Popular Science Monthly/Volume 30/November 1886/The Mental Faculties of Monkeys



WHEN we compare the mental faculties and social instincts of animals, even of monkeys, with those of the superior races of civilized men, the distance seems immeasurable, and to fill the gap impossible. But, if we take the lower races of mankind, the differences appear less marked, and even analogies arise. Many of the moral and mental faculties, in fact, which we observe among the quadrumana appear common to them with savage peoples on the one side, and with some of the higher mammalia on the other side, which have well-developed social instincts—with, for instance, dogs, horses, and elephants. The animals which man has domesticated are, as a rule, those which belong to social species, and live in the natural state in more or less numerous groups. And, among the monkeys, it is not the large ones, those which most resemble men in stature, that are most social and most susceptible of domestication, but the smaller ones, the tree-climbers.

The gorilla, of Western Africa, lives in patriarchal and polygamous families, in which many females and their young submit to the authority of a single adult, and the habits of the chimpanzee are similar; but the Cynocephalæ, most of the smaller species of the African. Continent, and American monkeys, live in considerable troops, in a kind of general sexual promiscuity, in which the love of the mothers for their young, very strong while they need it in their weakness, does not outlive their growth out of helpless infancy. Similar habits have been noticed among some savage races; and traditions are preserved among many people of a time when family bonds did not exist. But traces of more durable family bonds between monkeys of the same blood seem to exist among the chimpanzees and gorillas, where the appearance of particular and exclusive affection is combined with rivalry with the members of other families. Savage, in the "Boston Journal of Natural History," tells of a female chimpanzee which was observed in a tree with the male and a pair of young of different sexes. She first started to hurry down and run into the thicket with the male and the young female; but, seeing the young male left behind, she went back for him and had taken him in her arms when she was shot. Houzeau, in his "Études" ("Studies on the Mental Faculties of Animals as compared with those of Men"), compares this trait with the indifference with which the New Zealand mother saw Cook take away her son, probably forever, as she was expressly informed. Houzeau also finds traces of paternal affection in the protection that old anthropoid apes accord to the members of the polygamous tribe of which they are chiefs. This kind of affection can, however, hardly be said to exist among all men. There are numerous tribes in which the fathers do not know their own children, in which the names pass in the female line, and where a man's heirs are the children of his sisters. Striking examples of conjugal love are sometimes shown among monogamous monkeys. An incident in point is that of a female of an American species which, tired of holding her young one, called up the male to relieve her. Another story is that of the male in the Jardin des Plantes which became inconsolable and starved itself to death after its companion died.

In the way of language, monkeys manifest their passions, emotions, desires, and fears, by cries and gestures, emphasized by significant accents, which vary with the species. Monkeys and children, together with savages and uneducated people of civilized nations, manifest an inclination to mimic the gestures and motions of all persons whom they see. We think that this trait is especially prominent in monkeys, but thousands of instances might be cited to show that mankind, old and young, shares it with them. The attitude and the sagacity of monkeys are so human that some savages believe that it is out of maliciousness that they do not talk. In fact, a monkey might pass for a dumb man, because he does not articulate the consonants clearly, as we do; but not all men have this power of articulation in an equal degree. We have stammerers by birth and by habit. Some savage tribes have a scanty alphabet complicated by clicks and nasal and guttural sounds that can not be imagined till they are heard. All monkeys have voices, and many of them have very strong ones. Excepting the solitary and taciturn orang-outang, the species which live in troops are chatterers, and keep up a great hubbub. The principal tones of their noisy and rapid language, with the frequent repetitions of the same sounds, may also be found in the languages of the most savage peoples. They are, for the most part, complex, guttural, and harsh articulations, with few variations. But the alphabets of some of the African and Melanesian nations are not much richer. In both, it is generally the labials which are wanting. Laughter is not wholly peculiar to men, for some monkeys have a noisy and expansive laugh analogous to ours. Cook has stated that natives of the New Hebrides express their joy by a kind of guttural whistle, analogous to the jerky, rattling laugh of some monkeys. Monkeys are also capable of showing sorrow and weeping; and it is possible to follow on their faces the equivalents of the physiognomical changes which in man answer to the expression of his various emotions. Among these are the drawing back of the corners of the mouth and the contraction of the lower eyelid, which constitute the monkey's smile, and the depression of the eyebrow and forehead in anger.

