THE MASTER OF DESTINY
BOOKS BY
FREDERICK TILNEY
THE BRAIN FROM APE TO MAN
IN COLLABORATION WITH
HENRY ALSOP RILEY
THE FORM AND FUNCTIONS OF THE
CENTRAL NERVOUS SYSTEM
THE MASTER OF DESTINY
A BIOGRAPHY
OF THE BRAIN
BY FREDERICK
TILNEY, M.D.
WITH A FOREWORD
BY AUSTEN FOX
RIGGS, M.D.
[Illustration]
DOUBLEDAY, DORAN & COMPANY, INC.
GARDEN CITY MCMXXX NEW YORK
[Illustration]
COPYRIGHT, 1929, 1930
BY FREDERICK TILNEY
ALL RIGHTS RESERVED
PRINTED IN THE UNITED STATES AT
THE COUNTRY LIFE PRESS
GARDEN CITY, N. Y.
FIRST EDITION
FOREWORD
Race after race of man has appeared on this earth, lasted but a short
span of time, and then met disaster and extinction. Our modern race is
of this series. We have reason to believe that it differs in quality
from its forerunners chiefly in its cerebral endowment. That its
progress from animalhood to civilization is due to this endowment, is
not questioned, for its victory over environment, its ascendency over
all other animals is plainly due to its superior brain power.
How did this race originate? Like all the other races preceding it? Or
by some aberrant, instantaneous freak of creation? How did it acquire
its characteristic brain? As the bird its wings, as the elephant its
trunk, as the camel its hump, or by a divine act of separate and
special creation? Those who maintain the quarrel over man’s origin are
not those who have familiarized themselves with the history of the
world and its creatures; they are not the astronomers, the geologists,
the biologists, the anthropologists or the archeologists. They are
clearly those who prefer believing to thinking, the traditionalists,
good men mayhap but not necessarily wise. In the earlier days of
science (it is only four or five hundred years old), its devoted
labourers were persecuted by Church and State. They had to give
respectful attention to criticism or else perish by fire and sword.
But, as we have advanced slowly from religious persecution and the
auto-da-fé to mere intolerant and wordy remonstrance, the scientist
has paid but scant attention to these quarrels. He feels that as they
are not of his making, neither are they his concern. Perhaps he is
not quite right there. To be sure, he is criticized, not wisely but
too well, and for the most part not quite fairly. We have criticized
him for an assumed lack of reverence, but even more for his obvious
indifference to our criticism. This has justice in it for, though his
indifference to criticism may be excused, the ignorance upon which
this criticism is founded should be his first concern, for the man
of science is the teacher and ignorance is his very opportunity.
Heretofore, however, he has seen his opportunity too narrowly, for he
has been content to teach only the few embryo scientists apprenticed to
his own particular field. He has not, until very lately, realized that
his hard-won knowledge is far more needed and therefore far more owed
to those who are most ignorant of it, in short, to the great mass of
men and women outside the scientific world.
“You are irreligious,” said his critics. “You have been weighed
and found wanting in that devotional attitude we find essential to
humanity. You do not even listen to our reproaches. You are irreverent!”
For the most part, there has been no answer. The men of science have
been strangely preoccupied with their own business of finding out
all they can of their fellow man, of his nature, his origin, his
difficulties, his dangers, and of his predictable future, all in the
faith that such knowledge will ultimately benefit mankind.
Now at length one of them has made rejoinder to these protests.
He admits that he has been preoccupied, especially so in the past
twenty years, with laborious but fascinating research into just these
questions so vitally concerning his fellow man. He admits that he had
not thought his scientific gleanings would interest any but scientists,
but he denies irreverence and insists that neither he nor any other
who spends his life in studying man and his place in nature could lack
reverence. He cannot find himself entirely in accord with any of the
eleven surviving religions which guide the lives of many men to-day.
The twelve extinct religions of the past also leave him unsatisfied.
Nevertheless he worships devoutly, though in a temple transcending in
significance and beauty any wrought by the hand of man. His devotion is
no mere lip service expressive of the self-protective instinct, but one
that takes form in labour. In spite of disappointment and hardship, he
has persevered through years in that labour, with the single object of
gaining a deeper understanding of man and his place in nature.
