Part 9

The commonest form of play in birds is flying play. Any one who has kept his eyes open at the seaside will have seen the Herring Gulls congregate in soaring intersecting spirals where the cliff sends the wind upwards. But such flights are nothing compared with those of other birds. Even the staid black-coated Raven may sometimes be seen to go through a curious performance. One I remember, all alone, flying along the side of a mountain near Oban; but instead of progressing in the conventional way, he flew diagonally upwards for a short distance, then giving a special croak with something of gusto in it, turned almost completely over on to his back, and descended a corresponding diagonal in this position. Then with a strong flap of the wings he righted himself, and so continued until he disappeared round the shoulder of the hill half a mile on. It reminded me of a child who has learnt some new little trick of step or dance-rhythm, and tries it out happily all the way home along the road. Mr. Harold Massingham has seen the Ravens’ games too, and set them down more vividly than I can.[26] He also is clear that they play for the love of playing, and even believes that their love of sport has helped their downfall to rarity by rendering them too easy targets for the gunner.

Or again, at the Egret rookery in Louisiana, at evening when the birds returned in great numbers, they came back with steady wing-beats along an aerial stratum about two hundred feet up. Arrived over their nesting pond, they simply let themselves drop. Their plumes flew up behind like a comet’s tail; they screamed aloud with excitement; and, not far above the level of the trees, spread the wings so that they caught the air again, and as result skidded and side-slipped in the wildest and most exciting-looking curves before recovering themselves with a brief upward glide and settling carefully on the branches. This certainly had no significance for courtship; and I never saw it done save over the pond at the birds’ return. It seemed to be simply an entertaining bit of sport grafted on to the dull necessity of descending a couple of hundred feet.

Examples could be multiplied: Rooks and Crows, our solemn English Heron, Curlew, Swifts, Snipe--these and many others have their own peculiar flying sports. What is clear to the watcher is the emotional basis of these sports--a joy in controlled performance, and excitement in rapidity of motion, in all essentials like the pleasure to us of a well-hit ball at golf, or the thrill of a rapid descent on sledge skis.

For any one to whom the evolution theory is one of the master-keys to animate nature, there must be an unusual interest in tracing out the development of lines of life that, like the birds’, have diverged comparatively early from the line which eventually and through many vicissitudes led to Man.

In the birds as in the mammals, and quite separately in the two groups, we see the evolution not only of certain structural characters such as division of heart, compactness of skeleton, increase of brain-size, not only of physiological characters like warm-bloodedness or efficiency of circulation, but also of various psychical characters. The power of profiting by experience becomes greater, as does that of distinguishing between objects; and there is most markedly an increase in the intensity of emotion. It has somehow been of advantage, direct or indirect, to birds to acquire a greater capacity for affection, for jealousy, for joy, for fear, for curiosity. In birds the advance on the intellectual side has been less, on the emotional side greater: so that we can study in them a part of the single stream of life where emotion, untrammelled by much reason, has the upper hand.

BIBLIOGRAPHY

Chance, E., ’22. “The Cuckoo’s Secret.” London, 1922.

Darwin, C., ’71. “The Descent of Man, and Selection in Relation to Sex.” London, 1871.

Groos, K., ’98. “The Play of Animals.” New York, 1898.

Howard, E., ’20. “Territory in Bird Life.” London, 1920.

Hudson, W. H., ’12. “The Naturalist in La Plata” (5th Ed.). London, 1912.

Huxley, J. S., ’14 and ’23. (Courtship in Birds) Proc. Zool. Soc., 1914, and Proc. Linn. Soc., 1923.

Kirkman, F. B. (ed.), ’10. “British Bird Book.” London, 1910.

Levick, G. M., ’14. “Antarctic Penguins.” London, 1914.

Massingham, H. J., ’23. “The Ravens.” _Nation and Athenæum._ London, 21st April, 1923.

Selous, E., ’01. “Bird Watching.” London, 1901.

Selous, E., ’05. “Bird Life Glimpses.” London, 1905.

FOOTNOTE:

[26] Massingham, ’23.

IV

SEX BIOLOGY AND SEX PSYCHOLOGY

SEX: THREE WAYS

That body has for soul an air-balloon Which drifts with every spiritual blast, Doomed, swollen thing! to leak or burst at last Though overmuch aspiring toward the moon.

This other soul, below the animal, Bloating and coating body’s baser parts With the manure of its desires and arts, Helps flesh to grow still more corporeal.

I pray that I may still inhabit earth, Where grass invites the foot, and roses smell; Yet shall I lead my body on to dwell In the eternal land of second birth, If, nought contemned, each part of being’s whole Is taken up in my transmuting soul.

