arboreal, the gorilla being the least so, probably on account of its
weight. Though they all descend at times to the ground, their awkward
motion on the surface shows them to be out of their element, while they
move with ease and rapidity in the trees. The organization of man
renders it questionable if his primeval ancestor was arboreal to any
similar extent. The indications would seem to be that it made the ground
its habitual place of residence at an early period in its history, and
that the result of this new habit and of its erect attitude was a change
in the relative length of its limbs.
That this animal dwelt mainly in trees in the first stage of its
existence, and possessed a powerful grasping power in its hands, we have
corroborative evidence in recent studies of child life. The human
infant, in its earliest days of life, displays a remarkable grasping
power, being able to sustain its weight with its hands for a number of
seconds, or a minute or more, at an age when its other muscles are
flabby and powerless. It appears in this to repeat a habit normal to the
ancestral infant, an instinct developed to prevent a fall from its home
among the boughs.
Yet it is doubtful if the man-ape long remained a specially arboreal
animal. The varied length of arm in the anthropoid apes was doubtless of
early origin, and in all probability man's ancestor had originally a
shorter arm than its related species. If so, this must have rendered it
less agile in trees than other forms. If we could see this ancient
creature in its arboreal home, we should probably find it more inclined
to stand erect than the other apes, walking on a lower limb, and
steadying itself by grasping an upper limb. This would be a more natural
and easy mode of progression to a short-armed animal than the crouching
attitude of the orang or the swinging motion of the gibbon, and its
effect would be to make the erect attitude to a large extent habitual
with this animal.
In short, man's ancestor may have become in considerable measure a biped
while still largely a dweller in the trees, and to that degree set its
arms free for other duties than that of locomotion. Like the other apes,
it probably often descended to the ground, where its habit of walking
erect on the boughs rendered the biped walk an easy one, or where this
habit may have been originally acquired. While this is conjectural, it
is supported by facts of organization and existing habit, and for the
reasons given it seems highly probable that the ancestor of man took to
a land residence at an early period in its history, climbing again for
food or safety, but dwelling more and more habitually on the earth's
surface. Even at this remote era it may have become essentially human in
organization, its subsequent changes being mainly in brain development,
and only to a minor extent in physical form and structure.
Fossil apes have not been found farther back than the Miocene Age of
geology. It is quite probable, however, that they may yet be found in
Eocene strata, since examples of their highest representatives, the
anthropoid or manlike apes, have been found in Miocene rocks. The fact
that these large apes are now few in number of species, is no proof that
many forms of them may not have formerly existed, and among these we may
class the ancestor of man.
V
THE FREEDOM OF THE ARMS
Man's ancestor is by no means the only form of ape that has made the
earth's surface its place of residence. The baboon is one example of a
number of forms that dwell habitually upon the ground, though they have
not lost their agility in climbing. But these species have returned to
the quadruped habit, to which the equal length of their limbs adapts
them. All the anthropoid apes dwell to some extent upon the ground, but
these can neither be called quadrupeds nor bipeds, their usual mode of
progression being an awkward compromise between the two. The same may be
said of one of the lemurs, the propithecus, the only member of its tribe
that attempts to move in the erect attitude. It does not walk, however,
but progresses by a series of jumps, its arms being held erect, as if
for balancing.
Of the apes, though many can stand upright, the gibbon is the only one
that attempts to walk in this position. This is a true walk, though not
a very graceful one. The animal maintains a fairly upright posture, but
walks with a waddling motion, its body rocking from side to side. Its
soles are placed flat on the ground, with the great toes spread
outward. Its arms either hang loosely by its side, are crossed over its
head, or are held aloft, swaying like balancing poles and ready to seize
any overhead support. Its walk is quickly changed to a different motion
if any occasion for haste arises. At once its long arms are dropped to
the ground, the knuckles closed, and it progresses by a swinging or
leaping motion, the body remaining nearly erect, but being swung between
the arms.
