UC-NRLF 



B M 175 



Ice Aejes 

Joseph McCabe 




THE LIBRARY 

OF 

THE UNIVERSITY 
OF CALIFORNIA 

PRESENTED BY 

PROF. CHARLES A. KOFOID AND 
MRS. PRUDENCE W. KOFOID 





.2 



Ice Ages 

The Story of the Earth's Revolutions 



By 

Joseph McCabe 

Author of "The A B C of Evolution," "The Evolution of 
Civilization," etc. 



Illustrated 



G. P. Putnam's Sons 

New York and London 

(Tbe fmfcfterbocfcer press 

1922 



Copyright, 1922 

by 
Joseph McCabe 



Made in the United States of America 




PREFACE 

IN two earlier little works (The A B C of Evolution and 
The Evolution of Civilization), of the same very modest 
proportions as this, I have given an outline of the story 
of Evolution. It is clear from the large circulation of 
these simple manuals that they have met a very real 
want. A good proportion of the workers, for whom in 
particular I write, feel that science means a new and 
mighty mental power in the world. They are asking if 
its broad teaching about man and the universe cannot 
be made plain to them without the use of learned words 
which they have not time to study, and without 
masses of detail which only tire them. 

These short and plain summaries of science en- 
deavour to supply that want. Twenty years' lecturing 
on the subject has educated me in the work of trans- 
lating the language of the laboratory into the speech 
of the fireside. There is no branch of culture (except 
metaphysics, which is not worth it, and mathematics, 
which is for mathematicians) that cannot be conveyed 
in plain speech. I have given the same lecture, on the 
Evolution of Life, one night in one of the leading 
universities of America and the next night to a ragged 
group of children in one of the slums of New York. 

iii 



iv PREFACE 

It is possible thus to teach, not merely science, but 
the most profound, most stimulating, and most recent 
truths of science. "Popular science" is a phrase that 
men of science do not like. Much that goes by that 
name is a loose statement of things that have been 
published in works that are already a little out of date. 
That is not the kind of science I give here. Each of 
these little manuals is based upon the whole literature 
of the subject, in various tongues, and upon the expert 
periodicals for each branch of the subject up to 
the date of publication. The difficulty is, even after 
leaving out what is unsuitable for these works, to 
compress so much matter without leaving it in a hard 
and not easily digested form. A good deal has to be 
omitted, or insufficiently explained. This, it seems, is 
notably the case in regard to my earlier references to 
Ice Ages. I describe them as having played a revolu- 
tionary part in the advance of life on the earth, and 
I am told that this is so helpful, so interesting, and so 
important that readers would like fully to understand 
them and their effects. So here I offer, in the same 
plain, untechnical manner, an outline of the really 
wonderful story of the earth's revolutions. 

J. M. 
March, 1922. 



PREFACE TO AMERICAN EDITION 

A WRITER of large imagination once suggested that 
a being travelling outward from the earth at a 
certain speed would pick up in succession the entire 
past history of our globe. Unfortunately, one would 
have to travel at a higher speed than light more than 
186,000 miles a second; apart from the practical 
difficulties, Einstein has now proved that nothing can 
travel more speedily than light ! 

But science has found a more practicable way of 
piecing together the romance of the earth. Indeed, 
when one reflects, one sees that this patient reconstruc- 
tion out of the crushed and half-obliterated tombs of 
the past is one of the most marvellous triumphs of the 
human mind. The part which Ice Ages have played 
in this wonderful past increases in interest and scien- 
tific importance every year. The whole drama of the 
upward crawl of life is now found to be vitally con- 
nected with the periods of intense cold through which 
our globe has passed in former ages. 

I offer here as a supplementary study to my earlier 
popular accounts of evolution (The A B C of Evolu- 



vi PREFACE TO AMERICAN EDITION 

tion and The Evolution of Civilization) a plain and non- 
technical account of these Ice Ages and how we know 
them, with particular attention to the human interest 
of the subject. 

J. M. 



CONTENTS 

PAGE 

PREFACE iii 

PREFACE TO AMERICAN EDITION v 

CHAPTER 

I. ICE AGES AND DARWINISM . . 3 

II. How WE DISCOVER ICE AGES . .21 

III. THE CAUSE OF ICE AGES ... 38 

IV. THE FIRST Two ICE AGES . . 55 

V. THE MIGHTY PERMIAN REVOLUTION . 73 

VI. THE COLD THAT SLEW THE DRAGONS . 90 

VII. THE ICE AGE THAT MADE MAN . 107 

VIII. THE NEW ERA OF EVOLUTION . . 125 



vii 



ILLUSTRATIONS 

PAGE 

DIRT BANDS ON A GLACIER MER DE GLACE 

Frontispiece 

CREVASSES ON A GLACIER . . . * 28 
THE MAKING OF THE ALPS .... 60 

THE LAST ICE AGE. LARGEST EXTENT OF 
THE ICE-SHEET AND EXTENSION OF THE 
DRY LAND no 



Ice Ages 



Ice Ages 

CHAPTER I 

ICE AGES AND DARWINISM 

THE story of the Ice Ages belongs, in more senses 
than one, to what is called the romance of science. 
Less than twenty years ago there still circulated in 
England a work in which a clerical geologist cheer- 
fully, in fact contemptuously, dismissed "the great 
Ice Age" as "the great nightmare." He appealed 
to the authority of a very distinguished and very aged 
geologist, who, not finding any reference to Ice Ages 
in the first chapter of Genesis, succeeded in closing 
his purblind eyes to the evidence that was pouring in 
from every quarter of the globe. 

The last faint traces of this curious prejudice have 
long disappeared. The nightmare has turned out 
not only one of the most solid of realities, but one 
of the most powerful and important agencies in the 
onward and upward progress of life. There have 
been five great Ice Ages or four definite Ice Ages 
and one long period of very severe chill in the story 

3 



4 ICE AGES AND DARWINISM 

of the earth. Four times at least in the course of the 
earth's evolution the temperature of a region that 
measured millions of square miles slowly and steadily 
sank until the summer sun was not strong enough 
to melt the winter's snows; and the snows gathered, 
hundreds of thousands of feet thick, on the lower 
slopes of the mountains, and hardened into ice; and 
the ice sluggishly flowed, in deep rivers or glaciers, 
down into the valleys and far over the plains, and 
sometimes spread in a vast cake or "cap" that 
covered a whole continent. Far beyond the actual 
ice-field, moreover, was a fringe of territory, hundreds 
of miles broad, which shivered, as northern Siberia 
does to-day, in the biting winds and blizzards that 
hurried from the ice towards the warmer lands. For 
tens of thousands of years at least, possibly for a 
quarter of a million years or more, some vast area 
of the earth's surface was thus converted into a desert 
of snow and ice. That is, briefly, an Ice Age. 

But I have mentioned northern Siberia, and it will 
at once occur to the reader that the preceding para- 
graph is just a picture of our polar regions to-day. 
The ice-caps at our North and South Poles cover more 
than ten million square miles, and round them is a 
broad, bleak fringe of wintry territory. Does this 
mean that we are living in an Ice Age to-day? A 
frivolous person might add, seeing that we have laid 
stress on Ice Ages as means of progress: Do you 
ask us to believe that the lowly Eskimo and the dull 



ICE AGES AND DARWINISM 5 

Siberians, who enjoy the bracing winds from the ice, 
illustrate the way in which Ice Ages contribute to the 
advance of life? 

The questions will help us to fix more precisely the 
part that the Ice Ages have played in the drama of 
earthly life . The polar ice-sheets of to-day are actually 
far larger than the sheets which we can trace in what 
we call the Ice Ages, yet they clearly play no part 
of any importance in the evolution of life at all 
events, in the evolution of human life, for there are 
very interesting developments, due to the glacial con- 
ditions, in the animal world. Man in those regions 
is so absorbed in wringing a scanty diet out of the 
stingy earth that he has no time or brain for anything 
else. We regard the polar regions as deserts, as so 
much waste land, on which the living things of the 
earth might, if it were green field or forest, get on 
with the drama of their evolution. 

But suppose these icy deserts had once been warm 
and fertile areas, with abundant and luscious vege- 
tation and teeming animal populations. Suppose 
these teeming animal populations had had easy con- 
ditions of life warmth and plenty of food during 
millions of years, and had become sluggish and un- 
progressive (or very slightly progressive), as animals 
do in such circumstances. And suppose the glacial 
conditions had crept slowly during tens of thousands 
of years upon this sluggish population. Any person 
can see that, if this is the real history of the polar 



6 ICE AGES AND DARWINISM 

ice-caps, they may at first have provided a mighty 
stimulation of the living population. 

That is, in point of fact, what happened. In the 
rocks of the Arctic and Antarctic circles we find the 
remains of the animals and plants of earlier days, 
just as we find them in the rocks of other regions. 
Two or three million years ago those rocks were 
beds of mud or sand, and the bodies of animals and 
leaves of plants got buried in them occasionally. 
The beds were hardened into stone and the remains 
"fossilized"; and the geologist who accompanies 
arctic explorers learns from them the earlier history 
of the polar regions. Two or three million years 
ago Greenland was as warm as Algeria is to-day. 
Graceful bamboos, gorgeous magnolias, even fig-trees, 
flourished where a vast sheet of ice now eternally 
buries the land. There are high authorities who 
regard the region as actually the cradle of the great 
monkey, ape, and human families. At all events, the 
glacial chill came gradually upon a warm-loving, well- 
fed population; and there was "natural selection" in 
its grimmest form. It was the beginning of the last 
Ice Age. 

In order that the reader may have at the outset a 
clear idea of what we mean by the Ice Ages, I must 
anticipate a little. We say that the Ice Age is over, 
yet these vast ice-caps linger in the polar regions. 
What is the meaning of that? 

We shall see that after each Ice Age the earth 



ICE AGES AND DARWINISM 7 

returns to a genial climate, but not to the temperature 
it had had before. The globe is growing steadily 
colder. Ice Ages are temporary periods of intense 
cold for certain parts of the earth; but, apart from 
them, the globe as a whole is "running down," as it 
were, in point of temperature. Until the oncoming 
of the last Ice Age there was no such thing as really 
permanent ice or snow anywhere on the earth. There 
were no polar caps. Now the poles are permanently 
frozen, and as time goes on as millions of years go 
on the ice will slowly extend towards the Equator. 
We have every reason to know that in time the whole 
earth will be permanently frozen over. So marvellous 
and sure is the vision of modern science that we can, 
if you wish, go even further. Long after all the water 
on the globe is permanently frozen solid, the atmos- 
phere will begin to liquefy. The temperature will 
sink to two hundred degrees (Centigrade) below zero, 
and then our atmosphere will be a sea of liquid air, 
thirty-five feet deep, lying upon the solid ice in our 
ocean-basins. 

But that will be long after "the fretful hour" of 
man is over, and we will confine ourselves to the Ice 
Ages of the past. Cold will one day extinguish all life 
on this globe, but in its earlier stages this advancing 
cold will have done much to stimulate the progress of 
life. We used to think of life in the past as a great 
battle of one living creature against another, for food 
or mates (among the higher animals). We saw that 



8 ICE AGES AND DARWINISM 

a comprehensive, world-wide struggle of this kind 
would test the strength, the speed, the cunning the 
life-qualities generally of animals, and would, by 
eliminating the weaker or more sluggish, tend steadily 
to improve the standard or change the structure in 
each generation. So we said that "natural selection" 
was the great agency of Evolution, as the genius of 
Charles Darwin was the first to discover. 

This "struggle for life" is one of the most obvious 
and elementary facts. It is going on to-day in every 
field and pond, every mile of the ocean and every mile 
of the land's surface, every workshop and every foot- 
ball field, every profession and every system of ideas, 
even among Churches and States. In these latter 
days social or intelligent evolution tends to take the 
place of evolution by combat, but throughout the 
greater part of the development of life on the earth 
there was no social or intelligent evolution. One has 
only to look round and see how pitifully feeble social 
evolution is in our own day, although that supposedly 
intelligent animal, man, has been on the earth for 
more than a million years ! 

We will return to this in the last chapter. For the 
moment it is enough to say that the "struggle for 
life," in the old sense, has been throughout the ages 
just as great a reality as Darwin thought. There 
have been a good many attempts to get away from 
the picture of "nature red in tooth and claw," but 
they are foolish. The teeth and claws would not be 



ICE AGES AND DARWINISM 9 

what they are if there had not been a prodigious 
development of them by use. 

But modern science has something further to say. 
Every year thousands of new facts are gathered in 
the field of nature and sent in to what we may call 
the "clearing house" the universities and learned 
societies. So our general picture of nature is enlarged 
or modified every decade. In the present instance we 
have not lessened our idea of the struggle in nature. 
We have enlarged it. Underlying and overlapping all 
the struggle of individual animals against each other, 
there are two great struggles of the elements. One is 
the battle of land and water. From the dawn of time 
that battle has been waged in one age the oceans 
flooding millions of square miles of the land, in another 
the land rising like a giant and shaking the waters 
from its broad shoulders. 

That has had in every age an enormous influence 
upon the struggle for life of the little pygmies, the 
animals and plants, that lived on the land or in the 
water. It has involved myriads of revolutions in 
their conditions of life, and these have sternly tested 
their life-qualities. But we are not concerned here 
with this war of land and water, except that we shall 
see that it is the rise of the land that explains Ice 
Ages. 

The struggle of the other two elements, heat and 
cold, is not less eternal and important. The cold 
of space about three hundred degrees below zero 



io ICE AGES AND DARWINISM 

(Centigrade) is like a great dragon lying in wait 
for every globe in the universe. For millions of years 
the globes remain hot enough to keep it off. A star 
may blaze for a thousand, or even several thousand, 
million years, but the dragon will close in on it in 
the end. Planets may bask in the heat and light of 
the suns for tens or hundreds of millions of years; 
but, as the fires of the sun sink, the dragon closes in, 
and the living populations of the planets pass into the 
silence. The fires of our sun are sinking, and the 
dragon is slowly approaching. (But be not alarmed. 
There are probably some tens of millions of years 
still for man on this planet.) 

What we have discovered in tracing the Ice Ages 
is that the dragon may get its teeth in, so to say, 
prematurely and temporarily for a matter of a 
quarter or half a million years. To keep up my little 
allegory if the reader is not tired of it the dragon 
seems to be watching the struggle of land and water, 
and every time the land gains a great victory, every 
time it rears its head too high above the sea level, 
there is a long spell of severe cold. There have, as I 
said, been five such periods of what we may call the 
first-class order: five Ice Ages. But there have been 
numbers of smaller uplifts of the land, followed by 
corresponding local chills. There have, in other words, 
been five revolutions in climate, and a large number of 
minor disturbances. 

A revolution in climate, a change from great warmth 



ICE AGES AND DARWINISM 11 

to arctic conditions, is bound to have a profound effect 
upon the living population. From millions of square 
miles the population disappears, and in further 
millions of square miles the vegetation is entirely 
changed and very greatly impoverished. There is a 
struggle for food, a vast destruction of life from cold 
and hunger, a demand for new habits and new organs. 
But all this will be fully explained and illustrated in 
later chapters. It is enough for the moment to say 
that during an Ice Age the living population of a very 
large part of the earth passes through a long and 
terrible ordeal. A very large proportion of it is 
annihilated. A few types survive by developing new 
structures or habits to meet the cold conditions; and 
we shall see that in a considerable number of cases 
these changes mean a very important advance in 
organization. 

Now all this is a splendid enforcement and develop- 
ment of Darwin's fundamental idea. Darwin wrote 
more than fifty years ago, which is as much as to say 
that he was certainly wrong on many points. The 
most distinguished man of science of our own day 
would laugh at the idea that he is right on every 
point that time will make no change in the brilliant 
theories which seem to him to give the best explana- 
tion of the facts as we know them at present. Fifty 
years ago the facts were not known nearly so well as 
we know them to-day. The progress made in observa- 
tion in half a century is colossal. Moreover, Darwin 



12 ICE AGES AND DARWINISM 

was a pioneer in a new field of speculation. For 
twenty years he worked without any check of criticism 
whatever upon his ideas. 

In the circumstances it is marvellous how right he 
was. The man who would try to prove him right in 
everything would be as foolish as the man who cackles 
because he was wrong in some things. It is, however, 
interesting to know that the main position taken up by 
Darwin was sound. Even distinguished men of science 
have in recent years spoken as if "Darwinism" were 
dead and natural selection discredited. The general 
public is puzzled, and a few words on the subject may 
be welcomed. 

If Darwinism means anything, it means that the 
various species of animals and plants were evolved by 
means of natural selection. Darwin, a very retiring 
and diffident man, would not have cared to see any 
scientific gospel set up with his name attached to it; 
but, if he were asked to give the essence of his theory, 
he would simply have quoted the title of his great 
work: "The Origin of Species by means of Natural 
Selection, or the Preservation of Favoured Races in 
the Struggle for Life." There is no need to say what 
that means. In every generation the individuals differ 
greatly from each other in strength, health, speed, 
cunning, sight, and so on. The destructive agencies 
of nature weed out the less gifted, and so "preserve" 
or "select" the better endowed. Thus the type is 
progressively changed. 



ICE AGES AND DARWINISM 13 

In working out this theory Darwin relied on two 
beliefs which have since been sternly challenged. 
He thought that what are called "acquired modi- 
fications" for instance, changes of organs acquired 
by the individual during life by the use of those 
organs (like the strength of a footballer's leg) might 
be handed on to the next generation. This is now 
generally denied, though there are eminent men of 
science who still hold it; but it is not an essential part 
of what any instructed person would call Darwinism. 
It was the general belief of scientific men in Darwin's 
time. 

Secondly, Darwin thought that progress in the 
making of new species was very slow and gradual. 
For instance, the power of a hawk's wing or the 
keenness of its eye was developed by very small 
increases of strength and keenness during a long 
series of generations. Most people would still think 
the same in this case, but there are other changes 
which are not so easily explained. A new theory, 
Mutationism, has arisen, and it demands larger 
changes (from parent to child) than Darwin generally 
admitted. In his own book he recognized "abrupt 
and great variations, " but he thought that they were 
rare. That question is still undecided. The new 
theory has its difficulties and weaknesses, and the 
public ought not to be intimidated by the dogmatic 
tone of some who write on it. It is not yet established, 
but it is the more favoured theory. 



14 ICE AGES AND DARWINISM 

These are the real corrections, or possible correc- 
tions, of Darwin. His fundamental teaching is sound. 
Some men of science of our day have evidently never 
read Darwin. They talk as if he did not know that 
natural selection is, as far as new species are con- 
cerned, negative. What nature positively does is to 
destroy the less fitted to survive. It is a sort of 
poetry to say that nature " selects" the fitter. How 
any one can suppose that Darwin did not see that is 
puzzling. He doubted himself if the term was the 
best possible, but he wrote to A. R. Wallace that, 
"with all its faults," he could see no better. 

Others point out that natural selection is "not 
omnipotent," or not the only cause of evolution. As 
if Darwin had said that! On June 5, 1860, he wrote 
to Hooker: 

"I have never hinted that Natural Selection 
is ' the efficient cause to the exclusion of the other * 
i.e., variability from climate, etc. The term 
selection implies something i.e., variation or differ- 
ence to be selected. " 

In 1865 he wrote again to protest emphatically against 
the idea that he "attributed nothing to variation in- 
dependently of Natural Selection. " 

These passages, finally, answer the writers who say 
that Darwin looked only to action from without, and 
did not realize that the agency within which causes 
the variations is equally important. He wrote to 



ICE AGES AND DARWINISM 15 

Hooker in 1857 that "external conditions do by 
themselves very little." He thought that external 
changes provoked changes in the animal, but he 
reminded Hooker "how profoundly ignorant we are 
on the causes of variation." In his last years he was 
very busy with this "most perplexing problem," and 
he confessed that it "baffled" him to the end. He 
was very far from ignoring the problem of the origin 
of the variations which nature "selected." But 
embryological science was still imperfect when he 
died. In fact, it is still very obscure on that side. 
Mendelism has thrown much light on the machinery, 
but it is not yet established as a general theory. 

This little account of the rights and wrongs of 
"Darwinism" may be useful to some readers. The 
truth is that Darwin left open, all his life, the question 
what agency caused the young to differ from their 
parents. His great theory was that such differences, 
however they arose, were the material for making 
new species, and that the machinery which made new 
species out of them was natural selection. That is, if 
one may say so, truer than ever. 

Instead of the work of natural selection being 
reduced to more modest proportions by our discovery 
of Ice Ages, it becomes more important than before. 
They are natural selection in its most imposing form. 
It is as if the agencies of nature took the population 
of a whole continent and put it through a drastic and 
searching test for a hundred thousand years. Let 



16 ICE AGES AND DARWINISM 

me illustrate it by anticipating one point. In the 
fifth chapter we shall see that the age of the Coal 
Forests ended in an Ice Age. This affected a con- 
tinent which then stretched from India to Australia 
and South Africa. At the beginning of the Ice Age 
the highest animals on this continent, or anywhere in 
the world, were clumsy reptiles. By the close of it 
some of these reptiles had evolved into mammals and 
birds, and the overwhelming majority of the animals 
had been annihilated. If that is not natural selection 
whatever view we take of the embryonic machinery 
the word must have a new meaning. It is, at all 
events, precisely what Darwin meant. 

