CHAPTER II.
MARRIAGE AND THE FAMILY AMONGST ANIMALS.
I. The preservation of species.—Two great processes of preservation—Different rôles of the male and the female in the animal family.
II. Marriage and the rearing of the young among animals.—Abandonment of the young in the inferior species—The superior molluscs guard their eggs—Solicitude of spiders for their eggs and their young—Instinctive foresight of insects—Its origin—Larvæ are ancestral forms—The familial instinct amongst birds—Frequency of monogamy amongst birds.
III. The family amongst animals.—Intoxication of egg-laying with birds—Absence of paternal love in certain birds—The familial instinct very developed in certain species—Transient nature of their love for the young—Promiscuity, polygamy, and monogamy among mammals—Hordes of sociable animals—Polygamous monkeys—Monogamous monkeys—General observations.
I. The Preservation of Species.
Two great processes are employed in the animal kingdom to assure the preservation of the species: either the parents do not concern themselves at all with their progeny, in which case the females give birth to an enormous number of young; or, on the other hand, they are full of solicitude for their offspring, cherishing and protecting them against the numerous dangers that menace them; and, in this last case, the young are few in number. Nature (since the expression is consecrated) proceeds sometimes by a lavish and lawless production, and sometimes by a sort of Malthusianism. Thus a cod lays every year about a million eggs, on which she bestows no care, and of which only the thousandth, or perhaps even the hundred thousandth part, escapes destruction; turtle-doves, on the contrary, only lay two eggs, but nearly all their young attain maturity. In short, the species is maintained sometimes by prodigality of births and sometimes by a great expenditure of care and affection on the part of the parents, especially of the female. It is almost superfluous to remark that analogous facts are observed in human natality, according as it is savage or civilised.
With animals, as with men, sexual association, when it endures, becomes marriage, and results in the family, that is to say, a union of parents for the purpose of protecting their young. The care of the male for his progeny is more rare and tardy than that of the female. Among animals, as among men, the family is at first matriarchal, and it is only in the higher stages of the animal kingdom that the male becomes a truly constituent part of the family group; but even then, except among certain species of birds, his chief care is less to rear the young than to govern in order to protect them. He plays the rôle of a despotic chief, guiding the family when it remains undivided after the rearing of the young, and most frequently acting like a polygamous sultan, without the purely human scruple in regard to incest.
Just as we find amongst animals the two principal types of the human family, the matriarchate and the patriarchate, or rather the maternal and paternal family, so we may observe equally among them all the forms of sexual union from promiscuity up to monogamy; but for enlightenment on these interesting points of sociology, a rapid examination of the animal kingdom is worth far more than all generalities.
II. Marriage and the Rearing of Young amongst Animals.
We shall leave entirely unnoticed the inferior kingdom of zoophytes, which are devoid of coalescing nervous centres, and consequently of conscious life. Even the lower types of molluscs do not begin to think of their progeny; they scatter their eggs as plants do their seeds, and leave them exposed to all chances. We must go to the superior molluscs to see any care of offspring awakening. In this order, indeed, the most highly developed species watch more or less over their eggs. The taredos carry them stuck together in rings round their bodies; snails often deposit them in damp ground, or in the trunk of a tree; cephalopods fix them in clusters round algæ, and sometimes watch them till they open, after which they leave them to get on as they can in the great world.
With spiders and insects the eggs are often the object of a solicitude and even prolonged forethought, which rejoice greatly the lovers of design. We must observe, however, that the males of spiders and that of the greater number of insects entirely neglect their young; it is again in the female that the care for offspring first awakens. And this is natural, for the eggs have been formed in her body; she has laid them, and has been conscious of them; they form, in a way, an integral part of her individuality.