It is now our turn to admit error and ask if we may not share in the
fruits of his research--even though our understanding has thus far been
alien to his field of labour, even though our path has not led us to
his temple, even though we have not been aware of his devotion. We
urge him to speak to us, not as to scientists, but as to his fellow
creatures, fellow citizens and fellow sufferers. We urge him to speak
to us plainly, believing that whatsoever has value in human knowledge
may be simply told.
With some hesitation he has consented. He has chosen to speak to us
of the brain, as the most direct approach to the comprehension of the
nature of man. He points out that this master organ of life holds the
secret of human success, that its function is human progress, its
neglect human disaster.
The immensity of the retrospect of his story will create in us the
wholesome effect called humility. The prospect he pictures is fraught
with the terror of what may happen, but it also holds forth inspiration
to courage and is golden with hope. No man can follow this account
without being inspired by a vision of the dawning of a new era of
progress, not an era of greater possessions but of better use of those
already possessed; of better relations between peoples and races; and
being sobered by a realization that this hope lies in developing still
further the efficiency of the master organ of destiny, through training
and education.
The scientist speaks. He tells what he has seen and heard and read
through the long pilgrimage of years, searching for the truth, and
he gives us the fruit of these labours, simply and accurately. But
scientific accuracy and matters of fact are only his raw material. They
are woven into the fabric of a true story, vibrant with adventure,
warmed by the love and reverence of the humanitarian, and illumined by
the prophetic imagination of a poet.
This tale of man’s emergence is fascinating, inspiring, stimulating,
but when it brings us to the climax of the present it becomes a
challenge. We are faced by an awful question. Shall the glorious race
of modern man sink into oblivion, as all the preceding races have sunk,
or may he save himself from chaotic ruin? If he is to be spared for
further progress to greater heights of happiness, he must take heed
of his own history, he must value his forebrain as his master organ
and set himself diligently to develop its powers more fully than ever
before. To this end he must discard the last bit of fundamentalism,
and the false security of all superstition; he must learn to depend
courageously on his own power to understand and control himself; he
must give up superhuman sanctions for evils that his intelligence has
long since discarded. Knowledge must replace superstition--else the
embattled hosts of the world will again be at their bloody work of
extinction, praying to the same god, using the same old prayers. It is
only by increasing the scope of his forebrain through self-knowledge,
training, and education that man can save himself from the old pitfalls
from which neither the old nor the new religions have heretofore saved
him. It is only thus, through understanding, that he can ever hope
to make full use of the forces of growth and change which we call
evolution. But our scientist gives us reason to hope that through
intelligence, itself a product of evolution, man may yet not only
escape destruction by these forces but may even go far toward gaining
a mastery over them which will insure the progress of his race toward
planes of usefulness and happiness as yet undreamed of.
It is indeed time that we think of ourselves as men in the making
and cease to consider ourselves as gods and the lords of a finished
creation.
AUSTEN FOX RIGGS.
Stockbridge, Massachusetts,
October, 1929.
CONTENTS
PAGE
FOREWORD v
CHAPTER
I. PRIMITIVE ANCESTORS 1
Origin and Early Days of the Brain
II. ANCESTORS BEFORE THE APES 24
The Brain from Fish to Man
III. MAN IN THE MAKING 51
Human Progress from Prehistoric to Modern Times
IV. EDEN OR EVOLUTION 85
Genesis and the Origin of Species
V. BIRTHPLACE AND EARLY BEGINNINGS OF MAN 107
Influences of Forest and Plain on Brain Development
VI. DAWN OF THE PRIMATE BRAIN 129
The Lowest of the Monkey Kind
VII. ON THE WAY UPWARD 152
Brains of the Old World Monkeys
VIII. MANLIKE TENDENCIES 168
Brains of Gibbon and Orang-Outang
IX. HUMAN IN MINIATURE 186
The Brain of the Chimpanzee
X. ALMOST HUMAN 212
The Brain of the Gorilla
XI. HUMAN AT LAST 239
The Brain of Prehistoric Man
XII. IMPLEMENTS OF HUMAN SUCCESS 267
How the Hand, Foot, and Brain Led the Way to Humanity
XIII. ESTIMATES AND VALUES 301
Assets and Liabilities of the Human Brain
XIV. THE FINAL TEST OF THE BRAIN 330
World Coöperation and Recivilization
THE MASTER OF DESTINY
CHAPTER I
PRIMITIVE ANCESTORS
ORIGIN AND EARLY DAYS OF THE BRAIN
Since every well-arranged biography should start at the beginning, we
may first inquire into the origin of the brain. The early history of
such an important organ must be closely interwoven with the genesis of
man. If man were the result of a separate creative miracle, so also was
his brain.
