Download DARWIN

DARWIN
AND HIS CRITICS
The Receptionof Darwin's Theory of Euoluti,on
by the ScientificCommunity
DAVID
L.. HULL
The University of ChicagoPress
Chicago and London
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The University of Chicago Press,Chicago 60637
The University of ChicagoPress,Ltd., Lon-don
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IN
APPRECIATION
TO
Virginia and Glenn D. Bouseman
@ 1973by David L. HuIl
All rights resewed. Published l97B
University of ChicagoPressedition 1983
Printed in the United Statesof America
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Iris and Robert H. Reid
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Library of Congress Cataloging in Publication
Data
Hull, David L.
Darwin and his critics.
Reprint. Originally published: Cambridge, Mass.:
Harvard University Press,1973.
Bibliography: p'
'
Includes index.
l. Darwin, Charles,1809*1882,
On the origin o{
species. 2. Darwin, Charles, 1809-1882.The descent
o[ man. 3. Evolution. I. Title.
83-4855
575.0r'62
QH365.08H84 1983
rsBN 0-226-36046-6
89 , / B50Q
Preface
produce the finished version of the von Baer paper. wayne Gailis offered
numerous. suggestionsfor improving the translation of pictet's essay.Katherine Kirkish, Dawn Klemme and Dorothy Dietrich labored to type and
retype the lengthy manuscript. This anthology was prepared under National
ScienceFoundation Grants GS-1971 and GS-3102.
Contents
D.L.H.
I
Introductory
3
16
37
Chapter I.. Introduction
.
Chapter II. The Inductive Method
Chapter III. Occult Qualities
Chapter IV. Teleology
JJ
Chapter V. Essences
ot
II
eviews
JosephDaltonHooker(1817-1911)
WilliamBenjaminCarpenter( 1813-1885)
H. G. Bronn( 1800-1862)
ThomasVemonWollaston( I 821-1Bi8 )
FrangoisJulesPictet (1809-1872)
AdamSedgwick( 1785-1873
)
RichardOwen ( 1804-1892)
SamuelHaughton( 1821-1897
)
WilliamHopkins( 1793-1866)
HenryFawcett( 1833-1884)
FrederickWollastonHutton ( I 836-1905)
FleemingJenkin ( 1833-1885)
ol
UT
87
118
126
L+2
155
1 1 1L
LI
216
229
zto
292
302
Contents
St. GeorgeJacksonMivart ( 1827_1900
) and
ChauncyWright ( 1830_t 875
)
Karl Ernstvon Baer (l7g}_l}7 6)
Louis Agassiz( 1807-1873
)
Conclusion
Bibliography
Index
J3 l
itlo
428
450
+59
+69
trntroductory
Introduction
This leads me to remark that I have always
been treated honestly by my
reviewers, passing over those without scientific
knowleirge as not worthy of
notice. My views have often been grossly misrepresented,
bitterly opposed and
ridiculed, but this has been generally done,
as I believe, i'gooä faith.Charies Darwin, Autobiography, p. l2S.
Darwin expected theologians, people untrained in scientific investigation,
and even those scientists who were strongly religious to object violently
to his theory of evolution. He had also anticipated the skepticism of even
the most dispassionate scientists. He had not Iabored over twenty years
for nothing gathering facts to support his theory and attempting to discount
those that apparently conflicted with it. But he had not anticipated the
I have got fairly sick of hostile reviews. Nevertheless,
they have been of
use in showing me when to expatiate a little
and to introduce a few new
discussions.
vehemence with which even the most respected scientists and philosophers
in his day would denounce his efforts as not being properly "scientific."
To the extent that these latter reactions were genuine and not the result
I entirely agree with you, that the difficulties on
my notions are terrific,
yet having seen what arl the Reviews have said
against me, r have far more
confidence in the generar truth of the doctrine than
r formerly had.-charres
Darwin to T. H. Huxley, Down, December 2, 1860,
Lit'e and. Letters,2:147.
of religious bigotry, they can be explained by reference to the philosophies
oT science popular in Darwin's day. In this chapter Darwin's understanding
of the philosophies of science of his day and his own. views on science
will be set out as fully as possible.
Darwin had both the good fortune and the misfortune to begin his scientific career at precisely that moment in history when philosophy of science
came into its own in England. Of course, philosophers from plato and
Aristotle had always written on epistemology and, after the scientific revolution, they were presented with the added advantage and obligation of recoriciling their philosophies with the current state of science. some of these
philosophers were also themselves scientists. But the works of Descartes,
Locke, Hume, Berkeley, Leibnitz, and Kant do not exhibit the same concern
with the accomplishments of science and the nature of the .,scientific
method" which has come to characterize philosophy of science.l
i. I an not want to exaggeratethe differencebetweenepistemologyand philosophy
of science.I have no serious quarrel with those who want to identify the rwo,
as doesGerd Buchdahl(1969). However,r am primarily interesredin thl reception
of-evolutionarytheory by scientistsin the niniteenth century. For this pr.ior.,
I have chosento narrow the focus of my discussionto those areas of epistem"togy
which seem most closely connected to the scientific enterprisc.
Introduction
Darwin and His Critics
Commencing with John Herschel's Preliminary Discourse on tha Study
of Natural Philosoplty (1830), English-speaking scientistsbecame self-conscious about the proper method of doing science. During the years
1837-1842, when Darwin was residing in London and rvorking on the species
problem, the great debate on the philosophy of science erupted between
William Whewell (1794*1866) and John Stuart Mill (1806-1873). In 1833
Whewell contributed his Astronomy and General Physics Considered witlt
reference to Natural Theology to the Bridgewater Treatises. In 1837 he
published his History of the Inductiue Sciencesand in 1840 The Philosophy
of Inductiue Sciences,Founded upon their History. Darwin was impressed
by the breadth of l<nowledgeexhibited in these five volumes and remembered Whewell as one of the best converserson srave subiects to whorn
he had ever listened.2
In 1843 Mill brought out his influential System of Logic, Ratiocinatiue
and Inductiue, Being a Connected Vieut of the Principles of Euidence,
and the Methods of Scientific Inuestigation. Although Mill had gathered
most of what he knew of science lrom reading Whewell's volumes, his
System of Logic was largely an empiricist attack on Whewell's reworking
of Kant's rationalist philosophy. The key word in this dispute and in the
methodological objections raised to Darwin's theory was "induction." It
would be nice to be able to set out at this point the meaning which the
disputants attached to this word, but I cannot. Everyone meant sornething
different by it, and in the .works of a single man, one is likely to find
many different uses of the word. Initially it was used by Francis Bacon
(1561-1626) to contrast his abortive "inductive method" with the Aristotelian "deductive method." As popularly misconceived, the deductive
method consistedin an irresponsible leap to a conclusion of high generality
and the subsequentdeduction of consequencesof these generalizations regardless of observedfacts. Perhaps the scholasticsat their worst were guilty
of such maneuvers, but the above characterization was not only a parody
of Aristotle but also fails to identify the actual weaknessesin Aristotle's
system. The inductive method, also as popularly misconceived, began with
observation and proceeded by the cautious construction of generalizations
of greater and greater generality. The deductive method proceeded from
the peak of the pyramid of knowledge down to its base, whereas the inductive method started at the base and worked up. The superiority of a pyramid
resting on its baserather than its peak was obvious.
Although Bacon carne close to advocating the inductive method as set
2 . D a r w i n ( 1 9 5 8 ) ,p . 6 6 .
out above, Flerschel, Whewell, and Mill were all alvare of its shortcomings.
Science had not and could not proceed by the method set out by Bacon.
Yet Bacon was the patron saint of the scientific revolution, and "inductive"
was an honorific title not to be discarded' lightly' Al1 three men wanted
to reservethe term "induction" for the processby which scientific knowledge.
is attained. Simultaneously they also wanted to use it to refer to the means
by which such knowledge was proved {actual. For Herschel and Mill induction was the discovery of empirical laws in the facts, reasoning from the
known to the unknown. Concurrently, this inductive method insured the
truth of these laws. For Whewell, induction was the superinducing of conto
cepts o11the facts by the mind. Experience might stimulate the mind
form a concept, but once the appropriate concept had been conceived,
truth was guaranteed. For Herschel and Mill, both Kepler's laws and the
parallel line postulate of Euclidean geometry were inductions from experience; for whewell they were self-evident truths whose truth could be known
a priori.
Induc'
Whe*eli did pot reply to Mill for six years, then published his Ol
tion,wit'hEspecialReferencetoMr.'!.StuartMill'sSystemofLogic
(1849), just in time for the third eclition of Mill's System of Logic''Ihe
because
controversy which ensued was gradually decided in Mill's favor, nct
because
but
Whewell,
of
that
to
superior
especialiy
was
position
Mill's
emwhewell,s version of I(antian philosophy ran contrary to the rising
scientific
over
this
controversy
of
midst
the
in
It
was
tirne.
the
piricism of
method that Darwin published his On the Origin of Species by Means
ol Natural selection, or tlte Preseruation of Fauoured Races in the struggle
coincidence was' to say the least, a
for Life (1859). For Darwin, this
mixed blessing.
which,
In his last year at cambridge, Darwin read I{erschel',sDiscourse
burnhim"a
in
stirred
(1818),
Narratiue
Personal
along with I{umboldt,s
structure
noble
the
to
contribution
humble
most
ing zeal to add even the
this
of Natural Science."3 Herschel had written his book to eticit precisely
revolution.
scientific
the
about
had
brought
reaction in his readers. Newton
of Newton's
Henceforth, all scientists had to do was to filI in the details
the Newwithin
always
but
it,
great structure, perhaps expanding upon
reiigion'
and
science
between
tonian framework. Nor was there any conflict
scientists
but
the
Bible,
o{
Geology had challenged the literal interpretation
themselves
and theologians had made their peace. scientists could concern
the
first crebut
with the workings of the material world, once created,
3 . D a r w i n ( 1 9 5 8 ) ,p . 6 7 .
Darwin and His Critics
Introduction
ation, 'life, mind and soul were the province of the theologian. "To
ascend to the origin of things, and to speculate on the creation, is not
the businessof the natural philosopher."a Not only were scientistsmaliing
but he was not prepared for the criticism which his methodology was to
receive from the most respected philosophers and scientistsof his day. Most
contemporary commentators tend to dismiss these criticisms as facile, disingenuous and superficial, suspectingthat they stemmed more from a distaste
of the content of Darwin's theory than from his methodology, but this
dismissal is itself too facile. Certainly the repeated invocation of the
great contributions to the noble edifice of science and to mankind by
applications of science in medicine and industry, but their discoveriesalso
lent support to religion through natural theology. As they discovered more
clearly how nature worked, they showed how great the creator's wisdom
had been. In his youth Darwin had hoped to join in this great parade
of scientists and men of God marching arm in arm to produce a better
world. Instead he stopped it dead in its tracks.
In his early publications, Darwin gave every appearance of contributing
his share to received science. His journals concerning the voyage of the
Beagle were in the best tradition of such narratives. FIis monographs on
living and fossil barnacles certainly were in no way controversial. Even
the publication of his papers on the formation of the Parallel Roads of
Glen Roy (1839) and of coral reefs (1842), though theoretical in nature,
did not detract lrom ]ris growing reputation as a true inductive scientist.
In the first, he expiained the appearance of a series of parallel shelveson
the sides of a glen in Scotland in terms of the gradual elevation of the
land. The parallei roads were actually the remnants of former beaches.
In the second, he explained the forrnation of coral reefs in terms of the
gradual subsidence of the ocean floor. New coral grew on the old as it
feii beneath the surface of the warer. But with the publication of the Origin
oI Species,large segments of the scientific and intellectual community,
turned on him. Both Adam Sedgwick, the eminent geologist, and Richard
Owen, the leading comparative anatomist of the day, had encouraged Darwin in his early work. After the Origin, their praise turned to ridicule.
Sedgwick (1860) complained that Darwin had "departed from the true
inductive track." Owen, while admitting that he himself had casually entertained the notion of natural selection,had judiciously refrained from enunciating it. It was "just one of those obvious possibilities that might float
through the imagination of any speculative naturalist; only the sober
searcher after truth would prefer a blamelesssilence to sending the proposition forth as explanatory of the origin of species, without its inductive
foundations."s
Darwin was prepared for the abuse which the content of his theory,
especially its implications for man, was to receive from certain quarters,
4. Herschel(1830),p. 38.
5. Owen (1860).
Baconian method by many of Darwin's critics and even by Darwin himself
indicated no great understanding of the actual nature of this method or
the philosophy from which it stemmed, but the leading philosophers contemporary with Darwin, John Herschel, William Whewell, and John Stuart
Miil, were equally adamant in their conviction that the Origin of Species
was just one mass of conjecture. Darwin had proved nothing! From a
philosophical point of view, evolutionary theory was sorely deficient. Even
today, both Darwin's original efforts .and more recent reformulations are
repeatedly found philosophically objectionable.GEvolutionary theory seems
capable of offending almost everyone.
In the nineteenth centur-y, "to be scientific" meant to be like John
I-Ierschel'sextension of physical astronomy to the sidereal legions.T Thus,
Darwin was especially anxious to heal the opinion of Herschel, the "great
philosopher" referred to in the opening paragraph ol the Origin He sent
Herschel a copy of his bool< and wrote to Lyell to pass on any comments
which the great physicist might make since "I should excessivelylike to
hear whether I produce any effect on.such a mind."8 Herschel's opinion
was rapidly forthcoming. Darwin wrote to Lyell, "I have heard, by a roundabout channel, that Herschel saysmy book 'is the law of higgeldy-piggeldy.'
What this exactly means I do not know, but it is evidently very contemptuous. If true this is a great blow and discouragement."e In the face of
such a rejection by the most eminent philosopher-scientist of the century,
it is easy to understand Darwin's pleasure when he discovered in an equally
roundabout way that another great philosopher, John Stuart Mill, thought
that his reasoning ln the Origin was "in the most exact accordance with
the strict principles of logic."lo On closer examination, however, Mil.l's
6. See,for example,Woodger(1929), Kneale (1949), von Bertalantry(1952),
Grene (1958), Himmelfarb(1959), Manser (1965), and Mooreheadand Kaplan
(1e67).
7 . C a n n o n( 1 9 6 1 ) ,p . 2 3 8 .
8. Darwin,November
23, 1859,Lif e andLetters(1887),2:26.
9. Darwin,December
12, 1859,ibid., 2:37.
10. Darwin,HenryFawcettto C. Darwin,January16, 1861,More Letters(1903),
1:189.
Dalwin and His Critics
endorsement can be seen to be not nearly reassuring. Darwin had prop_
erly used the Method of Hypothesis, but this rnethod belonged to the logic
of discovery, not proof. In spite of twenty years' labor, Darwin hacl failed
to provide proof for his theory of evolution by natural selection.
Darwin's own views on the nature of science exhibited the conflicts and
inconsistenciestypical of his day. He evidencecl the usual distrust of ,,hypotheses" while grudgingly admitting their necessity. For example, in a
letter to I{ooker, Darwin claimed that he looked upon "a strong tendency
to generalize as an entire evil"11 and yet admitted in his Autobiography:
"f cannot resist fo'ning one on every subject.,'l2 In the opening paragraph
of the Origin of SpeciesDarwin sketched the following history of the development of his theory:
When on board H.M.S. "Beagle," as naturalist, I was much struck
with certain facts in the distribution of the inhabitants of south America,
and_in the geological relations of the present to the past inhabitants
of that continent. These facts seemed to me to throw some lieht on
the origin of species-that mystery of mysteries, as it has been called
by one of our greatest philosophers. On my return home, it occurred
to me, in 1837, that something might perhaps be made out on this ques_
tion by patiently accumulating and reflecting on all sorts of facts wirich
could possibly have any bearing on it. Afte; five years, work I allowed
myself to speculate on the subject, and drew up some short notes; these
I enlarged in lB44 into a sketch of the concluiions, which then seemecl
to me probable: from that period to the present day I have steadily
pursuedthe sameobject (p. 1).
rn his Autobiography Darwin recalls roughly this same sequenceof events
but adds that he "worked on true Baconian principles and without a'y
theory collected facts on a wholesale scale."t3 But Darwin was well aware
that the possibility of speciesevolving had occurred to him soon after his
return from his voyage on the Beagte (if not before) and his principle
of natural selection not much later, in october 1838. Five years may have
elapsed before he permitted himself to write an essayon the subject, but
he had speculated and collected facts in the iight of these speculations
from the very first.
The source of this fabricatio' is easy to uncover. one of the most prevalent confusions in the work of even the best scientists and philosophers
was between the temporal order of an actual scientific investigation and
1l. Darwin, January11, 1844,More Letters( 1903) , 1: 39.
1 2 . D a r w i n ( 1 9 5 8 ) ,p . 1 a l .
1 3 . D a m i n ( 1 9 5 S ) ,p . 1 1 9 .
