Inheritance of acquired characteristics

“ While it is true that too much importance cannot be placed upon the subject of heredity, the inheritance which we receive not only from our parents and grandparents but even from our great-grandparents, and while it is true that all that can be acquired in character and culture, both intellectual and physical, is transmitted from the parents to their children ”

“ But if acquired modifications do not tend to be transmitted, if the use or disuse of organs or faculties does not similarly affect posterity by inheritance, then it is evident that no innate improvement in the race can take place without the aid of natural or artificial selection. ”

“ They will inherit from a mixture of unlike characteristics contributed by unlike peoples, and in their inheritance they will have certain of these characteristics in full identity, while certain others they will not have at all. ”

“ Every one must have heard of cases of albinism, prickly skin, hairy bodies, &c., appearing in several members of the same family. If strange and rare deviations of structure are truly inherited, less strange and commoner deviations may be freely admitted to be inheritable. Perhaps the correct way of viewing the whole subject would be, to look at the inheritance of every character whatever as the rule, and non-inheritance as the anomaly. ”

“ The whole subject of inheritance is wonderful. When a new character arises, whatever its nature may be, it generally tends to be inherited, at least in a temporary and sometimes in a most persistent manner. ”

“ Now, any change of character thus induced with advancing years in the individual might easily be inherited at an earlier age than that at which it first supervened, and thus become characteristic of the mature species; or again, such changes would be apt to follow from variation, independently of inheritance, under proper conditions. ”

“ In other words, the possession of specific qualities by a class—qualities not received by inheritance—affects in no way the evidence that the general qualities of the class were received by inheritance. We have recognized this principle at each step in the present discussion. For example, we saw that the national characteristics of a people arise from other causes than inheritance, but this did not lead us to conclude that the race characteristics of the same people were not inherited. In fact, every person affords in his own facial features an illustration of this principle. ”

“ There remains the terminological difficulty that, as I have tried to show, the individual may display characters which were potential in the germ, inherent and necessarily inherited, though they did not appear in the parent nor yet in any ancestor. We have to face the paradox, then, that in natural inheritance a parent can transmit what he has not got, though this does not apply to the unnatural inheritance of property in human society. ”

“ The idea of heredity has made familiar the notion that the equipment of the individual, mental as well as physical, is an inheritance from the race: a capital inherited by the individual from the past and held in trust by him for the future. ”

“ There had been a wondrous involution from centuries of great history, according to subtle, silent laws of hereditary inheritance, in very blood and life, of tone, and quality, and temper, and now there is evolved, evoked, just that of power which tells of kinship with those who have gone before. ”

“ But now—and this is a very important law of inheritance—if such a transmission of a favourable character is continued through a series of generations, it is not simply transmitted in the original manner, but it is constantly increased and strengthened, and in a last generation it attains a strength which distinguishes this generation very essentially from the original parent. ”

“ In this chapter we shall consider the significance of heredity and environment in their relation to character.
§ 2. Physical Heredity. All character has a physical basis. Every child has a body, and without a body it could have no character. In studying the development of character, we must therefore first examine the meaning of physical heredity. Heredity has been defined as the genetic relation that binds one generation to another. The individual's inheritance includes all that he is, or has, to start with, in virtue of this genetic relation. ”

“ Hence this class of biologists insist that the explanation of heredity given as a simple handing down from generation to generation of a germ plasm is not complete, and that while it is doubtless the foundation of heredity, it must be modified in some way so as to admit of the inheritance of acquired characters. There is no question that has excited such a wide interest in the biological world during the last fifteen years as this one of the inheritance of acquired characters. ”

“ Formation of Instincts.—The structure produced by repetition of voluntary acts, and which, as we have seen, determines habits, by the law of inheritance is transmitted in a slight degree to the next generation. I say in a slight degree only, because inheritance is from the whole line of ancestry and not from the immediate parents alone. The inheritance from the immediate parents is greater, it is true, than from any one of the series of previous generations, but infinitely less than the sum of inheritances from all previous generations. ”

“ There is nothing inherently impossible in this theory; indeed, if we allow that the transmission of inheritable characteristics is purely material, and it may be, there is only one other conceivable way in which it can occur. ”

“ If a father has blue eyes and the son has blue eyes, what can be clearer than that he inherited them? If the father stammers and the son stammers, who can doubt but that it came by inheritance? If the father is a musician and the son a musician, we say very glibly that the talent was inherited. ”

“ As a matter of fact, we know so little of the numbers of ancestors from all of whom we may inherit, and we understand so little of the conditions determining the inheritance of given characteristics, that we are not yet in a position to entertain expectations at all. All we know is, that we do not generally get so far as finding grapes on thorns and figs on thistles. The interesting subject of heredity still offers a wide field to the observer. ”

“ We believe this same principle not only harmonizes with, but is nothing more nor less than a great general law of increase, based upon the perfectionism of all organization and harmony of function; and what are denominated "laws of variation" may be explained by the laws of hereditary descent. When we take into consideration the fact that the true law of propagation is based upon a perfect standard in nature, all changes or deviations from that standard or model result from what are properly called laws of inheritance. ”

