MANLIKE TENDENCIES
BRAINS OF GIBBON AND ORANG-OUTANG
There is little about the Old World monkeys, either in their mode
of life or in their appearance, to inspire respect or confidence.
The savage fierceness of the baboon, the mischievous nonsense of the
macaque, seem like flimsy foundations upon which to build a race
of intelligent human beings. When these animals first made their
appearance they were but vague foreshadowers of what mankind might
be. It is not alone their form and structure that interests us; their
actions, habits, and behaviour must be carefully studied at the same
time.
_The Anthropoid Gibbon_
Had the human eye been able to observe all that transpired in the early
days of the monkey kind, it would have been difficult to believe that
a race of men was in the making. It would have seemed incredible that
from these chattering, restless monkeys change and modification could
eventually bring forth that development necessary for the human form.
And yet in the course of time changes of this kind did bring into
existence an ape which bore a much closer resemblance to man. It was
then possible to foresee how, from this new kind of animal, certain
human features might be derived. This particular member of the ape
world is the gibbon. All of his tendencies make him somewhat shy and
inconspicuous. At the zoölogical gardens he is generally sitting high
up on a perch in his cage with his long arms folded over his head,
peering quietly about him. His fur is usually dark, although some
members of his family are quite light in colour. The most impressive
thing about the gibbon is the fact that he can stand up, walk, and run
upon two legs. This he does a little awkwardly, but not unlike a human
being. In a certain memorable moving picture, an unusually interesting
silvery gibbon nearly usurped the rôle of leading man. His marvellous
feats earned for him universal applause, and whenever he appeared he
was the centre of attention. Among its most stirring moments, this
picture shows a dramatic scene in which a great Indian elephant whose
young one has been captured demolishes the dwelling of the jungle
native who has trapped her offspring. Shortly after the native with his
wife and children has escaped to safety, the gibbon emerges cautiously
from the wreckage of the home. Through the darkness of the forest he
discerns the glistening eyes of a tiger that is about to spring upon
him. Realizing that retreat is cut off, he takes to flight. In escaping
he stands upright and runs like a man, screaming in his fright in a
thoroughly human manner. Fortunately for the gibbon, the branch of a
tree comes opportunely in his path, and then, with a single upward
bound, he is off like a bird through the trees to safety.
Gibbons are gentle, affectionate creatures. They are also timid and at
the first sign of danger hurry away through the forest as far up in
the trees as they can go. The gibbon’s body and head are relatively
small, being only a little larger than some of the smaller macaques.
The animal’s legs are short and it has no tail. A prominent feature is
the exceptional length of the forearm and of the fingers. The hand is
slender and longer than the foot. The female bears one young at a time,
which the mother carries under her body, the young one clinging to the
fur on her chest with hands and feet. This burden does not embarrass
her in the slightest as she swings her way from tree to tree through
the forest. She makes as good time in this transportation as the
unincumbered males.
In the wild state the gibbons never leave the jungle, and live for the
most part throughout southern Asia and the adjacent islands. A few of
them venture from the inland forests to the vicinity of the coast.
All of the gibbons are highly developed for life in the trees. This
specialization is important not only for the effects it has had upon
these apes but also for those developments in them which were to be of
subsequent and substantial advantage to the rise of man.
There are many different varieties of gibbons such as the white-handed
gibbon, the silvery gibbon, the white-cheeked gibbon, the slender
gibbon. The animal that we shall consider is the hoolock gibbon of
India. He gets his name from a peculiar sound or cry which he makes.
If it were at all possible to imitate this cry it might be expressed
as “hooloo! hooloo! hooloo!” Mr. Candler has studied this interesting
animal at close quarters, and his account of its habits is well worth
quoting:
The Hoolock swings along the thinnest part of a bough or to the
slender end of a bamboo, until it bends to its weight, then with
a swing and a sort of a kick-off he flies through the air seizing
another branch, and swinging along it with the accuracy of a
finished trapeze performer. I fancy he does very little walking in
the wild state, for I have never seen a wild Hoolock on the ground.
Moreover, they are only found in the dense jungle where the ground
is everywhere covered with tangled vegetation. The Hoolocks are
extremely shy and it is difficult to watch them as they are concealed
by leaves high up on the bamboo clumps or tops of forest trees. The
cry of the Hoolock is characteristic. It is a very pleasing note,
rising and falling in intensity, and reminding one somewhat of a
pack of beagles giving tongue on a scent, which is waxing and waning
in strength as a larger or smaller number of the band join in the
chorus. It is heard chiefly in the early morning, then through all
the heat of the day there is silence, but towards evening as the sun
sets you may hear it again.