Introduction
the logical order of a reconstruction of scientific method. According to
empiricist epistemology,all knowledge has its foundation in experience. This
tenet was mistakenly taken to imply that a1l scientific investigation has
to begin with observation. The true inductive scientist began collecting
data indiscriminately, with no preconceived ideas, and gradually evolved
broader and broader generalizations.The process of scientific investigation
assured both the truth and the empirical meaningfulness of the resultant
propositions. Deductivists approached nature with a hypothesis already in
mind, and speculators flew too quickly to generalizations of too great a
scope. Thus, Darwin can be found saying of his coral reef paper, 'oNo
other worl< of mine was begun in so deductive a spirit as this; for the
whole theory was thought out on the west coast of S. America before
I had seen a rue coral reef."lo Similarly with respect to his theory of
evolution, he conceded to Asa Gray, "What you hint at generally is very,
very true: that my work will be grieiriously hypothetical, and large parts
by no means worthy of being called induction, my commonest error being
probably induction from too few facts."15
In a letter to FIenry Fawcett, however, Darwin indicated that he realized
that data cannot be gathered efficiently without some hypothesis in mind:
About thirty years ago there was much talk that geologistsought only
observe and not to theorize; and I well remember someone saying
that at this rate a man might as well go into a gravel-pit and count
the pebbles and describe the colours. FIow odd it is that anyone should
not see that all observation must be for or aeainst some view if it is
to be of any service!t6
"to
What mattered was that the hypothesis be an empirical hypothesis, one
that could be verified or refuted by observation, and that serious attemPts
be made to gather the relevant data. Immediately after saying that his
coral reef paper was begun in a deductive manner, Darwin adds, "I had
therefore only to verify and extend my views by a careful examination
of coral reefs."l7 Darwin's own experience as a scientist forced him to
recognize that the order in which hypotheseswere formed and the relevant
data gathered was not rigidly set. It helped to have a hypothesis in mind,
but hypotheses had to be changed as the investigation proceeded.ls His
theory of the formation of coral reefs was formulated before he had collected
14. Ibid.,p. 98.
1 5 . D a r w i n ,N o v e m b e2r 9 , 1 8 5 9M
, o r e L e t t e r s( 1 9 0 3 ) ,1 : 1 2 6 .
18, 1861,ibid., l:195.
16. Darwin,September
1 7 . D a r w i n ( 1 9 5 8 ) ,p . 9 8 .
i B . I b i d . ,p . 1 4 i .
t0
Dalwin and His Critics
very much of the relevant data and turned out to be largely factual. I{is
theory of evolution by natural selection was formulated after several years
of observationsas a naturalist, followed by two decadesof additional, selective investigation, and it too was basically correct. I{is theory of the Parallel
Roads of Glen Roy had much the same history on a smailer scale as his
theory of evolution, but was mistaken. In the case of inheritance, Darwin
actually did amass facts wholesale before he succeeded in working out
his theory of pangenesis. Its {ate was even more unhappy than that of
the Parallel Roads theory. Clearly there was no connection between the
Introduction
1l
chided him for objecting to the skepticism of scientific men. "You would
not fulminate quite so much if you had had so many wild-goose chases
after facts stated by men not trained in scientific accuracy."2o
Darwin's conservative views on publication were rewarded to some degree. His Origin ot' Species did not suffer the same fate as those works
on evolution that had preceded it. It was treatecl as a serious work of
science even by those who denounced it. But a similar reticence on the
part of Gregor Mendel resulted in his laws of heredity being overlooked
for almost forty years. Mendel published his laws in 1865, soon after the
temporal order of fact-gathering and hypothesizing and the truth of the
hypothesis.
appearance of the Origin He too wanted to avoid being branded a speculator. In his original paper he barely alludes to his unobservable "factors,"
Ilowever, Darwin did think that the temporal order of the verification
and the publishing of a hypothesiswas important in the sociology of science,
though the cogency of his entire argument rested upon their existence.
In a letter to Carl Nägeli (X{endel, 1867), he claimed that, "as an empirical
lvorker" he had to "define constancy of type as the retention of a character
during the period of observation." Pärhaps Darwin's advice might protect
both for the sal<eof the scientist's own reputation and for the, sake of
the acceptanceof his theory by the scientific community. To a young scientist, Darwin advised, "I would suggest to you the advantage, at present,
of being very sparing in introducing theory in your papers (I formerly erred
much in Geology in that way) ; Iet theory guide your obseruations, brt
scientists from being engulfed in half-baked scientific publications, but it
also contributed to the obscurity of Mendel's potentially great contribution
to science. Because l-amarck neglected the niceties oJ the sociology of sci-
till your reputation is well established, be sparing of publishing theory.
It makespersonsdoubt your observations.'l1e
ence, his worl< was ignored with disdainful embarrassment.Because Mendel
was too scrupulous in observing them, his work was overlooked. Darwin
Darwin also had a reason for advising restraint in publication which
was less personal and more significant to the progress of science. I{e was
aware of the fate of Lamarck and Chambers. Chambers had. received con-
strucl<an appropriate compromise.
Darwin's beliefs on the ethics of pubiication go a great way toward
explaining his reticence in publishing his own views on the origin of species
until his big book was complete. Darwin emphasized the importance of
providing empirical evidence for scientific hypothesesfor still another rea-
siderable popular acclaim but scathing denunciation from the academic
community, including T. H. Huxley (1854). Lamarck received norhing
but ridicule lrom all sides. Dar-win criticized Larrar-ck and Chambers, nor
for suggestingmechanisms for evolution which he thought were mistaken,
but for foisting their views on the scientific community without sufficient
effort at careful formulation and verification. Lamarck and chambers
looked upon the process of scierrtific verification as a very casual affair.
Darwin looked upon these matters as of utmost g.avity. Lamarck published
radically new theories in a variety of fields as diverse as mineralogy and
meteorology.He felt that the originality of his impressionisticsketcheswould
be enough to rnotivate others to undertake the subordinate task of filling
out and verifying his theories. As Burkhardt (1970) has aptly observed,
public neglect and private ridicule were the late of his theories. prior ro
knowing that chambers was the author of the vestiges of creation, Darwin
19. Darwin, 1863,More Letters(1g03),2:323.
son. The science of Darwin's day was filled with metaphysical principles
enunciated as if they were scientific laws. Darwin found Flerbert Spencer
to be one of the chief offenders in this regard. Because of the jargon of
the period, Darwin's discussionsof the differences between scientific laws,
the axioms of mathematics, and metaphysical principles are ltone too clear,
but in these matters he was no worse than the leading empiricist phiiosophers of the day. He tended to distinguish the forrnal from the empirical
sciencesby the prevalence of deductive reasoning in the for"mer. Of Spencer,
Darwin complained:
His deductive manner of treating any subject is wholly opposed to
my frame of mind. I{is conclusions never convince me; and over and
over again I have said to myself, after reading one of his discussions,20. Darwin,April 30, 1861,More Letters(1903),2:443;seealso,Darwin (1871),
p. 606.
12
Darwin and His Critics
"Here would be a fine subject for half-a-dozen years' work." Ilis fundamentai generalizations (which have been compared in importance by
some personswith Newton's Laws ! ) which I daresaymay be very valuable
under a philosophical point of view, are of such a nature that they
do not seem to me to be of any strictly scientific use. They partal<e
more of the nature of definitions than of laws of nature. They do not
aid me in predicting what will happen in any particular case. Anyhow
they have not been of any use to me.21
The distinction w}rich Darwin discerned in the works of Spencer was
between a scientific hypothesiswhich has not yet been verified and a purely
metaphysical principle which, by the methods of science, cannot be confronted by empirical data at all. FIe felt "inclined to cavil at speculation
when the direct and immediate effect of a cause in question cannot be
shown."2: Darwin doubted the merits of Spencer's scientific work, not
merely because the evidential basis was frequently lacking but because
Darwin doubted that there was any.
Although Darwin envied mathematicians their "sixth sense,"he also mistrusted them. For example, in the sixth edition of. the Origin, he had
to change the number of descendantsof a single pair of elephants which
would still be alive after 750 years from 15 million to 19 million. "I got
some mathematician to make the calculation. and he blundered and caused
me much shame."2sAgain to Hool<er, he remarked, "You will be amused
to observe that geologistshave all been misled by Playfair, who was misled
by two of the greatest mathematicians! And there äre other such cases;
so we could turn round and show your reviewer how cautious geologists
ought to be trusting mathematicians."2a
Darwin could not help but know the crucial role which mathematics
had played in physics, since Hersihel had repeatedly emphasized it in his
Discourse,.but it did not seem to be in the least useful in his own work
in biology. On occasion he had to make some simple computations. When
these proved too much for l.rim, he asked for help. In later life his son
Francis took over this duty. What seemed to bother Darwin was that the
kind of mathematical techniques he needed most were not available. For
Darwin, mathematics consisted of deductive reasouing, and he distrusted
greatly "deductive reasoning in the mixed sciences." In his own work,
21. Darwin (1958), p. 109; seealsoletter to J. Fiske,December8, 1874,Life
a n d L e t t e r s( 1 8 8 7 ) , 2 : 3 7 1 .
22. Darwin,March4, 1850,More Letters(1903),2:133.
23. Darwin,April 15, 1872,ibid.,1:336.
24. J)arwin,August7, 1869,More Letters(1903),l:315.
Intloduction
IJ
he seldom was presented with a situation in which he could use such deductive reasoning. He .was constantly forced to deal in probabilities, and no
one could tell him how to compute and combine such probabilities. I{e
agreed with Lyel1 about "mathematicians not being better able to judge
of probabiiities than other men of common-sense."?sDarwin tended to _.
extend his view of mathematicians to ph;,sicists,especially in their attempts
to calculate tl-reage of the earth. They had been wrong in their geological
calculations so many times in the past, Darwin was not overly terrified
by the specter of Lord Iielvin's estimation of the age of the earth.26
One reason which Darwin frequently gave for the Origin's being so
maligned and misunderstood was that Wallace's joirrt discovery had forced
him into premature publication. No similar pressure forced Darwin to publish his theory of pangenesis,and it met with even more resistance than
lhe Origin had. In reality, all of Darwin's theoretical work had much
the same structure. As Darwin put it: "The line of argument often pursued
throughout my theory is to establish a point as a probability by induction
and to apply it as hypotheses to other parts and see whether it will solve
them."2? If it did solve them, then Darwin thought- that there was good
reason to accept the hypotheses tentatively. As Darwin wrote of F. W.
I{utton's review of the Origin:
He is one of the very few who see that the change of species cannot
be directly proved, and that the doctrine must sink or swim according
as.it groups and explains phenomena. It is really curious how few judge
it in this way, which is clearly the right way.28
And in his autobiography he saysof his theory of par.rgenesis:
Towards the end of the work I give my well-abused hypothesis of
pangenesis.An unverified hypothesis is of little or no value. But if anyone
should hereafter be led to make observations by which some such hypothesis could be established,I shall have done good service, as an astonishing number of isolated facts can thus be connected together and rendered intelligible.20
Darwin produced several theoretical works in his career: two were in
error (pangenesisand his explanation of the Parallel Roads of Glen Roy)
25. Dar-win,June 17, 1860, ibid., 1:154. For severalamusinganecdotesabout
Darwin's mathematical ineptness see Himmelfarb (1959).
26: For a further discussion see the comments to the reviews of Haughton and
Fawcett.
27. DeBeer (1960), 3:142.
2 8 . D a r w i n , A p r i l 2 3 , | B G L ,L i f e a n d L e t t e r s ( 1 8 8 7) , 2 : 1 5 5 .
29. Darwin (1958), p. 120.
15
Darwin and I-Iis Clitics
Intloduction
and two correct (evolutionary theory and his explanation of the formation
of coral reefs).30His procedures in formulating. articulating, and verifying
these theories and explar-rationswere roughly the same, yet no one com-
book that scientifrc revolutions are so traumatic that no reasons can be
given for preferring one theory to another. Either one accepts the old
theoly and its standards of rneaningfulness and truth or the new theory
and its differing standards. The transition is almost mystical. Needless to
say, considerable controversy has followed upon l{uhn's reconstruction of
14
plained of the methodology of l.risGlen Roy or coral reefs papers. If Darwin's methodology was faulty in the Origin, then it should have been equally
faulty in all of his scientific works.
What was wrong with Darwin's theories? Was his methodology faulty?
What is the nature of inductive formulation and proof which eluded Darwin? These are the questions which occur to the modern reader when
first confronted by the reviews of the Origin of Speciesand Darwin's later
work, especially the Descent of Man. Some of the reviewers were obviously
biased. Some were merely mouthing undigested platitudes. But many of
the reviewers were competent scientistshonestly trying to evaluate a novel
theory against tl-re commonly accepted standards o{ scientific excellence,
and evolutionary theory consistently came up wanting. The solution to
these puzzles can be found ir-r the philosophies of science promulgated by
such philosophersas I{erschel, Whewell, and Mill and their most important
predecessors,Aristotle, Bacon, and Newton. Darwin was caught in the rniddle of a great debate over some of the most fundamental issues in the
philosophy of science-the difference between deduction and induction and
the role of each in science, the difference between concept formation and
the discovery of scientific laws, the lelation between the logic of discovery
and the logic of justification, the nature of mathematical axioms and their
relation to experience, the distinction between occult qualities and theoretical entities, and the role of God's direct intervention in nature. Before
philosophers of science had thoroughly sorted out these issues,they were
presented with an original and highly probiematic scientific theory to evaluate. That they rejected evolutionary theory, a theory which has outlasted
many of the theories judged to be exemplars of scientific method, says
something about the views of science held by these philosophers and
scientists.
In the succeedingchapters, the interconnections between Darwin's theory
of evolution and the philosophiesof scienceculrent in his day will be traced.
It is hoped that this discussion will aid the reader in understanding the
various criticisms in the ensuing reviews and in placing them in their appropriate conceptual setting, I(uhn (1962) has argued in his influential
30. For a discussionof some of Darwin's other scientifictheoriessee Ghiselin
(1969).
scientific revolutions as fundamentally arational processes.llowever, all of'
the discussions in this dispute have centered on revolutions in physical
theory. The revolutions in biology have been al1 but ignored.3l The essays
in this anthology should provide arnple source material for the disputants
on the valious sidesof this controversy.
In Chapter 2 the logic of justification ar.rd its relation to discovery will
be examined. What did it take ro proue a scientific theory? Why had
Newton's theory supposedly fulfilled the requirements of proof while Darwin's failed? In Chapter 3 the problems,surrounding concept formation
and meaning will be discussed.Early scientists were deeply impressed bv
the failure of Aristotelian science in the hands of the Scholastics. They
identified this failure rvitl'r the "deductive method" and with the central
role of "occult qualities" in ear'ly scientific theories. The fear of occult
qualities was so strong in many scientiststhat any reference to unobservables
was looked upon with extreme suspicion.But coexisting with this hard-nosed
empiricism was an equally strong belief in God as an underlying first cause
and his occasional dilect intervention in natural processes.This schizophrenic attitude of scientistsproved to be one of the strongest impediments
to the acceptance of evolutionary theory. As I(uhn (1962) has observed:
"For many men the abolition of that teleological kind of evolution was the
most significant and least palatable of Darwin's suggestions.The Origin
of Speciesrecognizedno goal set either by God or nature" (p. 171).
Chapter 4 will deal with the effect that essentialismhad on the acceptance
of evolutionary theory. Although this topic has been discussedextensively
elsewhereseit is too intimately connected with the problems at issue to
allow omission..Seldom in the history of ideas has a scientific theory conflicted so openly with a metaphysical principle as did evolutionary theory
with the doctrine of the immutability of species.s3
3 1 . S e eR u s e( 1 9 7 0a n d 1 9 7 1 ) ,G r e e n e( 1 9 7 1 ) ,a n d G h i s e l i n( 1 9 7 1 ) .
3 2 . M a y r ( 1 9 5 9 a )a n d H u l l ( 1 9 6 5) .
33. The following works are recommended for further reading in the philosophies
of Aristotle, ßacon, llerschel, Whewell and Mill : Blunt (1903), Ducasse (1951
and 1960), Anschutz (1953), Heathcote (1953), Hochberg (1953), Strong (1955),
Cannon (1961), Walsh (i962), Grene (1963), and Butts (1968).
fhe Inductive Method
t7
with those of their principles. But this was not the natural history and
experience that was wanted; far from it.t
2 ' The Inductive Method
rn the light of the great advances in physics in the seventeenth and
eighteenth centuries, nineteenth-century philosophers ancl scientistscollaborated to produce a philosophy of scienceconsistentwith these achievements.
In their informal remarl<s these authors tended to provide useful insights
into the scientific enterprise, but when they tried to be rigorous in their
characterization of the scientific method, they tended to make pronouncements which frustrated the rational evaluation of ner.vlyemerging scientific
theories, specifically evolutionary theory. In this chapter, the philosophies
of scienceof Aristotle, Bacon, Herschel, whewell, and Mill will be sketched,
both as these men set them out and as they r.verepopularly misconceived.