Three times since the first living things quitted the 
ocean and began to flourish on the land, the population 
of the earth has passed through one of these mighty 
selective ordeals. At the close of each, new and higher 
types of animals and plants were found on the earth; 
and no one would be quite so foolish as to say that it 
was a mere coincidence. There are some mostly 
philosophers, but a few men of science who would 
attribute evolution to an internal principle, a "vital 
principle," which has worked steadily up from the 
lowest level to man, moulding matter to its successive 
designs. It is hopelessly unintelligible how a principle 
which is unconscious, and therefore acts blindly, can 
be credited with such work; but in any case it does 
not lessen the action of natural selection in the great 
Ice Ages. 



ICE AGES AND DARWINISM 17 

Furry and feathery things, with warm blood, 
appeared during an Ice Age, because the condition 
of the world permitted and favoured them, slaying 
their fur-less and feather-less rivals. The hardy pine 
and yew and fir appeared during the same Ice Age 
for the same reason. The great reptiles of long ago 
quitted the earth because an Ice Age slew them; and, 
as this left the Northern Hemisphere to the higher 
birds and mammals, they were "selected." The oak 
and beech and holly came during the same Ice Age 
for the same reason. Finally, man was brought to 
face the same stern test of an Ice Age, and we shall 
see that it put him on the path of progress. 

This is the story we propose to tell, once we have 
explained how we know of these Ice Ages, what 
caused them, and at what precise points in the earth's 
chronicle they occurred. There is only one further 
preliminary remark to be made. 

I have occasionally spoken of the Ice Ages as 
"revolutions," and some will wonder whether this is 
not a frivolous use of words, if not an outrage on the 
dignity of science. Well, the word is not mine. It 
is the word applied to Ice Ages by the leading geo- 
logical writers of our time. They were revolutions 
in climate. Before each of them the earth had been 
for millions of years innocent of ice and snow, of 
glacial currents in the ocean and deadly blizzards on 
the land. That is an essential point to bear in mind. 
The Ice Ages supervened upon long periods of what 



i8 ICE AGES AND DARWINISM 

we might call perpetual summer. They came upon 
a population softened by long indulgence, by millions 
of "years of plenty." That is why they were so 
effective. 

They were revolutions in climate, and in a sense 
they were revolutions in biology. Here some horrified 
reader may wonder if science is now adding to its 
misdeeds by encouraging "Bolshevism." Have we 
not been told for decades that on the social side the 
message of science was emphatically, Evolution not 
Revolution? Science was supposed to know the laws 
of life intimately, since it embraced fifty million years 
or so of life-development. And we distinctly under- 
stood from it that the fundamental law was: "Slow 
and steady progress." We were to advance by inches 
nay, millimetres not yards. What are we to say 
to the young man in a hurry who gets hold of one of 
the most authoritative manuals of modern geology 
say, by Professor Chamberlin or Professor Schuchert 
and finds the dreaded word "Revolution" used 
repeatedly, if not standing for the very greatest 
advances that have been made in the march of life? 

I have just said that Darwin's idea of minutely 
slow and gradual change is very much challenged 
to-day. It is not merely the geologist who departs 
from the old idea. Mutationism is very widely 
accepted, and it means that progress takes place by 
larger changes ("mutations") longer steps, as it 
were than Darwin thought. 



ICE AGES AND DARWINISM 19 

What the geologist means, however, is something 
different. He may be either a Darwinian or a Muta- 
tionist. He may think that the transformation of 
a reptile into a bird was accomplished by adding 
together a series of dots or a series of dashes to 
make an illicit use of the Morse code. That is nothing 
to him, and we are going to imitate him in his work. 
When he speaks of "revolution," he means more 
rapid evolution than had preceded. 

There is really no antithesis between evolution 
and revolution. All the changes that take place are 
evolution. The French Revolution was a piece of 
political evolution. So was the Russian. But there 
is slow evolution and rapid evolution. Science now 
recognizes that life has by no means advanced at an 
even pace. During Ice Ages, particularly, the pace 
of advance has been much more rapid than during 
the "golden ages" which went before them. Man, 
for instance, made more progress in the last fifty 
thousand years of the last Ice Ages than during the 
first million years of his existence. It was a revolu- 
tionary period. 

Yet let not the social student rush to conclusions. 
The revolutions of which we speak in geology are 
portentously slow, if we measure them by human 
standards. The whole story of human civilization is, 
in the most liberal estimate, a matter of ten thousand 
years. You might, by a stretch of imagination, call 
that entire story a revolution a revolt of intelligence 



20 ICE AGES AND DARWINISM 

against the stupid older order. Yet this long period 
is not one-tenth as long as an Ice Age. That is where 
any attempt to make a parallel with man's affairs fails. 
But we will return in the last chapter to these ques- 
tions of social philosophy, which arise out of our 
subject, and will now proceed to tell how we know that 
there were Ice Ages in the past. 



CHAPTER II 

HOW WE DISCOVER ICE AGES 

THE first difficulty that occurs to the unscientific 
person who is told about Ice Ages is that he cannot 
see how we can possibly know of changes of climate 
in former days. It is difficult enough to say whether 
there has been any change in the climate of England 
during historic time. We get a reference to it once 
or twice in a century in Pepys's Diary, or in some 
incidental notice of the weather in a chronicle of war 
but we have very little knowledge of it even for 
the last thousand years. How, then, can we say 
confidently that there was an Ice Age in Europe 
a quarter of a million years ago? How are we to 
believe Australian and Indian geologists who announce 
that there was an Ice Age in their countries some ten 
million years ago? And what a feat of imagination 
it must be for Canadian geologists to assert that they 
can trace one of these revolutions in climate fifty or 
more million years ago? 

So talks a certain type of man in the street. The 
truth is that some of the statements of science which 
seem to him most clearly beyond the power of the 

21 



22 HOW WE DISCOVER ICE AGES 

mind are reached by methods which are really simple 
and positive. We say that light travels at 186,000 
miles a second, and that 700,000,000,000,000 waves 
of it enter your eye in a second when you see a violet. 
We say that the earth weighs 6,000,000,000,000,000,- 
000,000 tons ; that very few of the stars are less than 
100,000,000,000,000 miles away; that a certain "new 
star" was a blaze of white-hot hydrogen gas, several 
hundred billion miles away, flaming outward at a 
speed of a thousand miles a second. We say that 
electrons travel at (sometimes) more than 100,000 
miles a second, and that the nucleus of an atom of 
matter is about the billionth of a centimetre (which 
is about two-fifths of an inch) in diameter. The 
thoughtless person rolls his eyes, as if he knew more 
about the rules of evidence than our best men of 
science do. Yet in all these cases the evidence is 
exquisitely simple it can be explained to anybody 
and conclusive. It is far easier to prove these things 
than to prove that there are any stars, or even that 
there is an earth. 

The evidence of past Ice Ages is even simpler and 
easier. Some years ago I visited Switzerland and 
was particularly interested in one of its ice-rivers, or 
glaciers, which is called the Rhone Glacier, because 
the stream of water which flows from it, as it melts, 
is the beginning of the river Rhone. You go up a 
broad valley, fifty miles long, from the Lake of Geneva. 
Steep mountain sides, with a glacier or a snow-field 



HOW WE DISCOVER ICE AGES 23 

gleaming here and there on the crests, enclose the 
valley; and all the way along it are piled huge mounds 
of a peculiar bluish-grey rubbish, with large stones 
of every shape and size mixed in beds of coarse dust 
or what looks like soil. 

At length the side-walls of the valley gradually 
close in, and you reach its head. Before you a cas- 
cade of ice, a frozen Niagara, hangs over the ledge 
of the higher crest and tumbles, in masses as large 
as houses, all crushed together into a giant stream, 
down to the floor of the valley. It moves so slowly 
a few feet a day that it seems frozen to the moun- 
tain-side; but, if we tracked the stones on it month 
by month, we should see that it does move. 

And here you get the secret of the great mounds 
that sprawl the length of the long valley. The ice is 
from fifty to several hundred feet thick. Where it is 
200 feet thick we can calculate that it lies on its rocky 
bed with a pressure of 500,000 pounds to the square 
yard. In other words, it is a colossal scourer, weighing 
millions of tons, slowly grinding down the mountain- 
side. Suppose we set a mass of steel weighing millions 
of tons travelling by its own weight down the slopes 
of the heights above London. Suppose some agency 
kept this sluggish but powerful river of steel flowing 
for tens of thousands of years. Houses and soil would 
soon go, then the moving mass would begin to scour 
the rocks (if there were rocks below) into fine powder, 
and carry it to the valley below. 



24 HOW WE DISCOVER ICE AGES 

That is what the glacier does. The water that 
streams from it at the melting-point is a sort of 
muddy blue with this powder. Mounds of the dust 
lie about, and are continuous with the mounds down 
the valley. You notice also that the ice bears stones 
of all sizes on its surface, near its edges. Looking up 
the glacier, you see why. As it passes under the 
cliffs, the stones fall upon it from above. The sun 
is just as powerful in the snow-fields as in the valley 
more powerful, as I found when it scorched all the 
skin off my face. It melts the surface of the snow 
and ice, and water trickles during the day into every 
crevice. At night the water freezes and expands, 
breaking off fragments of rock that go down upon the 
glacier. They mingle with the dust of the scoured 
rocks where the ice melts. 

Many of the stones slip through the great cracks or 
crevasses in the ice, and reach the lowest part of the 
ice-river. You can imagine what happens. As the 
glacier moves, they are driven into the rocky floor of 
the bed by a pressure of half-a-million to a million 
pounds to the square yard. This will make scratches 
or furrows in granite rock. The whole bed of the 
ice-river is scored by the marks of its flow. It is as 
if the river of steel which I imagined were studded 
with steel teeth on its lowest side. They would 
plough, or rather harrow, granite. 

So this Rhone Glacier, which we are studying, 
does three things. It marks its bed with scratches 



HOW WE DISCOVER ICE AGES 25 

and furrows, in one general direction (the direction 
of its flow), which will last for ages. It leaves a 
mound (or "moraine") of a peculiar and easily 
recognized rock-dust, as we may call it, at its melting- 
point. It mixes with the dust the stones, large and 
small, which it has collected in its passage. 

Now we begin to understand the fifty-mile valley 
up which we go to find the glacier. It has similar 
mounds of mingled dust and stones all along, though 
they are immensely larger than the mound at the 
foot of the Rhone Glacier. It is grooved and scratched 
and furrowed, in a consistent direction (down the 
valley), all through. There can be no mistake what- 
ever about the conclusion. The whole valley was 
once filled by a giant glacier. The comparatively 
small Rhone Glacier of to-day once ran the whole 
length of it, and was joined by similar streams of ice 
from every side-valley until a vast solid river of ice, 
in places ten miles wide and more than a thousand 
feet deep, filled the whole valley. 

At the end of the valley is, as I said, the broad blue 
face of the Lake of Geneva. Something has carved 
out of the solid surface of the earth a basin forty-five 
miles long, and in places a thousand feet deep. Again, 
there can be no mistake about the cause of it. It 
was the vast glacier that came down the Rhone 
Valley at some remote date. If a very ponderous 
mass is moving down a slope and it at last touches 
level ground, it will naturally strike this level ground 



26 HOW WE DISCOVER ICE AGES 

with a greater pressure than ever. It will wear a 
little hollow at the point where it ceases to travel 
downward and encounters the horizontal strata. 
And if your mass weighs millions of tons, and keeps on 
scouring for tens of thousands of years, it will in the 
end scoop or gouge a great basin out of the solid 
crust of the earth. When the ice melts at last, the 
basin will fill with the waters. The lake is another 
reminiscence of great glaciers of long ago. 

By means of the scratches and scoured rubbish and 
stones transported from distant hills we can trace this 
huge glacier of long ago about two hundred miles 
further across the plains of Europe. And it is the 
same on every side of Switzerland. The valleys up 
which we pleasantly travel to-day were once filled 
with ice. They were mainly carved by ice. The 
lake-basins were hollowed out by the ice. The Lake 
of Lucerne, and especially the Italian Lakes, mark 
sites where colossal ice-rivers struck the plain age 
after age. On the Italian side the slopes along which 
the glaciers moved are steeper, and the lake-basins 
are deeper and grander. Every feature of the scenery 
becomes intelligible. 

We now know the chief means by which we can 
recognize regions where there was once very thick 
ice which means ice summer and winter and is no 
longer: scratches and furrows in a generally con- 
sistent direction, great mounds of dust scoured off 
the rocks and including blocks of stone from distant 



HOW WE DISCOVER ICE AGES 27 

mountains, and lakes of the kind we have described. 
We apply these to the Swiss district, and we learn 
that at one time a mighty cap of ice and snow covered 
the whole country and stretched far beyond it. We 
can prove, in fact, that 15,000 feet have been scoured 
off Mont Blanc itself since it reached its greatest 
height. The Swiss snow-fields and glaciers of to-day 
are shrunken remnants of the former sheet of snow 
and ice. 

It is by precisely the same means that we can tell 
that, at the same time as Switzerland wore its huge 
ice-cap, eight million square miles of Europe and 
America were covered, summer and winter, with ice 
and snow, and every high range of mountains on the 
earth had a corresponding ice-sheet. I once travelled 
on a stage-coach through a valley in New Zealand 
Arthur's Pass which corresponded with the Rhone 
Valley in Switzerland. It was a wide gorge cut 
through the rocks by a great ice-river long ago; and 
the little glaciers which hung upon its crests, and even 
the large glaciers of the New Zealand Alps beyond, 
were diminished relics of a period of far more extensive 
ice and snow. The fiords of New Zealand, like the 
fiords of Norway, are other relics. They are the 
tracks cut in the raised and rocky coast by great 
glaciers of long ago. They were carved by ice the 
work in each case being afterwards completed by 
water just as were the valleys of the Alps. In South 
America and other parts of the world we have similar 



28 HOW WE DISCOVER ICE AGES 

memorials of ice-action on a vast scale in the recent 
history of our planet. 

But it is especially in the north of Europe and of 
North America that we find such memorials. I have 
mentioned the fiords of Scandinavia. Looking up 
some of the more northerly of these fiords, you still 
see a comparatively small glacier at the head of the 
valley. It is, like the Rhone Glacier, the shrunken 
survivor of a colossal glacier of long ago, which carved 
the fiord. 

The plateau of Scandinavia was plainly at one 
time a vast snow-field such as we now find in the 
Arctic. Summer and winter the snows accumulated. 
The sun would melt only the surface, and the water 
trickling or soaking down into the condensing snow 
helped to convert it into a mass of ice; as happens in 
the snow-fields of Switzerland to-day. The ice moved 
bodily, thousands of feet deep, to the lower level, 
breaking into rivers or glaciers, which poured through 
every gap at the edge of the plateau, widening and 
deepening each gap until it became the beautiful 
valley which we now call a fiord. 

How far did these colossal glaciers of Scandinavia 
go? One of the ways in which we can retrace their 
paths is, as I said, by means of the blocks of stone 
which they gather from their native mountains, and 
bear along until the ice reaches its melting-point. 
Now, it was noticed long ago that the east coast of 
Scotland is strewn with great blocks of stone which 



HOW WE DISCOVER ICE AGES 29 

certainly came from Scandinavia. How explain this 
mystery in the old days? 

One clerical writer, who would have none of this 
nonsense about an Ice Age, said that the blocks were 
probably brought by the Vikings, as ballast for their 
boats, when they descended upon the coasts of Scot- 
land! We now see, of course, that they were brought 
by ice. It is not yet entirely settled whether they 
were brought by icebergs floating in what we call 
the North Sea or by glaciers. The general opinion 
is that the North Sea did not then exist, and the 
Scandinavian glaciers spread a huge sheet of ice as 
far as Scotland, four hundred miles away. We trace 
the glaciers in the same way over Denmark and 
Germany. 

But Scotland, we find, had at the same time its 
own glaciers, and they were far more formidable than 
any of the two hundred glaciers of modern Switzerland. 
Some were three thousand feet deep. They poured 
sluggishly down from the higher Caledonian moun- 
tains, some of them passing along the valley which 
is now the Irish Sea as far as North Wales. From 
the hills of Cumberland and Westmoreland flowed 
other glaciers, helping to complete the mantle of ice 
over northern Europe. The English lakes, generally, 
fill basins that were carved in the earth's crust by 
the glaciers of the district; just as the Scottish lochs, 
generally, also mark spots where the moving masses 
of ice touched the plains. In other cases valleys 



30 HOW WE DISCOVER ICE AGES 

were dammed by mounds of glacial rubbish and 
converted into lakes. The Welsh mountains were 
another great snow-field that poured immense glaciers 
over the country. 

Over all these areas we have the same unmistakable 
evidence : smoothed and scratched rocks, hollowed-out 
lake-basins, blocks of stone from remote mountains, 
and especially the huge beds of mingled scour-dust 
and stones which geologists call "boulder-clay" or 
"Drift." 1 Within one recent month I had occasion 
to travel along four or five of the valleys of South 
Wales, and in Lancashire, Northumberland, and 
Scotland. In each district the railway-cutting showed 
mile after mile of glacial rubbish; and I have noticed 
the same from the train in the United States, from 
New York to St. Louis, from Detroit to Niagara. It 
underlies the soil over immense areas of North Europe 
and America. 

It is interesting, as one travels, to find oneself 
flying in a modern train through miles of country 
where once vast glaciers laid down their burdens of 
rubbish. A man can recognize it almost anywhere; 
it is so characteristic. It is interesting to stand on 
the hill-tops in England, Wales, or Scotland, and 

1 The Drift (mixed mass of dirt and stones or boulders) is 
generally called "Till" if it lies as it was originally. But the 
flooded waters at the close of the Ice Age have largely redis- 
tributed or "stratified" it. That is why the boulders are so 
commonly rounded, as stones are in running water. The actual 
mound left by the glacier is called a "moraine." 



HOW WE DISCOVER ICE AGES 31 

trace the paths of the great ice-rivers which did most 
of the carving of their valleys, or to mark the boulders, 
scattered over green valleys, and picture the stream 
of ice that bore them ages ago. But the systematic 
work of carefully examining each of these regions and 
piecing them together in a comprehensive map of the 
glacial area has been done long ago by geologists. 
At some time within the recent geological period eight 
million square miles of Europe and North America 
were covered with a sheet of ice and snow, summer 
and winter, such as we find in the Arctic Circle to-day. 
In Europe, generally speaking, the ice-sheet spread 
down nearly to the latitude of the Thames and the 
Danube; but we have quite lately discovered that 
there were small glaciers even on the South Downs 
at that time. 

In America the sheet was even larger than in 
Europe. The great lakes were hollowed out by 
enormous glaciers moving down from Canada, and 
the marks of the ice are seen much further south. 
Within ten miles of New York one sees that the 
railway-cutting is ploughed through a bed of glacial 
rubbish. The indications are the same everywhere. 
The soil was scoured off vast areas, and their rocks 
were rounded, smoothed, and scratched. Older 
streams found their paths barred and were turned into 
new courses. Boulders and boulder-clay are found on 
all hands. 

We have spoken of Switzerland, but Greenland 



32 HOW WE DISCOVER ICE AGES 

gives us a better picture of what northern Europe 
and America were like at this time. Glaciers suggest 
comparatively narrow streams of ice, rarely a mile 
wide, though there is one in Alaska, the Malaspina 
Glacier, which has a coast-front seventy miles in 
width, and is more than 1,000 feet thick. But there 
may be lakes or seas of ice as well as rivers. In 
Greenland the sea or "cap" of land-ice covers half- 
a-million square miles, and it is often five hundred 
feet deep. Such caps there must have been in Europe 
and America. On the other hand, we do not imagine 
ice-caps or glaciers everywhere. As we shall see 
later, the reindeer, the mammoth, and the wool-coated 
rhinoceros were able to live in Europe. There were 
grassy or mossy regions. But we must remember 
that, in the height of this great chill, the reindeer 
and mammoth wandered as far south as the foot of 
the Pyrenees and the Alps. Even southern Europe 
and the southern United States must have then had 
a climate like that of Lapland or northern Siberia 
to-day; and the influence of the great chill, the cold 
winds from the ice-fields, would extend still further 
south. 

These things will concern us later. We are in- 
terested here only in the huge sheet of ice and snow 
that for tens of thousands of years covered half 
Europe and North America. It was the last great 
Ice Age. It is humorous to recall that even a geologist 
of distinction could call this a "nightmare" twenty 



HOW WE DISCOVER ICE AGES 33 

years ago ! There is no more certain event in geologi- 
cal history. The lingering hostility to it is only one 
more instance of the folly of resisting science on non- 
scientific grounds. 

