THE ICE AGE
For some reason or reasons concerning which there has been a great
deal of speculation but not a large amount of agreement, the closing
stages of the last geologic era which precedes our own and which
links the great past to the present, were distinguished by great cold
and by widespread fields of ice. Ice-sheets spread over six or eight
million square miles of the earth's surface where not long before
mild climates had prevailed. Were it not for this great Ice Age and
for its far-reaching effects on the conditions under which Man has
developed, this period, which is sometimes called the Pleistocene,
(from Greek words meaning the "most recent"), would be more properly
joined to the era which we have just been discussing, the two
periods constituting a single period of great land elevation and of
ocean-shrinking. This period, however, is now thought to be much more
important than it was formerly, and perhaps longer in duration.
More than half the ice-covered land lay in North America and more
than half the rest in Europe. The glaciation, therefore, was probably
confined to certain parts of the world and did not stretch all over
the planet. But the whole world felt its effects; even in tropical
regions ice and glaciers occurred on mountains where they did not
exist before and do not exist now, and on mountains which now have
glaciers the ice descended to levels 5000 feet below the point where
it now stops. The southern hemisphere was affected as well as the
northern, but to a much less degree. In Patagonia and New Zealand
glaciers crept down from the mountains and spread out on the plains.
Glaciers formed on the mountainous tracts of Tasmania and Australia
where none exist now. Most of the higher mountains of the southern
hemisphere bore glaciers. The Antarctic regions were presumably
buried beneath ice and snow as they are at present, but of that we
are not certain.
In Asia ice-fields far greater than those existing to-day affected
the higher mountains, and from the Lebanon to the Caucasus and from
the Himalayas to Siberia and China traces of glaciers are found where
they are not to be seen now. Yet on the plateaux and lowlands of
Asia ice-sheets were far less extensive than in Europe and in North
America.
In Europe there were large glaciers in the southern mountains and
extensive ice-sheets on the southern plains. Radiating from the
Scandinavian highlands a succession of great ice-sheets crept forth
on the lowlands of Russia, Germany, Denmark, Holland, and Belgium,
and crossing the shallow basin of the North Sea touched the shores
of Great Britain, where they were met by ice radiating from the
mountains of these isles.
From the Alps gigantic glaciers descended to the lowlands in all
directions. Then the Rhine glacier moved out far beyond the mountains
and joined with the glaciers of Savoy and Dauphiny on the plains of
France, while from the Southern Alps glaciers invaded the fertile
plains of Italy.
Glaciers of similar size and extent descended into the valleys of
the Rhine and Danube. The Pyrenees, some of the higher mountains of
the Spanish plateau, the higher mountains of France, the Apennines,
the Carpathians, the Balkans, the Urals, all had their ice-sheets.
Iceland and the Faroe Islands were buried under ice, and even Corsica
had snowfields and glaciers, some of which were not small.
Nearly one half of North America was buried in ice. Strangely enough,
it was not the whole northern half, but the north-eastern half that
was specially ice-invaded, and, more strangely still, not so much
the mountainous portions, though these were affected, as the plains.
Alaska was largely free from ice except on or about the mountains:
and there was less ice on the western plains than in the valley of
the Mississippi. Much the greater part of the four million square
miles of ice-field lay on the plains of Canada and in the upper
Mississippi valley. The Missouri and Ohio rivers like two great arms
embraced the borders of the ice-fields to which they owe their origin.
We do not propose to examine the several theories which have been
proposed to account for this extraordinary cold, for none is
completely acceptable or accepted, but we may just mention them. Dr.
Croll a century ago suggested that the cold may have been due to
the alterations in the shape of the earth's orbit, alterations which
astronomers tell us take place regularly, though very slowly and at
intervals of millions of years. If so, this glacial period was only
the last of many glacial periods; the traces of the earlier ones
having, however, been for the most part obliterated and destroyed.
Sir Charles Lyell has urged that geographical changes (elevations
and subsidences) would of themselves be sufficient to bring about
a glacial period, which (he says) would be the result of a great
continent being formed round the North Pole while oceanic conditions
prevailed at the Equator. Another theory is that the heat given out
by the sun is not always equal, being sometimes more (when even polar
countries enjoy a warm climate) and sometimes less (when only the
equatorial regions are habitable). The objection to this theory is,
of course, that we have no proof that our sun is of greatly variable
heat. Whatever may have been the cause of the glacial period, we know
as a proved fact that a long time ago (as measured by years, although
the event itself is among the latest of the many changes recorded
in the geological history of the earth) the climate of the British
Isles was so intensely cold that the greater part of this country was
covered with ice and snow, and we know also that this intense cold
was sufficient to change in many respects the habits and appearance
of the animals and vegetation of the earth. How much this was the
case can be gathered from the fact that in the period which preceded
it animals which now live in the tropics roamed in the Arctic circle,
and figs and magnolias grew in Greenland.
