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EVOLUTION IN MODERN
THOUGHT
BY HAECKEL, THOMSON, WEISMANN
AND OTHERS
THE MODERN LIBRARY
PUBLISHERS :: :: NEW YORK
* * * * *
CONTENTS
I DARWIN'S PREDECESSORS
J. Arthur Thomson, Professor of Natural History in the University of
Aberdeen
II _The Selection Theory_
August Weismann, Professor of Zoology in the University of
Freiburg (Baden)
III HEREDITY AND VARIATION IN MODERN LIGHTS
W. Bateson, Professor of Biology in the University of Cambridge
IV "THE DESCENT OF MAN"
G. Schwalbe, Professor of Anatomy in the University of Strassburg
V CHARLES DARWIN AS AN ANTHROPOLOGIST
Ernst Haeckel, Professor of Zoology in the University of Jena
VI MENTAL FACTORS IN EVOLUTION
C. Lloyd Morgan, Professor of Psychology at University College,
Bristol
VII THE INFLUENCE OF THE CONCEPTION OF EVOLUTION ON MODERN PHILOSOPHY
H. Hoeffding, Professor of Philosophy in the University of Copenhagen
VIII THE INFLUENCE OF DARWIN UPON RELIGIOUS THOUGHT
Rev. P. H. Waggett
IX DARWINISM AND HISTORY
J. B. Bury, Regious Professor of Modern History in the University
of Cambridge
X DARWINISM AND SOCIOLOGY
C. Bougle, Professor of Social Philosophy in the University of
Toulouse, and Deputy-Professor at the Sorbonne, Paris
* * * * *
EVOLUTION IN MODERN THOUGHT
I
DARWIN'S PREDECESSORS
BY J. ARTHUR THOMSON
_Professor of Natural History in the University of Aberdeen_
In seeking to discover Darwin's relation to his predecessors it is
useful to distinguish the various services which he rendered to the
theory of organic evolution.
(I) As everyone knows, the general idea of the Doctrine of Descent is
that the plants and animals of the present day are the lineal
descendants of ancestors on the whole somewhat simpler, that these
again are descended from yet simpler forms, and so on backwards
towards the literal "Protozoa" and "Protophyta" about which we
unfortunately know nothing. Now no one supposes that Darwin originated
this idea, which in rudiment at least is as old as Aristotle. What
Darwin did was to make it current intellectual coin. He gave it a form
that commended itself to the scientific and public intelligence of the
day, and he won widespread conviction by showing with consummate skill
that it was an effective formula to work with, a key which no lock
refused. In a scholarly, critical, and pre-eminently fair-minded way,
admitting difficulties and removing them, foreseeing objections and
forestalling them, he showed that the doctrine of descent supplied a
modal interpretation of how our present-day fauna and flora have come
to be.
(II) In the second place, Darwin applied the evolution-idea to
particular problems, such as the descent of man, and showed what a
powerful organon it is, introducing order into masses of uncorrelated
facts, interpreting enigmas both of structure and function, both
bodily and mental, and, best of all, stimulating and guiding further
investigation. But here again it cannot be claimed that Darwin was
original. The problem of the descent or ascent of man, and other
particular cases of evolution, had attracted not a few naturalists
before Darwin's day, though no one [except Herbert Spencer in the
psychological domain (1855)] had come near him in precision and
thoroughness of inquiry.
(III) In the third place, Darwin contributed largely to a knowledge of
the factors in the evolution-process, especially by his analysis of
what occurs in the case of domestic animals and cultivated plants, and
by his elaboration of the theory of Natural Selection which Alfred
Russel Wallace independently stated at the same time, and of which
there had been a few previous suggestions of a more or less vague
description. It was here that Darwin's originality was greatest, for
he revealed to naturalists the many different forms--often very
subtle--which natural selection takes, and with the insight of a
disciplined scientific imagination he realised what a mighty engine of
progress it has been and is.
(IV) As an epoch-marking contribution, not only to AEtiology but to
Natural History in the widest sense, we rank the picture which Darwin
gave to the world of the web of life, that is to say, of the
inter-relations and linkages in Nature. For the Biology of the
individual--if that be not a contradiction in terms--no idea is more
fundamental than that of the correlation of organs, but Darwin's most
characteristic contribution was not less fundamental,--it was the idea
of the correlation of organisms. This, again, was not novel; we find
it in the works of naturalists like Christian Conrad Sprengel,
Gilbert White, and Alexander von Humboldt, but the realisation of its
full import was distinctly Darwinian.
_As Regards the General Idea of Organic Evolution_
While it is true, as Prof. H. F. Osborn puts it, that "'Before and
after Darwin' will always be the _ante et post urbem conditam_ of
biological history," it is also true that the general idea of organic
evolution is very ancient. In his admirable sketch _From the Greeks to
Darwin_,[1] Prof. Osborn has shown that several of the ancient
philosophers looked upon Nature as a gradual development and as still
in process of change. In the suggestions of Empedocles, to take the
best instance, there were "four sparks of truth,--first, that the
development of life was a gradual process; second, that plants were
evolved before animals; third, that imperfect forms were gradually
replaced (not succeeded) by perfect forms; fourth, that the natural
cause of the production of perfect forms was the extinction of the
imperfect."[2] But the fundamental idea of one stage giving origin to
another was absent. As the blue AEgean teemed with treasures of beauty
and threw many upon its shores, so did Nature produce like a fertile
artist what had to be rejected as well as what was able to survive,
but the idea of one species emerging out of another was not yet
conceived.
