FOOTNOTE
[1] The Spaniards have lost possession of Cuba and the Philippines since this was first written.
[CHAPTER II.
THE STANDPOINT OF BIOLOGISTS.]
[Lamarck’s View on Heredity.]
In this chapter I shall invite attention to what the biologists have discovered concerning racial change, and the conditions under which the change occurs.
Before the simultaneous publication in 1858 by Darwin and Wallace of their “Law of Natural Selection,” biologists believed in the Lamarckian view of heredity, a notable follower of Lamarck being our own Herbert Spencer. Lamarck briefly sums up his views in the following passage: “All that nature has caused individuals to acquire or lose through the circumstances to which their race has found itself for a time exposed, and consequently, through the predominant exercise of certain organs, or through a failure to exercise certain parts, it preserves through heredity to the new individuals that are produced by them, provided the changes acquired are common to the two sexes, or to those that have produced these new individuals.” Now this view is the one that is popularly held to this day, and it is the very view which the new school of biologists have set themselves to combat.
Lamarck would have accounted for the long neck of the giraffe by supposing that in remote ages its ancestors were short-necked like other animals, but that it exercised this neck in browsing off high trees, that the necks elongated in consequence of this stretching, and that this elongation was transmitted by heredity, although even by imperceptibly slight degrees, from one generation to another, until the part gradually grew to the present length. Lamarck would cordially have agreed with the modern educationalist in the belief that the children of a man who gives himself to learning will have better head-pieces than if the father had been a soldier or professional cricketer.
In this Lamarckian view of heredity we have two ideas; first, that fresh characters may be acquired during an individual’s lifetime, due to the action of his surroundings or environment; and secondly, that these fresh characters are transmitted to the offspring and may produce in time marked racial change. The first idea is undoubtedly and admittedly true. The build of a soldier, a clerk, a ploughman, and an athlete is distinctive; the horn that grows upon a mechanic’s hand, and the development of the muscles of a blacksmith’s arm, are commonplace facts. It is the second idea, the supposed transmission of these acquired characters, which is now so seriously called in question.
[Darwin’s Law of Selection.]
The law of selection brought forward by Darwin and Wallace may be stated as follows:—No two offspring of the same parents are quite similar to each other, indeed they often vary to a considerable extent. Under the conditions in which they live, some of these offspring will have an advantage over the rest, dependent upon an inborn peculiarity. Inasmuch, therefore, as more progeny are produced than can ever survive, those most fitted to these surroundings will have the better chance of living. These will, in larger numbers, perpetuate the race and transmit their inborn qualities to the race, thus gradually eliminating the less suitable ones.
Keeping to the case of the giraffe, Darwin and Wallace would explain the length of the neck somewhat as follows: With Lamarck they believe that the ancestor was short-necked, but the subsequent elongation they would explain in quite another way. They would take for granted that there are times when grass and foliage are scarce, that short-necked animals would soon exhaust the herbage and shrubs, but that the taller shrubs and trees would afford subsistence to animals with a higher reach. Amongst the ancestral giraffes those born with the longest necks would at such times have an advantage over the rest, who in large numbers would die out. The longer necked ones, more suited to their environment, would perpetuate their inborn quality of long-neckedness: of the next generation those again with the longest necks would survive, and so on. The Darwin and Wallace school of thinkers would, I quite believe, be prepared to state that by attention to education it would be possible to improve the mental qualities of the race, but they would teach that this improvement could only take place provided that the system made it possible for the clever man and woman to earn a better livelihood, marry early, and have large families, while the stupid ones should produce fewer children, a condition which at present is far from being the rule.
Fig. 1.
Diagram to illustrate: A, the transmission of acquired characters, B, modification of type by natural selection. In A an individual of rounded proportions, at the top of the diagram, has two children. Environment is represented by a board with holes through which they must pass. In so doing they become thinner, transmit the thinness to their children, and so on. In B, a man of rounded proportions has two sons who vary, one being fat, the other thin. The fat one cannot get through the hole in the board; but the thin one does, has children who again vary, the thin one having an advantage.
[Three Ideas involved in Selection.]
