The Story of Evolution
by
Joseph McCabe
Part 5 out of 6
Such evidence as there is seems rather to suggest that South
Africa was the cradle of the placental mammals. We shall find
that many of our mammals originated in Africa; there, too, is
found to-day the most primitive representative of the Tertiary
mammals, the hyrax; and there we find in especial abundance the
remains of the mammal-like reptiles (Theromorphs) which are
regarded as their progenitors. Further search in the unexplored
geological treasures and dense forests of Africa is needed. We
may provisionally conceive the placental mammals as a group of
the South African early mammals which developed a fortunate
variation in womb-structure during the severe conditions of the
early Mesozoic. In this new structure they would have no
preponderant advantage as long as the genial Jurassic age
favoured the great reptiles, and they may have remained as small
and insignificant as the Marsupials. But with the fresh upheaval
and climatic disturbance at the end of the Jurassic, and during
the Cretaceous, they spread northward, and replaced the dying
reptiles, as the Angiosperms replaced the dying cycads. When they
met the spread of the Angiosperm vegetation they would receive
another great stimulus to development.
They appear in Europe and North America in the earliest
Cretaceous. The rise of the land had connected many hitherto
isolated regions, and they seem to have poured over every bridge
into all parts of the four continents. The obscurity of their
origin is richly compensated by their intense evolutionary
interest from the moment they enter the geological record. We
have seen this in the case of every important group of plants and
animals, and can easily understand it. The ancestral group was
small and local; the descendants are widely spread. While,
therefore, we discover remains of the later phases of development
in our casual cuttings and quarries, the ancestral tomb may
remain for ages in some unexplored province of the geological
world. If this region is, as we suspect, in Africa, our failure
to discover it as yet is all the more intelligible.
But these mammals of the early Tertiary are still of such a
patriarchal or ancestral character that the student of evolution
can dispense with their earlier phase. They combine in their
primitive frames, in an elementary way, the features which we now
find distributed in widely removed groups of their descendants.
Most of them fall into two large orders: the Condylarthra, the
ancestral herbivores from which we shall find our horses, oxen,
deer, elephants, and hogs gradually issuing, and the Creodonta,
the patriarchal carnivores, which will give birth to our lions
and tigers, wolves and foxes, and their various cousins. As yet
even the two general types of herbivore and carnivore are so
imperfectly separated that it is not always possible to
distinguish between them. Nearly all of them have the five-toed
foot of the reptile ancestor; and the flat nails on their toes
are the common material out of which the hoof of the ungulate and
the claw of the carnivore will be presently fashioned. Nearly all
have forty-four simply constructed teeth, from which will be
evolved the grinders and tusks of the elephant or the canines of
the tiger. They answer in every respect to the theory that some
primitive local group was the common source of all our great
mammals. With them are ancestral forms of Edentates (sloths,
etc.) and Insectivores (moles, etc.), side-branches developing
according to their special habits; and before the end of the
Eocene we find primitive Rodents (squirrels, etc.) and
Cheiroptera (bats).
From the description of the Tertiary world which we have seen in
the last chapter we understand the rapid evolution of the
herbivorous Condylarthra. The rich vegetation which spreads over
the northern continents, to which they have penetrated, gives
them an enormous vitality and fecundity, and they break into
groups, as they increase in number, adapted to the different
conditions of forest, marsh, or grass-covered plain. Some of
them, swelling lazily on the abundant food, and secure for a time
in their strength, become the Deinosaurs of their age, mere
feeding and breeding machines. They are massive, sluggish,
small-brained animals, their strong stumpy limbs terminating in
broad five-toed feet. Coryphodon, sometimes as large as an ox, is
a typical representative. It is a type fitted only for prosperous
days, and these Amblypoda, as they are called, will disappear as
soon as the great carnivores are developed.
Another doomed race, or abortive experiment of early mammal life,
were the remarkable Deinocerata ("terrible-horned" mammals). They
sometimes measured thirteen feet in length, but had little use
for brain in the conditions in which they were developed. The
brain of the Deinoceras was only one-eighth the size of the brain
of a rhinoceros of the same bulk; and the rhinoceros is a
poor-brained representative of the modern mammals. To meet the
growing perils of their race they seem to have developed three
pairs of horns on their long, flat skulls, as we find on them
three pairs of protuberances. A late specimen of the group,
Tinoceras, had a head four feet in length, armed with these six
horns, and its canine teeth were developed into tusks sometimes
seven or eight inches in length. They suggest a race of powerful
but clumsy and grotesque monsters, making a last stand, and
developing such means of protection as their inelastic nature
permitted. But the horns seem to have proved a futile protection
against the advancing carnivores, and the race was extinguished.
The horns may, of course, have been mainly developed by, or for,
the mutual butting of the males.
The extinction of these races will remind many readers of a
theory on which it is advisable to say a word. It will be
remembered that the last of the Deinosaurs and the Ammonites also
exhibited some remarkable developments in their last days. These
facts have suggested to some writers the idea that expiring races
pass through a death-agony, and seem to die a natural death of
old age like individuals. The Trilobites are quoted as another
instance; and some ingenious writers add the supposed
eccentricities of the Roman Empire in its senile decay and a
number of other equally unsubstantial illustrations.
There is not the least ground for this fantastic speculation. The
destruction of these "doomed races" is as clearly traceable to
external causes as is the destruction of the Roman Empire; nor,
in fact, did the Roman Empire develop any such eccentricities as
are imagined in this superficial theory. What seem to our eye the
"eccentricities" and "convulsions" of the Ceratopsia and
Deinocerata are much more likely to be defensive developments
against a growing peril, but they were as futile against the new
carnivores as were the assegais of the Zulus against the
European. On the other hand, the eccentricities of many of the
later Trilobites--the LATEST Trilobites, it may be noted, were
chaste and sober specimens of their race, like the last Roman
patricians--and of the Ammonites may very well have been caused
by physical and chemical changes in the sea-water. We know from
experiment that such changes have a disturbing influence,
especially on the development of eggs and larvae; and we know
from the geological record that such changes occurred in the
periods when the Trilobites and Ammonites perished. In fine, the
vast majority of extinct races passed through no "convulsions"
whatever. We may conclude that races do not die; they are killed.
The extinction of these races of the early Condylarthra, and the
survival of those races whose descendants share the earth with us
to-day, are quite intelligible. The hand of natural selection lay
heavy on the Tertiary herbivores. Apart from overpopulation,
forcing groups to adapt themselves to different regions and
diets, and apart from the geological disturbances and climatic
changes which occurred in nearly every period, the shadow of the
advancing carnivores was upon them. Primitive but formidable
tigers, wolves, and hyenas were multiplying, and a great
selective struggle set in. Some groups shrank from the battle by
burrowing underground like the rabbit; some, like the squirrel or
the ape, took refuge in the trees; some, like the whale and seal,
returned to the water; some shrank into armour, like the
armadillo, or behind fences of spines, like the hedgehog; some,
like the bat, escaped into the air. Social life also was probably
developed at this time, and the great herds had their sentinels
and leaders. But the most useful qualities of the large
vegetarians, which lived on grass and leaf, were acuteness of
perception to see the danger, and speed of limb to escape it. In
other words, increase of brain and sense-power and increase of
speed were the primary requisites. The clumsy early Condylarthra
failed to meet the tests, and perished; the other branches of the
race were more plastic, and, under the pressure of a formidable
enemy, were gradually moulded into the horse, the deer, the ox,
the antelope, and the elephant.
We can follow the evolution of our mammals of this branch most
easily by studying the modification of the feet and limbs. In a
running attitude--the experiment may be tried--the weight of the
body is shifted from the flat sole of the foot, and thrown upon
the toes, especially the central toes. This indicates the line of
development of the Ungulates (hoofed animals) in the struggle of
the Tertiary Era. In the early Eocene we find the Condylarthra
(such as Phenacodus) with flat five-toed feet, and such a mixed
combination of characters that they "might serve very well for
the ancestors of all the later Ungulata" (Woodward). We then
presently find this generalised Ungulate branching into three
types, one of which seems to be a patriarchal tapir, the second
is regarded as a very remote ancestor of the horse, and the third
foreshadows the rhinoceros. The feet have now only three or four
toes; one or two of the side-toes have disappeared. This
evolution, however, follows two distinct lines. In one group of
these primitive Ungulates the main axis of the limb, or the
stress of the weight, passes through the middle toe. This group
becomes the Perissodactyla ("odd-toed" Ungulates) of the
zoologist, throwing out side-branches in the tapir and the
rhinoceros, and culminating in the one-toed horse. In the other
line, the Artiodactyla (the "even-toed" or cloven-hoofed
Ungulates), the main axis or stress passes between the third and
fourth toes, and the group branches into our deer, oxen, sheep,
pigs, camels, giraffes, and hippopotamuses. The elephant has
developed along a separate and very distinctive line, as we shall
see, and the hyrax is a primitive survivor of the ancestral
group.
Thus the evolutionist is able to trace a very natural order in
the immense variety of our Ungulates. He can follow them in
theory as they slowly evolve from their primitive Eocene ancestor
according to their various habits and environments; he has a very
rich collection of fossil remains illustrating the stages of
their development; and in the hyrax (or "coney") he has one more
of those living fossils, or primitive survivors, which still
fairly preserve the ancestral form. The hyrax has four toes on
the front foot and three on the hind foot, and the feet are flat.
Its front teeth resemble those of a rodent, and its molars those
of the rhinoceros. In many respects it is a most primitive and
generalised little animal, preserving the ancestral form more or
less faithfully since Tertiary days in the shelter of the African
Continent.
The rest of the Ungulates continued to develop through the
Tertiary, and fortunately we are enabled to follow the
development of two of the most interesting of them, the horse and
the elephant, in considerable detail. As I said above, the
primitive Ungulate soon branches into three types which dimly
foreshadow the tapir, the horse, and the rhinoceros, the three
forms of the Perissodactyl. The second of these types is the
Hyracotherium. It has no distinct equine features, and is known
only from the skull, but the authorities regard it as the
progenitor (or representative of the progenitors) of the
horse-types. In size it must have been something like the rabbit
or the hyrax. Still early in the Eocene, however, we find the
remains of a small animal (Eohippus), about the size of a fox,
which is described as "undoubtedly horse-like." It had only three
toes on its hind feet, and four on its front feet; though it had
also a splint-bone, representing the shrunken and discarded fifth
toe, on its fore feet. Another form of the same period
(Protorohippus) shows the central of the three toes on the hind
foot much enlarged, and the lateral toes shrinking. The teeth,
and the bones and joints of the limbs, are also developing in the
direction of the horse.
In the succeeding geological period, the Oligocene, we find
several horse-types in which the adaptation of the limbs to
running on the firm grassy plains and of the teeth to eating the
grass continues. Mesohippus has lost the fourth toe of the fore
foot, which is now reduced to a splintbone, and the lateral toes
of its hind foot are shrinking. In the Miocene period there is a
great development of the horse-like mammals. We have the remains
of more than forty species, some continuing the main line of
development on the firm and growing prairies of the Miocene, some
branching into the softer meadows or the forests, and giving rise
to types which will not outlive the Tertiary. They have three
toes on each foot, and have generally lost even the rudimentary
trace of the fourth toe. In most of them, moreover, the lateral
toes--except in the marsh-dwelling species, with spreading
feet--scarcely touch the ground, while the central toe is
developing a strong hoof. The leg-bones are longer, and have a
new type of joint; the muscles are concentrated near the body.