Aristotle's views of Nature[3] seem to have been more definitely
evolutionist than those of his predecessors, in this sense, at least,
that he recognised not only an ascending scale, but a genetic series
from polyp to man and an age-long movement towards perfection. "It is
due to the resistance of matter to form that Nature can only rise by
degrees from lower to higher types." "Nature produces those things
which, being continually moved by a certain principle contained in
themselves, arrive at a certain end."
To discern the outcrop of evolution-doctrine in the long interval
between Aristotle and Bacon seems to be very difficult, and some of
the instances that have been cited strike one as forced. Epicurus and
Lucretius, often called poets of evolution, both pictured animals as
arising directly out of the earth, very much as Milton's lion long
afterwards pawed its way out. Even when we come to Bruno who wrote
that "to the sound of the harp of the Universal Apollo (the World
Spirit), the lower organisms are called by stages to higher, and the
lower stages are connected by intermediate forms with the higher,"
there is great room, as Prof. Osborn points out,[4] for difference of
opinion as to how far he was an evolutionist in our sense of the term.
The awakening of natural science in the sixteenth century brought the
possibility of a concrete evolution theory nearer, and in the early
seventeenth century we find evidences of a new spirit--in the
embryology of Harvey and the classifications of Ray. Besides sober
naturalists there were speculative dreamers in the sixteenth and
seventeenth centuries who had at least got beyond static formulae,
but, as Professor Osborn points out,[5] "it is a very striking fact,
that the basis of our modern methods of studying the Evolution problem
was established not by the early naturalists nor by the speculative
writers, but by the Philosophers." He refers to Bacon, Descartes,
Leibnitz, Hume, Kant, Lessing, Herder, and Schelling. "They alone were
upon the main track of modern thought. It is evident that they were
groping in the dark for a working theory of the Evolution of life, and
it is remarkable that they clearly perceived from the outset that the
point to which observation should be directed was not the past but the
present mutability of species, and further, that this mutability was
simply the variation of individuals on an extended scale."
Bacon seems to have been one of the first to think definitely about
the mutability of species, and he was far ahead of his age in his
suggestion of what we now call a Station of Experimental Evolution.
Leibnitz discusses in so many words how the species of animals may be
changed and how intermediate species may once have linked those that
now seem discontinuous. "All natural orders of beings present but a
single chain".... "All advances by degrees in Nature, and nothing by
leaps." Similar evolutionist statements are to be found in the works
of the other "philosophers," to whom Prof. Osborn refers, who were,
indeed, more scientific than the naturalists of their day. It must be
borne in mind that the general idea of organic evolution--that the
present is the child of the past--is in great part just the idea of
human history projected upon the natural world, differentiated by the
qualification that the continuous "Becoming" has been wrought out by
forces inherent in the organisms themselves and in their environment.
A reference to Kant[6] should come in historical order after Buffon,
with whose writings he was acquainted, but he seems, along with Herder
and Schelling, to be best regarded as the culmination of the
evolutionist philosophers--of those at least who interested themselves
in scientific problems. In a famous passage he speaks of "the
agreement of so many kinds of animals in a certain common plan of
structure" ... an "analogy of forms" which "strengthens the
supposition that they have an actual blood-relationship, due to
derivation from a common parent." He speaks of "the great Family of
creatures, for as a Family we must conceive it, if the above-mentioned
continuous and connected relationship has a real foundation." Prof.
Osborn alludes to the scientific caution which led Kant, biology being
what it was, to refuse to entertain the hope "that a Newton may one
day arise even to make the production of a blade of grass
comprehensible, according to natural laws ordained by no intention."
As Prof. Haeckel finely observes, Darwin rose up as Kant's Newton.[7]
The scientific renaissance brought a wealth of fresh impressions and
some freedom from the tyranny of tradition, and the twofold stimulus
stirred the speculative activity of a great variety of men from old
Claude Duret of Moulins, of whose weird transformism (1609) Dr. Henry
de Varigny[8] gives us a glimpse, to Lorenz Oken (1779-1851) whose
writings are such mixtures of sense and nonsense that some regard him
as a far-seeing prophet and others as a fatuous follower of
intellectual will-o'-the-wisps. Similarly, for De Maillet, Maupertuis,
Diderot, Bonnet, and others, we must agree with Professor Osborn that
they were not actually in the main Evolution movement. Some have been
included in the roll of honour on very slender evidence, Robinet for
instance, whose evolutionism seems to us extremely dubious.[9]
The first naturalist to give a broad and concrete expression to the
evolutionist doctrine of descent was Buffon (1707-1788), but it is
interesting to recall the fact that his contemporary Linnaeus
(1707-1778), protagonist of the counter-doctrine of the fixity of
species,[10] went the length of admitting (in 1762) that new species
might arise by inter-crossing. Buffon's position among the pioneers of
the evolution-doctrine is weakened by his habit of vacillating between
his own conclusions and the orthodoxy of the Sorbonne, but there is no
doubt that he had firm grasp of the general idea of "l'enchainment des
etres."