One might almost think that their early morning cry was like a rising
bell, and their cry toward evening was their curfew.
_Manners of the Gibbon_
Gibbons live in fairly large communities. They are constantly on the
move. From what is known of their intelligence it seems probable that
their movements are guided by definite plans. They even seem to have
some simple sort of governmental system. Tea planters in India often
keep these gibbons as pets for years. They run about the compound
quite freely. At times they suddenly disappear and are gone for several
months. Eventually they return quite unconcerned, as if nothing had
occurred to interrupt their pleasant human associations. For the most
part the gibbon is sociable. After he has become acquainted he will
often sit on the arm of a person’s chair at breakfast. Whatever his
appetite, he will never reach out for food at the table, although his
long arms give him much advantage over his human host. Nor will he
ever snatch things off the table. His manners are above reproach and
he keeps himself scrupulously clean. As the day is drawing to a close
it is his habit to get ready for the night. At sunset he settles down
to sleep, safely seated in the fork of a tree, usually with his long
arms over his head. He is never boisterous, mischievous, or noisy.
Oftentimes he seems to be more in sympathy with children than with
grown-ups.
The diet of the gibbon includes a long list of foods, such as fruits,
leaves, and young shoots, spiders, birds’ eggs, insects, and young
birds. If captured young the gibbon is readily tamed. He is never sulky
or ill tempered and shows marked intelligence both in learning many
tricks and adjusting himself to the rules of the home.
The locomotion of these animals among the trees is totally different
from that of the monkeys. The latter climb about using both hands and
feet. Gibbons employ their arms almost exclusively, swinging from
branch to branch, with the legs tucked close to the body. This is such
an important change in the transportation methods of apedom that we
should give it particular attention in order to note what effects it
had produced upon the gibbons themselves. In the first place, swinging
from one limb to another by the hands greatly elongated the forearm and
the fingers. This kind of locomotion gives the gibbon the appearance of
taking tremendously long strides with his arms. The right hand, first
grasping a branch, permits the animal to swing twelve or more feet to
the next branch which is grasped by the left hand. In the next step the
forward stride is taken by the right hand. Thus the animal alternates
the right and left hand just as we alternate the right and left foot.
It is probably for this reason that the gibbons have been called “tree
walkers” (_Hylobates_).
The second effect produced by this kind of swinging locomotion, called
brachiation, is even more decisive in the final outcome. Transportation
such as this swinging by the hands drew the body more and more into the
upright position. It brought about many of those fundamental changes
which made it possible for the gibbon to stand upright, walk, and run
upon two legs. Compared with other animals of this class, the gibbon
is the most two-legged of all the apes. He walks rather quickly in
the erect posture. His gait is waddling, and if pursued he will make
every effort to reach some support by which he can swing himself to
safety. In walking he turns his leg and foot outward, which gives him
a bow-legged appearance, added to which the shortness of his legs
makes his movements in walking and running far less graceful than
these acts ultimately came to be in their highest exponent, man. Here
undoubtedly may be discerned important elements for the inception of
human locomotion. They appear in an animal which can stand, walk, and
run upright, and also possesses well-developed hands.
_Gibbon’s Resemblance to Man_
The gibbons are said sometimes to scoop up water in the hollow of the
hand in order to drink. At other times they stretch out their long arms
among the foliage and lick off the dew which adheres to their hair, in
this way quenching their thirst.
In view of these facts our estimate of the gibbon may credit him
with certain manlike traits. Yet his resemblance to human beings,
considering the animal as a whole, is at best sketchy and vague. Casual
observation of the gibbon does not bring any clear association with
the human being at once to mind. Only after watching him, after noting
the manner in which he gets about, after seeing him walk and run on
two legs, is it possible to recognize certain tendencies which point
in the human direction. It is for this reason that the gibbon is said
to represent a stage preceding the manlike apes. Some students of
this question class the gibbon with these anthropoid apes. It seems
better judgment, however, to consider him rather an animal showing
dispositions which serve as a starting point for the anthropoids.
These tendencies, as they are crystallized in the gibbon, represent an
introductory chapter in the history of all those animals which later
became notable because they walked more or less upright and had the
use of hands. Thus the gibbon is often spoken of as pro-anthropoid.
He himself is a modern animal. One of his venerable ancestors, very
much like himself, lived long ago--_Propliopithecus_ of the Oligocene.