We discuss the causes of the Ice Age in the next 
chapter, and its remarkable influence on the evolution 
of man in a later chapter. But the reader will 
urgently ask when this Ice Age occurred. Here, 
unfortunately, science has no confident answer. The 
geologists of Scandinavia have recently made a very 
careful attempt to settle when the glaciers of their 
country retired to their present positions. They tell 
us that it was about 30,000 years ago, and this is 
generally accepted as "the end of the last Ice Age." 
But since we do not know how slowly the ice re- 
treated northward, this does not help us very 
much. The Ice Age was over in France before it 
was in England, and in England long before it was 
in Scandinavia. 

Probably most of the authorities would agree that, 
whatever be the period of time during which this 
mantle of ice and snow covered Europe and North 
America, it was at its greatest extension between 
50,000 and 100,000 years ago possibly nearer to 
the latter. Here there is a difficulty that is not yet 
settled. Most geologists believe that what we call 
an Ice Age is a very long period possibly several 
hundred thousand years during which the ice spreads 
from the higher land and retreats to it four or five 



34 HOW WE DISCOVER ICE AGES 

times in succession, and that there were comparatively 
warm intervals between the successive advances of 
the ice. Some suggest that when the burden of ice 
became very heavy Europe sank a little under it; 
much as if you pressed in one side of a tight rubber 
ball. It is thought that this would mean a return of 
the warmer climate and the melting of the ice. Then, 
it is said, the crust that part of it which we call 
Europe would rise again, and be glaciated once 
more. Others deny this, and believe that there was 
only one great ice-sheet. 

This unsettled question need not detain us. 
Whether there were previous and smaller extensions 
of the ice or no, there was that enormous extension 
which we have described. On that all are agreed. 
How long it lasted we cannot say. The estimates of 
those who believe in successive sheets of ice run up to 
400,000 years (which Sir Arthur Keith adopts in his 
Antiquity of Man), and even larger figures. We will 
return to the point in the seventh chapter. There also 
we will consider if the Ice Age is quite over. 

We have now given so fully the evidence for the 
last Ice Age that it is almost enough to say that, on 
the same sort of evidence, we find earlier Ice Ages 
scored upon the face of the earth. These mighty 
masses of hundreds of millions of tons of ice make 
an impression that the earth cannot easily erase. 
Naturally we do not find the evidence for earlier Ice 
Ages so abundant. The field of the Great War still 



HOW WE DISCOVER ICE AGES 35 

shows its ghastly scars, but the field of Waterloo, 
a little further north, shows no trace of the Napoleonic 
struggle except where men have artificially preserved 
the bullet-marks. The hand of millions of years of 
time has generally smoothed the wrinkles and 
scattered the mounds of the earlier Ice Ages. 

But the deep grooves and scratches which moving 
ice makes may be buried under later deposits, and so 
be preserved. I went one day to a beautiful gorge 
in Victoria, some fifty miles from Melbourne, to see 
the traces of a remote Ice Age. No ice or snow is 
ever now seen, summer or winter, in the Werribee 
Gorge; but on the exposed hard rocks, beside the 
stream, I found the unmistakable furrows and 
scratches. High overhead, at the top of the steep side 
of the gorge, was a narrow seam of coal. Once a semi- 
tropical carboniferous forest had covered the district 
with its weird giant club-mosses and tree ferns. 
Upon this an Ice Age had fallen. The glacier from 
the higher region had carved this gorge, and on its 
floor were the marks, at least ten million years old, 
of the passage of the frozen load. Even granite 
rocks are to such glaciers merely as stiff soil is to a 
harrow. 

Geologists in India and South Africa find the same 
marks on rocks which correspond, in point of time, 
to the glacial marks in Australia. It had then been 
the turn of the southern continent. We know from 
other evidence that India, Australia, and South Africa 



36 HOW WE DISCOVER ICE AGES 

were at the time connected by land. Apparently this 
lost continent was the main theatre of an Ice Age 
one of the most deadly on record in that remote 
period. 

Two earlier Ice Ages are announced, and we will 
consider them in the fourth chapter. There was 
also, as we shall see, a period of such great and fatal 
chill, though with few marks of ice as far as we yet 
know, that it deserves to rank with the other four 
revolutions in climate. We may say, therefore, 
roundly, that we have discovered five Ice Ages. Apart 
from these we can detect occasional periods of cold 
that are very much more restricted in extent ; but the 
crust of the earth has now been so extensively 
examined that no one expects to discover another 
Ice Age. 

More than a hundred years ago the great German 
poet Goethe began to collect evidence of the last Ice 
Age. He traced the former extension of the Swiss 
glaciers over southern Germany, and of the Scandi- 
navian glaciers over north Germany. A few other 
geologists for Goethe was a close student of science 
were picking up the traces in various parts of 
Europe. There they had lain for fifty thousand 
years, awaiting the birth of science in the eighteenth 
century. 

To these men the discovery had an exhilarating 
novelty. They had found something new and interest- 
ing about the earth and its history. That the world 



HOW WE DISCOVER ICE AGES 37 

at large ridiculed them and their stones need not be 
said. That there were others who would have liked 
to burn them for suggesting that the earth was more 
than six thousand years old, or had ever worn this 
ridiculous mantle of snow and ice, need also not be 
recalled. Goethe worked on. But what a passion 
would have been infused into his work if he had 
known, as we know, the part that Ice Ages have 
played in the development of life! Fifty years later 
came Darwin. But even he had to quit the study 
before he could penetrate half the mystery of this 
procession of life through the ages which he so master- 
fully sketched. Ice Ages have helped to illumine it 
for us. We have at last learned how to read the 
hieroglyphs they have left on the rocks, as early 
civilized man left on his tombs and temples. Let us, 
however, first settle the problem of the cause of the 
Ice Ages themselves, which, experience tells me, is 
one of the earliest questions to arise in the mind of 
the learner. 



CHAPTER III 

THE CAUSE OF ICE AGES 

As late as 1876 you will find Encyclopaedias that 
make no reference to Ice Ages, as if these were foolish 
or malevolent dreams of cliques of scientific men who 
wanted to disturb the existing order of ideas. But 
by that time every impartial geologist knew that the 
last great Ice Age was an established fact, and the 
search for the causes of it had begun. 

There is still a certain type of writer who insists 
that science, especially evolutionary science, explains 
nothing; that it only describes. This is little more 
than a play upon words. If we take such a phenom- 
enon as an Ice Age and, after prolonged search and 
severe checking of our results, assign the causes of 
the Ice Age, most people will call this an explanation, 
in the ordinary sense of the word. It is, of course, 
open to any person to say that we are now merely 
describing the causes, just as we previously described 
the effects; though in that case we should have some 
trouble to explain what an explanation really is. 
I refer to the matter only because the way in which 
science has solved the problem of the Ice Ages is an 

38 



THE CAUSE OF ICE AGES 39 

excellent illustration of the foolishness of this kind of 
talk. We shall see that modern geology has at last 
hit upon what we cannot doubt to be the real causes 
to use strict scientific language, the antecedent con- 
ditions of Ice Ages, and these will seem to the ordinary 
person all that he requires in the way of explanation. 
The same point will serve to refute another rather 
foolish gibe at modern science: the one thing in 
modern life, the one achievement of the modern 
mind, which places us indisputably and immeasurably 
above any previous civilization. Science seems to the 
casual reader to change its teaching very frequently, 
and there are those who try to destroy our confidence 
in it on this ground. The gibe seems foolish when 
one regards the solid and unchanging structure of 
knowledge which science has built up in the course 
of a hundred years, or the way in which to-day it 
analyses with certainty the chemical composition of 
a star that is a million trillion miles away, or measures, 
and discovers the speed of, tiny particles (electrons) 
which are thousands of times smaller than the atoms 
of matter. The man who is urged in this way to 
distrust science need only look round the new world 
in which he lives the electric lighting and transport, 
the medical and sanitary and chemical services, the 
cheaper commodities and luxuries from other lands 
and he will exclaim, in the words of Sir Christopher 
Wren's epitaph in St. Peter's Cathedral: "If you 
seek his monument, look around you." 



40 THE CAUSE OF ICE AGES 4 

w 

But we shall now see a very good instancp of the 
kind of change which is constantly taking place in 
science. The man of science proceeds, in the ex- 
planatory part of his work, much as a criminal detec- 
tive does. He confronts a problem, often with very 
slight clues. He makes various guesses or "theories" 
about the solution of the problem, and these he suc- 
cessively follows up and checks until he finds the true 
cause. We do not blame the detective, although he 
fails, perhaps, in a larger proportion of cases than the 
investigator of nature does. 

The first idea that occurred to experts as an explana- 
tion of Ice Ages was that possibly the Poles of the 
earth shifted their position in the course of ages. The 
earth spins round, in space, like a huge top. It is a 
vast ball of metal, weighing six thousand million 
trillion tons, which, as the geography books politely 
say, "turns on its axis" once in twenty-four hours. 
We should prefer to say that it whizzes round on its 
axis; for the people who live at the earth's Equator 
are borne round and round at a speed of a thousand 
miles an hour. It is well known that the Poles are 
the coldest parts because the rays of the sun have 
to slant through a great thickness of atmosphere to 
reach those regions. They are reduced by filtering 
through the air, and they fall so thinly upon the Arctic 
Circles that they are unable to melt the snows even 
in summer. 
Well, take the earth as a giant top. Suppose this 



THE CAUSE OF ICE AGES 41 

top did not always spin perfectly upright, as the boy's 
top does. Suppose it very slowly, in the course of 
tens of thousands of years leaned first to one side 
and then to the other. The boy's top cannot do this 
to any great extent it does to some extent because 
its peg is fixed. The earth might conceivably alter 
its position considerably, and in that case the same 
points on its surface would not always be the Poles 
(or the regions farthest from the sun). The Poles 
would "wander"; that is to say, the ice-cap, the 
glacial conditions, would slowly shift from one region 
to another as the earth "wobbled" in space. Why 
not suppose that during the last great Ice Age 
North Europe and America were simply the polar 
regions of that time? 

The theory was helped out by another supposition. 
The earth travels round the sun, not in a circle but 
in an ellipse (or, roughly, an oval path), and the sun 
is not in the centre of this ellipse, but nearer one end. 
It follows that at one end of its orbit the earth is 
farther away from the sun than it is in the other 
parts of its orbit, and it also travels more slowly when 
it is thus farther away from the sun. Now, suppose 
this ellipitical orbit were altered in the course of ages 
suppose the two long ends were drawn out still 
farther so that the earth got periodically at a much 
greater distance from the sun. The winter would 
gain upon the summer. The winter's long snows 
would not yield to the summer's sun, and you would 



42 THE CAUSE OF ICE AGES 

have the condition of an Ice Age. If you combine 
this theory with the preceding, whatever region of the 
earth happened to be the polar region at the time 
would have a very cold experience. 

As a theory it is not without fascination; and 
readers of Mr. H. G. Wells' fine Outline of History will 
remember that he has incautiously adopted it. But 
it is as dead as Daniel in modern science. A brilliant 
American astronomer, the late Mr. Percival Lowell, 
called it "the astro-comical theory of Ice Ages." 
Astronomers themselves will not admit Sir Robert 
Ball was the last to admit such extensive wobbling 
on the part of our staid globe. Sir G. Darwin proved 
long ago that such wandering of the Poles has not 
occurred. Professor Barrell, probably the highest 
recent authority on the cause of Ice Ages, sums up 
the opinion of our astronomers in the words: "It 
would appear that the assumption of polar wandering 
as a cause of climatic change and organic migration is 
as gratuitous as an assumption of a changing earth 
orbit in defiance of the laws of celestial mechanics." 

And the geologists want the theory still less than 
the astronomers do. If it were true, there must have 
been fairly frequent periodical Ice Ages; one living 
writer, who clings to the theory, speaks of Ice Ages 
every 35,000 years! On the contrary, there have been 
only five Ice Ages in a hundred million years or more. 
If the theory were true, moreover, there would be ice- 
caps on each side of the earth North and South 



THE CAUSE OF ICE AGES 43 

Poles during each Ice Age. No such thing occurred. 
When the continent which stretched from India to 
Australia and South Africa was glaciated, the op- 
posite Pole of the earth was not. When the Northern 
Hemisphere was covered with ice and snow from the 
Urals to the Rocky Mountains, there was only a 
small amount of ice in Australia and a large cap (due 
to the mountains) in New Zealand just as there was 
in South America and India. In no case were there 
two polar caps. In fact, as we saw there were no polar 
caps on the earth until recent times. Moreover, the 
ice-sheet of the last and greatest Ice Age was nothing 
like circular. It had an immense width from the 
Rockies to Siberia (across Europe) and a com- 
paratively slight depth. 

The theory was, therefore, generally abandoned 
twenty years ago. When it was started the geology 
of Ice Ages was very imperfect. It was possible to 
squeeze into the mould of the new theory the few 
facts that were known. Since then glacial geology 
has made enormous progress, and the new facts are 
quite inconsistent with the first guess. So, like the 
detective, we abandon the first supposition and try 
another. 

We need not consider in such detail all the other 
causes that have been suggested. The idea grew up 
since no one of them seemed sufficient of itself, that 
the Ice Ages were due to combinations of various 
causes at particular points in the earth's history. 



44 THE CAUSE OF ICE AGES 

Some argued that, if you assume an intense period 
of volcanic energy at times, the atmosphere would 
come to have an immense fine screen of volcanic ash 
floating in its upper regions, which would keep off the 
rays of the summer sun. We know that there have 
been such periods, but they do not generally agree in 
time with the Ice Ages, and so here we have, at the 
most, a possible auxiliary cause. 

Others suggested that the ocean currents may 
change. New York has what the Americans call 
"zero weather" for months in the winter, because 
a glacial current runs down the eastern coast of 
America from the north; and if a strong current of 
air a violent wind comes with it, a Londoner (as 
I have found) can hardly breathe at the lower end of 
Broadway. London, which is much further north 
than New York, not only has no zero weather, but 
during most of the winter it is quite temperate, be- 
cause the British Isles are bathed by a warm current 
(the Gulf Stream) and the warm southwest winds 
which accompany it. There is actually a plan, in 
great favour with anti-British Americans, to change 
the course of the currents; and we should be frozen 
up every winter without our Gulf Stream. 

The idea, therefore, occurred to some that such 
changes of currents, owing to changes in the configura- 
tion of the land, may have made different parts of 
the earth glacial at different periods. The chief objec- 
tion to this is that during the greater part of the 



THE CAUSE OF ICE AGES 45 

earth's story there were no cold currents of air and 
water, for there was no ice nor snow. The glacial 
currents follow the setting-in of the Ice Age; they 
help us to understand something which has greatly 
puzzled geologists: why the polar regions remained 
warm, in spite of the slant of the sun's rays, until 
recent times. It may have been, as Professor Cham- 
berlin has suggested, because warm currents from the 
rest of the earth helped to keep up their temperature. 

The next cause suggested is much more plausible. 
Why is it colder on the top of a mountain than at 
sea-level? The rays of the sun, of course, are just 
as strong, or stronger, because they are less obstructed 
by the pure air. But, except in the direct rays of the 
sun, it becomes colder the higher you go. Height, as 
such, has nothing to do with the matter. It is the 
gradual thinning of the atmosphere as you rise which 
is responsible for the cold. We notice at sunset that 
the rays of the sun are far less powerful than at mid- 
day. We know that they are far less powerful in 
London or New York than they are "on the line." 
Everybody knows why. When the sun's rays slant 
they must pass through a thicker mass of air than 
when the sun is right overhead, and the air reflects 
or absorbs much of the heat. 

The thicker the air, in other words, the less heat 
will get through. But this cuts both ways. A thick 
air will let less heat reach the earth, but it will also 
let less heat pass away from the earth. The mountain 



46 THE CAUSE OF ICE AGES 

top is cold because the thin air not only lets more of 
the sun's heat through, but lets it be reflected at once 
back into space. The thick air of a city at the sea- 
level lets less direct heat through, but what it lets 
through it retains at the surface very much more. And 
two impurities in the air are especially important from 
this point of view: the vapour of water and carbon 
dioxide (or carbonic acid gas). 

As to moisture, everybody has had experience of 
the difference it makes. Moist, muggy weather makes 
a district very warm. The district is, as it were, 
wearing an overcoat in summer. At the same time, we 
must remember that the moisture is itself necessary 
for an Ice Age. One of the coldest regions of the 
earth, Eastern Siberia, is not glaciated. It is dry, 
and the summer sun can melt the light snowfalls 
of the winter. Greenland, on the other hand, is 
glaciated. It receives the moist winds of the Atlantic, 
which give very heavy falls of snow; and, although 
its mean temperature is much higher than that of 
Eastern Siberia, the snows remain and condense 
into an ice-cap and glaciers. Some scientific men 
have ventured to say that abundance of moisture 
is more important than cold for making an Ice Age. 
We shall see presently how to overcome this difficulty. 

Carbonic acid gas, on the other hand, simply tends 
to keep the surface of the earth warmer. The more 
there is in the air the warmer the region will be, and 
vice versa. It has therefore been said that possibly 



THE CAUSE OF ICE AGES 47 

one of the greatest causes of change of climate in past 
time was a change in the proportion of carbon dioxide 
in the atmosphere. 

This matter is worth considering a little more 
closely. At present there are, on the average, only 
three volumes of carbon dioxide to ten thousand 
volumes of pure air in our atmosphere. But suppose 
there was once, or generally has been, a far higher 
proportion! Clearly, in that case the great warmth 
of the earth in past ages looks intelligible. Now 
there is twenty-five times as much carbon in the sea 
and thirty thousand times as much in the rocks 
(chiefly in coal and limestone), as there is in our 
atmosphere; and the oceans and rocks have derived 
their carbon, directly or indirectly, from the air. Here 
we seem to get some light on the high temperature 
of the earth during most of its history; and if we 
suppose that at times the proportion of carbon in the 
air was reduced far below what it is to-day, we get a 
plausible theory of the cause of Ice Ages. 

We have, in fact, a kind of third battle of the ele- 
ments underlying the drama of life; and these things 
are really much more enlightening than "vital prin- 
ciples" (which are hopelessly unintelligible in them- 
selves) or mysticism like Professor Bergson's. There 
is the battle of land and water. There is the battle of 
the constituents of the air. And there is the battle, 
connected with and based upon the other two, of 
heat and cold. The oceans and plants are constantly 



48 THE CAUSE OF ICE AGES 

absorbing carbon from the air, and the balance is 
restored at times by great volcanic outbursts, which 
belch dense volumes of carbon dioxide into the air. 
On the generally accepted theory of the earth's origin 
atmosphere began with a high proportion of carbon 
in it. There is a new theory which denies this; but 
both must and do admit great volcanic activity, 
recorded in the rocks, at different periods. I 

But while we read in the calendar of the rocks of 
intense periods of absorption of carbon (such as the 
Coal Forests) and vigorous periods of discharge of 
carbon (by volcanoes), we do not find that they occur 
at such periods as to explain the five Ice Ages. It is 
true that one of the greatest of the Ice Ages comes 
just after the Coal Forests and the formation of much 
limestone; and this is exactly what theory requires. 
But the last and greatest Ice Age had these ante- 
cedents only in the scantiest degree far less than 
the preceding Ice Age, which was so much less severe 
that we can give it the title of an Ice Age only by 
courtesy. So we must go further, and reserve this 
as a possible auxiliary cause. 



1 1 should say that I am indebted for most of the material of this 
chapter, and much of the material of other chapters, to the bril- 
liant American geologists, Professor Chamberlin, Professor 
Schuchert, Professor Barrell, and Professor Case; and that they 
all follow the new (Planetesimalist) theory of the earth's origin, 
which I do not accept. I cordially acknowledge my debt to their 
fine works, however, and refer the reader to them for further 
details. 



THE CAUSE OF ICE AGES 49 

Another theory is that these past variations of 
climate are due to variations in the emission of heat 
by the sun. We have made the curious discovery 
that our actual glaciers advance and recede over periods 
of something between thirty and forty years; and 
some suspect longer periods of between 500 and 600 
years. It is thought that these periods mean periodic 
changes in the sun's radiation of energy; and, at all 
events, it is now known that there are periods of the 
maximum formation of sun-spots. But, as it is im- 
possible to imagine how changes in the sun can ac- 
count for local chills on the earth, I will not linger over 
this theory. The sun's radiation affects the whole globe. 

When, fourteen years ago, I first touched upon this 
subject in one of my works, I found geologists in 
suspense between the suggestions I have given and 
one other, which they admitted only to the same 
rank : the elevation of the land. It seemed to me that 
the latter was the really fundamental cause of Ice 
Ages, and in all my works since I have so described it. 
We now have authorities like Professor Schuchert I 
need not say that he is not likely to have read my 
popular works! writing that "probably the greatest 
single factor is high altitude of the continents, with 
great chains of mountains which disturb the general 
direction and constitution of the air currents and the 
ocean currents as well." Professor Case, Professor 
Barrell, and other special students are of the same 
opinion. 



50 THE CAUSE OF ICE AGES 

There is really no longer any need for reserve in 
stating the cause of Ice Ages. Professor Schuchert 
has given us a diagram in which he combines a chart 
of known rises of the land in past time and a chart 
of cold periods (Ice Ages and minor chills) in past 
time. They correspond almost as closely as the 
fingers of a man's hand correspond to the fingers of 
a glove. The few discrepancies and these relate 
only to minor and less known periods are within the 
limits of possible error owing to imperfect know- 
ledge. Every serious chill the earth has experienced 
came just after, and during, a rise of the land to a 
proportionate extent. 

