ON THE WAY UPWARD
BRAINS OF THE OLD WORLD MONKEYS
We have seen that the first steps leading to improvements in the
primate brain were taken by certain humble creatures living in distant
parts of the earth, and by the great tribes of the New World monkeys
inhabiting South America and Central America. These steps did not lead
far along the path of progress. They were only a beginning, the first
harbingers of man’s arrival. Many lowly animals in the ape house at the
zoölogical gardens reveal numerous features suggestive of the human
being. Such features not only include their fingers, finger nails, toes
and toe nails, but even more their facial appearance. Many of these
monkeys look like diminutive old men. They snarl and show their teeth
when angry. Their way of indicating displeasure is almost human. They
make certain expressive gestures, like nodding or tilting of the head
to one side in a quizzical or even pathetic manner. They make plaintive
cries or sounds, in some cases almost like the notes of a bird, or they
scream out loudly in anger. All of these New World monkeys are notable
for one other reason. They do not make any of those humorous grimaces
that are so amusing in the Old World monkeys. These latter manifest a
certain drollness in their constantly changing facial expression.
The Old World monkeys include about three quarters of all living
species. They are embraced in one great family, but the members of this
family show many differences ranging from the huge dog-faced baboon to
the small bonnet monkey. Some of them are gentle and affectionate, some
are savage, pugnacious, and treacherous. This entire family is spread
out over the hot or semitropical regions of the world. Many of its
members live in the damp, tropical forests; others prefer rocky, almost
barren country, and a few seek their homes in temperate climates. Some
monkeys are found among the lower ranges of the Himalayas and may be
seen in the winters playing among the branches of snow-laden trees. Two
varieties seem to have a surprising endurance in really severe cold.
They inhabit the elevated regions of eastern Tibet.
In picturing to ourselves the characteristics of a monkey we are apt
to have the conception of an animal that can hold on and hang by its
tail. None of the Old World monkeys has this kind of tail. The greatest
number of them live in the trees, and the tail, while generally short
and stumpy, in some cases is decorative and almost plume-like. Most of
the Old World tribes are especially interesting and amusing because of
a large elastic pouch in each cheek. This pouch the monkey greedily
crams with food in his haste to get his meal into safe-keeping. When
the cheek pouches are filled both cheeks are bulged out and give the
animal somewhat the appearance of a gourmand embarrassed by a mouthful
of delicacies. Later on, at his leisure, the monkey chews and swallows
the food.
_Baboons_
By far the largest of the Old World monkeys are the baboons. They may
be recognized at once by three characteristics. The head and face look
much more like those of a dog than is true of other monkeys. They have
long and dangerous fangs in the upper and lower jaws. They go about,
like most four-legged animals, upon hands and feet which have much the
appearance of paws.
Further acquaintance with the baboon shows him to be a surly,
unmannerly, savage, and thoroughly undependable creature. All of his
tribes have fleshy pads over the buttocks, which in some cases are
large and brilliantly coloured. Some members of his clans, such as
the mandrill, have faces which look like gruesome masks or hideously
painted savages. The skin over the nose is a fiery red, while the
cheeks are swollen, ribbed, and of a vivid blue colour. A beard of
golden hue hangs beneath the chin in contrast to the dull olive drab
of the body. Protruding over the lips are savage canine teeth, long
and dagger-like. These baboons are about as large as a good-sized
dog. The colouring of the face adds considerably to the repulsive
unattractiveness of the animal. They run along on their hands and feet,
with their eyes directed downward, so that they are obliged to elevate
the large overhanging eyebrows in order to look upward and forward.
They go about with the palms of the hand and soles of the feet laid
flat upon the ground. The mother is often seen walking or scampering
around with a young baboon clinging to her back. Sometimes the mother
will sit up on top of a rock just like a human being. Her offspring
often perches on her neck after the fashion of a well-trained acrobat.
All of these monkeys are gregarious. They travel about in large
numbers. Often as many as a hundred individuals collect in one herd.