The last word we shall have to say on the climatic conditions of
this period is that the Ice Age had its sub-periods and divisions
like all other epochs and in them the ice sometimes retreated, and
consequently in parts of the earth where there had been snow and ice,
and where there were to be ice and snow again, the wintry conditions
retreated (for centuries, perhaps, at a time), and the valleys and
plains basked during these intervals in sun and rain and warmth.
These epochs are called "inter-glacial epochs."
The life of the regions not much affected by the rigours of snow and
ice is gradually being ascertained by geologists now. One of its most
marked features was the retreat of the northern and Asiatic animals
before the advancing ice towards the warmer tropics and Equator;
these animals journeyed back northward again whenever the retreating
ice would let them. The great _Proboscideans_, the Mastodon and the
Mammoth were members of this group, and so were the bear, the bison,
the musk ox. With these mingled towards the south several types
(which were gradually becoming extinct in North America) such as the
horse, tapir, llama, and the sabre-tooth cat. A second prominent
feature was a southern group in the western hemisphere, consisting of
gigantic sloths, armadillos, and water-hogs; and now for the first
time the interest of animal life shifts to South America.
"There are many instances," says Sir Edward Ray Lankester in his
book on _Extinct Animals_, "in which small living animals were
represented in the past by gigantic forms very close in structure
to the little living beasts, but of much greater size. Hence it is
concluded that these particular living animals are the reduced and
dwindled representatives of a race of primeval monsters. There is
some truth in this, as may be seen from the history of the living
sloths and armadillos of South America, as compared with the extinct
gigantic sloths and armadillos dug up in that country. But it is a
great mistake to conclude from this that it is a law of nature that
recent animals are all small and insignificant as compared with
their representatives in the past. That is simply not true. Recent
horses are bigger than extinct ones; recent elephants are much bigger
than their earlier elephantine ancestors. There never has been
any creature of any kind--mammal, reptile, bird, or fish--in any
geological period we know of, so big as some of the existing whales,
the Sperm Whale, the great Rorqual, and the whalebone whales.
"It is true that there were enormous reptiles in the past, far larger
than any living crocodiles, standing fourteen feet at the loins, and
measuring eighty feet from the tip of the snout to the end of the
tail; but their bodies did not weigh much more than a big African
elephant, and were small compared with whales. So let us be under no
illusions as to extinct monsters, and proceed to look at those of
South America with simple courage and confidence in our own day."
The peculiar productions of South America in the way of animals
appear to be the members of the group of mammals called _Edentata_
found nowhere else. When, however, South America, which once was an
island, joined on to North America, numbers of animals, mastodons,
horses, tigers, and tapirs, emigrated from north to south, and
perhaps proved too much for the aboriginal or native beasts. At any
rate, all the big South American mammals died out, and now there
are left only the small tree sloths, the small armadillos, and the
strange-looking ant-eaters. But in quite late geological deposits
of South America we find the bones of gigantic armadillos and of
gigantic ground sloths, which lasted on till the time when man
appeared on the scene.
The _Glyptodon_, of which there were several different kinds, was an
enormous armadillo as big as an ox. Like their small, puny, modern
descendants, they carried on their backs a hard case of bones,
something like the shell of a tortoise. The modern armadillo's shell,
however, is jointed so that the little animal can roll itself up into
a ball, and in this direction, therefore, the armadillo, though it
has decreased so much in size, has advanced in adaptability.
The _Megatherium_ was nearly as big as an elephant, and its skeleton,
though so much larger, is very similar to those of the small sloths
of present-day South America. Its teeth also are very much like
theirs. But whereas the living sloths climb trees, as they have
learnt to do, the _Megatherium's_ method was more primitive though
quite as effective. It stood on the ground and pulled the trees down
in order to eat the young branches. The _Mylodon_, which lived at
the same time, was not so big, and its habits were similar. It had
a number of little bony pieces scattered in its skin in the region
of the back, like the pieces forming the bony case of the ancient
armadillos; but the pieces in this case were not closely fitted
together.
It was supposed that the _Mylodon_, like all the peculiar gigantic
animals of South America, had become extinct as long ago as the
Mammoth (of which we shall say more presently) or of the woolly
rhinoceros which used to haunt Fleet Street. All these extinct South
American animals were distinguished by peculiarly shaped teeth, and
had no teeth at all in front. They are called, therefore, _Edentata_,
and their representatives to-day are much smaller.