“ Now that you have before you, in outline, the problem of mental inheritance, its debt to biology, and the present necessity—if the problem is to advance—for the analytical treatment of traits by a science of individual differences, let me in closing return to my earlier remarks touching the import of inheritance in human history. I urged that human knowledge and human obligation have grown out of proportion to human talent. ”

“ Whenever the means have been at hand, the family stock from which each man has been derived, has been minutely traced. The question of inherited traits is becoming yearly one of increasing interest, and most striking results come from a comparison of facts upon this subject. The fusion of different races is said to produce marked results on the characteristics of the human being. ”

“ Yet it would be wrong to conclude that the faculty of speech is acquired, or is absolutely not inherited. Whatever properties of organisms are constantly repeated periodically are called hereditary; whatever endures through many generations is called inherited. ”

“ Independence of Inheritable Characters.—It has been found that many truly heritable characteristics or traits of an individual, whether plant or animal, are comparatively independent of one another and may be inherited independently. ”

“ It is quite otherwise with the phenomena of heredity. We know nothing even of the proximate cause of any single phenomenon; far less of that ultimate cause in which all these phenomena had their origin. The inheritance of a trait of bodily figure, character, or manner is a mystery as great as that other and cognate mystery, the appearance of some seemingly sudden variation in a race which has for many generations presented an apparently unvarying succession of attributes, bodily, physical, or mental. ”

“ In strict accuracy, the law of ancestral inheritance must be described as giving means of determining the probable deviation of any individual from the mean of his own generation, when the deviations of some or all of his ancestry from the types of their respective generations are known. ”

“ In other words, the young folk present not only an individual continuity with their organic predecessors which is heredity proper, but with their social predecessors also. The elements of organic continuity, which we usually think of first of all as organic though of course psychic also, are conveniently distinguished as the inheritance—a term in fact which the biologist seeks to deprive of its common economic and social senses altogether, leaving for these the term heritage, material or immaterial alike. ”

“ Concerning those individual differences of which heredity is the controlling cause, two facts are worthy of note. First, that human nature is very highly specialized and that inheritance may be in terms of special abilities or capacities. For instance, artistic, musical, or linguistic ability, statesmanship, power in the field of poetry, may be handed down from one generation to the next. ”

“ It talks, for example, much of 'hereditary' and non-hereditary peculiarities, and some of us can remember a time when our friends among the biologists seemed almost ready to put each other to the sword for differences of opinion about the inheritability of certain characteristics; but no one seems to trouble himself much with the question a philosopher would think most important of all—precisely what is meant by the metaphor of 'inheritance' when it is applied to the facts of biology. ”

“ There are two reasons why we should consider the good and bad characteristics which may be ours through inheritance. In the first place, heredity is not fatality, and we are not absolutely obliged to follow the paths which our ancestors marked out for us, and in the second place, we can, by understanding our own characters, mark out better paths for our posterity. ”

“ The gifts that come to us through inheritance are ours without blame or credit to us but they bring with them the responsibility of their use. We are responsible for maintaining or increasing our dower of health by obedience to physical laws; responsible for the cultivation of our intellects, for the development of inherited virtues, and the annihilation of inherited vices.
If you study your characteristics and talents 26 you find that they repeat those of your ancestry. ”

“ Other Inheritable Conditions in Man.—While many pedigrees show beyond dispute that such qualities as musical ability, literary ability, memory, calculating ability, mechanical skill, longevity, peculiarities of handwriting, obesity and muscular strength, for example, are inherited, their modes of inheritance have not yet been sufficiently analyzed to express them exactly. ”

“ Turning to the influence of heredity, we recognized that by it are determined all the most fundamental features of each race and type of man, and that often the individual reverts to the traits of the one or the other of his parents, or of his remote ancestors, in such manner that one trait may belong to one ancestor, another to another. ”

“ We inherit thoughts as we inherit wealth; we inherit customs and laws and forms of worship, and indeed [Pg 30] our whole mental furniture; we can add enormously to our inheritance, and can transmit the augmented fund to our descendants. But the other process of inheritance, to which the word "heredity" is taken to apply, is not, immediately at least, cumulative. We inherit the old faculties, bodily and mental, unaltered, or with infinitesimal alterations, though we live in a different environment, and are ourselves as much altered as our environment. ”

“ The trunk of the elephant, the fin of the fish, the wing of the bird, the cunning hand of man and his complicated brain—and, in short, all organs and faculties whatsoever—can only have been moulded and developed by use—by usefulness and by using—but not necessarily by use-inheritance, not necessarily by directly inherited effects of use or disuse of parts in the individual. ”

“ After subtraction of the necessary amount for the greater likeness in training, that the individuals of like ancestry will have, whatever amount is left will necessarily, represent the actual inheritance of the child from its ancestors—parents, grandparents, and so on. ”

“ Enough, however, is known of ancestry and the infinite marks of inheritance on every structure as well as enough of the reaction of the human machine to the varied environment that surrounds it, to make it clear that if one were all-seeing and all-wise he could account in advance for every action of every man. ”

“ No one can doubt the law of hereditary transmission. Our inherited and acquired characteristics are sure to be transmitted to our descendants. Indeed, so thoroughly does character permeate one's entire being that it might be said of each drop of blood that in its characteristics it is a miniature of the person in whose body it was secreted. Eminent characters do not emanate from degenerate parents; and neither is the reverse true, except as the result of adequate reversionary influences. ”