The females of spiders also take care of their eggs after laying them, enclose them in a ball of thread arranged in cocoons, carry them about with them, and at the moment of hatching set them free, one by one, from the envelope. Amongst some species there is even a certain rearing of the young. Thus the Nemesia Eleonora lives for some time in her trapped nest with her young, numbering from twenty to forty.[29]
With insects maternal forethought sometimes amounts to a sort of divining prescience, which the doctrine of evolution alone can explain. There is really something wonderful in the actions of a female insect, as she prepares for her descendants, whom she will never see any more than she has seen her own parents, a special nourishment which differs from her own. It is thus that the sphinx, the pompilus, the sand-wasp, and the philanthus dig holes in the sand, in which they deposit with the eggs a suitable food for the future larvæ.[30]
In order to understand these facts, apparently so inexplicable, we must look not only to the powerful influence of selection, but also to the zoögenic past of the species. With the insect the perfect form is always the last which it assumes, the outcome of all the previous metamorphoses. But the larval form, though actually transitory, must have been for a long time the permanent form, and it had different tastes and needs. At the present time there are still numbers of insects whose larval existence has a much longer duration than that of the so-called perfect insect (May-flies, cockchafers). There are even larvæ which reproduce themselves. Certain others, even though sterile, have not lost the maternal instinct. Thus at the time of the hatching of the nymphs the larvæ of the termites assist the latter to get rid of their envelope. It is therefore probable that, though now transitory, the larval forms of insects have formerly been permanent; they represent ancestral types, which evolution has by degrees metamorphosed into insects that we call perfect. The larvæ, now actually sterile, descend from ancestors which were not so, and in the larvæ of certain species the maternal instinct has survived the reproductive function.[31]
This is doubtless the case with bees and ants; their workers must represent an ancestral form, having preserved the maternal fervour of its anterior state; the winged form, on the contrary, must be relatively recent. It even appears probable that in the republics of ants and bees the laborious workers may have succeeded, in a certain way, in getting rid of sexual needs which cause animals and even men to commit so many mad actions. With them the old maternal instinct has taken the place ceded to it by sexual instinct, and has become enlarged and ennobled. Their affection is no longer exclusively confined to a few individuals produced from their own bowels, but is shared by all the young of the association. In their sub-œsophagian ganglion one care takes precedence of all others—the care of rearing the young. This is their constant occupation and the great duty to which they sacrifice their lives. Maternal love, usually so selfish, expands with them into an all-embracing social affection. It is not impossible that a psychic metamorphosis of the same kind may one day take place in future human societies.
It would even seem that the workers appreciate the faculty of reproduction all the more for being deprived of it. The queen bee, or rather the fertile female, who is the common mother of all the tribe, has every possible care lavished on her, and is publicly mourned when she dies. If she happens to perish before having young, and then cannot be replaced, the virgin workers despair of the republic; losing for ever “les longs espoirs et les vastes pensées,” they give way to an incurable and mortal pessimism.
One primitive form of the family, the matriarchate, which we shall study later, is realised, even in an exaggerated form, by ants and bees. In human societies we shall only find very faint imitations of this system, which has been so strictly carried out by the primates of the invertebrates, and which seems to have inspired the ancients with their fables about the amazons.
The vertebrated species, with the exception of mankind, have founded no society that can be even distantly compared to that of hymenoptera and of ants. With nearly all fishes and amphibia the parents are very poorly developed as regards consciousness, and take no care of their eggs after fecundation. Some species of fishes are, however, endowed with a certain familial instinct, and strange to say, here it is the male who tends his offspring. So true is it, that the imaginary being called Nature has no preference for any special methods, and that in her eyes all processes are good on the one condition that they succeed! Thus the Chinese Macropus gathers the fecundated eggs into his jaws, deposits them in the midst of the froth and mucous exuding from his mouth, and watches over the young when they are hatched.[32] The male of synagnathous fishes and the sea-horses carry their eggs in an incubating pouch; the Chromis paterfamilias, of the lake of Tiberias, protects and nourishes in his mouth and bronchial cavity hundreds of small fishes.[33]
Other fishes also have more or less care for their young. Salmon and trout deposit their eggs in a depression which they have hollowed out in the sand for the purpose. Fishes, belonging to various families, construct nests and watch over the young when hatched (Cranilabrus massa, Cranilabrus melops). Often again it is the male who undertakes all the work. Thus the male of the Gasterosteus leiurus is incessantly occupied in fetching the young ones home, and driving away all enemies, including the mother.[34] The male stickleback, who is polygamous, builds a nest and watches with solicitude over the safety and rearing of the young.[35]
Many reptiles are unnatural parents; some, however, already possess some degree of familial instinct. Thus several males of the batrachians assist the female to eject her eggs. The male accoucheur toad rolls the eggs round his feet, and carefully carries them thus. The Surinam toad, the Pipa Americana, after having aided the female in the operation of laying the eggs, places them on the back of his companion, in little cutaneous cavities formed for their reception.[36]
The Cobra capella bravely defends its eggs. The saurians often live in couples, and the females of crocodiles escort their new-born little ones. Female tortoises go so far as to shelter their young in a sort of nest.[37]
But it is especially among birds and mammals that we find forms of union or association very similar to marriage and the family in the human species. Nothing is more natural; for anatomical and physiological analogy must of necessity lead in its train the analogy of sociology. There is no more uniformity either amongst mammals than amongst men; the needs, the habitat, and the necessities of existence dominate everything, and in order to secure adjustment to these, recourse is had to various processes.