Coincidence is absolutely out of the question, and 
we have only to reflect a little upon the matter to see 
that here we have a real and most interesting explana- 
tion. Let us again anticipate a little. The period 
of the Coal Forests was closed by an Ice Age. Now 
geologists can tell what was the condition of the earth 
during the age of the Coal Forests. Apart from a 
few local dry areas, the land was overwhelmingly low, 
hot, and muggy. It was a land of steamy swamps 
and saturated forests. The air was foul with carbon 
dioxide and rich in vapour. It brooded sluggishly 
over the land, keeping in the heat which struggled 
through it to the sun. 

We know that towards the end there was an exten- 
sive rise of the land, and we can easily work out the 
effect. Most people know how rainy Killarney is. 



THE CAUSE OF ICE AGES 51 

The reason is that the moist winds from the Gulf 
Stream reach the summits of the Kerry hills, and 
are cooled. The invisible particles of moisture then 
come together and form clouds, and the "clouds 
drop their fatness" upon poor Kerry (which suffers 
much consumption in consequence). In other words, 
mountains cause a circulation of the air and a pre- 
cipitation of its moisture in the form of rain. Thus 
the higher lands which rose at the close of the Coal 
Forest period enormously lessened the proportion of 
moisture in the air in those regions sent it back to 
the sea in rivers and the heat of the earth could 
escape better into space. At the same time the Coal 
Forests and limestone beds had been for a million 
years or more extracting carbon from the air in great 
quantities enormous quantities and helping to thin 
the atmosphere. It was like taking two blankets off 
the bed of a man who was accustomed to have three. 
The earth shivered. There was an Ice Age on and 
around the highlands. 

I must not give the reader the impression that all 
this is now quite clear and harmonious. We are, 
remember, talking about the climate of ten or more 
million years ago. There are difficulties. Here and 
there during the Coal Forest Age the earth was, 
locally, dry enough to form salt beds. In Australia 
the ice of the later period is sometimes found at what 
is now sea-level. It is for science to find exceptional 
conditions locally. The broad truth is that every 



52 THE CAUSE OF ICE AGES 

rise of mountains has been followed by a chill; and 
every Ice Age has been preceded by a great rise of 
mountain chains. We shall see this in later chapters. 

Thus we combine what is sound in the various 
speculations I reviewed. The crunching or crushing 
of a large part of the crust of the earth into the folds 
which we call mountains would lead to great volcanic 
activity. The alterations of level would create new 
ocean currents and modify old. The moisture that 
had, when it was evenly distributed, warmed the 
earth is now gathered into clouds, which form rain, 
and later snow and ice. From far around the cold 
regions would receive the warm moist winds, and the 
heavy snows would pile up on the mountains and 
harden into ice. But these general principles will 
become clearer to the reader when we work them out 
in detail. 

Most people who are unfamiliar with these matters 
have a quite exaggerated idea of the fall in tempera- 
ture that is needed to create an Ice Age, and they thus 
make the problem more difficult for themselves. One 
naturally thinks, at first, that if Europe once enjoyed 
a perpetual summer, and then passed into a long Ice 
Age, the average temperature of the continent must 
have dropped something like fifty or a hundred de- 
grees. It seems to be a question of falling bodily 
from a summer temperature to a winter temperature. 

The fallacy is that we are taking the temperature of 
too small a region, or at particular times. When we 



THE CAUSE OF ICE AGES 53 

think of summer we think of particular spells of hot 
weather. When we recall winter we probably recall 
the very hard days when we in the south of England 
get a dose, brought by northeastern winds, of the 
climate of Russia. The average temperature is very 
different. The scientific man takes the average 
temperature over a whole continent, and can calculate 
how many degrees this annual average temperature 
must fall in order to give the conditions of an Ice 
Age. It is not easy, but the calculation has often 
been made, and there is now a general agreement 
that the necessary fall of temperature is only some- 
thing between nine and eleven degrees. Let us say, 
roundly, ten degrees. 

It is not difficult to see how a great rise of the 
land would bring about a change to this extent in the 
temperature of a whole continent. We have not 
merely to think of the elevation itself, which brings 
large areas up into thinner air, but of the effect upon 
the atmosphere and water-distribution of the whole 
district. Apart from the highlands proper, there will 
be broad stretches of land which were formerly flat 
and low, and therefore probably sodden with water, 
that will now be tilted, and the water will drain 
off. Winds will be created by the inequality of 
temperature between mountain and plain, the air 
above the warm plain expanding and rising, while 
the chilled air from the mountains will take its place. 
The warm moist air will replace the cold on the higher 



54 THE CAUSE OF ICE AGES 

levels and be chilled, and its moisture condensed into 
cloud. There will be a considerable lowering of 
temperature over the whole area. That will give in 
time the required fall of temperature, and the snow- 
laden hills will begin to pour their rivers of thick ice 
down upon the plains. 



CHAPTER IV 

THE FIRST TWO ICE AGES 

IT will be admitted that if we afterwards show that 
there was a considerable elevation of the land before 
each Ice Age as we certainly can in the case of the 
later and more important Ice Ages we have found 
a real explanation. Some people, however, will 
learnedly remind us that there is a distinction be- 
tween "proximate" and "ultimate" causes of things. 
The profound person wants to know the ultimate 
causes. In the present case the demand is reasonable 
enough if we put it in a more familiar shape. We 
have explained the cause of Ice Ages. It was the rise 
of the land and the changes in the atmosphere in- 
volved by this. But what was the cause of the rise 
of the land? 

Here, again, there has had to be a long course of 
inquiry, spread over several decades, and more than 
one attempt to solve the problem has failed and been 
abandoned. In geology the work of science is even 
more laborious and extensive than in other branches, 
because beyond the professional geologists (generally 
professors at universities) there is a vast army of 

55 



56 THE FIRST TWO ICE AGES 

what we may call amateurs, who do material service. 
Every science has its large body of amateurs fellows 
of the Astronomical Society, the Zoological Society, 
the Geographical Society, and so on but in geology 
a larger proportion of them are real workers. The 
reason is that geology has to study minutely the whole 
face of nature. Every quarry or cutting, every gravel- 
pit or cliff, may yield something. So a country is 
practically divided up among its local geologists, who 
search every scar or cliff or exposed surface in their 
neighbourhood. The thinkers, the constructive men, 
the great geologists, have to sift the reports of all 
these local investigations, from all over the world, 
and pick out the important facts which will confirm 
or disprove theories. 

It is well for the non-scientific reader to understand 
this labour. He is apt to suppose that the '" theories ' ' 
he reads of are just clever guesses made by a few men 
who work in libraries or laboratories. It would 
greatly surprise the general public to see one of these 
men at work. I was once in the study of a distin- 
guished anthropologist, a professor at Cambridge, and 
he had an amazing library, in many languages, of 
books and reports on all the races and peoples in the 
world, published or sent in by men who had examined 
them. I found in the study of a distinguished geolo- 
gist a similar mass of reports, from all parts of the 
world, on the particular section of the earth's crust 
(quite a small section) on which he was an authority, 



THE FIRST TWO ICE AGES 57 

besides a great collection of specimens of rock, often 
cut and ground into slices thin enough to be examined 
under the microscope and polariscope. v 

In a word, a theory in modern science is based upon 
a colossal amount of actual observation, all the world 
over, by tens of thousands of trained and devoted 
observers. It has to face a fierce fire of criticism from 
scientific men themselves when it is launched. There 
is, of course, a good deal of further criticism from non- 
scientific people, but no one who is primarily concerned 
about the truth of his opinions takes any notice of that, 
because it is always incompetent, and often ridicu- 
lous. Then, even when the theory is generally ac- 
cepted, it is only "provisional" for a long time. It 
fits the facts at the moment, but new facts may dis- 
turb it. After a sufficient period it may have the same 
degree of certainty as the facts themselves. That is 
the position, for instance, of the theory of evolution. 
Millions of facts, in every department of nature, have 
been discovered since it was proposed, and all fit it 
perfectly. 

The rise of mountain chains in former ages may 
seem to be so far from our experience that any theory 
of the cause must remain very speculative. But the 
matter does in some ways come under experience. 
For instance, when we say that the warm Coal Forest 
period in America ended in an Ice Age because a 
great range of mountains arose there, we have positive 
evidence that this was so. Ranges of mountains do 



58 THE FIRST TWO ICE AGES 

not vanish into thin air. They are ground up, by ice 
and water and weather, and the rubbish is laid by 
rivers on the nearest sea-floor. As we find such 
rubbish (now turned into rock once more) forty thou- 
sand feet deep at a certain part of the United States, 
we know that it represents the ground-down remains 
of a range of mountains, probably about twenty 
thousand feet high, which arose in America toward 
the close of the Coal Forest period. 

Why was the crust of the earth thrown, or crumpled 
into these (and other) mountain masses? Well, just 
as we took Switzerland to illustrate an Ice Age, we 
may take it to illustrate the formation of mountains. 
The higher Alps are great stumps of very hard rock 
(granite, gneiss, etc.), which it takes a long time to 
wear down. We saw that the frost and flowing ice 
are wearing them down, and we know that millions 
of tons have been worn off them since the Ice Age. 
We know further that the stuff of which these granite 
and other mountains are made was once molten rock, 
which has solidified or frozen. It came up from the 
lower depths underneath the ordinary crust of the 
earth. It was originally, in its physical condition, 
like the lava that pours out of an active volcano. 

Now, if we take two ranges of mountains in the 
Alps and examine the rocks under the soil of the 
valley which lies between them, we find a curious 
thing. The beds of sandstone, limestone, etc., under- 
lying the soil of the valley are curled up rather in 



THE FIRST TWO ICE AGES 59 

the shape of a great U as if they were made of leather 
instead of hard stone. We then find the same thing 
in the valley across the mountains the same rocks 
in the same curled conditions. We recognize at once 
that those beds of sandstone or limestone once crossed 
right over the Alps from valley to valley, but they 
have been worn off the mountains while they were 
sheltered under the soil of the valleys. To take a 
simple illustration, it is like an old silver-plated statue 
from the outstanding parts of which the coat of silver 
has been worn while it remains in the sheltered parts. 
In this way we know that in the region which we now 
call Switzerland the crust of the earth has somehow 
been puckered or crumpled accordion-pleated, a 
lady would say into tremendous folds. In fact, we 
can calculate that two hundred miles of what was 
a fairly level plain at one time have been squeezed 
or cramped into a hundred and twenty miles. The 
solid rocks, many thousands of feet deep, were pushed 
into folds, some of which rose to twenty thousand feet 
or more, as if they were made of rubber. This per- 
mitted the molten matter below them to rise under- 
neath the great folds or "pleats" of the crust. It 
solidified, and the "plating" of sedimentary rock was 
worn off, leaving the granite; and so we get our Mont 
Blanc and the other Alps. 

Pushing the examination further, we see that the 
tremendous force which thus crumpled the rocks came 
from the Mediterranean. In France, Germany, and 



60 THE FIRST TWO ICE AGES 

Bohemia there are very heavy and solid masses of old 
rock. It was against these that the crust was pushed. 
If you put three books on the tablecloth and push 
the cloth against them, it rises into folds. Something 
like that happened in the formation of the Alps and 
other mountains. Something crumpled layers of rock, 
from three to five miles thick, into folds. 

We can go a little further. We can discover a force 
that is capable of driving the solid crust into such 
folds. Everybody knows that the water (rain, rivers, 
and waves) is continually wearing away the land. 
The rocks are constantly crumbling, and every shower 
of rain washes away the refuse. The beds of mud and 
gravel of any large river remind us of this. Stones 
are broken into pebbles, pebbles are ground into sand, 
and the sand is heaped on the sloping beds of the seas. 
It has been estimated that the rivers of the United 
States convey 783,000,000 tons of material from the 
land to the ocean every year. The land is so extensive 
that this only means that the United States, as a 
whole, loses one inch deep of its surface in 760 years. 

But regard it from another point of view. Multiply 
783,000,000 tons a year by four or five million years. 
At the end of that time several thousand billion tons 
would be transferred from one part of the earth's 
crust to another. Most probably the pace was not 
so rapid in earlier ages, but it was always rapid enough 
after an Ice Age (when the land stood high). Any- 
how, in time, billions of tons of stuff are worn off 





THE MAKING OF THE ALPS 

Above, an outline of the Swiss mountain-chains ; below, the experi- 
ment with a table-cloth 



THE FIRST TWO ICE AGES 61 

a continent and laid upon the sloping shelf which we 
call the bottom of the sea (near the shore). 

This is a very serious alteration of the equilibrium 
of the crust. The ocean floor sinks slowly under the 
load. On the land the lighter crust steadily rises. 
In the end a very serious strain is set up in the crust. 
There is a prodigious pressure from the sea towards 
the land, and it is only relieved by part of the land, 
next the shore, rising in giant folds as it is pressed 
against the harder masses of the interior, and permit- 
ting the molten matter to rise under the folds. Thus 
have all the great mountain chains been formed. It 
is estimated that this force exerts a pressure of 20,000 
to 30,000 Ibs. per square inch, according to the depth. 

The next step is the wearing down again of the 
new mountains, and it proceeds rapidly while the 
land is elevated and the water runs freely. But be- 
tween the two processes is the interval with which we 
are concerned an Ice Age. For from a quarter to 
half a million years it is generally estimated the 
region shudders under its burden of ice and snow. 
The moving ice then wears down the new land, and 
thus in time brings about its own disappearance. It 
reduces the mountains to a level at which glacial 
conditions no longer occur. The great floods of the 
melting ice in their turn do a vast amount of scouring. 
The "eternal hills" vanish once more, and the earth 
returns or did in earlier ages to its warm lowland 
condition, until another crisis in the crust occurs. 



62 THE FIRST TWO ICE AGES 

As a general theory, based upon quite obvious 
facts, this is very interesting and illuminating, but 
science never pretends to have discovered the final or 
whole truth about anything in half-a-century. Philo- 
sophy is two thousand years old, yet it does not put 
before us a very large body of accepted truths. As 
to theology. . . . But we will give it a rest. It is 
enough to say that no one is more conscious than 
the man of science of the imperfectness of our know- 
ledge; though, in point of fact, the solid structure of 
settled scientific knowledge is colossal, and is rising 
daily. And this in a world in which every other 
system of ideas is crumbling ! 

This explanation, then, is sound as far as it goes 
but it cannot answer every possible question. For 
instance, I drew attention some years ago to a very 
curious feature of our five Ice Ages. The intervals 
between them seem to be about fifty per cent, shorter 
after each Ice Age. I do not know of any geological 
writer who has paid attention to this curious feature, 
yet it is quite plain in every recent geological work it 
is not a personal inference and I will again explain it. 

The geological scale of the rocks which one sees in 
manuals is really a chronological scale. It puts the 
rocks in the order of their appearance in time. But 
we are very uncertain what was the whole period of 
time taken to form the crust of the earth, so it is 
only a relative scale. Some think that the story of 
the earth is a matter of fifty million years; some a 



THE FIRST TWO ICE AGES 63 

hundred, or several hundred, million years. Schuchert, 
one of the ablest geological writers of our time, con- 
siders that "geological time endured about 800 
million years." And lately Baron Rayleigh and the 
physicists have been insisting that the story of the 
earth is a matter of at least 1,600 million years! 

That is a very delicate and difficult and unsolved 
problem. For my present purpose this does not 
matter, because relative periods of time will do. The 
geologist divides past time into Eras, and each of 
these is sub-divided into Periods. Each represents a 
certain group of rocks, the thickness of which is 
fairly well known, so that allowing for different 
rates of formation at different times the geologist 
roughly knows the length of one Era as compared 
with another. 

There are five of these Eras, corresponding to five 
levels in our fifty-two miles of rock. Now the modern 
geologist tells us that, if we represent the whole thick- 
ness (the whole of geological time) as 100, the 
proportion of each Era is as follows: 

The Cenozoic Era . . . . 5 

The Mesozoic Era . . . . 12 

The Palaeozoic Era . . . . 28 

The Proterozoic Era . . . . 15 

The Archaeozoic Era . . . . 40 

All the estimates work out at something like this, 
because the figures really express the thickness of 



64 THE FIRST TWO ICE AGES 

the known rocks. Well, the last Ice Age was at the 
end of the Cenozoic Era "the other day," one 
might say, on this scale of time. The previous great 
chill was at the end of the Mesozoic; the one before 
this at the end of the Palaeozoic; the preceding one 
at or before the beginning of the Palaeozoic. So far, 
for four Ice Ages, it is certain that the interval has 
been reduced by about fifty per cent, every time. 
There remains only the first Ice Age, and here esti- 
mates are uncertain and conflicting. But it occurred 
somewhere about the middle of the appallingly long 
Era (as long as all the others put together) before the 
Palaeozoic. 

That is a singular phenomenon. It not only sug- 
gests that the earth will be permanently covered with 
snow and ice in a few million years, because the inter- 
vals between Ice Ages will shorten until they disappear 
but it makes one suspect a machinery which is un- 
known to us. There is a sort of rhythm about it 
which excites curiosity. 

There is only one group of facts in modern geology 
which I can conceive as throwing some light on it. 
It is agreed that the abysses of the ocean are becoming 
deeper as time goes on. The floor of the seas is sink- 
ing, and we may presume that the land is rising. At 
all events, the land is much higher than it used to be. 
The facts are still not very well known, and it may be 
that the explanation is somewhere in this constant 
need of the mass of the earth to adjust itself to the 



THE FIRST TWO ICE AGES 65 

changing conditions. It seems to do so, not continu- 
ously, but by a mighty spasm of mountain-making at 
long intervals, and these give us our revolutions of 
climate or Ice Ages. 

But many readers will be disappointed unless they 
hear something about another theory of mountain- 
formation which was once very popular, though it 
seems nowadays in danger of joining "the astro- 
comical theory of Ice Ages" in the land of lost hy- 
potheses. However, it is by no means dead, much less 
damned, and it will serve to illustrate another aspect 
of the question. 

We all remember how it used to be explained that 
mountain chains are wrinkles, marks of old age, on 
the skin of our planet. An old man's skin becomes 
too large for his diminishing body, and it grows 
smaller by "wrinkling." So, it was said, the earth 
is cooling and contracting, age by age, and thus its 
skin (crust) becomes too large. It adapts itself to 
the smaller body of the globe by wrinkling; but the 
wrinkles go outward, instead of inward, as our skin 
does. 

This, again, is a picturesque and attractive theory, 
but it is rejected by a large number of modern geolo- 
gists. The rocky crust or skin of our earth is between 
fifty and sixty miles thick, and at one time everybody 
thought that the rest of the globe was molten matter 
at a very high temperature. We thought that the 
earth had once been a fiery mass of molten metal, 

5 



66 THE FIRST TWO ICE AGES 

a little sun, and had merely cooled at the surface. 
There is now a new theory in geology, that the loose 
stuff which was brought together to form our globe 
did not engender heat enough to make the whole mass 
molten; that it was only fiery and molten at the sur- 
face. On this view the great mass of the earth is solid 
and rigid, and cannot shrink to the extent that was 
once thought. 

In spite of the large number of distinguished geolo- 
gists who follow this (Planetesimal) theory, there is 
a good deal to be said for the older (Nebular) theory, 
and it is well to wait. Not only the sun and all the 
stars, but Jupiter and Saturn, are just as the old 
theory demands. But we must not go into those 
matters here. The geologists of the new school do 
not admit the "wrinkling." At the most they admit 
that some obscure changes are going on in the atoms 
of the heavy metals (uranium, radium, etc.) down 
below, and that these changes may co-operate with 
the causes we described in the work of forming 
mountains. 

Such, then, is the mechanism which indirectly 
leads to the Ice Ages. Now we have to consider the 
effect of the Ice Ages themselves upon life. Whatever 
obscurities may remain, we are getting a much more 
satisfactory knowledge of what we may call the 
machinery of the planet. And upon the action of 
this purely physical machinery the story of the slow 
advance of life has depended throughout the ages. 



THE FIRST TWO ICE AGES 67 

While philosophers and a few mystic-minded men of 
science have been working out theories of some vital 
force that sought its way upward a force far more 
mysterious and unintelligible than the facts it is 
invoked to explain science has been patiently work- 
ing out the real explanation. If I may use a rather 
exaggerated illustration, it is as if a race of creatures 
that had no sense of elevation that saw everything 
flat were watching the course of the Thames or the 
Hudson acrosss the country, and, wondering why the 
river followed this particular path, thought that there 
was some mysterious river-spirit or river-god that 
directed it. Then a man with normal vision conies 
along, and he explains that the course of the river is 
simply directed by the configuration of the ground. 
That is how science is now explaining the course of 
the river of life . 