The front teeth are now chopping incisors, and the grinding teeth
approach those of the modern horse in the distribution of the
enamel, dentine, and cement. They are now about the size of a
donkey, and must have had a distinctly horsy appearance, with
their long necks and heads and tapering limbs. One of them,
Merychippus, was probably in the direct line of the evolution of
the horse. From Hipparion some of the authorities believe that
the zebras may have been developed. Miohippus, Protohippus, and
Hypohippus, varying in size from that of a sheep to that of a
donkey, are other branches of this spreading family.
In the Pliocene period the evolution of the main stem culminates
in the appearance of the horse, and the collateral branches are
destroyed. Pliohippus is a further intermediate form. It has only
one toe on each foot, with two large splint bones, but its hoof
is less round than that of the horse, and it differs in the shape
of the skull and the length of the teeth. The true horse (Equus)
at length appears, in Europe and America, before the close of the
Tertiary period. As is well known, it still has the rudimentary
traces of its second and fourth toes in the shape of splint
bones, and these bones are not only more definitely toe-shaped in
the foal before birth, but are occasionally developed and give us
a three-toed horse.
From these successive remains we can confidently picture the
evolution, during two or three million years, of one of our most
familiar mammals. It must not, of course, be supposed that these
fossil remains all represent "ancestors of the horse." In some
cases they may very well do so; in others, as we saw, they
represent sidebranches of the family which have become extinct.
But even such successive forms as the Eohippus, Mesohippus,
Miohippus, and Pliohippus must not be arranged in a direct line
as the pedigree of the horse. The family became most extensive in
the Miocene, and we must regard the casual fossil specimens we
have discovered as illustrations of the various phases in the
development of the horse from the primitive Ungulate. When we
recollect what we saw in an earlier chapter about the evolution
of grassy plains and the successive rises of the land during the
Tertiary period, and when we reflect on the simultaneous advance
of the carnivores, we can without difficulty realise this
evolution of our familiar companion from a hyrax-like little
animal of two million years ago.
We have not in many cases so rich a collection of intermediate
forms as in the case of the horse, but our fossil mammals are
numerous enough to suggest a similar development of all the
mammals of to-day. The primitive family which gave birth to the
horse also gave us, as we saw, the tapir and the rhinoceros. We
find ancestral tapirs in Europe and America during the Tertiary
period, but the later cold has driven them to the warm swamps of
Brazil and Malaysia. The rhinoceros has had a long and
interesting history. From the primitive Hyrochinus of the Eocene,
in which it is dimly foreshadowed, we pass to a large and varied
family in the later periods. In the Oligocene it spreads into
three great branches, adapted, respectively, to life on the
elevated lands, the lowlands, and the water. The upland type
(Hyracodon) was a light-limbed running animal, well illustrating
the close relation to the horse. The aquatic representative
(Metamynodon) was a stumpy and bulky animal. The intermediate
lowland type was probably the ancestor of the modern animal. All
three forms were yet hornless. In the Miocene the lowland type
(Leptaceratherium, Aceratherium, etc.) develops vigorously, while
the other branches die. The European types now have two horns,
and in one of the American species (Diceratherium) we see a
commencement of the horny growths from the skull. We shall see
later that the rhinoceros continued in Europe even during the
severe conditions of the glacial period, in a branch that
developed a woolly coat.
There were also in the early Tertiary several sidebranches of the
horse-tapir-rhinoceros family. The Palaeotheres were more or less
between the horse and the tapir in structure; the Anoplotheres
between the tapir and the ruminant. A third doomed branch, the
Titanotheres, flourished vigorously for a time, and begot some
strange and monstrous forms (Brontops, Titanops, etc.). In the
larger specimens the body was about fourteen feet long, and stood
ten feet from the ground. The long, low skull had a pair of horns
over the snout. They perished like the equally powerful but
equally sluggish and stupid Deinocerata. The Tertiary was an age
of brain rather than of brawn. As compared with their early
Tertiary representatives' some of our modern mammals have
increased seven or eight-fold in brain-capacity.
While the horses and tapirs and rhinoceroses were being gradually
evolved from the primitive types, the Artiodactyl branch of the
Ungulates--the pigs, deer, oxen, etc.--were also developing. We
must dismiss them briefly. We saw that the primitive herbivores
divided early in the Eocene into the "odd-toed" and "even-toed"
varieties; the name refers, it will be remembered, not to the
number of toes, but to the axis of stress. The Artiodactyl group
must have quickly branched in turn, as we find very primitive
hogs and camels before the end of the Eocene. The first hog-like
creature (Homacodon) was much smaller than the hog of to-day, and
had strong canine teeth, but in the Oligocene the family gave
rise to a large and numerous race, the Elotheres. These
"giant-pigs," as they have been called, with two toes on each
foot, flourished vigorously for a time in Europe and America, but
were extinguished in the Miocene, when the true pigs made their
appearance. Another doomed race of the time is represented by the
Hyopotamus, an animal between the pig and the hippopotamus; and
the Oreodontids, between the hog and the deer, were another
unsuccessful branch of the early race. The hippopotamus itself
was widespread in Europe, and a familiar form in the rivers of
Britain, in the latter part of the Tertiary.
The camel seems to be traceable to a group of primitive North
American Ungulates (Paebrotherium, etc.) in the later Eocene
period. The Paebrotherium, a small animal about two feet long, is
followed by Pliauchenia, which points toward the llamas and
vicunas, and Procamelus, which clearly foreshadows the true
camel. In the Pliocene the one branch went southward, to develop
into the llamas and vicunas, and the other branch crossed to
Asia, to develop into the camels. Since that time they have had
no descendants in North America.
The primitive giraffe appears suddenly in the later Tertiary
deposits of Europe and Asia. The evidence points to an invasion
from Africa, and, as the region of development is unknown and
unexplored, the evolution of the giraffe remains a matter of
speculation. Chevrotains flourished in Europe and North America
in the Oligocene, and are still very primitive in structure,
combining features of the hog and the ruminants. Primitive deer
and oxen begin in the Miocene, and seem to have an earlier
representative in certain American animals (Protoceras), of which
the male has a pair of blunt outgrowths between the ears. The
first true deer are hornless (like the primitive muskdeer of Asia
to-day), but by the middle of the Miocene the males have small
two-pronged antlers, and as the period proceeds three or four
more prongs are added. It is some confirmation of the
evolutionary embryonic law that we find the antlers developing in
this way in the individual stag to-day. A very curious race of
ruminants in the later Tertiary was a large antelope
(Sivatherium) with four horns. It had not only the dimensions,
but apparently some of the characters, of an elephant.
The elephant itself, the last type of the Ungulates, has a
clearer line of developments. A chance discovery of fossils in
the Fayum district in Egypt led Dr. C. W. Andrews to make a
special exploration, and on the remains which he found he has
constructed a remarkable story of the evolution of the elephant.*
It is clear that the elephant was developed in Africa, and a
sufficiently complete series of remains has been found to give a
good idea of the origin of its most distinctive features. In the
Eocene period there lived in the Egyptian region an animal,
something like the tapir in size and appearance, which had its
second incisors developed into small tusks and--to judge from the
nasal opening in the skull--a somewhat prolonged snout. This
animal (Moeritherium) only differed from the ordinary primitive
Ungulate in these incipient elephantine features. In the later
Eocene a larger and more advanced animal, the Palaeomastodon,
makes its appearance. Its tusks are larger (five or six inches
long), its molars more elephantine, the air-cells at the back of
the head more developed. It would look like a small elephant,
except that it had a long snout, instead of a flexible trunk, and
a projecting lower jaw on which the snout rested.
*See this short account, "Guide to the Elephants in the British
Museum," 1908.
Up to the beginning of the Miocene, Africa was, as we saw, cut
off from Europe and Asia by the sea which stretched from Spain to
India. Then the land rose, and the elephant passed by the new
tracts into the north. Its next representative, Tetrabelodon, is
found in Asia and Europe, as well as North Africa. The frame is
as large as that of a medium-sized elephant, and the increase of
the air-cells at the back of the skull shows that an increased
weight has to be sustained by the muscles of the neck. The
nostrils are shifted further back. The tusks are from twenty to
thirty inches long, and round, and only differ from those of the
elephant in curving slightly downward, The chin projects as far
as the tusks. The neck is shorter and thicker, and, as the animal
increases in height, we can understand that the long
snout--possibly prehensile at its lower end--is necessary for the
animal to reach the ground. But the snout still lies on the
projecting lower jaw, and is not a trunk. Passing over the many
collateral branches, which diverge in various directions, we next
kind that the chin is shortening (in Tetrabelodon longirostris),
and, through a long series of discovered intermediate forms, we
trace the evolution of the elephant from the mastodon. The long
supporting skin disappears, and the enormous snout becomes a
flexible trunk. Southern Asia seems to have been the province of
this final transformation, and we have remains of some of these
primitive elephants with tusks nine and a half feet long. A later
species, which wandered over Central and Southern Europe before
the close of the Tertiary, stood fifteen feet high at the
shoulder, while the mammoth, which superseded it in the days of
early man, had at times tusks more than ten feet in length.
It is interesting to reflect that this light on the evolution of
one of our most specialised mammals is due to the chance opening
of the soil in an obscure African region. It suggests to us that
as geological exploration is extended, many similar discoveries
may be made. The slenderness of the geological record is a defect
that the future may considerably modify.
From this summary review of the evolution of the Ungulates we
must now pass to an even briefer account of the evolution of the
Carnivores. The evidence is less abundant, but the characters of
the Carnivores consist so obviously of adaptations to their
habits and diet that we have little difficulty in imagining their
evolution. Their early Eocene ancestors, the Creodonts, gave rise
in the Eocene to forms which we may regard as the forerunners of
the cat-family and dog-family, to which most of our familiar
Carnivores belong. Patriofelis, the "patriarchal cat," about five
or six feet in length (without the tail), curiously combines the
features of the cat and the seal-family. Cyonodon has a wolf-like
appearance, and Amphicyon rather suggests the fox. Primitive
weasels, civets, and hyaenas appear also in the Eocene. The
various branches of the Carnivore family are already roughly
represented, but it is an age of close relationships and
generalised characters.
In the Miocene we find the various groups diverging still further
from each other and from the extinct stocks. Definite wolves and
foxes abound in America, and the bear, civet, and hyaena are
represented in Europe, together with vague otter-like forms. The
dog-family seems to have developed chiefly in North America. As
in the case of the Ungulates, we find many strange side-branches
which flourished for a time, but are unknown to-day. Machoerodus,
usually known as "the sabre-toothed tiger," though not a tiger,
was one of the most formidable of these transitory races. Its
upper canine teeth (the "sabres") were several inches in length,
and it had enormously distensible jaws to make them effective.
The great development of such animals, with large numbers of
hyaenas, civets, wolves, bears, and other Carnivores, in the
middle and later Tertiary was probably the most effective agency
in the evolution of the horse and deer and the extinction of the
more sluggish races. The aquatic branch of the Carnivores (seals,
walruses, etc.) is little represented in the Tertiary record. We
saw, however, that the most primitive representatives of the
elephant-stock had also some characters of the seal, and it is
thought that the two had a common origin.
The Moeritherium was a marsh-animal, and may very well have been
cousin to the branch of the family which pushed on to the seas,
and developed its fore limbs into paddles.