Like men, birds live sometimes in promiscuity, and sometimes in monogamy or polygamy; the familial instinct is also very unequally developed among them. Sometimes even we find their conjugal customs modified by the kind of life they lead. Thus the wild duck, which is strictly monogamous in a wild state, becomes very polygamous when domesticated, and it is the same with the guinea fowl. Civilisation depraves these birds, as it does some men. As may be supposed, it is generally the animals living in troops who are degraded most easily by habitual promiscuity. But this is not always the case; the character of the animal, his mode of life, and the degree of morality previously acquired, determine his manner of acting. It is probable also that certain animals, living in troops during the breeding season, have formerly been less sociable than at present, for they leave the troop and retire apart in couples as soon as they have paired. Social life is burdensome to them.
It is especially interesting to study the various modes of conjugal and familial association amongst birds. This may easily be inferred from the ardour, the variety, and the delicacy they bring to their amours; the moral level among them, to borrow a human expression, is very diverse, according to the species. There are some birds absolutely fickle and even debauched—as, for example, the little American starling (Icterus pecoris), which changes its female from day to day; that is to say, it is in the lowest stage of sexual union, a debauched promiscuity, which we only exceptionally find in some hardly civilised human societies.[38] The starling, nevertheless, is not ferocious, like the asturides, to whom, according to Brehm, love seems unknown, and amongst whom the female devours her male, the father and the mother feast on their own young, and the latter, when full grown, willingly eat their parents. These ferocious habits denote a very feeble moral development. But if we may believe a French missionary, Mgr. Farand, bishop of the Mackenzie territory, similar customs still prevail among the Redskins of the extreme north.[39] We shall not, therefore, be too much scandalised at the birds. These cases of moral grossness are, besides, rare enough with them.
Other species, while they have renounced promiscuity, are still determined polygamists. The gallinaceæ are particularly addicted to this form of conjugal union, which is so common, in fact, with mankind, even when highly civilised and boasting of their practice of monogamy. Our barn-door cock, vain and sensual, courageous and jealous, is a perfect type of the polygamous bird. But the polygamous habits of the gallinaceæ do not prevent them from experiencing very strong sexual passion. When seized by this frenzy of desire, some of them appear to be senseless of all danger. The firing of a gun, for example, does not alarm a male grouse when swinging his head and whistling to charm his female;[40] but this ardour does not hinder him from being a fickle animal, always in search of new adventures, and always seeking fresh mates.[41]
These examples of wandering fancy are for the most part rare among birds, the majority of whom are monogamous, and even far superior to most men in the matter of conjugal fidelity.
Nearly all the rapacious animals, even the stupid vultures, are monogamous. The conjugal union of the bald-headed eagle appears even to last till the death of one of the partners. This is indeed monogamic and indissoluble marriage, though without legal constraint.[42] Golden eagles live in couples, and remain attached to each other for years without even changing their domicile.[43] But these instances, honourable as they are, have nothing exceptional in them; strong conjugal attachment is a sentiment common to many birds.
With the female Illinois parrot (Psittacus pertinax) widowhood and death are synonymous, a circumstance rare enough in the human species, yet of which birds give us more than one example. When, after some years of conjugal life, a wheatear happens to die, his companion hardly survives him a month. The male and female of the panurus are always perched side by side. When they fall asleep, one of them, generally the male, tenderly spreads its wing over the other. The death of one, says Brehm, is fatal to its companion. The couples of golden wood-peckers, of doves, etc., live in a perfect union, and in case of widowhood experience a violent and lasting grief. The male of a climbing wood-pecker, having seen his mate die, tapped day and night with his beak to recall the absent one; then at length, discouraged and hopeless, he became silent, but never recovered his gaiety (Brehm). These examples of a fidelity that stands every test, and of the religion of memory, although much more frequent in the unions of birds than in those of human beings, are not, however, the unfailing rule. With birds, as with men, there seems to be a good number of irregular cases—individuals of imperfect moral development and of fickle disposition. This may be inferred from the facility with which, among certain species of monogamous birds, the dead partner is replaced. Jenner, who introduced vaccination, relates that in Wiltshire he has seen one of a couple of magpies killed seven days in succession, and seven times over immediately replaced. Analogous facts have been observed of jays, falcons, and starlings. Now, when it concerns animals that are paired, each substitution must correspond to a desertion, the more so as the observations were made in the same locality and in the height of the breeding season.[44]
Very peculiar fancies sometimes arise in the brains of certain birds. Thus we see birds of distinct species pairing, and this even in a wild state. These illegitimate unions have been observed between geese and barnacle geese, and between black grouse and pheasants.
