changes
were brought about will be considered in some of the
later chapters. At present we are interested merely
in the fact that evolutionary changes actually did take
place under man's observation. Today we have many
very highly-developed varieties of cultivated plants
and domesticated animals, and, in many cases at least,
we know what were the wild ancestral types from
which these have descended. Comparison of the ancestral types with the present cultivated or domesticated varieties reveals vast differences, and we know
definitely in these cases that the differences have been
brought about by a gradual evolution.
Consider the many exceedingly different races of
dogs that have all been bred from one wild stock. Consider also the many varieties of cattle and of chickens.
The present-day types are quite different from each
other, and quite different from the wild original ancestor from which they have all descended. Even more
striking changes have been brought about among cultivated plants. Few people realize that the cabbage,
the cauliflower, the kohlrabi, Brussels sprouts, kale, and
collards are all descendants of the same wild ancestral
type. These forms are very different from each other,
and very different from their common ancestor, the
wild cabbage, which is still growing in some places.
These and many other modifications have been brought
about under man's observation. In these cases we
have seen evolution taking place. According to the
special creation concept such results should be impossible, but we know that they are possible because we
have seen them take place.
There are also a number of other lines of evidence
for evolution. These others, however, will not be discussed here, for the reader without biological training
would not fully appreciate them. We believe that the




22   WHERE EVOLUTION AND RELIGION MEET
few lines of evidence that have been presented are by
themselves sufficiently convincing. An even greater
conviction should be developed by the succeeding chapters, in which we shall turn our attention to the question of how the evolutionary process has taken place.




III


LAMARCK'S THEORY OF USE AND DISUSE
DURING the last decade of the eighteenth century,
three distinguished men had simultaneously and independently proposed the first explanation of evolution.
The evidences that evolution might be a fact had been
accumulating so rapidly that some attempt to explain
it was inevitable, and this first attempt came from the
three leading countries in scientific work. The three
men who proposed the same explanation were Goethe
of Germany, St. Hilaire of France, and Erasmus Darwin (grandfather of Charles Darwin) of England.
The explanation may be called the "theory of environment." It had been observed that birds change
their plumage and animals their fur with the changing
seasons, and this suggested that animals respond to
environment in a striking way. Animals were thought
to be plastic and moulded by environment, as clay may
be moulded by the fingers of a potter. In this explanation, therefore, environment was regarded as an external agency impressing itself on the bodies of animals,
and changing them to fit the environment better.
Of course there is such a thing as response to environment, and this was perhaps the first natural explanation of evolution, but it was soon found to be too
superficial to be at all adequate, so that it did not survive long as a real explanation. A more definite and
thoroughgoing explanation was to be desired. Such an
explanation was provided at the opening of the nineteenth century by Lamarck.
Lamarck has been called the "founder of organic evo23




24  WHERE EVOLUTION AND RELIGION MEET
lution," because he was the first to develop what may
be called a definite, well-organized doctrine; in other
words, a system of belief in reference to evolution.
Lamarck was a Frenchman, the period of his life
extending from 1744 to 1829. He became a leader in
botany, publishing a manual of the flora of France,
which became the standard manual for that country.
Later he became interested in zoology, especially the
fossil mollusks, and it was this study that led him to
his conclusions concerning evolution.
Lamarck offered his explanation at an unfortunate
time for any fair consideration. The dominant French
naturalist at that time was Cuvier, who bitterly and
sarcastically opposed Lamarck's ideas. Cuvier did not
believe in evolution, and as he had the confidence of
the public, Lamarck's attempt to prove the fact of evolution and its explanation made no headway. He was
more than a generation ahead of his time, and hence
his great reputation came long after he was dead.
Thoroughly convinced that evolution was a fact,
Lamarck sought to explain how the evolutionary
(. changes might be taking place. Although the infor# L~ mation at his disposal was very meager, as compared
j with what is now available to biologists, Lamarck
devised an ingenious and logical theory, which has
~Iexerted a profound influence upon biological thought
ever since. This was the theory of use and disuse. In
brief the idea is this. When an animal uses one of its
organs to an unusual degree, that organ is thereby developed; while if the organ is not used at all, it degenerates. Such modifications may be transmitted to the
progeny, thus making it possible for the effects to
accumulate over a number of generations. In this
way an organ may in time become so highly developed, or so completely degenerated, that the animal
possessing it is really of quite a different type or species
from its original ancestors. This constitutes evolution.




LAMARCK'S THEORY OF USE AND DISUSE 25


The best way to explain Lamarck's ideas is by the
use of a concrete example. Using Lamarck's theory,
we may show how one type of animal gradually gives
rise, among its descendants, to a type which is quite
different. If this can be demonstrated in one instance,
presumably it will hold true for other instances as well;
if the theory can explain the evolutionary changes that
have taken place in connection with one organ or character, presumably it can also account for other evolutionary changes. While the example which we shall
use may be open to considerable criticism on the
ground of scientific details, it has the advantage of
dealing with familiar material, and will be quite suitable as an illustration of the workings of Lamarck's
theory.
The proposition is to explain how the giraffe evolved
from a horse-like ancestor, how the long fore-limbs and
neck of the former could have arisen from the short
limbs and neck of the latter. Lamarck accounts for
such a change in the following way. The horse-like
ancestors lived originally in a region composed of
meadows, where their food was provided in the form
of grass and other small herbaceous plants. A certain
group (not all) of these horse-like forms migrated to
another region. This migration might have been a
voluntary "exploration," or it might have been a case
of having been driven from the original district by
certain predatory animals that abounded there. In
any event, a group of horse-like forms came to live in
a new district, and this new district had quite different
characteristics from the old one. It was a dry desert
region, with no grass or other small herbage, and only
an occasional tree. Thus these animals have been
thrown into quite different surroundings from the old.
Their environment has changed, and this change in
environment is to bring very important consequences.
Facing this new environment, the animals find that




26 WHERE EVOLUTION AND RELIGION MEET


their customary source of food is no longer present.
The only available source of forage is the leaves of
occasional trees, and these leaves are rather too high
to be reached conveniently. The animals are starving,
in dire need. Under the circumstances, what they particularly need is to be able to reach up and browse
upon the foliage of the trees above them. Thus the
change in environment has resulted in a new need, a
need which had never been experienced before. The
logical consequence of this new need is the creation of
a new desire in the animals that are experiencing the
need, a desire to reach upward to the only food that is
available. As a result, the animals try to reach the
leaves, they make a conscious effort to stretch upward.
This conscious effort sets in operation those forces
which are to bring about evolution.
Just as the blacksmith by constant exercise develops
a mighty forearm, so the horse-like animals by constantly stretching upward actually lengthen their neck
and fore-limbs. These organs are developed through
use, developed as they had never been developed before, simply because they had never before been exercised in this particular way. Perhaps the animals may,
during their lifetime, increase their height an inch or
two through this special form of exercise. Of course
they are not yet giraffes, but they have taken the
initial step.
At this point Lamarck makes an assumption, an
assumption which seems quite logical on the face of it.
Characters which have been acquired by parents are
passed on to the progeny. The slight gain in height
which has been made by the animals of the first generation is passed on to the animals of the second generation. This is inheritance of acquired characters, and
it is through this that Lamarck explains evolution.
The second generation of horse-like animals, endowed
at the beginning with the slight gain in height which




LAMARCK'S THEORY OF USE AND DISUSE 27


they have inherited from their parents, continue to live
in the same environment. Consequently they are actuated by the same motives as before, and will themselves
stretch upward for forage. As before, this stretching
will result in a slight increase in length of neck and
fore-limbs, but now this increase in height will be
added to the initial increase that had been inherited
from the parents. The acquisitions of the second generation are added to those of the first, and through a
series of generations these modifications are gradually
accumulated. So it is quite clear that, although any
one generation might gain but an inch in height, in the
course of enough generations there will result the fullydeveloped giraffe. The horse-like ancestor has given
rise to the giraffe descendant; an old species has given
rise to a new one; evolution has taken place.
One is struck by the apparently quite logical sequence of cause and effect relationships that appear
in this theory. A changed environment brings a new
need. The animal responds to this new need by a new
desire and a conscious effort to satisfy the desire. The
conscious effort inevitably results in the unusual exercise or use of certain organs, and with this use the
organs are developed. Whatever gain this development brings is passed on to the progeny, who in turn
add a further gain along the same lines. As a result
of this gradual accumulation, a new species sooner or
later results, and thus we have evolution.
It is to be noted that this evolution is always adaptive. The new species is better adapted to cope with
its environment than was the old species; the giraffe
has a better equipment to carry on a successful existence in the desert region than had its horse-like ancestor. It is also evident, however, that what amounts to
an adaptive change in the new desert environment
would not be adaptation in the old meadow environment. In the old environment the horse-like ancestor


A




28 WHERE EVOLUTION AND RELIGION MEET
would doubtless be better adapted than would the
giraffe descendant. Hence we must conclude that not
all the horse-like animals were changed into giraffes,
but only those which were thrown into the desert environment. Where there was but one species before,
there now exist two. Whereas the original group of
animals could successfully occupy only one type of
region, their descendants are now able to spread over
both the meadows and the deserts. Thus evolution
does not (necessarily) result in a supplanting of the
old species by the new, with an extinction of the
former, but results in the multiplication of species,
along with the conquering of new territories.
This illustration of Lamarck's theory shows bow
adaptive evolution may come through the greater development of certain organs, a type of change that
would be called progressive. The theory may also be
employed to explain how adaptive evolution may in
other cases result from the less development or degeneration of certain organs, a type of change which might
be called retrogressive. Lamarck illustrated this type
of case by the evolution of the snake. Snakes are descended from animals that had legs. A certain group
of these animals was thrown into a new environment
where new needs were encountered. In this case it
was necessary, either as a means of flight from dangerous foes or as a means of pursuit of elusive victims, to
creep through narrow crevices. Feeling this need, actuated by the desire to accomplish this, and making a
conscious effort to do so, the ancestral animals spent
their time at the exercise of wriggling through narrow
crevices, and thereby allowed their legs to fall into
disuse. As a result of this disuse, this lack of exercise
of the limbs, those members degenerated somewhat
during the first generation. The second generation
started with the heritage of slightly underdeveloped
limbs. and allowed the limbs to degenerate still further.




LAMARCK'S THEORY OF USE AND DISUSE 29
The final result of this accumulation of effects was the
complete loss of the limbs, the production of the snake.
Lamarck's theory usually appeals to those courageous people who enjoy or approve of personal responsibility, for Lamarck would encourage us to believe
that the fullest development of future generations can
come only through exercising our capacities toward
a better adaptation of ourselves to our environment.
Simply because it provides this inspiring rule of conduct, however, we must not conclude that Lamarck's
theory is necessarily the true explanation or the only
explanation of evolution. Other explanations of evolution likewise provide inspiring rules of conduct, and
perhaps assign a more important mission to those
who cannot have descendants, or can no longer have
descendants.
This was the theory which Lamarck presented in
1801, at a time that his biological colleagues did not
even believe in the fact of evolution. These colleagues,
blindly holding to the old conservative views of special
creation, and doubtless moved by petty jealousies, immediately attacked Lamarck with a storm of ridicule
and abuse. Prejudiced from the start against the new
theory, these other biologists magnified every little flaw
in the illustrations which Lamarck used, and refused
to recognize the real truth and value which lay in
Lamarck's basic propositions. This wholesale antagonism practically ruined Lamarck's influence in the biological world, and he died in obscurity. It was a later
generation that appreciated his work.
As a matter of fact, there were two big difficulties
with Lamarck's theory. In the first place, Lamarcli
laid what was really unnecessary stress on the operation of conscious effort as a necessary part of his theory.
This was unfortunate, since biologists refuse to recognize the possibility of conscious effort in plants and
in primitive animals. Automatically then Lamarck's




30   WHERE EVOLUTION AND RELIGION MEET
theory becomes restricted to accounting for evolution
only among higher animals. A modification of the
theory is necessary before the other cases can be
included.
The other objection to Lamarck's theory is a much
more serious one. It is quite essential to the theory
that acquired characters be inherited. Otherwise there
could be no further progress than the slight gain made
during a single generation, and this would not be sufficient to bring any substantial evolutionary advance.
It is clear, therefore, that Lamarck's theory provides
an explanation of evolution only if inheritance of acquired characters can take place. As a matter of fact,
during the century following Lamarck, the most reliable evidence that was collected on this point seemed
to indicate clearly that inheritance of acquired characters never takes place. For this reason the theory
was discarded by most biologists. Recently Lamarck's
theory has been revived in a modified form, as will be
described in a later chapter.
In spite of the poor success of Lamarck's theory, he
must be given credit for having presented the first
comprehensive theory on evolution. His theory failed
as an explanation because it could not meet the two
critical objections that have been mentioned. It remains to be seen whether these objections can be met
any more satisfactorily by the later theories.