None of the other anthropoid apes ever walk erect, though they assume at
times the upright posture. But though they use all their limbs as
walking organs, they show no tendency to revert to the habit of the
quadrupeds. Their motion is like that of the gibbon when in haste, a
series of jumps or swings between the supporting arms. The shortness of
their arms, however, prevents them from standing erect, like the gibbon,
in doing this; and they bend forward to a degree depending on the length
of their arms, the chimpanzee the most, the orang the least.
As a rule, the flat sole of the foot is set on the ground, with the toes
extended, as in man, but the toes are sometimes doubled under in
walking. The orang rarely touches the ground with the sole or the closed
toes, but walks on the outer edge of the foot, the feet being bent
inward as if clasping the rounded sides of a bough. The other species
have a tendency in the same direction, the legs being bowed and the
gait rolling. In using the hands in walking, the closed knuckles are
usually placed on the ground, though occasionally the open palm is
employed. The whole movement of these animals is strikingly awkward, and
goes to indicate that there can be no satisfactory compromise between
life in the tree and on the ground.
The significant fact in these attempts to walk is that none of the
anthropoid apes show any inclination to revert to the quadruped habit.
Their attitude is in all cases an approach toward the erect one, which
posture is attained by the gibbon. The arms are used not as walking but
as swinging organs. Evidently their mode of life in the trees has
overcome all tendency toward the quadruped motion in these apes and
developed a tendency toward the biped. But none of them have gained the
muscular development of the leg known as the calf, nor an adjustment of
the joints to the erect attitude, since none but the gibbon walks erect,
and it does so only at occasional intervals.
The conclusion to be derived from all this is that the man-ape was in
its early days much more truly a biped than are any of the species
named. Like them, it had no tendency to revert to the quadruped habit.
The shortness of its arms was unsuited to this, while rendering it
impossible for the animal to progress in the semi-erect, swinging
fashion of the other anthropoid apes. As a result of its bodily
formation, it may have begun to walk erect at a very remote date, with
a consequent straightening of the joints and muscular development of the
legs. When this condition was fully attained, it was practically a man
in physical conformation, though mentally still an ape, and with a long
development of the brain to pass through before it could reach the human
level of mind.
The far-reaching conclusions here reached are all based on one important
fact, the shortness of man's arms as compared with the disproportionate
length of arm in the anthropoid apes. This, for the reasons given,
rendered the adaptation of the man-ape to life in the trees inferior to
that of the long-armed apes; while, as has just been said, it unfitted
it to walk on the ground either as a quadruped or in the jumping method
of its fellow anthropoids. In short, the biped attitude was much the
best suited to its organization and the one it was most likely to
assume. This once adopted as its habitual posture, efficiency in walking
would be gained by practice.
When once this animal became a ground walker, its facility of motion in
the trees was in a measure lost. When the feet became accustomed to the
flat surface of the ground, they became less capable of grasping the
rounded surface of the bough. Fitness to the one situation entailed loss
of fitness to the other. The feet of the apes can clasp the bough
firmly, by curving around its opposite sloping sides, and to this these
animals doubtless owe their bowed legs and their disposition to walk on
the outer edge of the foot. This disposition the man-ape lost as its
foot fitted itself to the surface of the ground. It was probably
retained in a measure by the young, after it had been lost by the mature
form, and is still manifested in the position of the foot in the human
embryo.
These considerations bring us to an important question: Why did the
man-ape gain a length of arm not the best suited to its arboreal
habitat? Why, in fact, do changes in physical structure ever take place?
How does an animal succeed in passing from one mode of life to another,
when during the transition period it is imperfectly adapted to either,
and therefore at a seeming disadvantage in the struggle for existence?
The study of animal development has given rise to certain difficult
problems of this character, some of which have been solved by showing
that the supposed disadvantage did not arise, or that it was balanced by
some equal advantage. In this way a considerable gap in life conditions
has perhaps occasionally been crossed. Small gaps have doubtless been
frequently passed over in the same manner.