The Rodents are represented in primitive form early in the Eocene
period. The teeth are just beginning to show the characteristic
modification for gnawing. A large branch of the family, the
Tillodonts, attained some importance a little later. They are
described as combining the head and claws of a bear with the
teeth of a rodent and the general characters of an ungulate. In
the Oligocene we find primitive squirrels, beavers, rabbits, and
mice. The Insectivores also developed some of the present types
at an early date, and have since proved so unprogressive that
some regard them as the stock from which all the placental
mammals have arisen.
The Cetacea (whales, porpoises, etc.) are already represented in
the Eocene by a primitive whale-like animal (Zeuglodon) of
unknown origin. Some specimens of it are seventy feet in length.
It has large teeth, sometimes six inches long, and is clearly a
terrestrial mammal that has returned to the waters. Some forms
even of the modern whale develop rudimentary teeth, and in all
forms the bony structure of the fore limbs and degenerate relic
of a pelvis and back limbs plainly tell of the terrestrial
origin. Dolphins appear in the Miocene.
Finally, the Edentates (sloths, anteaters, and armadilloes) are
represented in a very primitive form in the early Eocene. They
are then barely distinguishable from the Condylarthra and
Creodonta, and seem only recently to have issued from a common
ancestor with those groups. In the course of the Tertiary we find
them--especially in South America, which was cut off from the
North and its invading Carnivores during the Eocene and
Miocene--developed into large sloths, armadilloes, and anteaters.
The reconnection with North America in the Pliocene allowed the
northern animals to descend, but gigantic sloths (Megatherium)
and armadilloes (Glyptodon) flourished long afterwards in South
America. The Megatherium attained a length of eighteen feet in
one specimen discovered, and the Glyptodon often had a dorsal
shield (like that of the armadillo) from six to eight feet long,
and, in addition, a stoutly armoured tail several feet long.
The richness and rapidity of the mammalian development in the
Tertiary, of which this condensed survey will convey some
impression, make it impossible to do more here than glance over
the vast field and indicate the better-known connections. It will
be seen that evolution not only introduces a lucid order and
arrangement into our thousands of species of living and fossil
mammals, but throws an admirable light on the higher animal world
of our time. The various orders into which the zoologist puts our
mammals are seen to be the branches of a living tree, approaching
more and more closely to each other in early Tertiary times, in
spite of the imperfectness of the geological record. We at last
trace these diverging lines to a few very primitive, generalised,
patriarchal groups, which in turn approach each other very
closely in structure, and plainly suggest a common Cretaceous
ancestor. Whether that common ancestor was an Edentate, an
Insectivore, or Creodont, or something more primitive than them
all, is disputed. But the divergence of nearly all the lines of
our mammal world from those patriarchal types is admirably clear.
In the mutual struggle of carnivore and herbivore, in adaptation
to a hundred different environments (the water, the land, and the
air, the tree, the open plain, the underground, the marsh, etc.)
and forms of diet, we find the descendants of these patriarchal
animals gradually developing their distinctive characters. Then
we find the destructive agencies of living and inorganic nature
blotting out type after type, and the living things that spread
over the land in the later Tertiary are found to be broadly
identical with the living things of to-day. The last great
selection, the northern Ice-Age, will give the last touches of
modernisation.
CHAPTER XVIII. THE EVOLUTION OF MAN
We have reserved for a closer inquiry that order of the placental
mammals to which we ourselves belong, and on which zoologists
have bestowed the very proper and distinguishing name of the
Primates. Since the days of Darwin there has been some tendency
to resent the term "lower animals," which man applies to his
poorer relations. But, though there is no such thing as an
absolute standard by which we may judge the "higher" or "lower"
status of animals or plants, the extraordinary power which man
has by his brain development attained over both animate and
inanimate nature fully justifies the phrase. The Primate order
is, therefore, of supreme interest as the family that gave birth
to man, and it is important to discover the agencies which
impelled some primitive member of it to enter upon the path which
led to this summit of organic nature.
The order includes the femurs, a large and primitive family with
ape-like features--the Germans call them "half-apes"--the
monkeys, the man-like apes, and man. This classification
according to structure corresponds with the successive appearance
of the various families in the geological record. The femurs
appear in the Eocene; the monkeys, and afterwards the apes, in
the Miocene, the first semi-human forms in the Pleistocene,
though they must have been developed before this. It is hardly
necessary to say that science does not regard man as a descendant
of the known anthropoid apes, or these as descended from the
monkeys. They are successive types or phases of development,
diverging early from each other. Just as the succeeding
horse-types of the record are not necessarily related to each
other in a direct line, yet illustrate the evolution of a type
which culminates in the horse, so the spreading and branching
members of the Primate group illustrate the evolution of a type
of organism which culminates in man. The particular relationship
of the various families, living and dead, will need careful
study.
That there is a general blood-relationship, and that man is much
more closely related to the anthropoid apes than to any of the
lower Primates, is no longer a matter of controversy. In Rudolph
Virchow there died, a few years ago, the last authoritative man
of science to express any doubt about it. There are, however,
non-scientific writers who, by repeating the ambiguous phrase
that it is "only a theory," convey the impression to inexpert
readers that it is still more or less an open question. We will
therefore indicate a few of the lines of evidence which have
overcome the last hesitations of scientific men, and closed the
discussion as to the fact.
The very close analogy of structure between man and the ape at
once suggests that they had a common ancestor. There are cases in
which two widely removed animals may develop a similar organ
independently, but there is assuredly no possibility of their
being alike in all organs, unless by common inheritance. Yet the
essential identity of structure in man and the ape is only
confirmed by every advance of science, and would of itself prove
the common parentage. Such minor differences as there are between
man and the higher ape--in the development of the cerebrum, the
number of the teeth or ribs, the distribution of the hair, and so
on--are quite explicable when we reflect that the two groups must
have diverged from each other more than a million years ago
Examining the structure of man more closely, we find this strong
suggestion of relationship greatly confirmed. It is now well
known that the human body contains a number of vestigial
"organs"--organs of no actual use, and only intelligible as
vestiges of organs that were once useful. Whatever view we take
of the origin of man, each organ in his frame must have a
meaning; and, as these organs are vestigial and useless even in
the lowest tribes of men, who represent primitive man, they must
be vestiges of organs that were of use in a remote pre-human
ancestor. The one fact that the ape has the same vestigial organs
as man would, on a scientific standard of evidence, prove the
common descent of the two. But these interesting organs
themselves point back far earlier than a mixed ape-human ancestor
in many cases.
The shell of cartilage which covers the entrance to the ear--the
gristly appendage which is popularly called the ear--is one of
the clearest and most easily recognised of these organs. The
"ear" of a horse or a cat is an upright mobile shell for catching
the waves of sound. The human ear has the appearance of being the
shrunken relic of such an organ, and, when we remove the skin,
and find seven generally useless muscles attached to it,
obviously intended to pull the shell in all directions (as in the
horse), there can be no doubt that the external ear is a
discarded organ, a useless legacy from an earlier ancestor. In
cases where it has been cut off it was found that the sense of
hearing was scarcely, if at all, affected. Now we know that it is
similarly useless in all tribes of men, and must therefore come
from a pre-human ancestor. It is also vestigial in the higher
apes, and it is only when we descend to the lower monkeys and
femurs that we see it approaching its primitive useful form. One
may almost say that it is a reminiscence of the far-off period
when, probably in the early Tertiary, the ancestors of the
Primates took to the trees. The animals living on the plain
needed acute senses to detect the approach of their prey or their
enemies; the tree-dweller found less demand on his sense of
hearing, the "speaking-trumpet" was discarded, and the
development of the internal ear proceeded on the higher line of
the perception of musical sounds.
We might take a very large number of parts of the actual human
body, and discover that they are similar historical or
archaeological monuments surviving in a modern system, but we
have space only for a few of the more conspicuous.
The hair on the body is a vestigial organ, of actual use to no
race of men, an evident relic of the thick warm coat of an
earlier ancestor. It in turn recalls the dwellers in the primeval
forest. In most cases--not all, because the wearing of clothes
for ages has modified this feature--it will be found that the
hairs on the arm tend upward from the wrist to the elbow, and
downward from the shoulder to the elbow. This very peculiar
feature becomes intelligible when we find that some of the apes
also have it, and that it has a certain use in their case. They
put their hands over their heads as they sit in the trees during
ram, and in that position the sloping hair acts somewhat like the
thatched roof of a cottage.
Again, it will be found that in the natural position of standing
we are not perfectly flat-footed, but tend to press much more on
the outer than on the inner edge of the foot. This tendency,
surviving after ages of living on the level ground, is a
lingering effect of the far-off arboreal days.
A more curious reminiscence is seen in the fact that the very
young infant, flabby and powerless as it is in most of its
muscles, is so strong in the muscles of the hand and arm that it
can hang on to a stick by its hands, and sustain the whole weight
of its body, for several minutes. Finally, our vestigial
tail--for we have a tail comparable to that of the higher
apes--must be mentioned. In embryonic development the tail is
much longer than the legs, and some children are born with a real
tail, which they move as the puppy does, according to their
emotional condition. Other features of the body point back to an
even earlier stage. The vermiform appendage--in which some recent
medical writers have vainly endeavoured to find a utility-- is
the shrunken remainder of a large and normal intestine of a
remote ancestor. This interpretation of it would stand even if it
were found to have a certain use in the human body. Vestigial
organs are sometimes pressed into a secondary use when their
original function has been lost. The danger of this appendage in
the human body to-day is due to the fact that it is a blind alley
leading off the alimentary canal, and has a very narrow opening.
In the ape the opening is larger, and, significantly enough, it
is still larger in the human foetus. When we examine some of the
lower mammals we discover the meaning of it. It is in them an
additional storage chamber in the alimentary system. It is
believed that a change to a more digestible diet has made this
additional chamber superfluous in the Primates, and the system is
slowly suppressing it.
Other reminiscences of this earlier phase are found in the many
vestigial muscles which are found in the body to-day. The head of
the quadruped hangs forward, and is held by powerful muscles and
ligaments in the neck. We still have the shrunken remainder of
this arrangement. Other vestigial muscles are found in the
forehead, the scalp, the nose--many people can twitch the
nostrils and the scalp--and under the skin in many parts of the
body. These are enfeebled remnants of the muscular coat by which
the quadruped twitches its skin, and drives insects away. A less
obvious feature is found by the anatomist in certain
blood-vessels of the trunk. As the blood flows vertically in a
biped and horizontally in a quadruped, the arrangement of the
valves in the blood-vessels should be different in the two cases;
but it is the same in us as in the quadruped. Another trace of
the quadruped ancestor is found in the baby. It walks "on all
fours" so long, not merely from weakness of the limbs, but
because it has the spine of a quadruped.
A much more interesting fact, but one less easy to interpret, is
that the human male has, like the male ape, organs for suckling
the young. That there are real milk-glands, usually vestigial,
underneath the teats in the breast of the boy or the man is
proved by the many known cases in which men have suckled the
young. Several friends of the present writer have seen this done
in India and Ceylon by male "wet-nurses." As there is no tribe of
men or species of ape in which the male suckles the young
normally, we seem to be thrown back once more upon an earlier
ancestor. The difficulty is that we know of no mammal of which
both parents suckle the young, and some authorities think that
the breasts have been transferred to the male by a kind of
embryonic muddle. That is difficult to believe, as no other
feature has ever been similarly transferred to the opposite sex.
In any case the male breasts are vestigial organs. Another
peculiarity of the mammary system is that sometimes three, four,
or five pairs of breasts appear in a woman (and several have been
known even in a man). This is, apparently, an occasional
reminiscence of an early mammal ancestor which had large litters
of young and several pairs of breasts.
