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Vernon L. (Vernon Lyman) Kellogg.

Darwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming online

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Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 14 of 38)
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variations."

Tayler, 8 a Darwinian defender, has discussed this objec-
tion as follows : ''This objection appears to me to be one of
the most weighty of all the objections which have been raised
to the selectional hypothesis, and it is further an extremely
difficult objection to satisfactorily reply to; first, because it is
almost impossible to say in what form of organism the earli-
est variations appeared, and without this no judgment on the
value of any small variation can be of use ; secondly, it is
equally essential to know the kind of environment which
such an organism was living in; and lastly, if we were
fully acquainted with the character of the organism and its
environment it would still be difficult to form any adequate
opinion on the value of such a variation, owing to the fact
that this apparently simple organism would differ so widely
from our own functional activity and life that any conclu-
sions formed on comparative methods of testing its powers,



142 DARWINISM TO-DAY.

etc., would be extremely likely to be fallacious. If, however,
we keep in mind the facts that ( I ) the whole and not merely
a part of the organism is selected, and that, therefore,
each variation does not require to be of the same value as if
selection depended on it alone; (2) specialisations are
largely quantitative, between man at one extreme of de-
velopment and a simple unicellular organism at the other,
the difference, though very great, is mainly due to the fact
that man is a huge multicellular colony ; this difficulty will be
much simplified. To estimate the quantitative difference it is
necessary to endeavour to determine the specialisation of an
individual cell in one of those collective specialisations or
organs : the difference between a cell in, for instance, the
cerebral cortex of man and the character of an amoeba is no
doubt great, but the amceba reacts to stimuli, though in a
less specialised form, just as the cortex cell does ; in the same
way the reaction to light in the mammalian eye is not a new
development it has its beginnings in the preference for
light or darkness shown by many unicellular organisms.
These two points, that selection is organismal and that
specialisations are as. or more, largely quantitative than
qualitative, weaken if they do not abolish all those diffi-
culties to natural selection that are founded on this objec-
tion, and it is further necessary to recollect that no specialisa-
tion has yet been found which has not a primitive counter-
part in the earliest known forms of life." * ^

With regard to the objection that because natural selec-
tion working with fluctuating Darwinian variations is

Answer to the working only with linear or quantitative varia-
objection'that * tions and therefore cannot produce many-
"tSSSTnSir * branched descen t (which is certainly the kind
LnTedTscent of descent that exists) but only straight-line or
Verier* 1 " 111 * 7 mon - t yP ic descent, it is obvious that the Dar-
winian answer to this is partly that of the
answer to the objection discussed in the last paragraph. In



DARWINISM DEFENDED. 143

addition it is partly that of the answer to the objection to
be mentioned in the next sentence. This related objection
is that while natural selection may produce continuous
gradatory adaptive change or evolution it cannot produce
discontinuity in the series, i. e., cannot produce separated
distinct species. This objection receives an answer which
is* of the nature of an admission that natural selection wholly
unaided really cannot differentiate species. It must call to
its aid some isolation or segregation factor, and as isolation
is certainly most commonly effected through migration and
geographic means, it is usually this factor of geographic
isolation that natural selection must be accompanied by to
form new species. As Plate says: "Any particular phase
of the struggle for existence extinguishes all those indi-
viduals which do not possess certain absolutely necessary
characteristics. By this means there is produced a common
type. And only when some means of isolation is added can
the splitting of the species into two or more forms result.
Natural selection can only transform a species gradually
and develop it in a continuous forthright line ; alone it cannot
produce a divergent, tree-like evolution. This results from
geographic, biologic, or sexual isolation, which is in most
cases a form of the extensive manner of working of the
struggle for existence. But selection can aid in the differ-
entiation of a species into two or more forms, as the following
examples show. When all average or median-sized in-
dividuals of a species are killed out there remain only the
smallest and the largest, by which we may assume that the
first are saved because they can most readily conceal them-
selves, while the latter find in their great size a sufficient
protection. On the ground of this difference in size perhaps
both forms will be inclined to keep apart from each other
and if to this is added a somewhat differing habit of life,
two races can arise which in course of time will become
distinct species. From a butterfly kind of very variable