Darwin relates a case of this kind of passion suddenly appearing in a wild duck. The fact is related by Mr. Hewitt as follows:—“After breeding a couple of seasons with her own mallard, she at once shook him off on my placing a male pintail in the water. It was evidently a case of love at first sight, for she swam about the new-comer caressingly, though he appeared evidently alarmed and averse to her overtures of affection. From that hour she forgot her old partner. Winter passed by, and the next spring the pintail seemed to have become a convert to her blandishments, for they nested and produced seven or eight young ones.”[45] It is difficult not to attribute such deviations as these to motives similar to those by which we are ourselves actuated—to passion, caprice, or depravity. They certainly cannot be accounted for by the theory of mechanical and immutable instinct. Such facts clearly prove that animal psychology, although less complicated than our own, does not differ essentially from it, and consequently throws much light on our present investigation. The adventure of the wild duck, for example, may, without any alteration, be read as a human adventure, proving for the hundred-thousandth time that the heart, or what we call by that name, is versatile; that conjugal fidelity does not always resist a strong impression arising from a chance encounter; that novelty has a disturbing effect; and, finally, that indifference and coldness can rarely hold out against the persistent advances of one who loves ardently enough not to yield to discouragement. Dante has already made this last reflection in his celebrated line—
“Amor ch’a nullo amato amar perdona.”
To quote Dante à propos of the illicit amours of a pintail and a wild duck may shock the learned, but the aptness of the quotation proves once more the essential identity of the animal and human organisms.
III. The Family amongst Animals.
If the study of the modes of sexual union amongst animals is not useless to the sociologist, that of the animal family is at least quite as interesting. This latter confirms the inductions of theorists relative to the primitive form of the human family. The animal family is especially maternal. The female of birds, immediately she has laid her eggs, experiences a sort of intoxication; to sit becomes for her an imperious need, which completely transforms her moral nature. In January 1871, during the bombardment of Paris, a German shell, bursting in the loft of a house inhabited by one of my friends, was powerless to disturb a female pigeon absolutely enchained by the passion of incubation.
It is amongst birds that the animal family is best constituted; this, however, differs much according to the species, especially as regards the participation of the male in the rearing of the young.
Amongst ducks, the male has no care for his progeny. The male eider resembles the duck in this respect (Audubon). Male turkeys do much worse: they often devour the eggs of their females, and thus oblige the latter to hide them.[46] Female turkeys join each other with their young ones for greater security, and thus form troops of from sixty to eighty individuals, led by the mothers, and carefully avoiding the old males, who rush on the young ones and kill them by violent blows on the head with their beaks.[47]
Among certain species of gallinaceæ the male leaves to the female the care of incubation and of rearing the young. During this time he is running after adventures, but returns when the young are old enough to follow him and form a docile band under his government.[48] It is important to notice that, amongst birds, the fathers devoid of affection generally belong to the less intelligent species, and are most often polygamous. It seems, therefore, that polygamy is not very favourable to the development of paternal love.[49]
But bad fathers are rare amongst birds. Often, on the contrary, the male rivals the female in love for the young; he guards and feeds her during incubation, and sometimes even sits on the eggs with her. The carrier pigeon feeds his female while she is sitting;[50] the Canadian goose[51] and the crow do the same; more than that, the latter takes his companion’s place at times, to give her some relaxation. The blue marten behaves in the same manner.[52] Among many species, male and female combine their efforts without distinction of sex; they sit in turn, and the one who is free takes the duty of feeding the one who is occupied. This is the custom of the black-coated gull,[53] the booby of Bassan,[54] the great blue heron,[55] and of the black vulture.[56] According to Audubon, the blue bird of America works so ardently at the propagation of its species that a single brood does not satisfy him; each couple, therefore, exerts itself zealously, rearing two or three broods at the same time, the female sitting on one, while the male feeds the little ones of the preceding brood.[57]
But however violent the love of birds for their progeny may be, it lasts only a short time, and is suddenly extinguished when the young can manage for themselves. It is then quite surprising to see the parents drive away by strokes of the beak the little ones they had been nursing with such devoted tenderness a few days before. The birds of several species, however, teach their young to fly before separating from them. The white-headed sea-eagle carries them on its back to give them lessons in flying; grebes, swans, and eiders teach their young to swim, etc. But the family is only of short duration among birds and animals generally, unless, as is the case with some gallinaceæ, the male keeps a few of his daughters to enrich his harem. As a matter of fact, both with birds and other animals, the paternal or maternal sentiment hardly lasts longer than the rearing time. When once the young are full grown, the parents no longer distinguish them from strangers of their species, and it is thus even with monogamic species when the conjugal tie is lifelong; the marriage alone endures, but the family is intermittent and renewed with every brood. We may remark that it is almost the same with certain human races of low development. But, before speaking of man, it will be well to investigate conjugal union and the family amongst the animals nearest to man—the mammals.
