Physical Qualities of the Chimpanzee--His Social Habits--Mental
Characteristics
Physically considered, the chimpanzee very closely resembles man, but
there are certain points in which he differs both from man and from
other apes. We may notice a few of these points. The model of the
ear of the chimpanzee closely resembles that of man, but the organ
is larger in size and thinner in proportion. It is very sensitive to
sound, but dull to touch. The surface is not well provided with nerves.
He cannot erect his ear, as most animals do, by the use of the muscles
at the base; but, like the human ear, the muscles are useless, and in
this respect the ear is fixed and helpless.
The hand of the chimpanzee is long and narrow. The finger bones are
larger, in proportion to their size, than those of the human hand. One
thing peculiar to the hand of the chimpanzee is that the tendons inside
of the hand (those called the flexors), which are designed to close the
finders, are shorter than the line of the bones. On this account the
fingers of the ape are always held in a curve. He cannot straighten
them. This is probably due to the habit of climbing, in which he
indulges to such a great extent. He also indulges in the practice of
hanging suspended by the hands. In making his way through the bush
he often swings himself by the arms from bough to bough. Sometimes he
suspends himself by one arm, while he uses the other to pluck and eat
fruit. This characteristic is transmitted to the young, and is found in
the first stages of infancy. The thumb is not truly opposable, but is
inclined to close towards the palm of the hand. It is of little use to
him. His nails are thick, dark in color, and not quite so flat as those
of man.
The great toe, instead of being in line with the others, projects at
an angle from the side of the foot, something after the manner of the
human thumb. The foot itself is quite flexible and has great prehensile
power. In climbing, and in many other ways, it is used as a hand. The
tendons in the sole of the foot are equal in length to the line of the
bones, and the digits of the foot can be straightened; but from the
habitual use of them in climbing, the ape is predisposed to close the
digits, wherefore the foot is naturally inclined to curve into an arch,
especially in the line of the first and second digits.
His habit of walking is peculiar. The greater part of the weight is
borne upon the legs. The sole of the foot is placed almost flat on the
ground, but the pressure is greatest along the outer edge, in the line
of the last digit. This is easily noticed where he walks over plastic
ground. In the act of walking he always uses the hands, but he does
not place the palms on the ground. He uses the backs of the fingers
instead. Sometimes only the first joints or phalanges, resting upon the
nails, are placed on the ground. At other times the first and second
joints are used. I have seen one specimen that, when walking, employed
the backs of all his fingers, from the knuckles to the nails. The
integument on these parts is not callous, like that of the palm. The
color pigment is distributed the same as on other exposed parts of the
body. These facts show that the weight of the body is not borne on the
fore limbs, as it is in the case of a true quadruped, but indicate that
the hand is only used to balance the body while in the act of walking
and to shift the weight from foot to foot. The weight is, therefore,
not equally distributed between the hands and the feet, and the animal
cannot truly be said to be a quadruped in habit.
His waddling gait is caused by his short legs, stooping habit, and
heavy body. All animals having stout bodies and short legs are
predisposed to a waddling motion, which is due to the wide angle
between the weight and the changing center of gravity. This motion
is more conspicuous in bipeds than in quadrupeds, because the base
supporting the weight is reduced to a single point.
The chimpanzee is neither a true quadruped nor a true biped, but
combines the habits of both. It appears to be a transition state from
the former to the latter. Vestiges of this mixed habit are still to be
found in man. In the act of walking his arms alternate in motion with
his legs. This suggests the idea that he may have had, at some time, a
similar habit of locomotion. Such a fact does not necessarily show that
he was ever an ape, but it does point to the belief that he has once
occupied a horizon in nature like that now occupied by the ape, and
that having emerged from it, he still retains traces of the habit. This
peculiarity is still more easily observed in children than in adults.
In early infancy all children are inclined to be bow-legged. In their
first efforts at walking they invariably press most of their weight on
the outer edge of the foot and curve the toes inward, as if to grasp
the surface on which the foot is placed. The instinct of prehension
cannot be mistaken. It differs in degree in different races, and is
vastly more pronounced in negro infants than in white ones.
There is another peculiar feature in the walk of the chimpanzee. The
arms and legs do not alternate in motion with the same degree of
regularity that they do in man or quadrupeds. This ape uses his arms
more like crutches. They are moved forward, not quite, but almost at
the same instant, and the motion of the legs is not at equal intervals.