The descendants of this ancient extinct ape with the long name,
whose fossil remains have been found in Egypt, followed two lines of
development. One line led up to the modern anthropoid apes and man, the
second to the modern gibbons. The first offshoot from this line gave
rise to a great ape which in many features looks much more like man
than does the gibbon. This is the orang-outang. He is one of the big
apes seen in the large primate cages of the zoölogical gardens. He may
be recognized by the brownish-yellow hair which covers his body, by his
face which bears a humorous caricatured resemblance to man, and by the
erect posture which he assumes much of the time. Although he climbs
about his cage and its supports like a skillful acrobat, this manlike
ape lacks the grace and agility of the gibbon. He is wild and shy, but
possesses enormous strength, which makes him more than a match for the
most able-bodied man.
_The Orang-Outang_
The orang lives in Borneo and Sumatra. He has not been found elsewhere
in the world. In his island home he enjoys a deserved reputation
because of his prodigious strength. When full grown he stands a little
over four feet in height. He has a heavy body, short thick neck,
receding forehead, thick lips, and a face uncovered by hair. His muzzle
protrudes to form a thick and heavy upper jaw, with a large mouth and
large teeth. In the full-grown male the cheek pouches become greatly
enlarged, so that they look like an old-fashioned ruff around the head.
This feature gives him a hideous and gruesome appearance. The arms are
long, reaching almost to the ankles when the orang stands upright.
The hands are long and narrow, the thumb is short, the fingers are
united by webs at their bases. The legs are short in comparison to
the length of the body and considerably bowed. The feet are long and
narrow. The great toe is short, but it can be used for grasping the
branches. Fleshy pads over the buttocks are present in the adult male,
but the orang has no tail. He is easily distinguished from the other
great apes by his bulging muzzle and his light yellowish-brown hair.
He seldom exceeds four feet two inches when standing upright, but his
outstretched arms together measure nearly eight feet from finger tip
to finger tip. Some specimens killed by hunters have been reported to
stand five feet three inches high.
Among the first accurate accounts of the orang-outang’s life is that
of Alfred Russell Wallace appearing in his famous book _The Malay
Archipelago_, from which the following description is an extract:
The orang has a wide distribution, inhabiting many districts along
the coast of the island [Borneo] where it appears chiefly confined
to the low swampy forests. It particularly affects a country which
is low and level with a few isolated mountains, on some of which
the Dyaks have settled and planted many fruit trees which are a
great attraction to the orang, as his most desirable food seems to
be unripe fruit. The habitual habitat of the animal is in the lofty
virgin forests, in which they can roam in every direction with as
much facility as the Indian on the prairie, passing from treetop to
treetop without being obliged to descend to the earth. The orang
makes his way leisurely through the forest, with remarkable ease.
He walks deliberately along the larger branches, in a semi-erect
attitude which his great length of arm and the shortness of his legs
causes him naturally to assume. But this proportion between his limbs
is increased by his walking on his knuckles and not on the palm of
his hand. He chooses those branches which intermingle with those
of an adjoining tree. In approaching these he stretches out his
long arms, seizing the neighboring bough with both hands and then
deliberately swings himself across to the next branch, on which he
walks along as before. He never jumps or springs nor even appears to
hurry himself, yet he manages to get along almost as quickly as a
person can run through the forest beneath. The long powerful arms are
of greatest use to the animal, as they enable him to climb easily the
highest trees, to seize fruit and young leaves from slender boughs
which will not bear his weight and to gather leaves and branches from
which to form his nest at night. When wounded he endeavors to make
a nest in which to remain quiet, and similarly at night prepares a
resting place in the tree to sleep. He likes this place low down in
the tree, not over 20 or 30 feet from the ground, probably because in
this position it is warm and less exposed to the wind.
The orang, it is said, makes a new nest for himself every night
or perhaps remakes an old one. In rainy weather the animal covers
himself with leaves or large ferns, and this may have led to the
belief that he actually builds huts in the trees. The animal does not
arise from his bed in the morning until the sun is well up and has
dried the dew upon the leaves. He seldom returns to the same tree two
days in succession.
They have no particular fear of man, and only retreat slowly after
a considerable period of scrutinizing inspection. They do not have
so much of the gregarious tendencies as do the other large apes. Two
full-grown animals are seldom seen together, but males and females
are sometimes accompanied by half-grown young ones. At other times
three or four young animals are seen together. Their food consists
almost exclusively of fruits, leaves, buds and young shoots. They
seem to prefer the unripe fruit, even when very sour or intensely
bitter, the red fleshy arillus being a particular favorite. The orang
rarely descends to the ground except when pressed by hunger, when
it seeks the succulent shoots at the riverside. In very dry weather
it also comes down from the trees in quest of water, of which it
generally finds sufficient in the hollow of the leaves. They have
been seen upon the ground playing together, at which times they
assume the erect posture and grasp each other with their arms.