But we are not obliged to accept this view which attributes the
universe and all living things to creative miracles. There is another
and equally reasonable possibility. We may, for example, assume that
man and all else came into existence by that process of continuous
change and progressive development called evolution. We have excellent
grounds for accepting such an assumption. Astronomy, geology, biology,
chemistry, and all of the sciences relating to mankind have revealed
the essential facts. Any other interpretation must disregard or
repudiate this convincing record. With such a record as this to guide
us we may turn our attention to the origin of the brain.
_Earliest Forms of Animal Life_
The inception of life on our planet was simple in the extreme. The
earliest animals, although well organized, possessed no special organs
in the strict sense. In the beginning there was nothing which could be
specifically called a stomach or a heart, a lung or a kidney. Certainly
there was nothing even remotely resembling a brain. The business of
living was transacted within a single cell. This cell was so small
that it could not be seen by the naked eye. Each of these cells was
sufficient unto itself. Each played its own separate part with a simple
programme of existence. Each was required to get its own food, to carry
on its own chemical activities of digestion and elimination. Finally,
after it had been successful in this remarkable process, it was called
upon to produce offspring, to perpetuate its species. This last act
was the crown and climax of its life, for in this way it conferred a
material immortality upon its kind.
The amœba, among living animals, is a good example of this simple
life. It is wholly intent upon carrying on within itself the earliest
traditions of existence. All of its life is conducted within a
single microscopic cell, which is at once its office and workshop.
It has nothing in its make-up that could in the ordinary sense be
called an organ. In such amœban animals as these there seems to be
nothing progressive, nothing to suggest the possibilities of further
advancement. Each amœba might, if such a thing were possible, look back
over a long line of ancestors exactly like itself. In looking forward
it might see no great possibility of progress. Perhaps it might reach
the more specialized conditions of its present-day relatives with
contractile threads in their substance and vibrating hairs by which to
move themselves about. At best the outlook of the amœba for progress
was restricted within very narrow limits.
_Familiar Animals of Earliest Type_
Certain events in the long history of these little animals have
acquired much human interest. At times some of these simple lives
become strikingly dramatic. Their monotonous existence is changed
and they pass through certain exciting phases. Such a drama is often
enacted when certain amœbæ gain entrance into the body of another
animal and there become parasites. The other animal may be some
huge beast or even man himself. One unpretentious amœba (_Amœba
histolytica_), if it gains entrance into the intestinal tract of man,
may cause amœbic dysentery and abscess of the liver. Another single
cell animal (_Trypanosome Gambiense_) living in the blood of certain
cattle is often conveyed by the tsetse fly to human blood where it
produces the fatal disease known as “African sleeping sickness.”
This small animal claims hundreds of thousands of victims a year. In
tropical Africa its devastations go on unchecked over an area of more
than a million square miles. In this region sleeping sickness kills
as many persons as all other diseases combined. From five to seventy
per cent. of the inhabitants in different localities are stricken.
Cattle, horses, and other domestic animals cannot be kept because of
this disease. On this account, and also because the area in which
the sickness rages is extremely fertile, it has been said that the
conquering of this malignant protozoan would be equivalent to the
discovery of a new continent.
Even better known are the several acts in the cycle of the _plasmodium
malaria_. This protozoan animal is often borne by the Anopheles
mosquito and injected into the blood of man. Then follows the familiar
series of pathological events consisting of chill, fever, and sweat,
called malaria. In certain respects it seems like retributive justice
when this animal is injected into the body of man to cure the effects
produced by another microörganism. The other organism is the spirochæte
which causes syphilis. It often produces changes which destroy the
human brain in consequence of a disease known as paresis. Many other
protozoan animals are parasites, but in the main they live and have
lived simple, unobtrusive lives.
Notwithstanding their apparent simplicity of structure and action,
these minute animals, like all other things, have been subject to
the influence of continuous change. They have responded to this
influence in different ways. In many instances, through generations of
reproduction, they have effected combinations and recombinations of
their essential constituents out of which have emerged modifications of
their original structure. Often these changes have proved progressive
and contributed to more complex modes of living. Often they have been
regressive or non-progressive. It was the progressive modifications in
these earliest animals that were of utmost importance to the origin of
the brain. This organ was not yet in sight, but adaptations working
toward it were soon to appear.