It will be argued that evolutionary theory did fail to meet the standards
of proof established by these philosophers for the simple reason that no
theory could possibly fulfill them, including the prrysical theories which
theseauthors had chosenas paradigm.
In Darwin's day Aristotle was lool<ed upon by scientists as the author
of infinite error and Bacon as the man who fashio'ed the method which
Newton was to use to unlock the mysteriesof the universe. Bacon's characterization of ancient pl-rilosopherswas typical:
From a few examples and particulars (with the addition of common
notions and perhaps of some portion of tl-re received opinions which
have been_most popular) they flerv at once to the most g".r".ul conclu_
sions,.or first principles of science. Taking the trutrr of tl-reseas
fixed
and
they proceeded by means-of intermediate propositions
.immovable,
to educe and p.ove from them the inferior conclusions; and äut'of these
they framed the art. After that, if any new particulars and examples
rep.u.gnanjto their dogmas were mooted and adduced, either they
sultly
molded them into their system by distinctions ancl explanations of their
ryle3, or else coarsely got rid of them by exceptions; *frlt" to
such par_
ticulars as were not repugnant they labored to issign causesin co.rformiry
As far as Aristotle's professed epistemology is concerned, Bacon's characterization is anything but fair, though it accurately depicts the level to
which it frequently sank in actual practice. IJowever, in singling out Aris--.
totle's emphasis on deduction at the expense of induction, Bacon failed
to identify the most significant source of error in Alistotle's epistemology.
In fact, deduction will continue to play a central role in scientific procedures
tlrroughout the history of science.The real culprits are the quest for absolute
certainty in the acquisition of knowledge and Aristotle's use of intuition
to accomplish this end. Future philosophers of science like Bacon, Flerschel,
and Mill will join Aristotle in his quest for absolute certainty but will
attempt to obtain it by a strict application of inductive logic.
Confusion over the nature of deQuction and induction is one of the
most conspicuous features in attempts to set out a philosophy of science
from Aristotle to John Stuart Mill. The metaphor that permeates the literature is that of a pyramid. For example, Adam Sedgwick (1860) complains
of Darwin's theory:
But I must in the first place observe that Darwin's theory is not induc-tiue,-rrot based on a series of acknowledged facts.pointing to a general
conclusion,-not a proposition evolved out of facts, logically, and of
course including them. To use an old figure, I look on the theory as
a vast pyramid resting on its apex, and that apex a mathematical point.
Deduction proceeded from the most general propositions at the apex
of the pyramid to the particulars at the bottom, induction from particulars
to generalizationsof broader and broader scope. A more misleading metaphor is hard to imagine. It is inapplicable to Aristotelian iogic. Both
Whewell and Mill were well aware that it was inapplicable to logical inferences as they viewed thern. Yet the metaphor persisted, and has done so
to this day in spite of the efforts of generations of iogic plofessors. The
pyramid which people have in mind when they contrast deduction with
induction is not a pyramid of inferences but a pyramid of concepts like
the Linnaean hierarchy.' At the peak of such a pyramid is the ciass of
greatest generality, e.g., animals. Animals are divided into additional classes
of reduced scope, e.g., protozoans, round worms, and chordates. Each of
these classesis subdivided in turn until the lowest level is reached-species,
1. Bacon(1620);bk. I- AphorismCXXV.
2. For example,seeJ. J. Bakerand G. Allen ( 1968).
l9
Darwin ar-rd FIis Critics
rlre Inductive Method
subspecies,ol valieties. At the bottom of the pyramid are arrayed individual
organisms.
When we turn to a consideraiton of statements of greater and greater
generality and inferences among thern, the whole idea of descending and
ascending in a pyramid ceasesto be appropriate. For example, the following
Hcrc lhe increase in generality is obvious. The conclusion is more general
tbiLn the premises taken separately or together. But there has been no
lscent in the pyramid of concepts. Crows and blackness are rnentioned
in all the constituent statements. To use such an inductive argument one
rnust alleady l<now how to recognize crows and the color black.
.fhe rnrportant difference between deduction and induction which has
1B
hypothetical syllogism is the classic example of an Aristotelian deductive
arsument:
(1)
cmergecltlrrough the years turns out to concern not generality but certainty.
In a valid deductive argument, the conclusion follows necessarily from
the prernises.If the premisesare true and the argument valid, the conclusion
rnusl be tlue. Both arguments (1) and (2) are deductive in this sense.
All hairy quadr-upedsare animals.
All hor"sesare hairy quadrupeds.
I-Ience, all horses are animals.
Although
the
inference
in hairy
the
from
the premises to
quadmpeds,
conclusion
and hairy
the conclusion.
quadrupeds
is no less general
than
Ilorses
are included
either
are included
in animals,
of the premises. It
but
retains
leference to the class of smallest scope (horses.) and largest scope (animals).
Only
the middle
the individual,
term
In an inductive argument, the conclusion follows from the premises, if
at all, rvith only a certain degree of probability. If the premises ere true
anrl the argument warrantedr then the conclusion is probably true. fn an
inductive argument there is always the possibility that true premises will
is deductive, no dccrease in generality accompanies
this argument
has dropped
out. Even
no decrease in generality
when
accompanies
the deduction
is to
the inference
from
the premises to thc conclusion:
(2)
All men are rnortals.
Socratesis a manI{ence, Socrates is a mortal.
Once again, the conclusion contains reference to the class of greatest
generality. One has not descendedin any pyrarnid of inferences. The story
is somewhat different for induction. The paradigrn exampie of an inductive
inference is induction by simple enumeration. In such inferences, one reasons from a series of singular statements about individuals to a universal
o c n e r a l i*^'"*-"^'
zrfnn'
'
ö.-_'''
(3)
This crow is black.
f'
',i
it,
ir.i
l't
-ff,
i...
fi
l:r
I$ :
lead to a false conclusion. For examirle, in argument (3) it turns out
that not all crows are black (nor all ravens; nor are all swans white).
It is casy to shorv that the difference between deductive and inductive
aryuments does not depend on any putative decreaseor increase in generalitv betiveen premisesand .conclusions.For example, the following argument
is analogousto the deductive argument (2), yet it is inductive. It is inductir.+ becausethe conclusion does not follow necessarilvfrom the nremises:
(4)
[:\:
Almost all swans are white.
The Brookfield Zoo owns three swans.
'h,i
I{ence, they are probably white.
$r'
&,ir.
$ll"i:
ii"
$i
$:'
N.
Sirr
$.,,
s\
In the ensuing discussionof the philosophies of Aristotle, Bacon, Flerschel,
Whnyell, and Mill, we will use "cleduction" and "induction" in the modern
scnscof demonstrative and nondemonstrative inference. Our anachronistic
usaqeproducesless distortion than one might think, sirrce ali the arguments
This crow is black.
$r n'hich these philosophers considered deductive are also deductive in this
.$|.r',
This crow is black.
g:'i:
This crow is black.
ti'
li'
f-li''
li.
ir
J,,
$,.,
i.,
$ystcrnsof logic now are included in one group or" the other. Even the
difference .ir-rlat.ionale does not introduce any change in ernphasis, since
one oI the chief concerns of philosophers from Aristotle to Mill was to
ii
evade lhe urrcertainty inherent in inductive inferences. Ilacon, Flerschel,
f'
.$
.,
Hence, all crows are black.
modern senseand all those that were thought inductive remain inductive.
'i'he difference betvveen the two usages stems from the rationale used to
nräke the clistinction and from the fact that certain types of inferences
rr'hich cr:unted as neither deductions nor inductions in some of the earlier
|.l
f,
.f;
l
I
20
Darwin and FIis Critics
rhe Inductive Method
attempt to eliminate it by trying to make inductive inferences
more rigorous, Aristotle by recourse to intuition, and whervell bv reference
to self-evident truth.
small induction,s but as Aristotle's own efforts and those of his followers
give ample proof, these precautions tend to be ignored in an epistemology
based on the infallible intuition of immutable essences.The source of error
in Aristotle's epistemology is not the deductive organization of hnowledge.
After all, verification by the deduction of observational consequencesis
one of the best ways of checking the truth of a scientific law, but deduction
to the individual as exemplified in argument (2) has no place in Aristotelian
and Mill
For Aristotle, k'owledge began with the observation of individuars rike
Callias, Socrates,Alcibiades, and Ajax and proceeded by simple enumeration until one intuited that which is universal in .them-their essence,or
formal cause. This process of concept formation preceded any inductive
inferences in the strict sense,since it preceded the formation of statements.
It cannot be represented as in argument (3), since in this argument one
already has the concepts, crow and black. one merery observesindividuals
and intuits their essence.For example, one might intuit that all the inclividuals listed above were men, or human beings, or animals. Intuition
need not begin with the lowest universal and proceed only iater to universals
of higher generality. It is possible to observe only one member of one
speciesof a universal of high generality and still correctly intuit that universal. usually more extensive observations are necessary.The number and
variety of observations needed for intuition vary from person to person
and from subject mattel' to subject matter. Fewer observations are usually
necessaryin mathematics than in such empirical sciencesas biology. Nor
did Aristotle think that the preceding enumeration of individuals could
be complete, since he believed that there were indefinitely rnany individuals
in any species. It is not possible to observe all human beings and then
merely by mechanically summing. their properties to discover their.essenceIntuition was necessary.
Little has been said thus far about intuition. There is very little to say.
Although intuition is the source of all certain knowledge, Aristotle hardly
mentions it. According to Aristotle, the essenceof mankind is to nous,
to know, to intuit. Man has the capacity for the direct apprehension of
the essenceof things, to see the universal in the individual-and
in this
capacity intuition is infalliblels Aristotle gives no justification for the existence of infallible intuition. He merely observesthat without it, the acquisition of certain knowledge would be impossible.
For Aristotle, scientific knowledge had to be universal, immutable and
absolutely certain. The existence of essencesassured that it would be universal and imrnutable. Intuition guaranteed that it would be certain. Aristotle can be found saying that, whenever observation and theory co'flict,
credit must go to obserwationaand warning against speculation from too
3. Aristotle,PosteriorAnalytics,pt. 2, ch. 19.
4. Aristotle,
The Generation
ol Animak,76Ob2B.
2l
epistemology.Science deals only with that which is universal, with essences.
After essenceshave been genuinely intuited, checking by observation is
superfluous.
By the time of Francis Bacon (1561-1626), the scientific revolution was
well under way with the work of Copernicus, Galileo, Tycho Brahe, I(epler,
Gilbert, and I{arvey, but to anyone living at the time the trend would
have been difficult to discern. Bacon hoped to replace the Aristotelian
deductive method with his method of i-rue induction, or induction by exclusion. Just as Aristotle had devised a set of lules for deduction, Bacon was
going to do the same for inductive logic. I{e hoped to produce an inductive
machine for grinding out true, scientific laws.
Bacon's plan was to begin with extensive gathering of data without any
speculation.GIfe felt that the best way to preclude any premature speculation was to have this labor performed by unlettered underlings. Besides,
he believed that it was "somewhat beneath the dignity of an undertaking
like mine that I should spend my orvn time in a matter which is open
to almost every man's industry."? No doubt comments like these prompted
Harvey to say that Bacon wrote philosophy "like a Lord Chancellor." Bacon
was never to have his army of workers. Instead, in the last year of his
life he himself tried to mal<e a beginning in the extensive gathering of
data completely on his own. Even if Bacon had been given his army of
workers, it is doubtful that his enterprise would have been very successful.
It is now commonplace to recognize, as Darwin recognized over a century
ago, that "the observer can generalize his own observations incomparably
better than anyone else" and that "observation must be for or against
a view if it is to be of any service."
Bacon hoped to assure the truth of his generalizationsby extensive factgathering and induction. As data were gathered, they were to be entered
on three tables-a table of essence,a tabie of deviation, and a table of
5. Ibid.. 756^1.
6. Bacon(1620),bk. 2, AphorismXI.
7. Ibid,. p. 271.
22
Darwin and Ilis Critics
degree. For example, if the nature of heat is under investigation, those
things that seemed hot would be listed on the fir.st table, those that lacked
heat on the second, and variations in heat on the third. Only after these
tables were filled out did induction actually begin. True induction for Bacon
was induction by exclusion or, as it is sometimes called, complete elimination. If the relevant concepts have already been formulated and if natural
phenomena can be divided into a finite number of discrete natural kinds,
then induction by complete elimination is possible. All the possible causes
of a kind of event can be listed and all but one eliminateci. But under
such circumstances induction by complete enumeration is also possible.
Bacon thought that the only induction recognized by Aristotle and practiced by his followers was induction by simple enumeration as exemplified
in argument (3). But Aristotle did not consider rhe process by which the
universals were abstracted from the individual as induction;it was intuition.
Induction of any kind could occur only at the level of universals, and
at this level both induction by complete enumeration and induction by
complete exclusion (or elimination) are possible, since Aristotle believed
in the existence of a finite number of discrete natural kinds. Argument
(5) below is an example of an induction by complete exclusion.
(5)
Scalene triangles have three
sides.
Isosceles triangles have three
sides.
Equilateral triangles have three
sides.
(6)
Man, the horse, and the mule
are longJived.
Man, the horse, and the mule
are all bilelessanimals.
Hence, all bileless animals are
long-lived.
Hence, all triangles have three
sides.
r ue Inductive Method
23
and are deductive in nature. Aristotle was cognisant of this fact.8 Many
later philosophers were not. This conflict between the desire to mahe induction certain while still remaining inductive is evident in Bacon's writings.
Induction by exclusion was not only a method of discovery but it afforded
absolutely certain knowledge. "Now what the sciences stand in need of
is a form of induction which shall analyse experience and take it to pieces,
and by a due process of exclusion and rejection lead to an inevitable
conclusion."0
Bacon nraintaincd that scientistswere to proceed from senscperception
of the individual to the lowest universals and from there gradually, without
omitting a step, to axioms of greatest generality.'n Taken literally, this
view of induction would completely eliminate deduction as anything but
an after-the-fact exercise,but on occasion, Bacon seems to think otherwise.
Both deduction and induction have roles to play in science-"from the
new light of axioms, which have been" educed from those particulars by
a certain method and rule, shall in their turn point out the way again
to new particulars, greater thir-rgsmay be looked for. For our road does
not lie on a level, but ascends and descendsl first ascending to axioms,
then descendingto works."11
It is difficult to reconcile these remarks concerning the role'of deduction
in science with Bacon's earlier pronouncements about gradual ascent. If
the formation of concepts or the discovery of laws is to proceed by true
induction, step by step, without any jumps, how can a concept or a law
be oI wider scope than the evidence from which it was derived? To the
extent that true induction is possible, the collateral security of deducing
new confirming instancesis impossible.
Herschel, Mill, and Whewell all concurred at least verbally in Bacon's
confused distinction between deduction and induction in terms of increasing
and decreasing generality, and much of lferschel and Mill consistsmerely
in tidying up Bacon's methods of induction. Both authors, however, empha-
The conclusion to argument (5) seemsto follow from the premisesnecessarily because of the suppressedpremise that these are all the species of
triangle that there are. All speciesof triangle have been enumerated. when
the suppressedpremise is added, the argument becomes deductive. Argument (6) is actually taken from Aristotle. Here, too, the cleductive nature
of the inference is readily apparent. only if the three species mentioned
are ail the bilelessanimals which exist is the argument valid. Both induction
by complete enumeration and induction by complete elimination are possible
only in a world which is divisible into a finite number of natural kinds
sized the role of deduction a good deal more strongly than Bacon had.
For example, I{erschel says:
It is to our immortal countryman Bacon that we owe the broad announcement of this grand and fertile principle; and the development
of the idea, that the whole of natural philosophy consists entirely of
B. Aristotle,PosteriorAnalytics"68b15,
9 . B a c o n( 1 6 2 0 ) ,p . 1 9 .
10. Ibid., bk. 1, AphorismCIV.
1 1 . B a c o n( 1 6 2 0 ) ,b k . 1 , A p h o r i s mC I I I .
24
Darwin and Ilis Critics
a series of inductive seneralizations, commencine \a,it[ the nrost circumstantially stated particulars, and carried to u.iver.sal la*,s, or axioms,
which comprehend i' their statements every subordi'ate degree of generality, and of a corresponding series of inverted reasoning fÄm genäars
to particulars, by which these axioms ar"etr.acedback into their ri*roresr
consequences,and all ltarticular propositiorrs deduced from them
3ut it is very itnportant to observe, that the successfulprocessof scien_
.
tific enquiry demands continually the alternate use of both the inductiue
and d edttctiue mcthod.r,
Herschel resolves tl-re conflicting roles of deduction and inductio' by
observing that "in the study of nature, we must not, therefore, be scrupulous
as to hoza we reach to a l<nowledgeof such general facts: providecl only
we verify thern carefully rvhen once detected, we must be content to seize
them rvherever they.are to be found."13 careful induction was advisable
but not necessary.Hence, deductive verification woulcl be more than an
empty exercise.