Erasmus Darwin (1731-1802), probably influenced by Buffon, was another
firm evolutionist, and the outline of his argument in the
_Zoonomia_[11] might serve in part at least to-day. "When we revolve
in our minds the metamorphoses of animals, as from the tadpole to the
frog; secondly, the changes produced by artificial cultivation, as in
the breeds of horses, dogs, and sheep; thirdly, the changes produced
by conditions of climate and of season, as in the sheep of warm
climates being covered with hair instead of wool, and the hares and
partridges of northern climates becoming white in winter: when,
further, we observe the changes of structure produced by habit, as
seen especially in men of different occupations; or the changes
produced by artificial mutilation and prenatal influences, as in the
crossing of species and production of monsters; fourth, when we
observe the essential unity of plan in all warm-blooded animals,--we
are led to conclude that they have been alike produced from a similar
living filament".... "From thus meditating upon the minute portion of
time in which many of the above changes have been produced, would it
be too bold to imagine, in the great length of time since the earth
began to exist, perhaps millions of years before the commencement of
the history of mankind, that all warm-blooded animals have arisen from
one living filament?"... "This idea of the gradual generation of all
things seems to have been as familiar to the ancient philosophers as
to the modern ones, and to have given rise to the beautiful
hieroglyphic figure of the [Greek: proton oon], or first great egg,
produced by night, that is, whose origin is involved in obscurity, and
animated by [Greek: Eros], that is, by Divine Love; from whence
proceeded all things which exist."
Lamarck (1744-1829) seems to have become an evolutionist
independently of Erasmus Darwin's influence, though the parallelism
between them is striking. He probably owed something to Buffon, but he
developed his theory along a different line. Whatever view be held in
regard to that theory there is no doubt that Lamarck was a
thorough-going evolutionist. Professor Haeckel speaks of the
_Philosophie Zoologique_ as "the first connected and thoroughly
logical exposition of the theory of descent."[12]
Besides the three old masters, as we may call them, Buffon, Erasmus
Darwin, and Lamarck, there were other quite convinced pre-Darwinian
evolutionists. The historian of the theory of descent must take
account of Treviranus whose _Biology or Philosophy of Animate Nature_
is full of evolutionary suggestions; of Etienne Geoffroy St. Hilaire,
who in 1830, before the French Academy of Sciences, fought with
Cuvier, the fellow-worker of his youth, an intellectual duel on the
question of descent; of Goethe, one of the founders of morphology and
the greatest poet of Evolution--who, in his eighty-first year, heard
the tidings of Geoffrey St. Hilaire's defeat with an interest which
transcended the political anxieties of the time; and of many others
who had gained with more or less confidence and clearness a new
outlook on Nature. It will be remembered that Darwin refers to
thirty-four more or less evolutionist authors in his Historical
Sketch, and the list might be added to. Especially when we come near
to 1858 do the numbers increase, and one of the most remarkable, as
also most independent champions of the evolution-idea before that date
was Herbert Spencer, who not only marshalled the arguments in a very
forcible way in 1852, but applied the formula in detail in his
_Principles of Psychology_ in 1855.[13]
It is right and proper that we should shake ourselves free from all
creationist appreciations of Darwin, and that we should recognise the
services of pre-Darwinian evolutionists who helped to make the time
ripe, yet one cannot help feeling that the citation of them is apt to
suggest two fallacies. It may suggest that Darwin simply entered into
the labours of his predecessors, whereas, as a matter of fact, he knew
very little about them till after he had been for years at work. To
write, as Samuel Butler did, "Buffon planted, Erasmus Darwin and
Lamarck watered, but it was Mr. Darwin who said 'That fruit is ripe,'
and shook it into his lap" ... seems to us a quite misleading version
of the facts of the case. The second fallacy which the historical
citation is a little apt to suggest is that the filiation of ideas is
a simple problem. On the contrary, the history of an idea, like the
pedigree of an organism, is often very intricate, and the evolution of
the evolution-idea is bound up with the whole progress of the world.
Thus in order to interpret Darwin's clear formulation of the idea of
organic evolution and his convincing presentation of it, we have to do
more than go back to his immediate predecessors, such as Buffon,
Erasmus Darwin, and Lamarck; we have to inquire into the acceptance of
evolutionary conceptions in regard to other orders of facts, such as
the earth and the solar system;[14] we have to realise how the growing
success of scientific interpretation along other lines gave confidence
to those who refused to admit that there was any domain from which
science could be excluded as a trespasser; we have to take account of
the development of philosophical thought, and even of theological and
religious movements; we should also, if we are wise enough, consider
social changes. In short, we must abandon the idea that we can
understand the history of any science as such, without reference to
contemporary evolution in other departments of activity.