144 DARWINISM TO-DAY.

colour-tone all brown individuals might disappear for some
special reason while both the lighter and darker individuals
might persist. Now if in consequence of this contrast a
racial feeling should develop between the light individuals
on the one hand and the dark ones on the other, the differ-
entiation into two species is already begun. If a snail species
living in fresh water is so harassed that it can only maintain
itself when its individuals move either into the region be-
tween tide-lines or into the deeper water, this would lead to
morphological differentiation, as we can indeed actually note
in the case of the chitons."

The objection that the existence of coadaptive and highly
complex adaptations, especially those which seem as if they
could be of no possible advantage to their pos-
oVcXn'coii* 11 * sessors exce P t m thd f present fully developed
cerning complex or specialised state, is one which unfortunately
adaptations' 6 cannot be definitely refuted or proved by ever
so much ingenious explaining or discussion in
the face of the lack of what we certainly do not now
possess, namely, direct observational or experimental evi-
dence. For such specialisations as elaborate mimickry, or
the electric organ of the torpedo, etc., which are of appa-
rent advantage only in perfected state, the selectionist is
forced to admit that the objector has apparently a good case,
"but for the gradual specialisation of many highly complex
structures and specialisations through the long-continued
selection of slight advantageous variations, Darwin and his
followers have offered ingenious and plausible explanations.
For the case of so complex and coadaptive a specialisation as
the eye and its function in the vertebrates or in the insects
and crustaceans, the possible evolution, by slight additions
and modifications, from simple pigment fleck to the present
marvellous visual organ, a logically irrefutable Darwinian
argument can be made out on the basis of the real and
constant utility and advantage of even very slight steps



DARWINISM DEFENDED. 145

forward. And so with many other complex specialisations,
although in almost all these cases it is necessary, as Darwin
says, to let the reason conquer the imagination. That is, the*
reasoned explanation explains, although one recoils con-
stantly before the almost inconceivable actuality of the
phenomenon.

Plate has recognised this objection as one of the really
weighty ones and has given much attention to its considera-
tion. His conclusion is that it is necessary to rely to a
greater or less extent on the Lamarckian factor of the
inheritance of somatogenic characters acquired in the life-
time of the individual through the effects of use, or disuse,
or other functional stimuli. This is, of course, direct aban-
donment of the position maintained by such strict selection-
ists as Weismann and Wallace, although Weismann himself,
in order to answer the objection without having recourse
to reliance on Lamarckian factors, introduces his new
theory or hypothesis of germinal selection to aid natural
selection in the difficulty presented by the objection. Lloyd
Morgan's " answer to this objection consists chiefly of the
formulation of the theory of orthoplasy (explained in chapter
viii of this book). It is, briefly, that every organism, from
its somatic and germinal aspects, exhibits two tendencies
of variability. The somatic variability is determined largely
or at least modified largely by environmental influences;
therefore those organisms whose somatic tendency is pre-
dominantly plastic will survive under altered conditions of
environment, where those organisms of a less easily mod-
ifiable tendency will be eliminated. Now if somatic changes
rarely or never become germinal, i.e., are inherited, the mod-
ifications of the parental organisms cannot be transmitted
to their offspring, but those offspring that happen to be
endowed with germinal variations in the same direction
as the acquired but not transmitted modifications would
start their life with a predisposition favourable to their



146 DARWINISM TO-DAY.

environment and therefore favourable to more complete
modification of the somatic side of the organism ; this tend-
ency being accumulative under constant conditions, coinci-
dent variability would arise by the process of selective
elimination and preservation, without the need of the
assumption of use-inheritance, which assumption facts
appear to negative.