Mill had much the same story to tell but did so with considerably
more force:
Bacon's greatest merit cannot therefore consist, as we are so of ten
told that it did, in exploding the vicious method pursued by the ancients
of flying to the highest generalization first, and deducing the micldle
.
principles from them; since this is neither a vicious ro. o., exploded,
but a universally accredited method of moder.n science,and that to which
it owes its greatest triumPhs.lr
The distinction between the temporal .order of discovery and the logical
order of a reconstructedlogic hacl surfaced at last. unfortunately, an awareness of this crucial distinction came in the midst of the great controver"sy
bet*'een whewell and Mill and did little to improve the coherence o[
the debate. Each side accused the other of confusing proof with discovery.
In following the course of this controversy, one gets the impr.essionthat
neither man appreciated the importance of this distinction until after he
had committed himself on too many issues.Thereafter, each tried to shore
up his position without openly admitting error, while trying to expose the
other's evasive maneuvers. The situation was not helped by an ambiguity
in the key term "induction." whewell callecj alr processeswhich contributed
to the construction of a scientific theory "induction," whereas I{erschel and
Mill
limited the term to inferences from the ]<nown to the unknow'.
1 2 . H e r s c h e(l1 8 3 0 ) ,p p . 1 0 4 , 1 7 4 - t 7 5
13. Ibid., p. 164.
1 4 . M i l l ( 1 8 7 4 ) ,p p . 6 8 - 6 9 .
.rre Inductive Method
25
Herschel and MilI thought that both the logic of discovery and the logic
of justification could be analyzed in terms of deduction and induction,
ryhereasWhewell thought that no simple rules could be given for the process
of discovery.15For Ilerschel and Mill the key tool in the logic of discovery
and justification was induction by elimination.
Darwin repeatedly made use of induction by elimination. For example,
in his paper on the Parallel Roads of Glen Roy (1839), he reasoned that
these roads or shelves were caused by either lakes or arms of the sea.
If they were caused by lakes, then huge barriers had to be erected and
removed successivelyat the rnouth of the glen. Since Darwin could not
see how such huge quantities of rocl< could be moved about, he eliminated
the lake hypothesis. Flence, the shelves were remnants of former shores
of the sea,produced as the land was gradually raised above sea level.
As Darwin's critics have been happy to point out, Darwin was mistaken.
Soon after publication of the Glen Ro]' paper, Agassiz'sglacier theory was
brouglrt to Darwin's attention, and Darwin immediately rcalized that huge
barriers of ice provided just the sort of dams needed by the lake hypothesis.
But not until 1861 was he finally forced to admit defeat, writing to Lyell,
"I am smashed to atoms about Glen Roy. My paper vlas one long gigantic
blunder from beginning to end. Eheu! Eheul"'u In his autobiography,
Darwin added:
During these two years I tool< several short excursions as a relaxation,
and one longer one to the Parallel Roads of Glen Roy, an account of
which was published in the 'Philosophical Transactions.' This paper was
a great failure, and I am ashamed of it. Having been deeply impressed
with what I had seen of the elevation of the land of South America,
I attributed the parallel lines to the action of the sea; but I had to
give up this vierv when Agassiz propounded his glacier-lake theory. Because no other explanation was possible under our then state of knowledge, I argued in favour of sea-action; and my error has beeh a good
lesson to me never to trust in science to the principle of exclusion.lT
Darwin says that the Glen Roy paper taught him a good lesson-never
to trust the principle of exclusion-precisely that principle which empiricist
philosophers were touting as the key feature both in the logic of discovery
and in the logic of justification. Darwin was correct to doubt this principle
but wrong in thinking tirat he could do without it. He continued to use
the principle of exclusion throughout his later works. What he had learned
1 5 . I b i d . ,p p . 1 9 9 ,2 8 4 ; F l e r s c h e( l1 8 4 1 ) ,p p . 1 9 6 - 1 9 7 .
1 6 . S e p t e m b e6r, 1 8 6 1M
, o r e L e t t e r s( 1 9 0 3 ) ,2 : 1 8 8 .
1 7 . D a r w i n ( 1 9 5 8 ) ,p . 8 4 .
26
Darwin and His Critics
was not that the principle of exclusion could neuer be trusted but that
it could never be trusted completely. It could, however, confer some probability on a hypothesis. It could not in actual practice make a hypothesis
absolutely certain, since in the natural sciencesit is never possible to elimi_
nate all alternatives.
In his Glen Roy paper Darwin had obviously overlooked the possibility
of ice barriers, but there were other possibilities as weil. For example,
even if the shelves had been lormed by sea action, a gradual d"c."or.
in sea level would have explained ihem as welr as a gradual elevation
of the land. (In point of fact, the sea level had decreased 400 feet in
the preceding 1000 years.) In his coral reefs paper (1842) Darwin ex_
plained the growth of coral reefs by reference to the gradual sinking of
the ocean floor. The facts, he contended, were inexplicable by any other
theory. In this instance Darwin's theory was basically correct, but he had
not eliminated all the possibilities-to name one, a gradual increase in
sea level. (As mentioned previously, the opposite had actually occurred.
Darwin also mentions certain phenomena which wourd have had the same
effect as a drop in sea level.)
Darwin also used this line of reasoning in the Origin of Species (p. 33)
and, The Descent of Man (p. 269). Again he had not eliminated all possible alternatives, bur he did think that he was justifiecl in cliscounting the
current explanation in terms of special creation. I-Ie dismissed it, not
because it was an i'correct scientific explanation, but because it was not
a proper scientific explanation at all. "I would give absolutely nothing
for the. theory of Natural selection, if it requires miraculous additions at
any one stage of descent."18Darwin's reasoning on this issue will be ex_
amined later in chapter 4.1e It might also be mentioned that Bacon was
no more successfulthan Darwin in eliminating all alternative explanations
for phenomena he was investigating. For example, his explanation of the
tides was erroneous because, in opposition to Garileo, he discounted the
rotation of the earth. Galileo's explanation, however, was equally
erroneous.2o
The method of exclusion, when incomplete, failed to provide absolute
proof for a hypothesis, but could incomplete inductions provide at least
some support for a theory? Da'win thought they could. The feature of
the philosophies of science professed by Herschel and Mill which would
1 8 .D a r w i n L
, i l e a n dL e t t e r s( l B B 7 ) , 2 : 7 .
19. Seealsothe reviewsby Hopkinsand Wright in this volume.
20. Bacon(1620),bk. 2, Aphorisms
XXXViand XLVI.
i'he Inductive Method
27
be of greatest use to Darwin's critics was their contention that only logically
necessarymodes of inf erence aflorded proot'. Although MiU recognized the
importance of approximations in science, they were merely stages on the
road to something better.zl Until this final stage was reached, proof had
not been provided. The only reason for resorting to approximations was
that the correct definitions had not yet been discovered, the phenomena.
had not been correctly reduced to natural kinds. When they had been
discerned, universal correlation was guaranteed.22In abstract sciences lihe
zoology, botany and geology "a probability is of no account; it is but
a momentary halt on the road to certainty, zrnd a hint for fresh
experiments,"23
Mill has received considerable credit for not dismissing evolutionary
theory out of hand as l{erschel and Whewell had done,2a but the credit
is not deserved.'z5Mill discussesevolutionary theory in a footnote to his
System of Logic, but only after treating Broussais' hypothesis about the
localization of disease, Gilbert's contention that the earth is a magnet,
and the suggestion that the brain be looked upon as akin to a voltaic
pile. Finally, Mill says:
fuIr. Darwin's remarkable speculation on the Origin ot' Speciesis another unimpeachable example of a legitimate hypothesis. What he terms
"natural selection" is not only a uera causa, but one proved to be capable
of producing effects of the same kind with those which the hypothesis
ascribes to it: the question of possibility is entirely one of degree. It
is unreasonable to accuse Mr. Darwin (as has been done) of violating
the rules of Induction. The rules of Induction are concelned with the
conditions of Proof. Mr. Darwin has never pretended that his doctrine
was proved. I-Ie was not bound by the ruies of Induction, but by those
of Hypothesis. And these last have seldom been more completely fulfilled.
Ile has opened a path of inquiry full of promise, the results of which
none can foresee.And is it not a wonderful feat of scientific knowledse
and ingenuity to have rendered so bold a suggestion, which the fiÄt
impulse of every one was to reject at once, admissible and discussabie,
evelr as a conjecture?'?6
Mill's endorsement was a double-edged l<nife. While admitting the legitimacy of Darwin's procedure as a method in the logic of discovery, he
2 1 . M i l l ( 1 8 7 4 ) ,p . 3 8 7 .
22. Ibid., p. 388.
23. M;ll (1865),2:308.
2 4 . D e B e e r( 1 9 6 4 ) ,p . 1 6 4 ,a n d E l l e g ä r d( 1 9 5 8 ) ,p . 1 9 5 .
25. llimmelfarb (1959).
26. Mill (187+),p. 328.
,p,
uar.wrn and His
Cr.itics
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"u.li
30
Dalwin and Ilis Critics
,'he Inductive Method
philosophers set, it might not be the theory that was at fault. what then
is the current view on the philosophy of science? How does evolutionary
theory, both in its original form and in its modern reformulations. measure
up to today's standards?
The most widely accepted moclel of scientific method.among logical em_
piricists is termed the hypothetico-cleductivemodel (H-D model). On this
model, a hypothesis is formulated in some unspecified manner and then
checked by deducing va'ious consequencesfrom it. If the deductions turrr
out to be true, then the hypothesis is gradually confirmed. No scientific
from a law, that law must be universal in form. Neither. deducibility nor
the universality of the relevant laws can be abandoned without losing this
eleganceand simplicity. Flowever, many putative laws in science,especially
in biology and specifically in evolutionary theory, are not universal in form.
hypothesis, however, is ever completely confirmed or verified. Scie.tific
laws are universal in form, and not all consequencescan be crrecked.However, if one of the deductive consequencesof the hypothesis turns out to
be false, the hypothesis is immediately shown to be false and must be
rejected. I{ence, falsification is very easy.
The I{-D model has the virtue that it does not prescribe any rigid procedures in discovery. There is no cut-and-d'ied rogic of discovery. certainly
there may be methods of scientific investigation which have proved fruitful
in the past and are more likely to produce results than others. For example,
analogiesand models are two very effective means of discovery,while simple
trial-and-error is not very efficient. But the chief virtue of the H-D model
is that it recognizesthe impossibility of absorute proof for any scientific
31
Thev are statistical.statements,trend and tendency statements, and approxirlations. From the statement that blue-eyed couples almost always produce'
blue-eyed children, it is impossible to deduce the eye-color of a particular
child. I{orvever, it can be inferred tl-rat it is highly likely that all of the
clrildren of a blue-eyed couple, ceteris paribus, will have blue eyes. The
inferenceis inductive.
If all less-than-universalstatements are interpreted merely as particular
statements which assert o,nly that at least one subject has the predicate
indicated, then the relation between verification and falsification is reversed.
\/erification becomes easy; falsification impossible. But scientists do not
treat all less-than-universal statements as particul:rr statements. There is
considerabledifference between the claim that 99 percent of smokers wili
die of lung cancer and the claim that 1 percent of them wi1l. This difference
is the subject matter of statistics and probability theory. In this type of
inference, neither verification nor falsification is easy. In neither case will
a single observation suffice-even in principle. Populations have to be defined and samples taken. Currently, philosophers of science are trying to
iormulate ivhat might be cailed a hypothetico-inductive model of science,
but it is proving to be a very frustrating task. Numcrous troublesome paradoxeshave arisen, and few solutionshave been forthcoming.
theory. According to the method of "inverse creduction" incorporated in
the H-D model, a scientific theory can become increasingly more probable;
that is all. rn inverse deduction, one reasons from the truth of specific
inferences made from a law to the increased likerihood that the law is
true. From the point of view of deductive logic such inferences arc fallacious-the fallacy of affirming the consequent. of course, early philoso-
How appropriate are current schematizations for evolutionary theory?
Darwin maintained that the Origin was one long argument and a convincing one at that:
phers of science recognized the method of inverse deduction but thousht
it was oniy a temporar.yheuristic device.
As might be expected from its brevity, the foregoing clescription of the
I{-D model is overly sirnple. IJypotheses are not tested in isolation but
embedded in theories. Thus, if a decluctive consequenceof the theory turns
Sorne of my critics have said, "Oh, he is a good observer, but has
no llower of reasoning." I do not think that this can be true, for the
Origin of Species is one long argument from the beginning to the end,
and it has convinced not a fe'rv able men. No one could have written
it without somepower of leasoning.3t
out to be false, a single hypothesis is not falsified. I{ather, any one of
severai hypothesesand observationsmay be at fault. rnstead of abandoni'g
a theory upon a negative deduction, the theory is usually modified, and
An argument it may be, but the traditional notions of deduction and
induction were completely inadequate for characterizing it. For example,
Darwin saysin the opening paragraphs of the Origin:
considerable latitude is permitted in the degree of modification permissible
while still terming the theory the ,,same,,theory.
The elegance and simplicity of the H-D model stems from its deductive
character. In order for singular observation statements to be deducible
For I am well aware that scarcely a single point is discussedin this
volume on which facts cannot be aclduced, often apirarently leading to
3 1 . D a r w i n ( 1 9 5 8 ) ,p . 1 4 0 .
20
rz
Dar.winand His Critics
conclusions opposite to those at which
I have arrived. A fair resurt can
be obtained only by fully.stating u"a
Uofun.ing th" fr.i, il;;;;"".,
on both sides of each question; and this
cannot possiblybe here däne-r,
In a letter to Il. G. Bronn, Darwin
admits, ,.you put very well and very
fairly that I can in no onc i.stance
exprairr the course of modification
in any particular instance."ss If evolution
by natural selection was to be
accepted at all, it woulcr have to
be "chiefly from trris view connecting
under an intelligible point of view
a host of facts. when we descend to
details, \,\'e can prove that no one
specieshas changecl; nor can we prove
that the supposed changes are beneficial,
which is the groundwork of the
theory. Nor can we explain why some
species have changed and others
have not."3r
As Huxley observed, the origin is "a
mass of facts crushed and pounded
into shape,rather than rreld together by
the orclinary mediurn of an obviorrs
logical bond; due attention will, *,ithout
doubt, clisco'er this bond, but
it is often hard to find."35 The modern
reader frequently grows impatient
with Darwin's method in the Origin
of piling example on example, but
this was the only rnethocl open to hirn
given ti-restructure of evorutionary
theory' This format is still characteristic
of works in evorutionary theory.36
As Darwin formulated it, evolutionary trreory
clid not permit verification
or falsification by the simple expedient
of deducing a single observational
consequenceand checking it. Given Newton's
equations and a few reasonably unproblematic simplifying assumptions
and boundary conditions, a
physicist could deduce some fairly precise
observational consequenceswhich
could be used to confirm or disconfirm his
theory. He courd deduce where
Mars should be at a precise time. Darwin's
theory was neither mathematicar
in notation nor deductive in form. Given
evolutionary theory and the kind
of data available to a biologist, no precise,
unequivocar inferencesrvere possible' one could not predict how an extant
spe;ies wourd evorve or retrodict
how an extinct species did evolve. At best,
only a range of some more
or less possible outcomes could be generated.
In this respect) Darwin,s
theory was at a decidecl disaclvantage.The
two means of verification recognized in Darwin's day were the deductive
subsumption of one general law
under a more general law and the deduction
of specific observationar con3 1 . D a r w i n ( 1 S 5 9 ) ,p . 2 .
3 3 . _ O c t o b5e,r t 8 6 0 ,i 4 o r eL e t t e r s( 1 9 0 3 ) ,I : 1 7 2 _ 1 7 J .
34. Dawin, Lile an'dLetters(1887),ZriiOt.- - ' "
3 5 . H u x l e y( t 8 9 6 ) , p . 2 5 .
3 6 . S e eD o b z h a n s t(yt S t Z ; , M a y r ( 1 9 4 2a n d
1963).
:
i
i
i'
The Inductive Method
JJ
sequencesof the law. Darwin's basic principles were related inferentially
but not in a strict deductive hierarchy. Evolutionary theory was basically
statisticalin nature. The relevant inferenceswere inductive.
Charles S. Peirce was one of the few philosophers who recognized and
emphasized the statistical nature of evolutionary theory. FIe saw Darwin's
theory as one more application of the statistical method which Maxwell
(1831-1879) had used so successfullyin physicsand Quetelet (1796-1874)
in sociology.s?The work of these men and others had prepared the scientific
community for "the idea that fortuitous events may result in a physical
law."38 Peirce's accurate understanding of the structure of evolutionary
theory is sufficiently rare to warrant reproducing in its entirety:
The Darwinian cont,lol,ersyis, in large part, a question of logic. Mr.