But there are features of the human body which recall an ancestor
even earlier than the quadruped. The most conspicuous of these is
the little fleshy pad at the inner corner of each eye. It is a
common feature in mammals, and is always useless. When, however,
we look lower down in the animal scale we find that fishes and
reptiles (and birds) have a third eyelid, which is drawn across
the eye from this corner. There is little room to doubt that the
little fleshy vestige in the mammal's eye is the shrunken
remainder of the lateral eyelid of a remote fish-ancestor.
A similar reminiscence is found in the pineal body, a small and
useless object, about the size and shape of a hazel-nut, in the
centre of the brain. When we examine the reptile we find a third
eye in the top of the head. The skin has closed over it, but the
skull is still, in many cases, perforated as it is for the eyes
in front. I have seen it standing out like a ball on the head of
a dead crocodile, and in the living tuatara--the very primitive
New Zealand lizard--it still has a retina and optic nerve. As the
only animal in nature to-day with an eye in this position (the
Pyrosome, a little marine animal of the sea-squirt family) is not
in the line of reptile and mammal ancestry, it is difficult to
locate the third eye definitely. But when we find the skin
closing over it in the amphibian and reptile, then the bone, and
then see it gradually atrophying and being buried under the
growing brain, we must refer it to some early fish-ancestor. This
ancestor, we may recall, is also reflected for a time in the
gill-slits and arches, with their corresponding fish-like heart
and blood-vessels, during man's embryonic development, as we saw
in a former chapter.
These are only a few of the more conspicuous instances of
vestigial structures in man. Metchnikoff describes about a
hundred of them. Even if there were no remains of primitive man
pointing in the direction of a common ancestry with the ape, no
lower types of men in existence with the same tendency, no apes
found in nature to-day with a structure so strikingly similar to
that of man, and no fossil records telling of the divergence of
forms from primitive groups in past time, we should be forced to
postulate the evolution of man in order to explain his actual
features. The vestigial structures must be interpreted as we
interpret the buttons on the back of a man's coat. They are
useless reminiscences of an age in which they were useful. When
their witness to the past is supported by so many converging
lines of evidence it becomes irresistible. I will add only one
further testimony which has been brought into court in recent
years.
The blood consists of cells, or minute disk-shaped corpuscles,
floating in a watery fluid, or serum. It was found a few years
ago, in the course of certain experiments in mixing the blood of
animals, that the serum of one animal's blood sometimes destroyed
the cells of the other animal's blood, and at other times did
not. When the experiments were multiplied, it was found that the
amount of destructive action exercised by one specimen of blood
upon another depended on the nearness or remoteness of
relationship between the animals. If the two are closely related,
there is no disturbance when their blood is mixed; when they are
not closely related, the serum of one destroys the cells of the
other, and the intensity of the action is in proportion to their
remoteness from each other. Another and more elaborate form of
the experiment was devised, and the law was confirmed. On both
tests it was found by experiment that the blood of man and of the
anthropoid ape behaved in such a way as to prove that they were
closely related. The blood of the monkey showed a less close
relationship--a little more remote in the New World than in the
Old World monkeys; and the blood of the femur showed a faint and
distant relationship.
The FACT of the evolution of man and the apes from a common
ancestor is, therefore, outside the range of controversy in
science; we are concerned only to retrace the stages of that
evolution, and the agencies which controlled it. Here,
unfortunately, the geological record gives us little aid.
Tree-dwelling animals are amongst the least likely to be buried
in deposits which may preserve their bones for ages. The
distribution of femur and ape remains shows that the order of the
Primates has been widespread and numerous since the middle of the
Tertiary Era, yet singularly few remains of the various families
have been preserved.
Hence the origin of the Primates is obscure. They are first
foreshadowed in certain femur-like forms of the Eocene period,
which are said in some cases (Adapis) to combine the characters
of pachyderms and femurs, and in others (Anaptomorphus) to unite
the features of Insectivores and femurs. Perhaps the more common
opinion is that they were evolved from a branch of the
Insectivores, but the evidence is too slender to justify an
opinion. It was an age when the primitive placental mammals were
just beginning to diverge from each other, and had still many
features in common. For the present all we can say is that in the
earliest spread of the patriarchal mammal race one branch adopted
arboreal life, and evolved in the direction of the femurs and the
apes. The generally arboreal character of the Primates justifies
this conclusion.
In the Miocene period we find a great expansion of the monkeys.
These in turn enter the scene quite suddenly, and the authorities
are reduced to uncertain and contradictory conjectures as to
their origin. Some think that they develop not from the femurs,
but along an independent line from the Insectivores, or other
ancestors of the Primates. We will not linger over these early
monkeys, nor engage upon the hopeless task of tracing their
gradual ramification into the numerous families of the present
age. It is clear only that they soon divided into two main
streams, one of which spread into the monkeys of America and the
other into the monkeys of the Old World. There are important
anatomical differences between the two. The monkeys remained in
Central and Southern Europe until near the end of the Tertiary.
Gradually we perceive that the advancing cold is driving them
further south, and the monkeys of Gibraltar to-day are the
diminished remnant of the great family that had previously
wandered as far as Britain and France.
A third wave, also spreading in the Miocene, equally obscure in
its connection with the preceding, introduces the man-like apes
to the geologist. Primitive gibbons (Pliopithecus and
Pliobylobates), primitive chimpanzees (Palaeopithecus), and other
early anthropoid apes (Oreopithecus, Dryopithecus, etc.), lived
in the trees of Southern Europe in the second part of the
Tertiary Era. They are clearly disconnected individuals of a
large and flourishing family, but from the half-dozen specimens
we have yet discovered no conclusion can be drawn, except that
the family is already branching into the types of anthropoid apes
which are familiar to us.
Of man himself we have no certain and indisputable trace in the
Tertiary Era. Some remains found in Java of an ape-man
(Pithecanthropus), which we will study later, are now generally
believed, after a special investigation on the spot, to belong to
the Pleistocene period. Yet no authority on the subject doubts
that the human species was evolved in the Tertiary Era, and very
many, if not most, of the authorities believe that we have
definite proof of his presence. The early story of mankind is
gathered, not so much from the few fragments of human remains we
have, but from the stone implements which were shaped by his
primitive intelligence and remain, almost imperishable, in the
soil over which he wandered. The more primitive man was, the more
ambiguous would be the traces of his shaping of these stone
implements, and the earliest specimens are bound to be a matter
of controversy. It is claimed by many distinguished authorities
that flints slightly touched by the hand of man, or at least used
as implements by man, are found in abundance in England, France,
and Germany, and belong to the Pliocene period. Continental
authorities even refer some of them to the Miocene and the last
part of the Oligocene.
The question whether an implement-using animal, which nearly all
would agree to regard as in some degree human, wandered over what
is now the South of England (Kent, Essex, Dorsetshire, etc.) as
many hundred thousand years ago as this claim would imply, is
certainly one of great interest. But there would be little use in
discussing here the question of the "Eoliths," as these disputed
implements are called. A very keen controversy is still being
conducted in regard to them, and some of the highest authorities
in England, France, and Germany deny that they show any trace of
human workmanship or usage. Although they have the support of
such high authorities as Sir J. Prestwich, Sir E. Ray Lankester,
Lord Avebury, Dr. Keane, Dr. Blackmore, Professor Schwartz, etc.,
they are one of those controverted testimonies on which it would
be ill-advised to rely in such a work as this.
We must say, then, that we have no undisputed traces of man in
the Tertiary Era. The Tertiary implements which have been at
various times claimed in France, Italy, and Portugal are equally
disputed; the remains which were some years ago claimed as
Tertiary in the United States are generally disallowed; and the
recent claims from South America are under discussion. Yet it is
the general feeling of anthropologists that man was evolved in
the Tertiary Era. On the one hand, the anthropoid apes were
highly developed by the Miocene period, and it would be almost
incredible that the future human stock should linger hundreds of
thousands of years behind them. On the other hand, when we find
the first traces of man in the Pleistocene, this development has
already proceeded so far that its earlier phase evidently goes
back into the Tertiary. Let us pass beyond the Tertiary Era for a
moment, and examine the earliest and most primitive remains we
have of human or semi-human beings.
The first appearance of man in the chronicle of terrestrial life
is a matter of great importance and interest. Even the least
scientific of readers stands, so to say, on tiptoe to catch a
first glimpse of the earliest known representative of our race,
and half a century of discussion of evolution has engendered a
very wide interest in the early history of man.*
* A personal experience may not be without interest in this
connection. Among the many inquiries directed to me in regard to
evolution I received, in one month, a letter from a negro in
British Guiana and an extremely sensible query from an inmate of
an English asylum for the insane! The problem that beset the
latter of the two was whether the Lemuranda preceded the
Lemurogona in Eocene times. He had found a contradiction in the
statements of two scientific writers.
Fortunately, although these patriarchal bones are very
scanty--two teeth, a thigh-bone, and the skull-cap--we are now in
a position to form some idea of the nature of their living owner.
They have been subjected to so searching a scrutiny and
discussion since they were found in Java in 1891 and 1892 that
there is now a general agreement as to their nature. At first
some of the experts thought that they were the remains of an
abnormally low man, and others that they belonged to an
abnormally high ape. The majority held from the start that they
belonged to a member of a race almost midway between the highest
family of apes and the lowest known tribe of men, and therefore
fully merited the name of "Ape-Man" (Pithecanthropus). This is
now the general view of anthropologists.
The Ape-Man of Java was in every respect entitled to that name.
The teeth suggest a lower part of the face in which the teeth and
lips projected more than in the most ape-like types of Central
Africa. The skull-cap has very heavy ridges over the eyes and a
low receding forehead, far less human than in any previously
known prehistoric skull. The thigh-bone is very much heavier than
any known human femur of the same length, and so appreciably
curved that the owner was evidently in a condition of transition
from the semi-quadrupedal crouch of the ape to the erect attitude
of man. The Ape-Man, in other words, was a heavy, squat,
powerful, bestial-looking animal; of small stature, but above the
pygmy standard; erect in posture, but with clear traces of the
proneness of his ancestor; far removed from the highest ape in
brainpower, but almost equally far removed from the lowest savage
that is known to us. We shall see later that there is some recent
criticism, by weighty authorities, of the earlier statements in
regard to the brain of primitive man. This does not apply to the
Ape-Man of Java. The average cranial capacity (the amount of
brain-matter the skull may contain) of the chimpanzees, the
highest apes, is about 600 cubic centimetres. The average cranial
capacity of the lowest races of men, of moderate stature, is
about 1200. And the cranial capacity of Ape-Man was about 900
It is immaterial whether or no these bones belong to the same
individual. If they do not, we have remains of two or three
individuals of the same intermediate species. Nor does it matter
whether or no this early race is a direct ancestor of the later
races of men, or an extinct offshoot from the advancing human
stock. It is, in either case, an illustration of the intermediate
phase between the ape and man The more important tasks are to
trace the relationship of this early human stock to the apes, and
to discover the causes of its superior evolution.