To be more explicit: the hands are placed almost opposite each other;
the right foot is advanced about three times its length; the left
foot is then placed about one length in front of the right; the arms
are again moved; the right foot is again advanced about three lengths
forward of the left; and the left again brought about one length in
front of that. The same animal does not always use the same foot to
make the long stride. It will be seen by this that each foot moves
through the same space, and that, in a line, the tracks of either foot
are the same distance apart; but the distance from the track of the
right foot to that of the left is about three times as great as the
distance from the track of the left foot to that of the right. Or the
reverse may be the case. The distance from the track of either foot to
the succeeding track of the other is never the same between the right
and left tracks, except where the animal is walking at great leisure.
There is, perhaps, no animal more awkward than the chimpanzee, when he
attempts to run. He sometimes swings his body with such force between
his arms as to lose his balance and fall backward on the ground.
Sometimes when he rights himself again, he is half his length backward
of his starting point.
The chimpanzee is doubtless a better climber than the gorilla. He finds
much of his food in trees; but he is not, in the proper sense of the
term, arboreal. To be arboreal, the animal must be able to sleep in a
tree or on a perch. The chimpanzee cannot do so. He sleeps the same as
a human being does. He lies down on his back or side, and frequently
uses his arms for a pillow. I do not believe it possible for him to
sleep on a perch. He may sometimes doze in that way, but the grasp of
his foot is only brought into use when he is conscious. I have often
known Moses to climb down from the trees and lie upon the ground to
take a nap. I never saw him so much as doze in any other position.
I may here call attention to one fact concerning the arboreal habit.
There appears to be a rule to which this habit conforms. Among apes
and monkeys the habit is in keeping with the size of the animal. The
largest monkeys are found only among the lowest trees, and the small
monkeys among the taller trees. It is a rare thing to see a large
monkey in the top of a tall tree. He may venture there for food or
to make his escape, but it is not his proper element. The same rule
appears to hold good among the apes. The gibbon has the arboreal
habit in a more pronounced degree than any other true ape. The orang
appears to be next; the chimpanzee comes in for third place, and the
gorilla last. It must not be understood that all of these apes do not
frequently climb, even to the tops of the highest trees; but that is
not their normal mode of life, any more than the top of a mast is the
habitual place for a sailor on a ship.
The chimpanzee is nomadic in habit, and, like the gorilla, seldom or
never passes two nights in the same spot. As to his building huts or
nests in trees or elsewhere, I am not prepared to believe that he ever
does that. For months I hunted in vain and made diligent inquiry in
several tribes, but failed to find a specimen of any kind of shelter
built by an ape. I do not assert that it is absolutely untrue that he
does this, but I have never been able to obtain any evidence of it,
except the statement of the natives. On the contrary, certain facts
point to the opposite belief. If the ape built himself a permanent
home, the natives would soon discover it and there would be no
difficulty in having it pointed out. If he built a new one every night,
however rude and primitive it might be, there would be so many of them
in the forest that there would be no difficulty in finding them. The
nomadic habit plainly shows that he does not build the former kind, and
the utter absence of them shows that he does not build the latter kind.
The whole story appears to be without foundation.
In addition to these facts, one thing to be noticed is that few or none
of the mammals of the tropics ever build any kind of home. The animals
that in other climates have the habit of burrowing do not appear to
do so in the tropics, This is due, no doubt, to the warm climate, in
which they are not in need of shelter. Of course birds and other
oviparous animals build nests, as they do elsewhere. The period of
incubation makes this necessary.
The longevity of these apes is largely a matter of conjecture, but
from a cursory study of their dentition and other facts of their
development, it appears that the male reaches the adult stage at an
age ranging from eight to ten years, while the female matures between
six and eight. These appear to be the periods at which they pass from
the state of adolescence. Some of them live to be perhaps forty years
of age, or upwards, but the average life is probably not more than
twenty-one to twenty-three years. The average of life is, doubtless,
more uniform with them than with man. These figures are not mere
guesswork, but are deduced from reliable data.
The period of gestation in both these apes is a matter that cannot be
stated with certainty. Some of the natives say that it is nine months,
while others believe that it is seven months or less. There are some
facts to support each of these claims, but nothing is quite conclusive.
The sum of the evidence that I could find rather points to a term of
four and a half months, or thereabouts, as the true period. During
the months of January and February the male gorillas are vociferous
in their screaming, the young adults separate from the families, and
other things indicate that this is the season of pairing and breeding.
They may not be strictly confined to this period, but the inference
that they are so is well founded. It is quite certain that the season
of bearing the young is from the beginning of May to the end of June.
It is about this time that the dry season begins, and it continues
for four months. It would appear that nature has selected this period
of the year because it is more favorable for rearing the young. During
this season food is more abundant and can be secured with less effort.