_Critical Changes in Animal Existence_
In the course of time certain critical changes took place in the
lowly scheme of animal existence. These were distinctly progressive
changes. Some of the single-cell animals began to live in colonies.
Circumstances thus conferred upon them a community life. They began to
exist in close contact with others like themselves and were compelled
to forego their simple, independent habits. They were, in fact,
actually joined to each other by rather slender bonds of their own
vital substance--protoplasm. This was an epochal stride forward. It
was the first step which led to progress. In some instances it brought
about entirely new relations between these animals and the world in
which they lived. Now, since these small cells were grouped together as
colonies, each individual cell lost much of its own independence. Its
interests became, in some degree at least, the interests of the group.
If, as a single cell by itself, it had been thoroughly self-contained,
now it was necessary for it to follow the needs and inclinations of
its neighbours. It was forced to observe the conventions and habits
of its colony. This condition of affairs exists in what are known as
the colonized protozoans. In addition to the advantages of community
life there was another and far more important reason why this new kind
of existence was a critical step. It introduced for the first time
the principle of differentiation or class distinction. A division of
labour was thus made possible. Some of the cells in each group were
forced to take up positions on the outer surface of the colony. Others
occupied places inside of the group. This arrangement immediately
created a distinction between “outer cells” and “inner cells.” It was
destined to have far-reaching consequences because it established a
difference in the responsibilities of two great classes. The outer
cells made an immediate and direct contact with the world. They were
nearest to the water, to the light, and to all of the outer chemical
substances necessary for living. They were like guards and outposts
about a camp, defending the colony from adverse influences. They might
be likened to the first line of battle in the aggressive struggles for
life, acting as foragers and procurers of food. The rôle of the inner
cells was different. Their contacts with the world were more indirect
and established largely through the outer cells. Their offices were
especially confined to the inner workings of the colony. They became
the germ cells whose function it was to insure the immortality of the
species. This arrangement was a momentous advance in the direction of
progress. It was particularly momentous because it laid the foundations
upon which all of the great developments in the animal world were to
be built. In a certain way, it was also a prophecy, for it foretold
the coming of animals that were to follow the protozoans. These
newcomers, the metazoans (animals which came after the first forms of
animal life), were to possess a body with outer cells engaged chiefly
in the efforts of life, while the inner cells would be particularly
concerned with the essence of living, such, for example, as digestion,
assimilation, and circulation.
This remarkable process of class distinction among cells developed new
and useful methods in living. It brought about a division of labour in
the business of life. Different parts of the animal now had different
obligations to fulfil. Some parts served to move the body about, some
were employed in digesting food, some in eliminating waste, some in
breathing and circulation, some in reproduction. In the end, this
division of labour resulted in the formation of a body made up of many
different organs, each having its own particular responsibilities.
We may find an excellent example of the very earliest stages of this
division of labour in Volvox, one of the colony-forming protozoans.
Most of the colonized cells of this minute animal are on the outside,
forming a hollow sphere. These cells are equipped with minute hairs
or flagellæ which, by their constant motion, keep the animal rolling
around in the water like a hollow rubber ball. In this manner it seeks
and finds its food, and thus also it may escape when threatened. But
all of the cells of Volvox are not on the outside. A number of them are
tucked away from the actual surface of the animal. These are the sex
cells to which is entrusted the important duty of reproduction.
_Early Influences at Work to Form the Brain_
Even by this time in the history of the earth, although animal life had
been developing for millions of years, there was no sign of anything
like a brain. The forces, however, which would eventually bring such
an organ into existence were already at work. Perhaps from this great
distance it may be difficult to recognize the exact nature of these
forces as they began to act at this particular stage of life. They were
present nevertheless, faintly discernible like the first streaks of
dawn which precede the sunrise. This figure of speech may seem to imply
that in the end the brain was the actual sun destined to rise above
the horizon of animal life and ultimately to dominate all progressive
achievement. The rest of this biography must prove whether this is an
extravagant figure or not. One important influence behind those forces
that eventually produced the brain stands out clearly. It seems to have
been the direct result of that class distinction among cells which
caused such effectual division of labour. With this subtle influence at
work it required one further critical step to set in motion the events
which were to end in the formation of a brain. This step was taken
when the sponges (_Poriphara_), the simplest of metazoan animals, came
into existence. They differed from the protozoans, even the colonized
protozoans, because their bodies were more complexly organized.