While there were many evolutionists before Darwin, few of them were
expert naturalists and few were known outside a small circle; what was
of much more importance was that the genetic view of Nature was
insinuating itself in regard to other than biological orders of facts,
here a little and there a little, and that the scientific spirit had
ripened since the days when Cuvier laughed Lamarck out of court. How
was it that Darwin succeeded where others had failed? Because, in the
first place, he had clear visions--"pensees de la jeunesse, executees
par l'age mur"--which a University curriculum had not made impossible,
which the _Beagle voyage_ made vivid, which an unrivalled British
doggedness made real--visions of the web of life, of the fountain of
change within the organism, of the struggle for existence and its
winnowing, and of the spreading genealogical tree. Because, in the
second place, he put so much grit into the verification of his
visions, putting them to the proof in an argument which is of its
kind--direct demonstration being out of the question--quite
unequalled. Because, in the third place, he broke down the opposition
which the most scientific had felt to the seductive modal formula of
evolution by bringing forward a more plausible theory of the process
than had been previously suggested. Nor can one forget, since
questions of this magnitude are human and not merely academic, that he
wrote so that all men could understand.
_As Regards the Factors of Evolution_
It is admitted by all who are acquainted with the history of biology
that the general idea of organic evolution as expressed in the
Doctrine of Descent was quite familiar to Darwin's grandfather and to
others before and after him, as we have briefly indicated. It must
also be admitted that some of these pioneers of evolutionism did more
than apply the evolution-idea as a modal formula of becoming, they
began to inquire into the factors in the process. Thus there were
pre-Darwinian theories of evolution, and to these we must now briefly
refer.[15]
In all biological thinking we have to work with the categories
Organism--Function--Environment, and theories of evolution may be
classified in relation to these. To some it has always seemed that the
fundamental fact is the living organism,--a creative agent, a striving
will, a changeful Proteus, selecting its environment, adjusting itself
to it, self-differentiating and self-adaptive. The necessity of
recognising the importance of the organism is admitted by all
Darwinians who start with inborn variations, but it is open to
question whether the whole truth of what we might call the Goethian
position is exhausted in the postulate of inherent variability.
To others it has always seemed that the emphasis should be laid on
Function,--on use and disuse, on doing and not doing. Practice makes
perfect; _c'est a force de forger qu'on devient forgeron_. This is one
of the fundamental ideas of Lamarckism; to some extent it met with
Darwin's approval; and it finds many supporters to-day. One of the
ablest of these--Mr. Francis Darwin--has recently given strong reasons
for combining a modernised Lamarckism with what we usually regard as
sound Darwinism.[16]
To others it has always seemed that the emphasis should be laid on the
Environment, which wakes the organism to action, prompts it to change,
makes dints upon it, moulds it, prunes it, and finally, perhaps, kills it.
It is again impossible to doubt that there is truth in this view, for even
if environmentally induced "modifications" be not transmissible,
environmentally induced "variations" are; and even if the direct influence
of the environment be less important than many enthusiastic supporters of
this view--may we call them Buffonians--think, there remains the indirect
influence which Darwinians in part rely on,--the eliminative process. Even
if the extreme view be held that the only form of discriminate elimination
that counts is inter-organismal competition, this might be included under
the rubric of the animate environment.
In many passages Buffon[17] definitely suggested that environmental
influences--especially of climate and food--were directly productive
of changes in organisms, but he did not discuss the question of the
transmissibility of the modifications so induced, and it is difficult
to gather from his inconsistent writings what extent of transformation
he really believed in. Prof. Osborn says of Buffon: "The struggle for
existence, the elimination of the least-perfected species, the contest
between the fecundity of certain species and their constant
destruction, are all clearly expressed in various passages." He quotes
two of these:[18]
"Le cours ordinaire de la nature vivante, est en general toujours
constant, toujours le meme; son mouvement, toujours regulier, roule
sur deux points inebranlables: l'un, la fecondite sans bornes donnee a
toutes les especes; l'autre, les obstacles sans nombre qui reduisent
cette fecondite a une mesure determinee et ne laissent en tout temps
qu'a peu pres la meme quantite d'individus de chaque espece" ... "Les
especes les moins parfaites, les plus delicates, les plus pesantes,
les moins agissantes, les moins armees, etc., ont deja disparu ou
disparaitront.".
Erasmus Darwin[19] had a firm grip of the "idea of the gradual
formation and improvement of the Animal world," and he had his theory
of the process. No sentence is more characteristic than this: "All
animals undergo transformations which are in part produced by their
own exertions, in response to pleasures and pains, and many of these
acquired forms or propensities are transmitted to their posterity."
This is Lamarckism before Lamarck, as his grandson pointed out. His
central idea is that wants stimulate efforts and that these result in
improvements which subsequent generations make better still. He
realised something of the struggle for existence and even pointed out
that this advantageously checks the rapid multiplication. "As Dr.
Krause points out, Darwin just misses the connection between this
struggle and the Survival of the Fittest."[20]
Lamarck[21] (1744-1829) seems to have thought out his theory of
evolution without any knowledge of Erasmus Darwin's which it closely
resembled. The central idea of his theory was the cumulative
inheritance of functional modifications. "Changes in environment bring
about changes in the habits of animals. Changes in their wants
necessarily bring about parallel changes in their habits. If new wants
become constant or very lasting, they form new habits, the new habits
involve the use of new parts, or a different use of old parts, which
results finally in the production of new organs and the modification
of old ones." He differed from Buffon in not attaching importance, as
far as animals are concerned, to the direct influence of the
environment, "for environment can effect no direct change whatever
upon the organisation of animals," but in regard to plants he agreed
with Buffon that external conditions directly moulded them.