The lowlands are drier, and this enables the mother to retire with her
young to the dense jungle, where she is less exposed to danger than
she would be in the more open forest. It is uncertain whether or not
the periods are the same with both apes. Native reports differ on this
point. But it is probable that they are the same. The average of this
season is about four and a half moons, or eighteen weeks.
From a social point of view the chimpanzee appears to be of a little
higher caste than other apes. In his marital ideas he is polygamous,
but is in a certain degree loyal to his family. The paternal instinct
is a trifle more refined in him than in other simians. He seems to
appreciate better the relationship of parent and child and to retain
it longer than others do. Most male animals become estranged from
their young and discard them at a very early age. The chimpanzee keeps
his children with him until they are old enough to go away and rear
families of their own.
The family of the chimpanzee frequently consists of three or four wives
and ten or twelve children, with one adult male. There are known cases
in which two or three adult males have been seen in the same family,
but each one having his own wives and children. In such an event there
seems to be one who is supreme. This fact suggests the idea that
among them a form of patriarchal government prevails. The wives and
children do not apparently question the authority of the patriarch or
rebel against it. The male parent often plays with his children and is
seemingly very fond of them.
There is one universal error that I desire here to correct. It is the
common idea that animals are so strongly possessed of the paternal
instinct that they nobly sacrifice their own lives in defense of their
young. I do not wish to dispel any belief that tends to dignify or
ennoble animals, for I am their friend and champion. But truth demands
that this statement be qualified. It is quite true that many have
lost their lives in such acts of defense, but it was not a voluntary
sacrifice. It is not alone in the defense of their young, but in many
cases it is an act of self-defense. In other instances it is from a
lack of judgment. These apes have often been frightened away from
their young and the latter captured while the parents were fleeing
from the scene. This may have been the result of sagacity rather than
of depravity; but the parental instinct in both sexes and in many
instances has failed to restrain them from flight. If it be a foe
that appears to come within the measure of their own power, they will
defend their young, and this sometimes results in the loss of their own
lives; but if it be one of such formidable aspect as to appear quite
invincible, the parents leave the young to their fate. This is true of
all animals, including mankind.
I have no desire to detract from the heroic quality of this instinct
or to dim the glory it sheds upon the noble deeds ascribed to it, but
the fact that a parent incurs the risk of its own life in the defense
of its young is not a true test of the strength or quality of this
instinct. It is only in the few isolated cases of a voluntary sacrifice
of the parent, foreknowing the result, that it can be said the act was
due to instinct. In most such cases the parent acts under a belief
in its own ability to rescue the one in danger, the parent not being
wholly aware of its own peril. I doubt if any animal except man ever
deliberately offered its own life as a ransom for that of another. Such
instances in human history are so rare as to immortalize the actor.
To whatever extent the instinct may be found, it is much stronger in
the female than in the male, and it appears to be stronger in domestic
animals than in wild ones. To what extent this is due to their contact
with man, it is difficult to say. The germ may be inherent, but it
responds to culture.
The fact that the ape deserts its offspring under certain conditions
may be taken as an evidence of superior intelligence affording it a
higher appreciation of life and danger, rather than a low, brutish
impulse. It is the exercise of superior judgment that causes man to act
with more prudence than other animals. It does not detract from his
nobleness.
Within the family circle of the chimpanzee the father is supreme;
but he does not degrade his royalty by being a tyrant. Each member
of the family seems to have certain rights that are not impugned by
others. Possession is the right of ownership. When one ape procures
a certain article of food, the others do not try to dispossess him.
It is probably from this source that man inherits the idea of private
ownership. It is the same principle, amplified, by which nations claim
the right of territory. Nations often violate this right, and so do
chimpanzees, when not held in check by something more potent than a
mere abstract sense of justice. With all due respect, I do not think
the ape so much abuses the right by urging his claim beyond his real
needs as nations sometimes do.
When a member of a family of apes is ill, the others are quite
conscious of the fact and evince a certain amount of solicitude. Their
conduct indicates that they have, in a small degree, the passion of
sympathy, but the emotion is feeble and wavering. So far as I know,
they do not essay any treatment, except to soothe and comfort the
sufferer. They surely have some definite idea of what death is, and
I have sometimes had reason to believe that they have a name for it.
They do not readily abandon their sick, but when one of them is unable
to travel with the band the others rove about for days, keeping within
call of it; but they do not minister to its wants. It is said that if
one of them is wounded the others will rescue it if possible and convey
it to a place of safety. I cannot vouch for this, as such an incident
has never come within my own experience.