The first question has a predominantly technical interest, and
the authorities are not agreed in replying to it. We saw that, on
the blood-test, man showed a very close relationship to the
anthropoid apes, a less close affinity to the Old World monkeys,
a more remote affinity to the American monkeys, and a very faint
and distant affinity to the femurs. A comparison of their
structures suggests the same conclusion. It is, therefore,
generally believed that the anthropoid apes and man had a common
ancestor in the early Miocene or Oligocene, that this group was
closely related to the ancestral group of the Old World monkeys,
and that all originally sprang from a primitive and generalised
femur-group. In other words, a branch of the earliest femur-like
forms diverges, before the specific femur-characters are fixed,
in the direction of the monkey; in this still vague and
patriarchal group a branch diverges, before the monkey-features
are fixed, in the direction of the anthropoids; and this group in
turn spreads into a number of types, some of which are the
extinct apes of the Miocene, four become the gorilla, chimpanzee,
orang, and gibbon of to-day, and one is the group that will
become man. To put it still more precisely, if we found a whole
series of remains of man's ancestors during the Tertiary, we
should probably class them, broadly, as femur-remains in the
Eocene, monkey-remains in the Oligocene, and ape-remains in the
Miocene. In that sense only man "descends from a monkey."
The far more important question is: How did this one particular
group of anthropoid animals of the Miocene come to surpass all
its cousins, and all the rest of the mammals, in
brain-development? Let us first rid the question of its supposed
elements of mystery and make of it a simple problem. Some imagine
that a sudden and mysterious rise in intelligence lifted the
progenitor of man above its fellows. The facts very quickly
dispel this illusion. We may at least assume that the ancestor of
man was on a level with the anthropoid ape in the Miocene period,
and we know from their skulls that the apes were as advanced then
as they are now. But from the early Miocene to the Pleistocene is
a stretch of about a million years on the very lowest estimate.
In other words, man occupied about a million years in travelling
from the level of the chimpanzee to a level below that of the
crudest savage ever discovered. If we set aside the Java man, as
a possible survivor of an earlier phase, we should still have to
say that, much more than a million years after his departure from
the chimpanzee level, man had merely advanced far enough to chip
stone implements; because we find no other trace whatever of
intelligence than this until near the close of the Palaeolithic
period. If there is any mystery, it is in the slowness of man's
development.
Let us further recollect that it is a common occurrence in the
calendar of life for a particular organ to be especially
developed in one member of a particular group more than in the
others. The trunk of the elephant, the neck of the giraffe, the
limbs of the horse or deer, the canines of the satire-toothed
tiger, the wings of the bat, the colouring of the tiger, the
horns of the deer, are so many examples in the mammal world
alone. The brain is a useful organ like any other, and it is easy
to conceive that the circumstances of one group may select it
just as the environment of another group may lead to the
selection of speed, weapons, or colouring. In fact, as we saw,
there was so great and general an evolution of brain in the
Tertiary Era that our modern mammals quite commonly have many
times the brain of their Tertiary ancestors. Can we suggest any
reasons why brain should be especially developed in the apes, and
more particularly still in the ancestors of man?
The Primate group generally is a race of tree-climbers. The
appearance of fruit on early Tertiary trees and the
multiplication of carnivores explain this. The Primate is, except
in a few robust cases, a particularly defenceless animal. When
its earliest ancestors came in contact with fruit and nut-bearing
trees, they developed climbing power and other means of defence
and offense were sacrificed. Keenness of scent and range of
hearing would now be of less moment, but sight would be
stimulated, especially when soft-footed climbing carnivores came
on the scene. There is, however, a much deeper significance in
the adoption of climbing, and we must borrow a page from the
modern physiology of the brain to understand it.
The stress laid in the modern education of young children on the
use of the hands is not merely due to a feeling that they should
handle objects as well as read about them. It is partly due to
the belief of many distinguished physiologists that the training
of the hands has a direct stimulating effect on the thought-
centres in the brain. The centre in the cerebrum which controls
the use of the hands is on the fringe of the region which seems
to be concerned in mental operations. For reasons which will
appear presently, we may add that the centres for controlling the
muscles of the face and head are in the same region. Any finer
training or the use of the hands will develop the centre for the
fore limbs, and, on the principles, may react on the more
important region of the cortex. Hence in turning the fore foot
into a hand, for climbing and grasping purposes, the primitive
Primate entered upon the path of brain-development. Even the
earliest Primates show large brains in comparison with the small
brains of their contemporaries.
It is a familiar fact in the animal world that when a certain
group enters upon a particular path of evolution, some members of
the group advance only a little way along it, some go farther,
and some outstrip all the others. The development of social life
among the bees will illustrate this. Hence we need not be puzzled
by the fact that the lemurs have remained at one mental level,
the monkeys at another, and the apes at a third. It is the common
experience of life; and it is especially clear among the various
races of men. A group becomes fitted to its environment, and, as
long as its surroundings do not change, it does not advance. A
related group, in a different environment, receives a particular
stimulation, and advances. If, moreover, a group remains
unstimulated for ages, it may become so rigid in its type that it
loses the capacity to advance. It is generally believed that the
lowest races of men, and even some of the higher races like the
Australian aboriginals, are in this condition. We may expect this
"unteachability" in a far more stubborn degree in the anthropoid
apes, which have been adapted to an unchanging environment for a
million years.
All that we need further suppose is--and it is one of the
commonest episodes in terrestrial life--that one branch of the
Miocene anthropoids, which were spread over a large part of the
earth, received some stimulus to change which its cousins did not
experience. It is sometimes suggested that social life was the
great advantage which led to the superior development of mind in
man. But such evidence as there is would lead us to suppose that
primitive man was solitary, not social. The anthropoid apes are
not social, but live in families, and are very unprogressive. On
the other hand, the earliest remains of prehistoric man give no
indication of social life. Fire-places, workshops, caves, etc.,
enter the story in a later phase. Some authorities on prehistoric
man hold very strongly that during the greater part of the Old
Stone Age (two-thirds, at least, of the human period) man
wandered only in the company of his mate and children.*
* The point will be more fully discussed later. This account of
prehistoric life is well seen in Mortillet's Prehistorique
(1900). The lowest races also have no tribal life, and Professor
Westermarck is of opinion that early man was not social.
We seem to have the most plausible explanation of the divergence
of man from his anthropoid cousins in the fact that he left the
trees of his and their ancestors. This theory has the advantage
of being a fact--for the Ape-Man race of Java has already left
the trees--and providing a strong ground for brain-advance. A
dozen reasons might be imagined for his quitting the
trees--migration, for instance, to a region in which food was
more abundant, and carnivores less formidable, on the
ground-level--but we will be content with the fact that he did.
Such a change would lead to a more consistent adoption of the
upright attitude, which is partly found in the anthropoid apes,
especially the gibbons. The fore limb would be no longer a
support of the body; the hand would be used more for grasping;
and the hand-centre in the brain would be proportionately
stimulated. The adoption of the erect attitude would further lead
to a special development of the muscles of the head and face, the
centre for which is in the same important region in the cortex.
There would also be a direct stimulation of the brain, as, having
neither weapons nor speed, the animal would rely all the more on
sight and mind. If we further suppose that this primitive being
extended the range of his hunting, from insects and small or dead
birds to small land-animals, the stimulation would be all the
greater. In a word, the very fact of a change from the trees to
the ground suggests a line of brain-development which may
plausibly be conceived, in the course of a million years, to
evolve an Ape-Man out of a man-like ape. And we are not
introducing any imaginary factor in this view of human origins.
The problem of the evolution of man is often approached in a
frame of mind not far removed from that of the educated, but
inexpert, European who stands before the lowly figure of the
chimpanzee, and wonders by what miracle the gulf between it and
himself was bridged. That is to lay a superfluous strain on the
imagination. The proper term of comparison is the lowest type of
human being known to us, since the higher types of living men
have confessedly evolved from the lower. But even the lowest type
of existing or recent savage is not the lowest level of humanity.
Whether or no the Tasmanian or the Yahgan is a primitive remnant
of the Old Stone Age, we have a far lower depth in the Java race.
What we have first to do is to explain the advance to that level,
in the course of many hundreds of thousands of years: a period
fully a hundred times as long as the whole history of
civilisation. Time itself is no factor in evolution, but in this
case it is a significant condition. It means that, on this view
of the evolution of man, we are merely assuming that an advance
in brain-development took place between the Miocene and the
Pleistocene, not similar to, but immeasurably less than, the
advance which we know to have been made in the last fifty
thousand years. In point of fact, the most mysterious feature of
the evolution of man was its slowness. We shall see that, to meet
the facts, we must suppose man to have made little or no progress
during most of this vast period, and then to have received some
new stimulation to develop. What it was we have now to inquire.
CHAPTER XIX. MAN AND THE GREAT ICE-AGE
In discussing the development of plants and animals during the
Tertiary Era we have already perceived the shadow of the
approaching Ice-Age. We found that in the course of the Tertiary
the types which were more sensitive to cold gradually receded
southward, and before its close Europe, Asia, and North America
presented a distinctly temperate aspect. This is but the penumbra
of the eclipse. When we pass the limits of the Tertiary Era, and
enter the Quaternary, the refrigeration steadily proceeds, and,
from temperate, the aspect of much of Europe and North America
becomes arctic. From six to eight million square miles of the
northern hemisphere are buried under fields of snow and ice, and
even in the southern regions smaller glacial sheets spread from
the foot of the higher ranges of mountains.
It is unnecessary to-day to explain at any length the evidences
by which geologists trace this enormous glaciation of the
northern hemisphere. There are a few works still in circulation
in which popular writers, relying on the obstinacy of a few older
geologists, speak lightly of the "nightmare" of the Ice-Age. But
the age has gone by in which it could seriously be suggested that
the boulders strewn along the east of Scotland--fragments of rock
whose home we must seek in Scandinavia--were brought by the
vikings as ballast for their ships. Even the more serious
controversy, whether the scratches and the boulders which we find
on the face of Northern Europe and America were due to floating
or land ice, is virtually settled. Several decades of research
have detected the unmistakable signs of glacial action over this
vast area of the northern hemisphere. Most of Europe north of the
Thames and the Danube, nearly all Canada and a very large part of
the United States, and a somewhat less expanse of Northern Asia,
bear to this day the deep scars of the thick, moving ice-sheets.
Exposed rock-surfaces are ground and scratched, beds of pebbles
are twisted and contorted hollows are scooped out, and
moraines--the rubbish-heaps of the glaciers--are found on every
side. There is now not the least doubt that, where the great
Deinosaurs had floundered in semi-tropical swamps, where the figs
and magnolias had later flourished, where the most industrious
and prosperous hives of men are found to-day, there was, in the
Pleistocene period, a country to which no parallel can be found
outside the polar circles to-day.
The great revolution begins with the gathering of snows on the
mountains. The Alps and Pyrenees had now, we saw, reached their
full stature, and the gathering snows on their summits began to
glide down toward the plains in rivers of ice. The Apennines (and
even the mountains of Corsica), the Balkans, Carpathians,
Caucasus, and Ural Mountains, shone in similar mantles of ice and
snow. The mountains of Wales, the north of England, Scotland, and
Scandinavia had even heavier burdens, and, as the period
advanced, their sluggish streams of ice poured slowly over the
plains. The trees struggled against the increasing cold in the
narrowing tracts of green; the animals died, migrated to the
south, or put on arctic coats. At length the ice-sheets of
Scandinavia met the spreading sheets from Scotland and Wales, and
crept over Russia and Germany, and an almost continuous mantle,
from which only a few large areas of arctic vegetation peeped
out, was thrown over the greater part of Europe. Ten thousand
feet thick where it left the hills of Norway and Sweden, several
thousand feet thick even in Scotland, the ice-sheet that resulted
from the fusion of the glaciers gradually thinned as it went
south, and ended in an irregular fringe across Central Europe.