But some years ago Dr. Nordenskjold, a Scandinavian traveller, while
exploring in Patagonia, found a vast cavern called the _Ultima
Speranza_ cave, on the western coast. From this cavern the settlers
who lived close by had removed an enormous piece of skin covered with
greenish-brown hair, and studded on its inner side with little knobs
of bone. The skin was dry but sound. When it was placed in water it
gave out a smell which, though unpleasant, was very interesting, for
it showed that the animal which had worn it could not have been dead
thousands or even many hundreds of years. It was, in fact, evidently
a piece of the skin of a _Mylodon_, which had survived in this region
until modern times.
Further explorations were made in the cavern by Dr. Moreno, of La
Plata, and other naturalists, and an immense quantity of bones was
obtained, and more portions of the skin of _Mylodon_ with the hair
on. The cavern had been inhabited probably several centuries ago by
Indians, for human bones and weapons were obtained.
The remains of as many as twenty _Mylodons_ have been obtained from
the cavern, and many of the bones are cut or broken in a way which
leads us to suspect that the human inhabitants of the cave cut up the
dead _Mylodons_ for food, and split their bones to obtain the marrow!
Some of the _Mylodon_ bones, skulls, jaw-bones, leg-bones, etc., are
smeared with blood and have pieces of cartilage and tendon attached.
There are other evidences which go to show that the Indians may have
kept the _Mylodons_ alive in the cave and fed them with hay brought
from the outside. Anybody who would care to see the last of the great
extinct animals can inspect some of these remains at the museum in
Cromwell Road, London.
Besides the relics of the _Mylodon_ and of Man the cavern has yielded
bones and teeth, and many horny hoofs belonging to a kind of extinct
horses; and this constitutes one of the puzzling things about this
cave treasure. The cave is in a part of the country very difficult
to reach, and though Sir Thomas Holdich and Mr. Hesketh Prichard
made efforts to reach it again and explore it systematically and
scientifically, there is a great deal about it that seems likely to
remain unexplained.
The bones that were found are not buried in lime or any preserving
stone; but lie in sand where one would expect them to have perished
long ago if they had been of any great age. Yet side by side with
them are the bones of a long-extinct horse; and there is no tradition
among the Indians to-day of any huge beast corresponding to the
_Mylodon_. Sir E. Ray Lankester has pointed out that the whole of
South America has been submerged and has risen (and is rising still)
for many centuries. Possibly the rocks and high lands where the
_Mylodon_ cavern occurs formed an island during the submergence,
where a number of early animals took refuge and survived until the
re-elevation of the land--and so lived on in the present condition of
the land surface until fifty or a hundred years ago. The great land
tortoises (like the Galapagan[17] tortoise) have similarly survived
on a few equatorial islands. Possibly, though it does not seem very
likely, the _Mylodon_ is still living in similar caverns in this
region, as yet unvisited by man.
[Footnote 17: Of the Galapagos Islands.]
In Australia, the land of the marsupials or mammals with pouches,
the bones of many gigantic creatures belonging to that tribe of
animal have been found. Giant kangaroos, twice as tall as the biggest
living kangaroo, wombats and voles as big as a rhinoceros, have been
discovered. One of these is the _Diprotodon_, which Sir Richard Owen
reconstructed much in the same way that he reconstructed the _Moa_,
and of which Dr. Stirling has since found complete specimens in a
morass in South Australia.
[Illustration: Diprotodon
Equal in size to a large rhinoceros. (Remains found in Australia.)]
Last of all of the great extinct mammals which we shall mention
is the Mammoth, which has a peculiar interest because, like the
_Mylodon_, it certainly survived until man was on the earth, as there
are many more evidences to prove.
In one of the caves of France inhabited by prehistoric men and
thickly strewn with the chipped flints which they used as tools and
weapons, as well as with the bones of extinct animals which they
ate, a piece of Mammoth's tusk has been found on which is rudely but
cleverly carved, evidently by the men who lived there, the picture of
a Mammoth. (There are besides, antlers on which a reindeer is very
cleverly and artistically outlined. Even the tuft of hair below the
chin is shown, and the great feet and the extra toes are correctly
pictured. Clearly the men who drew this reindeer lived with the
reindeer; and besides the reindeer, living near these men in the
south of France, was the great Mammoth.)