Wallace believes that the orang seldom stands or walks erect unless
when using its hands to support itself by the branches overhead, or
when attacked. He also thinks that the representations of it walking
with a stick are quite imaginary. In its general demeanour the orang
would impress one as dull and apathetic. When seated among the branches
its back is bent, its head is bowed, and its long arms either reach
up to grasp a branch overhead or hang listlessly by its sides. Some
explorers have maintained that the animal builds huts for itself in the
trees. This is largely an exaggeration, but the orang has developed
an interesting technique for building itself a nest in the trees as
night approaches. Small branches are first laid crosswise to form a
framework, and over this a thick bed of leaves is placed. The orang is
quite fussy about the construction of its bedroom and takes good care
to cover itself up when the wind is chilly or the night stormy. Even in
captivity the animal is particular about the details of its bedchamber
and always manages to cover itself with straw or newspapers if it
happens to find them in the cage.
The orang has other constructive tendencies. He often manifests some
engineering skill in devising supports for himself in his cage. With
these he will amuse himself by the hour, climbing upon the support,
dropping to the floor, and repeating the entire performance time after
time in as many different ways as he can. In one instance a young male
orang found a long rope hanging from the roof of his cage. He clung to
the rope by his left hand and both feet. With his free right hand he
passed the end of the rope around the bars, turned it through a right
angle, and pulled it tight. In this way he made an interesting perch
for himself. If anyone detached the rope he at once replaced it and
thus remade his perch.
On the ground the orang is clumsy. He usually goes on all fours, and
his walking gait has been likened to that of a very old man bent down
by age, hobbling along with the aid of a cane. It is interesting to
note that in walking he goes on the outer borders of his feet. His
stride is short and shuffling. Even when hurrying he lopes along
rather than runs. Unlike the gibbons, the orang does not use his hand
as a drinking cup. His lower lip protrudes in a capacious trough for
collecting rain water. If given a pail of milk or water the orang lifts
the pail and pours the fluid into this trough and then swallows it.
When captured young the animals can be trained and taught to obey many
words of command. In time they get over their shyness and seem to like
human companionship. They are, however, easily frightened. Females when
pregnant separate themselves from the others and remain more or less in
seclusion until the young are born. The offspring grow slowly and, like
human infants, require the care of their mothers for a long time. When
the mother moves about the young one clings to the hair of her chest.
This is a marked characteristic of child care throughout the ape world.
_The Orang in Infancy_
Wallace recites an interesting experience which he had with a baby
orang whose mother was shot and killed by him in the forest the
preceding day. This experience is especially interesting because of
its many human resemblances. When Wallace stooped to pick up the
helpless infant orang that lay sprawling on its back, his long beard
was immediately seized by the grasping hands and feet of the youngster.
It was a long and painful ordeal to get away from this clinging infant.
The baby orang had but a single tooth, but soon its milk teeth began
to appear, much as in a human infant. The lack of milk on the island
made it difficult to feed the young ape. When a finger was placed in
its mouth it would suck with great vigour, drawing in its cheeks in
a vain effort to extract milk. After persevering for a long while it
would give up in disgust and start screaming, much as would a human
baby under similar circumstances. When handled or nursed it was always
quiet, but if laid down by itself it would invariably cry. It enjoyed
being rubbed after its morning bath and was quite happy while its hair
was being combed and brushed.
For the first few days it clung desperately by all four hands to
everything it could reach, and Wallace remarks that it was necessary
for him to be cautious in keeping his beard out of the way. He felt
that the infant ape was lonely and needed companionship, so a little
harelipped monkey of the macacus variety was obtained as a playmate. It
was curious to see the difference in the actions of these two animals,
the one an offspring of a humbler monkey, the other born of one of
the great manlike apes. The two young ones were about the same age.
The orang, just like a human baby, would lie upon its back helplessly
rolling from side to side, stretching out all four hands into the air
and striving to grasp something, although hardly able to guide its
fingers to any desired object. When dissatisfied it opened wide its
almost toothless mouth and expressed its discomfort in an infantile
scream. The little macacus monkey, on the other hand, was constantly
on the go, running and jumping about, examining everything in sight,
taking hold of objects with greatest precision, balancing itself on the
edge of its box and searching everywhere for food. There could scarcely
be a greater contrast. One could hardly escape the conclusion that in
the orang, as in man, a long period of slow growth is necessary for
its final development. The advantages of such growth are sufficiently
apparent and need no further comment.
