Devolution.
As in the evolution of an individual tree some branches flourish while others fail; as in a forest some trees grow tall and stretch out wide branches while others are stunted and die out; as in the onward and upward progress of any species some individuals are in advance of the main body while others lag behind; so in the forward march of the collective human mind across the centuries some individual minds are in the van of the great army, while in the rear of the column stagger and fall vast numbers of defective specimens.
In any race the stability of any faculty is in proportion to the age of the faculty in the race. That is, a comparatively new faculty is more subject to lapse, absence, aberration, to what is called disease, and is more liable to be lost, than an older faculty. To many this proposition will seem a truism. If an organ or faculty has been inherited in a race for, say, a million generations, it seems, a priori, certain that it is more likely to be inherited by a
given individual of that race than is an organ or faculty which originated, say, three generations back. A case in point is what is called genius. Genius consists in the possession of a new faculty or new faculties, or in an increased development of an old faculty or old faculties. This being the case, it seems to Galton [92] necessary to write a good sized volume to prove that it is hereditary. So far was that from being an obvious fact that even yet the heredity of genius is far from being universally accepted. But no one ever wrote a book to prove that either sight, hearing, or self consciousness is hereditary, because every one (even the most ignorant) knows without any argument that they are so. On the point in question Darwin says, speaking of horses: "The want of uniformity in the parts which, at the time, are undergoing selection chiefly depends on the strength of the principle of reversion" [67: 288]. That is, parts or organs which are undergoing change by means of selection are liable to lose what has been gained by reverting to the initial condition. And again he says: "It is a general belief among breeders that characters of all kinds become fixed by long continued inheritance" [67: 289]. In another place he speaks of the "fluctuating and, as far as we can judge, never ending variability of our domestic productions, the plasticity of their whole organization" [67: 485], and he at, tributes this instability to the recent changes these have undergone under the influence of the artificial selection to which they have been subjected. And in still another place Darwin speaks of "the extreme variability of our domesticated animals and cultivated plants."
But it is scarcely necessary to carry this argument further. Any one who is willing to give the matter a thought will admit that the shorter time an organ or faculty has been possessed by a race the more unstable must it be in the race, and, consequently, in the individual; the more liable will it be to be dropped; the more liable to be defective; the more liable to vary; the more liable to be or to become imperfect—as we say, diseased. And that, per contra, the longer time an organ or faculty has existed in any race, the more certain it is to be inherited and the more certain it is to assume a
definite, typical character—that is, the more certain it is to be normal, the more certain it is to agree with the norm or type of the said organ or faculty. In other words, the less likely it is to be imperfect—what we call defective or diseased. This being allowed, it will readily be granted: 1st, That the race whose evolution is the most rapid will (other things being equal) have the most breakdowns; and, 2d, That in any given race those functions whose evolution is the most rapid will be the most subject to breakdowns.
If these principles be applied to the domesticated animals (which have, most of them, within the last few hundred generations, been much differentiated by artificial selection), they will explain what has often been looked upon as anomalous—namely, the much greater liability to disease and early death of these as compared with their wild prototypes. For that domestic animals are more liable to disease and premature death than wild, is admitted on all hands. The same principle will explain also how it is that the more highly bred an animal is—that is, the more widely it has been differentiated in late generations from a previous type—the more liable will it be to disease and premature death.
Taking now these general rules home to ourselves—to the human race—we find them to mean that those organs and functions which have been the latest acquired will be most often defective, absent, abnormal, diseased. But it is notorious that in civilized man, especially in the Aryan race, the functions which have undergone most change in the last few thousand years are those called mental—that great group of functions (sensuous, intellectual, moral) which depend upon, spring from, the two great nervous systems—the cerebro-spinal and the great sympathetic. This great group of functions has grown, expanded, put forth new shoots and twigs, and is still in the act of producing new faculties, at a rate immeasurably greater than any other part of the human organism. If this is so then within this great congeries of faculties it is inevitable that we should meet with constant lapses, omissions, defects, breakdowns.