IV


DARWIN'S THEORY OF NATURAL SELECTION
THERE is no more famous name in the history of
biology than that of Charles Darwin. He was born in
1809, sixty-five years after the birth of Lamarck, and
died in 1882. He was born at Shrewsbury, England,
studied for a short time at Edinburgh University, and
then went to Cambridge, where he graduated in 1831.
At that time Professor Henslow, a distinguished botanist, was at Cambridge, and he stimulated the interest
of young Darwin in the world of life. Through the
influence of Professor Henslow, Darwin was appointed
naturalist of the famous British expedition around the
world, in the ship Beagle. This expedition started in
1831 and returned in 1836, much of the time being
spent in South America and the adjacent islands. It
was his world-wide observations during the five years
of this expedition that sowed the seeds of Darwin's
ideas concerning evolution. The long voyage ruined
his health, and during the rest of his life he could work
only a limited amount each day, living in seclusion at
his country place at Down.
For over twenty years Darwin worked at his explanation of evolution, and in 1858 he received from his
friend Alfred Wallace, who was then traveling in the
East Indies, a manuscript containing exactly the theory
he had worked out. With characteristic generosity,
Darwin decided to abandon his work, and give precedence to Wallace's paper. Fortunately, however,
certain of Darwin's scientific friends, who knew of his
31




32 WHERE EVOLUTION AND RELIGION MEET
work, urged him to present his own results along with
those of Wallace at the same meeting of the Linnean
Society in 1858. These two papers, therefore, were
read at the same meeting, and when Wallace learned
of the situation, he withdrew from the field, recognizing Darwin's prior claims on account of his many years
of work. It was in 1859 that a full account of Darwin's
explanation was published in his "Origin of Species,"
and it at once aroused the greatest interest, not only
because it came at a "psychological moment" to attract
attention, but also because of the extraordinarily able
championship of Huxley.
C Darwin makes three distinct contributions to the
cause of evolution and to biological science in general.
In the first place, his work exemplifies the perfection
of a certain method of research, the method of observa-,tion and inerence. Darwin s obv     ations were about
as exteiive- -i —space as would have been possible,
covering practically the whole globe; in time they were
likewise quite as extensive as could reasonably have
been demanded, for Darwin studied his problem intensively for 20 years before publishing his conclusions.
In the matter of thoroughness, his methods leave
nothing to be desired. The account of his years of
conscientious investigation furnishes a much-needed
stimulus and a warning to other investigators who are
in danger of carrying on hasty and hence unreliable
research.
Darwinr's second contribution was his greatest one,
and the one for which he has become deservedly
famous. He was the first author who was successful
in carrying the evolution idea before the general public. This was not accomplished through Darwin's
direct influence, for in his own writings he did not
really address the general public. Darwin's writings,
however, were received with great enthusiasm by a
number of very influential biologists, and it was these




DARWIN'S THEORY OF NATURAL SELECTION 33


men who preached the doctrine of evolution very
widely before general audiences. Under the circumstances it is not surprising that the public got the impression that Darwin was the author of the idea of
evolution. This is strictly untrue, for Lamarck and
many others had recognized the fact of evolution before Darwin's time, as Darwin himself clearly acknowledges. But although Darwin cannot justly be credited
with authorship of the idea, he is at least the one who
was primarily responsible for spreading the idea. That
in itself was a great service, for it brought substantial
benefits to many lines of human thought, as we shall
see later.
In this connection it should be pointed out that
Darwin was a great deal more fortunate than Lamarck.
Lamarck attempted to present the evolution idea at
a time when the public was not ready to receive it;
hence the enterprise was a failure. By Darwin's time,
however, sufficient progress had been made in human
thought, that the world was ready for the evolution
idea; since he presented evolution at this psychological
moment, the scientific public received it with great
favor.
Darwin's third contribution was the theory of Natural Selection, by means of which he attempted to
explain evolution. How successful an explanation this
proved to be we shall see later, but it must at all times
be kept clearly in mind that any objections to Darwin's theory are not objections to the fact of evolution.
As has been said, every explanation of evolution that
has ever been proposed may prove unsatisfactory, but
the fact of evolution will still remain to be explained.
As we present Darwin's theory of Natural Selection,
we should consider whether it is successful in overcoming the two serious objections that were raised
to Lamarck's theory. In other words, we should see
whether Darwin explains evolution without requiring




34 WHERE EVOLUTION AND RELIGION MEET


conscious effort or the inheritance of acquired characters.
At the basis of Darwin's theory lies the tendency
to a geometrical ratio of increase that is present in all
plants and animals. If the human race were to breed
at the fairly conservative rate of 4 children per family
and a generation every 25 years, if all the children
themselves survived and had families, and if death by
accident, disease, or starvation were eliminated, the
descendants from a single pair at the end of a thousand
years would amount to a million million individuals.
Most plants and animals have a much higher rate of
increase than this, for the generations are short and a
great number of progeny is produced each generation.
A famous example is provided by the rotifers, animals
so tiny as to be barely visible to the naked eye. If
these animals were allowed to breed at.the normal rate
and it were possible to rear all of the progeny, a single
pair would produce within a year "a solid sphere of
organic matter with a radius greater than the probable
limits of the known universe." It is quite obvious that
these expectations are never realized, and the reason
is that death by accident, disease, and starvation is
constantly taking place to check this prodigious rate
of increase.
The bearing of this phenomenon on Darwin's theory
becomes evident from the following considerations. In
a certain meadow there are growing a thousand plants
of a certain kind. Each plant produces one hundred
seeds. Each seed has the power of producing a young
plant the next season. On this basis we might expect
to find 100,000 plants occupying the meadow during
the following year. Now there is good reason to believe that each of the 100,000 seeds starts to produce
a young plantlet at the beginning of the year, but
by the end of the season we find that only about a
thousand mature plants are present, approximately the




DARWIN'S THEORY OF NATURAL SELECTION 35
same number as the year before. Why? Because in
that locality there is only enough room and means of
subsistence to support a thousand plants of that kind.
Out of the hundred thousand young plants that started
the season, 99,000 have perished through accident, disease, or starvation. "Death is the rule, life the exception." There is an equilibrium of species, approximately the same number of individuals of a species
being present in a given locality year after year.
How can this phenomenon operate to bring about
evolution? Darwin interprets the situation as follows.
If we are to consider any group of individuals of the
same species we find that no two of them are exactly
alike. We immediately recognize that this proposition
is true of the human race. Out of the many thousands
of men that we have encountered during our experience, we have never found any two that were absolutely identical, indistinguishable. Even twins can
always be distinguished after critical examination.
What is true of men is also true of plants and animals,
although we may not at first recognize it. It would be
impossible to find two oak trees or two cats that would
be indistinguishable upon careful examination. In
other words, in all living organisms there is variation
such that no two individuals are ever exactly alike.
Since this is true, it means that the hundred thousand
young plants that we were considering were all somewhat different with respect to one character or another.
One thousand out of the total hundred thousand survives. Which thousand is this to be? Will the matter
be decided entirely by chance? To a certain degree,
but not entirely. If one hundred plants start to grow
where there is only enough space or food available for
one of them to mature, it is evident that a sort of a
competition will be set up among these one hundred
individuals, a struggle for existence, in which one indi



36 WHERE EVOLUTION AND RELIGION MEET


vidual will succeed while the rest perish. Under the
circumstances, which one of the hundred will be the
one to survive? If all the hundred individuals are
identical, it will be a matter of chance which one survives. But we know that they are all slightly different
with respect to one characteristic or another. One of
them might be endowed with the ability to grow a little
faster than the others. It would then get a better start
than its competitors, raise its head above the rest, and
hence get a fuller exposure to light, which is essential
to plant growth. Having this decided advantage, the
fortunate plant would continue to thrive, and, by casting its shade over the others, would eventually crowd
them out. Again, one of the plants might differ from
the rest by having slightly longer and more vigorous
roots. It would then get from the soil more of the
water and salts which are essential to plant growth,
and, developing a stronger growth than its competitors,
would be the successful one of the hundred. Whenever competition is set up in this way, it is the stronger
individual that is successful, while the weaker ones
perish. The successful individual is the one which
happens to be a little better adapted to its environment than are the others. As Darwin puts it, there is
a "survival of the fittest," a natural selection of those
that are the best equipped to meet their living conditions, with an elimination of the others. It is this
inevitable natural phenomenon that brings about evolution.
The exact workings of the Darwinian principles in
the production of a new species from an old may be
illustrated by the same imaginary case that was used
before to illustrate Lamarck's theory. Let us see how
the Darwinian theory can account for the origin of the
giraffe from a horse-like ancestor by means of the principle of natural selection, without calling upon any of
the conscious effort or inheritance of acquired char



DARWIN'S THEORY OF NATURAL SELECTION 37
acters which proved to be the objectionable points in
Lamarck's theory. To make the same start as in the
other case, a group of the horse-like animals is thrown
into a new, desert environment where the only substantial forage is provided by the foliage of trees.
Although these animals all belong to the same species,
there occur slight individual variations with respect
to practically all their characteristics. The particular
characteristic that is significant in the present connection is the matter of height. A few of the animals
have slightly longer necks and fore-limbs than have
the others. Food is limited; only the lowest branches
of the trees are within the reach of any of the animals.
The tallest of the animals are successful in reaching
this food, while the others starve to death.
Since the tallest animals are the only ones to survive,
it follows that they are the only ones to reproduce.
As a result, all of the animals of the second generation
are the progeny of parents that were slightly taller
than the average of the species. To put the matter in
exact terms, let us say that the average height of the
first generation was six feet, but that some of the
animals were as tall as six feet two inches, Iwhile some
of the others were only five feet ten. it was the individuals of the former group that survived and reproduced. The individuals of the second generation were,
therefore, the descendants of six-foot two-inch parents.
What then will be the average height of the second
generation? Is it not reasonable to suppose that that
average height will be six feet two? Is it not a matter
of common experience that the slight peculiarities that
distinguish any given parents from the general mass, of
the population will be passed on to their progeny?
Surely Darwin is quite justified in concluding that the
animals of the second generation will show an average
height of six feet two inches.
This further conclusion also seems entirely justified.




38 WHERE EVOLUTION AND RELIGION MEET,Just as the individuals of the first generation varied in
height around an average of an even six f eet, so it
follows that the individuals of the second generation
willI vary in height around an average of six feet two;
that is to say, some of them will be as tall as six feet
four, while others will be only an even six feet.
These are the characteristics of the population of the
second generation, a population which now proceeds
to face the same conditions and to enter into the same
sort of a competition or struggle for existence as did
the parents. Still the food is limited, and the taller
ones have a decided advantage over the others in procuring it. As before it is the tallest group, the six-foot
four individuals, that is successful in the struggle, while
the rest perish. It follows that the individuals of the
third generation, since they are the descendants of
parents that were six feet four in height, will vary
around the average height of six feet four, some of
them being six feet six, while others are only six feet
two. Generation after generation the same forces operate. The average height of the species gradually increases, because it is always the tallest individuals that
have an advantage in the struggle for existence. Eventually the characteristic height of the giraffe is attained
and a new species may be said to have been evolved.
The same evolutionary result has been obtained as
under Lamarck's theory, but without the operation of
conscious effort or the inheritance of acquired characters.
To summarize: The capacity for geometrical ratio
of increase, which appears in all living organisms, tends
to bring into the world a greatly increased number of
individuals with each generation. Since there is not
enough space or enough food to go around, there results
a competition or struggle for existence among the individuals. One of the results of this struggle for existence is to kill off all but a fortunate few, and thus




DARWIN'S THEORY OF NATURAL SELECTION 39


maintain a constant number of individuals, an equilibrium of species, generation after generation. Under
special circumstances there may be exceptions to this,
but the exceptional situations are, at best, only temporary, and do not affect the adequacy of Darwin's
theory. The other result of the struggle for existence
arises from the fact that there are never any two individuals which are quite identical, there is always variation. Hence, in this varying group of competing
individuals, it is the fittest that survive, those which
are the best adapted to their environmental conditions.
It is these individuals that produce the next generation. The average fitness of the next generation is
the same as that of the parents, but some few of the
progeny are even more fit than were the parents. Again
it is this group of the most fit that survives, so that
there is a continuous though gradual gain as the generations go on. Eventually enough change has been
made to bring into existence a new species.
Not only in the case used as an illustration, but in
practically all other cases as well, the Darwinian theory
can be used just as successfully to explain evolutionary
change as can the Lamarckian. As before, we find that
the evolutionary machinery operates to produce a type
of animal (or plant) which is better adapted to the
environment than was the ancestral type. And, as
before, it is clear that the same change which means a
more perfect adaptation in one set of environmental
conditions would not be a more perfect adaptation
under another set of environmental conditions. The
general result is to produce two species where but one
existed before, and to increase the territory that may
be occupied.
There is a very impressive type of evidence which
has been used as confirmation of Darwin's theory, and
at the same time may be used to illustrate how adaptation to one set of conditions is not successful adapta



40 WHERE EVOLUTION AND RELIGION MEET
tion to another set of conditions. Nature has not been
the only agent to bring about evolutionary change
through a constant selection of better adapted individuals. Man himself has acted in this same capacity,
and with considerable success. For many centuries
man has been carrying on selection with his cultivated
plants and domesticated animals. This selection has
perhaps been even more rapid in producing evolutionary change than natural selection, for here it is even
more certain that it will always be the best adapted
individuals that will be the progenitors of the next
generation. The great difference lies in the basis of
selection. Nature always selects those individuals
which are the best adapted to the environment when
grown in the wild, under natural conditions, while man
always selects those individuals which are the best
adapted to his own needs when grown under conditions
of artificial cultivation. Starting with a given type of
plant, nature would be likely to produce by her selection a type that could live successfully in poor, dry
soil, but would not produce a great weight of seed or
fruit. Starting with the same type of plant, man would
produce by his selection a type which would bear a
great weight of seed or fruit, but which would be
adapted to living only in the fertile, irrigated soil
which he provided for it. Starting with a given type
of animal, nature would be likely to produce a type
which could run and fight, but did not develop a great
weight of meat on its bones. With the same start, man
would develop a heavy, sluggish variety that would be
very poorly adapted to running or fighting. In almost
every case the adaptation to man's needs is quite different from adaptation to nature's demands. Furthermore, if man were to allow some of his cultivated plants
or domesticated animals to return and live under natural conditions, these forms would prove very poorly
adapted to life in the wild and might perish entirely.