Darwin proposed to apply the statistical method to biology. The same
thing has'been done in a widely dif{erent branch of science, the theory
of gases. Though unable to say r,irhat the ,movements of any particular
molecule of gas would be on a certain hypothesis regarding the constitution of this class of bodies, Clausius and Maxwell were yet able, by
the application of the doctrine of probabilities, to predict that in the
long run such and such a proportion of the n-'roleculeswould, under
given circumstances, acquire such and such velocities; that there would
take itlace, every second, such and such a number of collisions, etc.;
and from these propositions they were able to deduce certain properties
of gases, especially in regard to their heat-relations. In like manner,
Darwin while unable to say what the operation of variation and natural
selection in every individual case will be, demonstrates that in the Iong
run they will adapt animals to their circumstances.Whether or not existing anirnal forms are due to such action, or what position the theory
ought to take, forms the subject of a discussion in which questions of
fact and questionsof logic are curiously interlaced.3e
Although Peirce was almost alone in approving of the form of Darwin's
theory, he joined the majority in rejecting selected parts of the content.
He preferred Agassiz'sEssay on Classification (1859).40 In 1893 he passed
the following judgment on evolutionary theory:
What I mean is that his hypothesis, while without dispute one of
the most ingenious and pretty ever devised, and while argued with a
37. JamesClerk Maxwell was a Scottishphysicistwhosefamousequationsrevolutionizedphysics.M. A. Quetelettrsedstatisticsin a rudimentaryway in compiling
figures{or crimesand suicides;see O_uetelet(1846). Herschelreviewedthis work
in the EdinburghReaieu (1850), 42 i1-57.
3 8 . P e i r c e( 1 9 3 5 ) ,6 : 2 9 7 .
39. Peirce(1877\.
40. Peirce(1931), 1;203-205.
34
fhe Inductive Method
Darwin and I-Iis Critics
wealth of knowledge, a strength of logic, a charm of rhetoric, and above
all with a certain magnetic genuinenessthat was almost irresistible, did
not appear, at first, at all near to being proved; and to a sober mind
its case looks less hopeful now than it did twenty years ago.41
At the turn of the centuly, the fortunes of evolutionary theory had
reached their lowest ebb. Physicists to a man had proved that the earth
was not neariy as old as Darwin's theory required. Geneticists such as
de Vries and Morgan were claiming that mutations were discrete, not
gradual; thus, Darwin had been wrong in thinking that evolution was
gradual. The excessesof evolutionists like Haeckel and the disputes concerning orthogenesis and neo-Lamarckianism had earned for evolution a decideclly bad reputation. It was more metaphysics than science.a2One would
expect the situation to irnplove consiclerablywhen physicists and geneticists
discoveredtheir errors, and it did, but the problem of the form of evolutionary theory remained unchanged. It was still, at best, pr.obabilistic. In the
1930's Fisher, Haldane, and Wright attempted to use the recent advances
in genetics to produce a theory of evolution which was both mathematical
and genetical. The unit of evolution became the gene, and evolutionary
change was to be measured in terms of changes in gene frequencies. Even
so, the situation with respect to verification did not irnprove much. Given
modern evolutionary theory, knowledge of mutation rates, rates of difierential reproduction, and so forth, the best that a modern evolutionist could
do was to provide a distribution function of possible outcomes.a3
Two alternatives seem open to us at this juncture: either revert to a
hypothetico-inductive model of science or argue that evolutionary theory
after a century is still inadequately formulated and that in a more finished
form will conform to the lI-D model. The problem with the first alternative
is that there is no H-I model. Thus, this alternative reduces to the admission
that there is no reconstruction of scienceappropriate to evolutionary theory
as it now stands. Biologists are currently working on the second alternative.
Some are attempting to reformulate macro-evolutionary theory more rigorously so that deductive confirmation or disconfirmation is possible.aa
others find evolutionary theory in terms of organisms and their interactions
4 1 . P e i r c e( 1 9 3 5 ) ,6 : 2 9 7 .
42. unfortunately,spaceprohibitsus from pursuingthe history of the reception
of evolutionarytheory during this period. Peter Vorzimmer (lg70) has wiitten
an informedbut uneventreatiseon these"yearsof controversy."see also provine
fl971).
43. See,Ior- exalnple,Lewontin (196g)
sec Hull (1974),
; for fur-thercliscussion
44. MacArthurand Wilson (i967) and Williams (I9?0).
t,
i:
35
too crude to permit an adequate formulation of evolutionary theory. Instead, they cail for a molecular version of evolutionary theory, hoping in
this manner to fulfill the requirements of the H-D model.as This reductive
maneuver is quite common in science.Whenever laws at one level of analysis
appear indeterministic, analysis of the phenomena at a lower level often
revealsrelations which are closer to universality. The only thing that stands'
in the way of true, universal laws is accuracy of measurement and the
level of analysis. It should be remembered, however, that after years of
successin physics, the reductive program was frustrated at the subatotnic
level.
On the first alternative, philosophers of science have more work to do'
They have to work out the details and general outline of a reconstruction
of science appropriate to evolutionary theory in its present form. After
all, notice how much better evolutionary theory looked when Peirce switched
from the Newtonian to the Maxwellian paradigm. On the second alternative,
biologists have more work to do. They have to produce a scientific theory
consisting of universal laws which permit specific predictions. On either
view, evolutionary theory and philosophy of science are still at odds'
Most of this chapter has concetned the detrimentil effects of early philosophiesof scienceon the reception and accePtanceoI evolutionary theory'
A few words must be said in defense of these systems.When early philosophers of science were not concerned with rigid proof and certainty, much
that they said was applicable to science in general and to evolutionary
theory in particular. (Compare Hopkins' strict interpretation with Fawcett's
more informal treatment in this volume.) For example, Bacon provides
a list of auxiliary devices to help in scientific investigation. These praerogatiue instantiarunl are much more original and applicable to actual scientific
investigation than his methods of true induction' Almost everything that
I-Ierschelhad to say about the discovery and verification of scientific theories-when he was not being rigorous-fits evolutionary theory perfectly.
Miil is similarly reievant when he is discussing such things as multiple
causation,approximate generalizations,and probable inference.
Even the extensive fact-gathering encouraged by these empiricist philosophies of science was not entirely detrimental to evolutionary theory, given
its statistical nature. Darwin did not waste the twenty years preceding
tlre publication of the Origin. Only such a wide sarnpling of data had
the slightest chance of supporting it. The relation between Whewell's phi45. Schaffner(1969).
36
Darwin and His Critics
losophy of scienceand evolutionary theory is even more equivocal. Nothrng
in Whewell's second-levelphilosophy of science was incompatible with evolutionary theory. He did not concur in the popular conviction that a strict
logic of discovery would assure truth. In the colligation of ideas why not
superinduce the idea of evolution by natural selection on the facts? Certain
ideas are self-evident. Why not evolution? The answer can be found at
a deeper level in a belief which Whewell shared with Aristotle, Bacon,
Herschel, and Mill, a belief in the existence of natural kinds definable
by a single set of necessaryand sufficient conditions, a belief in essences.
Empiricists wanted to eliminate so-called "occult qualities" from science
and yet they retained that element in earlier philosophies which contributed
the most to the prevalence of metaphysical entities-essentialism.
$.
K.
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ki
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3 ' Occult Qualities
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il
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Nineteenth-century scientists were in agreement that all references to
occult qualities should be excluded from science, but they were not clear
as to rvhat it was about a quality that made it occult. Bacon thought
that such Aristotelian notions as the hdt and the moist were occult qualitres
but that his own explanation in terms of the movement of unobservable
particles was perfectly acceptable. Newton thought of light as being corpuscular but excluded all reference to such theoretical entities from his
published writings. Such hypothesesas light corpuscle! and the aether had
no place in science.Darwin found Forbes's explanation of the distribution
of living creatures in terms of polar principles absolute rubbish, on a par
with magnetism moving tables. Owen's Law of Irrelative Repetition in
terms of a polarizing force opposing the Platonic rati'o was scarcely better.
Yet his own theories necessitated unobservable gemmules and the spontäneous generation of the original life fonns in the distant past. Mendel
claimed that he defined constancy of type merely as the retention of a
character during the period of observation, yet could not avoid postulating
unobservable"factors" as the cause of his observed ratios. In the preceding
chapter, the Victorian aversion to speculation in the senseof large inductive
leaps was examined. In this chapter we will deal with speculation in the
senseof unobservable entities, substances,and properties. The crucial distinction is between theoretical entities for which indirect evidence can
be obtained and metaphysical entities which are unobservable in principle.
Bacon intended the notion of gradual induction and complete elimination
to insure Ihe truth of the generalizations derived, but induction from experience also served a second function in empiricist epistemology-to insure
the empirical content of scientific terms. If scientific concepts are abstracted
from experience, regardless of how large the inductive leap, they will still
be grouncled in experience and not empty verbiage. From Bacon and New-
3B
Darwin and His Critics
Occult Qualities
ton to l{erschel and Mill, scientistsand empiricist philosophers had a deepseated aversion to what they viewed as Scholastic occult qualities. One
of the primary goals of scientists during and after the scientific revolution
was to make certain that scientific concepts and generalizations were not
empir'ically meaningless. The issue was not whether a scientific generalization was true but the more basic question of whether or not it was empirically rneaningful.
rras known by intuition, and intuition was infallible. Observation might
rvell excite intuition to act, but only intuition was capable of apprehending
the tme objects of scientific knowledge-eternal, immutable essences.The
most obvious objection to Aristotle's postulation of infallible intuition is
that people do make mistakes. In fact, almost everything which Aristotle
Aristotelian science, in the.hands of the Scholastics, had degenerated
to such an extent that many putatively empiricai claims were actually immune to experimental disproof. Such notions as the hot and the moist
had begun in Aristotle as observational terms. If something felt hot, then
it was i'rot. But gradually these rerms took on additional dimensions. Maybe
one body felt hotter than another, but that did not guarantee that it contained more of the hot. The gradual evolution of observational terms to
something else is common throughout the history of ideas, but the nature
of this "something else" varies- One possibility is.that the term becomes
a theoretical term in a well-articulated scientific theory. For example,
"force" rnay well have begun its career as an obserwational term referring
to the effort a human being expends in holding a heavy object but eventually such reference became all but irreievant. Theoretical terms frequently
refer to unobservable entities, but because these terms occur embedded
in a well-articuiated scientific theory, indirect evidence can be obtained
for the existence of the theoretical entities to which they refer. Another
fate for an observational term is to become purely metaphysical. There
is nothing wrong with metaphysical terms, just so long as they are openly
metaphysical and do not masquerade as something else. For example, when
a metaphysician refers to such tl'rings as bare particulars, he is not claiming
that they exist in the same sense that trees ancl planets do. Too often,
however, philosophers and scientistshave confused metaphysical terms with
those that have empirical referents. The consequenceshave been less than
saiutary.
The terms usually singled out by Aristotle's critics as being ,,occult,,
were those designed to characterize Aristotelian essences.Aristotle would
have been dismayed by the claim that his essenceswere unknowable, since
for him essenceswere the oniy things that were knowable in the true sense
of the word. Perhaps essenceswere furthest from the level of gross observation, but they were the most l<nowablein the senseof intuitive knowledge.
Aristotle's critics, of course, would reply that intuition itself was a metaphysical notion. Aristotle claimed that, at bottom, ail certain knowledee
39
himself claimed to have intuited turned out to be false. Several evasive
nraneuversare possible for saving the notion of infallible intuition. The
extent to which one uses one of these maneuvers determines exactly how
rnetaphysicalthe notion of intuition itself becomes.
One way to salvage the notion of infallible intuition is to deny the status
of intuition to any process that eventuates in falschood. "You say that
vou intuited that all crows are blacl<? Well, here is a white crow." "Oh,
well, that must not have been intuition." Intuition was intended to assure
the tluth of the premises in deductive. arguments so that the truth of the
conclusionswould be assured, but ali that this maneuver does is to shift
the problem back one step. Now the problem is deciding which claims
oI intuition are factual and which mistal<en.
A second way to save intuition is to discount al1 ex_ceptionsas monsters.
Aristotle says that science deals with what happens always or for the most
part, This latter qualification did not mean that scientific knowledge could
bc less than universal in form. Rather, it was included in recognition
o[ the existence of accidents and monsters, and science does not concern
itself with accidents or monsters."That bird is white? Well, then it isn't
a crow." Among normal individuals, Aristotle distinguished between essential attributes and accidental properties. Essential attributes were those characteristicswhich made a thing what it was-its defining characteristics.
Accidental properties were those characteristicswhich varied in a haphazard
rvay from individual to individual-the individual differences which were
to be the raw material of evolution.l In addition to these accidental characteristicswhich occurred quite as a matter of course, Aristotle also recognized
rare individuals completely outside the natural order-monsters.
According to Aristotle, neither accidental properties nor monsters allowed
of explanation and hence were not the proper subject matter of science.
All natural laws were true universal generalizations. What of exceptions?
They were merely accidents or monsters and could easily be dismissed.
It was tl.ris Scholastic habit of monsterbaiting which ploved the greatest
obstacle in the deveiopment of Scholastic science. On the modern view
nf science if is nreciselv fhe "aeeidenrs" and "monsters" which call for
l. See comments on Jenhin's paper.
40
Dalrvin and I-Iis Critics
explanation.e It was Darwin's attention to so-called accidental variations
which led to his theory o[ evolution, and it in turn demolished the Aristotelian distinction betr,r,een
essentialand accidental characteristics.No characteristic is so "accidental" that it cannot become in time typical of a
group. And what would have happened in geneticsif Morgan had dismissed
his one-in-a-million white-eyed male {ruit-fly as an inexplicable accident?
Darwin was aware of the importance of exceptions in science and also
of the human propensity to ignore them:
I had, also, durins rnany years, followed a golden rule, namely, that
whenever a published fac.t, a new observation or thought came across
me, which w'as opposed to my general results, to rnahe a memorandum
of it r.vithout fail and at once; for I had found by experience that such
facts and thoughts rvere far more apt to escape from the memory than
favourable ones.3
He had gathered this admonition frorn Herschel, who had said in his Disc o z r r s a( 1 8 3 0 : 1 6 5 ):
in any case any exception occursJ it must be carefully noted and
.
set aside for re-examination at a more advanced period, when, possibly,
the cause of the exception rray appear, and the exception itself, by allowing for the effect of the cause, be brought over to the side of our inducI
tion; but should exceptionsplove nunrerousand various in their features,
our faith in the conclusion will be proportionally shaken, and at all
i
events its importance lessenedby the destruction of its universality.
Philosopl-rers
and scientiststhrough the ages have been nearly unanimous
in their opinion tl-rat scientific laws l-rad to be universal in form. One way
to save the universality of scientific laws is to discount all exceptions as
monsters, as not propeily fitting the definition of the names of the classes
of entities related in the law. Once the phenomena have been properly
reduced to natural kinds, universal laws must be forthcoming.a
In their investigations, scientists tend to concentrate on exceptions to
their laws with the hope that such an emphasis will Iead to their improvement. Like essentialists,they hope to discover true, universal generalizations;
but, unlike essentialists,they tend to change the law to accommodate the
exception rather than to dismiss the exception as inexplicable. The end
result of tl-re essentialist distinction between essentiai and accidental at2. This view in biology can be traced back at least to William
Harvey, who
in 1657 observed that the laws of nature can often be discerned by careful investigations of rareties.
3. Darwin (1958), p. 123.
4. Mill (1874), p.3BB.
Occult Qualities
+1
tributes is that essential attributes tend to become occult, unobservable,
unknowable. Because this distinction concerns the dcvelopment of concepts
rvithin a system, not some intrinsic quality of a concept from the beginning,
and because there is a strong tendency to dismiss erroneous explanatory
schemata as empty metaphysics, two examples will be discussed at some
length in preparation for the discussion of evolutionary theory and occult
qualities. These examples are Aristotle's polar principles, elements, and
humors-and Newton's light corpuscles, aether, and action-at-a-distance'
In the preceding chapter, Aristotle was quoted as saying that man, the
horse, and the mule were all bileless animals and assuming that these ate
all the bileless animals that there are. But he can also be found saying
that the ass, deer, roe, camel, seal and dolphin lack gall bladders (676b26,
677.30). It would seem reasonable to infer that in a teleological system
like Aristotle's there should be some correlation between lacking a gall
bladder and lacking gall. These referdnces might reasonably be dismissed
asa later development of his ideas, or as oversightsand errors in transcriptron
or translation, but even if they accurately reflect Aristotle's view, he need
not stand convicted of contradicting himself. For .Aristotle, bile was not
merely the fluid secreted by the liver and stored in'the gall bladder. It
was one of the four humors and, as such, part of an interconnected system
o{.concepts.