Now there are three ideas in this law of natural selection: first, that there are inborn variations among the offspring even of the same family; secondly, that these various individuals living in surrounding conditions on the whole uniform and common to all of them, will start in life, some with an advantage and others with a relative disadvantage, and that those possessing an advantage will, more of them, tend to produce offspring; thirdly, that the variations, inborn in this case and not acquired, will probably be transmitted. That there are marked variations—physical, mental, and moral—among a litter of kittens or puppies is within the experience of everyone who has kept them, and that variations in human families are as marked is known to everyone who has brothers and sisters. Even twins frequently differ considerably from each other, and it is said that the last years of the lives of the Siamese twins were sadly marred by their opposing views as to the rights and wrongs of the American Civil War! It stands to reason also that these variations may be of advantage or disadvantage to their possessors, and that among animals and plants, where there are no social props given to the weak, the variations may and do determine survival. To give an idea of the rigorous operation of selection which we find among the lower animals, we have only to enumerate the number of the progeny produced by each pair, which is often prodigious, and knowing as we do that the number of individuals in a species remain virtually the same in a given district for long periods of time together, we conclude that the room of the parents is just filled by a younger pair, and all the excess of their progeny over and above this one pair must have succumbed to surrounding want and hardship. To give one concrete example out of hundreds that might be selected, let us take the case of the golden eagle given by Weismann in his essay on the “Duration of Life.” He says: “Let us fix the duration of life in the golden eagle at sixty years, and its period of immaturity (of which the length is not exactly known) at ten years, and let us assume that it lays two eggs a year, then a pair will produce one hundred eggs in fifty years, and of these only two will develop into adult birds, and thus on an average a pair of eagles will only succeed in bringing a pair of young to maturity once in fifty years; and so far from being an exaggeration, this calculation rather under-estimates the proportion of mortality among the young.”
But in all probability most of us are more conversant with the ways of the domesticated cat than with those of the golden eagle. The cat produces its first litter of three or four before it is a year old. Its kitten-producing life lasts, say, for eight years, and it may, on a low estimate, be supposed to produce a litter of four kittens once in each year. In all a cat will have, on a fair estimate, thirty-two kittens, and may be a great-great-great-great-great-great-grandmother in her lifetime, yet we do not observe in town or village such an alarming increase in the cats from year to year. Their number is pretty stationary, kept so by the enormous destruction of their progeny. The enormous capacity for reproduction of a race of animals, where for a time their surroundings are favourable, will be appreciated by the lowland farmers whose fields were laid waste a few years ago by armies of short-tailed field-mice, whose natural enemies, the hawks, the cats, and the weasels, had been extensively shot or trapped.
The struggle to survive among the savage tribes of man must be excessive. Whole races come and go, and their survivors again fall victims to privations, disease, or natural enemies, before the white man with his better brain and capacity for adaptation.
[Selection is a Fact, not a Theory.]
The third idea in the law of natural selection—namely, that inborn variations are transmitted—is also a fact that is universally admitted not only among biologists at the present day, but by those who trust only to their everyday experience. “The child has its father’s temper,” or “its mother’s eyes,” are expressions heard in every nursery, while the innumerable cases of the transmission of inborn drooping eyelids and supernumerary fingers and toes show the same thing in a more striking manner.
The law of selection is therefore no mere unproved fancy, it is a statement of fact, and of one which is so obviously true that it is now almost universally admitted, not only among specialists, but by most intelligent and educated persons. It was understood, and its significance partly appreciated by Malthus, and I find that even he acknowledges a prior claim of Franklin’s.[2] Romanes[3] tells us that the idea occurred in 1813 to Dr. Wells, and in 1831 to Mr. Patrick Matthew, and the wonder is that other thinkers have passed unnoticed such an obvious phenomenon.
[How much is explainable by Selection?]