The continent at that time stretched westward beyond the Hebrides
and some two hundred miles beyond Ireland. The ice-front followed
this curve, casting icebergs into the Atlantic, then probably
advanced up what is now the Bristol Channel, and ran across
England and Europe, in a broken line, from Bristol to Poland.
South of this line there were smaller ice-fields round the higher
mountains, north of it almost the whole country presented the
appearance that we find in Greenland to-day.
In North America the glaciation was even more extensive. About
four million square miles of the present temperate zone were
buried under ice and snow. From Greenland, Labrador, and the
higher Canadian mountains the glaciers poured south, until, in
the east, the mass of ice penetrated as far as the valley of the
Mississippi. The great lakes of North America are permanent
memorials of its Ice-Age, and over more than half the country we
trace the imprint and the relics of the sheet. South America,
Australia, Tasmania, and New Zealand had their glaciated areas.
North Asia was largely glaciated, but the range of the ice-sheet
is not yet determined in that continent.
This summary statement will convey some idea of the extraordinary
phase through which the earth passed in the early part of the
present geological era. But it must be added that a singular
circumstance prolonged the glacial regime in the northern
hemisphere. Modern geologists speak rather of a series of
successive ice-sheets than of one definite Ice-Age. Some, indeed,
speak of a series of Ice-Ages, but we need not discuss the verbal
question. It is now beyond question that the ice-sheet advanced
and retreated several times during the Glacial Epoch. The
American and some English geologists distinguished six
ice-sheets, with five intermediate periods of more temperate
climate. The German and many English and French geologists
distinguish four sheets and three interglacial epochs. The exact
number does not concern us, but the repeated spread of the ice is
a point of some importance. The various sheets differed
considerably in extent. The wide range of the ice which I have
described represents the greatest extension of the glaciation,
and probably corresponds to the second or third of the six
advances in Dr. Geikie's (and the American) classification.
Before we consider the biological effect of this great of
refrigeration of the globe, we must endeavour to understand the
occurrence itself. Here we enter a world of controversy, but a
few suggestions at least may be gathered from the large
literature of the subject, which dispel much of the mystery of
the Great Ice-Age.
It was at one time customary to look out beyond the earth itself
for the ultimate causes of this glaciation. Imagine the sheet of
ice, which now spreads widely round the North Pole, shifted to
another position on the surface of the planet, and you have a
simple explanation of the occurrence. In other words, if we
suppose that the axis of the earth does not consistently point in
one direction-- that the great ball does not always present the
same average angle in relation to the sun--the poles will not
always be where they are at present, and the Pleistocene Ice-Age
may represent a time when the north pole was in the latitude of
North Europe and North America. This opinion had to be abandoned.
We have no trace whatever of such a constant shifting of the
polar regions as it supposes, and, especially, we have no trace
that the warm zone correspondingly shifted in the Pleistocene.
A much more elaborate theory was advanced by Dr. Croll, and is
still entertained by many. The path of the earth round the sun is
not circular, but elliptical, and there are times when the
gravitational pull of the other planets increases the
eccentricity of the orbit. It was assumed that there are periods
of great length, separated from each other by still longer
periods, when this eccentricity of the orbit is greatly
exaggerated. The effect would be to prolong the winter and
shorten the summer of each hemisphere in turn. The total amount
of heat received would not alter, but there would be a long
winter with less heat per hour, and a short summer with more
heat. The short summer would not suffice to melt the enormous
winter accumulations of ice and snow, and an ice-age would
result. To this theory, again, it is objected that we do not find
the regular succession of ice-ages in the story of the earth
which the theory demands, and that there is no evidence of an
alternation of the ice between the northern and southern
hemispheres.
More recent writers have appealed to the sun itself, and supposed
that some prolonged veiling of its photosphere greatly reduced
the amount of heat emitted by it. More recently still it has been
suggested that an accumulation of cosmic or meteoric dust in our
atmosphere, or between us and the sun, had, for a prolonged
period, the effect of a colossal "fire-screen." Neither of these
suppositions would explain the localisation of the ice. In any
case we need not have recourse to purely speculative accidents in
the world beyond until it is clear that there were no changes in
the earth itself which afford some explanation.
This is by no means clear. Some writers appeal to changes in the
ocean currents. It is certain that a change in the course of the
cold and warm currents of the ocean to-day might cause very
extensive changes of climate, but there seems to be some
confusion of ideas in suggesting that this might have had an
equal, or even greater, influence in former times. Our ocean
currents differ so much in temperature because the earth is now
divided into very pronounced zones of climate. These zones did
not exist before the Pliocene period, and it is not at all clear
that any redistribution of currents in earlier times could have
had such remarkable consequences. The same difficulty applies to
wind-currents.
On the other hand, we have already, in discussing the Permian
glaciation, discovered two agencies which are very effective in
lowering the temperature of the earth. One is the rise of the
land; the other is the thinning of the atmosphere. These are
closely related agencies, and we found them acting in conjunction
to bring about the Permian Ice-Age. Do we find them at work in
the Pleistocene?
It is not disputed that there was a very considerable upheaval of
the land, especially in Europe and North America, at the end of
the Tertiary Era. Every mountain chain advanced, and our Alps,
Pyrenees, Himalaya, etc., attained, for the first time, their
present, or an even greater elevation. The most critical
geologists admit that Europe, as a whole, rose 4000 feet above
its earlier level. Such an elevation would be bound to involve a
great lowering of the temperature. The geniality of the Oligocene
period was due, like that of the earlier warm periods, to the
low-lying land and very extensive water-surface. These conditions
were revolutionised before the end of the Tertiary. Great
mountains towered into the snow-line, and vast areas were
elevated which had formerly been sea or swamp.
This rise of the land involved a great decrease in the proportion
of moisture in the atmosphere. The sea surface was enormously
lessened, and the mountains would now condense the moisture into
snow or cloud to a vastly greater extent than had ever been known
before There would also be a more active circulation of the
atmosphere, the moist warm winds rushing upward towards the
colder elevations and parting with their vapour. As the
proportion of moisture in the atmosphere lessened the
surface-heat would escape more freely into space, the general
temperature would fall, and the evaporation--or production of
moisture would be checked, while the condensation would continue.
The prolonging of such conditions during a geological period can
be understood to have caused the accumulation of fields of snow
and ice in the higher regions. It seems further probable that
these conditions would lead to a very considerable formation of
fog and cloud, and under this protecting canopy the glaciers
would creep further down toward the plains.
We have then to consider the possibility of a reduction of the
quantity of carbon-dioxide in the atmosphere The inexpert reader
probably has a very exaggerated idea of the fall in temperature
that would be required to give Europe an Ice-Age. If our average
temperature fell about 5-8 degrees C. below the average
temperature of our time it would suffice; and it is further
calculated that if the quantity of carbon-dioxide in our
atmosphere were reduced by half, we should have this required
fall in temperature. So great a reduction would not be necessary
in view of the other refrigerating agencies. Now it is quite
certain that the proportion of carbon-dioxide was greatly reduced
in the Pleistocene. The forests of the Tertiary Era would
steadily reduce it, but the extensive upheaval of the land at its
close would be even more important. The newly exposed surfaces
would absorb great quantities of carbon. The ocean, also, as it
became colder, would absorb larger and larger quantities of
carbon-dioxide. Thus the Pleistocene atmosphere, gradually
relieved of its vapours and carbon-dioxide, would no longer
retain the heat at the surface. We may add that the growth of
reflective surfaces--ice, snow, cloud, etc.--would further lessen
the amount of heat received from the sun.
Here, then, we have a series of closely related causes and
effects which would go far toward explaining, if they do not
wholly suffice to explain, the general fall of the earth's
temperature. The basic cause is the upheaval of the land--a fact
which is beyond controversy, the other agencies are very plain
and recognisable consequences of the upheaval. There are,
however, many geologists who do not think this explanation
adequate.
It is pointed out, in the first place, that the glaciation seems
to have come long after the elevation. The difficulty does not
seem to be insurmountable. The reduction of the atmospheric
vapour would be a gradual process, beginning with the later part
of the elevation and culminating long afterwards. The reduction
of the carbon-dioxide would be even more gradual. It is
impossible to say how long it would take these processes to reach
a very effective stage, but it is equally impossible to show that
the interval between the upheaval and the glaciation is greater
than the theory demands.
It is also said that we cannot on these principles understand the
repeated advance and retreat of the ice-sheet.
This objection, again, seems to fail. It is an established fact
that the land sank very considerably during the Ice-Age, and has
risen again since the ice disappeared. We find that the crust in
places sank so low that an arctic ocean bathed the slopes of some
of the Welsh mountains; and American geologists say that their
land has risen in places from 2000 to 3000 feet (Chamberlin)
since the burden of ice was lifted from it. Here we have the
possibility of an explanation of the advances and retreats of the
glaciers. The refrigerating agencies would proceed until an
enormous burden of ice was laid on the land of the northern
hemisphere. The land apparently sank under the burden, the ice
and snow melted at the lower level and there was a temperate
interglacial period. But the land, relieved of its burden, rose
once more, the exposed surface absorbed further quantities of
carbon, and a fresh period of refrigeration opened. This
oscillation might continue until the two sets of opposing forces
were adjusted, and the crust reached a condition of comparative
stability.
Finally, and this is the more serious difficulty, it is said that
we cannot in this way explain the localisation of the glacial
sheets. Why should Europe and North America in particular suffer
so markedly from a general thinning of the atmosphere? The
simplest answer is to suggest that they especially shared the
rise of the land. Geology is not in a position either to prove or
disprove this, and it remains only a speculative interpretation
of the fact We know at least that there was a great uprise of
land in Europe and North America in the Pliocene and Pleistocene
and may leave the precise determination of the point to a later
age. At the same time other local causes are not excluded. There
may have been a large extension of the area of atmospheric
depression which we have in the region of Greenland to-day.
When we turn to the question of chronology we have the same acute
difference of opinion as we have found in regard to all questions
of geological time. It used to be urged, on astronomical grounds,
that the Ice-Age began about 240,000 years ago, and ended about
60,000 years ago, but the astronomical theory is, as I said,
generally abandoned. Geologists, on the other hand, find it
difficult to give even approximate figures. Reviewing the various
methods of calculation, Professor Chamberlin concludes that the
time of the first spread of the ice-sheet is quite unknown, the
second and greatest extension of the glaciation may have been
between 300,000 and a million years ago, and the last
ice-extension from 20,000 to 60,000 years ago; but he himself
attaches "very little value" to the figures. The chief ice-age
was some hundreds of thousands of years ago, that is all we can
say with any confidence.
In dismissing the question of climate, however, we should note
that a very serious problem remains unsolved. As far as present
evidence goes we seem to be free to hold that the ice-ages which
have at long intervals invaded the chronicle of the earth were
due to rises of the land. Upheaval is the one constant and
clearly recognisable feature associated with, or preceding,
ice-ages. We saw this in the case of the Cambrian, Permian,
Eocene, and Pleistocene periods of cold, and may add that there
are traces of a rise of mountains before the glaciation of which
we find traces in the middle of the Archaean Era. There are
problems still to be solved in connection with each of these very
important ages, but in the rise of the land and consequent
thinning of the atmosphere we seem to have a general clue to
their occurrence. Apart from these special periods of cold,
however, we have seen that there has been, in recent geological
times, a progressive cooling of the earth, which we have not
explained. Winter seems now to be a permanent feature of the
earth's life, and polar caps are another recent, and apparently
permanent, acquisition. I find no plausible reason assigned for
this.