Let me repeat that science does not say that it 
has explained the course of the life-river. There are 
people who accuse science in general, and its popular 
exponents in particular, of dogmatism. It is a quite 
false charge. When we have completely mastered 
the physical conditions of the evolution of life we 
have still a long way to go. We have then to explain 
the internal machinery, inside living things, which 
enables life to adapt itself to the changing external 
circumstances. This is being done, but more slowly. 
It is far more difficult. But we have not yet com- 
pletely studied even the external circumstances which 



68 THE FIRST TWO ICE AGES 

directed the evolution of life. I am merely giving our 
knowledge as far as it is settled, and showing how 
wonderfully illuminating it promises to be. 

The first two Ice Ages are the least known. That 
requires little explanation. We know an Ice Age by 
the scars it has made on the surface of the planet, 
and time is apt to remove them. Rocks on which 
glaciers scratched their signature are worn away. 
Beds of glacial rubbish are washed away by the sea or 
a great river. Fortunately, however, these memorials 
of Ice Ages are sometimes buried under strata which 
have escaped the war of the element ever since, and 
the inquisitive geologist of modern times has found 
them. 

But there was no life on land during the first two 
Ice Ages, and we will dismiss them briefly. As I have 
explained in The A B C of Evolution, the first half, 
or more, of the drama of evolution was played in the 
ocean. Life is a product of the water, probably of 
shallow seas, and in the water it remained until more 
than half the story of the earth was over. Early Ice 
Ages would, no doubt, affect even the marine popu- 
lation, though we do not trace this in the scanty early 
records ; but their agency is not important until there 
is life on land. However, to make complete the story 
of the Ice Ages themselves, we will see how these 
early revolutions are known. 

Four or five pages back I gave the list of the earth's 
"Eras." The lowest (and earliest) two, the Pro- 



THE FIRST TWO ICE AGES 69 

terozoic and Archgeozoic, are still sometimes combined 
as one, the Archaean (or Ancient Age), and we will 
take them together here. As the figures in my list 
corresponding to each Era show, this vast age repre- 
sents more than half the earth's story, although by 
the close of it life had not risen higher than the level 
of the worm and the starfish. The rocks of this age 
are, moreover, overwhelmingly volcanic. They repre- 
sent tens of millions of years of constant and pro- 
digious outpours of lava through and upon the thin 
crust. That is what we should expect, precisely 
because the crust was thin. 

Somewhere about the middle of this long fiery 
youth of the earth an Ice Age occurred. We have 
no traces of the original crust of the earth, the first 
skin of rock to be drawn over its molten body. But 
there are a few large sections of the face of the earth 
to-day which have been above water from primordial 
times, and one of these, which geologists call Canadian, 
is a very large part of the northeast of North America. 
The Canadian geologists have found that some of the 
beds in these formations point indisputably to the rise 
of vast mountains, followed by an Ice Age. There 
are great masses of boulder-clay (the scoured dust 
intermingled with blocks of stone), which have since 
been converted into rock. The boulders are rounded 
and scratched in the usual manner, and the quantity 
of the material points to a really great Ice Age. One 
bed alone is five hundred feet thick, and stretches 



70 THE FIRST TWO ICE AGES 

over a thousand miles. Geologists are agreed that 
this was the earth's first revolution, and that it 
corresponds with an age of mountain formation. 

We will not try to picture this glacial interlude in 
the fiery drama of the earth's early life. The record 
is too worn, too faint, for realistic pictures of those 
dim ages; and there was no land population to feel 
the selective action of the revolution. It is enough 
for our general purpose that there was incontestably 
a great Ice Age; that it is connected with the rise of 
chains of mountains ; and that, as far as we can place 
it, its chronological position is consistent with the 
curious law of diminishing intervals to which I have 
drawn attention. 

At the end of this very long Era (taking the Pro- 
terozoic and Archaeozoic together) there was a second 
Ice Age. From this point onward, in fact, the end 
of one geological Era and the beginning of another is 
precisely dated by a "revolution" a rise of moun- 
tains and great lowering of temperature. Generally 
speaking, the earth still enjoyed a very warm climate, 
a perpetual summer, from Pole to Pole. Corals, 
those pretty and delicate indications of warmth, 
swarmed in the seas all over the earth. Shell-fish, 
starfish, sea-lilies, sponges, jelly-fishes, and other 
lowly types filled the waters. There was still no fish 
or any dweller on the inhospitable land. 

There now occurred an Ice Age which covered 
widely distant continents with a glacial mantle. On 



THE FIRST TWO ICE AGES 71 

the theory we are following, ice sheets may be found 
anywhere during an Ice Age. They will occur 
wherever new mountains have arisen. We are there- 
fore not surprised to find that there were now ice 
sheets in Norway, in China, in India, in Australia, 
and in Africa. The beds of rock containing rounded 
and scratched boulders are from 600 to 1,500 feet 
thick in the south of Australia and Tasmania. There 
is a bed in China 170 feet thick. In Norway the bed 
rests on sandstone that was clearly scratched and 
grooved by moving ice. 

It is impossible to prove that rocks so distant from 
each other represent precisely the same age, but it 
suffices that they all belong, roundly, to the close of 
the Proterozoic Era and the beginning of the Palaeozoic 
(or, as a geologist would say, the base of the Cambrian 
Period). Seeing that the climate of the earth had 
been for millions of years previously, and was for 
millions of years afterwards, warm and uniform, these 
great stretches of ice in such different parts of the 
earth amount to an Ice Age. Cold winds and cold 
ocean-currents would spread the lower temperature 
far beyond the actual fields of ice and snow. There 
must have been a great destruction of marine life. 
It is not, however, until an Ice Age exerts its terrible 
influence on a land-population that we get the chief 
effect which I have ascribed to it, and we will pass 
to the next. 

We have in this case not the same evidence of 



72 THE FIRST TWO ICE AGES 

mountain-building as in the other cases; though we 
know that mountains arose at the time at least in 
America. The geological record of the time is poor, 
or is imperfectly known. But we shall see this so 
very plainly in connection with the later Ice Ages 
that we may assume the cause was the same in Cam- 
brian or Pre-Cambrian times. The earth passed 
through another of its crises or revolutions. The 
dragon of cold crept in between two prolonged periods 
of warmth, and the globe had another foretaste of 
its ultimate condition. 



CHAPTER V 

THE MIGHTY PERMIAN REVOLUTION 

FROM this point onward the story of the earth is very 
well known. Our generation is so much accustomed 
to the gigantic accomplishments of science that one 
may ask the reader to pause and appreciate what has 
been done. From some twenty miles deep of com- 
pressed stone indeed, from the comparatively few 
places where the hand of nature or of man has 
exposed these rocks to view geologists have deci- 
phered the story of the life of the earth and its living 
populations, during some tens of millions of years of 
past time, in marvellous fullness. The same rocks 
lay under the feet of the men of every previous 
civilization. The same quarries and cliffs exposed 
the secrets of nature to their eyes. Yet until little 
more than a hundred years ago few had even a dull 
suspicion of this buried chronicle, and none could 
read a single line of it as we do to-day. 

That story I have told in my earlier works, and 
I propose here only to add certain details and new 
discoveries concerning the Ice Ages. The most 
valuable part of recent geological work is the clearer 

73 



74 MIGHTY PERMIAN REVOLUTION 

perception of what I have already called the general 
mechanism of the earth, the struggle of the elements. 
When you read that the rivers bear so many thousand 
million tons of the land down to the sea every year, 
and that, if all the "dry land" were thus worn down 
and conveyed to the bottom of the ocean, the waters 
would rise 650 feet, you may be tempted to reflect 
on the misplaced ingenuity which has spent months 
over these stupendous calculations. But it is all part 
of the explanation of that drama of terrestrial life 
which, since the discovery of evolution, has attracted 
us more than ever. 

The next Ice Age we have to consider, the Permian 
Revolution, came after the age of the Coal Forests, 
and we will take these as a fixed and familiar point 
from which we may work. Everybody knows the 
meaning of our coal-beds. During one or two million 
years the earth bore forests of such denseness and 
continuity that the rotted wood has given us the 
immense masses of carbon in our coal seams. I will 
assume here that the reader knows that coal-beds 
occur in every continent, from the Arctic to the 
Antarctic, which shows that at least semi-tropical 
forests then flourished all over the earth; and that 
the Coal Forest implies low-lying, sodden land, with 
a hot steamy temperature and vast swamps. It was 
"the age of amphibia" in the record of animal life. 

We must bear in mind also that the forests had 
not suddenly grown thick during the Carboniferous 



MIGHTY PERMIAN REVOLUTION 75 

Period. The vegetation had been growing steadily 
denser ever since it had invaded the land. The "sea- 
weeds" became ferns and mosses, and these, finding 
ideal conditions for their growth, became larger 
individually, and denser collectively, until they ended 
in the rich, rank forests of our coal-beds. During 
many millions of years the earth had enjoyed a great 
warmth from Pole to Pole. There were periods and 
places of rise of the land, with dry and cool climate; 
but what I have given is the general aspect of the earth. 

It was the interval between two Ice Ages, the 
Palaeozoic Era, lying between (if the reader will turn 
back for a moment to the list on p. 63) the revolution 
which closed the Proterozoic Era and the revolution 
which opened the Mesozoic Era. And from what we 
have already seen we understand this. The Ice Age 
had been due to the rise of the land. But a rise of 
the land always brings about its own destruction. 
The rain falls more freely and heavily, as the moisture 
is chilled and condensed by the hill-tops. The streams 
and rivers run more swiftly, as the land slopes more 
steeply towards the sea. The frost and moving ice 
break up and scour away the mountains. When the 
ice sheets melt, the vast streams of water are very 
destructive. 

So the earth returns in a comparatively short time 
to its lowland condition, with a warm climate. The 
wearing of the land will now be much slower. 
Sediment will accumulate much more sluggishly on 



76 MIGHTY PERMIAN REVOLUTION 

the floor of the ocean. In this respect the war of 
land and water relaxes very considerably, and the 
critical reaction, the pressure against the land which 
causes new mountains, is long delayed. But there is 
another thing to be considered. The level of the 
water has meantime risen, on account of the thousands 
of millions of tons of worn land that have drifted into 
it just as surely as the water will rise in a pail if 
you put into it a handful of sand and pebbles. The 
oceans overflow the low-lying continents, creating 
great swamps and lakes, accentuating the warm, 
moist conditions. 

American geologists calculate that their continent 
has been thus flooded fifteen times since the Ice Age 
with which I closed the last chapter often to the 
extent of millions of square miles, and chiefly during 
the Era we are now reviewing. Nearly a dozen times 
during that Era the waters encroached upon the land 
until they covered sometimes from thirty to forty per 
cent, of North America. 

These changes are part of the external machinery 
of evolution, part of the great process which we call 
natural selection. When the sea spread far over the 
land there was an immense increase of marine life, 
as will be understood. When the land rose again to 
some extent and poured off the waters, all this new 
marine population was exposed to material changes 
of conditions and a fiercer struggle for existence. All 
such changes are very slow, we must remember, and 



MIGHTY PERMIAN REVOLUTION 77 

the animals and plants, or some of them, have time 
to be adapted to new conditions. This means that 
they evolve new organs. They pass into different 
species. It was during one of these temporary rises 
of the land a very extensive rise, but not acute 
enough to cause anything like an Ice Age that 
branches of the fish world left the water, and began 
the story of the quadrupeds. That interesting and 
important chapter, the struggle for air-breathing 
apparatus, I have told elsewhere. 

The next step to the fish is the amphibian, and the 
swampy earth of the Carboniferous Period suited this 
type. The land, or land-and-water world of those 
days, swarmed with amphibians, sometimes five or 
six feet long. But a new revolution was approaching. 
Four times during this Palaeozoic Era there had been 
a considerable rise of land in America, though it did 
not rise high enough to cause a revolution in climate. 
The masses of sediment were steadily accumulating 
along the shores of every continent, and the time 
of reaction, of thrust back towards the land, had 
arrived. 

In the case of this Ice Age one of the subsidiary 
causes also was very important. Whatever may have 
been the primitive condition of the earth's atmosphere, 
it is certain that it was heavily loaded with carbon 
dioxide during the Era we have just reviewed. The 
Coal Forests extracted a vast amount of this carbon. 
The carbon in our coal seams is two hundred times 



78 MIGHTY PERMIAN REVOLUTION 

the entire quantity there is in the atmosphere to-day; 
and the very thick beds of limestone associated with 
them mean (as limestone is a compound of carbon 
and lime) further enormous quantities drawn from 
the atmosphere. The air must have been extra- 
ordinarily thinned by the end of the Coal Forest 
period. When the land rose also, forming great 
ranges of mountains, the dense moisture in the air 
began to be precipitated. The conditions of an Ice 
Age were given. 

This Ice Age, which we call the Permian Revolution 
because it occurred at the beginning of what is called 
the Permian Period, was very intense, prolonged, and 
widespread in its influence. Its main theatre was, as 
I said, the land which then linked India, Australia, 
and South Africa. This was an ancient continent 
(known in science as Gondwana Land) of which we 
have the clearest evidence. Probably India was then 
not united to the rest of Asia the mountain mass of 
the Himalaya rose only millions of years afterwards 
but was the northern tip of this lost continent. From 
India the land stretched across what is now the 
Indian Ocean, and included the greater part of Africa 
and Australia. Indeed, part of it stretched across the 
Pacific to South America, and part to Antarctica. 

As we find the chief traces of the Permian Ice 
Age in India, Australia (mainly Queensland, South 
Australia, Victoria, and Tasmania), and South Africa 
the fringes of this lost continent we take it that 



MIGHTY PERMIAN REVOLUTION 79 

Gondwana Land was the leading ice-field. The 
memorials of it are such as I have already described. 
In Central India and down into the tropics we have 
mighty beds of the kind of glacial rubbish, mixed 
with boulders, which I described, and the rocky 
surface below this stuff is grooved and polished by 
heavy moving ice. Other beds are now raised (by a 
later elevation) high up on the Himalayas and in 
Afghanistan. 

In Australia we have the same beds in great thick- 
ness. I told on an earlier page of having seen these 
memorials of an Ice Age in the Werribee Gorge in 
Victoria. In this district the evidence is particularly 
interesting. It shows that the Ice Age consisted of 
a succession of cold periods with warmer intervals. 
There are even thin seams of coal and marine beds 
between glacial deposits, showing that the climate 
became warm again, and the sea overran the land. 
It will be remembered that I suggested a picture of 
the land, during an Ice Age, sinking to a lower level 
under its colossal burden of ice, then rising again 
when the ice melted, and receiving a new burden. 
These "inter-glacial periods" are, however, not yet 
absolutely settled in science. 

In Africa we have the same indications, and in such 
abundance that we need not fear to speak of a great 
Ice Age. There are glacial beds 1,300 feet deep in 
Natal, and very thick beds in Cape Colony. In fact, 
the ice-sheet practically covered the area which we 



8o MIGHTY PERMIAN REVOLUTION 

called British South Africa in 1914. And the vege- 
tation is so similar to that of contemporary Australia 
and India that we safely assume they were parts of 
one continent. We have the same hardy types of 
ferns and the same glacial indications in Argentina 
and Brazil, the western limit of this lost continent. 

But in many other parts of the earth also there 
were ice-caps. Neither of the astronomical specu- 
lations we noticed in the least fits the facts of this 
very well-known Ice Age. There was nothing like 
polar caps. Apart from the ice that stretched from 
North India to Cape Colony and Tasmania, there was 
the ice in Brazil. Then there was so much ice in 
eastern North America that American geologists prefer 
to call this Ice Age the "Appalachian Revolution"; 
and there are further glacial indications of this date 
in England, Germany, and Bohemia. 

Of the cause in this case, apart from the great 
absorption of carbon, we can have very little doubt. 
It was one of the great ages of mountain-formation. 
A chain (the Palaeozoic Alps) stretched from Ireland, 
through Wales and the south of England, to France. 
Another chain (the Variscian Alps) stretched from 
France to Bohemia. There were other chains in 
Armenia, India, Malaysia, Australia, Africa, and 
America. In North America the western or Pacific 
coast spluttered with volcanoes, while the eastern 
fringe rose in a chain of mountains (the Appalachian 
mountains, from about New York to Georgia), which 



MIGHTY PERMIAN REVOLUTION 81 

are estimated to have reached a height of 20,000 feet, 
or far higher than the Swiss Alps are to-day. The 
ground-up remains of the range now lie, 40,000 feet 
thick, in a deep trough alongside the site of the old 
mountains. 

It was a fresh crisis in the physical fortunes of the 
planet. Whatever share shrinking, or atomic changes 
under the crust, may have had, the ten million years 
or more of wearing away of the land and piling 
material on the ocean-floor explain a good deal. The 
ocean-basins may have sunk deeper, thus permitting 
masses of water to drain off the flooded continents. 
There was, in sum, an immense gain of the land 
upon the water, and a considerable rise upward of 
parts of the continents. From the picture we have 
drawn of the earth previously to this stage, it will be 
understood that there was a colossal amount of 
moisture to condense into snow and ice. This with- 
drawal of moisture, coupled with the extraordinary 
withdrawal of carbon that had proceeded for over a 
million years, greatly thinned the atmosphere, and 
allowed the heat to escape. There was more dry 
land than there had ever yet been in the story of our 
planet, and there was a thinner air to "blanket" it. 
It was like passing from the thick warm atmosphere 
of Geneva to the summit of one of the Alps beyond. 

I have so fully described in earlier works the effect 
upon life of this revolution in climate that a short 
summary will suffice here. But before I do so, let 

6 



82 MIGHTY PERMIAN REVOLUTION 

me make an observation that may help to relieve the 
perplexity of many readers. Evolutionary literature 
is in our time so full of flat contradictions that the 
casual reader is puzzled, if not pained. He reads 
that Darwinism and natural selection are now unim- 
portant, if not superseded. He learns that "environ- 
ment," to which we once attributed so much, is now 
a very subsidiary matter. He must even feel some- 
times that environment is negligible, and that the 
mechanism of heredity is what matters overwhelm- 
ingly in evolution. 

All these statements are grossly one-sided. Recent 
science has made a great advance in the study of the 
mechanism of heredity, and some of those who are 
engaged in this study lose their sense of proportion. 
Environment alone could not explain evolution unless 
it directly altered the features of living things, and 
they transmitted these features to their offspring. 
If, for instance, cold itself provoked a coat of fur or 
feathers on an animal, and this "acquired modifica- 
tion" were handed on to the next generation, we 
should have an explanation of the change of species. 
That is properly drawn out and spread over a great 
period Lamarck's theory; but no one now admits 
it in this form, and few admit either of the two 
propositions I have stated 

Darwin's idea was quite different. He assumed 
that some internal cause brought about differences 
between young and their parents, or "variations." 



MIGHTY PERMIAN REVOLUTION 83 

He repeats constantly that he takes these variations 
for granted; and I have quoted him saying that he 
believes external causes have very little to do with 
variation. But science in his time knew very little 
about the internal or embryonic cause, and Darwin 
chiefly occupied himself with what followed. Environ- 
ment " selected" those variations which were favour- 
able to the possessor. On a white background, for 
instance, the chances of survival are against a dark 
animal; on a dark background they are against 
a light animal. That is one feature out of myriads. 
So, if the young differ constantly from their parents, 
the environment often has a good deal to say to the 
variations. 

Since that time we have learned much about the 
embryonic machinery, although we are very far from 
having mastered it. Unfortunately, some of the 
students of heredity use language which seems to the 
general public to mean that all the older study of 
environment was useless. On the contrary, it has 
not lost a single particle of its value. Internal forces 
alone can no more explain evolution than external 
forces could. If we supposed that there was some 
internal force which pressed life on from the level of 
the fish to that of the reptile, then to that of the bird 
or mammal, we should be taking refuge in a mysticism 
that really explains nothing and is not science. If 
we supposed that this internal force caused the fish 
to develop into a reptile (through the amphibian 



84 MIGHTY PERMIAN REVOLUTION 

stage) without regard to the fact that meantime the 
land became higher and drier that the same mystic 
force converted the reptile into a bird without regard 
to the Ice Age which now occurred we should be 
guilty of an outrage on common sense. 

Both factors, internal and external, were essential 
to the evolution of life. We want the internal power 
of growth and the external pruning and shaping 
forces. Without the rise of the land in the Carboni- 
ferous Period there would have been no reptile. If 
the embryonic forces had produced one, the external 
conditions of the Coal Forest Age would have de- 
stroyed it. Without the further rise of the land to 
the extent of causing an Ice Age there would have 
been no bird or mammal. If they had arisen, from 
purely internal causes, they would not have found 
the conditions of survival. The physical story of 
the earth has guided and shaped the course of the 
life-story just as the land-conditions direct the course 
of a river. That is Darwinism, or the origin of new 
species by selection. Theories of heredity are supple- 
mentary to this, and we are as yet much less confident 
about them. 

The Permian Revolution itself is one of the clearest 
illustrations of this. The reptile appears just before 
it sets in. That is to say, the land is beginning to 
rise and, as the waters are drained, amphibian life 
becomes less easy or even, in places, impossible. 
In some such region the amphibian loses its gills 



MIGHTY PERMIAN REVOLUTION 85 

and becomes a reptile. The amphibians in nature 
to-day show how easily this would occur. The frog 
loses its gills, but keeps mainly to the water; but in 
a waterless region it is a pure land-animal some- 
times a tree-animal and almost has no tadpole stage. 
There are, on the other hand, amphibians (the 
axolotls of Mexico) which retain the gills all their 
life, and never live on land, because their water- 
conditions are excellent We can even control the 
development of amphibians by giving them either a 
land or a water environment, as we wish. They 
show the most perfect interplay of internal forces and 
environment. 

