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.
It is not my intention to discuss these questions in detail; they are
too many-sided and of too much importance to be treated of merely in
passing; moreover, I gave expression years ago to my views on this
subject by dealing with one example--the musical sense in Man. I do
not believe that the musical sense had its beginnings in Man, or that
it has materially increased since the days of primitive Man, but in
conjunction with the higher psychical life of civilized peoples its
expressions and applications have risen to a higher level. It is, so to
speak, an instrument which has been transmitted to us from our animal
ancestors, and on which we have learnt to play better the more our mind
has developed; it is an unintended 'accessory effect' of the extremely
fine and highly developed organs of hearing with their nerve-centres
which our animal ancestors acquired in the struggle for existence, and
which played a much more important rôle in the preservation of life in
their case than it does in ours. The musical sense may be compared to
the hand, which was developed even among the apes, but which civilized
Man in modern times no longer uses merely to perform its original
function, grasping, but also for many other purposes, such as writing
and playing the piano. And just as the hand did not originate through
the necessities of the piano, neither did the extremely delicate sense
of hearing of the higher animals develop for the sake of music, but
rather that they might recognize their enemies, friends, and prey, in
darkness and mist, in the forest, on the heath, and at great distances.
The case is probably the same with the rest of the special psychical
endowments or talents. I do not of course maintain that they, like
the musical sense, did not at some time play a rôle in the struggle
for existence and survival, and therefore could not increase, but
the increase was certainly not continuous, but much interrupted,
so that it would extend only to small groups of descendants, and
therefore could only contribute very slowly to the elevation of the
psychic capacities of a whole people. But in certain individuals
and families such augmentations would certainly take place through
germinal selection, and it seems to me probable that these would never
be wholly lost again, even if they appeared to be so, but would be
handed on, in id-minorities, through the chain of generations, and
would slightly raise the average of the talent in question, and might
even, under favourable circumstances, combine in the development of
a genius. We know how strongly hereditary such specific talents are;
let us suppose that the determinants of, say, the musical sense have,
by the intra-germinal chances of nutrition, been started on a path of
ascending variation; they will continue in this path until a halt is
called from some quarter or other. This can only happen if, in the
reducing division, or in amphimixis, the highly developed musical
determinants are wholly or partly eliminated, or are reduced to a
minority. As long as this does not happen the ascending variation will
go on, and then we may have the birth of a Mozart or of a Beethoven.
Personal selection will not interfere either in a positive or a
negative sense, since high development of the musical sense has no
effect either in advancing or retarding the struggle for existence;
the increase will therefore go on until the large majority of highly
developed musical determinants, which we must assume in the case of
a musical genius, is reduced, or even transformed into a minority,
through unfavourable reducing divisions of the germ-cells, and by
association with the germ-cells of less musical mates.
The fact that highly developed specific talents have never been known
to be inherited through more than seven generations is quite in keeping
with this view. But even this persistence has been observed only in
the case of musical talent, and the long continuance of the inherited
talent may well be due, as Francis Galton suggests in his famous
statistical investigations into the phenomena of inheritance, to the
fact that musical men do not readily choose wives who are absolutely
lacking in this talent. It would be easy to rear an exceedingly
highly gifted musical group of families within the German nation, if
we could secure that only the highly-gifted musically should unite
in marriage--that is, if personal selection could play its part. In
another more general domain of mental endowment a case of this kind
has been recorded, for Galton tells us of three highly gifted English
families which intermarried for ten generations, and in that time
scarcely produced a descendant who did not deserve to be called a
distinguished man in some direction or other.