DARWIN'S THEORY OF NATURAL SELECTION 41
If, however, the competition did not prove too severe,
a few individuals might survive, and, from this start,
nature would then gradually erase the effects of man's
selection and substitute those of her own.
The contrast between Lamarck's theory and Darwin's should be quite evident. There is likewise a contrast with respect to the recommendations for human
conduct. In this respect, the recommendation that is
provided by Darwin's theory is a more "dangerous"
and perhaps a more distasteful one, but if it represents
the truth, we should not hesitate to accept it. According to Darwin, there must exist in any human population some individuals that are better adapted to their
environment than are others. If then the human race
is to improve in future generations it is these individuals that should be the most successful in reproducing their kind. How can this be brought about?
In the first place, some agreement should be reached
as to what constitutes the most perfect adaptation to
the human environment. It is very doubtful whether
we should ever be able to reach anything like a perfect
agreement on this matter, but a certain amount of
agreement could surely be attained, and even that
would provide a basis for considerable progress. Again,
it is reasonable to expect that perfect adaptation under
certain social conditions (human environment) might
be imperfect adaptation under others; but here, too, it
should be possible to visualize certain common features
in the adaptation to practically all human conditions,
and this much would provide a safe basis for procedure.
The authors of the present text will not attempt anything like an exact analysis of what constitutes perfect
adaptation to human environment, for that is a stupendous problem which the great thinkers of all ages
have attacked directly or indirectly. All that we attempt to do is to focus the attention of the reader on




42 WHERE EVOLUTION AND RELIGION MEET


the problem, so that he himself may do more effective
thinking along these lines.
It is quite apparent that where mankind lives in the
savage state features of adaptation are markedly different from those that would hold for a civilized community. In the savage a premium would be put upon
brute strength, while in civilized man the premium
would be put upon intellect. But the problem is a
great deal more complicated than that. We might go
on to say that the perfectly adapted man under conditions of modern civilization is not only intelligent,
but is healthy, energetic, industrious, cooperative, and
endowed with a sense of justice. Surely it should be
one of our big aims for the future to achieve a society
in which as many as possible of the men and women
are endowed with these traits.
But how is this to be achieved? If we take our
recommendation from Darwin's theory, it amounts to
this. The men and women with these fine traits should
be more successful in reproducing their kind than are
the others. To a certain extent this matter takes
care of itself, and under many conditions an inevitable
progress is made. It seems inevitable that in general
the men and women who are unintelligent, unhealthy,
sluggish, lazy, blindly selfish, and unfair will make a
failure of life and will be less successful in reproducing
their kind than are those with the opposite traits.
Under certain conditions, however, this plan of
things is seriously impaired. During war it is likely
that the best blood is killed off. In any vicious aristocracy, either political or economic, the most desirable
types of men and women are often not allowed to survive and reproduce. Without going into the matter
any further at this point, we can at least be safe in
concluding that when society is conducted so as to
give all individuals a fair opportunity to express those
desirable traits with which they may be endowed, the




DARWIN'S THEORY OF NATURAL SELECTION 43


greatest progress in human selection will result. Let
competition continue, but let that competition be as
fair as possible, lest the benefits be impaired and the
results seriously distorted.
It should be clear that there is nothing brutal contemplated in this program. Nothing could be more
unwise than actively to enforce the code of "survival
of the fittest," and ruthlessly to eliminate all that fall
below some rigid artificial standard of perfection. Quite
the opposite methods are called for in the proper application of Darwinian principles to man. Every man
must be given a fair opportunity to express his capacities, and the stress is to be laid, not upon elimination
of the unfit, but upon preservation of the fit.
This theory of Darwin's took the scientific world by
storm, and was rather generally accepted during the
four decades following its publication. Not only in
biology but in many other lines of human thought as
well it exerted a profound influence. Naturally there
were many objections raised to the theory. Two of
these objections will be worth while considering at this
point.
In the first place, it was pointed out that there are
two general types of evolutionary changes that must be
accounted for: quantitative changes, or mere changes
in the degree of development of certain existing structures; and qualitative changes, or radical changes in
type, involving the production of brand-new structures. It was admitted that the natural selection
theory could explain the quantitative changes, but it
was claimed that this theory could not explain the
qualitative changes.
In the example that was considered, the difference
between the giraffe and its horse-like ancestor was
quantitative. It was a difference in the length of neck
and fore-limbs, that is, a mere difference in the degree
of development of structures possessed by both types




44 WHERE EVOLUTION AND RELIGION MEET
of animal. Natural selection explained this change,
but the explanation depended upon the fact that there
was some variation in the horse-like ancestor to begin
with, a few of the animals being slightly taller than the
rest. If, in the ancestral form, there had been no such
variation in the direction of greater height, if, in other
words, every one of the horse-like ancestors had been
exactly six feet high, natural selection would never
have been able even to make a start toward the production of the giraffe.
Consider now what is involved in a qualitative
change. A certain ancestral organism has no hair
whatsoever. One of the types which has descended
from this ancestor possesses hair. How can natural
selection explain this evolutionary change? It would,
of course, be easy enough to explain how a long-haired
form had been developed from a short-haired ancestor,
for this would be merely a quantitative change in existing structures. But if the ancestor has no hair whatsoever, and the descendant possesses hair, this involves
a qualitative change, the production of a brand-new
structure which did not exist before. In such a case
natural selection cannot even make a start. It was
concluded, therefore, that, although the natural selection theory might explain quantitative evolutionary
changes, it failed to explain the many qualitative evolutionary changes that must have taken place in the
past.
This first objection would merely limit the scope of
the natural selection theory; the second objection was
more serious. It was claimed that in actual practice
the gradual cumulative gains brought about by selection always reached a definite stopping point beyond
which further gain was impossible. It was felt that
this stopping point was the species boundary, so that
although natural selection might pull the species up
to its maximum development with respect to any char



DARWIN'S THEORY OF NATURAL SELECTION 45


acter, it would never be successful in taking that final
critical step into the next species. For example, natural selection might change the horse-like ancestors
of the giraffe from six feet in height up to seven feet,
but no further gain could be made. The seven-foot
animals would have among their progeny none that
were any taller than seven feet, so that it would be
impossible for natural selection to carry the gain in
height any further than this. In this case then, natural
selection would serve to produce a rather tall variety
of horse, but it would be unsuccessful in producing the
giraffe. This objection was based in part upon actual
experiments that had been performed, in which it was
found that there was this definite limit to the gains
that could be made by selection.
Although Darwin's theory was successful in overcoming the objections that had been raised to Lamarck's
theory, there still remained, therefore, two critical objections that had not been overcome. We shall see
whether any subsequent theory was successful in escaping these two objections, (1) that only quantitative
changes could be accounted for, and not qualitative,
(2) and that the gradual progress that was made by
selection was not successful in taking the critical step
from one species to the next, that is, could not cross
the species boundary. It should be pointed out that
these two objections in no wise serve to prove that'
a struggle for existence and natural selection do not
actually take place. These phenomena are recognized
as established facts. It merely becomes doubtful
whether these forces can account for all the evolution
that has taken place in the past without the assistance
of still other critical forces that Darwin had failed to
recognize. The reader should further be reminded that
this doubt that was cast upon Darwinism was directed
merely at the adequacy of Darwin's explanation of evolution, and not at the fact of evolution itself.




V


THE MUTATION THEORY OF DE VRIES
THE explanation of evolution proposed by De Vries
introduced the modern period in the study of evolution. The preceding period, which may be called the
mediheval period, culminated in the work of Darwin.
During that period, the method used was observation
and inference. Darwin carried this method to the limit
of its possibilities, both in space and time, making observations throughout the world, and studying rational
conclusions for more than twenty years before publication. Inference from observations, however, is not
demonstration. Any further progress in the study
of evolution demanded a new method, and this was
introduced by De Vries. It is the method of experimentation. Instead of observing the resemblances and
differences of plants, for example, and inferring relationship, plants were made to reproduce under control to see whether new species are actually produced.
If by this method a new species is observed to come
from an old one, the result is not an inference, but a
demonstration.
Hugo De Vries was born at Haarlem, Holland, in
1848, and is still actively at work with his investigations. He studied at the universities of Leyden, Heidelberg, and Wurzburg, receiving the best training in
biological technique that was possible at that time.
He became professor of plant anatomy and physiology
at the University of Amsterdam, and published the
results of some important investigations on the structure of plant cells.
His call to the subject of evolution came in an unexpected way. He was botanizing in an area in Hol46




THE MUTATION THEORY OF DE VRIES         47
land where native vegetation was still present. Among
the plants he was observing, he discovered an introduced plant growing abundantly, a primrose, afterwards found to be a native of the United States. As
he examined these immigrant primroses, he found an
individual here and there very different from the
majority, but still a primrose. He began to suspect
that these occasional individuals might have come
from the ordinary forms; if so, here was one species
producing another one.
He took specimens of the primrose to his Botanical
Garden and began a series of experiments, to see
whether the common form occasionally produced an
entirely different one. The method used is known as
pedigree culture, the pedigrees of the different individuals being carefully recorded. This was continued
for thirteen years, and by that time De Vries had the
exact records of the pedigree of every primrose in his
garden, running back through many generations. As
a result, he found that now and then an entirely new
kind of individual would suddenly appear in a pedigree. Upon the basis of this work, De Vries announced the theory of "mutation" as an explanation
of evolution.
The explanation of evolution which is offered by
De Vries is very similar to that of Darwin's. In fact
there is really only one feature in which the two
theories differ, but that feature is of critical importance. The importance of this difference may be
realized when we recall the objections that were raised
to Darwin's theory, and notice how De Vries, by making this one critical change in the theory, was successful in overcoming these objections.
In criticism of Darwin's theory, it was urged that:
(1) although quantitative changes, or changes in the
degree of development of some preexisting organ or
character, might be brought about by naturfl selection




48 WHERE EVOLUTION AND RELIGION MEET
in the way that Darwin had outlined, evidently a great
part of the evolution that has taken place in the past
must have consisted of qualitative changes, or the
actual appearance of certain new organs and characters
where nothing of the sort had existed before; and Darwin's theory seemed quite inadequate as an explanation of changes of this latter sort; (2) experience in
breeding has strongly suggested that, although selection may be effective in the gradual accumulation of
the effects of small variations up to a certain point,
this critical point, the species boundary, can never be
passed, so that it is really impossible to produce a new
species from an old one. These were two important
objections to the Darwinian theory; it is interesting
to see how De Vries is successful in escaping these
objections.
De Vries recognizes the truth in Darwin's statement
that there are never any two individuals that are
absolutely alike. He acknowledges that these small
individual variations always occur; but he maintains
that it is not the little variations of this sort that are
important in providing a basis for explaining evolution. In addition to these small, quantitative variations that are always taking place, De Vries points out
that there will occasionally occur variations of quite a
different sort. Occasionally there will appear in a
population of animals or plants one or a few individuals which are quite different from all the rest.
They differ not merely in having some organ or character slightly more or slightly less developed, but in
possessing some character that the others lack, or in
lacking some character that the others possess. De
Vries presented considerable evidence to prove that
radical variations of this sort occasionally take place,
and other investigators have also observed many instances of this phenomenon. For example, in a population of fruit flies which normally have red eyes there




THE MUTATION THEORY OF DE VRIES


49


may suddenly appear one individual which has absolutely white eyes; in a group of corn plants of normal
size there may appear a few individuals that are
absolute dwarfs, being less than a foot in height even
when grown in rich soil; a herd of normal cattle may
possess one animal which is without horns; in a field of
American evening primroses there may appear a few
plants that are giants, having a much greater size in all
of their parts than the other plants. It can be seen
at once that these variations are of quite a different
sort from the small, quantitative, individual differences that Darwin used in his theory.
These conspicuous, qualitative variations are called
mutations, and, according to De Vries, it is mutations
which lie at the basis of evolution. Otherwise his
theory agrees entirely with Darwin's. De Vries also
believes that natural selection operates to bring about
a survival of the fittest, with an elimination of the
unfit. The one difference between the two theories is
that Darwin used the small, quantitative, individual
variations which are constantly occurring, while De
Vries uses the abrupt, qualitative variations which appear only occasionally. This one fundamental difference between the theories, however, carries with it
many important consequences.
According to De Vries, there occurs the same competition or struggle for existence, and natural selection
comes into play to bring about the survival of the
fittest, just as in Darwin's theory; but the natural
selection (so far as it is effective in bringing about
evolution) takes place among the mutations rather
than among the small, quantitative variations. As
Darwin pictures it, natural selection, by leading along
the small, quantitative variations in a given direction,
and gradually accumulating these effects, finally, after
the lapse of a great many generations, results in
enough change to produce a new species. De Vries,




50 WHERE EVOLUTION AND RELIGION MEET


on the other hand, maintains that new species will
occasionally appear very suddenly and spontaneously
(the cause being unknown) in the form of mutations,
and that natural selection will merely decide which of
these mutations is fit to survive.
In this connection a word should be said as to the
occurrence of mutations and the possible fate which
awaits them. A given species of plant or animal may
go along for a number of generations without showing
any mutations at all (merely showing the small, quantitative variations of the Darwinian type, which, according to De Vries, will lead to no real evolutionary
results). Then, among the progeny of one generation,
there may suddenly appear one or a few individuals
which are the result of mutation, and which differ
radically from all the others. After that the species
may again continue for a number of generations without having any mutations, but sooner or later it will
again produce among its normal progeny a small group
of mutated forms. So it is that, although mutations
are infrequent, in the course of enough generations a
given species may show quite a number of them.
There is never any way of knowing when the next
mutation may take place or what it may amount to.
The change may affect any part of the organism, and
may modify that part in almost any conceivable way.
Furthermore, it should be realized clearly that the
changes produced by mutation are not necessarily
adaptive; that is, they do not necessarily serve to provide the plant or animal with any better equipment
for coping with its environment. The changes are
fortuitous, a matter of chance. Some may happen to be
useful, but others may be useless or even harmful. In
this respect, mutations are similar to the small, quantitative variations of Darwin. If the change produced
by mutation happens to be useful, if it serves to adapt
the plant or animal to its environment better than




THE MUTATION THEORY OF DE VRIES 51
before, then the mutants (individual plants or animals
produced by mutation) will have an advantage over
the others in the struggle for existence, and will be
likely to survive while the others perish. If the change
is useless, if it neither helps nor hinders the organism
in any appreciable way, the mutants will have no advantage over the others, and whether or not they survive will be decided by chance. If the change is
actually harmful, being a distinct disadvantage to the
organism in its attempt to adjust itself to environmental conditions, then the mutants will be at a disadvantage in the struggle for existence, and will perish
while others survive.
De Vries believed, and presented evidence to support
his belief, that mutations of these various types would
occasionally take place in all species of plants and
animals. Natural selection would then proceed to
"judge" the mutants, and, if they were better adapted
than their parents, they would survive, multiply themselves, and eventually crowd out the parental type.
From the start, the mutants would be sufficiently different to be regarded as a new species. In this case,
therefore, natural selection does not operate gradually
to build up new species, but merely decides which,
among the many new species spontaneously produced
by mutation, are to survive and therefore be effective
in bringing about evolution.
It should be rather apparent that this mutation
theory of De Vries' escapes the two objections that
were raised to Darwin's explanation of evolution. In
the first place, the objection that only quantitative
changes can be explained is not applicable here. Mutations involve qualitative changes, adding to the
organism new characters that were not present before,
or eliminating old characters. It should not be concluded that mutation is ineffective in bringing quantitative changes, for these also may occur.




