We have observed that, according to naturalists, the earliest forms of life which appeared on the earth were androgynous or hermaphrodite, that the two elements necessary for reproduction were originally confined within one and the same individual within which were carried on all the functions of reproduction. Later, however, a division of labour arose, and these two original functions became detached, after which time the reproductive processes were carried on only through the commingling of elements prepared by, or developed within, two separate and distinct individuals.
As the belief is entertained by our guides in this matter that greater differentiation, or specialization of parts, denotes higher organization, it is believed that the division of labour by which the germ is prepared by one individual and the sperm by another individual, as is the case at the present time with all the higher orders of life, constitutes an important step in the line of progress. Here this line of argument ceases, and, until very recent15 times, concerning the course of development followed by each sex little has been heard. This silence on a subject of such vital importance to the student of biology is not perhaps difficult to understand; the conclusion, however, is unavoidable that the individual which must nourish and protect the germ, and by processes carried on within her own body provide nourishment for the young during its prenatal existence, and sometimes for years after birth, must have the more highly specialized organism, and must, therefore, represent the higher stage of development. Indeed, it is admitted by scientists that the advance from the egg-layers to the milk-givers indicates one of the most important steps in the entire line of development; and yet the peculiar specialization of structure necessary for its accomplishment was for the most part carried on within the female organism.
Concerning the origin of sex in the individual organism little seems to be known; as a result, however, of observations on the development of the reproductive organs in the higher vertebrates, and especially in birds, it is believed that there exists a “strict parallelism between the individual and the racial history,”—that the three main stages in the development of the chick, viz.: (1) germi-parity, (2) hermaphroditism, and (3) differentiated unisexuality, correspond to the three great steps of historic evolution.
By a careful investigation of the facts connected16 with the development of unisexual forms, we are enabled to discover the early beginnings of the characteristics which distinguish the two sexes throughout their entire course. We are told that with animals which have their sexes separate, in addition to strictly sexual difference
the male possesses certain organs of sense or locomotion, of which the female is quite destitute, or has them more highly developed, in order that he may readily find or reach her; or again the male has special organs of prehension for holding her securely. These latter organs, of infinitely diversified kinds, graduate into those which are commonly ranked as primary.4
The female, on the other hand, in addition to those sexual characters which are strictly primary, has “organs for the nourishment or protection of her young, such as the mammary glands of mammals, and the abdominal sacks of the marsupials.” In addition to these she is frequently provided with organs for the defence of the community; for instance, “the females of most bees are provided with a special apparatus for collecting and carrying pollen, and their ovipositor is modified into a sting for the defence of the larv? and the community.” We are assured by Mr. Darwin that many similar cases could be given.5
Here, then, with almost the first or primary step toward sexual differentiation, may be observed17 the establishment of that peculiar bias which upon investigation will be seen to extend all along the two lines of sexual demarcation, and which (to anticipate the conclusions of our argument), as soon as mankind is reached, appears in the male as extreme egoism or selfishness, and in the female as altruism or care for other individuals outside of self.
We are assured, however, that it is not alone to the reproductive organs and their functions that we are to look for the chief differences in the constitution and character of the sexes. Neither is it entirely to Natural Selection that we are to seek for the causes which underlie the specialization peculiar to the two diverging lines of sexual demarcation; in addition to primary sexual divergences, there are also “secondary sexual characters” which are of great importance to their possessor. Indeed, from the prominence given to Sexual Selection by Mr. Darwin, it would seem that it played a part in the development of males quite equal to that of Natural Selection itself.