Because of their aggressive disposition, they are dangerous enemies,
especially when irritated or disturbed. Their long, sharply pointed,
canine teeth are capable of inflicting severe wounds. Although they
have no actual speech, they utter certain sounds that seem to be
thoroughly understood by all members of the herd. There is quite a
variety in these sounds. Some of them resemble barks, grunts, or
even screams. Often they make low and subdued murmurs with various
inflections, the meaning of which all the baboons seem to understand
immediately. Sometimes the slightest murmur from one of the members of
the herd will act as a signal or warning. This is particularly true
when the baboons are out on an expedition of pillage or mischief.
On such occasions they always station a lookout or outpost at some
favourable point from which the signal may be given upon the approach
of danger. The faintest murmur made by one of these lookouts will start
the marauding baboons scampering away to safety.
_Disposition of Baboons_
For the most part they live in rocky places near ravines, crags, or
hilly promontories where grass and trees are scanty. Their favourite
abodes are usually places surrounded by wide plains. This kind of home
enables them to lie in wait for the right moment to perpetrate some
thieving expedition upon a garden or field and at the same time to have
every opportunity of escape. They are much given to mischief of this
kind. Consequently they are feared and despised by the inhabitants of
the country which they infest. If attacked, they often turn upon their
pursuers and inflict serious wounds upon their assailants. Some baboons
prefer to live in the dense forest and climb readily about even in the
tallest trees. Those that live in more open country are very agile
in clambering among the rocks and are able to reach lofty heights or
positions of safety. The baboon eats a little of everything, although
its chief diet consists of roots, fruits, reptiles, and insects.
To procure their food they are continually searching, turning over
stones beneath which the desired food may be concealed. When young the
baboon is often quite gentle and affectionate, but with most of them
this disposition changes when they grow up. In captivity baboons are
surly and unfriendly. Even those born and reared in captivity are more
difficult to approach and teach than other apes. They are vindictive
and treacherous. Their disagreeable dispositions accord well with
their unpleasant and often repulsive facial expressions. Their savage
reactions and lack of intelligence have earned for them the reputation
of being the lowest of the Old World monkeys. Baboons seldom assume
the erect position for standing or walking. They do, however, sit upon
their haunches in a somewhat crouched position, but not so freely as
many other Old World monkeys. They all live in Africa, with a slight
extension into Arabia. It is well that these animals never grew to the
size of the great apes, for had they done so they certainly would have
been among the most dreaded and frightful creatures ever known on earth.
Dr. Ditmars, who has spent much time in observing monkeys, reports
many interesting studies and experiments concerning their behaviour.
Apparently the habit of throwing missiles when enraged is not uncommon
among baboons. Any angry monkey may in its rage grasp and hurl an
object such as a drinking pan, but there is usually no accuracy in
its aim or intention in its act other than an expression of irritated
feelings. None of the monkeys has ever been known to use a stick or a
club in attacking others or defending itself. Although the throwing
of missiles is almost unknown among monkeys, the baboon marks an
exception. As an instance, one day Dr. Ditmars found the visitors to
the ape house almost in a panic, due to the savage behaviour of a
big yellow baboon. A part of the cement had fallen out of the wall
of his cage and broken up into sharp pieces. These pieces the baboon
was hurling at the visitors through the bars in a most deliberately
offensive manner and with effective aim. The crowd in consequence had
retreated to various points of safety. Later a shovelful of coal was
placed in the cage of this same baboon. The pieces of coal he also used
as missiles, throwing them with calculating aim at the keeper and other
attendants. The baboon seems to have an excellent throwing arm, and
Dr. Ditmars credits him with good control and much speed. During this
experiment a baboon of a different species acted in precisely the same
way. In both of these animals their pitching capacity was demonstrated
without any previous practice or instruction, and from these
observations it would appear that baboons are natural-born pitchers.