The suggestion that the disk of the sun is appreciably smaller
since Tertiary days is absurd; and the idea that the earth has
only recently ceased to allow its internal heat to leak through
the crust is hardly more plausible. The cause remains to be
discovered.
We turn now to consider the effect of the great Ice-Age, and the
relation of man to it. The Permian revolution, to which the
Pleistocene Ice-Age comes nearest in importance, wrought such
devastation that the overwhelming majority of living things
perished. Do we find a similar destruction of life, and selection
of higher types, after the Pleistocene perturbation? In
particular, had it any appreciable effect upon the human species?
A full description of the effect of the great Ice-Age would
occupy a volume. The modern landscape in Europe and North America
was very largely carved and modelled by the ice-sheet and the
floods that ensued upon its melting. Hills were rounded, valleys
carved, lakes formed, gravels and soils distributed, as we find
them to-day. In its vegetal aspect, also, as we saw, the modern
landscape was determined by the Pleistocene revolution. A great
scythe slowly passed over the land. When the ice and snow had
ended, and the trees and flowers, crowded in the southern area,
slowly spread once more over the virgin soil, it was only the
temperate species that could pass the zone guarded by the Alps
and the Pyrenees. On the Alps themselves the Pleistocene
population still lingers, their successful adaptation to the cold
now preventing them from descending to the plains.
The animal world in turn was winnowed by the Pleistocene episode.
The hippopotamus, crocodile, turtle, flamingo, and other
warm-loving animals were banished to the warm zone. The mammoth
and the rhinoceros met the cold by developing woolly coats, but
the disappearance of the ice, which had tempted them to this
departure, seems to have ended their fitness. Other animals which
became adapted to the cold--arctic bears, foxes, seals,
etc.--have retreated north with the ice, as the sheet melted. For
hundreds of thousands of years Europe and North America, with
their alternating glacial and interglacial periods, witnessed
extraordinary changes and minglings of their animal population.
At one time the reindeer, the mammoth, and the glutton penetrate
down to the Mediterranean, in the next phase the elephant and
hippopotamus again advance nearly to Central Europe. It is
impossible here to attempt to unravel these successive changes
and migrations. Great numbers of species were destroyed, and at
length, when the climatic condition of the earth reached a state
of comparative stability, the surviving animals settled in the
geographical regions in which we find them to-day.
The only question into which we may enter with any fullness is
that of the relation of human development to this grave
perturbation of the condition of the globe. The problem is
sometimes wrongly conceived. The chief point to be determined is
not whether man did or did not precede the Ice-Age. As it is the
general belief that he was evolved in the Tertiary, it is clear
that he existed in some part of the earth before the Ice-Age.
Whether he had already penetrated as far north as Britain and
Belgium is an interesting point, but not one of great importance.
We may, therefore, refrain from discussing at any length those
disputed crude stone implements (Eoliths) which, in the opinion
of many, prove his presence in northern regions before the close
of the Tertiary. We may also now disregard the remains of the
Java Ape-Man. There are authorities, such as Deniker, who hold
that even the latest research shows these remains to be Pliocene,
but it is disputed. The Java race may be a surviving remnant of
an earlier phase of human evolution.
The most interesting subject for inquiry is the fortune of our
human and prehuman forerunners during the Pliocene and
Pleistocene periods. It may seem that if we set aside the
disputable evidence of the Eoliths and the Java remains we can
say nothing whatever on this subject. In reality a fact of very
great interest can be established. It can be shown that the
progress made during this enormous lapse of time--at least a
million years--was remarkably slow. Instead of supposing that
some extraordinary evolution took place in that conveniently
obscure past, to which we can find no parallel within known
times, it is precisely the reverse. The advance that has taken
place within the historical period is far greater, comparatively
to the span of time, than that which took place in the past.
To make this interesting fact clearer we must attempt to measure
the progress made in the Pliocene and Pleistocene. We may assume
that the precursor of man had arrived at the anthropoid-ape level
by the middle of the Miocene period. He is not at all likely to
have been behind the anthropoid apes, and we saw that they were
well developed in the mid-Tertiary. Now we have a good knowledge
of man as he was in the later stage of the Ice-Age--at least a
million years later--and may thus institute a useful comparison
and form some idea of the advance made.
In the later stages of the Pleistocene a race of men lived in
Europe of whom we have a number of skulls and skeletons, besides
vast numbers of stone implements. It is usually known as the
Neanderthal race, as the first skeleton was found, in 1856, at
Neanderthal, near Dusseldorf. Further skeletons were found at
Spy, in Belgium, and Krapina, in Croatia. A skull formerly found
at Gibraltar is now assigned to the same race. In the last five
years a jaw of the same (or an earlier) age has been found at
Mauer, near Heidelberg, and several skeletons have been found in
France (La Vezere and Chapelle-aux-Saints). From these, and a few
earlier fragments, we have a confident knowledge of the features
of this early human race.
The highest appreciation of the Neanderthal man--a somewhat
flattering appreciation, as we shall see--is that he had reached
the level of the Australian black of to-day. The massive frontal
ridges over his eyes, the very low, retreating forehead, the
throwing of the mass of the brain toward the back of the head,
the outthrust of the teeth and jaws, and the complete absence (in
some cases) or very slight development of the chin, combine to
give the head what the leading authorities call a "bestial" or
"simian" aspect. The frame is heavy, powerful, and of moderate
height (usually from two to four inches over five feet). The
thigh-bones are much more curved than in modern man. We cannot
enter here into finer anatomical details, but all the features
are consistent and indicate a stage in the evolution from ape-man
to savage man.
One point only calls for closer inquiry. Until a year or two ago
it was customary to state that in cranial capacity also--that is
to say, in the volume of brain-matter that the skull might
contain--the Neanderthal race was intermediate between the
Ape-Man and modern man. We saw above that the cranial capacity of
the highest ape is about 600 cubic centimetres, and that of the
Ape-Man (variously given as 850 and 950) is about 900. It was
then added that the capacity of the Neanderthal race was about
1200, and that of civilised man (on the average) 1600. This
seemed to be an effective and convincing indication of evolution,
but recent writers have seriously criticised it. Sir Edwin Ray
Lankester, Professor Sollas, and Dr. Keith have claimed in recent
publications that the brain of Neanderthal man was as large as,
if not larger than, that of modern man.* Professor Sollas even
observes that "the brain increases in volume as we go backward."
This is, apparently, so serious a reversal of the familiar
statement in regard to the evolution of man that we must consider
it carefully.
*See especially an address by Professor Sollas in the Quarterly
Journal of the Geological Society, Vol. LXVI. (1910).
Largeness of brain in an individual is no indication of
intelligence, and smallness of brain no proof of low mentality.
Some of the greatest thinkers, such as Aristotle and Leibnitz,
had abnormally small heads. Further, the size of the brain is of
no significance whatever except in strict relation to the size
and weight of the body. Woman has five or six ounces less
brain-matter than man, but in proportion to her average size and
the weight of the vital tissue of her body (excluding fat) she
has as respectable a brain as man. When, however, these
allowances have been made, it has usually been considered that
the average brain of a race is in proportion to its average
intelligence. This is not strictly true. The rabbit has a larger
proportion of brain to body than the elephant or horse, and the
canary a larger proportion than the chimpanzee. Professor Sollas
says that the average cranial capacity of the Eskimo is 1546
cubic centimetres, or nearly that assigned to the average
Parisian.
Clearly the question is very complex, and some of these recent
authorities conclude that the cranial capacity, or volume of the
brain, has no relation to intelligence, and therefore the size of
the Neanderthal skull neither confirms nor disturbs the theory of
evolution. The wise man will suspend his judgment until the whole
question has been fully reconsidered. But I would point out that
some of the recent criticisms are exaggerated. The Gibraltar
skull is estimated by Professor Sollas himself to have a capacity
of about 1260; and his conclusion that it is an abnormal or
feminine skull rests on no positive grounds. The
Chapelle-aux-Saints skull ALONE is proved to have the high
capacity of 1620; and it is as yet not much more than a
supposition that the earlier skulls had been wrongly measured.
But, further, the great French authority, M. Boule, who measured
the capacity of the Chapelle-aux Saints skull, observes* that
"the anomaly disappears" on careful study. He assures us that a
modern skull of the same dimensions would have a capacity of
1800-1900 cubic centimetres, and warns us that we must take into
account the robustness of the body of primitive man. He concludes
that the real volume of the Neanderthal brain (in this highest
known specimen) is "slight in comparison with the volume of the
brain lodged in the large heads of to-day," and that the "bestial
or ape-like characters" of the race are not neutralised by this
gross measurement.
*See his article in Anthropologie, Vol. XX. (1909), p. 257. As
Professor Sollas mainly relies on Boule, it is important to see
that there is a very great difference between the two.
We must therefore hesitate to accept the statement that primitive
man had as large a brain, if not a larger brain, than a modern
race. The basis is slender, and the proportion of brain to
body-tissue has not been taken into account. On the other hand,
the remains of this early race are, Professor Sollas says,
"obviously more brutal than existing men in all the other
ascertainable characters by which they differ from them." Nor are
we confined to precarious measurements of skulls. We have the
remains of the culture of this early race, and in them we have a
surer trace of its mental development.
Here again we must proceed with caution, and set aside confused
and exaggerated statements. Some refer us to the artistic work of
primitive man. We will consider his drawings and carvings
presently, but they belong to a later race, not the Neanderthal
race. Some lay stress on the fact, apparently indicated in one or
two cases out of a dozen, that primitive man buried his dead.
Professor Sollas says that it indicates that even Neanderthal man
had reached "a comparatively high stage in the evolution of
religious ideas "; but the Australians bury their dead, and the
highest authorities are not agreed whether they have any idea
whatever of a supreme being or of morality. We must also disallow
appeals to the use of fire, the taming of animals, pottery, or
clothing. None of these things are clearly found in conjunction
with the Neanderthal race.
The only certain relic of Neanderthal culture is the implement
which the primitive savage fashioned, by chipping or pressure, of
flint or other hard stone. The fineness of some of these
implements is no indication of great intelligence. The
Neanderthal man inherited a stone culture which was already of
great antiquity. At least one, if not two or three, prolonged
phases of the Old Stone Age were already over when he appeared.
On the most modest estimate men had by that time been chipping
flints for several hundred thousand years, and it is no argument
of general intelligence that some skill in the one industry of
the age had been developed. The true measure of Neanderthal man's
capacity is that, a million years or so after passing the
anthropoid-age level, he chipped his stones more finely and gave
them a better edge and contour. There is no evidence that he as
yet hefted them. It is flattering to him to compare him with the
Australian aboriginal. The native art, the shields and spears and
boomerangs, and the elaborate tribal and matrimonial arrangements
of the Australian black are not known to have had any counterpart
in his life.
It would therefore seem that the precursors of man made
singularly little, if any, progress during the vast span of time
between the Miocene and the Ice-Age, and that then something
occurred which quickened the face of human evolution. From the
Neanderthal level man will advance to the height of modern
civilisation in about one-tenth the time that it took him to
advance from the level of the higher ape to that of the lowest
savage. Something has broken into the long lethargy of his
primitive career, and set him upon a progressive path. Let us see
if a careful review of the stages of his culture confirms the
natural supposition that this "something" was the fall in the
earth's temperature, and how it may have affected him.