52 WHERE EVOLUTION AND RELIGION MEET


In the second place, an objection that was raised
to Darwin's theory was that the accumulation of the
effects of the small, quantitative changes would never
be effective in passing the species boundary. This
objection cannot be applied to De Vries' theory. The
mutations are really new species from the moment
they appear. It is not at all the task of natural selection to bring about an accumulation of the effects of
these changes, but merely to decide which of the many
prospective new species shall survive and actually become established as a species in nature. It is evident,
therefore, that the mutation theory of De Vries escapes
the objections that were raised against the Darwinian
theory.
It will be worth while again to emphasize this fact.
Although the Darwinian explanation of evolution has
thus become somewhat discredited and supplanted by
what seems a more accurate theory, it should be remembered that what was really Darwin's main idea,
the idea of natural selection, is still believed to be
accurate. In fact it may safely be stated that (with
a few exceptions, which will at best be only temporary), a competition or struggle for existence of one
sort or another is bound to take place; and whenever
this struggle for existence takes place, natural selection, through the survival of the fittest, will follow as a
consequence just as inevitable as the law of gravitation.
If one seeks in De Vries' mutation theory a recommendation for human conduct, he finds one which is
essentially the same as that provided by Darwin's
theory, for the final evolutionary consequences are
brought about by natural selection in each case. As
before, we find that the evolutionary possibilities with
respect to man are, to a great extent, in the hands of
man himself. In this vast human population of ours
we are forced to believe that there must be occurring
from time to time a few mutations. What these mu



THE MUTATION THEORY OF DE VRIES 53
tations will amount to can never be predicted. Many
of the mutations will doubtless bring into existence
individuals who are really more poorly adapted to
their human environment than are most persons. What
shall be done with these? If the abnormality or defect
that is introduced by mutation is not a very serious
one, then the prospect need not concern us deeply.
If, for example, only some minor anatomical defect
is produced, such as a condition where the individual
has very short fingers and toes, we have no reason
to worry very much about the situation. Short fingers
and toes are, of course, clearly a defect. The individual
possessing them is somewhat more poorly adapted to
his environment, has a rather faulty equipment with
which to cope with the demands of life, as compared
with the mass of normal individuals that surrounds
him. The defect, however, is really not serious, and
there are in existence more than enough serious defects
to occupy our concern.
If, however, the defect that is introduced by mutation is of a more serious character, a social danger at
once confronts us; we are presented with an important
problem which should be solved. If, for example, mutation should result in a mental defect which brought
feeble-mindedness and serious criminalistic tendencies,
the individual possessing these traits would be a
burden and a menace to society. In such a case there
is no necessity, and no real justice, in the punishment
of this unfortunate individual with the death penalty;
but it is clear that it should be made impossible for
such an individual to reproduce and thus multiply the
defect.
On the other hand, we must conclude that there
will occasionally take place mutations which result in
somewhat superior individuals. This superiority might
be physical, such as greater strength, or resistance, or
improved powers of coordination, or it might be




54   WHERE EVOLUTION AND RELIGION MEET
mental. Since the most desirable and promising prospect in human evolution lies in the improvement of
mentality, it should be our particular concern to make
the most of any mutations that tend in this direction.
Individuals of superior mental capacity (provided this
be not associated with any vicious tendencies) should
be given a full opportunity to express their capacities,
so that society in general shall enjoy the benefits thereof; and, above all, such individuals should be allowed
and even encouraged to reproduce, so that their desirable traits will be multiplied in future generations.
Progress in human evolution along the general lines
just indicated is certain to take place wherever the
political, economic, and educational systems are sound.
Either under an intelligent democracy or a benevolent
autocracy superior individuals have the right of opportunity for self-expression and propagation. The right
economic situation is one which makes it readily possible for any really capable individual to attain a
comfortable though not extravagant and luxurious
standard of living. The right educational system is
one that puts a higher education within the reach of
every individual who gives good evidence of his ability.
One is comforted and encouraged by the thought that
in these matters the world as a whole is much better
off today than ever before (save for a few distressing
local situations which should be speedily improved).
There is always room, however, for improvement in
the details of the political, economic, and educational
systems, and there will always be ample benefits received from such improvements through the proper
direction of human evolution.
The mutation theory of De Vries is the third and
last of the "classic" explanations of evolution. This
is the theory that was rather generally accepted by
biologists at the beginning of the twentieth century.
The exact present status of this and the other theories
will be discussed in a later chapter.




VI


SOME OTHER THEORIES OF EVOLUTION
THE theories of Lamarck, Darwin, and De Vries may
be regarded as the three "classic" explanations of
evolution. Each one was, at the time of its presentation, more satisfactory in fitting the known facts than
any other contemporary explanation; each one provided what was presumably a thoroughgoing interpretation of all the evolutionary events that had taken
place in the past. It is these three explanations, therefore, that have during the past century exerted the
greatest influence on biological thought.
It has been seen how Lamarck's theory was rather
supplanted by Darwin's because the latter was successful in avoiding certain critical objections that had
been raised against the former. In a similar way Darwin's theory was supplanted by that of De Vries. It
should be understood, however, that when we speak
of one theory "supplanting" another, we mean nothing
further than this, that it is accepted by the majority
of those biologists who are in the best position to pass
critical judgment. It is not true that scientists were
unanimous in discarding Lamarck's theory at the time
that Darwin's was published; quite a number maintained very stoutly their belief in Lamarckism in spite
of the seemingly fatal objections that were raised
against it. Likewise there are some who today maintain that Darwin's theory is a more satisfactory explanation of evolution than is that of De Vries. These
differences of opinion among biologists are to be ac55




56 WHERE EVOLUTION AND RELIGION MEET
counted for by the fact that some, in the course of
their own investigations, encounter repeated and impressive instances of one type of evidence only, while
others are encountering another type of evidence.
Since conclusions are reached through a critical weighing of different types of evidence, it is not surprising
that there should be some difference of opinion on
such matters. We are rather safe in stating, however,
that during the last two decades the mutation theory
of De Vries has been the one favored by a majority
of the authorities.
In addition to these three "classic" theories, there
have been proposed numerous other explanations of
the evolutionary process. Most of these others have
proved worthless, either because they were based upon
wild speculation without adequate foundation in fact,
or because they contained some obvious fallacy. There
are three of these others, however, that are worthy of
mention. None of them is quite satisfactory as a
complete explanation of evolution, but each contains
points which have a real bearing upon the problems
of evolution. All of them were proposed during the
latter part of the nineteenth century.
ORTHOGENESIS THEORY
Practically all biologists recognize that there must
have occurred from time to time "determinate" variations, variations along apparently predetermined lines.
Some unknown internal force causes a plant or animal
to change in a certain way. Generations later, among
the progeny of this individual there will take place a
further change in the same direction, and later even
more changes will take place along this same "predetermined" line. These changes are in no way (so
far as we can see) determined by the effects of natural
selection or any environmental influence, but seem to
be regulated entirely by some unknown power that is




SOME OTHER THEORIES OF EVOLUTION 57


internal in the organism. This rather mysterious
phenomenon is referred to as "orthogenesis."
Most of the evidence for orthogenesis is provided by
the geological record. If we examine the fossil forms
of some group of plants or animals that lived during
a certain geologic age, and then compare these forms
with the representatives of that same general group
that appeared in preceding and succeeding geologic
ages, we are likely to find clear indications of orthogenesis. We see that a characteristic change has taken
place between the organism of one age and those of
the next, and that in the succeeding ages there has
taken place a series of further changes along this same
predetermined line. Since we cannot see how environmental influences could have brought about this peculiar succession, we are inclined to attribute it to some
unexplained force that is inherent in the organism.
For example, in our primitive plants there appears a
certain structure that is 16 units in length. Another
group of plants, somewhat more modern than the first,
contains the same structure with a length of 8 units.
As we pass to the more and more modern groups of
plants we find this structure gradually being reduced,
the changes passing through the series 4, 2, 1, 1/~, 0
units. Since this particular structure in plants is
rather removed from environmental influences and
outside the scope of natural selection (so far as we
can see), it is strongly suggested that some internal
force has been driving along continuously in the same
direction.
Some evidence of orthogenesis is also provided by
breeding experiments with modern plants. The Boston
fern suddenly produced a type that was a dwarf. Some
time later these dwarf descendants produced a type
that was still more of a dwarf. Again, the singly compound leaf of this fern was supplanted in some of the
descendants by a doubly compound leaf, and later




58 WHERE EVOLUTION AND RELIGION MEET
changes in this same line achieved a triply compound,
and finally a quadruply compound leaf. These changes,
which are evidently along a predetermined line, are
attributed to orthogenesis. It is implied that there is
in existence an internal force that operates independently of environmental influence.
Orthogenesis has been advanced by some as an explanation of evolution. All evolutionary changes could
be accounted for by saying that they were due to the
operation of this mysterious, internal, directing force,
which had been playing its rile through the ages quite
independently of outside influence. Although this
might be a simple account of evolution, it could not
be regarded as an explanation. In order to explain the
process, it would be necessary to understand this mysterious internal force and to see why and how it
operates. In truth, orthogenesis explains nothing, but
merely directs our attention to one of the phenomena
of evolution that requires explanation.
ISOLATION THEORY
If a given race of men remains, through the centuries, living in some rather restricted locality, the
form of language used by all the individuals of that
race will be essentially the same. If, on the other hand,
certain members of this race migrate to a new territory,
and remain there for a few centuries without holding
any intercourse with their relatives at home, at the
end of that time the form of language of the colonists
will differ in many of its characteristics from that of
the stay-at-homes. This result has been brought about
by the fact that the colonists have been isolated from
the rest of the race.
Many of the features of evolution can be accounted
for by exactly these same principles. If a given race
of animals remains, through the centuries, living in
some rather restricted locality, the characteristics of




SOME OTHER THEORIES OF EVOLUTION 59


all the individuals of that race will be essentially the
same. At one time or other there may have appeared
in this race a few individuals which, due to some type
of variation, were distinctly different from the rest.
Now if this difference were of no significance in the
struggle for existence it would gradually be erased.
The individuals which possessed the modification
would mate with normal, unmodified individuals. The
progeny would, in general, show characteristics intermediate between those of the two parents. As a result, the modification would be reduced one-half.
These "half-modified" forms would in turn mate with
certain of the normal, unmodified individuals which
make up the great bulk of the population. The progeny
from such matings would then be one-quarter modified.
Thus the original modifications would gradually be
erased or "swamped out" through the free crossing of
the few modified individuals with a series of those
unmodified forms which go to make up the bulk of the
population. This free intercrossing tends to maintain
a general average, to keep the characteristics of every
individual of the race very much the same. This is
the result which obtains when all of the individuals
of one race of animals are freely intermingling in one
region.
If, however, a few of the animals of this race migrate
to a new region, a region which is (or becomes) separated from the original one by some geographic barrier (for example, mountains, bodies of water, stretches
of desert), such that any return migration is rendered
difficult, important consequences will follow. In this
small group of colonists there may appear a few modified individuals. Under the circumstances, these individuals will have a very limited choice in mating.
Since the group of colonists is so small, it may be that
there are about as many modified as unmodified
animals. Hence the result of free crossing within this




60   WHERE EVOLUTION AND RELIGION MEET
small group will finally produce a population of "halfmodified" individuals. The population of colonists is
now somewhat different from the original race, and
this is only the start. The original change will open
the way to further changes. At the end of some centuries the colonists will be different in a good many
respects from the stay-at-homes. Thus isolation
brings evolutionary changes in the characteristics of
animals (and plants) in much the same way that it
brings changes in language.
This is not mere speculation. There is in existence
a great mass of evidence to support these ideas. We
find that where free crossing is possible among all the
individuals of a race of animals these individuals are
essentially the same in all of their characteristics. We
find that where a small group has become isolated
some centuries back there are characteristic differences
between the members of this group and the parental
race. If the isolation took place at an earlier date, the
differences are greater. A great many of the differences
that we see among our plants and animals of today
have come through the effects of isolation.
But is this a satisfactory explanation of evolution?
It may serve to explain the establishment of differences
between certain groups of animals and plants, but evolution amounts to something more than this. The
true, fundamental feature of evolution lies in the progressive changes that have taken place, those changes
which make the plants and animals of today better
adapted to their environment than were their more
primitive ancestors. This feature, the true progressive
evolution, is not explained by the isolation theory.
Isolation accounts for the establishment of mere differences, but not for the progressive evolutionary
changes.
Consequently, although most biologists recognize
the truth of the isolation theory, they do not regard it




SOME OTHER THEORIES OF EVOLUTION 61


as a satisfactory explanation of evolution by itself.
This theory, however, provides a very useful corrollary
to the theories of Lamarck, Darwin, or De Vries.
Choose one of these "classic" theories to explain progressive or adaptive evolution, the production of the
more advanced organisms from the more primitive,
and then let the isolation theory explain "lateral"
evolution, the multiplication of species "on the same
level."
HYBRIDIZATION THEORY
When we speak of a "species" of plants or animals
we refer to a group within which the individuals are
alike with respect to their more important characteristics; but very commonly a species may be composed
of several smaller groups known as "varieties." One
variety differs from another with respect to characters
of minor importance.
In the normal course of events, an individual of any
given variety will mate with another individual of that
same variety; but by artificial means man can mate an
individual of one variety with an individual of another
variety. A mating of this sort is called a "cross," and
the progeny which result from such a mating are "hybrids" (half-breeds). In view of the fact that the two
parents in a cross differ from one another with respect
to some of their characteristics, what will be the nature
of the hybrid progeny that result? In general it may
be answered that the hybrids will exhibit one or more
of the following three features. (1) Hybrids may be
intermediate between the two parents. For example,
if one parent has red flowers and the other parent has
white, the hybrid may have pink flowers. (2) Hybrids
may possess some of the characteristics of one parent
and some of the characteristics of the other, thus exhibiting a new combination of characteristics. For
example, one parent might be tall and have smooth




62 WHERE EVOLUTION AND RELIGION MEET
leaves; the other parent might be short and have hairy
leaves; and the hybrids might then be tall and have
hairy leaves. (3) Very rarely hybrids may exhibit
characteristics that are possessed by neither of the
parents. For example, the two parents might both
have white flowers (differing, of course, in other respects) and the hybrids purple flowers, the purple
being a new character that has evidently been produced by the cross. Of course the peculiarities of hybrids could be described in a great deal more detail
than this, but at present we are interested in noting
merely this one very significant fact: whether the
hybrids show an intermediate grade of character, or a
new combination of characters, or some new character,
in any of these cases the hybrids are really a new
type of organism, a new variety that had not existed
before the cross was made. Any method of producing
new varieties has (presumably) considerable evolutionary significance, for this may well lead to the
production of new species, and eventually to still
greater evolutionary changes.
Before deciding whether this phenomenon has any
great evolutionary significance, however, it will first
be necessary to seek the answers to two important
questions. (1) We know that hybrids may be produced
artificially by man, but will they be produced without
man's agency among plants and animals growing in
the natural state? Roughly speaking, this may be
answered in the affirmative; there is excellent evidence
that crossing takes place freely among many of the
plant varieties growing in nature, and this is probably
true, to a more limited extent, for animals as well. (2)
Once the hybrids have been produced, will their
progeny continue to show the same new traits that
characterized the hybrids themselves? In general,
hybrids produce among their progeny three different
types of individuals: some like one of the original