It can hardly be doubted at this day that monkeys have collective feasts, which Houzeau compares with the new-moon festivals of the negroes, Hottentots, and Papuans. Such assemblies take place among South American monkeys, when, having eaten up the resources of one place, they are about to emigrate to another. Duvancel witnessed, at Deobund, in India, a great meeting of monkeys, which the natives said took place regularly, after intervals of several years. They came up by thousands, from different directions, all marching with sticks in their hands. Arrived at the place of meeting, they threw their sticks into a great pile.

The feasts of the black chimpanzees of Africa are more like those of the negroes. The animals come together, it may be, fifty at a time, leaping, shouting, and drumming on old logs with sticks which they hold in their hands and feet. They are taking their first lessons in music, as it were; and it is remarkable that that music is upon the most rudimentary form of a drum, which is, besides, the universal primitive musical instrument of the lowest savage human races, and the only one which many of them possess. Tamed monkeys can beat the drum and play with castanets.

If we may believe popular stories, the quadrumana have some kind of funeral ceremonies. The Chinese Pharmacopœia speaks of a species of which, when any one of the band dies, all the others attend his funeral. A somewhat similar story, in which the dead monkey is covered with branches of trees, is told in "Purchas's Pilgrimmes"—a work which, however, is not of the highest scientific authority. But, however exaggerated these stories may be, it is not probable that monkeys are wholly indifferent to the death of their fellows—at least that they are less concerned than those Caffres who bury only the bodies of their chiefs and their children.

Leadership among gorillas is decided by the law of the strongest. When the young gorillas become able, they put the old chiefs out of the way, and themselves take their places. So savage tribes dispatch their old men when they are no longer of use, or when they stand in the way of some ambitious aspirant. Monkeys fight by striking and clinching with their hands, and by trying to bite; they will clinch one another just as athletes do. The gorilla, coming down on its enemy, utters a cry like the war-cry of savages, and strikes upon its chest with its hands, as Houzeau says athletes frequently do. When attacked by an armed man, it aims to seize his gun or his club, and having got it tries to break it; but it does not try to use it as the man does. Other monkeys try to avoid man, but when attacked by him defend themselves courageously and throw stones and sticks at him; if they are on trees, breaking off limbs and fruits and nuts, and whatever they can put their hands upon. The primitive arms of mankind are likewise projectiles thrown by the hand like the Australian boomerang and the Indian's tomahawk, club, or lance. Free as monkeys are in throwing sticks, they do not seem to have ever come to the point of using their weapons as clubs or lances; and it is not consistent with their organization and habits that they should do so. Their fortresses are tree-tops, from which flying sticks and stones can do great execution, but to fight with clubs and lances they would have to stand upon the ground, where they would be at a great disadvantage. Both races, then, have chosen or evolved the weapons best suited to their anatomical organization. The habits of streetboys still show that man's first weapon-using instinct was to throw stones; and with this in view we can fancy the early battles when throngs of men fought by throwing showers of stones up into the trees at the monkeys, who, in their turn, threw branches down at them. Very few animals besides men and monkeys throw projectiles, but that is because they are the only ones that have prehensile hands. But elephants when angry will break down branches and pull up saplings with their trunks; and the ostrich kicks stones behind itself at the faces of its pursuers. It is the anatomical organization of the animal that determines its choice of arms.

Monkeys are susceptible of showing spontaneous preferences and friendships for others, even outside of their species, and can be, in their affections for human companions, as capricious as children. They share in man's aversion to snakes. In a state of nature they appear to manifest aversion and hostility to other animals, and particularly to other species of quadrumana. Orang-outangs exhibit an instinctive animosity against other monkeys, and assail them in every way. The tribe as a whole exhibit anger by nearly the same kind of acts as men do. A chimpanzee of Du Chaillu's had marked preferences for particular things that were served at the table, and, when given other than what it desired, became irritated, threw down what was offered it, stamped its feet and uttered a peculiar cry, and acted, Du Chaillu says, just as a spoiled child would have done. A friend of the author, who had a little monkey, and was studying its instincts, said of it: "It is a badly brought-up child. It has all such a child's faults, and is intelligent enough to know when it is disobeying, and to hide itself when it intends to disobey." Dr. Abel's orang-outang showed its anger, when refused what it wanted, by rolling on the ground like a mad child and screaming, and would then go off and hide. The apes which Adanson chased in the forests of Senegal knit their eyebrows, gritted their teeth, and screamed; and the monkeys in the Jardin des Plantes and the Jardin d'Acclimatation, when irritated by the refusal of anything that has been tantalizingly shown them, throw themselves upon the gratings, make their ugliest faces, show their teeth, and scream and mutter.