SEX BIOLOGY AND SEX PSYCHOLOGY[27]

“And now I see with eye serene The very pulse of the machine.” --W. WORDSWORTH.

“There is reason to believe that the processes which underlie all great work in art, literature, or science take place unconsciously, or at least unwittingly. It is an interesting question to ask whence comes the energy of which this work is the expression. There are two chief possibilities: one, that it is derived from the instinctive tendencies which, through the action of controlling forces, fail to find their natural outlet; the other, that the energy so arising is increased in amount through the conflict between controlled and controlling forces.”--W. H. RIVERS.

The biology of sex is a vast subject. Not only are there questions of sex-determination, but the whole sexual selection problem has to be considered, together with the evolutionary function of sex, and its first origin. I can only attempt, in the short space at my disposal, to deal with one or two of the chief points, and only in so far as they bear on questions of human sex psychology.

In the first place, then, we have to consider the evolutionary history of sex. Of its origin we can say only that it is veiled in complete obscurity. Once present, however, it appears to have a definite function by making possible, through sexual reproduction, all the various combinations of any heritable variations that may arise in different individuals of a species, and so conferring greater evolutionary plasticity on the species as a whole.[28]

Primarily, sex implies only the fusion of nuclei from two separate individuals; there is no need for sex differences to exist at all. Sex differences, however, are almost universal in sexually-reproducing organisms, and represent a division of labour between the active male cell and the passive female cell, the former taking over the task of uniting the two, the latter storing up nutriment for the new individual that will result from that union.

The subsequent history of sex is, roughly speaking, the history of its invasion of more and more of the organization of its possessors. First the male as a whole, and not merely its reproductive cells, tends to become organized for finding the female. The female’s whole type of metabolism is altered to produce the most efficient storage of reserve material in her ova, and later she almost invariably protects and nourishes the young during the first part of their development, either within or without her own body. Appropriate instincts are of course developed in both male and female.

At the outset there is enormous waste incurred in the liberation of sperms and ova into the water, there to unite as best they may. Congress of the sexes eliminates the major part of this waste, and is universal above a certain level. This is in itself the basis for other changes. As the mind, or shall we say the psycho-neural organization, becomes more complex, the sexual instinct becomes more interwoven with the general emotional state; and a large number of animals appear not to mate unless their emotional state has been raised to a certain level. The result of this is that special actions, associated generally with bright colours or striking structures, with song or with scent, come into being.

The exact mechanism of the appearance of these courtship-displays is a much-vexed point; but it is undoubted that they only occur in animals with congress of the sexes and with minds above a certain level of complexity, and that they are employed in ceremonies between the two sexes at mating-time. There can subsist no reasonable doubt that there exists some causal connection between the associated facts.

An important point, which has been commonly overlooked, is that such characters and actions may be either developed in one sex only, or in both. In a large number of birds, such as egrets, grebes, cranes, and many others, the courtship-displays are mutual, and the characters used in them developed to a similar extent in both sexes. Such characters are therefore often not secondary sexual differences, and we had best use Poulton’s term _epigamic_ for them, whether they are developed in one or in both sexes.[29]

The human species, in accordance with its complexity and flexibility of brain, has epigamic characters of both kinds. Some, like voice and moustache, are different in the two sexes, others, such as colour of eyes and lips, the hairlessness of the body and grace of limbs and carriage, are common to both.

In the vertebrate stock, two main lines of evolution as regards sexual relationships may be traced. The first is predominant in mammals: here, in most species, the female will not receive the male except at fixed times, which are determined by a purely physiological mechanism, the internal secretion of the gonad (reproductive organ). Here we consequently find that the rule is for the males to fight for the possession of the females, not to display before them. In the monkeys, presumably as a result of a lessened dependence of mental upon physiological processes, bright colours and special adornments of various parts of the body are frequently developed.[30]

In the birds, on the other hand, although here too the internal secretion of the gonad delimits a period in which alone congress of the sexes can occur, it does not act for such a sharply-limited time as in the mammal, nor is it so intense as completely to override other components of the mind. As a result, general emotional stimulus may play an important part in inducing readiness to pair, and we accordingly find display of some sort, either by the male alone or by both sexes, present in the great majority of species. It is at least partly in correlation with this that beauty of voice and brilliant appearance is far commoner in birds than in mammals.

The monkeys represent in some way a transitional stage towards that seen in man, in whom the conditions have come to resemble those found in birds, with consequent great development of epigamic characters and actions of one sort and another, both physical and mental. Thus we see that sex, after invading and altering the conformation of the body, finally invades and alters the conformation of the mind.