While, however, natural selection as an agent capable of producing racial change is accepted by almost every well-instructed biologist, there are some who are still inclined to give some value to the operation of the Lamarckian transmission of acquired characters. They do not deny that to selection is due by far the most obvious racial changes, and that experimentally the most potent factor in the production of a new variety of a plant or animal is selection. They are, however, inclined to believe that along with this, there may be some transmission of acquired character, only discernible after the lapse of many generations. Darwin himself thought that this was the case; he held that certain racial distinctions were due to the action of the environment on the parents and the transmission of the change thus produced upon their offspring. In his great work upon “The Variation of Animals and Plants under Domestication,”[4] he enumerates some of these. They may be divided roughly into two classes: first, instincts and habits; and, secondly, results of use and disuse. Darwin believed that the trained habits of dogs and horses, the tameness of the rabbit and other domestic animals, were due to the direct and transmitted effects of man’s contact. He held that the large size of the leg and small size of the wing of the domestic as compared with the wild duck are gradually acquired and transmitted by use and disuse.
But Darwin, as Huxley points out,[5] was inclined to lay less stress upon the transmission of acquired characters in his later writings; and we find that in the “Origin of Species” he is inclined to abandon them altogether, and accept the position now held by the Neo-Darwinian School of Galton and Weismann. He says (pp. 117, 118), “If under changed conditions of life, a structure, before useful, becomes less useful, its diminution will be favoured, for it will profit the individual not to have its nourishment wasted in building up useless structures.... Thus, I believe, natural selection will tend in the long run to reduce any part of the organism as soon as it becomes through changed habits superfluous.”
Just as Darwin himself, as time went on, laid more and more stress upon the importance of selection, and less and less upon the transmission of acquired characters, most naturalists have tended to follow him in the same direction. It may be said, I think, without gainsay, that, since Darwin’s death, the most important and outstanding work done by the biologists has been the uprooting of much of the Lamarckian doctrine, originally held, not without question, however, by Darwin himself. The biologist of to-day is more Darwinian than Darwin, and explains on the Darwinian hypothesis even those cases which had presented difficulties to Darwin’s own mind.
[Galton and Weismann.]
Amongst those who were pioneers are Galton and Weismann, and, curiously enough, in England and Germany these two men, independently of each other, came to the same conclusion respecting the non-inheritance of acquired qualities, and pointed out that the facts of development indicate that the generative matter is passed on from one generation to another, remaining intact in the body of the parent, and that we have no reason to suppose that it could be influenced by changes in other parts of the parental organism. It is not uninteresting to note and contrast in these two investigators the action of the typically English and typically German mind, more especially as the comparison is perhaps equally complimentary to the two nationalities, and indicates the value of results arrived at by workers of different individualities.
Galton was first in the field, and as long ago as 1876[6] made the following clear and concise statement:—“The conclusion to be drawn from the foregoing arguments is that we might almost reserve our belief that the structural cells can react on the sexual elements at all, and we may be confident that at most they do so in a very faint degree: in other words, that acquired modifications are barely, if at all, inherited in the correct sense of the term.” Thirteen years later[7] he expresses himself in practically the same terms. An untiring investigator, chiefly in the facts of human heredity, he briefly sums up as above one of his most important general conclusions. It is all he has to say, it is all that his facts permit him to say.
In 1882, Weismann[8] questioned whether there is as yet any proof that acquired characters are transmitted; he writes:—“The theoretical conception of variation as a reaction of the organism to external influences has also not yet been experimentally shown to be correct. Our experiments are still too coarse, as compared with the fine distinctions which separate one individual from another, and the difficulty of obtaining clear results is greatly increased by the circumstance that a portion of the individual difference always depends upon heredity, so that it is frequently not only difficult, but absolutely impossible, to separate those which are inherited from those which are acquired.”
Since that time, Weismann, in a series of important essays,[9] indicating a profound knowledge not only of comparative morphology, but of the habits and modes of life of a vast number of animals and plants, has shown that many of the cases which Darwin was doubtful about may reasonably be explained by selection, and he has marshalled a vast mass of evidence in support of the argument that acquired characters, experimentally produced, are not transmitted.
These essays are profoundly interesting, and will supply food for thought for many years, but it must be admitted that Weismann has gradually been led away to speculations of the most elaborate kind, built upon the most flimsy substratum of fact. There is evidence of this tendency even in his early writings, but in his later essays, especially his recent work on “The Germ Plasm: a Theory of Heredity,”[10] the speculative part quite overpowers the rest.