"Greedy as a monkey" is a vulgar expression. Houzeau says that those persons who assert that monkeys will not have to do again with intoxicating drinks after having once been made their victims were more desirous of teaching a moral lesson than of telling the exact truth. Most tamed monkeys are ready enough to drink wine and brandy, and will help themselves to them. They like to get tipsy, and will indulge themselves whenever they can, in spite of chastisements. Their intoxication is characterized by the same symptoms as man's—weak knees, thick tongue, and unsteady movements. This identity of the effects of intoxication extends to other animals: asses and horses have been seen drunk; and dogs, which generally refuse wine, can be made to accept alcoholic drinks if they are sufficiently diluted and sweetened; while, as we have seen, monkeys of different species often exhibit antipathies to one another, those of the same species will assist one another, provided they are not sexual rivals. This trait of mutual helpfulness appears to exist in all animals that have organs of prehension—as among the climbing birds and those insects which have mandibles. The instinct is quite well developed among monkeys, and those of the same family or troop exhibit traits of mutual assistance that might be very properly compared with those shown by men in their relations with one another. The monkeys in Sumatra, according to Cesare Moreno, are very troublesome in the gardens, and even in houses, when they can find entrance into them; and no kind of inclosure seems adequate to protect fruits and vegetables from their depredations. Forming a line in order to pass their spoil from hand to hand, they scale the walls, enter at the doors or windows, and leisurely pillage all that they can find. Then they retire to the woods, to dress themselves up in the gayly colored cloths which they may have stolen, while they have a particular fancy for whatever will give a metallic reflection. They will divide their trinkets among one another, or quarrel about them, and dress themselves up in them in a grotesque style; and then, like children, having become tired of them, will leave them hanging on the branches or let them fall to the ground, and care no more for them. They seem to be thieves by instinct, for the mere pleasure of stealing, when they are not catering to their appetites; and they are capable of sacking a house and carrying off everything movable in it with the system and concert of a band of robbers. They observe a kind of discipline in their operations, and post their scouts, to inform them in season when it is time to run away; and this, when warned, they can do with wonderful simultaneousness.

Uiloa saw monkeys joining hands, six or eight together, to ford rivers. Dampier tells a very interesting story of the performances in this line of the monkeys of the Isthmus of Panama. We can see monkeys repeating the same exercise on a small scale for amusement in zoölogical gardens.

Travelers say that monkeys take up those of their number which are wounded in their battles. Savage observed the same thing done for chimpanzees when they were shot, and says that, when the wound does not immediately produce death, his fellows have been seen to put their hands over it to stop its bleeding, and, if this did not succeed, to apply leaves and sod. Houzeau relates an analogous story on the authority of the New-Hebrides islanders.

As men appropriate particular territories to themselves to the exclusion of all others, so the larger monkeys will drive away other animals from grounds they wish to occupy, with an efficiency that speaks well for their discipline and tactics.

The acuteness of the perception of domestic animals to approaching danger is well known. Monkeys exhibit it in an equal degree. Le Vaillant says that the bavian which went with him into Africa was his most trustworthy guardian, and signalized the approach of the slightest danger, whether by day or by night, even before the dogs could discover it; while the dogs acknowledged it their superior in this faculty, and at its look or nod would spring to this side or that, according as it indicated. The same monkey, though tamed, would answer the cries of the wild ones of its species when it heard them in the woods, but was afraid of them when it saw them. All travelers testify to the intelligence of monkeys in a wild state, and have much to say of the trouble they have in guarding against their devices. It is not considered safe to attack their troops, for they will defend themselves in concert and with energy, and in apparent security, from the tree-tops, where they are afraid of nothing but a gun.