_Macacus, the Indian Monkey_
Another one of the Old World monkeys, the macacus, shows a different
side of the picture. He is more friendly, more gentle, more full of
fun, and forever up to some sort of monkeyshines. Many of these monkeys
live in India. Mr. Kipling has described them in his famous “Road Song
of the Bandar-Log”:
Jabber it quickly and all together!
Excellent! Wonderful! Once again!
Now we are talking just like men.
Let’s pretend we are ... never mind,
_Brother, thy tail hangs down behind!_
These monkeys have their homes throughout the Indo-Malayan regions.
They extend northward into China and Japan and eastward into Tibet. The
macaques have a stout body and a proportionately large head. There is
considerable variation in the tail, which ranges from a long, sweeping,
plume-like appendage with a tuft at the tip, as in the lion macaque,
to a thick, stubby tail much like that of a dog which has been docked.
The pigtail monkey has a curled appendage. One of the macaques of
Japan has a mere stump, while the Barbary ape has no tail at all. The
macaques are the typical monkeys about which most of the favourite
stories concerning the ape kind have had their origin. Their enormous
cheek pouches, their facial grimaces, and the motion of their lips
make them unusually fascinating to watch. They are extremely noisy,
jabbering most of the time. They seem to have an extensive vocabulary
of sounds, consisting of shrill calls, grunts, low mutterings, barks,
chattering noises, and almost ear-splitting yells, which they emit
in moments of rage. They are playful and quarrelsome, and these two
phases of their behaviour pass without sharp line one into the other.
They never become involved in serious combats because they seldom
remain at one thing long enough to be effectual fighters. In their
quarters at feeding time they usually make a real pandemonium in their
frenzied efforts to stuff their cheek pouches as full as they can.
They have absolutely no consideration or courtesy on these occasions.
Their table manners are not only rough but actually ruthless, and the
most delicious morsels go to the strongest. The weak, the young, and
the female obtain what is left or go without. These monkeys are often
docile and affectionate. They make the most amusing kind of pets. No
animal is more mischievous or more destructive about a home where there
is anything within reach to break. Sometimes when they grow up they
develop the unpleasant tendency of being too strictly a one-man animal.
To protect their owner against an imaginary danger they will often
attack strangers or visitors.
_Behaviour of Macacus_
The head of the macaque is much less dog-shaped than that of the
baboon. The eyes are set closely together, and the animal sits on its
haunches a good deal of the time holding its head upright, so that
the eyes are directed forward. Its posture in sitting is quite human,
while its attentive gaze gives the impression that it is watching
intelligently all that is going on. Its nose is short and has a fairly
good nasal bridge. The lips are thin and the upper one is particularly
long. The hands and feet closely resemble human hands, except that the
palm is not so broad, the fingers are longer, and the thumb shorter.
In its movements the macaque is remarkably deft. It changes from one
position to another with surprising swiftness. These monkeys go about
in herds, often of considerable size. If captured young the animal is
easily trained and quickly learns many amusing tricks. It is full of
mischief and curiosity. Macacus monkeys frequently become a nuisance
in the neighbourhood of towns where they live in large numbers. When
full grown they are sometimes quite ill tempered and often savage even
to the extent of attacking the inhabitants without much provocation.
For the most part they live in cultivated tracts along the banks of
streams. They seem to seek rather than avoid the habitations of
man. They manifest little fear for their human neighbours and take
a real delight in molesting them by many annoying pranks. Sometimes
their attentions are vigorously resented and their human neighbours
turn upon them. Their behaviour on such occasions is like that of
tantalizing small boys who take an almost idiotic delight in the
vain efforts of their pursuers to overtake them, and continue their
aggravating antics in order to prolong the excitement of the futile
pursuit. If one happens to be captured, a number of them will turn
back to take the part of the unfortunate captive. In their native
haunts they are constantly on the move. Repose is totally foreign to
their daily programme. Scampering, swinging, chattering, screaming,
they go among the trees all day long. Either their actions are without
design, or else their purpose changes so rapidly and frequently that
their behaviour has the appearance of ceaseless motion. When together
they are very quarrelsome, constantly nagging or teasing each other,
but here, as in all of their activities, the object of their anger,
the victim of their jest, is as quickly shifted as their fleeting
attention. Having no fear of the water, they are able to swim for long
distances and greatly enjoy it. They feed upon spiders and many other
insects, besides fruits and berries. As compared with the baboon, they
show a greater mental alertness.