In the case of the anthropoid apes, we perceive a considerable variation
in the length of the arms, from the very long arms of the gibbon to the
comparatively short ones of the chimpanzee. These differences are
probably the result of some difference in their life habits, and accord
with the possibility of a still shorter arm in the man-ape. There is,
however, some reason to believe, as we shall show later on, that the arm
of this animal was longer and the leg shorter than in man himself, their
comparative length perhaps not differing greatly from that of the
chimpanzee. Aside from all other considerations, the use of the legs as
the sole organs of locomotion could not well fail to produce this
result, the legs growing longer and stronger in consequence of the
increased duty laid upon them, and the arms growing shorter and weaker
through their release from duty in locomotion. The case does not differ
in character from those of the dinosauria and the kangaroos, in both of
which instances a release of the arms from duty in walking was followed
by a considerable decrease in length and strength, while the legs grew
proportionally stronger.
If any disadvantage attended the shortening of the arms of the man-ape,
to the extent that this may have taken place in the tree, it was
probably correlated with some advantage. In the various instances of
short-armed animals cited this appears to have been the case, and it was
probably so in man's ancestral form. While the hands continued useful in
grasping and enabling the animal to maintain its place on the boughs,
they may have been gradually diverted to some other service, with the
result that the animal found the tree less desirable than before as a
place of residence and sought the ground instead. This would be
particularly the case if the new duty was one best exercised upon the
ground.
Shall we offer a suggestion as to this new use? Such changes are usually
the result of some change of habit in the animal, frequently one that
has to do with its food. Change of diet or of the mode of obtaining food
is the most potent influencing cause of change of habit in animals, and
the one that first calls for consideration.
The apes are frugivorous animals, though not exclusively so. Carnivorous
tendencies are displayed by many of them. They rob birds' nests of their
eggs and young, they capture and devour snakes and other small animals.
In zooelogical gardens monkeys are often observed to catch and eat mice.
It is evident that many of them might readily become carnivorous to a
large extent under suitable conditions. The large apes are usually
frugivorous, but some of them eat animal food. This is the case with
both the chimpanzee and the gorilla. The latter, while living usually on
fruit and often making havoc in the sugar-cane plantations and
rice-fields of the natives, also eats birds and their eggs, small
mammals and reptiles, and is said to devour large animals when found
dead, though it does not attempt to kill them for food. The young
gorilla which was kept in captivity at Berlin became quite omnivorous in
its diet.
With all this readiness to eat animal food, none of the existing apes
are carnivorous to any large extent, but the fact of this inclination
makes it not improbable that some of the apes of the past may have been
much more so. It is quite within the limits of probability, for
instance, that the man-ape at an early date became omnivorous in its
diet. Its change in structure may well have been the result of a decided
change in diet, such as that from fruit to flesh food. Such a radical
change as that from vegetable to animal food would certainly demand a
more active employment of the arms as agents in capture. Fruits and nuts
wait to be pulled; animals must be caught before they can be eaten. The
former is an easy matter to an arboreal animal; the latter might prove a
difficult one, especially if large animals were to be captured.
In short, the pursuit and capture of any of the larger animals for prey
could not fail to modify to a great degree the use of the arms. Their
employment in locomotion would interfere seriously with their utility in
this direction. To succeed in capturing nimble prey by an animal with
the ape form of hands a considerable freedom of the arms would be
necessary, and the feet would have to be mainly, if not wholly, depended
upon for motion. The ape has not the sharp claws of the carnivora with
which to seize and hold its prey. It must have been obliged to use its
palms for this purpose, and this it could not well have done unless they
were free in their action.
