Many other organs in man have been reduced from their former pitch of perfection through culture, and some of them are still in process of dwindling. When I formulated the idea of panmixia and applied it to explain cases which had previously been referred to the inheritance of the results of disuse, I regarded the short-sightedness of civilized Man from this point of view. My opinion aroused lively opposition at the time, especially on the part of oculists, who very emphatically referred the phenomenon to the inheritance of acquired shortsight, and indeed regarded it as a proof of the transmission of functional modifications.
But, apart from the fact that the assumption of this mode of inheritance must now be regarded not only as unproved, but as contradicted by reliable data, panmixia, in conjunction with the ceaseless fluctuations within the germ-plasm—germinal selection—affords a better explanation than the other theory was ever in a position to offer. At that time I pointed out that the survival of the individual among civilized races had not for a very long time depended on the perfection of his eyesight, as it does for instance in the case of a hunting or warlike Indian, or of a beast of prey, or of a herbivore persecuted by the beast of prey. And this is by no means due solely to the invention of spectacles, but in a much greater degree to the fact that every man no longer has to do everything, so that numerous possibilities of gaining a livelihood remain open to the less sharp-sighted; that is, the division of labour in human society has made the survival of the short-sighted quite feasible. As soon as this division of labour reached such a degree that the founding of a family offered no greater difficulty to the short-sighted individual than to one with normal sight, short-sightedness could no longer be eliminated; and partly because of the mingling with normal sight, but partly also because of the never-failing minus-fluctuations of the germ-plasm determinants concerned, a variation in a downward direction was bound to set in, and will continue until a limit is set to it by personal selection. Meantime, we are obviously still in the midst of the process of eye-deterioration; and the resistance to it is somewhat inhibited in its operation, because although individuals with extremely bad sight are for the most part hindered from gaining an independent livelihood and having a family, this is certainly, thanks to our mistaken humanity, not always the case. There are even instances of marriage between two blind persons!
As yet, however, the deterioration of eyes has not advanced very far; not nearly all families are affected by it, and even in Germany, the land of the 'longest school form' and of the greatest number of spectacle-wearers, short-sight is still usually acquired by individuals, although there must frequently be a more or less marked predisposition to it. It is a common objection to this view that in England, France, and Italy the percentage of short-sighted individuals is much lower, and, in point of fact, one sees far fewer people wearing spectacles in those countries. This, however, does not prove that a similar deterioration of eyes has not begun there also, for how could the small inherited beginnings be detected if they were not accentuated by the spoiling of the eyesight in the lifetime of the individual by much reading of bad print, and by writing with bent head, as is still too often the case in many German schools.
That our interpretation, through panmixia on a basis of germinal selection, is the correct one, we infer also from the fact that short-sightedness has been proved to be a frequent character even among our domesticated animals, such as the dog and the horse. These animals receive protection and maintenance from Man, and their survival and reproduction no longer depend on the acuteness of their sight, and thus the eye has fallen from its original perfection, just as in Man, although in this case reading and writing play no part.
A whole series of similar slight deteriorations of individual organs and systems of organs might be enumerated, all of which have appeared in consequence of long and intensive culture in Man. All these must depend upon germinal selection, on a gradually progressive weakening of the determinant-groups concerned, under the conditions of panmixia, that is, in the absence of positive selection.
To these must be added the deterioration of the mammary-glands and breasts, and the inability to suckle the offspring which results chiefly from this. Here we have a variational tendency which could not appear in a people at a lower stage of culture, and it has not become general in the lower classes of society among ourselves.
The muscular weakness of the higher classes is another case in point, and all gymnastics and sports will be of no avail as long as a relative weakness of the muscles is not a hindrance to gaining a livelihood, and having a family. Even universal conscription will do nothing to check this falling off of the bodily strength. Certainly military service strengthens thousands, and hundreds of thousands of individuals, but it does not prevent the weaklings from multiplying, and thus reproducing the race-deterioration. But it would indeed be well if only those who had gone through a term of military service were allowed to beget children.
It is only among the peasantry, inasmuch as they really work and do not merely look on as proprietors of the ground, that such a deterioration of the general muscular strength could not become the permanent variational tendency of the determinants concerned, because among genuine peasants bodily strength is a condition of having and supporting a family—at least on an average.
The diminution in the firmness and thickness of the bones in the higher classes, and many another mark of civilization, must be looked at from the point of view of panmixia and germinal selection; perhaps also the smaller hands and feet which frequently occur along with a more graceful general build in the higher ranks of European peoples. It would certainly not be surprising if in families which usually intermarry, and which in no way depend for their material subsistence on the possession of large and powerful hands and feet or bones generally, a downward variation of the relevant germ-determinants should have developed, but this could never overstep a certain limit, because it would then be prejudicial even in civilized life. That we must be very careful not to regard large hands and feet as the direct result of hard physical toil was brought home to me by an observation of Strasburger's. He was particularly struck by the fact that the peasants of the high Tatra (Carpathians) were distinguished by the smallness of their hands and feet.
But while civilization has excited numerous downward variations in the germ, it has, on the other hand, been the cause of numerous hereditary improvements—variations in an upward direction. This opens up new ground, for hitherto we have been confronted with the alternative of either accepting the inheritance of acquired characters, and on this basis referring the talents and mental endowments of civilized Man to exercise continued throughout many generations, or of admitting an increase of mental powers only in as far as they possess 'selection value,' that is, as they may be decisive in the struggle for existence. To these mental qualities belong cleverness and ingenuity in all directions, courage, endurance, power of combination, inventive power, with its roots in imagination and fertility of ideas, as well as desire for achievement, and industry. Throughout the long history of human civilization these mental qualities must have increased through the struggle for existence, but how have the specific talents such as those exhibited in music, painting, and mathematics come into existence? And how have the moral virtues of civilized Man been evolved, and particularly unselfishness? For it can hardly be maintained of any of these endowments that they possess selection-value for the individual.