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Title: Evolution in Modern Thought

Author: Ernst Haeckel

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EVOLUTION IN

MODERN

THOUGHT

BY HAECKEL, THOMSON, WEISMANN AND OTHERS

THE MODERN LIBRARYPUBLISHERS :: :: NEW YORK

VIII The Influence of

Deputy-Professor at the

Sorbonne, Paris

EVOLUTION IN MODERN THOUGHT

I

(I) As everyone knows, the general idea ofthe Doctrine of Descent is that the plantsand animals of the present day are the

lineal descendants of ancestors on thewhole somewhat simpler, that these againare descended from yet simpler forms, and

so on backwards towards the literal

"Protozoa" and "Protophyta" about which

we unfortunately know nothing Now noone supposes that Darwin originated thisidea, which in rudiment at least is as old

as Aristotle What Darwin did was tomake it current intellectual coin He gave

it a form that commended itself to thescientific and public intelligence of theday, and he won widespread conviction

by showing with consummate skill that itwas an effective formula to work with, akey which no lock refused In a scholarly,critical, and pre-eminently fair-mindedway, admitting difficulties and removingthem, foreseeing objections and

forestalling them, he showed that thedoctrine of descent supplied a modalinterpretation of how our present-dayfauna and flora have come to be.

(II) In the second place, Darwin appliedthe evolution-idea to particular problems,such as the descent of man, and showedwhat a powerful organon it is, introducingorder into masses of uncorrelated facts,interpreting enigmas both of structure andfunction, both bodily and mental, and, best

of all, stimulating and guiding furtherinvestigation But here again it cannot beclaimed that Darwin was original Theproblem of the descent or ascent of man,and other particular cases of evolution,had attracted not a few naturalists beforeDarwin's day, though no one [except

Herbert Spencer in the psychologicaldomain (1855)] had come near him inprecision and thoroughness of inquiry.(III) In the third place, Darwin contributedlargely to a knowledge of the factors in theevolution-process, especially by hisanalysis of what occurs in the case ofdomestic animals and cultivated plants,and by his elaboration of the theory ofNatural Selection which Alfred RusselWallace independently stated at the sametime, and of which there had been a fewprevious suggestions of a more or lessvague description It was here thatDarwin's originality was greatest, for herevealed to naturalists the many differentforms—often very subtle—which naturalselection takes, and with the insight of a

disciplined scientific imagination herealised what a mighty engine of progress

it has been and is

(IV) As an epoch-marking contribution,not only to Ætiology but to NaturalHistory in the widest sense, we rank thepicture which Darwin gave to the world

of the web of life, that is to say, of theinter-relations and linkages in Nature Forthe Biology of the individual—if that benot a contradiction in terms—no idea ismore fundamental than that of thecorrelation of organs, but Darwin's mostcharacteristic contribution was not lessfundamental,—it was the idea of thecorrelation of organisms This, again, wasnot novel; we find it in the works ofnaturalists like Christian Conrad Sprengel,

Gilbert White, and Alexander vonHumboldt, but the realisation of its fullimport 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' willalways be the ante et post urbem

conditam of biological history," it is also

true that the general idea of organicevolution is very ancient In his admirable

sketch From the Greeks to Darwin ,[1]

Prof Osborn has shown that several of theancient philosophers looked upon Nature

as a gradual development and as still inprocess of change In the suggestions ofEmpedocles, to take the best instance,there were "four sparks of truth,—first,

that the development of life was a gradualprocess; second, that plants were evolvedbefore animals; third, that imperfect formswere gradually replaced (not succeeded)

by perfect forms; fourth, that the naturalcause of the production of perfect formswas the extinction of the imperfect."[2] Butthe fundamental idea of one stage givingorigin to another was absent As the blueÆgean teemed with treasures of beautyand threw many upon its shores, so didNature produce like a fertile artist whathad to be rejected as well as what wasable to survive, but the idea of onespecies emerging out of another was notyet conceived

Aristotle's views of Nature[3] seem tohave been more definitely evolutionist

than those of his predecessors, in thissense, at least, that he recognised not only

an ascending scale, but a genetic seriesfrom polyp to man and an age-longmovement towards perfection "It is due tothe resistance of matter to form that Naturecan only rise by degrees from lower tohigher types." "Nature produces thosethings which, being continually moved by

a certain principle contained inthemselves, arrive at a certain end."