As those who are interested in heredity will probably read his works with the greatest attention, I have ventured in an [appendix] to make clear what in his works may, in my opinion, safely be looked upon as speculative rather than legitimate, or even provisional, generalisation, and what, therefore, may be altogether omitted from the study of a practical problem such as that with which we are concerned.
[Are Acquired Characters transmitted?]
The practical issues which both Galton and Weismann have raised cannot, however, be underestimated, and, in respect to the non-inheritance of acquired characters, the mass of modern thinkers may already be said to have given their allegiance to the views of those two thinkers.
But we are living in times when mere authority is at a discount, and we may well demand the facts for ourselves. The point which we are inclined to question is one as to which a doubt was often present in Darwin’s mind. Granted that selection is a factor, we are inclined to believe that the transmission of acquired characters must also take place, at any rate, to some extent. In attempting to decide this question upon the facts themselves we may take two lines of research. In the first place, we may examine every case of racial change, the production of new or different parts, the development of a new instinct, or the degeneration or loss of parts or instincts present at some past epoch. If in every case we are not compelled to exclude natural selection, and if in every case that we can directly and experimentally follow, selection is the outstanding factor, then there is strong presumptive evidence that racial change is caused by selection and not by the inheritance of acquired characters. In the second place, we may artificially induce the acquisition of some character, and notice whether this is transmitted; if it is not, then the general operation of this kind of transmission is rendered very doubtful.
[Many Cases of Supposed Transmission to be explained by Selection.]
It is upon these two lines that Galton and Weismann worked, and we may now follow in rough outline the evidence they adduced. Darwin had been able to explain, to universal satisfaction, the evolution of many types and varieties, as a result of selection alone; though certain cases of the supposed inheritance of use and disuse, and of acquired instincts, caused at times doubts to arise in his mind. But Weismann has questioned this inheritance, and has shown that—as Darwin himself sometimes believed—these may readily be explained by selection alone. The gradual increase, generation after generation, in the size of a useful limb or the perfection of a valuable organ of sense may readily be explained by selection. The fact that the limb or organ is of use to the race in its struggle will determine the survival of those born with these serviceable parts well-formed, and these in their turn will produce others as favourably or more favourably constituted, from whom further selection can take place. We cannot shut our eyes to the operation of selection in such instances, nor have we any reason for saying that part of the effect must be due to some other cause. In the case of organs which become useless and finally disappear in the course of generations, a selective agency will sufficiently account for this disappearance. As Darwin himself pointed out, a useless organ is an expense and a drain upon an animal’s capital; it requires blood, and its exercise uses up some of the sum total of energy the animal possesses. The truth of this can be shown experimentally, as when compensatory growth occurs in the rest of the body after amputation of a limb, or when one lung or kidney enlarges subsequently to the disease or removal of the other. In cases where an organ is useless, those who have it badly developed, and in consequence have other and useful parts more fully formed, will have a distinct advantage over those born with a well-formed but useless organ. We may thus explain the small size of the wings of the tame as compared with the wild duck, an instance in which Darwin saw difficulty in excluding inherited disuse. In this way we may explain the occurrence of the still smaller wings of the running ostrich and apteryx; also the blind fish of the Kentucky Cave, and the visionless eyes of the burrowing mole. As an illustration, an animal or man may, in this respect, be compared to an individual with a given amount of capital, who, if he spends his money in one direction, will thereby have less for another purpose. In this way a big leg may be obtained at the expense of a small arm, or a good ear be the cause of an indifferent eye.