Against the criticism that natural selection cannot explain
over-developments of specialisation, that is, the carrying
unnecessarily far of advantageous structural
and functional development, as illustrated by
ceming over- the great antlers of stags and moose, the micro-
tlon ' scopic fidelity of simulation and mimicry, and
the nearly identical equivalence of the right and left halves
of bilaterally symmetrical animals, the selectionist has little
to offer except the always pertinent questions : Are we sure
that the case in point is one of over-development, of unnec-
essary specialisation? And although the palaeo-zoologists
may be pretty emphatic ' in their declarations that the ex-
tinction of the Irish stag and of the unwieldy cretaceous
reptiles was directly due to over-specialisation, they cannot
prove it. And there you are, says the Darwinist.

The difficulty that natural selection has with structural
degeneration is admittedly a real one. The strict Darwinian

answer has to be that retrogression is produced
Consideration ,._. j i i i

of the objection either by reversed selection, that is, that when

concerning de- by a change in the life habits or external condi-

generation,

tions a certain function or organ becomes inju-
rious, as in the case of insects on small exposed islands
where the wind might carry the flying ones off into the
ocean, selection, on the basis of advantage, would tend to
preserve the ones most poorly equipped for flight; or it
has to be that when the function of an organ is, because of
change in habit or conditions, once neglected or discon-
tinued, that is, the organ is no longer used, any slight varia-



DARWINISM DEFENDED. 147

tion toward reduction of the organ would be of advantage
because of the saving in food which would be effected ! But
this is simply carrying the logic of the principle of advan-
tage to an illogical extreme, an extreme impossible to accept.
So Weismann devised the ingenious explanation of pan-
mixia or cessation of selection to account for degeneration.
That is, a rigid and persistent selective activity is as neces-
sary to maintain a specialisation as it was to produce it.
But even Weismann has found this explanation inadequate
and has, therefore, found a final and sufficient explanation
in his new theory of germinal selection. This last theory, a
refinement of Roux's theory of the battle of the parts, is
ingenious, suggestive, and thoroughly interesting, but un-
fortunately it is founded on certain assumptions concerning
the ultimate make-up of the germ-plasm and the behaviour
of the unit parts of it, the truth of which simply cannot be
tested. A strictly neo-Darwinian answer, that is, one based
solely on selection, is therefore hard to give. Plate, 10 after
an effective adverse criticism of the influence of the Weis-
mannian panmixia as an explanation of the structural reduc-
tion or atrophy of parts, concludes that such reduced or
rudimentary organs are to be explained "through the
inherited effects of disuse, the inherited effects of the influ-
ences of external factors, the inherited effects of the influence
of economy in nutrition, and, in a few cases, through re-
versed selection. The first three principles are only admissi-
ble under the assumption of the actuality of the inheritance
of individually acquired characters, and the fourth principle
has only a very subordinate importance." This is equivalent
to saying that the strict selectionist has no sufficient answer
to the objection under present consideration. One seems
forced to rely on Lamarckian factors for anything like a
satisfactory explanation of actual structural reduction of
useless organs. Tayler, 11 however, offers an explanation
for both ontogenic and phyletic degeneration, based on the



I 4 8 DARWINISM TO-DAY.

"known facts of nutrition." The interested reader may find
this explanation in the appendix to this chapter.

Doubt is expressed by some biologists of the reality and
fierceness of the struggle for existence which is an essential
part of the selection theory. De Vries ex-

P resses the belief that the intra - s P ecinc strug-
againsttherig- gl e , that is, the struggle and competition among
' individuals of the same species, has been much
overrated. And a few observations ll have actually been
made which indicate that for certain species this struggle
is at least not rigorous enough to give to the slight Dar-
winian variations a determining value as to the character
of the surviving individuals. Here again the proof for the
Darwinian point of view is not one so much of observa-
tion although actual life-and-death combats between indi-
viduals of a single species, and innumerable examples of
the preying of one species on another are familiar as it is
a proof of reasoning. The fact of an over-production of
eggs and embryos, that is, of reproduction by multiplica-
tion, is undeniable. The lack of existing space and food
for all individuals, if all should live the ordinary span of
life peculiar to the species, is demonstrable by mathematics.
The consequent conclusion of these two established premises
is a struggle for existence. That is the sound Darwinian
position.