The basic elements in Aristotle',s science were two sets of polar principles-the l-rot and the cold, the dry and the moist. All phenomena, whether
in physics, physiology, or meteorologY, were explained in the last analysis
by reference to these four qualities. The four basic elements of physics
were fire, air, earth, and water' Whatever properties fire had were due
to its being hot and dry, air hot and moist, and so on. The four humors
forrred the foundation of Aristotelian physiology. Yellow bile (or choler),
like fire, was hot and dry, black bile (or meianocholer),like air, was hot
and moist, and so on. In a healthy person these four humors were balanced,
but when one of them gained ascendancy,iilness resulted. Therapy consisted
in attempts to reinstate this balance'
This system cannot be eiaborated any more fully here' The purpose
of introducing it at all is to show that as a system of interconnected concepts
it is not different in kind from modern scientific theories' Changes in one
element in the systemhave ramifications throughout the system' For example'
in Aristotle's physics of natural place, the natural place for earth was at
the center. Copernicus, by placing the sun (fire) at the center, considerably
simplified astronomical computation, but he overturned all of Aristotelian
&il
+2
Darwin and His Critics
physics, and indirectly physiology, meclicine, meteorology,
and so on. Aris,
totelians had good reason for rejecting Copernicus, suggestion.
Because bile was part of this loosely connected system of
concepts, its
presence or absence was not purely a matter of observation.
some animal
might possessbile, though none was discernible, and others
rack it, though
a bitter fluid could be extracted from the river. similarry,
some animal
might feel no colde' or moister than another animar, but
because it was
iower on the scale of being, it hacl to be colder and moister. .,Cold,,
and
"moist2' became theoretical terms connected only indirectly
to our feelings
of cold and moisture. Because of the subsequent history
of Aristotelian
science and its distance frorn us in time, modern readers
might be tempted
to dismiss the whole system as metaphysicar nonsense,
but Aristotre,s procedure of inventing theoreticar entities which cannot
be observed directly
is not significantly different from modern scientific method.
Today we explain the recurrent fever and chills of malaria
by reference
to the life cycle of a species of plasmodium rather than
bv the cvclical
overpredominance of blood and phregm. we berieve
the action of ,t *
protozoan on the blood cells can be explained in
terms of the morecurar
structure of DNA and RNA, and this structure in terms
of molecules,
atoms, and various subatomic particres. Aristotre stopped
at the lever of
the four qualities. Today we stop at the level of quantum
mechanics. There
is no doubt that our explanation is far superior to
that of the ancient
Greeks. Care must be take', however, in identifying
the features of the
mode'r explanation whicrr make it preferable to
earlier explanations. It
does not lie, as scientists in Darwin,s day contended,
in the paucity of
unobseruableentities.
The elernents in Aristotelian natural scietrce became ,,occult,,,
not be_
cause of the happenstance that the human organism
cannot sense them
directly (after all we cannot perceive ultraviolet
right) but because the
system in which the concepts were embecrcred
was sc loosely organized
that little in the way of indirect evidence was
possibreeither. For exampre,
ever.rthough we cannot see ultraviolet light,
this light has certain effects
on our skin which we can detect..Numerous predictions
can be made about
what ultraviolet light should do, given current theory.
The four qualities
and other elements in Aristotelian ph1,5is5started
out as observablesand
progressed gradually to the rever of unobservabres,
but this deveropment
was not accompanied by a con"esponding increase
in precision in the sys_
temic interrelations of the more theoretic concepts
and between them and
possible observations. For example, a newry
discovered diseasecourd be at-
It.
fi
$r
lr
Nr:
F'
$ti
$nl
Occult Qualities
+3
tributed to predominance of phlegm by one physician and of biie by another,
and there would be no experiential way of resolving the dispute. Extreme
reliance on authority became more and more the order of the day.
Bacon and Newton attributed the degraded state of Scholastic philosophy
both to a penchant for rash, inductive leaps and to a weaknessfor occult
qualities. In order to avoid reference to occult quaiities, they proposed
t.
$,
It
tL.
':
..
r'
that science should make leference only to those entities, substances,or
gualitieswhose character or effects could be immediately shown. For Bacorr,
this proposal took the shape of fulminations against forms. Newton exlrressedthe same messagein his cryptic hypothesisnon fingo.u The manifesto
was easier to proclaim than to'practice. Bacon realized that his tables
could be used to abstract forms as easily as causes,and he went to great
lengtl-rsto assule his readers that this was not what he was doing. Although
lre refelred to "forms," he did not mean anythins like Aristotelian essences:
I cannot too often warn and admonish men against applying what
I say to those forms to which their thoughts and contemplations have
hitherto been accustomed
. For when I speak oI forms, I mean nothing more than those laws and determinations of absolute actuality which
govern and constitute any simple nature, as heat, light, weight, in every
kind of matter and subject that is susceptibleof them.6
The distinction toward which Bacon was groping was between concepts
and laws, between defining a concept in terms of a set of covarying characters and combining concepts thus defined into empirical laws. In actual
practice, Bacon's efforts at discovering causes by his inductive method
differed little from those of the Scholastics.To overlook the "grand distinction" between the coexistence of characters and the successionof phenomena in time was, as it seemed to Mill, "the capital error in Bacon's
view of inductive philosophy."? The conceptuai shift which made the recognition of this distinction more obvious was the change from an ontology
of substancesand attributes to an ontoiogy of events. The paradigm of
causationhad become one billiard bail hitting another.
In Bacon's work, as well as the Scholastics',the search for laws of nature
too often resulted in the enunciation of definitions,s but of equal importance
5. See discussionin the review by Wright included in this volume.
6. Bacon (1620), bk.2, Aphorism XVII.
i. Mill (1874), p.381.
B. The confusion of definitions and laws is still quite common. For example,
D. R. Cressey,using von Hartmann's method of analytic induction, ends up defining
"iriminal violation of financial trust" instead of discovering its causes.See Cressey
(1950) and Robinson (1951).
44
Occult Qualities
Darwin and I-Iis Critics
was the nature of the attributes referred to in these definitions. Although
Bacon tried to restrict himself to observablefacts and nothing but observable
facts, he was no more able to do so than scientists of other ages. In fact,
many of Bacon's most significant errors stemrned from his over-reliance
on superficial appearances. Like Aristotle, he argued tl-rat the earth did
universally admitted theory of the undulation of light,-neither the undulation, nor the very existence of ether being ploved-yet admitted
becausethe views explain so rTluch.l!
\:.
f
{,
not seem to move; hence, it did not move. Like Aristotle, he believed fin the spontaneous generation of macroscopic organisms because careful !i:.
observation showed it to occur' "in animalculae generated from putrification
i,
as in ants' eggs, worms, flies, frogs alter rain, etc." Bacon did concede
i
that more carefui observation was still called for.e In Darwin's day, Sedg- i
wick argued that we should accept the fossil record as we find it,
not interpolate unl<nown fossils and missing strata. I-Iis catastrophic description of fossil forms and geological strata \,\'assupposedly the history
of Creation. "It is not the dlearn of a disordered fancy," he asserted,"but
an honest record of successivefacts that were stamned bv Nature's hanrl
on the chronicle of the material wor1d."10
Could unobserwablesplay an important role in science and, if so, in
what senseunobservable? One of the commonest objections to evolutionary
theory was that it rested on hypotheses,on unobserwableand unknowabie
phenomena. In reply to these criticisms, Darwin wanted to distinguish between theories and theoretical entities and once again took refuge in the
unimpeachable authority of Newton. In a letter to Gray he objects:
Your distinction between an hypothesis and theory seems to rne very
ingenious: but I don't think it is ever followed. Every one now speaks
of tlre undulatory tlteorlL of light; yet the ether is itself hypothetical,
and the undulations are inferred only from explaining the phenomena
of light. Even in the theory of gravitation is the attractive power in any
way know,n, except by explaining the lall of the apple, and the movements
of tlre Planets? It seems to me that an hvpothesis 1s deuelobed into
a theory solelyby explaining an ample lot of facts.tt
He continues along much the same vein in a letter to F. W. llutton:
I am actually weary of telling people that I do not pretend to adduce
direct evidence o[ one species changing into another, but that I be]ieve
that this vier'v in the main is correct, because so many phenomena can
be thus grouped together and explained. But it is generally of no use,
f cannot make persons see this. I generally throw in their teeth the
9. Bacon(1620),bk. 2, AphorismXL and XLI.
10. Sedgwicl,,
Life and Letters(1890),2:190.
1 1 . D a r w i n ,F e b r u a r yl B , 1 8 6 0 L
, i l e a n d L e t t e r s( 1 8 8 7 ) , 2 : 8 0 .
45
Finally, he wrote to Lyell:
With respect to Bronn's objection that it cannot be sl'rown how life ''
arises,and likewise to a certain extent Asa Gt'ay's remark that natural
selectionis not a aero:caLrsa,I'"vasmuch interestedby findi1g accidentally
in Brewster'sLife,of Newton, that Leibnitz objected to the law of gravity
becauseNewton couid not show what gravity itself is. As it has chanced,
I have used in letters this very same argument, little knowing that any
one had really thus objected to the larv of gravity. Newton answers by
saying that it is philosophy to make out the movements of the cloch,
though you do not know why the weigl-rtdescendsto the ground. Leibnitz
lurther objected that the 1aw of gravity was opposed to Natural Religion!
Is this not curious? I really think I shall use the facts for sonte introducloly remarks for my bigger book.13
Without realizing it, Darwin had chosen an especially inaPpropriate
champion, both becausegravity, in'terpreted as an innate attraction betu'een
occult quality on a very subtle
every pair of particles of matter, uras
^n
level and becauseNewton himself was one of the most influential advocates
of the view of sciencewhich Darwin was being forced to combat' Newton
stated his ideas on science very grudgingly and with more than a little
petulance. They were elicited by attacks first on his theory of light and
then'on his law of universal gravitation.
Early in his 1ife, Newton set out a theory of light in which he claimed
to prove that white light resulted from the commingling of light rays of
various colors. As his notebooks show, Newton viewed these rays as being
composed of "globules," or corpuscles,but when he published the results
of his investigations, he was even more careful than Mendel had been
in avoiding reference to the theoletical entities which he was postulating.
I{e dicl, however, claim to have performed a crucial experiment which
had refuted the currently popular optical theories,including Robert Flooke's
undulation theory. The numerous letters published in reply to Newton's
optical theory had one thing in common-they called it a "hypothesis'"
The polemics that ensued clearly reveal a systematic ambiguity in the term
which was still prevelant in Darwin's day and which continues down to
the present. In the case of Newton, Ignatius Gaston Pardies, a professor
1 2 .A p r i l 2 0 , 1 8 6 0 M
, o r e L e t t e r s( 1 9 0 3 ) , 1 : 1 8 4 .
13. February23, 1860,Lile andLetters(lBB7),2:83-84.
+6
Occult Qualities
Darwin and His Critics
of mathematics, began his letter by referring to Newton's ingenious hypothesis concerning light. Newton replied in a model of overkill:
I do not take it amiss that the Rev. Father calls my theory an hypothesis, inasmuch as he was not acquainted with it. But my design was quite
different, for it seems to contain only certain properties of light, which,
now discovered, I think easy to be proved, and which if I had not
considered them as true, I would rather I'rave them rejected as vain
and empty speculation, than acknowledged even as an hypothesis.la
This terminological confusion was quickly cleared up. In his next letter'
Pardies apologized for his use of "hypothesis." It l.rad been done "without
any design, having only used that word as first occurring to me; and therefore request it may not be thought as done out of any disrespect."ls "Hypothesis" had been used to mean "whatever is explained in philosophy."
Newton accepted Pardies' apology but went on to enunciate an additional
sense of the term "hypothesis." Even if hypotheses were only statements
concerning substanceswhich one might postulate as the causesof observable
phenomena, Newton was opposed to them. In his Optics he had provided
the laws which governed the behavior of light, regardless of whether it
*,vasmade up of particles, waves, or something else. Scientistsdid not speculate about things they could not prove. Similarly, in his Principia, Newton
believed that he had provided the laws which governed the movements
ol material bodies. His reply to those scientists who wanted to know the
nature of gravity was the same as he had made to those who had wanted
him to speculateabout the nature of light:
It is certainly true that no theory can explain everything. Certain features
will ah.vays,Ior a time, have to be assumed.But Newton's contemporaries
rvanted to know what kind of considerations led Newton and might lead
them to accept gravity. Gravity really exists, but what is it that exists?
\\'hat chalacteristics might it have in addition to those necessitatedby
its role in the theory? Although these were precisely the questions which '
Newton asked himself, he objected to them when asked by others. He
nanted to limit public debate just to those propositions "deduced from
the phenomena." A more problematic phrase is hard to imagine, though
it ',vasto become commonplace in the literature.l? Deduction in the strict
renseis a necessaryinference, to be contrasted with induction. To deduce
somethingfrom the phenomena sometimes meant that it was observed (no
formal inference being involvecl) or that it was inferred from observations
{induction in the broad sense). In what sensehad Newton deduced his
ol)ticai and gravitational laws from the phenomena? He had hardly obsened either the various colored light rays in white light (though he had
seenthe diffracted spectrum when white light was passedthrough a prism)
or gravity (though he had seen bodies move in certain paths and at certain
t'elocities). From these observations in the context of his general beliefs
about the makeup of the universe, lte was able to infer his laws. This
inference. however. fitted none of the models of induction set out in his
da1'. In short, Newton would have been hard put to distinguish between
his laws, which had been deduced from the phenomena, and physical hypothesesabout mechanical qualities, since at best these were precisely what
his laws were.
So far I have explained the phenomena of the heavens and of the
sea by the force of gravity, but f have not yet assigned the cause of
gravity
I have yet been able to deduce from the phenomena the
reasons for these properties of gravity and I invent no hypotheses.For
everything u'hich is not deduced from the phenomena should be called
an hypothesis, and hypotheses,whether metaphysical or physical, whether
of occult qualities or rnechanical, have no place in experimental phiiosophy. In this philosophy propositions are deduced from the phenomena
and rendered general by induction. It is thus we have come to l<now
tlre impenetrability, the mobility, the impetus of bodies and the laws
of motion and of gravity. It is enough that gravity really exists, that
it acts according to the laws we have set out and that it sufEcesfor
' all the movements of the heavenly bodies and of the sea.16
1 4 . N e w t o n ( 1 9 5 8 ) ,p . 9 2 .
1 5 . I b i d . ,p . 1 0 5 .
1 6 . N e w t o n( i 9 6 0 ) , p . 5 4 7 .
Newton hated to admit that certain of his plinciples were physical hypothesesabout mechanical qualities, but his critics, especially in France,
went so far as to accuse him of introducing into science metaphysical hypothesesabout occult qualities. Cartesians such as Leibnitz tirelessly reminded him that gravity looked very much like such occult qualities as
syrnpathy, antipathy, attraction, and hostility, the very kinds of qualities
which Newton wished to exclude from science. In his eulogy to Newton,
the situation as follows:
Fontenelleassessed
l7- For example,I-Ierschel(1841:179) claimsthat perceptionis pirilosophical
deductionfrom experiment;CharlesBabbage(lB3?:57), speakso[ an observor
dcducing a law from an induction of a hundred million instances; James Clerk
Maxrvell (1890) claimed that his law of the distribution of electricity on the sttrface
ol conductors was analytically deduced from experiment; and see the titlc of Lyell
rl85i).
4B
Darwin and His Critics
I-Ie declares very freely that rre lays down this attraction, onlv as a
cause which he knows not, and whose effects he only considers,.oäpu.",
and calculates; and in order to avoid the reproach of reviving'the öccult
qualities of the schoolrren, he says, that ie establishesnoie but such
Qualities as are rnanif est and very visible by their phenomena, but that
the causes of these Quarities are indeed occult, a;d that h.' leaves it
to the other Philosophersto searchinto them.rs
But the Scl-roolmenalso claimed that their qualities were manifest. After
all, what is more ma'ifest than the hot and the cold, the dry and the
moist? In fact, of course, the technical terms .,hotr,' .,moist," and so on,
I'rad lost their original experiential connotations, but so had the notion
of force in Newtonian theory. It rrad little to do with the feerins one
gets when lifting a heavy object.
The feature of Newton's gravitational theory which i-ris contemporaries
found most objectionable was its apparent reliance on action at a clistance.
Gravity acted instantaneously in the abser-rceof contact throughout all
space.one way to eliminate such a counter-intuitive notion was to postulate
a universal ether per-vading all space. prior to Newton, scientistshacl frequently postulated subtle fluids to explain natural phenomena, especially
in biology, but such fluids were lookecl upon with some clegreeof suspicion.
with the tremendous successof Newton's theory, the postulation of subtle
fluids as explanatory principles became respectabre. For instance, in his
review of the origin included in this volume, Flopkins justifies Lamarck,s
vital fluids by comparing them with the luminiferous ether. Thus, Newton
contributed unwittingly to two opposing trends in science-the rigid, overly
restrictive, ultra-empirical inductive method and the almost unlicensed introduction of subtle Iluids.le
There was a diflerence betwee' the occurt qualities of trre schoolmen
and Newton's light corpuscles and gravity, and it was the difference which
Newton himself pointed out, but for different reasons. when attacked,
Newton retreated to mathematics. He invented no hypotheses.He offer.ed
no mecha'isms. He simply supplied the equations which accounted
for
various phenomena rnathematically. (A similar retreat has occurred in this
century in quantum mechanics.) Newton need not have retreated.