_Mental Tests_
Considerable psychological study has been made of the macaques,
particularly concerning their ability to learn and their mentality.
Dr. Kinnaman, who has made some of these studies, believes that they
have attained a higher level of intelligence than that ascribed to
the New World monkeys by Professor Thorndike. He thinks there is some
evidence that the macaques have powers of reasoning, although of a low
order. Dr. Hobhouse agrees with this view and adds that the macacus
monkey seems to be possessed of definite ideas. Professor Yerkes,
after a longer and more systematic study with experimental methods
better suited to the problem, agrees with Professor Thorndike that the
macacus may have a certain number of limited ideas. It is clear to him
also that there are extreme differences in the mentality of different
species of monkeys. The slow process which they display in the solution
of problems is quite surprising, in many instances being actually less
rapid than in some of the lower mammals.
One question is certain to arise at this point: How do the Old World
monkeys compare in mentality with lemur and tarsius and with the
monkeys of the New World? Perhaps the best answer to this question may
be obtained by watching the actions of these different animals in their
cages at the zoölogical gardens. Looking at a lemur as he jumps about
restlessly among the supports of his cage, it is quickly concluded that
this animal, not unlike a diminutive fox, is interesting only because
of his remarkable agility. Tarsius would probably not be found in
most zoölogical gardens because these animals do not survive long in
captivity. The marmosets would attract little more attention than the
lemurs, not only because of their small size, but also because of their
lack of interesting reactions. Howling monkeys, spider monkeys, and
woolly monkeys are more interesting because of the remarkable way in
which they use their tails like a fifth hand. Their facial expression
and their general behaviour, however, are somewhat monotonous.
The Old World monkeys, especially the macaques, hold the attention and
create a real interest. Here is to be seen a busy world of jabbering,
mischievous, tricky, athletic monkeys whose antics easily rival the
best of human clowning. There can be no doubt that these Old World
monkeys are on a higher mental plane than those of the New World.
The main fault to be found with them is that they never get anything
really done, except perhaps filling the pouches in their cheeks just
as full as they can. Even the grouchy baboons show some signs of
better mental powers than the South American monkeys. They have a
thoroughgoing hostility for their human contemporaries which they have
never changed, and their powers of organized banditry show a degree of
mental capacity that is foreign to the lower monkeys. This capacity we
should consider all the more noteworthy because the baboon manifests
a distinct tendency to lose some of the benefits derived from living
in the trees. It almost seems as though, to a certain extent, it had
retrograded. This retrogression appears in the fact that many of the
baboon’s characteristics are less ape-like and more dog-like than
other Old World monkeys and also because its hands and feet seem to
be specialized more in the direction of paws. Yet, in spite of this
backsliding on the part of the baboon, the monkeys of the Old World are
as a whole eminently more efficient in their actions and capacities
than any of the New World monkeys, the lemurs or tarsiers.
_Brains of the Old World Monkeys_
A question may arise concerning the relation in point of time which the
Old World monkeys bear to those of the New World. All of the evidence
supplied by fossils indicates that lemurs and tarsiers, as well as
the monkeys of South America and Central America, came into existence
long before those species which inhabit Africa and Asia. According to
most reliable records, the monkeys had their start some time early in
the Age of Mammals. It is correct, therefore, to look upon the Old
World monkeys as a later and higher stage of development in apedom.
This conclusion is borne out when we view the brains of the macaque
and the baboon. In this comparison we may be able to detect many signs
indicating improvements in the brain; in fact, all doubts may be set at
rest concerning the superiority of Old World monkeys.