It is conceivable, indeed, that the man-ape may have run down its prey,
or sprung upon it from covert, and seized it with the hands, but there
is good reason to believe that this was not its mode of capture. The
organization of the ape tribe gives it a characteristic action which is
not to be found in any other group of the vast animal kingdom, that of
handling and throwing missiles. In this it necessarily stands alone,
since no other animal has a grasping palm. The power is one of prime
importance, for without it we cannot perceive how man could ever have
emerged from the general animal kingdom. The use of missiles is by no
means uncommon with the monkeys. We cannot safely accept the story that
American monkeys will throw cocoanuts from tree-tops at those who hurl
stones at them from below, from the fact that the cocoanut seems too
heavy and too firmly fixed to its support for the strength of those
small species, but it is not uncommon for them to throw lighter objects.
Yet in doing this they usually seem to have no idea of aim, but toss the
missile aimlessly into the air. Of the large apes, the orang will break
off branches and fling them at its tormentors, or will throw the thick
husks of the durian fruit, but with similar lack of aim. The most
skilful in this exercise are some species of baboons, which can hurl
branches, stones, or hard clods with much dexterity.
It is of interest to find existing apes availing themselves of their
grasping power in this manner, since it leads us irresistibly to the
conclusion that the man-ape may have done the same thing. The species
which use missiles fail to take aim for two reasons, one that they
employ them only occasionally, often in imitation of human action, the
other that their arms are ill suited to this motion from their constant
employment in another duty. In the case of the man-ape we may justly
look for a more effective result, since if the arms became relieved from
duty in locomotion they were free to gain facility of action in other
directions.
If in addition to this the man-ape began to use missiles with a definite
purpose in view, that of striking down animal prey, so that the use of
such weapons became habitual instead of occasional, it would soon gain
some power of aim and a growing strength and skill in the throwing
motion. It is quite probable, also, that an early use of weapons was in
the form of clubs, which were retained in the grasp to strike down the
prey when overtaken. In this case, we may imagine our primitive biped
running swiftly after its prey, club in hand, striking at it when within
reach; or, if it should prove too swift, hurling the club or a stone
through the air with the hope of bringing it down in this manner. Such a
flinging action, if now and then successful, would be likely soon to
become habitual; while the arm would grow accustomed to this new motion,
and attain skill in taking aim. We may reasonably infer, also, that the
club would be used for defence as well as for offence, in case the
man-ape were in its turn pursued by larger animals. Instead of fleeing
to the nearest tree, it might now stand its ground and beat off its
enemy.
All must admit the probability, in a large tribe of animals with
grasping power in their hands, and in the habit of using missiles
occasionally, of one or more species coming to use them habitually. All
the anthropoid apes are certainly intelligent enough to do this, if it
should prove advantageous to them. Its principal advantage, however,
would seem to be to a species that became largely carnivorous and needed
to capture running or flying prey.
The habit of using implements is one of supreme importance in animal
evolution. To it we owe man as he exists to-day. While animals confined
themselves to their natural weapons of teeth and claws, their
development must have remained a very slow one and been confined within
narrow limits. When they once began to add to their natural powers those
of surrounding nature, by the use of artificial weapons, the first step
in a new and illimitable range of evolution was taken. From that day to
this, man has been occupied in unfolding this method, and has advanced
enormously beyond his primal state. A crude and simple use of weapons
gave him, in time, supremacy over all the lower animals. An advanced use
of weapons and tools has given him, in a measure, supremacy over nature
herself, and raised him to a stage almost infinitely beyond that of the
animal which trusts solely to teeth and claws.
So far as we know, only one of the innumerable species of animals
attained this development; unless, indeed, the various races of men had
more than one ape ancestor. For the appearance of man there became
necessary, first, the development of an order of animals with power of
grasp in their hands; and, second, the development of one or more biped
species, with hands freed from duty as walking organs and capable of use
in other directions. A third necessity was very probably the exchange of
the frugivorous for the carnivorous habit, which would act as a
predisposing agency in inducing the animal to desert the tree for the
ground, and to employ weapons in the chase. The final result of all this
would be an erect, walking, and running animal, with arms and hands
quite free from their old duty, except during an occasional return to
the tree, and with the necessary straightening of joints and development
of supporting muscles.