SOME OTHER THEORIES OF EVOLUTION 63
grandparents that entered into the cross; some like the
other grandparent; and some just like the hybrids
themselves. Some of the members of this last group
will thereafter breed true, producing progeny all of
which are like themselves; so we may be assured that
the new varieties produced by crossing (hybridization)
will tend to perpetuate themselves.
It becomes evident, therefore, that hybridization
must have considerable significance in evolution. If
we consider the matter a little more carefully, however, we realize that the r5le of hybridization is subsidiary to, or contributory to natural selection. As
we have seen, hybridization produces new varieties
that would not have appeared otherwise. These new
varieties are then subjected to natural selection. If
they prove to be more poorly adapted to their environment than are the other individuals of that species,
the hybrids will be at a disadvantage in the struggle
for existence and will soon be exterminated. If, however, they prove better adapted than the others, they
will survive and may even crowd out and supplant
the ancestral varieties. Evidently the role of hybridization is to produce a greater number of varieties
from which nature can make her choice. This is really
a very important function. Obviously the greater the
number of varieties produced, the more often will there
appear a new variety which is better adapted, and will
therefore provide a basis for evolutionary progress.
Hence hybridization serves to "speed up" evolution,
making it possible for progressive evolution to take
place at a more rapid rate than otherwise.
In this connection we may note an interesting and
important fact that very few people realize. What
is the real function of sex? Most people would answer
that this function is reproduction; but this is really
not true, as biologists can readily see. Sex is not the
only method of reproduction employed by plants and




64 WHERE EVOLUTION AND RELIGION MEET


animals, but only one of several. Furthermore, of the
several methods of reproduction, sex is distinctly the
poorest, the least efficient. Other methods of reproduction possess all of the advantages and none of the
disadvantages of the sex method. Since this is true,
why is sex the established method of reproduction in
our higher animals and plants? Out of a number of
possible methods of reproduction, why should nature
have chosen the very poorest with which to endow
her best plants and animals? Evidently sex brings
some great advantage which is more than enough to
offset the disadvantages inherent in this method. Sex
is relatively poor as a method of reproduction, but it
secures a great advantage in connection with reproduction, an advantage not possessed by any of the other
methods. This great advantage is the one which we
have just seen. Sexual reproduction produces a greater
number of varieties than does any other method of
reproduction. Thus, by providing nature with a
greater range of choice, sex makes evolution take place
faster than otherwise. We may conclude, therefore,
that the reason that sex is the established method of
reproduction in our higher animals and plants is not
because it is the best method of reproduction, but
because it brings a great advantage for the process of
evolution. It might well be said that the very existence of sex is good evidence of the fact of evolution.
Some have claimed that hybridization, considered
in connection with natural selection, provides a complete explanation of evolution. This extreme view is
not justified. In the first place, hybridization can
occur only in plants and animals that have sex. Since
our most primitive plants and animals do not have sex,
evolution must have been accomplished in these early
groups by some other means. In the second place,
although hybridization appears to produce new varieties, it is really not the final cause that underlies this




SOME OTHER THEORIES OF EVOLUTION 65
production. To put the matter in another way, hybridization can produce new varieties only after certain other evolutionary forces have already operated.
This point comes out clearly when we attempt to
visualize why it is that hybridization produces new
varieties. If two individuals of the same variety are
mated, no new varieties result. Why not? Because
the two parents were similar. If individuals of two
different varieties are mated, new varieties result.
Why? Because the two parents were different.' We
may conclude, therefore, that hybridization produces
new varieties only because the parents to the cross are
themselves different. How did the parents come to be
different? Again it might be said that this existing
difference is to be accounted for by some previous
hybridizing; but this is merely begging the question.
Originally the differences must have been caused by
some means other than hybridization. These are two
good reasons why hybridization does not provide by
itself a completely satisfactory explanation of evolution. Even so, hybridization must be regarded as
having considerable importance in evolution, for in
many groups of animals and plants hybridization
makes evolution take place much faster than otherwise; and furthermore, hybridization may often secure a very desirable combination of characters that
would be very unlikely to be brought together by any
other means.
We may now conclude that none of these three
"other" theories is in itself a completely satisfactory
explanation of evolution. It is equally clear, however,
that each contains forces which are contributory to
Even in the case where the hybrids exhibit a character not
possessed by either parent, this has been brought to pass by a
combination of certain "invisible" elements from one parent with
other invisible elements from the other parent. This fact can be
proved very neatly by the proper experimental breeding.




66 WHERE EVOLUTION AND RELIGION MEET


evolution. To get comprehensive ideas on the possible explanations of evolution one should, therefore,
have some understanding of orthogenesis, isolation,
and hybridization, as well as the classic theories of
Lamarck, Darwin, and De Vries.
Since none of the three theories that we have just
been considering is a complete explanation of evolution, we could hardly expect them to provide any very
complete recommendations on the matter of human
evolution. A few ideas, however, might be suggested.
Since orthogenesis is so little understood, since it
operates at best in a rather limited way and effects
evolutionary progress very slowly, it would probably
be difficult even to visualize this phenomenon in
human evolution. If orthogenetic changes actually
are taking place to any considerable extent in man,
the same methods that one would employ to preserve
the benefits of mutation would be the safe course to
pursue here also. If those individuals that show orthogenetic change in the right direction are provided with
the proper opportunities, they will perpetuate not
only this desirable change, but also the capacity for
further desirable changes in the same direction. Individuals showing dangerously bad orthogenetic changes
should, of course, not be allowed to reproduce.
Isolation, which in itself accounts merely for the
establishment of differences between varieties and
species, and does not account for progressive evolution,
provides no good recommendation on controlled human
evolution. In the past, isolation has undoubtedly
been very important in bringing about the differences
which we see today between the various races of mankind. For the future, however, we are not desirous
of developing further racial differences of this sort.
In fact, it is our aim to maintain the present human
races without any further splitting up, but to effect




SOME OTHER THEORIES OF EVOLUTION 67


improvement within each of them through control of
progressive human evolution.
Hybridization might seem to recommend for man
the crossing of different varieties, for in that way desirable new varieties are sometimes brought into existence. To jump at this conclusion would, however, be
exceedingly dangerous. It is true that crossing varieties may sometimes result in superior individuals,
through combination of the desirable traits of both
parents. It should be remembered, though, that
crossing may also produce inferior individuals, through
combination of the undesirable traits of both parents.
Since it is (as yet) rather hopeless to predict with certainty which of these results might be obtained in any
given case, human hybridization is a rather hazardous
practice. On the basis of actual breeding experiments
with plants and animals, and also upon inferences that
may be drawn from the results of past human breeding,
the following general recommendation is fairly well
warranted. Wide human crosses (beyond the color
line) are not advised, for the results which these are
likely to bring in the long run are more often unfortunate than fortunate. Less wide human crosses (between slightly different races within the color line) can
for the most part be recommended, for they evidently
bring more advantages than disadvantages.




VII


MODERN VIEWS ON EVOLUTION
THE reader is now able to distinguish six theories
that have been advanced in explanation of evolution,
and knows something of the merits and demerits of
each. It has been indicated that the orthogenesis,
isolation, and hybridization theories, although containing features of undoubted significance, definitely fall
short of being complete or thoroughgoing explanations
of the whole evolutionary process. Lamarck's theory
of Use and Disuse might well have been accepted as a
thoroughgoing explanation of evolution, save for the
fact that it rested upon inheritance of acquired characters, an assumption which clearly was not supported
by the known facts. Darwin's Natural Selection at
first seemed an even more attractive and reasonable
explanation, but here also the theory was not supported by certain critical facts, for experimental breeding rather clearly indicated that selection was never
effective in passing the species boundary. These considerations have, of course, left the impression that
the most acceptable of all the proposed explanations
is the Mutation Theory of De Vries.
This, we believe, is a fair representation of the consensus of opinion among biologists at the opening of
the twentieth century; but we must hasten to add to
this statement two very important reservations. First,
it is distinctly not true that all biologists at that time
held this same opinion as to the relative merits of the
several theories. Second, even those who did have
68




MODERN VIEWS ON EVOLUTION


69


these general views were in no position to maintain
that their views were supported by absolute proof. In
short, although the mutation theory seemed the most
likely of all explanations that had been presented,
there was no absolute assurance that it was the true
or final explanation of evolution, and so scientific men
attempted to maintain an open mind on these matters,
and stood ready to change their opinion in response
to any new and critical evidence that might be forthcoming.
When we think over these various theories with the
hope of arriving at some definite decision as to the real
explanation of evolution, the main impression that we
are likely to get is one of uncertainty. The matter is
by no means settled. Perhaps we may prefer one
theory to the others, but, lest we be guilty of jumping
to a conclusion with too much haste, let us consider
three propositions which have an important bearing
in this connection.
1. After all, is the "problem of evolution" a single
problem? Is it not instead a complex of numerous
smaller problems? Surely this latter is the case, for
we are obliged to explain many different things, to
answer many questions, before we can account for all
the results of evolution that we see in nature today.
Any explanation of evolution must be based on some
change or variation that appears in an individual
organism, something which makes it different from
the other individuals of the same species. Unless we
have such a change to begin with, it is impossible to
devise any scheme to explain evolution. So the first
question to be answered is, "What is the cause of
variation?" Next we face the possibility that varia,
tions of more than one type may be taking place.
Consequently, for any complete understanding of evolution, we must distinguish the different types of
variation that are taking place, and decide which of




70 WHERE EVOLUTION AND RELIGION MEET
the known types is significant in providing a basis for
evolution. Following this, we should understand how
the variations are perpetuated, multiplied, and manipulated by nature to bring about evolutionary progress.
Since all of these questions should be answered before
any complete understanding of the evolutionary
machinery is possible, we must conclude that the evolution problem is really a complex of numerous problems. We could hardly expect that any single idea
would itself provide a solution for all these problems.
2. Is it necessary that we subscribe to a belief in any
one of the theories, to the complete exclusion of the
others? Is it not quite possible that every one of them
may be a factor in evolution, and altogether probable
that no one of them by itself can adequately account
for all the features of evolution? This suggestion
is consistent with the preceding one. If evolution is
really a complex of several distinct problems, it is
quite likely that one theory may provide the best solution for one of the evolution problems, while other
theories provide better solutions for the other problems. Furthermore, it is certainly not true that any
one of the theories is absolutely contradictory of the
others. It is conceivable that the evolutionary forces
which Lamarck describes might be at play side by side
with those of Darwin and De Vries; and at the same
time orthogenesis, isolation, and hybridization might
also be in operation to contribute to the general results. Since this is conceivable, may it not be the
actual truth? May it not be quite true that each and
every one of the theories serves to explain some part
of evolution, while no one of them can explain all of
evolution?
3. After all, can we make much real progress toward
deciding upon the relative merits of the different
theories until we have in our possession more of the
critical facts? In our discussion of the theories we are




MODERN VIEWS ON EVOLUTION


71


always coming face to face with questions of fact,
running into some disputed or doubtful point about
which we might argue indefinitely and to no purpose;
for such disputed points cannot be settled until we
know the true facts which bear upon these points. A
theory is convincing only when it is demonstrated that
the assumptions which it contains are consistent with
the facts of nature. Hence the only sensible way to
settle discussions on evolutionary theories is to renew
our investigation of nature, and seek from her the
answers to our questions. This was exactly the conclusion that scientific men arrived at, and, with the
opening of the twentieth century, they abandoned (in
good part) their rather fruitless discussions, and proceeded to devote their energies toward discovering
more of the critical facts.
At that time there was introduced (mainly by the
work of De Vries) a new and improved method of
discovering facts. Previously men had merely observed natural phenomena as carefully and extensively
as possible and had drawn inferences from these observations. They had seen innumerable evidences of
evolution, and had then inferred that the results which
they saw had been brought about in certain ways.
They were sure that evolution had brought about these
results, but it was a matter of inference as to how
evolution had operated in bringing about these results. Then, with the opening of the twentieth century, a method of investigation was introduced which
made it possible not only to observe the results of
evolution, but actually to observe nature in the act of
bringing about these evolutionary results.
This method of investigation was the experimental
method. Plants and animals were grown under observation for many generations, and were mated artificially according to the plan of the investigation. The
hope was that a certain amount of evolutionary change




72 WHERE EVOLUTION AND RELIGION MEET
would take place under the eyes of the investigator.
It was felt that if one could in this way "catch evolution in the act," he could come much closer than otherwise to understanding the methods of evolution.
In this way the more general study of evolution gave
birth to and became diverted into the experimental
study of heredity, the science of "genetics." Almost
immediately it became apparent that this new science
was destined to play a large part in biology. An
enormous amount of research was started in this field,
and the results obtained were very gratifying. As a
consequence, the last two decades have witnessed a
series of rapid strides in the progress of our understanding of the principles of heredity. This progress
has been of the utmost significance, not only in its
bearing upon the purely theoretical aspects of biology,
but also in a very practical way, through the improvement it has effected in methods of breeding our cultivated plants and domesticated animals. In fact, the
experimental study of heredity has become more profitable than the more general consideration of the problem of evolution ever was. It is not surprising, therefore, that genetics, which was started merely as a
means of solving some of the problems of evolution,
has since come to be pursued for its own sake; so that
today biologists are really devoting more of their attention to genetics than to evolution.
In the present volume, however, we shall not undertake a consideration of the fascinating science of
genetics, for our interest here is in the more general
problems of evolution. Here our interest in genetics
goes no further than the light which it may cast upon
evolution. Without attempting to go into details,
therefore, let us see what answers may be provided
by the science of genetics for some of the questions
of evolution.
First, to consider the case of orthogenesis. Geneti



MODERN VIEWS ON EVOLUTION


73


cists have encountered, in their experimental breeding,
certain cases which might be interpreted as evidence
of orthogenesis. There are so few of these cases, how —
ever, as to indicate that changes of the orthogenetic
type are the exception rather than the rule. Furthermore, even though geneticists may acknowledge the
possibility that orthogenesis has played a real part in
the evolution of the past, they deny the implication
that this is due to some special internal force that has
the peculiar function of directing evolutionary changes
along predetermined lines. Instead they have concluded that orthogenesis is merely one of the manifestations of the same set of forces that also operate
to bring about such other results as mutation.
As for isolation, the results of experimental breeding confirm the idea that this has been very important
in establishing many of the differences that exist between the varieties and species of today. One trained
in genetics can visualize, in much more exact terms
than before, just how the results of isolation have been
brought about. On the other hand, it can just as
clearly be seen that isolation by itself can never bring
about progressive or adaptive evolution. For these
latter results other explanations are required.
Hybridization is, of course, much better understood
than before. The geneticist can see in a very exact way
how the crossing of different varieties results in a
hybrid which may well be said to constitute a new
variety. He can also see how very often the hybrids
are superior to their parental varieties. Such new
varieties may then become established in nature.
Hybridization, therefore, can explain not only the mere
multiplication of varieties, but also, within limits, real
evolutionary progress. On the other hand, it is now
possible to demonstrate very clearly that hybridization
can produce new varieties only because the two parents
in the cross are of a different constitution. And further,




