THE GRADES OF THE FACTORS OF EVOLUTION AND THE ORDER OF THEIR
APPEARANCE.
We have given in the previous chapter six factors of evolution--viz.:
1. _Pressure of the environment._ 2. _Use and disuse of parts._
3. _Natural selection._ 4. _Sexual selection._ 5. _Physiological
selection._ 6. _Reason._ Let us now compare these as to their grade in
the scale of energy and as to the order of their introduction.
The first two or the Lamarckian factors are the lowest in position,
the most fundamental and universal, and therefore the first in
the order of appearance. They precede all other factors, and were
doubtless for a long time _the only ones in operation_. For, observe,
all the selective factors--i. e., those of Darwin and Romanes--are
conditioned on reproduction; for the changes produced by these are
not in the individual during life, but in the offspring at birth.
And not only so, but the operations of these factors are further
conditioned on _sexual modes_ of reproduction; for all the non-sexual
modes of reproduction--as, for example, by fissure and by budding--are
but slight modifications of growth, and the resulting multitude of
organisms may be regarded as in some sense _only an extension of the
first individual_. Of course, therefore, the identical characters of
the first individual are continued indefinitely, except in so far
as they are modified in successive generations by the effect of the
environment and by use and disuse--i. e., by the Lamarckian factors.
In sexual generation, on the contrary, the characters of two diverse
individuals are funded in a common offspring; and the same continuing
through successive generations, it is evident that the inheritance in
each individual offspring is infinitely multiple. Now, the _tendency
to variation_ in offspring _is in proportion to the multiplicity of
the inheritance_: for among the infinite number of slightly differing
characters, as it were, offered for inheritance in each generation,
some individuals will inherit more of one and some more of another
character. In a word, sexual reproduction by multiple inheritance
_tends to variation of offspring, and thus furnishes material for
natural selection_.[16]
Thus, then, I repeat, all the selective factors are absolutely
dependent on sexual modes of reproduction. But there was a time when
this mode of reproduction did not yet exist.[17] The sexual modes
developed out of non-sexual modes. If these non-sexual preceded sexual
modes of reproduction, it is evident that at first only Lamarckian
factors could operate. Evolution was then carried forward wholly
by changes in the individual produced by environment and by use and
disuse (acquired characters), inherited and increased by integration
through successive generations indefinitely. It is probable, therefore,
that the _rate_ of evolution was at first comparatively slow; unless,
indeed, as seems probable, the _earliest_ forms _were then_ and the
_lowest_ forms _are now_ more plastic under the influence of physical
conditions than are the present higher forms. Doubtless, now, in the
higher animals and plants, the Darwinian factors are by far the most
potent; for, among plants, where we can use these factors separately,
if we wish to _make_ varieties, we propagate by seeds (sexual
reproduction); but, if we wish to preserve varieties, we propagate by
buds and cuttings (non-sexual reproduction).
I have taken the two Lamarckian factors together, and showed that they
preceded the Darwinian. But even in the two Lamarckian factors there is
a difference in grade. Undoubtedly the lowest, the most fundamental,
and therefore the first introduced, was _pressure of the physical
environment_. For use and disuse of organs implies some degree of
volition and voluntary motion, and therefore already some advance in
the scale of evolution.
With the introduction of sex another entirely different and higher
factor was introduced, viz., _natural selection_, or selection of
the fittest individuals of a varying progeny. We have already seen
how sexual generation produces variation of offspring, and how this
furnishes materials for natural selection. As soon, therefore, as this
form of generation was evolved, this higher factor came into operation
and immediately assumed control; while the previous factors became
subordinate, though still underlying, conditioning, and modifying the
activity of the higher. The result was an immediate increase in the
rate of evolution. It is very worthy of note that it is in the higher
animals, such as birds and mammals, in which we have only the highest
forms of sexual reproduction, where the diversity of characters of
the two sexes funded in the offspring is the greatest, and where,
therefore, the variation in offspring is also greatest and natural
selection most active; it is precisely among these that the Lamarckian
factors are most feeble, because, during the most plastic period of
life, the offspring is removed from the influence of the physical
environment, and from use and disuse by its inclosure within the womb,
or within a large egg surrounded with abundant nutriment. Development
is already well advanced before Lamarckian factors can operate at all.