Treviranus[22] (1776-1837), whom Huxley ranked beside Lamarck, was on
the whole Buffonian, attaching chief importance to the influence of a
changeful environment both in modifying and in eliminating, but he was
also Goethian, for instance in his idea that species like individuals
pass through periods of growth, full bloom, and decline. "Thus, it is
not only the great catastrophes of Nature which have caused
extinction, but the completion of cycles of existence, out of which
new cycles have begun." A characteristic sentence is quoted by Prof.
Osborn: "In every living being there exists a capability of an endless
variety of form-assumption; each possesses the power to adapt its
organisation to the changes of the outer world, and it is this power,
put into action by the change of the universe, that has raised the
simple zoophytes of the primitive world to continually higher stages
of organisation, and has introduced a countless variety of species
into animate Nature."
Goethe[23] (1749-1832), who knew Buffon's work but not Lamarck's, is
peculiarly interesting as one of the first to use the evolution-idea
as a guiding hypothesis, e.g. in the interpretation of vestigial
structures in man, and to realise that organisms express an attempt to
make a compromise between specific inertia and individual change. He
gave the finest expression that science has yet known--if it has known
it--of the kernel-idea of what is called "bathmism," the idea of an
"inherent growth-force"--and at the same time he held that "the way of
life powerfully reacts upon all form" and that the orderly growth of
form "yields to change from externally acting causes."
Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe,
there were other "pioneers of evolution," whose views have been often
discussed and appraised. Etienne Geoffroy Saint-Hilaire (1772-1884),
whose work Goethe so much admired, was on the whole Buffonian,
emphasising the direct action of the changeful _milieu_. "Species vary
with their environment, and existing species have descended by
modification from earlier and somewhat simpler species." He had a
glimpse of the selection idea, and believed in mutations or sudden
leaps--induced in the embryonic condition by external influences. The
complete history of evolution-theories will include many instances of
guesses at truth which were afterwards substantiated, thus the
geographer von Buch (1773-1853) detected the importance of the
Isolation factor on which Wagner, Romanes, Gulick and others have laid
great stress, but we must content ourselves with recalling one other
pioneer, the author of the _Vestiges of Creation_ (1844), a work which
passed through ten editions in nine years and certainly helped to
harrow the soil for Darwin's sowing. As Darwin said, "it did excellent
service in this country in calling attention to the subject, in
removing prejudice, and in thus preparing the ground for the reception
of analogous views."[24] Its author, Robert Chambers (1802-1871) was
in part a Buffonian--maintaining that environment moulded organisms
adaptively, and in part a Goethian--believing in an inherent
progressive impulse which lifted organisms from one grade of
organisation to another.
_As Regards Natural Selection_
The only thinker to whom Darwin was directly indebted, so far as the
theory of Natural Selection is concerned, was Malthus, and we may once
more quote the well-known passage in the Autobiography: "In October,
1838, that is, fifteen months after I had begun my systematic enquiry,
I happened to read for amusement 'Malthus on Population,' and being
well prepared to appreciate the struggle for existence which
everywhere goes on from long-continued observation of the habits of
animals and plants, it at once struck me that under these
circumstances favourable variations would tend to be preserved, and
unfavourable ones to be destroyed. The result of this would be the
formation of new species."[25]
Although Malthus gives no adumbration of the idea of Natural Selection
in his exposition of the eliminative processes which go on in mankind,
the suggestive value of his essay is undeniable, as is strikingly
borne out by the fact that it gave to Alfred Russel Wallace also "the
long-sought clue to the effective agent in the evolution of organic
species."[26] One day in Ternate when he was resting between fits of
fever, something brought to his recollection the work of Malthus which
he had read twelve years before. "I thought of his clear exposition of
'the positive checks to increase'--disease, accidents, war, and
famine--which keep down the population of savage races to so much
lower an average than that of more civilized peoples. It then occurred
to me that these causes or their equivalents are continually acting in
the case of animals also; and as animals usually breed much more
rapidly than does mankind, the destruction every year from these
causes must be enormous in order to keep down the numbers of each
species, since they evidently do not increase regularly from year to
year, as otherwise the world would long ago have been densely crowded
with those that breed most quickly. Vaguely thinking over the enormous
and constant destruction which this implied, it occurred to me to ask
the question, Why do some die and some live? And the answer was
clearly, that on the whole the best fitted live. From the effects of
disease the most healthy escaped; from enemies the strongest, the
swiftest, or the most cunning; from famine the best hunters or those
with the best digestion; and so on. Then it suddenly flashed upon me
that this self-acting process would necessarily _improve the race_,
because in every generation the inferior would inevitably be killed
off and the superior would remain--that is, _the fittest would
survive_."[27] We need not apologise for this long quotation, it is a
tribute to Darwin's magnanimous colleague, the Nestor of the
evolutionist camp,--and it probably indicates the line of thought
which Darwin himself followed. It is interesting also to recall the
fact that in 1852, when Herbert Spencer wrote his famous _Leader_
article on "The Development Hypothesis" in which he argued powerfully
for the thesis that the whole animate world is the result of an
age-long process of natural transformation, he wrote for _The
Westminster Review_ another important essay, "A Theory of Population
deduced from the General Law of Animal Fertility," towards the close
of which he came within an ace of recognising that the struggle for
existence was a factor in organic evolution. At a time when pressure
of population was practically interesting men's minds, Darwin,
Wallace, and Spencer were being independently led from a social
problem to a biological theory. There could be no better illustration,
as Prof. Patrick Geddes has pointed out, of the Comtian thesis that
science is a "social phenomenon."