When we turn to the question of the supposed transmission of acquired instincts and habits, we find that it is possible by means of the principle of selection, to explain some, at least, of the cases which presented difficulties to Darwin’s mind. Thus the tameness of rabbits, cats, and dogs, which animals have for countless generations been subjected to domestication, need not necessarily be accounted for by supposing that the results of training are transmitted. For it is easy to understand how those that would have rebelled most against man’s authority, and who were by nature the least tractable, would have been less cared for by man, and probably would finally have suffered extermination, while the docile received his attention, and were allowed to reach maturity and perpetuate the race. That this selection must be going on at the present time is very obvious, and as instances we may note the savage dogs that are constantly being destroyed, and the house dogs and domestic pets that are, in most cases, continually being selected from the docile animals and those of good temper. A dog that does not possess these good qualities can have no existence in town or village, and so by continual extermination of the unfriendly, the “friend of man” has gradually been evolved.
[Paucity of Experimental Evidence of such Transmission.]
Turning now to those cases in which characters can be acquired or experimentally stamped upon an individual, we find that no single reliable instance can be adduced in which transmission takes place. Mutilations have been practised upon male infants by Jews and other Semitic races for thousands of years; yet, in spite of this, the operation has still to be performed, for the lost parts appear in the offspring of to-day as in the earlier periods of their race’s history. Certain breeds of dogs and sheep have for many generations been systematically docked, and yet the young are born with as long tails as those of other breeds. Chinese women have compressed their feet from times long past in their history, yet Chinese female infants are still born with large feet, and have to undergo afresh the torture of their compression. More curious still, for it affects an organ of paramount importance, the brain, there is a tribe of Indians who flatten their heads in early life, entirely changing the shape not only of the skull, but of the brain itself, yet their children are born with normal rounded heads; the induced change is not transmitted.
It must be admitted that this evidence is pretty strong, and we need not wonder that it has produced such widespread conviction, although it has been so lately taken up by the thinking public.
[The Reproductive and the Body Cells.]
The body of a plant or animal is composed of small living bodies, most of them of microscopic size, called cells. These lead, to a certain extent, individual lives, and have individual characters, but they are built, as it were, together, like the bricks and stones of a house, to form the body. The cells are, all of them, nourished by the blood and lymph, and some are connected together by strands of connecting matter termed nerves. All the cells of the body are descendants from a single fertilised egg, which has resulted from the fusion of a paternal and maternal sexual cell. Among the cells of the body, and situated in special organs, are the sexual cells, likewise nourished by blood, but not connected by nerves with other parts of the body.
[Reproductive Cells unaffected by Local Changes in the Body Cells.]
Now there is no reason to suppose that these sexual cells residing in the bodies of the parent will be influenced by a change in the muscle or brain cells of the parent unless this change in some way or another influences the blood, the common go-between. But the blood is now known to be but a food and oxygen carrier, and an eliminator of used-up products. It is like a river laden with vessels carrying corn for the food of the big city, and nothing more. The life, the energy, the character of the body is the sum of the lives, the energies, and the characters of the cells—although these necessarily require the nourishment derived from healthy blood—just as the life of the city is the sum of the life of its citizens who require the nourishment of the corn.
[Constitutional Change may, though it rarely does, affect the Reproductive Cell.]
Let us suppose that an average healthy man during his lifetime acquires, by use, accident, or disease, some change in his right arm. There is no reason to suppose that the sexual cells, rather than any other cells in the body, will be affected. If, on the other hand, this local change in the arm affects the blood, depriving it of nutritive power, or casting into it obnoxious matter, then it is possible that all the cells of the body may be affected. We have many instances of such a thing, as when the blood and whole constitution are involved after maybe a primary local affection, and when, in consequence, the hair drops off, or marks and irregularities of the nails appear. In these cases the sexual cells may suffer from want of nourishment, or from what we may term a poison, and may produce less vigorous and perhaps diseased or malformed offspring, but they will show no tendency to develop in the offspring that primary local affection which caused ailment in the parent. But, as we shall see in the [next chapter], the sexual cells in most cases get off scot-free, and the most dangerous acquired constitutional diseases leave no trace of their passage upon the reproductive elements. It is indeed difficult to point to a case, with the notable exception of syphilis, in which acquired constitutional blood disorders leave any trace in the organisation of the progeny, and we are indeed fortunate that this is so.