Next, I suppose, physiological selection, or Romanes’s factor, came
into operation. After the introduction of sex, it became necessary that
the individuals of some varieties should be isolated in some way, so
as to prevent the swamping of varietal characters, as fast as formed,
in a common stock, by _cross-breeding_. In very low forms, with slow
locomotion, such isolation might easily take place accidentally. Even
in higher forms, changes in physical geography or accidental dispersion
by winds and currents would often produce geographical isolation,
and thus, by preventing crossing with the parent stock, secure the
formation of new species from such isolated varieties. But, in order
to insure in all cases the preservation of commencing species, _sexual
isolation_, or partial or complete infertility of some varieties
with other varieties and with the parent stock, was introduced, as
I suppose, later. The process by which this takes place has already
been explained. According to Romanes, natural selection alone, with
cross-breeding, tends to _monotypal_ evolution; isolation of some kind
is necessary for polytypal evolution. The tree of evolution, under
the influence of natural selection alone, grows, palm-like, from its
_terminal bud_; isolation of varieties was necessary for the starting
of _lateral buds_, and thus for the profuse ramification which is its
most conspicuous character.
Next, I suppose, was introduced _sexual selection_, or contest among
the males, by battle or by display, for possession of the females,
and the success of the strongest or the most attractive; and the
perpetuation and increase of these superior qualities of strength
and beauty in the next generation. This, I suppose, was later,
because connected with a higher development of the psychical nature.
This is especially true where splendor of color or beauty of song
determines the selection. As might be supposed, therefore, this factor
is operative only among the highest animals, especially birds and
mammals.[18]
Next and last, and only with the appearance of _Man_, another entirely
different and far higher factor was introduced, viz., _conscious,
voluntary co-operation_ in the work of his own evolution--a conscious,
voluntary striving to _attain an ideal_. We have called this a factor,
but it is much more than a mere factor, co-ordinate with other factors.
It is, rather, a different kind of evolution. It is evolution on
a higher plane and by another nature. As _physical_ Nature works
_unconsciously_, using certain factors, so _spiritual_ nature works
_consciously_, co-operating and using the same factors. At first this
factor, if we still call it so, was extremely feeble. In the early
stages of his progress, man, like other animals, was largely urged
on by forces of organic evolution, unknowing and uncaring whither
he tended. But more and more, as civilization advances, this higher
and distinctively human factor becomes more and more dominant, until
now, in civilized communities, it takes control of evolution. Reason,
instead of Nature, now assumes control, though still using the methods
and factors of Nature. This _free_, self-determined evolution of the
race, in order to distinguish it from the _necessary_ evolution of the
organic kingdom, we call progress.
Now, in this whole process we observe two striking stages. The one is
the introduction of sex, the other is the introduction of reason.[19]
They may be compared to two equally striking stages in the development
of the _individual_. As the _ontogenic_ evolution receives fresh
impulse at the moment of fertilization, so the evolution of the organic
kingdom receives fresh impulse at the moment of introduction of sex. As
in ontogenic evolution the individual at birth enters upon a new and
higher plane, in which it co-operates in its own _physical_ growth,
so the organic kingdom, with the introduction of man, enters upon a
new and higher plane, in which man co-operates in the physical and
_spiritual_ growth of the race. With sex three new and higher factors
were introduced, and these immediately assumed control and quickened
the rate of evolution. With reason another and infinitely higher factor
is introduced, which, in its turn, assumes control, and not only again
quickens the rate, but elevates the whole plane of evolution. Moreover,
this voluntary, rational factor not only takes control itself, but
transforms all other factors and uses them in a new way and for its own
higher purposes.
This last is by far the greatest change which has ever occurred in
the history of evolution. In organic evolution Nature operates by
necessary law without the conscious voluntary co-operation of the thing
evolving. In human progress man voluntarily co-operates with Nature in
the work of evolution, and even assumes to take the process mainly into
his own hands. Organic evolution is by _necessary_ law, human progress
by _free_ or at least by freer law. Organic evolution is by a _pushing_
upward and onward from _below_ and _behind_, human progress by a
_drawing_ upward and onward from above and in front by the attractive
force of ideals. In a word, organic evolution is by the law of _force_,
human evolution by the law of _love_.