Therefore, as far more important than any further ferreting out of
vague hints of Natural Selection in books which Darwin never read, we
would indicate by a quotation the view that the central idea in
Darwinism is correlated with contemporary social evolution. "The
substitution of Darwin for Paley as the chief interpreter of the order
of nature is currently regarded as the displacement of an
anthropomorphic view by a purely scientific one: a little reflection,
however, will show that what has actually happened has been merely the
replacement of the anthropomorphism of the eighteenth century by that
of the nineteenth. For the place vacated by Paley's theological and
metaphysical explanation has simply been occupied by that suggested to
Darwin and Wallace by Malthus in terms of the prevalent severity of
industrial competition, and those phenomena of the struggle for
existence which the light of contemporary economic theory has enabled
us to discern, have thus come to be temporarily exalted into a
complete explanation of organic progress."[28] It goes without saying
that the idea suggested by Malthus was developed by Darwin into a
biological theory which was then painstakingly verified by being used
as an interpretative formula, and that the validity of a theory so
established is not affected by what suggested it, but the practical
question which this line of thought raises in the mind is this: if
Biology did thus borrow with such splendid results from social theory,
why should we not more deliberately repeat the experiment?
Darwin was characteristically frank and generous in admitting that the
principle of Natural Selection had been independently recognised by
Dr. W. C. Wells in 1813 and by Mr. Patrick Matthew in 1831, but he had
no knowledge of these anticipations when he published the first
edition of _The Origin of Species_. Wells, whose "Essay on Dew" is
still remembered, read in 1813 before the Royal Society a short paper
entitled "An Account of a White Female, part of whose skin resembles
that of a Negro" (published in 1818). In this communication, as Darwin
said, "he observes, firstly, that all animals tend to vary in some
degree, and, secondly, that agriculturists improve their domesticated
animals by selection; and then, he adds, but what is done in this
latter case 'by art, seems to be done with equal efficacy, though more
slowly, by nature, in the formation of varieties of mankind, fitted
for the country which they inhabit.'"[29] Thus Wells had the clear
idea of survival dependent upon a favourable variation, but he makes
no more use of the idea and applies it only to man. There is not in
the paper the least hint that the author ever thought of generalising
the remarkable sentence quoted above.
Of Mr. Patrick Matthew, who buried his treasure in an appendix to a
work on _Naval Timber and Arboriculture_, Darwin said that "he clearly
saw the full force of the principle of natural selection." In 1860
Darwin wrote--very characteristically--about this to Lyell: "Mr.
Patrick Matthew publishes a long extract from his work on _Naval
Timber and Arboriculture_, published in 1831, in which he briefly but
completely anticipates the theory of Natural Selection. I have ordered
the book, as some passages are rather obscure, but it is certainly, I
think, a complete but not developed anticipation. Erasmus always said
that surely this would be shown to be the case some day. Anyhow, one
may be excused in not having discovered the fact in a work on Naval
Timber."[30]
De Quatrefages and De Varigny have maintained that the botanist Naudin
stated the theory of evolution by natural selection in 1852. He
explains very clearly the process of artificial selection, and says
that in the garden we are following Nature's method. "We do not think
that Nature has made her species in a different fashion from that in
which we proceed ourselves in order to make our variations." But, as
Darwin said, "he does not show how selection acts under nature."
Similarly it must be noted in regard to several pre-Darwinian pictures
of the struggle for existence (such as Herder's, who wrote in 1790
"All is in struggle ... each one for himself" and so on), that a
recognition of this is only the first step in Darwinism.
Profs. E. Perrier and H. F. Osborn have called attention to a
remarkable anticipation of the selection-idea which is to be found in
the speculations of Etienne Geoffroy Saint-Hilaire (1825-1828) on the
evolution of modern Crocodilians from the ancient Teleosaurs. Changing
environment induced changes in the respiratory system and far-reaching
consequences followed. The atmosphere, acting upon the pulmonary
cells, brings about "modifications which are favourable or destructive
('funestes'); these are inherited, and they influence all the rest of
the organisation of the animal because if these modifications lead to
injurious effects the animals which exhibit them perish and are
replaced by others of a somewhat different form, a form changed so as
to be adapted to (a la convenance) the new environment."
Prof. E. B. Poulton[31] has shown that the anthropologist James Cowles
Prichard (1786-1848) must be included even in spite of himself among
the precursors of Darwin. In some passages of the second edition of
his _Researches into the Physical History of Mankind_ (1826), he
certainly talks evolution and anticipates Prof. Weismann in denying
the transmission of acquired characters. He is, however, sadly
self-contradictory and his evolutionism weakens in subsequent
editions--the only ones that Darwin saw. Prof. Poulton finds in
Prichard's work a recognition of the operation of Natural Selection.