74 WHERE EVOLUTION AND RELIGION MEET


it can be seen clearly that this difference between the
two parents can itself be accounted for only by the
operation of some force other than hybridization, that
is, mutation. In short, hybridization is effective in
bringing about evolution, only after a certain amount
of mutation has already taken place.
It has been seen how Lamarck's theory of Use and
Disuse, which required the inheritance of acquired
characters as an essential part of the explanation of
evolution, was discredited by the appearance of a mass
of evidence which appeared to demonstrate that inheritance of acquired characters was impossible. For
many years after that, and in fact until very recently,
more and more evidence was gathered which still
pointed in the same direction. Recently, however,
some very reliable evidence has been presented which
indicates that inheritance of acquired characters is
really possible.
Without attempting to go into the details of this
evidence, we may merely summarize the indications.
In our very simplest plants and animals it would
appear that a considerable amount of inheritance of
acquired characters may be taking place, so that the
Lamarckian scheme may well have played a large part
in the evolution of these primitive organisms. In
such cases, of course, there would be no "conscious
effort" on the part of the organism, but this conscious
effort was, after all, no essential part of Lamarck's
theory. In our higher plants and animals, we have
reason to believe that the inheritance of acquired
characters can take place, at best, only under very
special circumstances, circumstances which are capable
of exerting a profound influence upon the organism
without killing it. Such circumstances are not often
realized. As to how important this may have been in
evolution, we are very uncertain indeed, and the widest
sort of difference of opinion exists. The best we can




MODERN VIEWS ON EVOLUTION


75


do is to present this summarizing thought; namely,
the Lamarckian scheme may have played a large part
in the evolution of the more primitive organisms, a
considerably smaller part in the evolution of the
higher organisms. Certainly not all of the features of
evolution can be accounted for in this way.
When we subject Darwin's theory of Natural Selection to a critical analysis in the light of our modern
knowledge of heredity, we are forced to conclude that
in one way Darwin was right and in another way he
was wrong. In a very general sense, natural selection
is the true and final explanation of progressive evolution; but if Darwin attempts to account for all evolution through natural selection among small quantitative variations, his theory is erroneous. Today we
understand a great deal more exactly than Darwin
ever did just what these small quantitative variations
amount to. We recognize that selection may be successful in accumulating the effects of these variations,
and we understand rather exactly how this results is
attained. But we can also see plainly that such selection must always reach a limit beyond which further
progress by the same means is clearly impossible, and
we know that in every case in which selection has been
tried this impassable limit is actually reached. To pass
this critical limit requires that something new be introduced by mutation.
We finally fall back, therefore, upon the mutation
theory. Mutation, although perhaps not in itself a
thorough explanation of all the features of evolution,
at the same time seems to be the phenomenon which
underlies at least the great bulk of evolutionary
change. Occasionally, among the individuals of a
given variety, there may appear one or a few individuals which contain some new character, or lack
some old one. If the change is an improvement, if
the mutants are better adapted than were their ances



76 WHERE EVOLUTION AND RELIGION MEET
tors, natural selection will operate to preserve the
mutants and perpetuate them as a new variety (or
new species, dependent upon the definition of
"species"). If, however, the mutants are more poorly
adapted than were their parents, natural selection will
eliminate them. It is rather generally felt that this
principle must underlie, directly or indirectly, the bulk
of evolutionary change and progress that has taken
place in the past.'
' It is true that, even in this mutation theory, some investigators
see a serious difficulty. During the last two decades there have
been discovered, and carefully studied, many hundreds of mutations in various plants and animals, and it is recognized that many
of these are sufficiently different from the parent types to be
called new species. It might well be expected that in the vast
majority of these cases the mutant would be inferior to its parent.
If the mutations take place absolutely at random (which is the
case, so far as we can yet see) there is much greater chance that
the change will be injurious to such a complicated bit of machinery
as a living organism, than that it will effect an improvement.
Hence we can readily believe that only rarely are improvements
introduced by mutation. Even this, of course, would provide an
adequate basis for progressive evolution. But if no mutation ever
brought an improvement, this process would serve merely to increase the total number of species, and would not bring real progressive evolution. Therein lies the difficulty. Out of the many
hundreds of mutations that have been seen to take place, there is
(according to some investigators) not even one which can, beyond
the shadow of a doubt, be recognized as a distinct improvement.
This, of course, would be a serious difficulty, a great flaw in the
mutation theory.
Most biologists, however, have great confidence in the mutation
theory, holding the view that some of the mutations already encountered are real improvements, and will provide a basis for
progressive evolution. Of course there is room for great differences
of opinion on what constitutes an improvement. It might well be
difficult for us to recognize such an improvement when we found
it, for, although it is often easy to see how some of the existing
characters serve to adapt the organism to its environment, it might
be difficult to recognize the true merits of some entirely new
character with which we had had no previous experience. As an
example of this, if such an improvement should take place in
man, would we immediately recognize as such the "superman"
which resulted? After all, even though we might not be able to
convince skeptics that any of the new mutations are improvements,
investigation has at least revealed this much: today there exist




MODERN VIEWS ON EVOLUTION


77


What causes mutation? We do not know, but we
have found out very definitely where in the organism
the mutation occurs, and we have discovered that, by
modifying the environmental conditions in certain
ways, mutations may be caused to take place more
frequently than otherwise. The mere fact that we
have discovered this much encourages us to believe
that in the future we may understand more fully the
causes of mutation.
Summary: Although opinions differ, it is generally
felt that the most significant factors in bringing about
evolution are mutation and natural selection (among
the mutants). This interpretation, however, should
not be accepted to the exclusion of all other theories.
It is more than likely that the operation of Lamarck's
scheme has in the past contributed in a very real way
to evolutionary progress. Isolation and hybridization
also play their parts, but are effective only after mutation has already taken place.
in plants and animals many characters which clearly serve to adapt
the organism to the environment, and there is the best sort of
evidence that these characters are old mutations, that they have
been added to the organism by mutations that have taken place
some time in the past. Hence one feels reassured in saying that,
directly or indirectly, mutation, followed always by natural selection, has been the phenomenon underlying the bulk of evolutionary
change and progress.




VIII


INFLUENCE OF THE EVOLUTION IDEA
IT IS safe to say that the study of evolution has revolutionized human thought. Every subject is now being
considered from the standpoint of its evolution. Not
only do biology and the physical sciences present their
results from the standpoint of evolution, but the evolution of language, of society, of government, of religion represents the present method of investigation
and presentation in all these subjects.
INFLUENCE OF THE IDEA OF INORGANIC EVOLUTION
The idea of evolution has been a conspicuous influence in astronomy. We no longer think of the solar
system merely as consisting of a central body about
which planets travel at various distances, but rather
as the result of a succession of events, following one
another in inevitable sequence. In other words, the
solar system is thought of not so much as a fact, but as
the result of a physical evolution. To understand the
solar system is not so much to observe its present condition as to realize the series of changes that have led
up to the present condition, and the possible changes
that are yet to come. This evolutionary point of view
sees in every present situation the suggestion of both
history and prophecy. When astronomy carries us beyond the solar system into the infinite spaces, there are
presented to us glimpses of all stages in the evolution
of the physical universe.
The same point of view controls the work on earth
78




INFLUENCE OF THE EVOLUTION IDEA  79


structure as presented by geology. The significant
thing is not so much what the earth is, but how it
came to be what it is. Its present structure cannot
be understood without some knowledge of the changes
which have brought it about. We have long recognized that the superficial features of the earth were not
"created once for all," but are in a continual state of
flux. The recorded history of any region of the earth's
surface includes many changes. The "everlasting hills"
may be a phrase true enough when the comparison is
with human life, but these same hills were evolved and
subsequent evolution will change them. When the
recorded history of the earth is presented by geology,
both as to its surface configuration and its vegetation
covering, it is recognized to be a history of continual
change, just as human history is a record of continual
change.
INFLUENCE OF THE IDEA OF ORGANIC EVOLOTION UPON
BIOLOGICAL SCIENCES
The influence of the idea of organic evolution is more
extensive in its application than the idea of inorganic
evolution, for it deals with life and all of its expressions. Its importance in the development of the biological sciences cannot be overestimated. The result
has been not only an increased knowledge of the various aspects of biology, but also enormously important
practical applications of this knowledge. A few illustrations will be given of how the evolution idea has
influenced biological investigation.
The oldest phase of biology was the classification of
plants and animals. Classification was necessary first
for convenience in organizing the vast amount of material. The first classification was purely artificial, as
much so as the arrangement of words in a dictionary,
or of entries in a card catalogue. For example, among
plants, the major groups were herbs, shrubs, and trees.




80 WHERE EVOLUTION AND RELIGION MEET


This brought together forms entirely unrelated, and
also separated near relatives. When the idea of evolution took possession of biology, it was evident that
plants and animals must be classified on the basis of
relationship, as indicated by resemblances and differences. From that time biologists specializing in classification have been constructing what may be called
"family trees." Many families are now recognized,
made up of closely related forms, evidently related to
one another by descent. This same thought has also
resulted in connecting the ancient plants and animals,
known only as fossils with those now living. The result is that we now have in organized form a history of
the evolution of plants and animals, from their records
in the most ancient deposits to the present time. As
investigation becomes more extensive and intensive,
there are often slight shifts in classification, based on
increasing knowledge of relationships.
After classification, the study of plant and animal
structures began to be developed. The whole purpose was to discover evolutionary relationships from
a knowledge of structures. At first, before the microscope was invented, only gross structures could be investigated, that is, structures that could be seen with
the naked eye. For example, the different forms of
leaves, stems, roots, and flowers were investigated and
compared. When the microscope came into use, this investigation of structures extended to the minute structures that make up the bodies of plants and animals,
the cells and the tissues into which they are organized. These minute structures gave clues to relationships that gross structures could not, and resulted in
much additional evidence of relationship by descent.
It was in this same connection that reproduction
came to be investigated and put upon its evolutionary
basis. With the help of the microscope the whole performance of the individual cells came into view. Per



INFLUENCE OF THE EVOLUTION IDEA 81
haps the most significant results in relation to evolution
came from the study of embryology, which means the
study of all the changes that take place from the egg
to the mature body. In the course of the early development of the embryo, very frequently glimpses
were obtained of the beginnings of structures that soon
disappeared, and were not represented in the mature
plant or animal, but were present in some other plant
or animal. It was natural to conclude that this indicated relationship. The main stimulus of the extensive
work in embryology has been to discover relationships
which will help to complete the story of the evolution
of plants and animals.
Even a more important result than any of those
mentioned has been the application of the evolution
idea to the study of heredity. The experimental study
of heredity is known as "genetics," and this important
subject owes its origin and development to the evolution idea. The laws of inheritance have such a wide
application in human interest and in the practical
handling of plants and animals that this debt to evolution cannot be overestimated.
It is evident, therefore, that the evolution idea has
been the great stimulus to investigation in physical and
biological sciences, and that our great progress in these
important fields began when the thought of evolution
took possession of scientific men.
The influence that our knowledge of evolution has
exerted upon biological sciences is not limited to the
purely theoretical aspects of those sciences. Biology
has a number of very practical applications, and, in
the field of these practical applications, our knowledge
of evolution can often be applied in a very practical
way. Most conspicuous, perhaps, is the contribution
which evolution makes to agriculture through improvement in the method of breeding our cultivated plants
and domesticated animals,




82 WHERE EVOLUTION AND RELIGION MEET
It has already been mentioned how the study of evolution culminated in the science of genetics. Genetics,
the experimental study of heredity, may be regarded
as the most modern method of studying evolution. The
subject matter of genetics, therefore, is very properly
a part of our knowledge of evolution. What we have
learned of genetics has taught us how to breed our
cultivated plants and domesticated animals in the most
efficient way.
The possibility of improving our cultivated plants
and domesticated animals has been brought out in
some of the previous chapters. We know that in past
centuries man has accomplished a great deal in this
line. Man originally started to practice agriculture
upon those wild types of plants which nature provided.
These plants were not particularly, suited to man's
needs, but were simply the best types that were available at that time. As time went on, however, man
found it possible to change the characteristics of these
plants so that they became much better suited to his
needs.' In other words, an evolution of the cultivated
plants commenced to take place. In bringing about
this evolution, the same general forces were in operation as when evolution takes place in nature.
Now we have seen how, in nature, progressive evolution is brought about through the operation of natural
selection. Generation after generation the only individuals which are allowed to survive and reproduce
are those which are the best adapted to nature's requirements. In this way a gradual progress is effected
in the direction of more perfect adaptation to nature's
requirements. It was according to exactly these principles that man changed his cultivated plants. Generation af ter generation the only individuals which he
would use for seed were those which were the best
adapted to his own needs. In this way a gradual
progress was effected in the direction of more perfect




INFLUENCE OF THE EVOLUTION IDEA 83
adaptation of the cultivated plants to man's needs.
The same general forces are in operation in both cases,
but, since the standard for selection is different, it follows that the direction in which progress is made is
also different. Nature, who is the selecting agent in
the one case, perfects her plants toward a better adaptation to the natural environment; man, who is the
selecting agent in the other case, perfects his plants
toward a better adaptation to his own needs. In the
one case we have natural selection, and in the other
case "artificial selection."
Just how much man has already accomplished in
this way can be appreciated when we contrast our
present cultivated varieties of plants with the wild
natural varieties from which they have descended. In
most such cases the difference is so great that we would
probably refuse to believe that the present cultivated
variety is in any way related to the wild ancestral
type, if we did not actually know that this was the
case. Probably the most striking instances of this
appear among that group of plants which we commonly refer to as "vegetables." In one famous case,
mentioned previously, man has derived from a single
wild ancestral type the cabbage, kohlrabi, Brussels
sprouts, cauliflower, kale, and collards. These types
differ widely from one another, and all differ from
the ancestral type which is still growing wild in some
regions. This is merely one of many possible examples.
Similar "miraculous transformations" might be found
among our cereals and fruits. Furthermore, what has
been said of our cultivated plants applies as well to our
domesticated animals, where, through this same policy
of selection, enormous changes have been effected in
the course of the past few centuries of stock raising.
One can readily see, therefore, that much in the way
of practical gain can be accomplished through artificially controlling the course of evolution in our culti



84 WHERE EVOLUTION AND RELIGION MEET
vated plants and domesticated animals. It is evident,
however, that practically all of what man has accomplished in the past has been without any knowledge of
evolution. In a purely empirical way man adopted
a sort of a "common sense" policy of selection, and
reaped the benefits thereof, without at any time understanding why his selection was effective or what was
the true evolutionary significance of the process. Since
this is true, since man has made such enormous gains
without any knowledge of evolution, how are we justified in claiming that a knowledge of evolution (especially heredity) is of great practical value in this field?
The answer is simply this. What has been learned
from the study of genetics makes it possible to accomplish in a very efficient manner those same things which
the untrained breeder of past centuries did in a rather
inefficient manner. Since the breeder of the past did
not understand the mechanism with which he was
working, he proceeded in a clumsy manner and attained
his objectives only after the lapse of a great many
years of effort, a good part of this effort having been
absolutely fruitless, owing to the numerous mistakes
which he made. With exactly the same start, the
trained geneticist of today would be able to get the
same results with an expenditure of much less time,
effort, and space. This means that the same results
could be obtained at a much smaller cost, which is
efficiency.
This further fact must also be quite evident. If,
through training in genetics, the breeder of today can
get the same results as before in a much smaller time,
it follows that in a given period of time he can get
more results. This is actually the case. During the
past decade we have been reaping the benefits of selection at a much more rapid rate and in a much more
wholesale way than ever before. In addition it can be
seen that the field of selection has been enlarged and