It may be well to stop a moment and show briefly some of the
differences between organic and human evolution--differences which are,
of course, wholly the result of the introduction of this new factor:
1. In organic evolution “_the fittest_” are those most in harmony
with the physical environment, and therefore they survive. In human
evolution _the fittest_ are those most in harmony with _the ideal_, and
often, especially in the early stages, when the race is still largely
under the dominion of organic factors, they do not survive, because
not in harmony with the social environment. But, although the fittest
individuals may indeed perish, the _ideal_ survives in the race and
will eventually triumph.
2. In organic evolution the weak, the sick, the helpless, the unfit
in any way perish and _ought to perish_, because this is the most
efficient way of strengthening the _blood_ or _physical nature_ of the
species, and thus of carrying forward evolution. In human evolution
the weak, the helpless, the sick, the old, the unfit in any way are
sustained and _ought to be sustained_, because sympathy, love, pity,
strengthen the _spirit_ or _moral nature_ of the race. But let us
remember that in this material world of ours and during this earthly
life the spirit or moral nature is conditioned on the physical nature;
and, therefore, in all our attempts to help the weak we must be careful
to avoid poisoning the blood and weakening the physical vigor of the
race by inheritance. This gravest of social problems, viz., How shall
we obey the higher law of love and mutual help without weakening the
_blood_ of the race by inheritance and the spirit of the race by
removing the necessity of self-help?--this problem, I believe, can and
will be solved by a _rational education_, physical, mental, and moral.
I only allude to this. It is too wide a field to follow up here.
3. In organic evolution the bodily _form_ and _structure_ must
continually change in order to keep in harmony with the ever-changing
environment. In other words, organic evolution is by continual change
of species, genera, families, etc. There must be continual evolution
of new forms by modification. In human evolution, on the contrary, and
more and more as civilization advances, man modifies the environment so
as to bring it into harmony with himself and his wants, and therefore
there is no necessity of change of bodily form and structure or
making of new species of man. Human evolution is not by modification
of _form_--new species; but by modification of spirit--new planes of
activity, _higher character_. And the spirit is modified and character
elevated, not by _pressure_ of an _external physical environment_, but
by the _attractive_ force of an _internal spiritual ideal_.
4. The way of evolution toward the highest--i. e., from protozoan
to man and from lowest man to the ideal, the divine man--is a very
_straight and narrow way_, and few there be that find it. In the
case of organic evolution it is so straight and so narrow that any
divergence therefrom is fatal to upward movement toward man. Once get
off the track, and it is _impossible_ to get on again. No living form
of animal is on its way _manward_, or can by any possibility develop
into man. They are all gone out of the way. There is none going right;
no, not one. The organic kingdom developing through all geological
times may be compared to a tree whose trunk is deeply buried in the
lowest strata, whose great limbs were separated in early geological
times, whose secondary branches diverged in middle geological times,
and whose extreme twiglets, and also its graceful foliage, its
beautiful flowers, and luscious fruits, are the fauna and flora of
the present day. But this tree of evolution is an _excurrent stem_,
continuous through the clustering branches to the terminal shoot--man.
Once leave the stem as a branch, and it is easy to continue growing in
the direction chosen, but impossible to get back on the straight upward
way to the highest. In human evolution, whether individual or racial,
the same law holds, but with a difference. If individual or race gets
off the straight, narrow way toward the highest--the divine ideal--it
is hard, very hard to get back on the track. Hard, I say, but _not_
impossible, because man’s conscious voluntary effort is the chief
factor in his own evolution. By virtue of self-activity, through the
use of reason and co-operation in the work of evolution, man alone of
all created things is able to rectify an error of direction and return
again to the deserted way.
5. In organic evolution, when a higher factor appears, it immediately
assumes control, and previous lower factors sink into a subordinate
position, though still underlying and conditioning the higher. But in
human evolution, the higher rational factor, when it comes in with
man, not only assumes control, but transforms all other factors and
uses them in a new way and for its own higher purposes. In fact, as
already said, it is much more than a mere factor. It determines a
new kind of evolution--evolution on a new and higher plane though,
indeed, underlaid and conditioned by the laws of organic evolution. As
_external physical_ Nature uses many factors to carry forward organic
evolution, so the _internal spiritual_ nature, characteristic of man
alone, uses these same factors in a new way to carry forward human
evolution or progress. Thus, for example, one organic factor--the
environment--is modified or even totally changed so as to effect
suitably the human organism. This is _hygiene_. Again, use and
disuse--another factor--is similarly transformed. The various organs of
the body and faculties of the mind are deliberately used in such wise
and degree (determined by reason) as to produce the highest efficiency
of each part and the greatest strength and beauty of the whole. This
is _education_--physical, mental, moral. So also the selective factors
are similarly transformed, and _natural_ selection becomes _rational_
selection. We all know how this method is applied to domestic animals
and cultivated plants in the formation of useful or beautiful
varieties. Why should it not be applied also to the improvement of our
race in the selection of our mates in marriage, or in the selection of
our teachers, our law-makers, our rulers? Alas! how little even yet
does reason control our selection in these matters! How largely are we
yet under the law of organic evolution!