The Mammoth was like an Indian elephant, but with a coarse hairy
pelt. It was rather bigger than the big Indian elephant, and its
tusks had a different curvature; but we may dispose of the popular
idea that it was bigger than any elephant. No Siberian Mammoth has
yet been found higher at the shoulders than nine feet six inches,
whereas the African elephant stands eleven feet and sometimes more
at the shoulders. Among the fossil elephants of Southern Europe and
of North America (_Elephas imperator_) there are two which stood from
twelve to thirteen feet high. The remains of the Mammoth are left all
over the north of Europe and Asia and of the countries which were
subjected to glacial influences. Even in England its teeth and tusks
are constantly found, and in the Natural History Museum there is a
whole skull with enormous tusks, which was dug up in a brickfield
at Ilford. Probably this animal continued to exist longer in Asia
and Siberia than in our own part of the world: and the cold and ice
preserved their remains so well that whole carcases have been dug up.
One such instance is historic. In 1799 a native chief near Lake
Onkoul, in Siberia, while seeking for Mammoth teeth, perceived a
great shapeless mass among the ice. He watched it for some years,
till at the end of the fifth year the ice melted and disclosed the
carcase of a whole Mammoth.
In the month of March, 1804, Schumakhoff cut off the horns (the
tusks), which he exchanged with the merchant Bultunof for goods of
the value of fifty roubles (not quite eight pounds sterling). It was
not till two years after this that Mr. Adams, of the St. Petersburg
Academy, who was travelling with Count Golovkin, sent by the Czar of
Russia on an embassy to China, having been told at Yakutsk of the
discovery of an animal of extraordinary magnitude on the shores of
the Frozen Ocean, near the mouth of the River Lena, betook himself
to the place. He found the Mammoth still in the same place, but very
much mutilated. The Yakuts of the neighbourhood had cut off the
flesh, with which they fed their dogs; wild beasts, such as white
bears, wolves, wolverenes, and foxes, had also fed upon it, and
traces of their footsteps were seen around. The skeleton, almost
entirely cleared of its flesh, remained whole, with the exception of
one foreleg. The spine of the back, one scapula, the pelvis, and the
other three limbs were still held together by the ligaments and by
parts of the skin; the other scapula was found not far off. The head
was covered with a dry skin; one of the ears was furnished with a
tuft of hairs; the balls of the eyes were still distinguishable; the
brain still occupied the cranium, but seemed dried up; the point of
the lower lip had been gnawed and the upper lip had been destroyed so
as to expose the teeth; the neck was furnished with a long flowing
mane; the skin, of a dark-grey colour, covered with black hairs and a
reddish wool, was so heavy that ten persons found great difficulty in
transporting it to the shore.
There was collected, according to Mr. Adams, more than thirty-six
pounds weight of hair and wool which the white bears had trod into
the ground while devouring the flesh. This Mammoth was a male, so
fat and well fed, according to the assertion of the Tungusian chief,
that its belly hung down below the joints of its knees. Its tusks
were nine feet six inches in length, measured along the curve, and
its head without the tusks weighed four hundred and fourteen pounds
avoirdupois. Mr. Adams took every care to collect all that remained
of this unique specimen of an ancient creation, and forwarded the
parts to St. Petersburg, a distance of 11,000 versts (7330 miles).
He succeeded in repurchasing what he believed to be the tusks at
Yakutsk, and the Emperor of Russia, who became the owner of this
precious relic, paid him 8000 roubles.
The skeleton is deposited in the museum of the Academy of St.
Petersburg, and the skin still remains attached to the head and the
feet.
A very curious example of the Siberian Mammoth was discovered only a
few years ago by a Lamut of one of the Arctic villages, and through
the energy of Dr. Herz was eventually removed in pieces to St.
Petersburg. In the Zoological Museum there the reconstructed Mammoth
now crawls out of a huge pit, for it was by falling into a pit that
this fine beast met his death hundreds of generations ago. It was
sunk in frozen ground, and this cold-storage treatment had preserved
it in an extraordinary manner. If the Siberian natives who discovered
it partially buried in alluvial deposit had not uncovered it, so that
the sun was able to play on the carcase and produced decay, this
wonderful primeval monster might almost have been got out whole. As
it was the frozen ground had so kept the remains that Dr. Herz found
well-preserved fragments of food between the teeth, and the remains
of a hearty meal in the stomach. There is no doubt that the Mammoth
fell into the crevice or pit and damaged himself so much in the fall
that he could not crawl out. One cannot help feeling some relief that
he died after a short death-struggle. A good deal of the very old
meat of this body was eagerly eaten by the native dogs.