The individual cells forming them had lost most of their separate
independence. All of these cells were now incorporated in a single
living individual, and each cell was subordinate to the interests of
the whole.
Cell distinction had become still more important because of the
increase in size of these animals. The outer cells now formed a
covering or skin called the “ectoderm.” The inner cells constituted
the wall of a cavity, which might be likened to the lining of the
stomach. The lining is called the “entoderm.” Many minute openings
or pores in the outer covering established communication by means of
small canals with the inner cavity of the animal. Through these pores
water is inhaled and carries with it particles of food into the inner
chambers. These particles are absorbed, and the water is then exhaled
through a larger opening called the “osculum.”
It was at this critical point that a decisive factor leading to the
formation of the brain made its appearance. Some of the deep cells
around the pores and outlets of the sponge formed “muscles.” In many
respects this was a new device, and the sponges become especially
interesting because of this innovation in animal life. The innovation
itself resulted in a special machine for producing motion; namely, the
muscle cell. Such muscle cells in the sponge are extremely simple. They
form rings around the pores and the outlets which, by contracting,
regulate the flow of water through the animal. But such muscle action
as this is extremely important because if the water in the sponge
contains an abundance of food particles, muscular contraction prevents
too rapid outflow. This slowing of the ex-current stream, among other
things, allows more time for absorption and digestion. The muscles in
different parts of the sponge act independently. Each one is, so to
speak, a free agent, occupying its position at its own particular pore
or outlet. If, however, it became necessary for all of these muscles
to contract at the same instant in a concerted effort, let us say, to
make the sponge move, there would be no mechanism to assure harmony
of action. The muscle cells at each outlet would react according to
their own inclinations--some relaxing, others contracting. Confusion
of action could scarcely fail to result. The sponge, however, does
not need to move about in order to get its food. Being stationary, it
obtains its nourishment by sucking the water through its pores, and by
regulating the flow the muscle cells do all that is required of them.
_A New Motor Device_
Simple as is this muscular equipment, it possesses great possibilities
for further development. It clearly indicates how such mechanisms for
producing motion might be expanded to create all of the surprising
varieties of motors which in time enabled animals to move about over
the earth, in the water, and through the air. It is true that the
simple strands of muscle in the sponge are far from powerful; but when
a number of muscular strands are collected together they may take form
in such muscles as the biceps of the arm, the great extensors of the
leg, or those covering the entire body.
The presence of the muscle cells created the need for a nervous
system to control and regulate their activities. In order to act
together muscles require a supervisor. The first important step in
this direction was taken when certain simple animals like hydras
and sea anemones (_Metridium_) made their appearance. These animals
are equipped with muscles in several parts of their bodies. Some of
them, unlike the sponges, have the power to move about a little,
crawling slowly like snails. They are also capable of moving their
many tentacles, and thus are able to reach out and grasp food. All of
these movements call for the action of the many different muscles. The
sea anemone has thirteen different sets of such muscles, the exact
coöperation of which requires the closest harmony of action. Each part
must be mutually adjusted to the others. It must act in the right
rhythm and with the proper force. Such delicate adjustment as this
could not be left to chance. It needed an adjuster and regulator. It
required also a system of communication between the cells in order
that each might sense how the others were acting during any given
interval of time. In consequence of these requirements many cells were
specialized as timers, signallers, and dispatchers. They acted like
independent telephone stations, each serving separate districts; such,
for example, as the individual tentacles of hydra or of sea anemones.
These separate stations were known as nerve cells. _In them the first
elements needed for the origin of the brain made their appearance._ At
first they were scattered and had limited communication by means of
slender strands, the nerve fibres. There was as yet no central operator
for receiving and routing their messages which were transmitted rather
diffusely by a loose nerve net.