From the point of view of duration and strength of the affections, or that which we as men should call their morality, the mammals are far from occupying the first rank in the animal hierarchy; many birds are very superior to them. We find, however, great differences in the morals, according to the species. Many mammals have stopped at the most brutal promiscuity; males and females unite and separate at chance meetings, without any care for the family arising in the mind of the male. The females of mammals being always weaker than the males, no sexual association comparable to polyandry is possible in this class, since, even if she wished it, the female could not succeed in collecting a seraglio of males. But as to polygamy, it is quite different, and this is very common with mammals, especially with the sociable kinds, living in flocks. It is even a necessity of the struggle for existence. Sociability generally proceeds from weakness. The species that are badly armed for fierce combats, and that have besides some difficulty in finding food, are glad to live in association. Union is strength. The ruminants, for example, do this. Certain carnivorous animals, ill-furnished with teeth and claws, dogs also, and jackals, live in troops for the same reason—that of opposing a respectable front to the enemy. This life in common is certainly favourable to the development of social virtues; it cannot but soften primitive cruelty, and develop altruistic qualities; but it is little conducive to sexual restraint and monogamy. Thus the greater number of sociable mammals are polygamous. The ruminants live in hordes composed of females and young, grouped around a male who protects them, but who expels his rivals and becomes a veritable chief of a band. Very various species compose familial societies in the same manner, and strongly resembling each other.
When the Indian adult elephant renounces the solitary life which strong animals generally adopt, it is in order to found a little polygamous society, from which he expels all the males weaker than himself.[58]
The moufflons of Europe and of the Atlas also form little societies of the same kind in the breeding season.[59]
Among the walrus, says Brehm, the male, who is of very jealous temperament, collects around him from thirty to forty females, without counting young, making altogether a polygamous family sometimes amounting to a hundred and twenty individuals.
The male of the Asiatic antilope saiga is inordinately polygamous; he expels all his rivals, and forms a harem numbering sometimes a hundred females.[60]
The polygamic régime of animals is far from extinguishing affectionate sentiments in the females towards their husband and master. The females of the guanaco lamas, for example, are very faithful to their male. If the latter happens to be wounded or killed, instead of running away, they hasten to his side, bleating and offering themselves to the shots of the hunter in order to shield him, while, on the contrary, if a female is killed, the male makes off with all his troop; he only thinks of himself.
In regard to mammals, there is no strict relation between the degree of intellectual development and the form of sexual union. The carnivorous animals often live in couples for the reason previously given; but this is not an absolute rule, for the South African lion is frequently accompanied by four or five females.[61] Bears, weasels, whales, etc., on the contrary, generally go in couples. Sometimes species that are very nearly allied have different conjugal customs; thus the white-cheeked peccary lives in troops, whilst the white-ringed peccary lives in couples.[62]
There is the same diversity in the habits of monkeys. Some are polygamous and others monogamous. The wanderoo (Macacus silenus) of India has only one female, and is faithful to her until death.[63] The Cebus capucinus, on the contrary, is polygamous.[64]
Those cousins-german of man, the anthropoid apes, have sometimes adopted polygamy and sometimes monogamy. Savage tells us that the Gorilla gina forms small hordes, consisting of a single adult male, who is the despotic chief of many females and a certain number of young.