The curiosity of animals is not always passive, and the attentive attitude they show is not always the effect of astonishment. They like to imitate, and to imitate they must observe. An orang-outang in the Jardin des Plantes, in Paris, being one day visited by Flourens and Geoffroy Saint-Hilaire, observed the latter with earnest attention. As soon as it had thoroughly studied its visitor, it took a cane, bent itself over like an old man, and imitated his gait. Another orang-outang had learned how to get upon a chair and open a door-latch, which was otherwise out of its reach. The chair it was accustomed to use having been taken away, it went and got another from the corner, brought it to the door, and mounted it. Houzeau regards these facts as indicating the existence of an inventive faculty, of a decided intention looking to a fixed end, and a perception of the relation of cause and effect, A black chimpanzee of Buffon's knew how to unlock the door, and, if it did not find the key in the lock, would look for it. This monkey took its meals like a well-bred person, ate with a spoon and fork, used a plate, and served itself with wine. The anthropoid ape Mafuka, in the Zoölogical Garden of Dresden, knew all about the way to open the door of its cage. It would steal the key and hide it under its arm till it wanted to use it. At one time, after watching a carpenter at work, it got his gimlet and bored holes in its table. At meals it filled its own cup from the pitcher, and took care not to let it run over.

Mr. Cobs gave his young orang-outang half an orange, put the other half in a cupboard, and lay down on the sofa. Remarking some peculiarity in the movements of the orang, he pretended to be asleep. The animal came cautiously up to him to assure itself that he was asleep, then climbed upon the cupboard, took the rest of the orange and ate it, hid the peel carefully under the sticks in the fire-place, and then itself lay down. Such manner of action, says Tylor, can hardly be explained except by a train of thoughts supposing the existence of what among ourselves we call reason.

Bennett had to chide a young gibbon many times for putting things out of their places, among other things a cake of soap. One morning when he was writing he observed the monkey taking the soap, and watched its operations in such a manner that he should not himself be observed. Seeing him apparently occupied with his writing, the monkey went off with the soap in its hand. When it had got to the middle of the cabin, Bennett spoke to it in such a manner as not to startle it. When it perceived that it had been seen, it returned and put the soap in very nearly the place from which it had taken it.

Monkeys seem well adapted to perform some kinds of domestic offices, and acquit themselves gracefully in them. The natives of Madagascar train the short-tailed lemur for hunting, where it renders the same services as a dog. Pyrard says that in his time the colonists of Sierra Leone employed chimpanzees in carrying water and beating in mortars. They would carry the water in jars on their heads, but would drop their burdens if some one was not at hand to relieve them from the load, Acosta tells of a monkey belonging to the Governor of Cartagena, which they were accustomed to send with a bottle and money to the wine-merchant's. It would never give up its money till it had got its wine, and would never touch that, although it was fond of it. Père Vincent Maria, procurator of the bare-footed Carmelites in the Indian Peninsula, tells of a Macacus silenus which imitated perfectly all the acts which it was shown how to perform. It would go at it so seriously and exactly that one could not help being surprised to see an animal do it all so well. Breton has in his Chinese pictures a representation of monkeys of one of the smaller species gathering tea-leaves on the tops of one of the steep ridges of Chansung. Williams doubts the truth of the story, but there is nothing in it outside of the probabilities. The ancient Egyptians obtained considerable services from the Cynocephalus.

Du Grandpré, of the French marine, speaks of a female chimpanzee that would heat the furnace on board the vessel. It was able to judge when the required degree of heat was reached, and would call the cook at the right moment. It would join the sailors in turning the capstan, would go on the yards with them, could pull ropes as well as any, and, observing that the ends were tied to keep them from hanging down, tied the ends which she held. Buffon mentions another female at Loango which could make the beds, sweep the house, and help turn the spit.

These monkeys had to be tamed before they could be taught; but, as they breed in captivity, Houzeau suggests that there is little doubt that the principal species are susceptible of domestication. Then it will only be necessary to train individuals for their special work. "Female monkeys," he adds, "might be employed in taking care of children. They would make excellent nurses, for their milk is rich in butter (ten per cent). These facts can hardly fail in time to strike the residents of European origin in Asia and Africa, where these animals are easy to get. We anticipate a time when these races, bred by man, will render great services in daily life and industry, and will contribute to the general progress. There is nothing in such a prediction which does not rest on scientific premises, and nothing in it to laugh at."—Translated for the Popular Science Monthly from the Revue Scientifique.