_Foundation Stones of the Brain_
In spite of this apparent simplicity, these nerve cells were the
foundation stones of the brain. Scattered as they were, they lacked
that unity of action which is the real secret of nerve power. A more
constructive plan for utilizing their capacity was requisite at this
stage. Such a plan was eventually forthcoming. It was exactly what
might have been expected in the progressive development of any good
business concern; namely, consolidation. In effect, it was a merger
uniting the separate nerve units into one centralized system. How
this merger was brought about may be recognized in such animals as
the jellyfish (_Cœlenterates_). In them the body equipment consists
of an outside layer called the “exumbrella,” and an inner layer, the
“subumbrella.” In the latter the older arrangement of the nerve cells
as scattered, more or less independent stations still persists. These
stations form a net of communication on the under surface of the
animal. But where the subumbrella joins the exumbrella, making the rim
of the jellyfish, the nerve fibres and the nerve cells form a nervous
ring entirely surrounding the animal. This is the first time in the
history of animal life that an actual central nervous system makes
its appearance. This ring of nerve fibres and cells acts as a central
receiving and dispatching station. It is a central office for receiving
information from the outside world and a dispatcher for sending
orders to different portions of the animal so that all parts may
coöperate harmoniously. Certain special organs develop along the rim
of the jellyfish, whose functions have some bearing upon the sense of
direction. These structures are known as the marginal sense organs or
“lithocysts.” They are in direct communication with the central nervous
system. Certain other sense organs are also present in the form of red
or black specks of pigment at the bases of the tentacles; they are the
“ocelli,” which are sensitive to light and are, in fact, the simplest
form of eyes. Thus, in such low forms of animal life as the jellyfish,
the first signs of special sense organs made their appearance, and the
nervous elements were for the first time organized to form a central
governing mechanism for the animal.
_Nerve Concentration in Forming the Head_
Following the merger of the scattered nerve cells to form a central
system, the process of developing a brain had opportunity to advance
along another new line. The circular nervous system of the jellyfish
passed through many modifications as it adapted itself to the form
of different types of lowly animals. The great impulse thus imparted
toward the formation of the brain veered off in numerous directions
until a new and decisive change occurred in the arrangement of the
muscles. At this juncture certain animals appeared whose bodies were
much elongated and slender. Their muscles were arranged in straight
rows, one behind the other. Such an arrangement had definite advantages
for transportation, and these advantages were utilized by such animals
as the flat worms (_Platyhelminthes_). Many of the nerve cells and
fibres became concentrated in the head end of these animals. This head
region in a general way took the lead in directing the activities of
motion and transportation. It also had centralized in and about it
many of the most important structures of life. The animal at this
critical stage now possessed a head and a body. In the broadest sense
the development of such a head may be likened to the creation of a
definite executive office within which was established a supreme organ
to preside over the rest of the body.
Further concentration of nerve cells in the head of the animal was the
next step in this constructive process. This advance added materially
to the centralization of nerve power, which was the keynote in the
formation and growth of the brain.
If this process of successive upbuilding seems mysterious and almost
miraculous, especially from its feeble beginnings in a single cell,
it is scarcely more remarkable than the commonplace miracle that has
resulted in the development and birth of every newly created animal
since the dawn of time. The offspring of each species--fish or fowl,
beast or man--has its beginning in a single cell. It passes through
stages of cell colonization, of class distinction among cells, and of
specialization of organs for the various functions of life.
In the main, these two processes have run parallel in their programmes
of construction--the beginning and development of life on our planet,
the beginning and growth of every new life created. Summarized thus
briefly, these successive stages necessary to bring the brain into
existence may appear unimpressive. But when we consider that each
forward step required ages for its achievement, we may appreciate that
this was indeed a marvel of progress. From nerve cell to brain is a few
short words in print; but it required millions of years for the slow
advances to attain even the humble level of the flat worms.
_Development of Better Brains_
With the head at length in its proper place and the most simple
kind of brain installed within it, vast horizons of life still lay
ahead. Better mechanisms were needed for a more successful struggle
with existence. More capable motors were required for more efficient
locomotion. These improvements came after the passage of long intervals
of time. By degrees more highly developed animals, such as bees, ants,
beetles, or other insects, lobsters, crayfish, and shrimp, began to
appear. Their brains were much better organized than those of the lowly
worms. The special senses of sight, smell, and taste became highly
important, while the central organ which presided over all activities
acquired a remarkable complexity in its structure.