CHAPTER XX. THE DAWN OF CIVILISATION
The story of man before the discovery of metal and the attainment
of civilisation is notoriously divided into a Palaeolithic (Old
Stone) Age, and a Neolithic (New Stone) Age. Each of these ages
is now subdivided into stages, which we will review in
succession. But it is important to conceive the whole story of
man in more correct proportion than this familiar division
suggests. The historical or civilised period is now computed at
about ten thousand years. The Neolithic Age, which preceded
civilisation, is usually believed to be about four or five times
as long, though estimates of its duration vary from about twenty
to a hundred thousand years. The Palaeolithic Age in turn is
regarded as at least three or four times as long as the
Neolithic; estimates of time vary from a hundred to five hundred
thousand years. And before this there is the vast stretch of time
in which the ape slowly became a primitive human.
This long, early period is, as we saw, still wrapped in mist and
controversy. A few bones tell of a race living, in semi-human
shape, in the region of the Indian Ocean; a few crude stones are
held by many to indicate that a more advanced, but very lowly
race, wandered over the south of Europe and north of Africa
before the Ice-Age set in. The starting-point or cradle of the
race is not known. The old idea of seeking the patriarchal home
on the plains to the north of India is abandoned, and there is
some tendency to locate it in the land which has partly survived
in the islands of the Indian Ocean. The finding of early remains
in Java is not enough to justify that conclusion, but it obtains
a certain probability when we notice the geographical
distribution of the Primates. The femurs and the apes are found
to-day in Africa and Asia alone; the monkeys have spread eastward
to America and westward to Europe and Africa; the human race has
spread north-eastward into Asia and America, northwestward into
Europe, westward into Africa, and southward to Australia and the
islands. This distribution suggests a centre in the Indian Ocean,
where there was much more land in the Tertiary Era than there is
now. We await further exploration in that region and Africa.
There is nothing improbable in the supposition that man wandered
into Europe in the Tertiary, and has left in the Eoliths the
memorials of his lowly condition. The anthropoid apes certainly
reached France. However that may be, the Ice-Age would restrict
all the Primates to the south. It will be seen, on a glance at
the map, that a line of ice-clad mountains would set a stern
barrier to man's advance in the early Pleistocene, from the
Pyrenees to the Himalaya, if not to the Pacific. He therefore
spread westward and southward. One branch wandered into
Australia, and was afterwards pressed by more advanced invaders
(the present blacks of Australia) into Tasmania, which seems to
have been still connected by land. Another branch, or branches,
spread into Africa, to be driven southward, or into the central
forests, by later and better equipped invaders. They survive,
little changed (except by recent contact with Europeans), in the
Bushmen and in large populations of Central Africa which are
below the level of tribal organisation. Others remained in the
islands, and we seem to have remnants of them in the Kalangs,
Veddahs, etc. But these islands have been repeatedly overrun by
higher races, and the primitive life has been modified.
Comparing the most isolated of these relics of early humanity, we
obtain many suggestions about the life of that remote age. The
aboriginal Tasmanians, who died out about forty years ago, were
of great evolutionary interest. It is sometimes said that man is
distinguished from all other animals by the possession of
abstract ideas, but the very imperfect speech of the Tasmanians
expressed no abstract ideas. Their mind seems to have been in an
intermediate stage of development. They never made fire, and,
like the other surviving fragments of early humanity, they had no
tribal organisation, and no ideas of religion or morality.
The first effect of the Ice-Age on this primitive humanity would
be to lead to a beginning of the development of racial
characters. The pigment under the skin of the negro is a
protection against the actinic rays of the tropical sun; the
white man, with his fair hair and eyes, is a bleached product of
the northern regions; and the yellow or brown skin seems to be
the outcome of living in dry regions with great extremes of
temperature. As the northern hemisphere divided into climatic
zones these physical characters were bound to develop. The men
who went southward developed, especially when fully exposed to
the sun on open plains, the layer of black pigment which marks
the negroid type. There is good reason, as we shall see to think
that man did not yet wear clothing, though he had a fairly
conspicuous, if dwindling, coat of hair. On the other hand the
men who lingered further north, in South-western Asia and North
Africa, would lose what pigment they had, and develop the lighter
characters of the northerner. It has been noticed that even a
year in the arctic circle has a tendency to make the eyes of
explorers light blue. We may look for the genesis of the
vigorous, light-complexioned races along the fringe of the great
ice-sheet. It must be remembered that when the limit of the
ice-sheet was in Central Germany and Belgium, the climate even of
North Africa would be very much more temperate than it is to-day.
As the ice-sheet melted, the men who were adapted to living in
the temperate zone to the south of it penetrated into Europe, and
the long story of the Old Stone Age opened. It must not, of
course, be supposed that this stage of human culture only began
with the invasion of Europe. Men would bring their rough art of
fashioning implements with them, but the southern regions are too
little explored to inform us of the earlier stage. But as man
enters Europe he begins to drop his flints on a soil that we have
constant occasion to probe--although the floor on which he trod
is now sometimes forty or fifty feet below the surface--and we
obtain a surer glimpse of the fortunes of our race.
Most European geologists count four distinct extensions of the
ice-sheet, with three interglacial periods. It is now generally
believed that man came north in the third interglacial period;
though some high authorities think that he came in the second. As
far as England is concerned, it has been determined, under the
auspices of the British Association, that our oldest implements
(apart from the Eoliths) are later than the great ice-sheet, but
there is some evidence that they precede the last extension of
the ice.
Two stages are distinguished in this first part of the
Palaeolithic Age--the Acheulean and Chellean--but it will suffice
for our purpose to take the two together as the earlier and
longer section of the Old Stone Age. It was a time of temperate,
if not genial, climate. The elephant (an extinct type), the
rhinoceros, the hippopotamus, the hyaena, and many other forms of
animal life that have since retired southward, were neighbours of
the first human inhabitant of Europe. Unfortunately, we have only
one bone of this primitive race, the jaw found at Mauer in 1907,
but its massive size and chinless contour suggest a being midway
between the Java man and the Neanderthal race. His culture
confirms the supposition. There is at this stage no clear trace
of fire, clothing, arrows, hefted weapons, spears, or social
life. As the implements are generally found on old river-banks or
the open soil, not in caves, we seem to see a squat and powerful
race wandering, homeless and unclad, by the streams and broad,
marshy rivers of the time. The Thames and the Seine had not yet
scooped out the valleys on the slopes of which London and Paris
are built.
This period seems, from the vast number of stone implements
referred to it, to have lasted a considerable time. There is a
risk in venturing to give figures, but it may be said that few
authorities would estimate it at less than a hundred thousand
years. Man still advanced with very slow and uncertain steps, his
whole progress in that vast period being measured by the
invention of one or two new forms of stone implements and a
little more skill in chipping them. At its close a great chill
comes over Europe--the last ice-sheet is, it seems, spreading
southward--and we enter the Mousterian period and encounter the
Neanderthal race which we described in the preceding chapter.
It must be borne in mind that the whole culture of primitive
times is crushed into a few feet of earth. The anthropologist is
therefore quite unable to show us the real succession of human
stages, and has to be content with a division of the whole long
and gradual evolution into a few well-marked phases. These
phases, however, shade into each other, and are merely convenient
measurements of a continuous story. The Chellean man has slowly
advanced to a high level. There is no sudden incoming of a higher
culture or higher type of man. The most impressive relics of the
Mousterian period, which represent its later epoch, are merely
finely chipped implements. There is no art as yet, no pottery,
and no agriculture; and there is no clear trace of the use of
fire or clothing, though we should bc disposed to put these
inventions in the chilly and damp Mousterian period. There is
therefore no ground for resenting the description, "the primeval
savage," which has been applied to early man. The human race is
already old, yet, as we saw, it is hardly up to the level of the
Australian black. The skeleton found at Chapelle-aux-Saints is
regarded as the highest known type of the race, yet the greatest
authority on it, M. Boule, says emphatically: "In no actual race
do we find the characters of inferiority--that is to say, the
ape-like features--which we find in the Chapelle-aux-Saints
head." The largeness of the head is in proportion to the robust
frame, but in its specifically human part--the front--it is very
low and bestial; while the heavy ridges over the large eyes, the
large flat stumpy nose, the thick bulge of the lips and teeth,
and the almost chinless jaw, show that the traces of his ancestry
cling close to man after some hundreds of thousands of years of
development.
The cold increases as we pass to the last part of the Old Stone
Age, the Solutrean and Magdalenian periods; and nothing is
clearer than that the pace of development increases at the same
time. Short as the period is, in comparison with the preceding,
it witnesses a far greater advance than had been made in all the
rest of the Old Stone Age. Beyond a doubt men now live in caves,
in large social groups, make clothing from the skins of animals,
have the use of fire, and greatly improve the quality of their
stone axes, scrapers, knives, and lance-heads. There is at last
some promise of the civilisation that is coming. In the soil of
the caverns in which man lived, especially in Southern France and
the Pyrenean region, we find the debris of a much larger and
fuller life. Even the fine bone needles with which primitive man
sewed his skin garments, probably with sinews for thread, survive
in scores. In other places we find the ashes of the fires round
which he squatted, often associated with the bones of the wild
horses, deer, etc., on which he lived.
But the most remarkable indication of progress in the "cave-man"
is his artistic skill. Exaggerated conclusions are sometimes
drawn from the statuettes, carvings, and drawings which we find
among the remains of Magdalenian life. Most of them are crude,
and have the limitations of a rustic or a child artist. There is
no perspective, no grouping. Animals are jumbled together, and
often left unfinished because the available space was not
measured. There are, however, some drawings--cut on bone or horn
or stone with a flint implement--which evince great skill in
line-drawing and, in a few cases, in composition. Some of the
caves also are more or less frescoed; the outlines of animals,
sometimes of life-size and in great numbers, are cut in the wall,
and often filled in with pigment. This skill does not imply any
greater general intelligence than the rest of the culture
exhibits. It implies persistent and traditional concentration
upon the new artistic life. The men who drew the "reindeer of
Thayngen" and carved the remarkable statuettes of women in ivory
or stone, were ignorant of the simplest rudiments of pottery or
agriculture, which many savage tribes possess.
Some writers compare them with the Eskimo of to-day, and even
suggest that the Eskimo are the survivors of the race, retreating
northward with the last ice-sheet, and possibly egged onward by a
superior race from the south. It is, perhaps, not a very
extravagant claim that some hundreds of thousands of years of
development--we are now only a few tens of thousands of years
from the dawn of civilisation--had lifted man to the level of the
Eskimo, yet one must hesitate to admit the comparison. Lord
Avebury reproduces an Eskimo drawing, or picture-message, in his
"Prehistoric Times," to which it would be difficult to find a
parallel in Magdalenian remains. I do not mean that the art is
superior, but the complex life represented on the
picture-message, and the intelligence with which it is
represented, are beyond anything that we know of Palaeolithic
man. I may add that nearly all the drawings and statues of men
and women which the Palaeolithic artist has left us are marked by
the intense sexual exaggeration--the "obscenity," in modern
phraseology--which we are apt to find in coarse savages.
Three races are traced in this period. One, identified by
skeletons found at Mentone and by certain statuettes, was negroid
in character. Probably there was an occasional immigration from
Africa. Another race (Cro-Magnon) was very tall, and seems to
represent an invasion from some other part of the earth toward
the close of the Old Stone Age. The third race, which is compared
to the Eskimo, and had a stature of about five feet, seem to be
the real continuers of the Palaeolithic man of Europe. Curiously
enough, we have less authentic remains of this race than of its
predecessor, and can only say that, as we should expect, the
ape-like features--the low forehead, the heavy frontal ridges,
the bulging teeth, etc.--are moderating. The needles we have
found--round, polished, and pierced splinters of bone, sometimes
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