Now the difference between Natural Selection and Sexual Selection is that, whereas, in the former, characters are developed and preserved which are of use to the individual in overcoming the unfavourable conditions of environment, by the latter, only those characters are acquired and preserved which assist the individual in overcoming the obstacles to reproduction; or, to use Mr. Darwin’s own language:
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[Sexual Selection] depends on the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction.... [Where] the males have acquired their present structure, not from being better fitted to survive in the struggle of existence, but from having gained an advantage over other males, and from having transmitted this advantage to their male offspring alone, sexual selection must here have come into action.... A slight degree of variability leading to some advantage, however slight, in reiterated deadly contests would suffice for the work of sexual selection; and it is certain that secondary sexual characters are eminently variable. Just as man can give beauty, according to his standard of taste, to his male poultry, or more strictly can modify the beauty originally acquired by the parent species, can give to the Sebright bantam a new and elegant plumage, an erect and peculiar carriage—so it appears the female birds in a state of nature, have by a long selection of the more attractive males, added to their beauty or other attractive qualities.6
Thus, according to Mr. Darwin, it is through a long selection by females of the more attractive males that the present structure of the latter has been acquired. If, in a short time, a man can give elegant carriage and beauty to his bantams, according to his standard of beauty, he can see no reason to doubt that female birds, by selecting during thousands of generations the most melodious or beautiful males, according to their19 standard of beauty, might produce a marked effect. He says:
To sum up on the means through which, as far as we can judge, sexual selection has led to the development of secondary sexual characters. It has been shown that the largest number of vigorous offspring will be reared from the pairing of the strongest and best armed males, victorious in contests over other males, with the most vigorous and best-nourished females, which are the first to breed in the spring. If such females select the more attractive, and at the same time vigorous males, they will rear a larger number of offspring than the retarded females, which must pair with the less vigorous and less attractive males.... The advantage thus gained by the more vigorous pairs in rearing a larger number of offspring has apparently sufficed to render sexual selection efficient.7
Although the belief is common among naturalists that the appearance of secondary sexual characters belonging to males is greatly influenced by female choice, a majority of writers upon this subject are not in sympathy with Mr. Darwin’s theory concerning the origin of these variations. It is believed by them that Sexual Selection “may account for the perfecting, but not for the origin, of these characters.”
It is useless, however, to rehearse the opinions of the various writers who have dealt with this subject. It is perhaps sufficient to state that20 the great beauty of males has usually been accepted as evidence of their superiority over the females.
In his chapter, “The Male generally more Modified than the Female,” Mr. Darwin remarks: “Appearances would indicate that not the male which is most attractive to the female is chosen, but the one which is least distasteful.” He says that the aversion of female birds for certain males renders the season of courtship one of great anxiety and discomfiture, not only to many of the more poorly endowed aspirants, but to those also which are more magnificently attired—that the pairing ground becomes a field of battle, upon which, while parading their charms to the best advantage, is sacrificed much of the gorgeous plumage of the contestants. On the wooing ground are displayed for the admiration and approval of the females, all the physical attractions of the males, as well as the mental characters correlated with them, namely, courage, and pugnacity or perseverance. According to Mr. Darwin, with the exception of vanity, no other quality is in any considerable degree manifested by male birds, but to such an extent has love of display been developed in many of them, notably the pea-fowl, that, “in the absence of females of his own species, he will show off his finery before poultry and even pigs.” We are assured that the higher we ascend in the animal kingdom the more frequent and more violent become two desires in the male:21 “the desire of appearing beautiful, and that of driving away rivals.” According to Mr. Darwin’s theory of development, because of the indifference of the female among the lower orders of life to the processes of courtship, it has been necessary for the male to expend much energy or vital force in searching for her—in contending with his rivals for possession of her person, and in performing various acts to please her and secure her favours. While excessive eagerness in courtship is the one all-absorbing character of male fishes, birds, and mammals, we are assured that with the females, pairing is not only a matter of indifference, but that courtship is actually distasteful to them, and, therefore, that the former must resort to the various means referred to in order to induce the latter to submit to their advances.
We are informed that the female is sometimes charmed through the power of song; that at other times she is captivated by the diversified means which have been acquired by male insects and birds for producing various sounds resembling those proceeding from certain kinds of musical instruments; and not unfrequently she is won by means of antics or love dances performed on the ground or in the air. On the pairing-ground, combs, wattles, elongated plumes, top-knots, and fancy-coloured feathers are paraded for the admiration and approval of the females. Led by the all-absorbing instinct of desire,
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the males display their charms with elaborate care and to the best effect; and this is done in the presence of the females.... To suppose that the females do not appreciate the beauty of the males, is to admit that their splendid decorations, and all their pomp and display, are useless; and this is incredible.8
Topknots, gaudy feathers, elongated plumes among birds, huge tusks, horns, etc., among mammals, the mane of the lion, and the beard of man, may be noticed among the many characters which have been acquired through Sexual Selection.