As regards the other great biological question, of the determination of sex, a very few words will suffice. In the first place I have no time to consider plants or lower animals. In almost all higher animals that have been investigated, however, there has been found some hereditary mechanism for ensuring a rough constancy of sex-ratio. This mechanism resides in the so-called _chromosomes_ of the nucleus. These exist for the most part in similar pairs in both sexes: but one pair is dissimilar in one sex. In mammals and man this sex is the male. Man possesses one chromosome less than woman. He possesses only one member of this pair of special sex-chromosomes, whereas she possesses two. All her ova are alike in possessing one, whereas half his sperms possess one, half possess none. Therefore, when the former kind of sperms fertilize an ovum, two sex-chromosomes are present in the fertilized egg and a female results; when the latter, only one, and the offspring is male.[31]

Putting the matter in the broadest terms, we can say that there is a different balance of hereditary factors in male and female, and that this difference of balance dates from the moment of fertilization, and normally determines sex.

Various agencies may alter the balance. The chromosomes themselves may vary in what we must vaguely call their potency; or external agencies may affect it. As a result, we sometimes obtain strange abnormal individuals, in which the balance has been upset; in them development results sometimes in organisms permanently intermediate between male and female, sometimes in a change of sex at some period of development.

In insects the chromosomes appear to be predominant throughout life. In vertebrates, however, they seem to play their chief rôle in early development, ending by building up either a male or a female gonad in the early embryo. This, once produced, takes over what remains of the task of sex-determination. It secretes a specific internal secretion which in a male acts so as to encourage the growth of male organs and instincts, to suppress those of females; and vice versa in a female.

As a result of this difference we find that castration in insects, even followed by engrafting of a gonad of opposite sex, produces no effect upon other sexual characters; whereas it exerts a profound effect upon mammals or birds.

As a second result, we find that in vertebrates the gonads form part of what has been called the chemical directorate of the body--the interlocking system of endocrine glands, each of which is exerting an effect upon the rest. The importance of this is seen in the experiments of Steinach, Sand, Voronoff, and others, who have been able to obtain a rejuvenating effect in senile mammals by increasing, by various methods, the amount of secreting reproductive organ in the body.[32]

To what then has our rapid survey led us? The actual origin of sex is lost to us in the mists of a time inconceivably remote. Its preservation once in existence, and its present all-but-universal distribution seem to be definitely associated with the biological advantage of the plasticity which it confers. Later, the primary difference between male and female--their power of producing different sorts of reproductive cells--leads on to secondary differences. These differences may be biologically speaking non-significant, mere accidents of the primary difference. Or they may be in the nature of a division of labour between the sexes, this division of labour usually concerning the protection of the embryo or the care of the young, or more rarely the preservation of the individual itself. Or, finally, they may concern the more efficient union of the gametes; such differences may merely affect the ducts and apertures of the reproductive system, and be more or less mechanical; or they may concern the use of these systems, in the form of still mechanical instincts, or they may be concerned in some way or other with the emotional side of the animals, and consist in characters and actions which stimulate the emotions of the other sex, characters which we have termed epigamic.

It is only in higher groups that these emotion-stimulating sexual characters arise, for only in them has mind reached a sufficient degree of perfection. But even though detailed study reveals in a bird or a mammal a mental life of a complexity far more considerable than the average man would imagine, yet on the whole it is straightforward and its currents run fairly direct from stimulus to fulfilment.

When we reach man, however, the whole aspect of the matter changes. The change is most marked, naturally, in his mental organization. Through his powers of rapid and unlimited association, any one part of his experience can be combined with any other; through his powers of generalizing and of giving names to things, his experience is far more highly organized than that of any animal; through speech and writing he is inheritor of a continuous tradition which enormously enlarges his range of experience. Again, he can frame a purpose and thus put the objective of his actions far further into the future than can lower organisms.

There are, however, also changes of considerable biological importance on the physical side. Man brings with him from his animal ancestors the endocrine secretory mechanism of the reproductive organs: but his life is not subordinated to it in such an iron-bound way. To start with he has gradually lost all semblance of a breeding-season. Traces of it survive in some primitive races, but in civilized communities all one can say is that the number of births may show a slight seasonal variation; and the reproductive organs are capable of function in all twelve months of the year--a state of affairs known, I believe, in no other vertebrate, or at least in no wild species.[33]

In the second place, there has been in the female a further emancipation of the sexual life. In all other mammals the female will only receive the male at certain well-defined periods, which in their turn depend on cyclical changes in the ovaries. In man this restriction has been overcome, and, in spite of the survival of a certain degree of cyclical change in feeling, neither sex is restricted any longer to certain physically-determined periods for the consummation of its sexual life. This is, we may say, a triumph of mind over matter in the human organism, of the mental elements of the sexual life over the purely physical elements.