If we look at the baboon’s brain we are impressed by the fact that it
has many more grooves and many more convolutions than the brain of the
South American monkey. The convolutions and the grooves of the brain
indicate the amount of cell space which the superbrain provides for
developing brain power. As between the baboon and the macaque, the
difference in this respect somewhat favours the former. This difference
is small and may perhaps be discounted by the fact that in macacus
the grooves have a slightly more advanced arrangement in consequence
of which certain departments of the superbrain show more progressive
tendencies than in the baboon. This is particularly true of the
department of hearing (temporal lobe) and the department of body and
contact senses (parietal lobe). Comparing the groove of Sylvius, whose
general angle furnishes such an important standard in rating a brain,
there is more of a backward tilting seen in this groove of the macaque
than in the baboon. Such an inclination is characteristic of higher
races. The central groove appears to be about on a par in both brains,
and the ape groove is likewise well developed both in the macaque and
the baboon. These three great boundary lines separate the four major
lobes of the superbrain. The department of sight in the occipital
lobe in macacus has no real advantage over the corresponding area in
the baboon. As already noted, the departments of hearing and of body
and contact sense are better organized and somewhat more expansive in
macacus than in baboon. But when we come to the preëminent part of
the superbrain, that portion in which the chief executive function is
located, namely, the frontal lobe, the baboon actually seems to have
some real advantage. Recalling the ugly disposition and ferocious
nature of this animal, we may question why he is superior in this
highest part of his brain to the lively and humorous little macaque.
It is unfortunate that we have not as yet any good psychological
studies of the baboon by which we may compare him with his more nimble
associates. Doubtless it is the disagreeable nature and uncompromising
aversion which the baboon has for mankind that make it so difficult to
estimate him psychologically. Yet there may be something of an enviable
consistency in the baboon’s aversion to man that implies a better type
of mental power than one might infer from the jabbering, ceaseless
activities of the macacus and all of the other bandar-logs. Some
explanation of this sort must at present suffice until we are possessed
of better standards for psychological comparison.
The two important structures on the base of the brain furnish a
definite idea of an animal’s rating. Accepting their evidence, it
appears at once that the bridge (_pons_) bears out our previous
observations concerning the powers of the superbrain. This evidence
gives the baboon a higher standing in intelligence than the macacus.
The value assigned to the bridge in the baboon is .164, while in the
macacus it is .150. This contrast gives an interesting corroborative
estimate of the superior mental powers of the baboon. From the figures
indicating the relative size of the pyramid, it would seem that the
macacus is somewhat more richly supplied in his variety of skillful
movements than the baboon. The figure in macacus is .147 and baboon
.143. While this is not a marked difference, it seems to indicate an
advantage probably derived from the more nimble and acrobatic actions
of the macacus. This animal has acquired a more highly efficient
mastery of tree life as compared with the more sluggish tendencies of
baboons, most of which prefer to live upon the ground and go about
like other four-legged animals. These contrasts between the Old World
monkeys are interesting for what they show in themselves. They give
rise to many questions which we would be glad to see answered by more
exact and extensive study. The reasons why the baboon or the macacus
should be endowed with superior qualities in one particular or another,
or why there should be corresponding improvements in the brain, are not
clear. There can be no doubt, however, that in the Old World monkeys as
a whole both behaviour and brain are in many respects superior to the
monkeys of the New World. We cannot fail to discern the special points
of this superiority in the brain. It seems impossible to avoid the
conclusion that when the Old World monkeys made their appearance they
definitely advanced the cause of progressive improvement and that from
this progress the brain profited as much as or even more than any other
part.
Turning back for a moment to the brains of the New World monkeys
and comparing them with those of the Old World group, we will find
sufficient evidence to convince us that the chief organ of the body was
surely on the way upward, and that the first humble steps taken by the
earliest members of monkey kind had been supplemented by further and
bold advances.