Chimpanzees are sometimes polygamous and sometimes monogamous. The polygamous family of monkeys is always subject to the monarchic régime. The male, who is at the same time the chief, is despotic; he exacts a passive obedience from his subordinates, and he expels the young males as soon as they are old enough to give umbrage to him. To sum up, he is at once the father, the protector, and the tyrant of the band. Nevertheless, the females are affectionate to him, and the most zealous among them prove it by assiduously picking the lice from him, which, with monkeys, is a mark of great tenderness.[65] But the master who has been thus flattered and cringed to sometimes comes to a bad end. One fine day, when old age has rendered him less formidable, when he is no longer capable of proving at every instant that right must yield to might, the young ones, so long oppressed, rebel, and assassinate this tyrannous father. We must here remark, that whatever the form of sexual association among mammals, the male has always much less affection for the young than the female. Even in monogamous species, when the male keeps with the female, he does so more as chief than as father. At times he is much inclined to commit infanticides and to destroy the offspring, which, by absorbing all the attention of his female, thwart his amours. Thus, among the large felines, the mother is obliged to hide her young ones from the male during the first few days after birth, to prevent his devouring them.
I shall here conclude this very condensed study of sexual association and the family in the animal kingdom. My object is not so much to exhaust the subject, as to bring into relief the analogies existing between man and the other species. The facts which have been cited are amply sufficient for this purpose, and we may draw the following general conclusions from them:—
In the first place there is no premeditated design in nature; any mode of reproduction, of sexual association and of rearing of young that is compatible with the duration of the species may be adopted. But in a general manner it may be said that a sort of antagonism exists between the multiplicity of births and the degree of protection bestowed on the young by the parents.
A rough outline of the family is already found in the animal kingdom; it is sometimes patriarchal, as with sticklebacks, etc., but most often it is matriarchal. In the latter case the female is the centre of it, and her love for the young is infinitely stronger and more devoted than that of the male. This is especially true of mammals, with whom the male is generally an egoist, merely protecting the family in his own personal interest.
The familial instinct, more or less developed, exists in the greater number of vertebrates, and in many invertebrates. From an early period it must have been an object of selection, since it adds considerably to the chances of the duration of the species. With some species (ants, bees, termites) this instinct has expanded into a wide social love, resulting in the production of large societies of complex structure, in which the family, as we understand it, is unknown. I lay stress on this fact, for it is of great importance in theoretical sociology; it proves, in fact, that large and complicated societies, with division of social labour, can be maintained without the institution of the family. We are not, therefore, warranted in pretending, as is usually done, that the family is absolutely indispensable, and that it is the “cellule” of the social organism. Let us observe, by the way, that the expression “social organism” is simply metaphorical, and we must beware of taking it literally, as Herbert Spencer, with a strange naïveté, seems to have done. Societies are agglomerations of individuals in which a certain order is necessarily established; but it is almost puerile to seek for, and to pretend to find in them, an actual organisation, comparable, for example, to the anatomic and physiologic plan of a mammal.
Terminating this short digression, I revert to my subject by summing up the results of our examination of sexual associations among the animals.
In regard to marriage, as well as to the family, nature has no preference; all means are welcome to her, provided the species profits by them, or, at least, does not suffer too much from them.
We find amongst animals temporary unions, at the close of which the male ceases absolutely to care for the female; but we also find, especially among birds, numbers of lasting unions, for which the word marriage is not too exalted. It does not appear that polyandry—that is, a durable society between one female and many males—has been practised by animals. The female, nearly always weaker than the male, could not reduce a number of them to sexual servitude, and the latter have never been tempted to share one female systematically. On the contrary, they are often polygamous. But it is especially amongst mammals that polygamy is common, and it must often have had its raison d’être either in the sexual proportion of births, or in a greater mortality of males. These are reasons I shall have to refer to later, in speaking of human polygamy.
But if polygamy is frequent with mammals, it is far from being the conjugal régime universally adopted; monogamy is common, and is sometimes accompanied by so much devotion, that it would serve as an example to human monogamists.
It is important also to notice that, in regard to animals, the mode of sexual association may vary without much difficulty. No species is of necessity and always restricted to such or such a form of sexual union. An animal belonging to a species habitually monogamous may very easily become polygamous. In short, there does not seem to be any relation between the degree of intelligence in a species and its conjugal customs.
In the following chapters it will be seen that, in great measure, these observations do not apply exclusively to animals.