To discern the outcrop of doctrine in the long interval betweenAristotle and Bacon seems to be verydifficult, and some of the instances thathave been cited strike one as forced.Epicurus and Lucretius, often called poets

evolution-of evolution, both pictured animals as

arising directly out of the earth, very much

as Milton's lion long afterwards pawed itsway out Even when we come to Brunowho wrote that "to the sound of the harp ofthe Universal Apollo (the World Spirit),the lower organisms are called by stages

to higher, and the lower stages areconnected by intermediate forms with thehigher," there is great room, as Prof.Osborn points out,[4] for difference ofopinion as to how far he was anevolutionist in our sense of the term

The awakening of natural science in thesixteenth century brought the possibility of

a concrete evolution theory nearer, and inthe early seventeenth century we findevidences of a new spirit—in the

classifications of Ray Besides sobernaturalists there were speculativedreamers in the sixteenth and seventeenthcenturies who had at least got beyondstatic formulae, but, as Professor Osbornpoints out,[5] "it is a very striking fact, thatthe basis of our modern methods ofstudying the Evolution problem wasestablished not by the early naturalists nor

by the speculative writers, but by thePhilosophers." He refers to Bacon,Descartes, Leibnitz, Hume, Kant, Lessing,Herder, and Schelling "They alone wereupon the main track of modern thought It

is evident that they were groping in thedark for a working theory of the Evolution

of life, and it is remarkable that theyclearly perceived from the outset that thepoint to which observation should be

directed was not the past but the presentmutability of species, and further, that thismutability was simply the variation ofindividuals on an extended scale."

Bacon seems to have been one of the first

to think definitely about the mutability ofspecies, and he was far ahead of his age inhis suggestion of what we now call aStation of Experimental Evolution.Leibnitz discusses in so many words howthe species of animals may be changedand how intermediate species may oncehave linked those that now seemdiscontinuous "All natural orders ofbeings present but a single chain" "Alladvances by degrees in Nature, andnothing by leaps." Similar evolutioniststatements are to be found in the works of

the other "philosophers," to whom Prof.Osborn refers, who were, indeed, morescientific than the naturalists of their day.

It must be borne in mind that the generalidea of organic evolution—that the present

is the child of the past—is in great partjust the idea of human history projectedupon the natural world, differentiated bythe qualification that the continuous

"Becoming" has been wrought out byforces inherent in the organismsthemselves and in their environment

A reference to Kant[6] should come inhistorical order after Buffon, with whosewritings he was acquainted, but he seems,along with Herder and Schelling, to bebest regarded as the culmination of theevolutionist philosophers—of those at

least who interested themselves inscientific problems In a famous passage

he speaks of "the agreement of so manykinds of animals in a certain common plan

of structure" an "analogy of forms"which "strengthens the supposition thatthey have an actual blood-relationship,due to derivation from a common parent."

He speaks of "the great Family ofcreatures, for as a Family we mustconceive it, if the above-mentionedcontinuous and connected relationship has

a real foundation." Prof Osborn alludes tothe scientific caution which led Kant,biology being what it was, to refuse toentertain the hope "that a Newton may oneday arise even to make the production of ablade of grass comprehensible, according

to natural laws ordained by no intention."

As Prof Haeckel finely observes, Darwinrose up as Kant's Newton.[7]

The scientific renaissance brought awealth of fresh impressions and somefreedom from the tyranny of tradition, andthe twofold stimulus stirred thespeculative activity of a great variety ofmen from old Claude Duret of Moulins, ofwhose weird transformism (1609) Dr.Henry de Varigny[8] gives us a glimpse, toLorenz Oken (1779-1851) whose writingsare such mixtures of sense and nonsensethat some regard him as a far-seeingprophet and others as a fatuous follower

of intellectual will-o'-the-wisps.Similarly, for De Maillet, Maupertuis,Diderot, Bonnet, and others, we mustagree with Professor Osborn that they

were not actually in the main Evolutionmovement Some have been included inthe roll of honour on very slenderevidence, Robinet for instance, whoseevolutionism seems to us extremelydubious.[9]

The first naturalist to give a broad andconcrete expression to the evolutionistdoctrine of descent was Buffon (1707-1788), but it is interesting to recall the factthat his contemporary Linnæus (1707-1778), protagonist of the counter-doctrine

of the fixity of species,[10] went the length

of admitting (in 1762) that new speciesmight arise by inter-crossing Buffon'sposition among the pioneers of theevolution-doctrine is weakened by hishabit of vacillating between his own

conclusions and the orthodoxy of theSorbonne, but there is no doubt that he hadfirm grasp of the general idea of

"l'enchaînment des êtres."

Erasmus Darwin (1731-1802), probablyinfluenced by Buffon, was another firmevolutionist, 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 ofanimals, as from the tadpole to the frog;secondly, the changes produced byartificial cultivation, as in the breeds ofhorses, dogs, and sheep; thirdly, thechanges produced by conditions of climateand of season, as in the sheep of warmclimates being covered with hair instead

of wool, and the hares and partridges of

northern climates becoming white inwinter: when, further, we observe thechanges of structure produced by habit, asseen especially in men of differentoccupations; or the changes produced byartificial mutilation and prenatalinfluences, as in the crossing of speciesand production of monsters; fourth, when

we observe the essential unity of plan inall warm-blooded animals,—we are led

to conclude that they have been alikeproduced from a similar livingfilament" "From thus meditating uponthe minute portion of time in which many

of the above changes have been produced,would it be too bold to imagine, in thegreat length of time since the earth began

to exist, perhaps millions of years beforethe commencement of the history of

mankind, that all warm-blooded animalshave arisen from one living filament?"