But the reptile, if it requires dry land for its 
original development, requires also warmth. It is 
cold-blooded and cold-coated, and it does not warm 
its eggs. Hence, when the land continued to rise at 
the close of the Coal Forest Period, the development 
of the reptiles was checked. As a rule, when a 
higher type of life is evolved it enjoys a period of 
great prosperity. Its individuals run to a great size 
there were once oysters a foot in diameter and 
sharks thirty feet long and the whole family is rich 
in numbers and variety. But the reptile family was 
checked by the increasing cold, and its great expan- 
sion was postponed until the Ice Age was over. To 
try to disconnect these things from environment is 
obviously foolish. 

The Permian Ice Age may have lasted a quarter of 



86 MIGHTY PERMIAN REVOLUTION 

a million years. If we bear in mind the extraordinary 
area it covered, and remember that cold winds and 
cold currents would go far beyond the ice-fields 
that, in fact, there was probably a winter season over 
great stretches of country that were not glaciated 
we see that the greater part of the earth was subjected 
to a heavy trial. There had been, remember, no 
ice, no snow, and no winter anywhere on the earth 
for something over ten million years. Every branch 
of the living world was adapted to warmth. There 
were, no doubt, broad regions which remained quite 
warm, but over a very great part of the earth the 
living population was put to the test of natural 
selection in its most terrible form. 

For the majority it was an unmitigated catastrophe. 
How do we know? Geologists compare the species 
of animals and plants which they find fossilized in 
the later Coal measures, before the revolution, with 
the species they find in the rocks at the close of the 
Ice Age. Thirty-nine out of every forty species have 
disappeared. Many new species have appeared, of 
course; some of the old species have passed into 
higher forms. But even these changes, under the 
influence of an Ice Age, involve an immense carnage 
of individuals. It was a period of the most terrible 
destruction of life. Had there been reptile philo- 
sophers and theologians, they would have pronounced 
it "the crack of doom." They would have lamented 
that their race, the flower of creation (as they then 



MIGHTY PERMIAN REVOLUTION 87 

were), had only just reached supremacy in time to 
witness the end of the world. 

But the earth had still tens of millions of years to 
offer to its living inhabitants. The ice slowly reached 
its culminating point, and then slowly receded. If 
there were inter-glacial periods, warmer (or less cold) 
periods between successive spreads of the ice-caps, 
we can only think that they would add to the severity 
of the trial. Animals would spread out from the 
warm regions, which would obviously become densely 
populated, and they would be fairly established in 
the new lands when the stress of the glacial conditions 
would fall upon them again. 

I must, however, refer the reader to my A B C of 
Evolution for an account of the way in which the cold 
conditions would act. Here it is merely necessary 
to emphasize the slowness of these changes, which 
the inexpert find it difficult to grasp. Take a glaciated 
region like Australia. Now we are less disposed than 
ever in science to give chronological figures ; not that 
the old figures were excessive, but because they are 
probably far short of the truth, and they are in any 
case very uncertain. But no one would imagine that 
the change from Coal Forest conditions to glacial 
conditions in Australia took less than ten thousand- 
years. This is, of course, not a suggestion of any- 
thing like the actual period. It is a figure that we 
can safely say is not large enough; though it is 
longer than the whole stretch of civilization. 



88 MIGHTY PERMIAN REVOLUTION 

If you spread an average fall of temperature of, 
say, twenty degrees over ten thousand years, you 
realize what a great opportunity is given to the 
adaptive powers of organisms. A thousand genera- 
tions of reptiles, ten thousand generations of ferns, 
would appear in that time. Every variation in the 
direction of protection of the animal and its eggs 
from cold would be favoured. There was time enough 
for the very large changes which are involved in the 
evolution of reptiles into birds and mammals; and, 
as I have described in detail elsewhere, the earliest 
birds and mammals which were obviously transformed 
reptiles, appeared at the close of the Ice Age. The 
plant world was in large part similarly transformed. 
The primitive ferns and club mosses of the Coal 
Forests disappeared. The pine and the yew, 
the cycad and other new types, spread over the 
earth. 

By the time the Ice Age was over life had been 
lifted to a distinctly higher level. It is not too much 
to say that more progress more advance towards the 
higher types of life had been made during that 
quarter of a million years (to use a rough estimate of 
the entire period) than during several million years 
that had gone before it. There had been a revolution. 
But the word "revolution" must not mislead us. 
Measured by our familiar standards of time, it was 
still a period of very slow evolution. The point is that 
evolution is by no means uniformly slow. During 



MIGHTY PERMIAN REVOLUTION 89 

these revolutionary periods its pace increases con- 
siderably. 

And the increase the swifter advance towards the 
higher level is due to external, not internal, causes. 
We have no reason to suppose that the changed 
environment provokes the embryonic machinery to 
act, to produce variations, more rapidly; and, even 
if we had, this would be action of the environment. 
On the other hand, to suggest that the internal factors 
happened to produce variations more abundantly 
during these externally revolutionary periods would 
be mysticism with a vengeance. There was once a 
religious philosopher who, despairing of finding any 
explanation of the influence of spirit on matter, and 
vice versa, said that the two sets of causes, spiritual 
and material, just happened to coincide. When you 
felt angry, your body was so nicely "wound up," as 
it were, to keep time with the spirit that it showed 
anger when you felt anger; but the mind did not 
influence the body. We can scarcely admit this sort 
of thing in science. The internal and external factors 
work intimately together. Natural selection is of 
fundamental and universal importance. 



CHAPTER VI 

THE COLD THAT SLEW THE DRAGONS 

THE reader must not suppose that in the rocks which 
represent the Permian Revolution we find reptiles 
gradually evolving in the direction of the bird and 
the mammal. Not only do we not find these interesting 
stages preserved, but we have very few traces indeed 
of birds or mammals during several million years 
after the Ice Age; and the first traces we have are 
much later than the Ice Age. The bodies of land- 
animals are rarely preserved. They usually lie on 
the soil until decay and bacteria have disposed of them. 
If one reflects how many hundreds of thousands of 
birds must die in England every year, yet how few 
bodies of birds one sees, this fact will hardly need 
further explanation. The scavenging department of 
nature is very efficient. 

But the first birds and mammals which we do find 
are of such a character that it is impossible to doubt 
their reptilian ancestry, as I have elsewhere explained. 
For a very different reason it is equally impossible to 
doubt their connection with the Ice Age. The whole 
transformation of a reptile into a bird or mammal is 

90 



COLD THAT SLEW THE DRAGONS 91 

an adaptation to cold. It means, especially, three 
things warm blood, a warm coat, and warmth for 
the eggs or young. One might, of course, suggest 
that they were evolved in some period of cold that 
was later than the Ice Age. As a matter of fact, 
there was a restricted but severe chill in the geological 
period immediately following the Permian. It is as 
if, in some part of the earth, the crust failed to rise at 
the appointed time and the formation of a certain 
mountainous region, with the inevitable chill, was 
delayed. Obviously, however, the prolonged Permian 
Ice Age is the most natural period in which to place 
the main part of the evolution of the mammal and 
the bird. 

The Ice Age slowly ended. The earth returned to 
its universal warmth. A new "golden age" opened; 
if warmth and abundance of food mean a golden age. 
But pleasant ages of that description are reactionary 
ages. Again, the social student need not take alarm, 
for we are speaking here always of the conditions of 
life of unintelligent animals. For those the spur of 
adversity is necessary. 

Golden ages have their own machinery of evolution. 
Plants and animals multiply so prodigiously that they 
come at last to a keen competition with each other. 
Picture the condition at the close of the last Ice Age. 
At least four million square miles of land were restored 
to what we may broadly call purposes of pasture. 
They were again covered with a rich vegetation, for 



92 COLD THAT SLEW THE DRAGONS 

there was still no winter suspension of life for the 
plants. Moreover, the temperate zone round the 
glaciated region returned to semi-tropical conditions. 
It is important always to bear in mind this great 
fringe of territory, with greatly reduced temperature 
and vegetation, round the actual region of ice and 
snow. It enormously extends the influence of the 
Ice Age. With the return of the sun, the whole of 
these vast regions would once more be clothed with 
vegetation, and the animals, spreading out from the 
restricted zones in which they had sheltered, would 
grow to a great size individually and to very large 
numbers collectively. They would breed astonish- 
ingly. Over-population, rivalry, and carnivorism 
would follow. 

But, in spite of its perennial interest, I must 
abstain entirely from telling again the story of the 
giant reptiles which now covered the earth. Several 
million years passed, during which progress consisted 
almost entirely in the growth of arms and armour. 
It was the progress of war time a pitiful waste of 
resources and time from any higher point of view. 
It is generally called "the Age of Reptiles." One 
might almost call it "the age of teeth." Sharks 
developed fearsome triangular teeth five or six inches 
long. Flying reptiles got more than two hundred 
ugly fangs in their jaws. Evolution, certainly, but . . . 
We almost prefer to contemplate an Ice Age. 

At all events, that is what we are going to do here. 



COLD THAT SLEW THE DRAGONS 93 

We are going to skip this long time of carnage and 
stupid bulk and come to the next revolution in 
climate. The story of the earth which underlies and 
directs the story of life is just the same as we have 
seen previously. The mountains which caused the 
Ice Age were worn down. The earth returned 
generally to a lowland condition, to a predominance 
of the water over the land. One has to remember 
that the earth as we know it to-day has higher land 
and more variety of scenery than it had in the past. 
It is only about thirty thousand years since the end 
of a very great Ice Age. The mountains are still 
lofty, and the ocean abysses are deeper than ever. 
During the Age of Reptiles the land was generally 
very low and swampy, the climate very warm and 
moist, the area of water enormous. Most of Europe 
was under water, and a marshy continent stretched 
from Europe to North America, which also was largely 
under water. The giant reptiles probably lived mainly 
in water, like hippopotami; many of them were 
exclusively aquatic animals, as the whale is to-day. 

In a word, the key to the puzzling story of life is, 
as usual, the physical story of our globe. The man 
who starts on hearing such an explanation, and calls 
it "Materialistic," is like a horse jibbing at a flying 
newspaper on a windy day. Materialism may or may 
not prove to be the final truth, but in the meantime 
the unravelling of these material factors or conditions 
of progress is decidedly illuminating. We leave open 



94 COLD THAT SLEW THE DRAGONS 

the question of the internal machinery of progress 
until science is much better acquainted with it. But 
we do see that any man who tries to tell us that a 
"vital principle" was working out the course of 
evolution on a definite plan is playing with words. 
At every step this course of evolution is conditioned 
by changes in the physical world which cannot 
reasonably be connected with any sort of plan. 

This was plain enough as regards the first appear- 
ance of the bird and the mammal. One would almost 
say that it was dictated by the physical changes in 
the earth itself understanding, of course, that the 
response of life would have been quite impossible 
without some remarkable machinery in the animal 
which could bring about the new adaptations. It is 
just as plain in regard to the next great stride in 
evolution: the extinction of the great reptiles and 
the triumph of the mammals and the birds. 

According to the table which we gave on a previous 
page, the Age of Reptiles was, in duration, about 
one-eighth of the entire story of the earth. What 
that means in positive figures we cannot yet say; 
estimates range from ten to a hundred or two hundred 
million years. It is, as I said, the radiologists who 
give us the highest figures, and one does not like to 
accept them until the evidence is more extensive 
and unquestioned than it is; but even the geologist, 
Professor Schuchert, would make this age (the Mesozoic 
Era) about a hundred million years. 



COLD THAT SLEW THE DRAGONS 95 

It is another vivid reminder how the progress of 
life waits upon the physical accidents of the earth. 
The highest types of life, the mammal and bird, were 
born about the beginning of the period. They had 
no advantage, however, when the ice disappeared 
and the earth became warm again. They remained 
half-formed, as it were. The bird remained half a 
reptile with long tail, and with toes on the end of 
its front limbs for millions of years; and it still had 
teeth in its jaws near the close of this long period. 
The mammal remained at the level of the Australian 
Platypus (which lays eggs) and the kangaroo (a primi- 
tive mammal) right to the close of the period. Birds 
and mammals were comparatively scarce, and they 
did not multiply into a great variety of types. To 
them the "golden age" of the reptile was a period of 
great adversity. They had in them the germs of the 
highest types of life, yet they made infinitesimally 
slow progress during these tens of millions of years. 
The whole higher promise of life awaited a change of 
climate. 

It came slowly and gradually in the last part of 
the Era. Most of Europe south of Scandinavia was 
under water, though large islands, surrounded by 
beautiful coral beds, rose above the warm ocean. An 
open sea spread from the south of England to the 
Indian Ocean. The chalk beds which extend over 
this area mainly consist of remains of microscopic 
animals and plants which lived in the shallows of 



96 COLD THAT SLEW THE DRAGONS 

this sea, and covered themselves with coats of lime. 
They enable us to trace the extent of the sea. They 
are, to the general public, the most striking beds of 
the time, and, although geologists do not now regard 
them as the most important, they still give their 
name to the period. It is called the Cretaceous 
(or Chalk) Period. 

This was the period of the next revolution, and, as 
I have said that we must hesitate to call it an Ice Age, 
it is necessary to say very precisely what happened. 
We know that there was a great rise of the land. 
After what we have already seen, we might infer this 
from the profound changes in the kingdom of life, 
which now experienced one of its greatest revolutions. 
But in order to avoid all appearance of arguing in a 
vicious circle, we will take the rise of the land as it is 
determined by geologists, quite apart from the fossils 
entombed in the rocks. The method requires little 
explanation. Where, as in so many parts of England, 
the chalk is at the surface, we know not only that it 
has been lifted up from the bottom of a shallow sea, x 

1 It used to be thought that the shells or skeletons of minute 
animals (Foraminifers) and plants (Algae), which chiefly compose 
the chalk, formed at one time an ooze at the bottom of the deep 
sea. This is not now considered to be the case. The explana- 
tion of the seams of flints which occur so often in the chalk may 
interest many. The chalk-mud or ooze at the bottom of the 
shallow sea would naturally contain abundant remains of sponges. 
It is thought that, after the chalk had been raised and converted 
into dry land, the rain-water percolated into it and dissolved the 
silica in the sponges, which was then deposited or concentrated 
in the form of flint. 



COLD THAT SLEW THE DRAGONS 97 

where the skeletons of the chalk-animalcules gathered, 
but that it has remained above sea-level ever since 
(unless we can trace beds which have been washed off 
it). Hence the mud must have been raised up, by an 
upheaval of the crust generally, at the close of the 
Chalk Period itself; otherwise later deposits would 
lie upon it. In the same way we can tell that a great 
part of Europe and America rose at the close of the 
Chalk Period. No later deposits have been laid upon 
it, as would inevitably be the case if it had remained 
longer under water. 

We can, in fact, learn that there was a very con- 
siderable disturbance of the earth's crust in the later 
part of the Chalk Period. There was an immense 
amount of volcanic activity. The west coast of 
America, in Chile and from Mexico to Canada, flamed 
with volcanoes. In India there was one of the 
greatest outpours of lava that can be traced in the 
geological chronicle since what I called the fiery 
youth of our globe. The hardened lava spreads over 
200,000 square miles, and is in some places a mile in 
thickness. So much may be quoted by those who 
think that a veil of fine volcanic ash in the upper 
atmosphere may be a cause of glaciation, but it is 
very difficult to imagine this ash remaining during 
anything like the long period of an Ice Age. 

In other places we have the plainest indications 
that the land was rising. In the preceding chapter 
we saw that a range of mountains, the Appalachian 

7 



98 COLD THAT SLEW THE DRAGONS 

(from New York to Georgia) rose in the eastern part 
of the United States, and was worn down again after 
the close of the Ice Age. The material, which had 
been laid in beds or strata under the sea, was now 
again crumpled into a lofty range of mountains. In 
the west of America, where the terrific volcanoes 
evinced a great disturbance of the crust, mountain- 
building was very conspicuous. It was the time of 
the birth of the vast mountain-system which spreads 
from Cape Horn to Alaska. The Cordilleras, the 
Andes, the Antilles, and the Rocky Mountains 
lumbered slowly upward, though they did not reach 
the height which we shall find them reaching on the 
eve of the next Ice Age. One range, the Laramide 
Mountains (in the region of Wyoming and Colorado) , 
is believed to have reached a height of 20,000 feet. 
Fifty miles of the earth's crust were here crushed and 
pleated into one-half that distance. The North 
American continent, generally, rose from the waters 
which had long covered it. In fact, American geolo- 
gists speak of this as "the Laramide Revolution." 

There was a similar, though less extensive, rise of 
the land in Europe and Asia. The Alps and the 
Pyrenees began to rise. The waters of the warm 
coral sea, with giant sharks and reptiles, that had 
for millions of years covered the greater part of 
Europe, were to a large extent shaken off, or drained 
into the ocean depths. Switzerland, until then at 
the bottom of the sea, began to contract into the 



COLD THAT SLEW THE DRAGONS 99 

huge folds which we know as the Alps. The Himalayas 
began to rise at the same time. The Chalk ocean 
which had spread from England to India, and south- 
wards deep into Africa, was broken up by rising 
stretches of ground into a series of seas or lakes. 

In other words, nearly all the principal mountain 
chains which we know to-day or the worn stumps 
of which we know were born at this period. But in 
nearly every case they failed to reach their full 
height. In the earlier (Permian) revolution of 
climate we had what we may call a complete opera- 
tion of mountain-building. In this case we have an 
incomplete operation. The rise of the land was very 
massive and extensive, but generally not so high as 
it had been in the Permian, and would be in the 
later, revolution. The formation of our great ranges 
of mountains was to be spread over millions of years. 
There was a mighty beginning in the later stages of 
the Cretaceous Period. Then we shall see there would 
be periodic advances during the warm period that 
followed, and finally a vast elevation that culminates 
in an intense Ice Age. 

This helps to reconcile us to the fact that the 
present revolution in geology and in climate was not 
accompanied or followed by what we can definitely 
call an Ice Age. There was, as far as we have yet 
discovered, no immense field of ice and snow covering 
millions of square miles. It is not at all true that, 
as one sometimes reads, there was no "glaciation." 



ioo COLD THAT SLEW THE DRAGONS 

European geologists found long ago that there were 
glacial beds in the region from Vienna to Bavaria, 
and that the boulders in these beds came, not from 
the Alps, but from a range of mountains in the 
neighbourhood of Bohemia. There was obviously 
a remarkable change in the climate of Europe. 
Where blue coral seas had hitherto smiled in the 
sun, there were now broad and deep rivers of ice 
pouring sluggishly upon the plains. 

Only in recent years (1913) similar glaciation has 
been discovered in America. Beds from eighty to 
a hundred feet thick were traced in Colorado, and 
the boulders must have come from mountains forty 
miles away. Professor Schuchert says : 

"It is to be expected that other areas of these 
tills will be found, in which event it will appear 
that the Laramide Mountains were then widely 
covered by Alpine and Piedmont [broad-fronted] 
glaciers." 

This snow-covered range, pouring large glaciers forty 
miles over the land (and therefore immensely larger 
than any in Switzerland to-day) must have made an 
impression on the climate of North America. 

It will now be clear what I meant when I ventured 
to call the period an Ice Age, but one not in the same 
category with the other Ice Ages. It was rather a 
period of chill, a very extensive and deadly chill in 
Europe and North America. Again we may note 



COLD THAT SLEW THE DRAGONS 101 

that there was nothing in the least like polar caps 
nothing to lend the feeblest countenance to the old 
astronomical theory and that the ice occurred simply 
where there were the greatest elevations of the land. 
The whole of the facts are, therefore, consistent with 
the theory we have accepted. By the very general 
alteration of the elevation of the land the atmosphere 
was put into more energetic circulation, and its high 
proportion of moisture was reduced by falls of snow 
and rain. But the new mountains do not seem to 
have been high enough, as a rule, or the moisture 
not great enough where the land was high, to form 
a great ice-cap anywhere on the earth. A cold 
period, but not strictly a glacial period, followed. 

And this was the chill that slew the dragons of 
the earlier Era. There has been a good deal of 
speculation as to the identity of the St. George that 
did this remarkable amount of dragon-slaying, but 
every agency that has ever been suggested, except 
cold, is ludicrously inadequate. Early mammals of 
the type of the innocent duckmole and the almost 
equally inoffensive kangaroo had no chance against 
twenty-ton reptiles, armour-plated from snout to 
tail, or flying reptiles with two hundred ugly teeth; 
to say nothing of the fact that it is not clear that 
carnivorous mammals (except insect-eaters) had yet 
appeared. Speculations about the disappearance of 
the race of giant reptiles from internal decay are 
just as unsatisfactory, and just as superfluous. 