The principal answer of the Darwinians to the criticisms

levelled at the theory of sexual selection is, that however

ineffective the theory is to explain many of the

Answer to the , . J

objections to the phenomena it is called on to cover, it is at least



S mucl1 more reasonable and satisfying as an
explanation of some of the phenomena, that is,
some of the categories of secondary sexual characters, such
as the ornamental plumes and colour-patterns of birds, the
sound-making organs of insects, etc., than any alternative
explanation that has been offered, that until a better expla-



DARWINISM DEFENDED. 149

nation be presented the theory of sexual selection should
not be discarded. That no other explanation of many, if not
most, of the phenomena in question has anything at all
convincing or satisfactory about it, or has met with any
general acceptance on the part of naturalists, is the plain
truth. If we feel it imperative to give our adherence, with
certain reservations, to any explanatory hypothesis of sec-
ondary sexual characters, Darwin's theory is the one to
have first claim on us. As a matter of personal opinion I
feel no necessity for any such attitude and am willing to
look on most of the phenomena connected with the general
problem of secondary sexual characters as quite inexplica-
ble on the basis of our present knowledge of bionomics.

The specific answer of Lloyd Morgan 1S and other Dar-
winians to the objection that choice on the part of the
female assumes an aesthetic recognition and preference
which it is doing violence to our knowledge of animal
psychology to assume, should not be overlooked. This
answer is, put summarily, that this so-called choice is one
of impulse, not deliberation : it is an imperative reaction to
a sufficient stimulus : and what determines that the stimulus
from one male shall be sufficient while that from another is
not, is the degree of pronouncedness or effectiveness of the
ornament, or call, or behaviour. It is a choice "which is
determined by the emotional meaning of the conscious mean-
ing. And it is the reiterated revival of the associated
emotional elements which generates an impulse sufficiently
strong to overcome ter instinctive coyness and reluctance.
... It is a perceptual choice arising from impulse rather
than an ideational choice due to motive and volition."

Regarding Wolff's argument that an explanation of these
characters is very necessary to the acceptance of the theory
of natural selection there is little to say in rebuttal. Natural
selection confesses itself inadequate to explain those ex-
traordinary characters and conditions by which the males



: 5 o DARWINISM TO-DAY.

of many species of mammals, birds, insects, spiders, etc.,
. differ from the females. And if sexual selection does not
explain them then some other explanation is necessary. But
the lack of this explanation does not invalidate the general
theory of natural selection as one of the factors in organic
evolution and indeed one of the most important and far-
reaching ones.

The difficulty of a satisfactory discussion of the objection

that natural selection rests too largely on an assumed likeness

to artificial selection, while the differences in

Consideration the two processes, especially in their results, are

tnatnatXse- too radical to allow us to rest any confidence



on this a PP arent homology, is, that despite the
assumed analogy several thousand years through which artificial
r e ie h ctira fiCial selection has been followed and studied we

still know too little of the real character of it,
especially of its results. Most selectionists now admit that
the argument for natural selection on the basis of its sim-
ilarity to artificial selection has been given too great promi-
nence and relied on too strongly, but that the observed
processes of the one do teach us much of truth about the
unobservable processes of the other the Darwinians firmly.
maintain. As Plate says, "The great value of artificial
selection consists in this, that it shows first, that a gradual
cumulation of characteristics in definite directions is actually
possible through successive selections, and second, that it
has afforded us a rich mass of data concerning variation,
inheritance, and the influence of changing intrinsic condi-
tions or influences. When Darwin showed what a high
plasticity the domestic animals possess he built for his
theoretical explanation of descent an indubitable necessary
foundation, for the changes which a domestic animal passes
through in the hands of man must of necessity be able to
be called forth in similar manner in the feral animals by
the creative force of nature, for the domestic animals cer-



DARWINISM DEFENDED. 151

tainly have come from the wild ones. It is also true that
man has made use of only natural factors, and whoever will
compare the extraordinary creatures of the deep sea with
even the most bizarre of our cultivated races, will see that
the fluxing life-conditions of free nature can modify or
reform the animal world in no less degree than the intelli-
gence of man can do it. ...