INFLUENCE OF THE EVOLUTION IDEA


85


that the results of selection today are more permanent
and in several ways better than before. Although reliable figures are not as yet available on this matter, it
is surely safe to state that the application of modern
selection methods during the last decade has brought
results which are worth many millions of dollars annually to the agriculture of this country.
The improvement in selection methods that has
come with a knowledge of genetics is, after all, less
striking than the improvement that has been effected
in connection with another method of breeding. We
have already considered how hybridization may bring
evolutionary progress when the hybrid produced by a
cross combines in itself some of the desirable characteristics from both parents. This same principle can
be turned to great advantage by man. Through crossing two of his cultivated varieties of plants, man may
produce a hybrid variety which is superior to either
parent. In addition to the superiority which results
from combining some of the desirable traits from both
parents, hybrids frequently exhibit a size, vigor, and
productiveness that is vastly greater than that of either
parent. The mechanism which operates during hybridization is a very complicated one, and it requires a
considerable training in genetics to be able to guide
artificially the operations of this mechanism. Before
the twentieth century, breeders only occasionally, and,
we might well say, through a lucky chance, reaped
some of the practical benefits of hybridization. During
recent years, however, owing to the knowledge that
we now have of genetics, the practical results from
hybridization have been enormous.
From what has been said the reader can appreciate
how a knowledge of genetics makes it possible for the
breeder, in a much more efficient manner than before,
to improve the quality and productiveness of our crop
plants. By exactly the same principles it is possible




86 WHERE EVOLUTION AND RELIGION MEET
to develop certain additional types of wild plants up
to the point where they are useful to man. In two
other ways also these same principles are applied to
great advantage. Owing to undesirable features of
climate and soil, many large regions of our country
have in the past been unable to support cultivated
crops. Some of these regions have recently been made
available through the development of new types of
crop plants that are able to grow in a poorer soil or in
a drier or colder climate than before. These things
have been achieved through intelligent selection or
hybridization. Again, a fact which many people do
not fully appreciate is that practically all of our cultivated plants very often become the victims of very
serious diseases. In such cases it is impractical to treat
the individual patient as we do in human disease.
Instead we merely attempt to check the spread of the
disease through the application to whole fields of plants
of certain fungicides which will kill the disease germs.
But very often a treatment with fungicides is quite
ineffective, as when the germs of disease inhabit the
soil and cannot be reached by fungicides. Even where
fungicides might be effective it is hopeless to apply
them thoroughly to crops grown on such a large scale
as our cereals. In such cases we are helpless in checking the ravages of disease, and our only recourse is to
develop, by selection or hybridization, new types of
cultivated plants which are naturally resistant to the
attacks of these diseases. These illustrations show how
wide a field it is in which we can reap the benefits from
applying our knowledge of genetics. Much has already
been accomplished along these lines, not only with
cultivated plants but also with domesticated animals.
Much more will undoubtedly be accomplished during
the next few decades.
Another very practical field of biology in which
enormous benefits have been reaped from knowledge




INFLUENCE OF THE EVOLUTION IDEA 87
of evolution is the field of human medicine. Since
we know from our study of evolution that man is a
descendant of the lower animals (though not a descendant of the present-day monkeys), we become
assured that the structures and functions of man are
laid out on the same fundamental plan as in the lower
animals. It is possible, therefore, to conduct certain
experiments upon lower animals and in that way to
make certain important discoveries that are applicable
to man. This practice, popularly known as "vivisection," has been attacked violently by certain blind individuals who must have failed utterly to appreciate the
true, values of the situation. It is undoubtedly true
that the lives of many of these same individuals, or at
least the lives of persons dear to them, have been saved
time and again through a medical knowledge which
has been made possible only as the result of those experiments upon lower animals which they condemn so
ruthlessly. Surely it is obvious that the marvelous
skill of the trained surgeon and his frequent "miraculous" successes have been made possible only through a
most intimate knowledge of the bones, muscles, bloodvessels, nerves, and other tissues of the human body;
and further, that this knowledge of the tissues of the
human body is founded in good part upon the investigation of tissues in the bodies of lower animals, where
the general structural plan is the same. Even more
significant than structure is the matter of function.
It is mainly experiments upon living animals that have
taught us the final details of function in the various
organs of our own body. Not only the surgeon but the
physician is dependent upon what has been learned in
this way. Those many "medicines" which are so useful
in administering to our health have been "tried out"
in the first place upon lower animals, and it is only
through this means of approach that it has been possible to introduce many of them.




88 WHERE EVOLUTION AND RELIGION MEET


Perhaps the most effective way of emphasizing these
points will be to present a single striking (but quite
representative) example. This is an account of merely
one of the many successes of one of our eminent surgeons. It illustrates how intelligent operations upon
the human brain have become possible through a study
of the brain of lower animals, through discovering that
there are always certain definite areas of the brain
which govern the activities of the muscles in certain
regions of the body.
(Quotation from Dr. W. W. Keen, Surgical and
anatomic evidence of evolution. Science 55:603-610,
1922.)
"A young woman with epilepsy, in whom the attacks
were constantly increasing in frequency and violence,
insisted that her attacks always began in her left
thumb, then spread to the hand, then to the arm, followed by unconsciousness and violent convulsions all
over the body. Careful observation for two weeks in
the hospital confirmed her statements that the fits
always did begin in this left thumb. If, then, I could
prevent the fit from beginning in this thumb, so I
reasoned, it might be that I could prevent the entire
attack. Just as, in a row of bricks standing on end, if
I can prevent the first one from falling, none of the
others will fall.
"The possibility of the exact localization of the little
cube of gray matter on the surface of the brain, dominating all the muscles of the thumb, was the key to
the whole operation. This localization of the thumb
center had been made absolutely by experiments on
the brains of animals. Accordingly, I opened her skull,
identified the spot corresponding to the thumb center
(i.e., the great toe of the fore foot) in animals, and cut
out a small cube less than an inch on each side." After
the operation, the epileptic attacks of the patient,
which before had occurred almost daily, recurred only




INFLUENCE OF THE EVOLUTION IDEA 89
about once in a year, and she recovered from the operation without any bad after effects.
An enterprise of vast practical importance, which
quite properly may be regarded as one of the applications of biology, is the matter of human breeding.
The prospect of better human breeding has been clearly
appreciated by but few persons, and in the nature of
the case there has been very little done to date in the
way of actively controlling this situation. There can
be absolutely no question, however, but that man is
subject to those same laws of evolution and heredity
which operate upon the lower animals and plants. We
have already observed how in nature there takes place
a gradual progressive evolution of animals and plants,
with the general result that these organisms become
better adapted to their environment. We have also
seen how man may take an active part as agent in the
process, and may so direct the course of evolution in
his domesticated animals and cultivated plants that
these forms become much better adapted to his own
needs. Since evolutionary progress is possible with
lower animals and plants, it must also be possible with
man; and since an intelligent control of the direction
of evolutionary progress is possible with lower animals
and plants, this also must be possible in the case of
man.
An intelligent control of the direction of human evolution can be exerted in two general ways. In the one
case man can play a rather active part as the selecting
agent; in the other case he can assume a relatively passive role and let nature do the selecting more or less
under his supervision. Much in the way of real practical progress can be brought about in either way. It
is appropriate that we should all understand these two
methods of controlling human evolution, and that we
should all exert our influence toward furthering the
proper application of both methods.




90 WHERE EVOLUTION AND RELIGION MEET


The "active" method is where man takes upon himself the responsibility of deciding that certain "desirable" individuals shall reproduce, and that certain
"undesirable" individuals shall not reproduce. On the
face of it the results of such a policy are bound to be
good, for it leads to a multiplication of the desirables
and an elimination of the undesirables. On the other
hand, it is quite evident that this policy could never
be applied in any very thoroughgoing way, not only
because man would violently resist any such radical
restriction of his personal liberties, but also because as
yet no one is-well enough informed to take the responsibility of intelligently controlling this enterprise. As
yet it is only within very narrow limits that this policy
is practicable, really only in connection with those cases
where we can say beyond the shadow of a doubt that
certain individuals are a menace to society and should
not be allowed to reproduce their kind. The active
control of human breeding should be exercised only
after we have developed a thorough understanding of
the subject with which we are dealing.
This enterprise of exercising an active control of
human breeding represents the subject of "eugenics."
Eugenics quite properly devotes itself to a twofold
task: (1) learning more of the facts and principles of
heredity in man; (2) devising the proper means of
applying the knowledge so gained to the active control
of human breeding. The second phase always follows
the first; application is attempted only in cases where
we are quite certain of the critical facts.
The first task of eugenics, that of learning the facts
of heredity in man, is a great deal more difficult than
might at first appear. During the last two decades
geneticists have learned a great many of the facts of
heredity in some of the lower animals and plants; but
what has been possible for these lower organisms seems
well nigh hopeless in the case of man. There are sev



INFLUENCE OF THE EVOLUTION IDEA  91


eral reasons for this. First and foremost is the fact
that we can experiment upon lower animals and plants,
controlling their matings and the conditions under
which they live. This is out of the question in the
case of man. In addition to this, man is, after all, an
exceedingly unfavorable type of material in which to
study heredity. The generations are far apart, the
number of offspring from any given mating is very
small, and the great complex of different characters
contained by any single individual is extremely confusing as compared with those lower animals and
plants that have been used so successfully in the study
of heredity. How then is it possible to learn anything
about heredity in man?
Although extremely difficult, this task is not impossible. In the first place, one can benefit by what has
already been learned of the principles of heredity in the
lower animals and plants. Knowing these principles
in advance, one can quite often interpret situations in
man which are due to the operation of these same principles. Then, lacking experimental data, one consults
the only data that are available, that is, family pedigrees. These family pedigrees are studied through as
many generations back as reliable records have been
kept, and in this way the method of inheritance of
quite a number of characters has already been discovered. The great difficulty, of course, lies in the fact
that the characteristics of one's ancestors are seldom
recorded in any very exact way, and it is only when
an absolutely exact record is known that such data can
be used. About the best records that are available are
those that have been preserved by some family physicians, for in these cases the accounts are usually in a
very exact and scientific form. For the most part,
however, it is only matters of disease and abnormality
that physicians have concerned themselves with. It is
not surprising, therefore, that we have a much more




92 WHERE EVOLUTION AND RELIGION MEET
exact knowledge of the inheritance of abnormalities
than of the "normal" characteristics of man. All in
all it can be seen that there is an enormous amount of
labor involved in learning the facts of inheritance in
man.
Work of this sort has been going on for several years,
and is still being carried on very actively under the
supervision of the Eugenics Record Office, Cold Spring
Harbor, N. Y. Although there has as yet been only
enough time to scratch the surface of this vast subject,
there is already available a great body of information
bearing on the inheritance of various of the characters
of man. Although the indications are rather clear that
some desirable characters (such as special abilities of
one sort or another) are heritable, the exact mode
of inheritance in such cases is not well understood.
Undoubtedly it will be many years before we are ready
to provide any very certain recommendations upon
methods of producing superior individuals through a
combination of the characteristics of two "desirable"
parents. After all, there is no great urgency for this
"positive" application of eugenics, and we could expect
in this matter no very general cooperation on the part
of the public.
Much more, however, is known about the inheritance
of certain undesirable characters. Not only do we know
that such things as feeble-mindedness, insanity, etc.,
are heritable, but we understand the exact mode of
inheritance of these traits. In other words, we are
ready to provide very definite recommendations as to
methods of eliminating from society certain types of
inferior individuals. This may be regarded as the
"negative" application of eugenics, the purification of
the human race through an elimination of undesirable
types. Since there is great urgency for this negative
application of eugenics, we do expect in this matter not
only a sympathetic but an enthusiastic cooperation on




INFLUENCE OF THE EVOLUTION IDEA 93
the part of the general public. Already a certain
amount of this cooperation has been obtained, and
as a result there have been enacted in a number of
states laws requiring the segregation or sterilization of
certain undesirable types, so as to prevent the further
multiplication of individuals of this sort. Much good
will undoubtedly result from these measures. Much
more good will come in the future when our laws governing these matters are more complete.
It is hoped that this brief account will provide the
reader with some conception of the eugenics enterprise.
It is also hoped that the reader will cultivate an intelligent sympathy for this enterprise. A word of caution
might be well, however. An unrestrained enthusiasm
is likely to do such a cause more harm than good.
Matters of this sort cannot be rushed. We must not
attempt application until we are certain of our facts;
and we should not attempt to impose an application
upon a relatively unsympathetic public. A more general education on these affairs will be profitable.
After all, however, our original object was simply
to point out to the reader one of the important practical applications of our knowledge of evolution. Surely
it is evident that eugenics depends entirely upon a
knowledge of heredity. Our knowledge of heredity
has come as a natural outgrowth of the study of evolution, and is properly a part of that more general
subject.
The hope of intelligently controlling the direction of
human evolution rests not entirely with eugenics. Following the program of eugenics, man plays a relatively
active role as agent in the selection of those individuals
which are to survive. Side-by-side with eugenics, however, there should be put into application another
method of controlling human evolution. In this latter
method man assumes a more passive role, merely allow



94 WHERE EVOLUTION AND RELIGION MEET
ing natural selection to take her course under his supervision.
If man were living in the same "wild" environment
as the lower animals, natural selection would doubtless
operate to modify him in the direction of great physical
strength and powers of resistance. These features
would be more perfect adaptation to a wild environment. Man of today, however, is living in quite a
different environment, a "civilized" environment, in
which the most prominent and exacting demands are
those which arise from his continuous and varied contacts with other human beings. In such an environment the most important features of perfect adaptation
are not mere physical strength, but consist instead of
various types of mental power. Industry, enterprise,
courage, sagacity, etc., are what are required of man to
adjust himself effectively to the conditions of life that
surround him.
Now it is quite certain that natural selection will be
in operation to eliminate the more poorly adapted individuals and preserve the better adapted, and it is inevitable that some sort of evolutionary progress will
result. But are we sure that this is the right sort of
evolutionary progress? Are we sure that it is operating
in the direction of producing "better citizens" and a
better society? As has been pointed out in some of the
preceding chapters, we may be confident that we will
move in the right direction if society is organized on
sound political, economic, and educational principles.
Under those circumstances the "good citizens" will
usually survive and the bad citizens perish. But under
unsound political and economic systems it is quite possible that a premium may be put upon greed, injustice,
and dishonesty. Under such circumstances the greedy,
the unjust, and the dishonest individuals will be successful in life. These will be the "fit" under such a
system, and human evolution will inevitably operate