Of course, such continued persistence, through a long series of
generations, of a high general mental level is more possible than the
transmission and increase of a specific talent, for in the former case
it is a question of a mixture of different high mental endowments,
of which not all need be developed in every individual, and yet the
individual need not fall to mediocrity if he possesses a combination
of other qualities. But in musical talent, on the other hand, the
falling from the height once attained takes place as soon as this one
character is no longer represented in a sufficiently strong majority
of determinants. Of course it would be a mistake to believe that the
talent of a Sebastian Bach or a Beethoven depended solely on the
highly developed musical sense; in them, as in all great artists, many
highly developed mental qualities must have combined with the musical
sense; a simpleton could never have written the Mass in B minor or the
Passion of St. Matthew even if he had possessed the musical genius of
Sebastian Bach. In this fact lies a further reason why genius is seldom
found at the same pitch in two successive generations; the combination
of mental characters always varies from father to son, and slight
displacements may give rise to very great differences in relation to
the manifestations of the specific talent. Under certain circumstances,
the weak development of a single trait of character, as, for instance,
power of action, or the excessive development of another, such as
indecision or desultoriness, may so nullify the existing favourable
combinations of mental characters, such as, let us say, musical sense,
inventive talent, depth of feeling, &c., that they bear no fruit
worth mentioning. And since as we have already seen, the different
mental qualities of the parents are to a certain extent separately
transmitted, that is, since they may appear in the children in the most
diverse combinations, we should rather be surprised that pronounced
talent in a specific direction can persist in a family for two and a
half centuries than that it should do so very rarely. For reducing
division is always combining the existing mental qualities anew, and
amphimixis is adding fresh ones to them.
Thus germinal selection, that is, the free, spontaneous, but definitely
directed variation of individual groups of determinants, is at the
root of those striking individual peculiarities which we call specific
talents; but it can attain to the highest level only rarely and in
isolated cases, because these talents are not favoured by personal
selection, and therefore the excessively highly developed determinants
upon which they depend may be dispersed in the course of generations;
they may sink to smaller majorities, or even to minorities, in which
case they will no longer manifest themselves in visible mental
qualities.
We deduced the process of germinal selection on the basis of the
assumption that the nutrition of all the parts and particles of
the body, therefore also of the determinants and biophors of the
germ-plasm, is subject to fluctuations. We regarded the resulting
variations of these last and smallest units of the germ-plasm as the
ultimate source of all hereditary variation, and therefore the basis of
all the transformations which the organic world has undergone in the
course of ages and is undergoing still.
We have still to inquire whether we can give any more precise account
of the nature of these units of the germ-plasm. If I mistake not,
we may say at least so much, that all variations are, in ultimate
instance, quantitative, and that they depend on the increase or
decrease of the vital particles, or their constituents, the molecules.
For this reason I have hitherto always spoken of only two directions
of variation--a plus or a minus direction from the average. What
appears to us a qualitative variation is, in reality, nothing more
than a greater or a less, a different mingling of the constituents
which make up a higher unit, an unequal increase or decrease of these
constituents, the lower units. We speak of the simple growth of a cell
when its mass increases without any alteration in its composition,
that is, when the proportion of the component parts and chemical
combinations remains unchanged; but the cell changes its _constitution_
when this proportion is disturbed, when, for instance, the red
pigment-granules which were formerly present but scarcely visible
increase so that the cell looks red. If there had previously been no
red granules present, they might have arisen through the breaking up
of certain other particles--of protoplasm, for instance, in the course
of metabolism, so that, among other substances, red granules of uric
acid or some other red stuff were produced. In this case also the
qualitative change would depend on an increase or decrease of certain
simpler molecules and atoms constituting the protoplasm-molecule. Thus,
in ultimate instance, all variations depend upon quantitative changes
of the constituents of which the varying part is composed.