How much these animals gained from their better brain power is clearly
seen in their behaviour. The achievements of ants and bees and beetles,
as well as many other insects, have long been a matter of wonder, a
theme of interest and fascination. If we credit these animals with
highly capable brains, it is their just due. One detail in their
organization, however, became a serious handicap to them in their
further development. The passageway from the mouth to the stomach ran
directly through the centre of the brain. If the brain grew extensively
it would encroach upon the gullet, ultimately shutting off the only
channel for food. This embarrassment actually overtook many insects
like the mosquito. Here the brain became large. The tube connecting
the mouth and the stomach was thus reduced to a fine calibre, and
the animal was forced to depend upon the highly concentrated fluid
diet obtained by sucking blood. Coarser forms of food could not pass
the œsophageal ring which the brain forms about the gullet. Thus the
stomach and the brain came into serious competition with each other.
If the brain grew larger the stomach would be deprived of food. In
consequence, this situation created a dangerous hazard to life.
_Advent of Backboned Animals_
In addition to this stomach-brain dilemma, animals such as the insects
suffered from another handicap because of the outer skeleton which
protected their bodies. This skeleton was in the form of a more or
less rigid shell, as in the lobster, crab, or crayfish. It was to
overcome the effects of such handicaps, according to some authorities,
that the great race of backboned animals came into existence. In any
event, such animals seem to have circumvented the difficulty of having
a brain which surrounded the gullet. They also overcame the necessity
of carrying a heavy shell about on the outside of their bodies. An
inner skeleton did away with this embarrassment. It is not altogether
clear how or when this transition took place. Many students of this
matter believe that the basis for this change is to be found in the
starfish group of lower animals (_Echinoderms_). Others maintain
that the change began with some creature not unlike the horseshoe
crab (_Limulus_). It is also believed that the animals which served
as the intermediate forms for this advance were the ostracoderms, a
group which has long since become extinct. They are known to us only
through fossil preservations. They possessed, however, so many fishlike
features that they may well have served as the forerunners of the
earliest animals with backbones. Whatever else is in doubt, one detail
of this transition is definite. The brain, already well developed in
certain lower creatures, now received a fuller opportunity to advance
along more advantageous lines. The first gains of this kind are seen in
the fish. Judged by outward appearances the object of such new brain
development was to provide a more efficient regulator for a new and
more efficient kind of animal. The fish, in one particular at least,
showed higher specialization. It was built for speed in locomotion.
The shape of its body, the arrangement of its muscles, the position
of its fins, the design of its head, and the form of its tail gave it
many advantages over lower animals. Equally important were the special
organs by which it sensed the world. The fish possessed powerful and
remarkably constructed eyes. It had most delicate organs for smell,
and an effective apparatus for taste. In fact, all of the senses of
the body were now so thoroughly organized that each one of them had
its own special department in the brain. According to this new type of
administrative organization, an endbrain, an interbrain, a midbrain,
and a hindbrain were established for distinct departmental purposes.
In spite of this better arrangement, there were still decided
limitations in the brain. The most serious of these deficiencies lay
in the mechanism regulating the energy turnover. The fish had little
power to withhold its reactions. Its impressions from the outside world
produced almost immediate responses. Such rapid reactions precluded the
wide range of acts which characterizes more deliberate behaviour.
The brain machinery for the most ample kind of living was not yet
present at this stage of animal development. It did begin to make
its appearance, however, when certain of the fish assumed partial
adjustment to life on land. These adventurous pioneers managed to
crawl out of the muddy waters at times when there was a lack of
oxygen or when the supply of food was insufficient. They set on foot
those progressive changes that gave rise to fore and hind limbs in
such amphibians as the frogs. When these latter animals made their
appearance nearly all of the fundamental problems of the vertebrate
brain had been solved. Nevertheless, there was still the need of
certain expansions in brain power and these, in some part, were
supplied during the age of reptiles.
As yet, however, that handicap of almost instantaneous reaction which
seriously limited the life of fish had not been entirely overcome by
the amphibian or by the reptile. These animals still lacked the brain
mechanisms needed for the deliberate and varied actions of the most
efficient life. They had not yet altogether escaped from the ancient
tyranny of automatic or reflex reaction.
At length the mammals, throughout the different periods of their long
progressive age, introduced the final detail of brain perfection. The
secret of this perfecting detail was the addition of a new mechanism to
the brain never possessed by animals before this time. The great and
new areas of the cerebral hemispheres now came slowly into existence.