_Application of these principles to some questions of the day_:
I. Evolution, as a law of derivation of organic forms from previous
forms by descent with modifications, as already shown, is as certain
as the law of gravitation. This question has passed beyond the realm
of doubtful discussion; but the causes, the factors, the details of
the process of evolution are still under discussion. Both Darwin and
Spencer, the two great founders of the theory of evolution in its
modern form, acknowledge and insist on at least four factors, viz., the
two Lamarckian and the two distinctively Darwinian. The only difference
between them is in the relative importance of the two sets: Spencer
regarding the former and Darwin the latter as the more potent. But in
these latest times there has arisen a class of biologists, including
some of highest rank, such as Wallace, Weismann, and Lankester, who
out-Darwin Darwin himself in their exaltation of the most distinctive
Darwinian factor, viz., natural selection. They try to show that
natural selection is the sole and sufficient cause of evolution; that
changes in the individual, whether as the effect of the environment or
by use and disuse of organs, are not inherited at all; that Lamarck was
wholly wrong; that Darwin (in connection with Wallace) was the sole
founder of the true theory of evolution; and, finally, that Darwin
himself was wrong only in making any terms whatever with Lamarck. This
view has been called _Neo-Darwinism_.
Perhaps the reasons for this view have been most strongly put by
Weismann, and are based partly on experiments, but mainly on his
ingenious and now celebrated theory of the immortality of germ-plasm.
The animal body consists of two kinds of cells wholly different in
function--somatic cells and germ-cells, including in this last the
sexual elements both male and female. Somatic cells are specially
modified for the various functions of the body; germ-cells are
wholly unmodified. The somatic cells are for the conservation of
the _individual_ life, the germ-cells for the conservation of the
_species_. In the development of the egg the germ-cell multiplies
itself into a cell-aggregate, and then most of the resulting multitude
of cells are modified in various ways to form the tissues and organs
of the body--somatic cells; but a few are reserved and put aside
in an unmodified form in the sexual organs as germ-cells, to again
produce ova which again divide into somatic and germ-cells, and so on
indefinitely. Now, according to Weismann, inheritance is only through
_germ-cells_, while the environment affects only the _somatic cells_.
Therefore changes produced by the environment can not be inherited.
Sexual modes of generation were introduced for the purpose of producing
variability in progeny, and thus furnishing material for natural
selection, as this was the only means of evolutionary advance. Weismann
made many experiments on animals, especially by mutilation, to show
that somatic changes are not inherited.
A full discussion of this question would be unsuitable in a work like
this. We will therefore content ourselves with making three brief
remarks:
_a._ If the views presented in the early part of this chapter are true,
then the Lamarckian factors must be true factors, _because there was
a time when there were no others_. They were therefore necessary, at
least to start the process, even if no longer necessary at present.
_b._ But if these factors were ever operative, _they must be so
still_, though possibly in a subordinate degree. A lower factor is
not abolished, but only becomes subordinate to a higher when the
latter is introduced. Thus it may well be that Lamarckian factors are
comparatively feeble at the present time and among living species,
especially of the higher animals, and yet not absent altogether. In the
earliest stages of evolution there was a _complete identification of
germ-cells and somatic cells_--of the individual with the species. In
such cases, of course, any effect of the environment must be inherited
and increased from generation to generation. But the differentiation
of the germ and somatic cells was not all at once, nor is their
sympathetic relation completely severed. It was a _gradual process_,
and therefore the effect of the environment _on the germ-cells through
the somatic cells_ continued, though in decreasing degree, and still
continues. The differentiation in the higher animals is now so complete
that germ-cells are probably not at all affected by changes in somatic
cells, unless these changes are _long continued in the same direction,
and are not antagonized by natural selection_.