There seems to be some evidence that we may stunt the growth of a plant or animal by insufficient or unsuitable food, and that all the cells of the body may thereby be reduced in size, the sexual cells among the rest, and that these reduced cells give rise to small progeny in the next generation. Here again the evidence in the case of animals seems rather doubtful, and rests on a few statements, such as that of De Quatrefages, that horses taken from Normandy to the hilly and less fertile country in Brittany become distinctly smaller in the course of three generations. In our own country large horses are found in the plains and small horses and ponies in the hilly districts of Wales and Scotland. But the obvious utility to man of small breeds in hilly districts, and of heavily-built horses on the plains, and the fact that horses have been bred for hundreds of years in view of their services to man, throws great doubt upon this particular evidence of De Quatrefages’, and we may well leave it out of account, unaccompanied as it is with evidence as to the total exclusion of the interbreeding of the Normandy with the Brittany variety.
On the other hand, among plants it really appears as if by adjusting the soil and climate you may produce stunted varieties, whose seed produce small plants. The poor and exposed ground of our hilltops are covered with dwarfed varieties of the bigger plants growing luxuriously in the adjacent plains, and a classical case mentioned by Lemaire[11] is that of the hemp which, removed from Piedmont to the less suitable soil of France, becomes a smaller variety, growing to only half its former height in the course of two or three generations. The enormous dwarfing that one can subject a plant to is illustrated in the case of the conifer, which the Japanese can cause to remain the size of a tiny shrub during its hundred years’ growth, by simply keeping the soil at the starvation edge, and by pruning the branches and roots.
It appears then to be pretty certain that every man and woman possesses a store of sexual cells, derived directly from the original sexual cells from which he or she was developed. These in the main are like the original cell, being as they are of its substance, but they show minor differences amongst themselves, and give rise in their turn to offspring no two of which are alike. These sexual cells, residing within the paternal or maternal body, are uninfluenced by the course of life led by that body, except, perhaps, in some few cases in which the whole system and the blood are impoverished, saturated with alcohol, or infected with the microbes of disease, which microbes in some cases, perhaps, directly attack the sexual cells.
[The Facts of Evolutive Selection known to the Gardener and Breeder.]
Scientific men are often very slow at arriving at a truth, and there are many instances of valuable knowledge held by sections of the people in perhaps an empirical fashion, which has at last found acceptance by the learned. The practical results of all this biological teaching has been in the hands of cattle-breeders and nurserymen for centuries. The various breeds of cattle have been produced by man, not by any new method of ventilating the cow-sheds, or by some freshly discovered patent fodder, but simply by selecting for breeding purposes those individuals that most suited the breeder’s purpose. The racing stallion was kept which most resembled a greyhound, the hog that most resembled a beer barrel, and the cow that gave the best combination of milk and flesh. The gardener produces the hundreds of new varieties placed every year in the market by keeping the seeds and propagating from any variety he may wish to perpetuate, and these varieties are always spontaneously occurring. He perfects his stock by selecting the seed only from the very best.
The testimony not only of the learned but of those who in their lives, unbiassed by any theory, have been engaged in modifying breeds of animals and plants, is unanimously in favour of the view that selection is the only, or, at any rate, by far the most powerful factor in producing racial change. So far these facts have had little or no application to the question of human race progress. People are still too much biassed by archaic anthropocentric ideas; they view man by himself, under his own special laws, and would often be shocked by an attempt to draw obvious parallels between him and the lower animals. Amongst the thinking few this attitude has changed, and broader and sounder views are rapidly gaining ground.
People, too, are apt to feel what may be called a false delicacy in speaking of questions relating to race change, but this may more rightly be termed the shyness necessarily associated with an unusual topic of discussion. We English laugh at the American woman who, from notions of extreme modesty, will not speak of the “leg” of a piano; but we in our turn draw our own often exaggerated lines, beyond which we will not pass. Just as there is no subject which will not yield food for the evil-minded, so there is no subject—having to do with the laws of nature—which cannot be naturally approached in all simple-mindedness. As soon, therefore, as it is realised, that this question we are dealing with is one which demands not only our closest attention, but also the advantage of public and private discussion, so soon shall we have acquired the habit of regarding it in quite a matter-of-fact and pure-minded way.