Because
he could and did provide laws which accuratery accounted for a
wide
nange of phenomena with a greater degree of accuracy then any previous
theory, there was good reason to believe in the existence of the postulated
l B . N e w t o n ( 1 9 5 8 ) ,p . 4 6 3 .
1 9 . S e eT h o m a sL l a l t ( 1 9 6 8 ) .
Occult Qualities
+9
rntities and qualities and to attribute to them the characteristicsthe theory
required.
postulate anything which
Justified or not, Newton did not like to have to
this
score, Darwin was at
On
quality.
occult
an
even slightly resembled
new lorces or subno
to
postulate
had
Darwin
a considerable advantage.
consequences"
inevitable,
the
almost
possible,
slances.FIe merely showed the
vary
Offspring
world.
organic
the
of fairly common observations about
proare
offspring
More
parents'
sliglitly from each other and from their
duced than can survive. It is reasonable to expect differential mortality
as a lunction of these variations. And so on. Darwin introduced nothing
that fainrly approached an occult quality, metapirysicalentity, or vital force.
Although an occasional author with extreme effort was able to read his
relerencesto natural selection as a reificatiou of Nature selecting,Darwin's
tlieory was purely naturalistic.20
when Dar.win,s critics objected to his evolutionary theory as hypotheticai
and speculative, they had in mind three features of his formulation: (1)
evolution occurring so slowly that no one had observed or was likely to
observeone speciesevolving into another; (2) the initial spontaneousorigin
of life being in the distanr past and unknowable; and (3) Darwin's uncautious assertion that aII specieshad evolved and most likely from a single
ionn.
Darwin grew weary of telling people that he did dot pretend to address
clirect evidence of one species changing into another. Among those rvho
contributed most to Darwin's wearinesswas Huxley. Throughout their collaborarion, I{uxley steadfastly maintained that intersterilitv infallibly distinguished speciesand "until selective breeding is definitely proved to give
rise to varieties intersterile with one another, the logical foundation of
the theory of natural selection is incomplete."2l Dalwin believed, on the
other hand, that it was clifficult "to make a marked line of separation
between fertiie and infertile crosses."t' Moreover, those groups distinguis|ed
by constant characters did not always coincide with those distinguished
by sterility. As the years went by Darwin bccame resigned to the
disagreement:
I did not understand what you required about sterility: assuredly the
facts given do not go nearly so far. We dif{er so much that it is no
,s" urltritg. To get ih" d.gt." of sterility you exPect in recently formed
20. See, for example,the review by Wollaston included in this volume'
2 1 . H r r x l e y( 1 8 9 6 ) ,P . v i .
, o r e L e t t e r s( 1 9 0 3 ) ' 1 : 1 6 6 '
2 2 . A u g u s ti , 1 8 6 0M
50
Darwin and I{is Critics
Occult Qualities
varieties seems to me simply hopeless. It seems to be almost like those
naturalists who declare they will never believe that one species turns
into another till they seeevery stage in the process.23
You will say Go to the Devil and hold vour tongue. No, I will nor
_
hold my tongue; for I must add that after going, for my present book,
all through domestic animals, r have come to the conclusion trrat there
are almost certainly several casesof two or three or more speciesblended
together and now perfectly fertile together.2a
You are so terribly sharp-sighted ancl so confoundly honest! But to
tiie day of my death I will always maintain that you have been too
sharp-sighted on hybridism.,5
Two points are at issue in the preceding quotations: the scientific issue
of the sufllciency of sterility as a criterion for speciessratus and the philosophical question concerning the need for direct confirmation of theories.
we cannot treat the scientific question here, since the literature is volumi"
nous. All that can be mentioned is that one of the cornerstones of the
synthetic theory of evolution is the biological definition of "species" in
terms of interbreeding, potential interbreeding, and reproductive isolation.2.
Darwin argued against intersterility as a criterion for species status and
for the constancy of characters. Modern evolutionists argue against the c'terion of constancy of characters and for reproductive isoration (which
in several important respectsis different from intersterility).2,
The question that interests us here, however, is whether or not Huxley
was justified in requiring direct evidence of evolutio' by natural selection
before accepting the theory without reservation. Either Huxley is wrong
in his views on the relation between direct evidence and proof or eise
the majority of scientists have been mistal<e' throughout the history of
science. scientific theories are accepted long before anything iike direct
proof is provided. For example, when copernicus enunciated rris heiiocentric system, scientistsimmediately selected the observation of stellar parallax
as the most sig'ificant test of the theory. None was observed until the
1830's-1ong after all reasonable men had accepted the heliocentric system.
2 3 . D e c e m b e2r 8 , 1 8 6 2 ,i b i d . , 1 : 2 2 5 .
2 4 . l a n u a r y1 0 , 1 8 6 3 M
, o r e L e t t e r s( 1 9 0 3 ) ,1 : 2 3 2 .
25. January30, 1868,ibid., 1:287.
26. Mayr (1963).
27. For further discussion,see the cornmentson the papers by Wollastonand
Fawcett in this volume. Darwin mentioned isolation in the'origin' (1859:105) but
Iater largelv ignored it. Not so Mayr (1963). peter vorzimm"e,
itozol Jiräurr",
these issuesin his book on Darwin.
/.,dr_i'r\qgir*\
\n
,r'1,.; I 1;1;1;1it,1..\'1.5
i ui,EfdfJlllllilt
, not untii recently has anything like the observation of the evoluof new speciesof muiticellular organisms been observed. (The developof speciesby polyploidy has been observed on occasi.on,but this is
a Darwinian method of evolution, and the evolution of new species
:bacteria is commonpiace.) Yet, few reasonable merr withheld consent
itlu theory that species have evolved and that -natural selection is the
icf {if uot the only) mechanism involved.
or example, even in Darwin's own day, F. J. Pictet contended in his
of the Origin of Species (1860) that he would not accept Darwin's
dtductions until he saw for himself the evoiution of a new organ' By 1864
t had been converted and in 1866 published a paper in support of
ionary Lheory (Pictet and Humbert, 1866). Needlessto say, the direct
he required had not been supplied. Instead, he had been convinced
ttry the numerous indirect proofs of evolutionary theory. On this score special
n and evolution by natural selection were on different footings. No
ftra seen a new speciesevolve anymore than they had seen.onespecially
but unlike the special creationists,Darwin had presented a mechafor evolution. Certain implications of his theory could be checked
:rana lis theory as a whole gradually confirmed or disconfirmed without
i,rbe direct observation of speciesevolving. Special creation was little more
i;i"
,than a bald assertion. Whether as a natural event lacking any scientific
eiplanation or as a supernatural event, special creation could be checked
,Qälyby direct obseiwation. As Darwin was to discover in his attempts to
lesswell-organized
.q1gueagainst the "theory" of speciai creation, ib was even
,thanAristotle's doctrine of polar principles and humors.
i, ,Confirmation of a scientific theory by reasonably direct means is always
, welcome,but such confirmation comes long after the theory has been establiuhedbeyond all reasonabledoubt. Empiricists had performed a worthwhile
s*n'ice in emphasizing the continuing role of experience in science, but,
i ar l{erschei obserwed: "Some things we come to believe not through obserl'v:ltion but by demonstration-speed of light, action at a distance in gravity,
the size of the sun, etc."'E As this list indicates, the things we come to
believe thr"ough demonstration, or indirect proof, are a mixed bag. The
dilficultl, lies in distinguishing between theoretical entities and those that
lack any empirical referents. If the issues had been more clearly drawn
at the time, it would have been dificult for Darwin's critics to charge
that natural selection was other than observable-as observable as a phenomenon can get. The situation was somewhat more equivocal with resPect
28. Herschel(1830), pp. 23-24.
t:
52
Darwin and FIis Critics
Occult Qualities
to the initial spontaneous generation of living creatures from nonliving
su!512n6s5-lut not very.
Before Dar-win, the common ploy in dealing with the origin of
by natural or supernatural means was to dismiss the question as
with events that occurred too long in the past ever to be known.
scientists wexe free to believe as they saw fit, and they generally
tion and extinction of the past and present inhabitants of the world should
have been due to secondary causes,like those deterrnining the birth and
species
dealing
I{ence,
saw fit
to believe in accordance with revealed religion. "The mystery of creation
is not within the legitimate territory of science." Theology must be assiduously excluded from the dynamical sciences but was a necessary adjunct
to the historical sciences,es
Darwin was presented with a dilemma. The currentiy popular doctrine
of the miraculous creation of species,a flashing together of elemental atoms
into fully formed plants and animals, ran counter to the naturalistic tenor
of evolutionary theory and its author.3o He maintained that if he were
forced to introduce "new powers" or "principle of improvement," he would
reject his theory of natural selection as "rubbish."sl Darwin felt himself
$r
il
$'
N
N.
i
il
I
li
I
i,
committed to a naturalistic explanation of the initial origin of species. !
Ile had none. To make matters worse, the naturalistic explanation for ii
s
the origin of life, the spontaneous generation of life, had a decidedly bad f,
reputation in scientific circles.s2The spontaneousgeneration of multicellular
organisms had been disproved after years of laborious effort, just in time
for its advocates to switch their allegiance to microbes. It was Darwin's
il
i.,
i
misfortune to propose his theory of evolution, which seemed to necessitate
il
the spontaneous generation of the original forms of life, at the same tirne
that Pasteul was beginning to route spontaneous generation from its last
t'
refuge. "All life comes from pre-existing life" was the popular dictum. i:
In the Origin Darwin bowed to protocol and referred to the first creation i,
i
of lile by means of a supernatural metaphor. "There is a grandeur in
this view of life, with its several powers, having been originally breathed
into a few forms or into one."33 Later he added, "by the Creator.', Such
a reference to the diety, however, did not necessarily commit Darwin to
a miraculous creation of life. "To my mind it accords better with what
we know of the laws impressed on matter by the Creator, that the produc29. Whewell ( 1840), 3:639; see also Wollaston,s
review in this volume.
30. For evidence that this was the tacitly accepted view, see Carpenter, I{ooirer,
Wollaston, and Fawcett in this volrrme.
31. Darwin, Lile and Letters (1887), 2:6; see also Darwin
(i859),
p. a09.
pictet, Sedgwick, Owen, and
32. See, for example,
the papers by Wollaston,
.
Agassiz in this volume.
33. Darwin
(1859), p. 490.
53
I
l
I
i
i
death of the individual."sa In this opinion Darwin agreed with the leading
authorities of the day. With one or two exceptions, the author of every
review in this collection concurred with this view of God_as acting through
exceptionlesslaws, not by rniraculous special creations. Even so, Darwin
was unhappy that he had gone so far and wrote to Hooker, "But I have
long regretted that I truckled to public opinion, and used the Pentateuchal
term of creation, by which I really meant cappeared' by some wholly unknown process."35
Darwin was never to resolve this dilemma, but there is little doubt as
to which alternative he preferred. As iate as 1870, he can be found saying:
Spontaneousgeneration seemsalmost as great a püzzle as preordination,
I cannot persuade myself that such a multiplicity o{ organisms can have
been produced, like crystals, in Bastian's solutions of the same kind. I
am astonished that, as yet, I have met with no allusion to Wyman's
positive statement that if the solutions are boiled for five hours no organisms appear; yet, if my memory servesme, the solution when opened
to air immediately becomesstocked. Against all evidence, I cannot avoid
suspecting that organic particles (my gemmules from the separate cells
of the lower organisms!) will keep alive and afterwards multiply under
proper conditions.
What an interesting problem it is.36
It is frequently argued that evolutionary theory was wasted motion unless
Darwin could also show how the first forms of life originated. In his defense,
Darwin once again sought refuge in the authority of Newton:
[Bronn] seems to think that till it can bö shown how iife arises it
is no good showing how the forms of life arise. This seemsto me about
as logical ' (comparing very great things with little) as to say it was
no use in Newton showing the laws of attraction of gravity and the
consequent movement of the planets, because he could not show what
the attraction of gravity is.37
In this instance Darwin's defense is apt. Newton, like Darwin, felt that
he had accomplisheci something by his theory even though he had left
somequestionsunanswered; e.g., questionsconcerning the nature of light and
the cause of gravity, It is interesting to note that Mill, at least, agreed with
34. Ibid., p. 48B.
35. March 29, 1863,Life and Letters(1887),2:202-203.
, o r e L e t t e r s( 1 9 0 3 ) ,l : 3 2 1 .
3 6 . J u l y 1 2 , 1 8 7 0M
37. February18, 1860,ibid., 1:i40-141.
I
I
54
Darwin and His Critics
Darwin, saying, "I do not think it an objection that levolutionary theory]
does not, even hypothetically, resolve the question of the first origin of life,
any more than it is an objection to chemistry that it cannot analyse beyond
a certain number of simple or elementary substances."3s
Newton was condemned for not stating explicitly certain assumptions
of his theory. Darwin was condemned for doing just the opposite (by Hop.
kins, for example) . Darwin answered that "though perhaps it would have
4'Teleology
been more prudent not to have put it in, I would not strike it out, as
it seemed to me probable, and I give it on no other grounds."se Here
was Darwin's sin: he had not exercised enough caution. Science must be
safe. The inductive method was calculated to make it safe. Many scientists
were willing to admit that varieties may have arisen through natural selec.
tion, but one must not carry things too far. These varieties never strayed
from the confines of their species (Pictet). Or perhaps, as Forbes and
Teleology had been part of the conceptual frameworh of Western science
from ancient Greece until the time of Darwin. Natural phenomena might
be governed by scientific laws, but it was the Creator who had instituted
ii:i them. Galileo and Newton replaced ono physical theory with another, but
others suggested, there were several centers of creation, and then dispersal, irrr
they lelt the teleologicai world-picture intact. The findings of paleontologists
but no evolution beyond certain bounds-say, the generic level. Like Tycho
" and geologistshad necessitateda reinterpretation of Genesis. But it was
Brahe's compromise between the geocentric and heliocentric systems,in
lt Darrvin who finally forced scientists to realize just how trivial teleology
which the sun revolved arouncl the earth while all the other known planets
had become in their hands. The change in scientific thought marked by
revolved around the sun, hybrid systems like Forbes's failed to gain wide.
the appearanceof the Origin of Specieswas so fundamental that it certainly
spread acceptance. There was considerable wishful oratory about moderatiorr$$',
the title of a conceptual revolution. The problems which arose
deserves
in all things-a little bit of evolution tempered u'ith a little bit of specials.\,
$]l
Irorn speciesevolvine will be discussedin the next chapter. In this chapter
creation, a little bit of natural selection and a little bit of divine guidrve will be concerned with the difFculty which scientistshad in reconciling
ance-but at bottom the two positions were incompatible. As soon as a
$^ their belief that the order in the world must be in some senseteleological
natural explanation was achnowledged for the origin and evolution of some
with their grorving awareness that the only sense in which it could be
species,nothing but time stood in the way of extending it to all species,
termed teleologicalwas a trivial one.
Conversely, as soon as a supernatural explanation was allowed for the origin
of some species, there was nothing to prevent a supernatural explanation
Teleology,the belief that things in the empirical world "strive" to attain
being given for all species.Unlike Wallace, Darwin insisted on telling a
är.' ends, is one of the most influential and misunderstood doctrines in the
totally consistentnaturalistic story or none at all.
$f' history of philosophy. In one interpretation, teleology entails a universal
3 8 . M i l l ( 1 9 1 0 ) ,2 : 1 B l ; s e ea l s oF a w c e titn t h i sv o l u m e .
c.onscious
being ordering everything for the best. As Plato Put it: "I heard
39. December
25, 1859,Lile and Letters(1887),2:46.
some one reading, as he said, from a book of Anaxagoras, that mind was
u
r'
$
$'
Hr',
K
$i
$,
$r''
fr
the disposer and cause of all, and I was delighted at this notion, which
appeared quite admirable, and I said to myself: if mind is the disposer,
mind will dispose all for the best, and put each particular in the best
$'
place."1
For the Platonic doctrine of external teleology, Aristotle substituted the
subtler view of immanent teleology. For Aristotle the ends were internal
$'
{.,'
il'
lil[:
f..
fi
I. Plato.Plnedo.St. 96-99.
56
Dalwin and His Critics
to the subject' Individuals did what
was best for themselvesby themselves.
Every natural kind (or species) had
a static, immutable essenceas rts
formal cause' These essencesmade
a thing.lvhat it ,"vas.These essences
iu
turn also serwed as final and efficient
causes. The end toward which a'
things strove was to realize their olvn
essenceas fully as possible. ,,[For]
any living thing that has reached its
normar development and which rs
unmutilated, and whose mode of generation
is not spontaneous,the most
natural act is the production of another
like itserf, an animal producing
an animal, a plant a plant, in order that,
as far as its nature allows, it may
partake in the eternal and divine.
Trrat is the goal towards wrrich aI things
strive, that for the sake of which they
do *h]tsoerrer trreir nature renders
possible."z
Both of these versions of teleology
can be interpreted to be exciting,
substantive claims about the empirical
world. In these interpretations they
have been shown to be untenable. For
example, accordin.gto external teleology, given a knowledee of the orde'ing
mind, one should be abre to infer
rvl-rat tl-re empirical world must be rike,
ancl conversery,given knowledge
of the e'rpirical world, one should be
abre to infer the crraracter of the
ordering mi'd. If the universe is a perfectly
running mechanism rvith a place
for everything and everything in its place,
rhen one type of mind is implied.