Clinical observation teaches day by day that the above reasoning
is solidly grounded. It presents lapses of all degrees and in unlimited varieties; lapses in sense function, such as color-blindness and music deafness; lapses in the moral nature, of the whole or a part; in the intellect, of one or several faculties; or lapses, more or less complete, of the whole intellect, as in imbecility and idiocy. But over and above all these lapses, and as a necessary accompaniment of them, we have that inevitable breaking down of function, once established in the individual, which we call insanity, as distinguished from the various forms and degrees of idiocy. For it is easy to see that if a function or faculty belonging to any given species is liable for any general cause to be dropped in a certain proportion of the individuals of that species, it must be also liable to become diseased—that is, to break down—in cases where it is not dropped. For if the faculty in question is by no means always developed in the individual—if it quite frequently fails to appear—that must mean that in many other cases in which it does appear it will not be fully and solidly formed. We cannot imagine a jump from the total non-appearance of a given function in certain members of a species to the absolute perfection and solidity of the same function in the rest of the members. We know that species do not grow that way. We know that in a race in which we have some men seven feet high and others only four that we shall find, if we look, men of all statures between these extremes. We know that in all cases extremes presented by the race are bridged (from one to the other) by full sets of intermediary specimens. One man can lift a thousand pounds, another can lift only a hundred; but between these are men the limit of whose strength fills up the whole gap between the hundred and the thousand pounds. One man dies of old age at forty years, another at one hundred and thirty years, and every year and month between forty years and one hundred and thirty years is the limit of some man's possible life. The same law that holds for the limit of faculties holds also for the solidity and permanence of faculties. We know that in some men the intellectual functions are so unstable that as soon as they are established they crumble down—crushed (as it were) by their own weight—like a
badly built house, the walls of which are not strong enough to sustain the roof. Such are extreme cases of so-called developmental insanity—cases in which the mind falls into ruins as soon as it comes into existence or even before it is fully formed; cases of insanity of puberty and adolescence, in which nature is barely able to form or half form a normal mind and totally unable to sustain it, the mind, consequently, running down at once back into chaos. The hopelessness of this class of cases (as regards recovery) is well understood by all alienists, and it is not difficult to see why such insanities should and must be practically incurable, since their very existence denotes the absence of the elements necessary to form and maintain a normal human mind in the subjects in question.
In the realm of insanity, properly so called—that is, excluding the idiocies—these cases occupy the extreme position at one end of the scale, while those persons who only become maniacal or melancholic under the most powerful exciting causes, such as child-birth and old age, occupy the other end. That is, we have a class in whom the mind, without a touch, crumbles into ruin as soon as formed or even before it is fully formed. Then we have another class in which the balance of the mental faculties is only overturned by the rudest shocks, and then only temporarily, since the cases to which I refer recover in a few weeks or months if placed under favorable conditions. But between these extremes the whole wide intermediate space is filled with an infinite variety of phases of insanity, exhibiting every possible condition of mental stability and instability between the two extremes noticed. But throughout the whole range of mental alienation this law holds, namely: that the latest evolved of the mental functions, whether intellectual or moral, suffer first and suffer most, while the earliest evolved of the mental and moral functions suffer (if at all) the latest and the least.
If the mind be likened to a growing tree, then it can be said that the lesser onsets of insanity shrivel its leaves—paralyze, or partially paralyze, their functions for a time, the leaves standing for the later formed and more fragile emotions and concepts, and
especially for the later formed combinations of these; that deeper attacks kill the leaves and damage the finer twigs; that still more profound disturbances kill the finer twigs and injure the larger; and so on, until, in the most profound and deep-rooted insanities, as in the developmental dementias, the tree is left a bare, ghastly trunk, without leaves or twigs and almost without branches.
And in all this process of destruction the older formed faculties, such as perception and memory, desire for food and drink, shrinking from injury, and the more basic sense functions, endure the longest; while, as has been said, the latest evolved functions crumble down first, then the next latest, and so on.
A fact that well illustrates the contention that insanity is essentially the breaking down of mental faculties which are unstable chiefly because they are recent, and that it rests therefore upon an evolution which is modern and still in progress, is the comparative absence of insanity among negroes.
It has been said that the large percentage of insanity in America and Europe depends directly upon the rapid evolution in late millenniums of the mind of the Aryan people. Very few would claim that the negro mind is advancing at anything like the same rate. As a consequence of these different rates of progression we have in the Aryan people of America a much higher percentage of insanity than is found in the negro race.
When the United States census of 1880 was taken it was found that among forty-three millions of white people there were eighty-six thousand insane—exactly one in five hundred—while among six and three-quarter million negroes only a little more than six thousand were insane, which is a proportion of only about one to eleven hundred. Doubtless if we had statistics of other backward and stationary peoples a similar state of matters would be found—all such facts as we have leading to the conclusion that among savages and semi-savages there exists comparatively little insanity.
In conclusion the results arrived at in this chapter may be summed up as follows:
1. The stability of a faculty in the individual depends upon its age in the race. The older the faculty the more stable it is, and the less old the less stable.
2. The race whose evolution is most rapid will be the most subject to breakdown.
3. Those functions in any given race whose evolutions are the most rapid will be the most subject to breakdown.
4. In the more progressive families of the Aryan race the mental faculties have for some millenniums last past developed with great rapidity.
5. In this race the large number of mental breakdowns, commonly called insanity, are due to the rapid and recent evolution of those faculties in that race.