What has been advanced above is, no doubt, largely a series of
assumptions and conjectures, few of which are sustained by known facts.
But as the matter stands, no other method of dealing with it can be
adopted, since the facts in the case have in great part vanished. What
we know positively is that man exists, and that in physical structure
he is very closely related to the anthropoid apes. What we have
excellent reason to feel assured of is that man has descended from the
lower animals, and in all probability from an ape-like ancestor. We know
that one or more species of anthropoid apes have become extinct, and can
reasonably conjecture that one ancient species became modified into the
form of man. We know that human remains have been found that, to some
small extent, fill the gap between man and the ape. Correlative evidence
exists in the variations in length of limb in the existing anthropoids,
their efforts to walk upright, their varied degree of dependence upon
the arms for locomotion, and the occasional use of missiles by these and
lower forms. To these may be added the carnivorous tastes shown by many
members of the ape family, with the indication that more decided
carnivorous habits might readily be assumed.
Taking the stand that such a partly carnivorous anthropoid ape, biped in
structure, appeared and made the ground its usual place of residence, we
find ourselves on the direct trail of man. Long ago as this may have
been, and far and difficult as was the journey to be made, the way was
thenceforth straight and well-defined. Such an animal, living largely on
animal food, and using weapons superior to its natural ones in the
capture of prey, was essentially a man, however low may still have been
its level of intelligence. Its feet were firmly fixed upon the upward
track, and only time and stress of circumstance were needed to carry it
upward to the high level of civilized man.
We may, indeed, go further than this. We are in a measure justified in
saying what this man-ape was like, this creature which had left its
early home in the trees and began to walk upright upon the earth,
pursuing the larger animals and capturing them for food. It was probably
much smaller than existing man, little if any more than four feet in
height and not more than half the weight of man. Its body was covered,
though not profusely, with hair, the hair of the head being woolly or
frizzly in texture, and the face provided with a beard. The complexion
was not jet black, like the typical negro, but of a dull brown hue, the
hair being somewhat similar in color. The arms were lank and rather
long, the back much curved, the chest flat and narrow, the abdomen
protruding, the legs rather short and bowed, the walk a waddling motion,
somewhat like that of the gibbon. It had small, deep-set eyes, greatly
protruding mouth with gaping lips, huge ears, and in general a very
ape-like aspect. Our warrant for this description of man's ancestor must
be left for a later portion of our work. We shall only say here that it
is based on known fact, not on fancy.
VI
THE DEVELOPMENT OF INTELLIGENCE
The full adoption of the erect attitude gave the ancestor of man an
immense motor supremacy over the lower animals, for it completely
released his fore limbs from duty as organs of support and set them free
for new and superior purposes. In all the animal kingdom below man there
exists but a single form that emulates him in this possession of a
grasping organ which takes no part in walking or in other modes of
locomotion. This is the elephant, whose nose and upper lip have
developed into an enormous and highly flexible trunk, with delicate
grasping powers. The possession of this organ may have had much to do
with the intellectual acumen of the elephant. Yet it is far inferior in
its powers to the arm and hand of man; while the form, size, and food of
the elephant stand in the way of the progress which might have been made
by an animal possessed of such an organ in connection with a better
suited bodily structure.
For a period of many millions of years the world of vertebrate life
continued quadrupedal, or where a variation from this structure took
place the fore limbs remained to a large extent organs of locomotion.
Finally a true biped appeared. For a period of equal duration the mental
progress of animals was exceedingly slow. Then, with almost startling
suddenness, a highly intellectual animal appeared. Thus the coming of
man indicated, in two directions, an extraordinary deviation from the
ordinary course of animal development. Both physically and mentally
evolution seemed to take an enormous leap, instead of proceeding by its
usual minute steps, and in the advent of man we have a phenomenon
remarkable alike in the development of the body and the mind.