"After inquiring how it is that 'these varieties are developed and
preserved in connexion with particular climates and differences of
local situation,' he gives the following very significant answer: 'One
cause which tends to maintain this relation is obvious. Individuals
and families, and even whole colonies perish and disappear in climates
for which they are, by peculiarity of constitution, not adapted. Of
this fact proofs have been already mentioned.'" Mr. Francis Darwin and
Prof. A. C. Seward discuss Prichard's "anticipations" in _More Letters
of Charles Darwin_, Vol. _I._ p. 43, and come to the conclusion that
the evolutionary passages are entirely neutralised by others of an
opposite trend. There is the same difficulty with Buffon.
Hints of the idea of Natural Selection have been detected elsewhere.
James Watt,[32] for instance, has been reported as one of the
anticipators (1851). But we need not prolong the inquiry further,
since Darwin did not know of any anticipations until after he had
published the immortal work of 1859, and since none of those who got
hold of the idea made any use of it. What Darwin did was to follow the
clue which Malthus gave him, to realise, first by genius and
afterwards by patience, how the complex and subtle struggle for
existence works out a natural selection of those organisms which vary
in the direction of fitter adaptation to the conditions of their life.
So much success attended his application of the Selection-formula that
for a time he regarded Natural Selection as almost the sole factor in
evolution, variations being pre-supposed; gradually, however, he came
to recognise that there was some validity in the factors which had
been emphasised by Lamarck and by Buffon, and in his well known
summing up in the sixth edition of the _Origin_ he says of the
transformation of species: "This has been effected chiefly through the
natural selection of numerous successive, slight, favourable
variations; aided in an important manner by the inherited effects of
the use and disuse of parts; and in an unimportant manner, that is, in
relation to adaptive structures, whether past or present, by the
direct action of external conditions, and by variations which seem to
us in our ignorance to arise spontaneously."
To sum up: the idea of organic evolution, older than Aristotle, slowly
developed from the stage of suggestion to the stage of verification,
and the first convincing verification was Darwin's; from being an _a
priori_ anticipation it has become an interpretation of nature, and
Darwin is still the chief interpreter; from being a modal
interpretation it has advanced to the rank of a causal theory, the
most convincing part of which men will never cease to call Darwinism.
FOOTNOTES:
[Footnote 1: _Columbia University Biological Series_, Vol. I. New York
and London, 1894. We must acknowledge our great indebtedness to this
fine piece of work.]
[Footnote 2: _op. cit._ p. 41.]
[Footnote 3: See G. J. Romanes, "Aristotle as a Naturalist,"
_Contemporary Review_, Vol. lix. p. 275, 1891; G. Pouchet, _La
Biologie Aristotelique_, Paris, 1885; E. Zeller, _A History of Greek
Philosophy_, London, 1881, and "Ueber die griechischen Vorgaenger
Darwin's," _Abhandl. Berlin Akad._ 1878, pp. 111-124.]
[Footnote 4: _op. cit._ p. 81.]
[Footnote 5: _op. cit._ p. 87.]
[Footnote 6: See Brock, "Die Stellung Kant's zur Deszendenztheorie,"
_Biol. Centralbl._ viii. 1889, pp. 641-648. Fritz Schultze, _Kant und
Darwin_, Jena, 1875.]
[Footnote 7: Mr. Alfred Russel Wallace writes: "We claim for Darwin
that he is the Newton of natural history, and that, just so surely as
that the discovery and demonstration by Newton of the law of
gravitation established order in place of chaos and laid a sure
foundation for all future study of the starry heavens, so surely has
Darwin, by his discovery of the law of natural selection and his
demonstration of the great principle of the preservation of useful
variations in the struggle for life, not only thrown a flood of light
on the process of development of the whole organic world, but also
established a firm foundation for all future study of nature"
(_Darwinism_, London, 1889, p. 9). See also Prof. Karl Pearson's
_Grammar of Science_ (2nd edit.), London, 1900, p. 32. See Osborn,
_op. cit._ p. 100.]
[Footnote 8: _Experimental Evolution_. London, 1892. Chap. I. p. 14.]
[Footnote 9: See J. Arthur Thomson, _The Science of Life_. London,
1899, Chap. XVI. "Evolution of Evolution Theory."]
[Footnote 10: See Carus Sterne (Ernst Krause), _Die allgemeine
Weltanschauung in ihrer historischen Entwickelung_. Stuttgart, 1889.
Chapter entitled "Bestaendigkeit oder Veraenderlichkeit der
Naturwesen."]
[Footnote 11: _Zoonomia, or the Laws of Organic Life_, 2 vols. London,
1794; Osborn, _op. cit._ p. 145.]
[Footnote 12: See Alpheus S. Packard, _Lamarck, the Founder of
Evolution, His Life and Work, with Translations of his writings on
Organic Evolution_. London, 1901.]
[Footnote 13: See Edward Clodd, _Pioneers of Evolution_, London, p.
161, 1897.]
[Footnote 14: See Chapter ix. "The Genetic View of Nature" in J. T.
Merz's _History of European Thought in the Nineteenth Century_, Vol.
2, Edinburgh and London, 1903.]