102 COLD THAT SLEW THE DRAGONS 

The physical change of the earth itself is the 
obvious explanation. There had been very rich and 
luscious vegetation on the warm, low-lying, watery 
earth of the earlier Era. The monstrous size of the 
reptiles themselves is proof enough of that. When 
the earth, in Europe and America, was raised and 
drained over so enormous an area, there would be 
a proportionate thinning of the vegetation. But the 
cold had a more direct effect. The climate of Europe 
and North America became less and less suitable for 
reptiles. In particular, the mother reptiles provide 
no warmth for their eggs, and the cooling earth 
would no longer suffice to hatch the eggs. The turn 
of the bird and the mammal, which were especially 
evolved to meet cold conditions, had come at last. 
The river of life entered upon a new stretch; and 
nowhere in its whole course is it plainer that the 
material circumstances guided the flow. 

Apart from this negative evidence the general 
extinction of the reptiles, at least the larger reptiles, 
in Europe and North America we have abundance 
of positive evidence of cooling climate. The modern 
type of tree, the hard-wood flowering tree (oak, 
beech, etc.), began to spread over the northern 
hemisphere. The plant world, as well as the animal 
world, entered upon its modern development. 

The remains of plants which we find in the lowest 
and earliest beds of the Chalk series show that the 
earth still possessed its old type of climate. We 



COLD THAT SLEW THE DRAGONS 103 

should certainly not say that it was just as warm at 
the Poles as in other latitudes, but it was so warm 
there had been all the time except during the Ice 
Ages that the same vegetation grew at the Poles 
as in other regions. There is no difference between 
the trees of the coal-seams in the Arctic and Antarctic 
Circles and the trees of the Australian or English 
Coal Forests. Early in the Chalk Period, however, 
we begin to find a difference. We can see that there 
are zones of climate; that the vegetation farther 
north differs from the southern vegetation. And the 
main difference is that farther north there is a spread 
of the flowering trees which shed their leaves an- 
nually. 

How these were evolved, and what the precise 
meaning of this annual fall of the leaves is, we cannot 
repeat here. It is enough to say that they mean a 
cold season of the year, a winter season. No such 
season can be traced earlier in the story of the earth. 
Now we know unmistakably that it has set in, for we 
find the fossil imprints of leaves of such trees, and 
also tree trunks with annual rings of growth. Fossil 
trees, three feet thick, have been found in the Arctic 
Circle with no less than two hundred and ten rings, 
indicating so many winter seasons. They belong to 
this period. At the same time the corals, which are 
very sensitive to cold, disappeared from the polar 
regions, and even from North Europe. We have no 
reason to suppose that corals are more sensitive to 



104 COLD THAT SLEW THE DRAGONS 

cold to-day than they were formerly, yet we now 
have them almost confined to the tropics. Their 
retreat from higher latitudes at the time we are 
discussing tells us what the climate of the earth had 
been up to that time, and what a change was taking 
place in the Chalk Period, as the masses of the land 
slowly rose out of the deep. 

Thus our Cretaceous Ice Age, although so much 
less acute than the others, was not less important in 
its influence upon the evolution of life. A veritable 
revolution occurred. At the time, no doubt, it would 
have seemed, if there had been observers, a painfully 
slow evolution. The progress would be no more 
evident than it is to-day. But to us who find the 
life-story condensed into a few thousand feet of rocks 
the change seems enormous. The face of the Northern 
Hemisphere was transformed. The older types were 
annihilated on a colossal scale. Birds and mammals 
replaced the reptiles; modern trees and shrubs 
replaced the cycads* and other ancient forms of 
vegetation; grasses began, for the first time, to cover 
the plains. 

The transformation seems to have begun in America. 
With the great rise of land which we described, whole 
regions which had lain under water were drained and 
dried. Coarse sedges, the forerunners of the familiar 
grass, developed in the beds of the former lakes or 
inland seas. On the rising and cooler ground the 
old types of trees could not prosper, and such trees 



COLD THAT SLEW THE DRAGONS 105 

as the willow, elm, oak, and maple overran the land- 
scape. In the course of the Cretaceous Period itself 
there also appeared the magnolia, laurel, holly, fig, 
plane, birch, beech, walnut, hazelnut, and many 
others. From America they spread to Greenland, 
and some time afterwards they appeared in Portugal 
and pushed over Europe. From Greenland to Portugal 
seems a long jump for the plant-world, but there still 
existed across the North Atlantic a connection between 
America and Europe. We may suppose that this 
"lost continent" was elevated in the Chalk Period 
we may even suspect that it may have in it some 
of the missing evidence of glaciation and the new 
forests and grasses slowly travelled across it to Europe. 
Such travels are easily accommodated in the long 
periods of geological time. 

Just as I write this page I receive press-cuttings 
that tell how a distinguished English professor has 
been saying to the great joy of narrow-minded folk 
that the Darwinian era is over and discredited, and 
that we face the problem of the causes of evolution 
almost as blankly as ever. Such language is unfor- 
tunate and misleading. The reader will judge for 
himself whether the material of these chapters does 
or does not throw light upon the evolution of life, and 
whether the explanation is not on the main lines of 
Darwin's teaching. The professor in question is so 
exclusively devoted to the internal causes of evolution 
the causes of variation which baffle him, that he 



106 COLD THAT SLEW THE DRAGONS 

ignores what has been done in the study of environ- 
ment; as if the evolution of life had proceeded on its 
own lines in sublime indifference to these mighty, 
significant, and most illuminating physical changes 
in its environment! However eager we may be to 
solve the dark problem of heredity, or defend any 
particular view of it, we need not slight the brilliant 
work that has been done in making clear the selective 
action of the environment. 



CHAPTER VII 

THE ICE AGE THAT MADE MAN 

UNTIL the period of great chill which we described 
in the last chapter, the entire earth had been warm 
all the year round. Periodically, at intervals of 
millions of years, a large part of the surface was 
glaciated, and the climate generally affected; but 
after each of these temporary intrusions of cold the 
earth had returned to a warm climate. There were 
no arctic circles, no temperate zones, no cold winters. 
At the end of the Cretaceous Period we find a marked 
change. The earth was cooling at the Poles, and in 
the temperate zone there was the annual chill which 
we call winter. 

Yet the earth returned to a degree of warmth which 
we enjoy no longer to-day. As I stated in an earlier 
chapter, we find under the snows of Spitzbergen the 
frozen remains of flowering plants that would not 
now prosper even in England. We find England and 
France clothed with a vegetation which we should not 
at present expect north of Morocco. We find, long 
afterwards, that the elephant and hippopotamus were 
as much at home on the plains or in the streams of this 

107 



io8 THE ICE AGE THAT MADE MAN 

part of Europe as they now are in Africa. Indeed, it 
is the opinion of many high authorities that the most 
important family of animals on the earth, the Primates 
(monkeys, apes, and man), developed within the Polar 
Circle, and descended south only as the earth pro- 
gressively cooled. 

All this I have described in the earlier manual. 
I want only to refresh the reader's memory in order 
to throw into strong relief the effect upon man of the 
next Ice Age. Cold, as such, is not a beneficent 
agency. Adverse circumstances may stimulate a few 
to rise above them, but for the majority they mean 
an absorption in the problems of the hour which 
leaves no time or inclination to think of progress. The 
earliest civilizations were not born on the fringe of 
the ice-sheet, but far south of its greatest extension, 
and in the most fertile and comfortable valleys which 
the region afforded. 

It is chiefly the supervening of the cold upon a 
warm climate which stimulates evolution. We must, 
of course, not understand that too narrowly. It may 
have been probably was in the later stages of the 
Permian Ice Age that the bird and mammal were 
evolved. The advance of the cold, the conversion of 
fruitful into bleak and inhospitable territory, would 
at first tend simply to press the animals backward 
into the regions which remained warm. These would 
in time be over-populated, and the intense struggle 
for life would drive some back into the temperate 



THE ICE AGE THAT MADE MAN 109 

fringe, where there would be less competitors. I have 
suggested that this was the way in which certain 
families of reptiles were gradually adapted to the 
cold, and became birds and mammals. But this 
comes, in the end, to the same thing. It was the 
supervening of an Ice Age upon a uniformly warm 
earth which caused the evolution. 

I am going now to suggest that, in the same way, 
the glaciation of a Europe which had previously been 
warm throws a remarkable light upon the making 
of man. It will be noticed that I speak only of 
"suggesting" this. It is by no means the settled 
teaching of science. The facts which I give as the 
basis of the suggestion are, of course, undisputed, but 
science is only now feeling its way towards a general 
conception of the early history of man, and there is 
still a great deal that is obscure and unsettled. The 
reader will judge if this connection of man's advance 
with the last great Ice Age does not greatly illumine 
the whole story. 

Of the Ice Age itself I gave so much evidence in 
the first chapter that it is hardly necessary to add 
more. Europe north of the Thames and Danube 
(and partly south of those rivers), and America north 
of a line drawn from St. Louis to New York, bear on 
their faces the marks of the Ice Age as plainly as 
northern France still shows the scars of the Great 
War. The numerous lakes generally dammed valleys 
or basins scooped out of the crust which lie in such 



1 10 THE ICE AGE THAT MADE MAN 

positions as the Swiss lakes do to-day; the boulders 
scattered over vast areas far from the rocks from which 
they came; the rounded and scratched rocks; the 
thousands of miles of ancient moraines or beds of 
glacial rubbish all these things have been familiar 
for decades, and meet the eye of the student of geology 
almost wherever he goes. I have myself seen them 
superficially, as a rule, in the course of travel over an 
area of hundreds of thousands of square miles, from 
Germany to Chicago. x 

Again, one must keep one's mind clear as to what 
is disputed and what is settled. There is now no 
geologist in the world who would not think it ludicrous 
to question the occurrence of the last Ice Age. One 
would as soon think of questioning the historical exist- 
ence of the Carthaginians. But when it was, how long 
it lasted, what caused it, and whether there were 
inter-glacial periods, are points on which opinions 
differ. 

In regard to the causes there is little difference of 
opinion, as we have seen previously. The general 
feeling now is that the Ice Age was due to the forma- 
tion of chains of mountains. Since, in point of fact, 
it occurred when the chief mountain ranges of to-day 
reached their height, there is not much room for differ- 



1 For America the United States Geological Survey has issued 
(1916) a beautiful volume on the evidences of glaciation. But 
every recent manual of geology devotes much space to the last Ice 
Age. 




eproduced by permission of George Philip & Son, Ltd. 

THE LAST ICE AGE. LARGEST EXTENT OF THE ICE-SHEET 
AND EXTENSION OF THE DRY LAND 



THE ICE AGE THAT MADE MAN 1 1 1 

ence of opinion. The constancy with which we find 
these two phenomena associated in the story of our 
planet, and the ease with which we can explain the 
connection, dispense us from further discussion. We 
saw that the great mountains of Europe, Asia, and 
America began to rise during the Chalk Period. We 
can trace that some of them continued to rise, at in- 
tervals, during the warm periods which followed the 
Chalk; and we can show that these elevations brought, 
locally, a drier and colder climate. It was one of these 
rises, in America, that caused the Colorado River to 
flow more steeply and cut its famous canyons. But 
the main rise was at the close of this last warm Era 
of the earth's chronicle. The Rockies and Andes, 
the Pyrenees and Alps and Carpathians, the Atlas and 
Himalaya ranges, then reached their height. The 
Ice Age followed ; and we need seek no other cause. 

There is a little more difference of opinion as to 
whether the Ice Age meant four or five glacial periods 
with warm intervals between them. As far as America 
is concerned, the leading geologists claim that they 
have proved five successive extensions of the ice from 
the mountains, with four comparatively warm periods 
between. A few maintain that there were six glacial 
extensions; a few others that there were only three. 
It is a technical question that does not greatly interest 
the general public. We need note only that the 
second (Kansan) spread of the ice is regarded by the 
American geologists as by far the greatest; but as man 



H2 THE ICE AGE THAT MADE MAN 

was not then in America we are not much concerned 
with it. 

The chief authorities on the glaciation of Switzer- 
land also claim five glacial and four inter-glacial 
periods, and they are generally followed. But there 
is, especially among recent geologists, more difference 
of opinion about Britain and northern Europe. Many 
geologists state categorically that there was only one 
glacial period in England. Others believe that man 
arrived here during an inter-glacial period. As far 
as the point concerns us, we will return to it later. 

Assuming that there were inter-glacial periods, the 
explanation would be on lines which we have previ- 
ously suggested. Take North America. We find 
the bones of whales and seals several hundred feet 
above the present sea level and far inland. Near 
Montreal such bones are found at a height of 520 feet. 
Clearly the land has risen a good deal since the Ice 
Age. This probably means that during the Ice Age 
the earth's crust was pressed down by the enormous 
weight of ice and snow which it bore in North America, 
and the sea encroached. The vast broken hollow 
which we call Hudson's Bay seems to be a perma- 
nent relic of the depression. The Baltic region and 
the flooded fiords of Norway appear to demand the 
same explanation. It is suggested that this depres- 
sion of the surface by a great mass of ice may have 
led to a milder climate, and that, as the ice then 
melted, the earth may have risen again. So some 



THE ICE AGE THAT MADE MAN 113 

would explain the five glacial and four inter-glacial 
periods. Eight million square miles of permanent 
ice and snow that was the greatest extension of the 
ice-sheet mean a most formidable load, when we 
recall that a column of ice only 200 feet deep and a 
yard square weighs half-a-million pounds. 

The differences of opinion are far more pronounced 
on the most interesting question of all: when the 
Ice Age began, and how long it lasted. The most 
favoured estimate in America is that the first glacia- 
tion began about 600,000 years ago, and that the last 
ended from 50,000 to 20,000 years ago. Professor 
Chamberlin, in a rather older estimate, makes the Ice 
Age last from 1,020,000 to 20,000 years ago. Pro- 
fessor Schuchert, one of the most recent writers, esti- 
mates the whole period at from 400,000 to 1,400,000 
years ago ; and he says that the latter figure is probably 
nearer the truth. The radiological estimate of the 
age of the earth would require an even larger figure 
than this. On the other hand, Scandinavian geolo- 
gists claim to have fixed the end of the Ice Age in their 
region at 30,000 years ago, and some who say that 
the place on which Stockholm is built to-day was 
under ice 9,000 years ago even at 7,000 years ago. 

In other words, the subject is so obscure, and the 
estimates are so conflicting, that we shall have to 
proceed with great care and reserve when we come to 
the question of man's contact with the Ice Age. Yet 
this is the most interesting of all questions in connec- 



1 14 THE ICE AGE THAT MADE MAN 

tion with the last Ice Age, and we shall see to what 
extent science can give us a satisfactory idea. 

Here any person who wishes to follow intelligently 
the references to discoveries of early man which now 
occur so frequently in the press will find it useful to 
remember just one or two geological terms. The 
story of the earth is, as I said, divided into Eras (see 
p. 63). The last, and shortest, of these is called the 
Cenozoic Era. 1 If we take the whole story, for con- 
venience, as a matter of a hundred million years this 
Era lasted about five million years. It represents 
the time between what we called the Cretaceous Revo- 
lution and that with which we are now concerned, the 
Pleistocene Revolution. The last section of this Era 
is known as the Pliocene Period, and the entire stretch 
of time since its close is called the Pleistocene Period. 
These are the two words which occur invariably when 
there is question of early human remains. The Plio- 
cene is the Period before the Ice Age began, or the last 
part of the Cenozoic Era. The Pleistocene is from 
the beginning of the Ice Age until the dawn of history. 

It is quite certain that man appeared long before 
the Ice Age, or in the first half of the Cenozoic Era. 
We have no remains whatever not even rough stone 
implements belonging to those early days, but it is 
none the less certain that man was on the earth. It 



1 At one time it was commonly called the Tertiary Era, as the 
whole of geological time was then divided into three main sections. 
The name still occurs, but it is now inappropriate. 



THE ICE AGE THAT MADE MAN 115 

is now beyond any question that man and the man- 
like apes came from a common stock, and, as we find 
remains of such apes in strata which belong to the 
middle of the Cenozoic Era (or before it), we know 
that our branch of the Primate family must have been 
in existence at the same time a time that we may 
conceive, on the most moderate estimates of geological 
chronology, as between two and three million years 
ago. No doubt the ancestor of our race that then 
existed was only semi-human; possibly not very 
different from the apes of the other branches of the 
family. Probably its home was South Central Asia, 
or the lost land of which the islands of the Malay 
Archipelago are fragments. All the evidence up to 
date seems to me to point to the latter. 

But, whatever the cradle of the race was, man 
wandered into Europe before the Ice Age began; and 
with this point alone we are concerned here. A year 
or two ago (1920) Mr. Reid Moir, one of the best 
experts in East Anglia, found flint implements of a 
fairly advanced type underneath the Boulder Clay 
near Ipswich. He and others stoutly maintain that 
the earliest implements on (or under) British soil 
belong to the Pliocene Period. There are the usual 
differences of opinion. Some would say perhaps 
this is now the general opinion that man was in 
Britain (which was then not yet cut off from Europe) 
before the Ice Age began; some would say that he 
reached Britain during an inter-glacial period. 



1 16 THE ICE AGE THAT MADE MAN 

The dispute must be mentioned in any account of 
man and the last Ice Age, but it does not affect the 
view which I am putting before the reader. On the 
one hand, it is practically certain that man entered 
Europe from the south-east, and it would take ages 
before the primitive, sluggish, ape-like wanderer 
reached the part which we now call England. If the 
man-like apes were in France at least a million years 
before the Ice Age, as they were, we need not hesitate 
to assume that man was somewhere in Europe before 
the end of that million years. On the other hand, 
it is perfectly certain and agreed that the race was 
spread over Europe before the great extension of 
the ice and snow which covered four million square 
miles, and this is precisely the glacial period which 
"made man." 

With these reserves, therefore, let us picture to 
ourselves what happened on the lines which most of 
the authorities follow. Strewn fairly thickly over 
parts of the eastern counties of England (though not 
confined to these) are certain very crudely chipped 
flint implements which are known as Eoliths. The 
workmanship is so slight that some still question if 
they are not merely flints that have been accidentally 
chipped or knocked together ; but they are now gener- 
ally admitted. They are found also on the other 
side of the North Sea, and, as the North Sea was then 
dry land, these very primitive humans probably found 
it a congenial country, with plenty of food. In the 



THE ICE AGE THAT MADE MAN 117 

same region East Anglia we find also the next 
type of flint implement (rostro-carinate) . Taken 
together, the two sets of implements seem to indicate 
a very long sojourn of primitive man in eastern Europe 
long before the Ice Age. 

Whether the bones of the Piltdown man (or Eoan- 
thropus) are remains of this race is a very thorny 
question. One badly shattered skull and bits of a 
second skull were found at Piltdown, and the best 
authorities estimate that the brain was quite large. 
On the other hand, the lower jaw was so brutal that 
some at first regarded it as belonging, not to the man, 
but to a chimpanzee. A somewhat similar, though 
slightly higher and later, jaw was found at Heidelberg 
in Germany unfortunately without any trace of the 
upper part of the skull. All agree that these are the 
earliest remains of man in Europe, but the claim that 
the brain was large is very puzzling. Let us leave it 
open. It is difficult to believe that such a jaw was 
associated with a "modern" type of brain; and it is 
significant that only the lowest kind of stone culture is 
found in strata of that age (at least 400,000 years ago) . 
I do not think that the last word of science has yet 
been said on the subject of Piltdown man. 

We reach firm ground, knowledge in which all the 
scientific men of Europe are agreed, when we glance 
at an early European race which is known as the 
Neanderthal race, or we may roughly say man of 
the Old Stone Age. Of this race we have about thirty 



1 18 THE ICE AGE THAT MADE MAN 

skulls, whole or partial, and several skeletons. They 
are all consistent, and the type is well known, as I 
have elsewhere described it. This was man at the 
beginning of the Ice Age: more than a million years 
old, yet lower in mental endowment and culture 
than the Australian black is to-day. This was the 
race that passed through the ordeal of the Ice 
Age. 

I have dealt somewhat fully with this period in the 
first chapter of my A B C of Evolution, and here I will 
be content to make certain important points clearer. 
The first is the question of climate. It may seem to 
the inexpert more or less of a conjecture when we say 
that the primitive European lived at first in a warm 
climate, with abundant food, and passed into the 
stress and scarcity of an Ice Age. But the evidence 
is positive. Both the animal and plant remains tell 
us the climate of a region at any particular time. We 
saw that before man came into Europe the climate was 
so warm that palms grew in the latitude of London 
and Paris, monkeys swung from tree to tree, and the 
elephant and hippopotamus found the temperature 
suitable. We then find, as we pass to higher levels, 
that the palms and the monkeys retire southward, 
but the earlier traces of man are contemporary with 
the elephant, rhinoceros, and hippopotamus. Step 
by step we can follow this early European race, by 
means of the bones of its animal contemporaries, into 
a colder and drier climate, until at last man shivers 



THE ICE AGE THAT MADE MAN 1 19 

in caverns amidst a region of ice and snow, and the 
woolly elephant and reindeer replace the older types 
of animals. 