_Psychological Tests_
The orang-outang has not yet been so extensively subjected to
psychological study as its more sociable fellow ape, the chimpanzee. It
is fortunate, however, that at least one of this species has come under
the critical observation of an astute student of animal behaviour,
Professor Robert M. Yerkes, of Yale University. In his notable
contribution on the mental life of monkeys and apes, Professor Yerkes
has described certain tests devised for estimating the intelligence of
lower animals, and applied to the partly grown orang known as “Julius.”
These tests were devised on what is known as the “multiple choice
basis.” Julius, after many unsuccessful efforts to solve his problems
by the method of trial and error, quite unexpectedly seemed to get the
idea of what was wanted. He suddenly responded to the test without a
single mistake. He seemed to solve his problem quite as if he knew what
it was all about. It took him a long time, but at last he showed that
he was capable of some kind of thinking. The curve of learning as it
was charted day by day from the actions of Julius indicated that if he
had been a human subject his mental process would possibly have been
described as rational. Professor Yerkes feels justified in concluding
from this evidence that the orang solves his problems ideationally.
In general, Julius appeared to be far superior to other monkeys in
his intelligence. His mental processes were slow, but the method of
learning by ideas seemed to replace the simpler way of trial and
error which is common throughout the monkey world. Julius persistently
endeavoured, and often vainly, to gain some insight into a situation.
Even though slow, he showed nevertheless that the brain had at length
attained the development necessary for the production of real ideas.
However questionable this attainment may be in the monkeys or in other
lower animals, there seems to be little doubt about its existence in
the orang.
_Brains of the Gibbon and Orang_
Upon reviewing the facts concerning the gibbon and the orang, we may
ask certain questions. For example, does the real progress which these
two members of the ape world show in their capacity to do things
manifest itself as a measurable difference in their brains? Would it
be possible to maintain that these were indeed the brains of more
capable and more intelligent animals than the monkeys? Certain features
about the brain of the gibbon and the orang are striking. In the first
place, the pattern of their convolutions is more complicated. The
orang especially has more grooves and convolutions upon the surface
of the superbrain. It is believed, and many facts sustain the belief,
that convolutions indicate in a general way the capacity of an animal
to develop brain power. In the gibbon the increase in convolutions
is not so pronounced as in the orang, although it is not difficult
to see that in this respect the gibbon’s brain is much improved when
compared with lower monkeys. Upon identifying the familiar landmarks,
it is obvious that the groove of Sylvius, the central groove, and
even the ape groove form more decisive boundaries and outline more
prominent lobes than in macaque or baboon. The superbrain departments
for sight (occipital lobe), for hearing (temporal lobe), for body
and contact senses (parietal lobe), are all more extensive. Each
lobe, by the presence in it of smaller secondary grooves which do not
appear in the lower monkeys, shows how its capacity has expanded. The
grooves of the brain, in their arrangement, number, and relations,
now begin to assume an appearance similar to that of the human brain.
Each sense department in the orang is well organized. Each has gained
in prominence, thus indicating how the senses of sight and hearing,
and body and contact senses, have increased their capacity. By means
of its amplified sensory combinations the superbrain was eventually
capable of producing intelligent reactions. The area in front of the
central groove manifests the chief improvement. This is the part of
the brain in contact with the frontal bone. It has made some advances
in the gibbon but is still more prominent in the orang. At this stage
it is possible to speak of a well-developed frontal lobe acting as the
headquarters of all higher mental functions. The large increase in the
size of the orang’s brain is in some degree proportional to the size of
the animal’s body. Many other factors have actuated this expansion and
will receive special consideration in a subsequent chapter.
If it were possible to reduce the difference in intelligence between
the orang and the gibbon to actual figures, the contrasts would be
marked. Certain estimations of this kind are significant. The bridge
(_pons Varolii_) on the base of the brain, which may be regarded as
an index of intelligence, has a value of .200 in the gibbon and .300
in the orang. The pyramid, indicating the degree of skill in movement
attained by the animal, as well as the degree of controlling itself by
the dictates of its will, also shows a considerable difference. This
difference is again in favour of the orang, whose pyramid is estimated
at .160, while that of the gibbon is .138.
Many other points indicating similar advantages held by the orang over
the gibbon might be cited. They have the same general meaning, namely,
that the orang possesses a better brain. In fact, all of the evidence
gathered from this animal reveals many manlike tendencies. Such
tendencies, both in brain and behaviour, first became notable in the
gibbon. At this stage they were not prominent features. They were, so
to speak, in a preparatory or pro-anthropoid phase. In the orang those
manlike tendencies foreshadowed by the gibbon became more definite and
better developed. They formed the foundations for new combinations out
of which was to emerge a still higher type of animal.