With them developed new and greater capacities for action together with
far more effective adjustments to life.
_Vast Ages of Animal Life_
All of these developments reach back a great distance in time, so
great that it is difficult to calculate its exact duration. According
to modern estimates the first animals came into existence about
1,000,000,000 years ago in the Proterozoic period. This period was
followed by the Palæozoic, which began approximately 300,000,000 years
ago, and is known as the Age of Fish. Then came the remarkable Age of
Reptiles, beginning about 200,000,000 years ago, followed by the Age of
Mammals, which commenced in the neighbourhood of 65,000,000 years ago.
The present Age of Man has had a short duration, extending back only
about 1,000,000 years.
Two methods have been depended upon in determining these figures and
the age of the earth. The first is based upon the rate of deposit and
upbuilding of sedimentary rocks. The estimated period required for the
development of each rock layer has provided a time-table for the age of
the different strata of the earth’s crust. The second method calculates
the rate at which common salt is extracted from the land and deposited
in the oceans. Imprints of fossil animals upon the several rock layers
also reveal the age of different strata. The discovery of radium
afforded the latest gauge for estimating geologic time. The physicists
now tell us that former calculations have been far too modest and
that we must go back still further to reach the actual beginnings
of our earth. Their “radioactive clock” indicates that the earth is
1,600,000,000 years old.
During all this vast interval there has been a succession of great
changes in the earth and its waters. Continents have risen above sea
level, to be submerged again. Great inundations of continental oceans
have swept inward and made vastly different land divisions from those
which exist to-day. North America has been more or less widely flooded
by great oceans at least fifteen times. Other continents have been
similarly inundated. Mountain ranges have risen and crumbled away by
erosion. In point of geologic time most of the present mountains are
relatively young. The oldest of these is the Appalachian range which
was formed during the Permian period approximately 230,000,000 years
ago. The Rocky Mountains appeared at the close of the Cretaceous,
100,000,000 years ago, while the Swiss Alps are of much later
development, having been formed at the close of the Miocene about
15,000,000 years ago. Even the Himalayas are relatively young when
compared with the earth’s antiquity. They had not taken on their full
gigantic proportions until the close of the Eocene about 45,000,000
years ago.
According to many authorities, great continental land connections
once existed between Africa and what is now part of South America.
This connecting continent disappeared beneath the ocean long ago. So
also did the land connection between Asia and North America in the
region of the Bering Sea. An important land connection existed between
England and the Continent, across what is now the English Channel, in
Pliocene times. It was present, therefore, at some time within the last
6,000,000 years. Immense inland seas have drained off or evaporated and
left in their places great desert spaces, like the Bad Lands of the
West.
_The Long Upward March Toward Humanity_
While these changes were in process marked alterations in climate
affected the surface of the earth. Glacial ice caps descended from
the poles, later to recede and leave the earth invested in tropical
warmth. Time and again these changes recurred. The crust of the earth,
chilled by intense refrigeration for protracted ages, grew warm again
for equally long periods when tropical vegetation crept up toward
the poles. These changes in vegetation have been accompanied by many
changes in the animal inhabitants of the globe. Species of animals
in profusion have come into existence only to follow the path which
led to extinction. In many cases the forms of life began simply and
progressed by graded stages to greater structural complexity. Man is an
outstanding example of this rule. He began in much simpler form than
that in which he now exists. This relative simplicity is particularly
true of his brain.
Thus, as if descending a long stairway, we may pass by the successive
terraces of the earth’s history toward the beginnings of geologic
time. The expanse of this time is difficult to conceive. From the
inception of animal life in the long Proterozoic Age, throughout the
ages of Fish, Reptiles, and Mammals, man’s brain was in the making.
Irresistible forces molded the various stages of its progress. Species,
genera, families, and even entire orders of animals came into existence
and disappeared as wastage in a great experiment. Yet, through all
vicissitudes of time and change, the long upward march toward humanity
held its place. Ultimately it became the dominant feature in creation.
The advent of man introduced a new era. It remains to be seen whither
the forces moving in this Age of Man will take us. They may be leading
to extinction. The way to such a termination is clearly open to our
race. On the other hand, the brain has made man what he is and may
save him for better things. Its interesting pioneer ancestry, although
extremely remote, has left a well-established record. The history of
its development through the process of evolution in the backboned
animals is still more interesting.