INFLUENCE OF THE EVOLUTION IDEA  95


to multiply such individuals and exaggerate such traits.
Further, under an unsound educational system many
of the truly desirable individuals will have no opportunity to express their desirable traits, and the important influence which they should be exerting upon the
improvement of society will be lost when these individuals are themselves lost in obscurity without reproducing their kind. How important it is to establish
and preserve sound political, economic, and educational
systems! How impressive and how practical is this
lesson on human progress which comes from our knowledge of evolution!
INFLUENCE OF THE IDEA OF ORGANIC EVOLUTION OUTSIDE
THE REALM OF BIOLOGICAL SCIENCES
All human problems are in a certain sense biological.
The evolution idea, therefore, has a wider application
than its use in guiding investigation in the physical and
biological sciences, and in applying the results of such
investigation to human needs. The principles of evolution have perhaps not been applied as fully as they
deserve to be in the interpretation of the problems
presented by history, political science, sociology, economics, etc. Evolution indicates that certain conditions and their results are inevitable, and that progress
in any desired direction is possible. Training in the
analysis of situations and in the recognition of conditions of desirable progress is certainly supplied by a
study of evolution. A few concrete illustrations will
help to make this possible application of the evolution
idea more obvious.
Racial problems are becoming more and more pressing as the races of men are being brought more in contact. In the old days of race isolation there were no
such problems, but complete isolation is no longer possible. Races inevitably come into commercial and
political contact, but the problems are particularly


A




96 WHERE EVOLUTION AND RELIGION MEET


acute when all the races are mingled in one government, as in this country. Racial groups may be considered as organisms, and their reactions to one another
are as evident as are the reactions of plants and animals
in the evolutionary program. There is conspicuous
a struggle for existence, the gradual adaptation to
conditions, the survival of those that become better
adapted, the gradual elimination of those that do not
become adapted. Even the "friendly" struggle between
racial groups results in natural selection. It will all
depend on the basis of this selection, and the evolution
idea suggests that this basis must be one that makes
for better human relations. The evolution program
will be inevitable, but what may be called the evolution motive may be controlled.
The evolution program can be observed also in connection with political groups. They are constructed
for struggles, and in this case adaptation to the desires
of those who determine such issues will have the usual
result. As issues shift, adaptations shift, and progress
in a given direction may not be constant. The principle of natural selection is exemplified nowhere more
clearly than in the struggle for existence among political groups, and when these groups multiply, the final
adaptation selected may not be very conspicuous. For
this reason, political progress may be very slow, or
selected adaptations may even result in retrogression.
In any event, progressive evolution as a result of the
struggle of political groups for existence is the thing
to be secured, even if it is very gradual.
The problems involved in the struggle of economic
groups are even more acute than those connected with
political groups. Certain economic groups may be defined as institutions representing commercial units.
We recognize that they are competing institutions, and
that their struggles with one another are based upon
the desire to be "selected." Every device used has this




INFLUENCE OF THE EVOLUTION IDEA 97


bid for selection in view. In these cases, of course,
there are many kinds of selection, but each one of them
determines the survival value of some adaptation. The
total result of this kind of struggle is probably better
service, so that it may be expected to represent progressive evolution.
The economic classes of individuals, however, present more serious problems than the economic institutions. Such classes are represented by capitalists,
farmers, laborers, professionals, etc. The struggles for
existence among these classes are well known, and the
resulting selection has sometimes been in the direction
of progressive evolution, and sometimes in the direction of retrogressive evolution. A better adaptation
for one party to the struggle may be quite the reverse
for another party, and the result is a retrogression.
Natural selection, resulting in progressive evolution,
must choose some adaptation favorable for both at
once, for they are mutually dependent. It is for this
reason that in such struggles often some disinterested
party is asked to determine the best selection, the selection that will make for continuance and progress.
It is evident that in all human activities, represented
by races, political groups, economic groups, etc., the
evolution forces are present, and the evolution concept
helps to interpret the results. The same is true of such
intellectual enterprises as philosophy and psychology,
whose representatives are notably evolutionists.
There remains to be considered another great field
of human interest, and that is religion. So important
is this subject, and so often misunderstood in its relation to evolution, that it will be considered in a separate chapter.




IX


EVOLUTION AND RELIGION
THE belief that science is antagonistic to the Christian religion was very general among church people of
a generation or two ago. The accumulating facts of
science, and especially various conclusions based upon
the facts, were thought to contradict certain statements
in the Bible. This attitude towards science in general
became most outspoken when Darwin announced his
explanation of evolution, for among the organisms involved was man, whose physical origin had been settled
in the minds of the majority of Christians by the plain
statement of Scripture./
Gradually the situation changed, and the hostile
camps became allies in a great cause. Relg is -
covered that science is honestly searching for t e truth,
and science discovered tt  P  h  in
a        scle  asls. It seems strange now that the to
groups, each searching for the truth in its own way,
should ever have come in conflict. Truths are not contradictory; if claimed truths are contradictory, then
the truth is not clear.
When it is said that the situation has changed, it is
not implied that all of the representatives of religion
and science have declared an armistice, for in crtain
localities and with certain temperaments the old notion
of the incompatibility of science and religion persists.
But these are mere "hold overs" from a former general
situation. The whole tendency today is toward the
cooperation of religion and science.
98




EVOLUTION AND RELIGION   9


99


The first thing to make clear is that the impression
that science and religion are in conflict arose from the
confusion of religion with theology. In a certain sense
theology may be called a science, the science whose
subject is God, and the great body of whose literature
is the record of men's conclusions concerning God,
which may fairly be called philosophical speculations.
That such speculations have developed great diversity
of opinion is evidenced by the existence of numerous
church denominations. In the midst of clashing theologies, however, religion remains the same, for it deals,
not with speculation, but with human character, and
its measure of character is conduct. If in their search
for truth scientific men now and then discover facts
that contradict certain conclusions of a speculative
philosophy, they cannot be regarded as attacking religion. About all there has been to the so-called conflict between science and religion is the setting of a
discovered fact over against a speculation.
The thoughtful Christian certainly appreciates the
fact that the presentation of his religion must be adjusted to the increasing body of scientific truth. To
hazard religion upon the issue involved in denying
matters of definite experience is not to be thought of.
In a scientific age the result would be to alienate the
increasing thousands who have come in contact with
science, and to convert a powerful and helpful influence into a serious obstruction. It matters little what
scientific theories are abandoned or withdrawn. They
are certainly never withdrawn because of ignorant
opposition, but only because of advance in knowledge.
If an hypothesis is false, it will come to naught, and
if it is true, no amount of opposition can withstand it.
The subject of organic evolution has aroused more
opposition from certain representatives of religion than
has any other scientific subject. In the minds of the
uninformed Darwin's name seems to be the only one




100 WHERE EVOLUTION AND RELIGION MEET


associated with this field of investigation, and to them
evolution and Darwinism are synonymous. In the
preceding chapters it has been shown that there were
theories of evolution before that of Darwin, as well as
others since. It so happened, however, that Darwin's
theory was announced at the psychological moment for
developing a conflict with theology, and so his name
became identified with this conflict. In the recent
revival of this old conflict, we are hearing again that
evolution is anti-Christian. The most obvious fact to
one who believes in both evolution and Christianity is
that there is an entire misunderstanding as to the facts
and claims of evolution as it has been developed by the
more recent work. Such a misunderstanding has been
corrected in the preceding chapters, which give an outline of the attempts to explain organic evolution. One
notable misconception may be easily understood. As
facts multiplied, the current explanations were found
to be inadequate to explain some of them. For example, the more intensive study developed the fact
that Darwin's explanation was not satisfactory. His
name is so identified with evolution in public thought
that the criticism of his conclusions was taken to mean
that the theory of evolution was being abandoned. The
real situation is that every proposed explanation may
prove inadequate, and yet the facts of evolution remain to be explained.
It is very instructive to realize the revelations made
in recent years by physics and chemistry as to the constitution of matter, and the natural laws that have
brought about such stupendous results as solar systems,
earth structures, etc. This kind of evolution, working
through an extent of time and space almost impossible
to realize, does not seem to have aroused any antagonism. It was in connection with organic evolution
that the theological mind became sensitive. It seems
reasonable, however, to infer that if inorganic evolu



EVOLUTION AND RELIGION


101


tion is simply the method by which God moulds matter,
organic evolution could be regarded as the method by
which God develops organisms. In other words, it is
all the result of the activities of that all-pervading
energy which we have learned to call God. There is
no religious difference between creation by law and
creation by direct command, if back of it all the Creator
is recognized.
-- The fact of progressive evolution is most impressive
in this connection. For example, we have observed
that through all the stretch of earth history, in spite
of all imaginable changes in external conditions, certain structures in plants and animals have changed
steadily in one direction. These steady changes have
carried forward the group as a whole. When we apply
this to the human situation, progressive evolution depends upon what may be called human selection. This
selection determines whether there shall be progress
or not. Human selections of all kinds have been made,
but there has been much progressive evolution. It is
the function of religion to guide human selection, so
that there may result a steady social progress. This
fact of steady progress appeals to the Christian, who
feels that under the guidance of his religion there will
be a progressive evolution of humanity.
The conclusion of the whole matter is that since
evolution is an established fact it cannot be anti-Christian. The alternative need not be considered, for it is
just as clear that Christianity has a scientific basis in
the nature of man, and that its results have been demonstrated as clearly as those of experimental evolution.
The fact is that these two great fields, so far from
being contradictory, are mutually helpful. In this
way the revelation of God in Nature has supplemented
his revelation through Christ.
Nothing is more helpful to the student and leader
of men than a clear application of the working of evo



102 WHERE EVOLUTION AND RELIGION MEET
lution as exemplified in plants and animals. Evolution teaches that progress is gradual; that a better is
progress toward the best; that the future has its roots
in the present. It shows that advance in a certain
direction may not be uniform, for there are periods of
apparent retrogression, as well as those of more rapid
advance. The results are only apparent in the large
view over periods of time, when the tossing back and
forth of surface waves disappears, and the steady advance of the slow-moving current becomes apparent.
It is the Christian claim that God has revealed himself to man not merely in the words of Scripture, but
also in the works of Nature. It would seem likely,
therefore, that the revelation of Scripture is supplementary to that of Nature, containing further but not
contradictory revelation. It would seem more logical,
therefore, to read our knowledge of Nature into our
interpretation of Scripture, than to interpret Nature
by our conceptions of Scripture. The frequent attempts
to interpret natural phenomena by conceptions derived
from Scripture have so often ended disastrously that a
reversal of the process might be suggested. That these
disasters do not involve the Scriptures simply demonstrates that the conclusions were unessential.
As an illustration, it might be cited how common and
painful were the efforts to show the perfect adaptation
of everything in Nature. The most trivial anatomical
parts of plants and animals were held to be perfect, in
the sense that they could not be better adapted to the
work at hand. Since it has been found that there is
no such thing as perfect adaptation among organisms,
and furthermore, that perfect adaptation means stagnation, for it removes the essential factor in progress,
not only have the old views been corrected, but a very
large and new thought has been introduced.
Though absolutely perfect adaptation has never yet
been achieved by living organisms, progress toward




EVOLUTION AND RELIGION


103


more perfect adaptation has been the evolutionary keynote of all bygone ages. At all times the hope and
possibilities of still greater progress toward perfection
have furnished the activating principle for all forms
of life. Endowed at the beginning of life with an
equipment which functioned imperfectly, each living
organism possesses capacities for perfecting that equipment with which the needs of life may be met. The
same is seen on a more magnificent scale in the agelong histories of great groups of plants and animals.
Endowed at the beginning with an imperfect equipment, each race of organisms has possessed capacities
for unlimited progress toward perfection, and the progress of the race has been built upon the progress of the
individuals. Of all living organisms, man alone can
be fully conscious of these possibilities. Man alone
can consciously direct the line of progress, and, through
the lives of successful individuals, make certain progress toward a goalof -perfection.
' The reason why so many scientific men believe in
Christianity is that they find it to be thoroughly scientific.,What can be called a scientific approach to religioni may be outlined briefly as follows.
Religion is now known to be a universal human
impulse. No race of men of any age of the world
failed to give expression to this impulse. Any universal impulse must have some function, The function of the food impulse, for example, is to keep us in
health and vigor. -I-t seems obvious that the function
of the religious impulse is to develop the greatest efficiency, to bring man to the highest expression of his
being. The resulting efficiency all depends on the ideal
selected. If there is an unwise selection in regard to
the food impulse, the result is unhappy; and so if there
is selected an unwise ideal in response to the religious
impulse, the result is far from efficiency.
The effective ideal has been demonstrated by gen



104 WHERE EVOLUTION AND RELIGION MEET


erations of human experience. Man is a bundle of
impulses, some of them base, some of them noble. Not
all of them can dominate. Which one shall be selected
to dominate? This selection determines a man's religion. The baser impulses can be dismissed as out of
consideration when we are selecting a religious ideal.
The problem is to select among our nobler impulses
the one that shall determine a decision when conflicting interests are involved.
If we try to discover the dominating impulse selected
by those whose lives we admire most, those about
whom we read, and also those whom we know, we find
that they have selected unselfishness to dominate their
lives; unselfishness that expresses itself in service. It is
the most difficult possible selection, for it runs counter
to most of our other impulses. But it makes the difference between a self-centered life and an outgoing
life. Men can be put into two categories: those who
are centripetal (self-centered), and those who are centrifugal (outgoing). There can be no question as to
which category is the more efficient.
The next step is to discover the stimulus that will
secure response to an impulse so difficult to keep functional. It is clear that the most masterful human passion, and therefore the most powerful human stimulus,
is love. We realize that everything that is finest in
human character and conduct is in response to the
stimulus of love. Our conclusion is that the most effective ideal for the religious impulse is love stimulating
service. This is the ideal of the Christian religion, and
it makes scientific men choose it as the only religion
with a scientific approach, no matter how much theologians, and rival church organizations, and professing
Christians may confuse the issue. Furthermore, since
it has selected our most masterful passion as the stimulus, it is the final religion.
The great contribution which Jesus made to religion




EVOLUTION AND RELIGION             105
was his recognition of the master passion love as the
most powerful stimulus to develop the best that is possible in man. It is no wonder that in the religion of
Jesus, God is not only called Father, but is personified
as Love. God is Love, that is, the master passion that
can develop the best that is in us.
















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