Although the immense teeth, tusks, horns, and various other weapons or appendages which ornament the males of many species of mammals, have all been developed through Sexual Selection for contending with their rivals for the favours of the females, it is observed that the “most pugnacious and best armed males seldom depend for success on their ability to drive away or kill their rivals,” but that their special aim is to “charm the female.” Mr. Darwin quotes from a “good observer,” who believes that the battles of male birds “are all a sham, performed to show themselves to the greatest advantage before the admiring females who assemble around.”9
In The Descent of Man is quoted the following from Mr. Belt, who, after describing the beauty of the Florisuga mellivora, says:
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I have seen the female sitting on a branch, and two males displaying their charms in front of her. One would shoot up like a rocket, then suddenly expanding the snow-white tail, like an inverted parachute, slowly descend in front of her, turning round gradually to show off back and front.... The expanded white tail covered more space than all the rest of the bird, and was evidently the grand feature in the performance. Whilst one male was descending, the other would shoot up and come slowly down expanded. The entertainment would end in a fight between the two performers; but whether the most beautiful or the most pugnacious was the accepted suitor, I know not.10
Audubon, who spent a long life in observing birds, has no doubt that the female deliberately chooses her mate. Of the woodpecker he says the hen is followed by half a dozen suitors, who continue performing strange antics “until a marked preference is shown for one.” Of the red-winged starling it is said that she is pursued by several males “until, becoming fatigued, she alights, receives their addresses, and soon makes a choice.”11 Mr. Darwin quotes further from Audubon, who says that among the Virginia goat-suckers, no sooner has the female “made her choice than her approved gives chase to all intruders, and drives them beyond his dominions.”
It is said that among mammals the male depends almost entirely upon his strength and courage to24 “charm the female.” With reference to the struggles between animals for the possession of the females, Mr. Darwin says:
This fact is so notorious that it would be superfluous to give instances. Hence the females have the opportunity of selecting one out of several males, on the supposition that their mental capacity suffices for the exertion of a choice.12
We are assured that among nearly all the lower orders of life the female exhibits a marked preference for certain individuals, and that an equal degree of repugnance is manifested towards others, but that the male, whose predominant character is desire, “is ready to pair with any female.” On this subject Mr. Darwin remarks: “The general impression seems to be that the male accepts any female.” He says it frequently occurs that while two males are fighting together to win the favours of a female, she goes away with a third for whom she has a preference. Mr. Darwin quotes from Captain Bryant, who says of a certain species of seals:
Many of the females on their arrival at the island where they breed, appear desirous of returning to some particular male, and frequently climb the outlying rock to overlook the rookeries, calling out and listening as if for a familiar voice. Then changing to another place they do the same again.13
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Little seems to be known of the courtship of animals in a state of nature. Among domesticated species, however, many observations have been made by breeders going to prove that the female exerts a choice in pairing. Concerning dogs, Mr. Darwin quotes from Mr. Mayhew, who says: “The females are able to bestow their affections; and tender recollections are as potent over them as they are known to be in other cases where higher animals are concerned.” Of the affection of female dogs for certain males the same writer says it “becomes of more than romantic endurance,” that they manifest a “devotion which no time can afterwards subdue.”
On concluding his chapter on choice in pairing among quadrupeds, Mr. Darwin remarks:
It is improbable that the unions of quadrupeds in a state of nature should be left to mere chance. It is much more probable that the females are allured or excited by particular males, who possess certain characters in a higher degree than other males.14
As the female among birds selects her partner, he thinks it would be a strange anomaly if among quadrupeds, which stand higher in the scale and have higher mental powers, she did not also exert a choice.15
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Because of the indifference of the female to the attentions of the male, in order to carry on the processes of reproduction, it was necessary among the lower orders that the male become eager in his pursuit of her, and as a result of this eagerness excessive passion was developed in him. As the most eager would be the most successful in propagating, they would leave the greatest number of offspring to inherit their characters—namely, in males, passion and pugnacity correlated with the physical qualities acquired through Sexual Selection.