It might be objected to this argument that chemistry has made us
acquainted with isomeric combinations whose qualitative differences
do not depend upon a different _number_ of the molecules composing
them, but upon their different arrangement; it might be supposed that
something similar would occur also in morphological relations. And, in
point of fact, this seems to be the case. We may, for instance, imagine
one hundred hairs as being at one time equally distributed on the back
of a beetle, and at another standing close together and forming a kind
of brush, but although this brush would be a new character of the
beetle, yet its development would depend upon quantitative differences,
namely, on the fact that the same skin-area, which in the first case
bore perhaps only one hair, had in the second case a hundred. The
quantity of hair cells has notably increased upon this small area. In
the same way the characteristic striping of the zebra depends not on
a qualitative change in the skin as a whole, but upon an increased
deposit of black pigment in particular cells of the skin, therefore
on a quantitative change. In relation to the whole animal it is a
qualitative variation, as contrasted, for instance, with the horse, but
in respect of the constituent parts which give rise to the qualitative
variation it is purely quantitative. The character of the whole edifice
is changed when the proportion of the stones of which it consists are
altered.
Thus the determinants of the germ may not only become larger or smaller
as a whole, but some kinds of the biophors of which they are made up
may increase more than others, under definite altered conditions, and
in that case the determinants themselves will vary qualitatively, so
that, from the changing numerical proportions of the different kinds of
biophors, a variation of the characters of the determinants can arise,
and consequently also qualitative variations of the organs controlled
by the determinants--the determinates. But, since nothing living can
be thought of as invariable, the biophors themselves may, on account
of nutritive fluctuations, grow unequally, and thereby vary in their
qualities. To follow this out in greater detail and attempt to guess
at the play of forces within the minutest life-complexes would at
present only be giving the rein to imagination, but in principle no
objection can be made to the assumption that every element of life down
to the very lowest and smallest can, by reason of inequalities in its
nutrition, be not only started on an ascending or descending movement
of uniform growth, but can also be caused to vary _qualitatively_,
that is, in its characters, because its component parts change their
proportions.
Of course we know nothing definite or precise with regard to the units
of the germ-plasm, and we cannot tell what is necessary in order
that a determinant shall determine a part of the developing body in
this way or in that; thus we have no definite idea of the relations
subsisting between the variations of the determinants and those of
their determinates, but we know at least so much, that hereditary
variation of a part is only possible when a corresponding particle
in the germ-plasm varies; and we may at least assume that these
correspond to each other so far, that a greater development of the one
implies a greater development of the other, and that a reversal of
these relations is impossible. If the determinant _X_ disappears from
the germ-plasm the determinate _X´_ disappears from the soma. It is
therefore justifiable to infer from the degree of development of an
organ the strength of its determinant, and to assume that plus- and
minus-variations in both are correspondingly large.
But in addition to the fluctuations in the equilibrium of the
germ-plasm which lie at the root of all hereditary variation, we have
to take into account something which we have already touched upon
briefly--the correlation of the determinants, the influencing of one
determinant by those round about it. I have spoken for the sake of
brevity of 'the determinant' of a part, although all the large and
more important parts must certainly be thought of as represented by
several or many, if not, indeed, by whole groups of determinants.
Although it is quite out of our power to follow the complex processes
of the mutual influences of the determinants upon each other, we can
say this at least, _that these influences must exist_, and we have
here a faint indication of what must occur in the case of spontaneous
variations within the germ-plasm. We must, in the first place, think
of the individual determinants as arranged in groups, so that, for
instance, the determinants of the right and left half of the body lie
together, and therefore are frequently affected together by influences
which cause variation, so that both vary in the same direction at
the same time. In point of fact, analogous deformities, such as
polydactylism of both right and left hands, and even of hands and feet
at once, do actually occur. That the right and left hands, the fore-
and hind-limbs, are represented in the germ by particular determinants,
may be inferred from their frequently different phyletic evolution into
different forms of hand and foot, e.g. into flipper and rudimentary
hind-leg in the whale, as well as from the cases of particulate
inheritance, which are rare, but which undoubtedly do occur, such
as when, in Man, there is a maternal blue eye on one side of the
head and a paternal brown eye on the other. But almost more striking
than the differences between these homologous or homotypic parts
are their points of resemblance, and these may probably be in part
referred to their disposition side by side and common history in the
germ-substance, although a far larger proportion of them are probably
due to their adaptation to similar functions, and are therefore to be
regarded as a phenomenon of convergence within the same organism.