"Recently de Vries, 14 in his book on 'Mutations/ has tried
to deny the worth of the selection principle, and although
I fully recognise the high worth of his contribution to science
based on such extensive series of experiments, yet I must
oppose him in this position. In various places in the book
he writes that nothing fixed can be produced by selection,
and that therefore it can have no importance as a working
factor in descent. For example, in the introduction (p. 6)
he says: 'Artificial selection never, as far as experience
reaches, leads to the origin of new complete types.' The
reversion of modified domesticated races is indubitable, and
de Vries himself has brought forward new illustrations of
this fact which has been so long known. But convincing
proof that natural selection cannot lead to constant forms
cannot be deduced from these observations, because they
refer in all cases to forms which have been highly modified
in the course of a few years or decades, so that the pre-
sumption lies close at hand that there has not been sufficient
time really and lastingly to modify the original heredity
established by centuries. Many facts indicate that the in-
tensity of heredity depends upon the number of generations,
that is, upon time. Long-inherited characters are difficult
to eradicate; recent ones easy. We can, therefore, not
expect to meet such a constancy in the products of a century
as we find in Nature. Many gradually selected races of
doves are now almost entirely constant, that is, no longer
revert to the primitive race when they are inter-bred. The
way in which the reversions appear shows that the duration



152 DARWINISM TO DAY.

of time plays an important role in inheritance (heredity).
Schubeler found in his studies of the translation of the
northern boundary of the grain culture that the characters
newly acquired (heavier and earlier ripening seeds) per-
sisted for several generations when the forms were replanted
in the original [more southerly] habitat. De Vries in six
years selected corn which had an average of 20 rows of
kernels instead of the original 12 to 14, and held the plants
at this height of production through five years. When he
then planted seed from a i6-rowed ear, the average of the
ears gathered from this planting was in the first generation
still at 20 rows, and sank only in the next two years again
to 14 to 16. If he had continued his selection longer he
would have arrived at a more nearly constant form. De
Vries himself says : 'When the selection ceases, the selected
characteristics drop away and in practically the same length
of time which was necessary for the production of the new
race, that is within a few generations.' From this it follows
that a domestic race produced by slow persistent selection
through many thousands of generations would show the
same relative constancy or fixity as natural species, the
majority of which also must have originated slowly, for
otherwise the appearance of new species would be often
observed. If one wishes to be very conservative in this
matter one may declare : in the light of our present knowl-
edge we cannot say that artificial selection gives us any safe
means of judging just what degree of constancy [fixity] can
be attained by its means ; but it is not fair to say that be-
cause up to the present only a partial constancy has been
reached through artificial selection, natural selection cannot
have led to the production of constant species. All culti-
vated races have been relatively quickly, some indeed very
quickly, selected 18 and, therefore, they strike back very
quickly. This, however, need not be assumed for the slowly
arisen products of natural selection."



DARWINISM DEFENDED.



'53



Tayler, 18 making a general defence of the natural selection

theory, says : "To realise how far the theory of selection is

Tayler'sgen- ca P able of explaining the facts of organic evo-

eral defense of lution, it is necessary to bear in mind the

natural selection, postulates on whkh the theory {s founded

"i. It is obvious that natural selection can only act by
preserving or eliminating the complete organism. Selection
must therefore be organismal. This Darwin and other
selectionists have clearly recognised.

"2. As the whole organism must survive, if the favoura-
ble variation or variations are to be preserved, it follows that
certain minor unfavourable variations may also be pre-
served if they happen to exist in an individual which sur-
vives on account of its major favourable variations. And



Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 14 of 38)