On the subject of the acquirement of secondary sexual characters, Mr. Darwin says: “The great eagerness of the males has thus indirectly led to their much more frequently developing secondary sexual characters.” Indeed, by all naturalists, the fact is recognized that the appearance of these characters is closely connected with the reproductive function.
Later experiments have confirmed the observations of Mr. Darwin concerning the intelligence of27 the female among the lower orders of life. Among these experiments are those recently made by Professor Harper, of the Department of Biology, in the Northwestern University. Professor Harper announces that in all the experiments conducted by him, the female animal showed a greater degree of perception, or intelligence, than the male. He says: “In all my experiments, I found that the female displayed a remarkable quickness in grasping ideas which the male after numerous sluggish efforts finally accomplished.” Professor Harper declared that these facts regarding animals apply with equal force to human beings.
Regarding the power of the female to appreciate the beauty of the males, Mr. Darwin says:
No doubt this implies powers of discrimination and taste on the part of the female which will at first appear extremely improbable; but by the facts to be adduced hereafter, I hope to be able to show that the females actually have these powers.16
In commenting on the fact that the female Argus pheasant appreciates the exquisite shading of the ball-and-socket ornaments, and the elegant patterns on the wing-feathers of the male, Mr. Darwin writes:
He who thinks that the male was created as he now exists, must admit that the great plumes which prevent the wings from being used for flight, and which are28 displayed at courtship and at no other time, in a manner quite peculiar to this species, were given to him as ornaments. If so he must likewise admit that the female was created and endowed with the capacity for appreciating such ornaments. Every one who admits the principle of evolution, and yet feels great difficulty in believing the high taste implied by the beauty of the males, and which generally coincides with our own standard, should reflect that the nerve cells of the brain in the highest as in the lowest members of the vertebrate series are derived from those of the common progenitor of this great kingdom.
In referring to the remarkable patterns displayed on the male Argus pheasant, designs which have been developed through Sexual Selection, Mr. Darwin says:
Many will declare that it is utterly incredible that a female bird should be able to appreciate fine shading and exquisite patterns. It is undoubtedly a marvellous fact that she should possess this almost human degree of taste. He who thinks that he can safely gauge the discrimination and taste of the lower animals may deny that the female Argus pheasant can appreciate such refined beauty; but he will then be compelled to admit that the extraordinary attitudes assumed by the male during the act of courtship, by which the wonderful beauty of his plumage is fully displayed, are purposeless; and this is a conclusion which I, for one, will never admit.17
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Here, then, in the female bird we see developed in a remarkable degree the power of discrimination, the exercise of taste, a sense of beauty, and the ability to choose—qualities which the facts brought forward by scientists show conclusively to have been acquired by the female and by her transmitted to her offspring. Regarding males, outside the instinct for self-preservation, which, by the way, is often overshadowed by their great sexual eagerness, no distinguishing characters have been acquired and transmitted, other than those which have been the result of passion, namely, pugnacity and perseverance. This excessive eagerness which prompts them to parade their charms whenever such display is likely to aid them in the gratification of their desires is developed only in the male line.
According to the law of heredity, those modifications of the male which have been the result of Sexual Selection appear only in the sex in which they originated. It will be well for us to remember that according to Mr. Darwin’s theory of pangenesis, sexes do not differ much in constitution before the power of reproduction is reached, but that after this time the undeveloped atoms or
gemmules which are cast off from each varying part in the one sex would be much more likely to possess the proper affinities for uniting with the tissues of the same sex, and thus becoming developed, than with those of the opposite sex.18
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We are given to understand that secondary sexual characters are extremely variable, also that variability denotes low organization; secondary sexual characters indicate that the various organs of the structure have not become specialized for the performance of their legitimate functions. Highly specialized forms are not variable.