Again we must call to mind the physical revolution 
which underlay the human story. Man had entered 
Europe when it was generally low-lying and warm. 
Our mountain chains had, as we saw, been arrested 
in their development, and had largely been worn down 
again. Europe was, in fact, the best continent for 
man to spread in. The European race was not 
" called " to a great destiny by some mystic vital force, 
nor was it endowed with some remarkable germ- 
properties which other races had not. These mys- 
ticisms explain nothing they are mere verbiage 
and are superfluous. 

What was unique about Europe was its physical 
history. America was too far away; the only land- 
bridge to it (Alaska) was in a remote and bleak region. 
Asia, we can see, was becoming very mountainous and 
inhospitable. Africa was forbiddingly hot and un- 
healthy, and the narrow valley of the Nile through 
which we might imagine primitive man approaching it 
the one gap through its northern barrier of desert 
did not yet exist in those days. The black had prob- 
ably entered Africa, and become black, from land on 
the north-eastern coast which exists no longer. Eu- 
rope was, on the whole, the best continent; and man 
early spread over Germany, Italy, France, Spain, 
Belgium, and England. Then Europe began to rise, 



120 THE ICE AGE THAT MADE MAN 

as we saw, and to prepare for its children the drastic 
ordeal of an Ice Age. 

The change is well expressed in a distinction which 
used to be made in the science of prehistoric man. 
Earlier man was called "river drift man"; later "cave 
man." A dozen different stages, with names that 
would only bewilder the reader, are distinguished to- 
day, but the old distinction expresses a fact of the 
broadest and greatest importance. Earlier man of the 
Old Stone Age, who left his implements in the river 
gravels, was an open-air man; a naked, homeless, 
speechless, primitive type, not particular about his 
food and not needing to exert himself to find it. Man 
of the later Old Stone Age, who lived in caverns, was 
a higher and far more progressive being: a maker of 
clothes and fire, a hunter, accustomed to decorate his 
weapons. Step by step he advances as the great 
ice sheet slowly spreads over Europe and drives him 
into his rock shelters and caverns. 

And here is the second point of great importance. 
Did the oncoming of the Ice Age convert man into a 
social animal, and precisely on this account put him 
in the way of more rapid advance? I have in the 
earlier work summarized the evidence that man was not 
a social animal before the Ice Age, and that he began 
to lead a social life during it Recent research has 
made no difference in this evidence, and I will not 
repeat it. Everything we know tends to show that 
social life began round the fires which man learned to 



THE ICE AGE THAT MADE MAN 121 

make when the cold set in, and under the rock shelters 
where some protection was afforded from the biting 
winds. That was the real making of man. There is 
no reason whatever to suppose that the pace of human 
progress would have increased as it did if there had 
been no Ice Age. 

To what I have said elsewhere about the stimulation 
given by social life let me add here that the Ice Age 
converted man into a hunter. On the analogy of 
very lowly savages lower than the Australian, as 
many are we can imagine man before the Ice Age. 
He literally " picked up" his living lizards, insects, 
dead animals, eggs, shell-fish, etc. His only weapon 
for ages was a stone that he held in his hand, without 
a handle. At the most he might throw it at an 
animal. To what extent could such a man be a 
hunter? His bones show that he was a heavy, slow- 
moving creature, and his weapons (of which we have 
millions of specimens) reached only as far as his arm 
reached. What animal could he hunt? The wolf, 
the fox, the deer, the horse, the wild ox, or dog ? Every 
animal could outpace him. Even if we supposed 
that he hunted in groups, it would make little differ- 
ence. An elephant or a rhinoceros would hardly 
remain passive while a score of Palaeolithic savages 
tried to gash its flanks with hand-carried stones. 

Arrow-heads and spear-heads begin with the Ice 
Age. Man had become a hunter. The drawings 
which he has left us show that he hunted the rein- 



122 THE ICE AGE THAT MADE MAN 

deer, the mammoth, the wild ox, and the wild horse. 
In some places great piles of horse bones accumu- 
lated. They are clearly hunting camps. Neanderthal 
man had become both social and a hunter. Food no 
longer lay about on every hand. Even in summer 
what was left of Europe, apart from the northern ice 
sheet which reached the valley of the Thames (with 
glaciers even on the South Downs) and the great 
Swiss ice sheet, was bleak enough. In winter it must 
have been frozen over. Vegetation was scanty. Fish 
and shell-fish were unobtainable half the year. It was 
necessary to store food against hungry days. "Big 
game" hunting was imposed upon man; and we can 
broadly realize the stimulation it would give to his 
intelligence. This and social life explain the rapid 
advance of man in the cave-period; and it was the 
Ice Age which necessitated both. 

The next step was agriculture. A hunting com- 
munity must wander a good deal. It exhausts a 
region, and must move to another. When man 
learned, or noticed, the meaning of the seed when 
he could sow food at his own door and garner it for 
the winter he could have settled villages, the germs 
of towns and of civilization. We should not expect 
this discovery in glacial Europe. But the larger part 
of the inhabitants had been driven out of Europe, and 
they were pinned in a relatively small region between 
the African desert and the frozen North: some in 
Morocco and Algeria, most of them at the eastern end 



THE ICE AGE THAT MADE MAN 123 

of the Mediterranean (which was then dry land). 
This concentration led to social life and (as the condi- 
tions of life were here less exacting) to even greater 
progress. The primitive barbarian of Europe be- 
came an artist. The primitive migrant from Europe 
became, in a more genial world, a farmer. 

The end of the Ice Age would, as we saw, be at a 
different date in different regions. The south would 
first enjoy the new conditions and be stimulated by 
them. But even in its end the Ice Age shaped the 
course of human history. The swollen waters of the 
Nile cut the valley of Egypt through the desert, and 
gave it its covering of wonderful soil. The swollen 
rivers from nearer Asia filled up the arm of the sea 
which is now Mesopotamia. For the primitive farmer 
here were two rich territories. About the same time 
the basin of the Mediterranean was flooded. As the 
ice of Europe melted, the level of the Atlantic rose 
higher. Hundreds of thousands of millions of tons 
of ice and snow were transferred to the ocean. Prob- 
ably the ocean then burst through the gap at Gibraltar. 
At all events, we know, on positive grounds, that a 
large part of the land between Italy, Greece, Asia 
Minor, Palestine, and Africa was then flooded. 

I refer to my previous book for the working out of 
these consequences. Briefly, this central idea connects 
together all the threads of the evolution of civilization 
in different regions. It explains why south-eastern 
Europe was the great stage of civilization, why 



124 THE ICE AGE THAT MADE MAN 

there was a "Mediterranean race," why the white 
race became the chief representative and developer 
of civilization. The discoveries of the last twenty 
years have illumined the whole story. However per- 
plexing may be the earlier part of man's history, the 
later part, the advance to civilization, can no longer 
be regarded as a mystery. 



CHAPTER VIII 

THE NEW ERA OF EVOLUTION 

WE have now completed, in outline, the story of the 
earth's revolutions, and it is plain that we are guilty 
of no exaggeration in giving that name to the Ice Ages. 
Geological time was divided into three Eras long 
before the earlier Ice Ages were suspected, or the 
last Ice Ages fully known. There were great 
breaks of some kind in the geological chronicle. The 
continuity of nature's processes was somehow broken. 
Now we understand these natural divisions. Between 
each of the older geological Eras was a revolution, 
physical and biological; and the obscure primordial 
Era, or Eras, that we have added to the older ones 
also witnessed an Ice Age. 

That these were physical revolutions is now clear; 
and I trust I have shown, in the small space at my 
disposal, that they were also biological revolutions. 
What effect upon life the first two Ice Ages had we do 
not know. But the chronicle is very complete as re- 
gards the third, fourth, and fifth revolutions. It is 
enough to recall that the third brought upon the scene 
the mammal and the bird; the fourth made the earth 

125 



126 THE NEW ERA OF EVOLUTION 

statable for the mammals and birds, and secured 
their triumph; the fifth, in stimulating the evolution 
of man towards civilization, rendered the greatest 
service of all. The story of life becomes intelligible. 
Great as are the mysteries that still lurk within the 
organism, it is merely foolish to confine one's atten- 
tion to these obscurities and say that we face the 
general problem of the evolution of life with no more 
knowledge than men had fifty years ago. One half 
the problem has been wonderfully illumined. 

I need not repeat that this triumph has entirely 
confirmed and expanded the main principle which 
Darwin put before the world fifty years ago. But it 
will be useful to conclude with some consideration of 
the relation of these matters to social problems and 
methods. 

And in the first place it is necessary to make en- 
tirely clear that all this study of evolution in the past 
has no direct lessons at all for present and future 
evolution. One looks back with a smile on much of 
the sociological literature of the late nineteenth cen- 
tury, and even of the early decades of the twentieth. 
There was a distinguished man of science in Austria, 
Professor Virchow, who rejoiced the reactionaries 
all his life by refusing to countenance Darwinism (in 
which he privately believed) ; and his reason was that 
Darwinian ideas led to Socialism. But there were 
even more numerous writers who assailed Socialism 
on the express ground that it was inconsistent with 



THE NEW ERA OF EVOLUTION 127 

Darwinism. It was one of those wordy warfares which 
are so frequent in social literature, where argument 
and rhetoric are apt to take the place of facts. Both 
sides were wrong. Darwinism is a description of the 
past; social idealism of the present and the future. 
The laws and processes of the past are not the laws 
and processes of the future. 

Broadly speaking, what the whole of this slow ad- 
vance of life during tens or hundreds of millions of 
years this long struggle for food and (above a cer- 
tain level) for mates, this slow oscillation of the crust 
of the earth which changes and destroys the life- 
conditions of myriads, this periodic invasion of the 
planet by intense cold what it all means is that life 
had to be goaded onward. The living population of the 
earth was like a flock of sheep that had to be turned 
here and there : like a pack of dogs that had to feel the 
lash and the rein. We may say what we like about 
heredity, but this is the quintessence of the evolution 
of life up to now. Fishes may have had must have 
had the most wonderful germinal potentialities, but 
they did not leave the water until physical changes 
in the earth's surface drove them to do so. It was 
the same with all the other great steps in evolution. 
The lash was laid on the back of the animal world. 
The spur of adversity sank into it. 

But social idealism makes or imagines laws for a 
totally different material. It assumes that it is 
legislating for intelligent men and women. It sup- 



128 THE NEW ERA OF EVOLUTION 

poses that it is dealing with living beings who can see 
the goal, and can, if it is attractive enough, make their 
way to it without spur or lash. That never happened 
before in the history of life on the earth. All the 
earlier animal populations were blind in this respect. 
They went where they were driven. Man alone can 
frame an ideal which will draw and direct him. If 
you care to put it so, he is driven by the luminous 
thing, the vision, in his own mind; but it makes all 
the difference in the world, for the lash of outward 
circumstances is no longer needed. 

Hence the appearance of man ought to start a new 
era in evolution. If I may use a rather bold meta- 
phor, it should be like the opening of an era of auto- 
matism or automobilism. The old type of carriage 
was an inert thing; it went where it was dragged. 
That was the pre-human animal. The motor car 
does not wait to be dragged. Man is now supposed 
to have the motive power and the chart of the way in 
his own mind. He is "the master of things," not 
the slave of things. The old laws of progress do 
not apply to him. 

An animal was made strong or cunning in the old 
era by fighting. Unless it fought, through a long 
series of generations, it lost its potentialities and 
might even lose its actual qualities, as birds on islands 
where there are no enemies lose the use of their wings 
or as fish in dark caverns lose the use of their eyes. 
Man does not need that external stimulus. It is 



THE NEW ERA OF EVOLUTION 129 

nonsense to say that he needs fighting to develop his 
strength, for athletic exercises devised by himself will 
do it just as well and he will not leave his well- 
developed muscles in some stinking grave on the 
athletic field. It is nonsense to say that he needs 
competition to develop his intelligence; for he could 
develop it in isolation. 

That is to say, in theory; and there you have the 
key to the whole confusion. Man is changing, but he 
has not yet changed. Some men are a new type of 
creature, looking before and after. A great many are 
not. Few have fully developed the new faculty. We 
live in the phase of transition from evolution by the 
lash to deliberate self-evolution; and every age of 
transition is confused and painful. It is said that 
there are 1,700 million human beings on the earth. 
Two-thirds, or more, of them have no idea whatever 
of a new power or a new era. They have lived under 
the lash of pastors and masters so long that the new 
idea of self-government, if it reaches them at all, 
dazes them. Even in civilization the majority hardly 
know what it means; and the majority of those who 
know, and try to realize it, are checked by the diffi- 
culty that they must act collectively, and in order to 
do so they must think collectively, which will take a 
long time. 

And if the logically-minded reader asks whether 
this state of humanity is to last until there is a new 
Ice Age, the answer need not be too modest. I have 



130 THE NEW ERA OF EVOLUTION 

shown that there is a very curious and positive reason 
to suspect that the interval of time between Ice Ages 
is shortened by about fifty per cent, every time. Why 
this is so no one has yet attempted to say ; but the 
facts are so remarkable that it looks like a "law." 
Now, supposing that the interval between the fourth 
and fifth Ice Ages was about five million years a low 
estimate and that the fifth is over, the sixth might 
be expected in two or three million years from to-day. 
If anybody thinks that the human race will have to 
wait so long as that for wisdom, he would, one would 
imagine, like Huxley, "hail the coming of some 
friendly comet to sweep us to destruction." 

On the contrary, the new era of evolution will by 
that time be so far advanced that physicial revolu- 
tions will cease to control the world of life. We say 
that the last Ice Age is over. This may not be quite 
accurate. It may be that the earth will grow so much 
warmer that the Swiss ice, and much of the Polar 
ice, may disappear We are in the penumbra of the 
Ice Age, even if we say that it is over. Most prob- 
ably in the course of some tens of thousands of years 
Europe will become warmer. It is wearing down. 
Then will come, at a time which seems to us colossally 
remote, yet is small on the geological scale, the sixth 
Ice Age. If the interval goes on decreasing by fifty 
per cent., the Ice Ages will at last run together, and 
the entire earth be glaciated. If, as seems probable, 
man is still on this globe when that occurs, it will make 



THE NEW ERA OF EVOLUTION 131 

no difference to him. His command over matter will 
have reached such a pitch that he will be able to live 
without cornfields or cows. 

Much of this, no doubt, sounds like romance. But 
it is very sober romance. Take the last four Ice 
Ages, and the intervals between them as suggested on 
p. 63. If we take the story of the earth as a hundred 
million years, it is plain that we are justified in ex- 
pecting the sixth Ice Age in from two to two and 
a-half million years; and we should fairly expect 
permanent glaciation in five or six million years. On 
that scale of time (a hundred million years for the 
earth's past) mathematicians say that they have very 
good reason to expect at least ten million further years 
of life on the earth. If you multiply the figures by 
seventeen, as the radiologists demand, the permanent 
glaciation would not be expected for eighty million 
years; but on the other hand, man's lease of life is 
extended to something over two hundred million 
years ! If there is any romance in this, it is not my 
feeble fancy that can claim the merit. It is a direct 
inference from the statements of our most brilliant 
geologists and physicists. 

And this to return to our social theme is pre- 
cisely the spirit which the world wants : a basis of most 
carefully ascertained fact, and then an audacity like 
that of our great intellectual constructors. The revo- 
lution which will inaugurate the new era of evolution 
will not be physical. If there are any laws of life at 



132 THE NEW ERA OF EVOLUTION 

all, it will be intellectual and emotional. The heavy 
conservatism of the race will be shaken by as mighty 
an upheaval as the physical uplift which shattered the 
conservatism of the salamanders of the Coal Forest or 
the reptiles of Mesozoic Europe and America. The 
evolution of mind will have its revolutions its rapid 
periods as had the evolution of matter and of life. 

It is clear that we have entered upon such a period. 
Speaking quite soberly, attending to the historical 
facts alone, there never was in the world before such 
intellectual movement as there has been during the 
last half or three-quarters of a century. One has only 
to recall the religious and political changes which have 
affected the minds of hundreds of millions of people. 
We have to pay the price of this movement. In all 
earlier ages movement was from one definite political 
or religious type to another: from monarchy to re- 
publicanism, from one religion to another known 
religion. The alternative existed or was clearly con- 
ceived. The difficulty of our age is that we are com- 
pelled to look beyond all the familiar types to create 
new ones; and for a time the situation is bound to be 
intellectually chaotic. Moreover, modern civiliza- 
tion has economic problems of a magnitude that was 
never dreamed of in the world before. So we neces- 
sarily have an age of controversy, of intellectual differ- 
ences. The danger is that the mass of people may be 
tempted, from weariness, to shirk the task. The 
supreme requirement is that we shall keep our mental 



THE NEW ERA OF EVOLUTION 133 

life at the highest pitch of efficiency which the hard 
conditions of life permit. Our "national education" 
is largely a sham. We must do what we can to help 
each other; and even the most drastic intellectual 
challenge is a help, provided we can keep our tempers, 
maintain a high level of character, avoid conceit in 
our own opinions, and appreciate the causes of more 
conservative opinions. 

This is no place to indicate what the author thinks 
to be the goal speculative, political, economic, moral, 
or social towards which we should agree to tend. 
I am dealing with general laws and dispositions. I am 
showing how the factors or stimuli of progress are now 
internal, not external. They are the mind and will of 
man, not Ice Ages or struggles for life. 

Yet this truth must not be taken too narrowly. It 
does not in the least mean that material conditions 
lose their importance. As we have seen, one of the 
most acute controversies in connection with evolution 
is as to the respective parts of heredity and environ- 
ment of "nature" and "nurture," as is often said; 
and there has been a strong tendency in the last two 
decades to depreciate, or even deny, the importance 
of environment. As far as the main theme of this 
book is concerned, my position will be clear. Darwin 
was right in admitting both factors, and he was 
equally right in thinking that for the present the study 
of the action of the environment is far more profitable 
than the study of heredity. In spite of the able and 



134 THE NEW ERA OF EVOLUTION 

devoted work that has been done, the fundamental 
mystery of heredity remains as obscure as ever. 
We simply have not the least idea how it is that a 
microscopic germ can build up a human body; but we 
have a very vast and profound and interesting know- 
ledge of the selective machinery of the environment. 
Hence, as far as past evolution is concerned, 
environment is as important as ever. And when we 
say that the factors of progress now ought to be in- 
ternal, we have not the slightest intention of lessening 
the importance of environment. All that is meant is 
that a man endowed with reason, will, and emotions 
ought not to wait for the stimulus of adverse circum- 
stances, as life has done hitherto. The revolutions 
of the past, which were very progressive but deadly 
periods, inaugurated " golden ages" which were very 
stagnant and unprogressive. Man's mental power 
makes him independent of both. He needs, or should 
need, no stimulation of adversity to make him advance. 
He runs no risk, or should run no risk, from a golden 
age. His mind can provide the stimulating elements, 
without the cruelty, of the one ; and it can add stimu- 
lating elements, without losing the comfort, of the 
other. Evolution is giving birth to wisdom. It 
is the function of wisdom to create a new evolution. 

THE END 



A Selection from the 
Catalogue of 

G. P. PUTNAM'S SONS 



Complete Catalogues sent 
on application 



The 

A B C of Evolution 



Joseph McCabe 



A book that tells the meaning of 
Evolution, and the actual story of 
the evolution of things, in very 
simple and attractive language. 
Packed with scientific knowledge, 
but quite free from difficult 
scientific terms. Tells you about 
everything, from Einstein to the 
Brontosaur, from the stars to the 
laws of social development, yet a 
child may read it with pleasure. 



G. P. Putnam's Sons 

New York London 



The Evolution of 
Civilization 

By 

Joseph McCabe 

Author of " A. B. C. of Evolution," etc. 

The author has attempted an ambitious task 
in this sketch of civilization from the earliest 
times, and he has achieved it brilliantly. 

Here, in this small compass, is the story of 
civilization from brute man to our own stage of 
culture. Here is the romance of time so lucidly 
told that it will probably induce the reader to a 
more detailed study of the various tendencies that 
have raised man to what he now is. 

"There is no writer today," says the reviewer 
in John 0' London's Weekly, " who can explain 
the discoveries of modern science in simpler and 
more popular language, nor is there a man who 
has a more thorough grasp of his subject. This 
is a very able book." 

G. P. Putnam's Sons 

New York London 



A Candid History of 
the Jesuits 

By / 

Joseph McCabe 

Author of " Twelve Years in a Monastery," 
"Modern Rationalism" 



It is curious that no writer addressing English- 
speaking readers, has ever attempted a system- 
atic history of the Jesuits. Probably no religious 
body ever had so romantic a history, or inspired 
such deadly hatred. On the other hand, histories 
of the famous society are almost always too preju- 
diced, either for or against, to be reliable. Mr. 
McCabe has attempted in this book to give the 
facts impartially, and to enable the inquirer to 
form an intelligent idea of the history and charac- 
ter of the Jesuits from their foundation to the 
present day. Every phase of their remarkable 
story including the activity of political Jesuits 
and their singular behavior on the foreign mis- 
sions is carefully studied, and the record of 
the Jesuits in England is very fully examined. 

G. P. Putnam's Sons 

New York London 



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