[Footnote 15: See Prof. W. A. Locy's _Biology and its Makers_. New
York, 1908. Part II. "The Doctrine of Organic Evolution."]
[Footnote 16: Presidential Address to the British Association meeting
at Dublin in 1908.]
[Footnote 17: See in particular Samuel Butler, _Evolution Old and
New_, London, 1879; J. L. de Lanessan, "Buffon et Darwin," _Revue
Scientifique_, XLIII. pp. 385-391, 425-432, 1889.]
[Footnote 18: _op. cit._ p. 136.]
[Footnote 19: See Ernest Krause and Charles Darwin, _Erasmus Darwin_,
London, 1879.]
[Footnote 20: Osborn, _op. cit._ p. 142.]
[Footnote 21: See E. Perrier, _La Philosophie Zoologique avant
Darwin_, Paris, 1884; A. de Quatrefages, _Darwin et ses Precurseurs
Francais_, Paris, 1870; Packard, _op. cit._; also Claus, _Lamarck als
Begruender der Descendenzlehre_, Wien, 1888; Haeckel, _Natural History
of Creation_, Eng. transl. London, 1879; Lang, _Zur Charakteristik der
Forschungswege von Lamarck und Darwin_, Jena, 1889.]
[Footnote 22: See Huxley's article "Evolution in Biology,"
_Encyclopaedia Britannica_ (9th edit.), 1879, pp. 744-751, and Sully's
article, "Evolution in Philosophy," _ibid._ pp. 751-772.]
[Footnote 23: See Haeckel, _Die Naturanschauung von Darwin, Goethe und
Lamarck_, Jena, 1882.]
[Footnote 24: _Origin of Species_ (6th edit.), p. xvii.]
[Footnote 25: _The Life and Letters of Charles Darwin_, Vol. 1. p. 83.
London, 1887.]
[Footnote 26: A. R. Wallace, _My Life, a Record of Events and
Opinions_, London, 1905, Vol. 1, p. 232.]
[Footnote 27: _My Life_, Vol. 1. p. 361.]
[Footnote 28: P. Geddes. article "Biology." _Chambers's
Encyclopaedia._]
[Footnote 29: _Origin of Species_ (6th edit.), p. xv.]
[Footnote 30: _Life and Letters_, II, p. 301.]
[Footnote 31: _Science Progress_, New Series, Vol. 1. 1897. "A
Remarkable Anticipation of Modern Views on Evolution." See also Chap.
VI. in _Essays on Evolution_, Oxford, 1908.]
[Footnote 32: See Prof. Patrick Geddes's article "Variation and
Selection," _Encyclopaedia Britannica_ (9th edit.) 1888.]
II
THE SELECTION THEORY
BY AUGUST WEISMANN
_Professor of Zoology in the University of Freiburg_ (_Baden_)
I. THE IDEA OF SELECTION
Many and diverse were the discoveries made by Charles Darwin in the
course of a long and strenuous life, but none of them has had so
far-reaching an influence on the science and thought of his time as
the theory of selection. I do not believe that the theory of evolution
would have made its way so easily and so quickly after Darwin took up
the cudgels in favour of it if he had not been able to support it by a
principle which was capable of solving, in a simple manner, the
greatest riddle that living nature presents to us,--I mean the
purposiveness of every living form relative to the conditions of its
life and its marvellously exact adaptation to these.
Everyone knows that Darwin was not alone in discovering the principle
of selection, and that the same idea occurred simultaneously and
independently to Alfred Russel Wallace. At the memorable meeting of
the Linnean Society on 1st July, 1858, two papers were read
(communicated by Lyell and Hooker) both setting forth the same idea of
selection. One was written by Charles Darwin in Kent, the other by
Alfred Wallace in Ternate, in the Malay Archipelago. It was a splendid
proof of the magnanimity of these two investigators, that they thus in
all friendliness and without envy, united in laying their ideas
before a scientific tribunal: their names will always shine side by
side as two of the brightest stars in the scientific sky.
The idea of selection set forth by the two naturalists was at the time
absolutely new, but it was also so simple that Huxley could say of it
later, "How extremely stupid not to have thought of that." As Darwin
was led to the general doctrine of descent, not through the labours of
his predecessors in the early years of the century, but by his own
observations, so it was in regard to the principle of selection. He
was struck by the innumerable cases of adaptation, as, for instance,
that of the woodpeckers and tree-frogs to climbing, or the hooks and
feather-like appendages of seeds, which aid in the distribution of
plants, and he said to himself that an explanation of adaptations was
the first thing to be sought for in attempting to formulate a theory
of evolution.
But since adaptations point to _changes_ which have been undergone by
the ancestral forms of existing species, it is necessary, first of
all, to inquire how far species in general are _variable_. Thus
Darwin's attention was directed in the first place to the phenomenon
of variability, and the use man has made of this, from very early
times, in the breeding of his domesticated animals and cultivated
plants. He inquired carefully how breeders set to work, when they
wished to modify the structure and appearance of a species to their
own ends, and it was soon clear to him that _selection for breeding
purposes_ played the chief part.
But how was it possible that such processes should occur in free
nature? Who is here the breeder, making the selection, choosing out
one individual to bring forth offspring and rejecting others? That was
the problem that for a long time remained a riddle to him.