_c._ It is a general principle of evolution that the _law of the whole
is repeated with modifications in the part_. This is a necessary
consequence of the unity of Nature. We ought to expect, therefore,
and do find, that the order of the use of the factors of evolution is
the same in the evolution of the _organic kingdom_, in the evolution
of _each species_, and in the evolution of _each individual_. In all
these the physical factors are at first powerfully operative; these
become subordinate to organic factors, and these, in their turn, to
psychical and rational factors. Therefore, as the individual in its
early stages--i. e., in embryo and infancy--is peculiarly plastic
under the influence of the physical environment, and afterward becomes
more and more independent of these; so a species when first formed is
more plastic under the influences of Lamarckian factors, and afterward
becomes more rigid to the same. And so also the organic kingdom was
at first more plastic under Lamarckian factors, and has become less
so in the present species, especially in the higher animals. The
principal reason of this, as we have already seen, is the increasing
differentiation of germ and somatic cells, and the removal of the
former to the interior, where they are more and more protected from
external influence.
II. Some evolutionists--the materialistic--insist on making human
evolution identical in all respects with organic evolution. This, we
have shown, is not true. The very least that can be said is that a
new and far more potent factor is introduced with man, which modifies
greatly the process. But we may claim much more, viz., that evolution
is here on a different and higher plane. The factors of organic
evolution are, indeed, still present, and condition the whole process;
but they are not left to be used by Nature alone. On the contrary, they
are used in a new way and for higher purposes--by reason.
But by a revulsion from the materialistic extreme some have gone to the
opposite extreme. They would place human progress and organic evolution
in violent antagonism, as if subject to entirely different and even
opposite laws; but we have also shown that, although the distinctive
human factor is indeed dominant, yet it is underlaid and conditioned by
all the lower factors; that these lower factors are still necessary as
the agents used by reason.
III. We have already given the views of Weismann and Wallace, and some
reasons for not accepting them; but there is one important aspect
not yet touched. There are some logical consequences of these views
when applied to human evolution which seem to us nothing less than a
_reductio ad absurdum_. This brings into view still another contrast
between organic evolution and human progress.
In organic evolution, when the struggle for life is fierce and pitiless
as it is now among the higher animals, natural selection is undoubtedly
by far the most potent factor. It is at least conceivable (though
not probable) that at the present time organic evolution might be
carried on mainly or even wholly by this factor alone; but in human
evolution, especially in civilized communities, this is impossible.
If Weismann and Wallace be right, then alas for all our hopes of race
improvement--physical, mental, and moral!--for natural selection will
never be applied by man to himself as it is by Nature to organisms. His
spiritual nature forbids. Reason may freely use the Lamarckian factors
of environment and of use and disuse, but is debarred the unscrupulous
use of natural selection _as its only method_. As this is an important
point, we must explain.
All enlightened schemes of physical culture and hygiene, although
directed primarily to secure the strength, the health, and the
happiness of the _present generation_, yet are sustained and
ennobled by the conviction that the improvement of the individuals
of each generation enters by inheritance into the gradual physical
improvement of the race. All our schemes of education, intellectual
and moral, though certainly intended mainly for the improvement
of the individual, are glorified by the hope that the race also is
thereby gradually elevated. It is true that these hopes are usually
extravagant; it is true that the _whole_ improvement of one generation
is not carried over by inheritance into the next; it is true,
therefore, that we can not by education raise a lower race up to the
plane of a higher in a few generations or even in a few centuries: but
there must be at least a small residuum, be it ever so small, carried
forward from each generation to the next, which, accumulating from age
to age, determines the slow evolution of the race. Such are the hopes
on which all noble efforts for race-improvement are founded. Are all
these hopes baseless? They are so if Weismann and Wallace are right. If
it be true that reason must direct the course of human progress, and
if it be true also that selection of the fittest in the organic sense
is the only method which can be used by reason, then the dreadful law
of pitiless destruction of the weak, the helpless, the sick, the old,
must with Spartan firmness be voluntarily and deliberately carried out.
Against such a course we instinctively revolt with horror, because
contrary to the law of our spiritual nature.
But the use by reason of the Lamarckian factors is not attended with
any such revolting consequences. All our hopes of race-improvement,
therefore, are strictly conditioned on the efficacy of these
factors--i. e., on the fact that useful changes, determined by
education in each generation, are to some extent inherited and
accumulated in the race.