One of the most remarkable of all the social habits of the chimpanzee
is the _kanjo_, as it is called in the native tongue. The word does
not mean “dance” in the sense of saltatory gyrations, but it implies
more the idea of “carnival.” It is believed that more than one family
take part in these festivities. Here and there in the jungle is found
a small spot of sonorous earth. It is irregular in shape and about two
feet across. The surface is of clay and is artificial. The clay is
superimposed upon a kind of peat bed, which, being porous, acts as a
resonance cavity and intensifies the sound. This constitutes a kind of
drum. It yields rather a dead sound, but this is of considerable volume.
[Illustration: KANJO NTYIGO-CHIMPANZEE DANCE]
This queer drum is thus made by the chimpanzees. They secure the clay
along the banks of some stream in the vicinity. They carry it by hand,
deposit it while in a plastic state, spread it over the place selected,
and let it dry. I have placed in the museum of Buffalo, N. Y., a part
of one of these drums that I brought home with me from the Nkami
forest. It shows the finger-prints of the apes. They were impressed in
it while the mud was yet soft.
After the drum is quite dry, the chimpanzees assemble by night in great
numbers and the carnival begins. One or two of them beat violently on
this dry clay, while others jump up and down in a wild and grotesque
manner. Some of them utter long, rolling sounds, as if trying to sing.
When one tires of beating the drum, another relieves him, and in this
fashion the festivities continue for hours. I know of nothing like this
in the social system of any other animal, but what it signifies or what
its origin was is quite beyond my knowledge. They do not indulge in
this _kanjo_ in all parts of their domain, nor does it occur at regular
intervals.
The chimpanzee is averse to solitude. He is fond of the society of man
and is, therefore, easily domesticated. If allowed to go at liberty,
he is well disposed, and is strongly attached to man. If confined, he
becomes vicious and ill-tempered. All animals, including man, have the
same tendency. Mentally the chimpanzee occupies a high plane within
his own sphere of life, but within those limits the faculties of the
mind are not called into frequent exercise and, therefore, they are not
so active as they are in man.
It is difficult to compare the mental status of the ape to that of
man, because there is no common basis upon which the two rest. Their
modes of life are so unlike as to afford no common unit of measure.
Their faculties are developed along different lines. The two have but
few problems in common to solve. While the scope of the human mind
is vastly wider than that of the ape, it does not follow that it can
act in all things with more precision. There are, perhaps, instances
in which the mind of the ape excels that of man by reason of its
adaptation to certain conditions. It is not a safe and infallible guide
to measure all things by the standard of man’s opinion of himself.
It is quite true that, by such a unit of measure, the comparison is
much in favor of man; but the conclusion is neither just nor adequate.
It is a problem of great interest, however, to compare them in this
manner, and the result indicates that a fair specimen of adult ape
is in about the same mental horizon as a child of one year old. But
if the operation were reversed and man were placed under the natural
conditions of the ape, the comparison would prove much less in favor of
man. There is no common mental unit between them.
On problems that concern his own comfort or safety the chimpanzee
exercises the faculty of reason with a fair degree of precision. He
is quick to interpret motives or to discern intents, and he is a rare
judge of character. He is inquisitive, but not so imitative as monkeys
are. He is more observant of the relations of cause and effect. In his
actions he is controlled by more definite motives. He is docile and
quickly learns anything that lies within the range of his own mental
plane.
The opinion has long prevailed that these apes subsist upon a vegetable
diet. That is a mistake. In this respect their habits are much the same
as those of man, except that the latter has learned to cook, but the
former eats his food raw. Their natural tastes are greatly diversified,
and they are not all equally fond of the same articles of food. Most
of them are partial to the wild mango, which grows in abundance in
certain localities in the forest. This is often available when other
kinds of food are scarce. It thus becomes, as it were, a staple article
of food. There are many kinds of nuts to be found in their domain, but
the nut of the oil palm is a great favorite. They sometimes eat the
kola nut, but they are not partial to it. Several kinds of small fruits
and berries also form part of their diet. They eat the stalks of some
plants, the tender buds of others, and the tendrils of certain vines.
The names of these vines I do not know.
Most of the fruits and plants that are relished by them are either
acidulous or bitter in taste. They are not especially fond of sweet
fruits. They prefer those having the flavors mentioned. They eat
bananas, pineapples, or other sweet fruits, but rarely do so from
choice. Most of them appear to prefer a lime to an orange, a plantain
to a banana, a kola nut to a sweet mango. In captivity they acquire a
taste for sweet foods of all kinds.
In addition to these articles they devour birds, lizards, and small
rodents. They rob birds of their eggs and their young. They make havoc
of many kinds of large insects. Those that I have owned were fond of
cooked meats and salt fish, either raw or cooked.