"This idea of the gradual generation of allthings seems to have been as familiar tothe ancient philosophers as to the modernones, and to have given rise to thebeautiful hieroglyphic figure of theπρω̃τον ν, or first great egg, produced

by night, that is, whose origin is involved

in obscurity, and animated by ρως, that

is, by Divine Love; from whenceproceeded all things which exist."

Lamarck (1744-1829) seems to havebecome an evolutionist independently ofErasmus Darwin's influence, though theparallelism between them is striking Heprobably owed something to Buffon, but

he developed his theory along a different

line Whatever view be held in regard tothat theory there is no doubt that Lamarckwas a thorough-going evolutionist.Professor Haeckel speaks of the

Philosophie Zoologique as "the first

connected and thoroughly logicalexposition of the theory of descent."[12]

Besides the three old masters, as we maycall them, Buffon, Erasmus Darwin, andLamarck, there were other quiteconvinced 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 EtienneGeoffroy St Hilaire, who in 1830, beforethe French Academy of Sciences, foughtwith 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 ofEvolution—who, in his eighty-first year,heard the tidings of Geoffrey St Hilaire'sdefeat with an interest which transcendedthe political anxieties of the time; and ofmany others who had gained with more orless confidence and clearness a newoutlook on Nature It will be rememberedthat Darwin refers to thirty-four more orless evolutionist authors in his HistoricalSketch, and the list might be added to.Especially when we come near to 1858 dothe numbers increase, and one of the mostremarkable, as also most independentchampions of the evolution-idea beforethat date was Herbert Spencer, who notonly 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 shakeourselves free from all creationistappreciations of Darwin, and that weshould recognise the services of pre-Darwinian evolutionists who helped tomake the time ripe, yet one cannot helpfeeling that the citation of them is apt tosuggest two fallacies It may suggest thatDarwin simply entered into the labours ofhis predecessors, whereas, as a matter offact, he knew very little about them tillafter he had been for years at work Towrite, as Samuel Butler did, "Buffonplanted, Erasmus Darwin and Lamarckwatered, but it was Mr Darwin who said

'That fruit is ripe,' and shook it into hislap" seems to us a quite misleadingversion of the facts of the case Thesecond fallacy which the historicalcitation is a little apt to suggest is that thefiliation of ideas is a simple problem Onthe contrary, the history of an idea, like thepedigree of an organism, is often veryintricate, and the evolution of theevolution-idea is bound up with the wholeprogress of the world Thus in order tointerpret Darwin's clear formulation of theidea of organic evolution and hisconvincing presentation of it, we have to

do more than go back to his immediatepredecessors, such as Buffon, ErasmusDarwin, and Lamarck; we have to inquireinto the acceptance of evolutionaryconceptions in regard to other orders of

facts, such as the earth and the solarsystem;[14] we have to realise how the

interpretation along other lines gaveconfidence to those who refused to admitthat there was any domain from whichscience could be excluded as a trespasser;

we have to take account of thedevelopment of philosophical thought, andeven of theological and religiousmovements; we should also, if we arewise enough, consider social changes Inshort, we must abandon the idea that wecan understand the history of any science

as such, without reference tocontemporary evolution in otherdepartments of activity

While there were many evolutionists

before Darwin, few of them were expertnaturalists and few were known outside asmall circle; what was of much moreimportance was that the genetic view ofNature was insinuating itself in regard toother than biological orders of facts, here

a little and there a little, and that thescientific spirit had ripened since the dayswhen Cuvier laughed Lamarck out ofcourt How was it that Darwin succeededwhere others had failed? Because, in thefirst place, he had clear visions

—"pensées de la jeunesse, executées parl'âge mûr"—which a Universitycurriculum had not made impossible,

which the Beagle voyage made vivid,

which an unrivalled British doggednessmade real—visions of the web of life, ofthe fountain of change within the organism,

of the struggle for existence and itswinnowing, and of the spreadinggenealogical tree Because, in the secondplace, he put so much grit into theverification of his visions, putting them tothe proof in an argument which is of itskind—direct demonstration being out ofthe question—quite unequalled Because,

in the third place, he broke down theopposition which the most scientific hadfelt to the seductive modal formula ofevolution by bringing forward a moreplausible theory of the process than hadbeen previously suggested Nor can oneforget, since questions of this magnitudeare 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 acquaintedwith the history of biology that the generalidea of organic evolution as expressed inthe Doctrine of Descent was quite familiar

to Darwin's grandfather and to othersbefore and after him, as we have brieflyindicated It must also be admitted thatsome of these pioneers of evolutionismdid 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 nowbriefly refer.[15]

In all biological thinking we have to workwith the categories Organism—Function

—Environment, and theories of evolutionmay be classified in relation to these To