To sum up the argument thus far: It has been observed that through the separation of the sexes, and the consequent division of labour, there have been established two diverging lines of development. While the male pheasant has been inheriting from his male progenitors fantastic ball-and-socket ornaments, and huge wings which are utterly useless for their legitimate purpose, the female, in the meantime, has been receiving as her inheritance only those peculiarities of structure which tend toward uninterrupted development. Within her have been stored or conserved all the gain which has been effected through Natural Selection, and as a result of greater specialization of parts, there have been developed certain peculiarities in her brain nerve-cells, by which she is enabled to exercise functions requiring a considerable degree of intelligence.
Although this power of choice, which we are given to understand is exercised by the female throughout the various departments of the vertebrate kingdom (evidences of it having been observed among creatures even as low in the organic scale as fishes), implies a degree of intelligence31 far in advance of that manifested by males, it is admitted that the qualities which bespeak this superiority, namely, the power to exercise taste and discrimination, constitute a “law almost as general as the eagerness of the male.”19
We are assured by Mr. Darwin that in the economy of nature those ornaments of the male Argus pheasant which serve no other purpose than to please the female and secure her favours, and which have been acquired at great expense of vital force, are of the “highest importance to him,” and that his success in captivating the female “has more than compensated him for his greatly impeded power of flight and his lessened capacity for running.” Yet it is plain that his compensation for this immense expenditure of vital force has not lain in the direction of higher specialization, but that while by the acquirement of these characters the processes of reproduction have doubtless been aided, the injury to the male constitution has been deep and lasting.
Upon this subject Mr. Darwin himself says:
The development, however, of certain structures—of the horns, for instance, in certain stags—has been carried to a wonderful extreme; and in some cases to an extreme which, as far as the general conditions of life are concerned, must be slightly injurious to the male.20
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He thinks, however, that
Natural Selection will determine that such characters shall not be acquired by the victorious males if they would be highly injurious, either by expending too much of their vital powers or by exposing them to any great danger.
According to Mr. Darwin, as these characters enable them to leave a more numerous progeny, their advantages are in the long run greater than those derived from more perfect adaptation to their conditions of life. It is plain, however, that this advantage, although it enables them to gratify their desires, and at the same time to perpetuate their species, does not imply higher development for the male organism.
We have been assured by our guides in these matters that in the processes of evolution there is no continuous or unbroken chain of progress, that growth or change does not necessarily imply development, but, on the contrary, only as a structure becomes better fitted for its conditions, and only as its organs become more highly specialized for the performance of all the duties involved in its environment, may it be said to be in the line of progress. If this be true, particular attention should be directed to the fact that as secondary sexual characters do not assist their possessor in overcoming the unfavourable conditions of his environment, they are not within the line of true development, but, on the contrary, as their growth33 requires a great expenditure of vital force, and, as is the case among birds, they often hinder the free use of the legs in running and walking, and entirely destroy the use of the wings for flight, they must be detrimental to the entire structure. For the reason that females have managed to do without them, the plea that the great tusks, horns, teeth, etc., of mammals have been acquired for self-defence, is scarcely tenable.
On the subject of the relative expenditure of vital force in the two lines of sexual demarcation, Mr. Darwin remarks:
The female has to expend much organic matter in the formation of her ova, whereas the male expends much force in fierce contests with his rivals, in wandering about in search of the female, in exerting his voice, pouring out odoriferous secretions, etc.... In mankind, and even as low down in the organic scale as in the Lepidoptera, the temperature of the body is higher in the male than in the female, accompanied in the case of man by a slower pulse.[21]
Yet he concludes: “On the whole the expenditure of matter and force by the two sexes is probably nearly equal, though effected in very different ways and at different rates.”21
However, as has been observed, the force expended by the male in fierce contests with his rivals, in wandering about in search of the female, and in his exertions to please her when found, does34 not constitute the only outlay of vitality to which he is subjected; but in addition to all this, there still remains to be considered that force which has been expended in the acquirement of characters which, so far as his own development is concerned, are useless and worse than useless; namely, in birds, combs, wattles, elongated plumes, great wings, etc., and in mammals great horns, tusks, and teeth—appendages which lie outside the line of true development, and, as we have seen, are of no avail except to aid in the processes of reproduction and to assist him in the gratification of his desires; in fact, as these excrescences hinder him in the performance of the ordinary functions of life, they may be regarded in the light of actual hindrances to higher development.