This is not to deny that the sexual life of man is dependent upon the reproductive hormones. It is apparently necessary for proper activation of the sexual centres in the brain that there should occur a continuous liberation of secretion from the reproductive organs into the blood. Again, the mental activities of man are so much more important than those of other forms that even the cessation of activity of the reproductive organs, for instance in the female at the change of life, or even their total removal, need not prevent the continuation, albeit in a modified form, of the sexual life in its varied indirect manifestations.

Before attempting to probe the intricacies of the mental side of the subject, we had better see what we can learn of the physical. Let us first remind ourselves of one or two facts gained from animal experimentation. In the first place, in mammals the activation of the sexual instincts of one or the other sex appears to be completely or almost completely under the control of the internal secretions of the reproductive organs. Steinach and others have taken new-born male guinea-pigs and have removed their testes and grafted ovaries in their place. The result has been an animal almost completely feminized both as regards body and mind. In some of the animals milk was secreted, and when this occurred they would act as foster-mothers to new-born guinea-pigs of other parents. The reverse operation, the masculinization of females, was equally successful, the animals growing large and showing all the instincts of a normal male and none of those of a normal female.

A similar dependence of behaviour on gonad is seen in fowls. Here nature makes a number of experiments, which have recently been studied by Dr. Crew of Edinburgh. When the ovaries of a hen are affected by a certain type of tumour, the bird stops laying, her comb and wattles enlarge to the size of a cock’s, her spurs grow, she begins to crow, her plumage changes at the moult and becomes cock-like, and finally she becomes indistinguishable from a male. Indistinguishable, even in behaviour: her years of feminine routine in laying and brooding are forgotten: the secretion of the altered ovary now apparently resembles that of a testis and stimulates centres of the brain which would otherwise have remained permanently dormant. She struts and crows, fights and mates, and the memory of the previous part of her life is for all practical purposes lost, since the centres for female activity are no longer stimulated at all.

Various workers have even experimentally produced a state of hermaphroditism in mammals by simultaneous grafting of portions of testes and ovary: the behaviour here oscillates between male and female.[34]

It is quite clear from these and other facts that in higher vertebrates there are present in every individual of either sex the nervous connections which give the possibility of either male or female behaviour; but that normally only one of these two possibilities is realized, since for the potentiality of action given by the nervous connections to become actual as behaviour it is necessary for the nervous system to be activated by the secretion of one or other of the reproductive organs. Castrated animals fail to realize either possibility of normal sex-behaviour, although their nervous machinery is untouched.

There are, further, some facts of observation which, even if they have not yet been fully analysed by experiment, still throw light on the matter. Although many of the most familiar birds--fowls, pheasant, peacock, duck, finches, and so forth--have bright-coloured males and drab females, with marked difference of behaviour between the sexes, there are, as we have seen, many others, such as herons, divers, swans, grebes, moorhens, and auks, in which the sexes are alike in plumage and furthermore show what may be called a “mutual” courtship in which both male and female play similar rôles. In this latter class it seems clear that the secretions of the male and female reproductive organs must be more alike than in the markedly dimorphic species: and this is borne out by some strange facts regarding not merely the courtship but the actions concerned with pairing itself. In the crested grebe and the little grebe, for example, close observation has shown that either member of the pair may assume the passive “female” attitude or the active “male” attitude in pairing: and in the moorhen we meet with the still more extraordinary phenomenon of double pairing, in which an act of pairing with male and female in normal position is immediately followed by a second act in which the normal position is reversed.[35] It would appear in such cases that the similarity of male and female internal secretion is so great that quite slight changes in nervous or metabolic activity can cause the nervous centres for the opposite sex’s mode of behaviour to become activated.

In human beings we are confronted with various grades of sexual organization and behaviour besides the typically feminine and the typically masculine. In the first place it is matter of common knowledge that many women, who so far as their physical reproductive capacity goes are perfectly normal, show various mental traits which are more characteristic of men, and vice versa. What is more, the “masculinoid” woman (to use the current jargon) tends physically also to be less feminine, to have the feminine secondary sexual characteristics in stature, form of skeleton, distribution of fat, breasts, etc.--less strongly developed than normal, while the “feminoid” man shows the reverse tendency.[36]