If it is a shoddily constructecrmechanism
which needs constant tinkering,
another type of mind is implied. what
externar tereologistsdid not rike
about evolutionary theory was the type
of mind it irnplied. God coulcl
have constructed the worlcl so that
species evolved by natural selection
in the struggle for existence, bur
that ki'd of God dicl not seem especialry
worthy of love and veneration. Evolutionary
theory had even more devastating consequencesfor immanent tereorogy.
If essencesare static and if in
general the goal toward whicrr all things
strive is to realize their esserrce,
then the wholesale progressive change
entailed by evorutionary theory is
impossible. If evolution has occurred,
then either essencesare not static
or else things must strive, not to furfilr
their own essence,but the essence
of some other species.
Both versions of tereology also have
more sophisticated interpretations,
but with these interpretations they become
vacuous. An advocate of external
teleology might be led to say that
whatever the larvs of nature turn out
to be' God did it' He never suspends
these laws in divine intervention,
and these laws reveal nothing of his
character. An advocate of immanent
teleology might assert that all it takes
for the worrd to be teleolosical
2. Aristotle,De Anima, 415" 26.
Teleology
i ,il for regularitiesto exist. The emptinessof thesepositionsis all too apparent,
.".but they were the positions to which the proponents of teleology were
at last driven. Darwin's theory was one of the chief instruments in the
'
final trivialization of teleology.
Thanks largely to the efforts of Thomas Aquinas, Aristor_elian metaphysics,physics,and natural history were incorporated into Church dogma.
Tlrrough the years, however, Aristotle's metaphysics took on a decidedly
' Platonic caste. God was not merely a detached, impersonal first and final
. . cause.but an overseerwho actively participated in the affairs of the world.
He both instituted the laws of nature and periodically suspended them
in miracles. Copernicus and Galileo had to combat the Aristotelian physics
of natural place, but they did not attack either the metaphysicsor theology
of.Church doctrine. God still instituted the laws of physics and still suspended them on occasion, but these laws were the laws of Newton, not
Aristotle. But of even greater significaflce, Newton's laws required the continued and continuing efforts of God in their operation. Newton was anxious
to reconcile physics with theology, and his instrument was Richard Bentley
(1662-17+2).3
Bentley did for Newtonian physics what Aquinas had done for the physics
of Aristotle. In "A Confutation of Atheism from the Origin and Frame
of the World" (1693), he argued that Newtonian physics was not only
compatible with the existence of God but also necessitatedit. Bentley's
arguments all follow the sarne format. Certain phenomena were derivable
Irom Newtort's laws, e.g., the earth traveling around the sun in an ellipse.
Other phenomena were not derivable from Newton's laws, e.g., the sun
bcing luminiforous and the other bodies in the solar system opaque, the
distancesof the various planets from the sun, and the inclination of the
earth's axis of rotation to its plane of revolution. Now that Aristotle's physics
of natural place had been abandoned, these phenomena had no explanation
in terms of natural law. They had no secondary causes. They appeared
to be "accidental" features of the universe. Yet they had to be precisely
as they were in order for the earth to support life. If the earth were
farther away from the sun, then it would be too cold to supPort life. If
nearer, it would be too hot. If the earth's path had been more elliptical,
the extremes in temperatur-eon earth as it revolved around the sun would
be too great. If the earth's axis had not been inclined to the plane of
its orbit, parts of the earth would be too hot to support life and others
too cold. If the earth revolved around the sun more slowly, the seasons
3. Lilre Whewell,BentleywasMasterof Trinity College,Cambridge(1700-1742).
58
59
Darwin and His Critics
Teleology
would be too long. If rnore quickly, too short. And so on. All these phenomena had to be as they were if life-- especially man-was to exist. Their.
disposition did not follow fi'om Newton's laws. Flence, either they occurred
As Aristotle observed, instead of organisms' being so well-organized and
rveli-adaptedbecauseit was of their essenceto be so, "such things survived,
being organized spontaneouslyin a fitting way; whereas those which grew
by accident or else God did it. The chance coincidence of so many phenomena was extremely implausible. Flence, God was responsible. The existence of life was good. I{ence, God was good.
otherwiseperished and continue to perish." Aristotle immediately dismisses
such a ridiculous contention. "Yet it is impossible that this should be the
tlue view. For teeth and other material things either universally or nolmallycome about in a given way; but of not one of the results of chance or
spontaneity is this true."? Whenever anything occurs regularly, it must be
becausethe formal and final causescoincide. Because an organism is what
This Neoplatonic world-view was to find favor among such biologists
as Cuvier, Owen, Agassiz, and von Baer. Space was God's sensorium, gravity his consciouswill, and each speciesa divine thought. Even an empiricist
like Flerschel concurred in this ontology, hoping to combat the more radical
empiricism of Locke and Hume and the materialism of Laplace. According
to llerschel, falling bodies are urged .to the earth's surface ,,by a force or
it is, it produces teeth as they should be. The haphazard production of
numerous alternatives and the elimination of those that are not fit occur
too irregularly to be part of the natural order.
An identical story can be told for William Whewell, with one minor
complication. FIe somehow had to reconcile his own advocacy of final causes
with Bacon's "barren virgin" quip. Whewell's solution was to argue that
final causes should be excluded from physical inquiry but were perfectly
legitimate as the results of such inquiry. Final causeswere barren because
effort, the direct or indirect result of a consciousnessand a zolll existing
someu,tlzere,though beyond our power to trace, which force we term
grauity."l
In his Bridgewater Treatise, Whewell updated Bentley's arguments for
God's existence. In reading I{erbert Mayo's The Philosolthy o.f the Liuing
(1838), Darwin was incensed over Mayo's contention that Whewell was
they themselves were the fruits of the labor.s God ordered the universe
according to his divine plan, and it .was the goal öf science to discover
this plan. Any explanation in terms of the perishing of the unfit and the
survival of the fit was inconceivable:
profound "because he says length of days adapted to duration of sleep
of man!!! whole universe so adapted!!! and not men to Planets.-instance
of arrogance!!"5 The Bridgewater Treatises were published because scientists had been gaining the reputation of being materialists, determinists,
If the objector were to suppose that plants were orginally fitted to
yeals of various lengths, and that such only have survived to the present
time, as had a cycle of a length equal to our present year, or one which
could be accommodated to it; we should reply, that the assumption
is too gratuitous and extravagant to require much consideration.e
and atheists, especially in France with the workl of D'Alembert, Diderot,
de la Mettrie, Laplace, and Voltaire. Whewell was pleased to do rvhat
he could to combat the growing slander by showing the mutual dependence
of science and religion. "My prescribed object is to lead the friends of
religion to look with confidence and pleasure on the progress of the physical
sciences,by showing how admirably every advance in our knowledge of
the universe harmonizes with the belief of a most wise and good God.',u
Periodically, proponents of teleology, whether of the immanent or tire
external variety, entertained a possible alternative explanation for the aoaptation of living creatures to their environments-the survival of the fit.
4. Herschel(1833), pp.221-222.
5 . D e B e e r( 1 9 6 0 ) ,p . 1 3 4 .
6. Whewell (1833), p. i; though Whewell'sBridgewarerTreatisewas Volume
III of this series, it was the first to appear in print. The complete title of this
series was TIte Bridgeuater Treatises on the Power, Wisdom and Goodness of God,
as
in the crcation. Dach contribution will be cited separately by the
-Manifested
title
of that volume. We have only a fragment of Charles Babbage,i (1S37) etror*
which does not form a part of the Bridgewater Treatises, even tho'gh it bears
the title The Ninth Bridgeuater Treatise.
Lilre a true philosopher, Whewell went on to hedge his bet. Even if adzptations did come about by such a gratuitous and extravagant mechanism,
"it does not remove the difficulty. Ifow came the functions of plants to
be periodical at all?"
I
Prior to the publication of the Origitt, philosophers and scientists had
some justification for rejecting nonteleological explanations of adaptation,
since there was no alternative explanation. Lamarck's theory came closest
to supplying a mechanism fol adaptation, but few were willing to accept
it, both because of its own weaknessesand becauseof the inordinate influence of Cuvier. After the Origin, however, the reactions of philosophers
7. Aristotle,Physics,
bk. II, ch. B.
B . W h e w e l l( 1 8 3 3 ) ,p . 1 8 0 .
9. Ibid.. p. 27.
60
6i
Darwin and l{is Critics
Teleology
and scientistswere not much different. Mill, inhisTlzree Essayson Religion
written during the decade following the publication of the Origin and
published posthumously in 1874, still found the argument from design preferable to evolution by natural selection:
Flerschel's position on these matters was typical. In his 1861 edition
of Physical Geography of tlte Globe, he added the following comment
on Darwin's theory:
I regret to say, however, that this latter half of the argument is not
so inexpugnable as the former half. Creative forethought is not absolutely
the only link by which the origin of the r,r'onderful mechanism of the
eye may be connected with the fact of sight. There is another connecting
link on which attention has been greatly fixed by recent speculations,
and the reality of which cannot be called into question, though its
adequacy to account for such truly admirable combinations as some of
those in Nature, is still and will probably long remain problematical.
This is the principle of "the survival of the fittest."
Mill continues:
Of this theory when pushed to this extreme point, all that can now
be said is that it is not so absurd as it looks, and that the analogies
which have been discovered in experience, favourable to its possibility,
far exceed what any one could have supposed beforehand. Whether it
wiil ever be possible to say more than this, is at present uncertain. The
theory if admitted r.r,ouldbe in no way whatever inconsistent with Creation. But it must be acknowledged that it would greatly attenuate the
evidence for it.ro
Darwin's arguments in the Origin are mere analogies,whereas the argument
from design r.r.asa genuine inductive argument. "In the present state of
our knowledge, the adaptions in Nature aflord a large balance of probability of creation by intelligence."
Many philosophers and scientists were willing to accept evolutionary
theory if only Darra'in u'ould admit divine providence. Without it they felt
trapped between inexorable law and blind chance. The terminology of this
position varied, but the messagewas always the same. Some maintained
that some phenomena were lawlgoverned, other lthenomena not. Others
maintained that ail phenomena r,r.erelaw-governed. In either case, God
instituted these laws and guidecl their action. A universe governed by divinely
instituted law did not seem so cold and barren. Add periodic mir-aclesand
the world-picture
became evell rnore intimate. Lxclude God, and both
accidental and larv-govemed phenomena bccame equally "accidental," given
the peculiar telminology of the time.11
1 0 . M i l l ( 1 9 6 9 ) ,p p . 1 7 2 ,1 7 4 .
11. For example, see the review
and Wright in this volume.
by von
Baer and
the exchange between
Mivart
This was written prior to the publication of Mr. Darwin's work on
the Origin of Species,a work which, whatever its merit or ingenuity, we.
cannot, however, consider as having disltroued the view taken in the
text. We can no more accept the principle of arbitrary and casual variation of natural selection as a sufficient condition, per se, of the past and
present organic world, than we can leceive the Laputan method of composing books (pushed ä outrance) as a suficient account of Shakespeare
and the Principia.t"
Herschel is repeating l-rischarge quoted earlier that Darwin's theory was
the law of higgledy-piggledy. Evolution by random variation and natural
selectiondid not exhibit the mathematical regularity and simplicity characteristic of physical law. The laws of physics wele worthy of God's authorship, just as Hamlet and Macbetlt were worthy of Shakespeareand the
Principia worthy of Newton. Darwin's theory implied a God who would
composea book by randomly striking the keys of a -typewriter until something turned out. Herschel did not want to deny that evoiution might
occur by law, but it had to be a la'w worthy of God.
Equally in either case, an intelligence, guided by a purpose, must be continually in action to bias the directions of the stepsof change-to regulate
their amount-to limit their divergence-and to continue them in a definite
course. We do not believe that Mr. Darwin means to deny the necessity
of such intelligent direction. But it does not, so lar as we can see, enter
into the formula of this law; and without it we are unable to conceive
how far the law can have led to the results. On the other hand, we
do not mean to deny that such intelligence may act according to a law
(that is to say, on a preconceived and definite plan). Such law, stated
in words, wouid be no other than the actual observed law of organic
succession;or one more general, taking the fonn when applied to our
own planet, and including all the links of the chain which have disappeared. But the one lalv is a necessarysupplernent to the other, and
ought, in all logical propriety, to form a part of its enunciation. Gr-anting
this, and with some demur as to the genesis of man, we are far from
disposed to repudiate the view taken of this mysterious subject in Mr.
Dar-r.r,in'sboolc.13
12. Flerschel (1861), p. 12; see von Baer's review in this volume for an expansion
on this reference to Gulliuer's TraaeLs.
13. Iferschel (1861), p. 12.
62
Teleology
Dar-lvin and His Critics
believe that there is a bit more interference by the Ct'eator in the construction of each species than in the course of the planets. It is only
ou,ing to Paley and Co., I believe, that this more special interference
is thought necessary with living bodies. But wc shall never agree, so
clo r-rottrouble yourself to answer.1s
A quick reading of the preceding paragraph might lead the reader to
think tl.rat Flerschel is saying much more than he is. Herschel pleads for
a supplementation of Darwin's laws by some reference to intelligent dilection, but what does he suggest? A description of phylogeny! Darwin was
at a loss as to the manner in which he could reply to criticisms such
as these. The request for a law of divine providence could be taken literally,
Wlren you conre to "Deification," asli yoursclf honestly whethcr what
you are thinking applies to the endlessvariations of domestic productions,
rvhich man accurnulates for his mere fancy or use. No doubt these are
all causedby some unknown larv, but I cannot believe they were ordained
Ior any purpose, and if not so ordained under domesticity, I can see
no reason to believe that they were ordained in a state of nature' Of
course it may be said, when you l<ich a stone, or a leaf falls from a
tree, that it was ordained, before the foundations of the world were
laid. exactlv where that stone or leaf should lie. ln this sensethe subject
has no interest for me.16
in which case Darwin felt obligated to deny it. If God were all-good,
all-knowing, and all-powerful, then one would expect that organisms would
tend to vary in directions advantageous to their survival. Darwin found
no evidence o[ such directed variation. As far as Darwin could tell, variations were "chance," they occurred "in all directions." By .these claims
Darwin did not mean that variations w,ere uncäused. Rather he meant
that whatever laws governed variation, they were currently unknown and
to the best of Darwin's knowledge they were not teleological. That is,
there was no correlation between those variations which an organism might
need and those it would get. The God implied both by cvolution and
the current state of the organic world was capricious, cruel, arbitrary, wasteful, slipshod, and totally unconcerned with the welfare of his creations,
a god reminiscent of the Old Testament, not nineteenth century natural
theology.
I
$.
!
!
There seems to me too much misery in the world. I cannot persuade
myself that a beneficent and omnipotent God would have designedly
created the Ichneumonidae with the express intention of their feeding
within the living bodies of Caterpillars, or that a cat sl.rould play with
a mouse. Not believir-rg this, I see no necessity in the belief that the
eye was expressly designed.ln
One might argue that God moves in strange ways and that he is guiding
things, though we cannot discern his plan. I-Iowever species evoive, that
is the way he planned it. Darwin found this position empty verbiage. He
saw no reason to utter such pious inanities. No mention is made of intelligent direction in the formula of evolution by natural selection, but neither
did it enter into the formula of the law of universal gravitation. In a
series ol letters, Darwin tried, with little success,to make his position clear
to Lyell:
No astronomer, in showing how the movements of planets are due
to gravity, thinks it necessaryto say that the law of gravity was designed
that the planets should pursue the courses lvhich they pursue. I cannot
14. f)arwin,May 22, 1860,Lif e andLetters( 1BB7)2: 105.
63
lr
$
It
n
*
Will you honestly tell me 1o,.,i f should be really much obliged;
whether you believe that tl-re shape of my nose (eheu!) was ordained
and "guided by an intelligent cause"? By the selection of analogous and
less differences fanciers make almost generic dif{erencesin their pigeons;
and can yor.rsee any good reason why the natural'selection of analogous
individual diffelences should not tnalie a nerv sPecies?If you say thai
God ordained that at some time and place a dozen slight variations
should arise, and that one of thern alone should be preserved in the
stluggle for life and the other eleven should perish in the first or few
generations, then the saying seems to me mere verbiage. It comes to
merely saying that everything that is, is ordained.tt
At one tirne God had played an important role in physics,but gradually
his function had been eroded, until reference to him was little more than
pious honorifics. It is often said that evolutionary theory brought an end
to the practice of including God as a causal factor in scientific explanations'
A more accurate characterization is that it demonstrated forcefully that
this day had already passed.The architects of the clemiseof teleology were
not atheistic materialists but pious n-renlil<e Herschel, Whewell, and Mill,
rvho thought they were doing religion good service by limiting tl're domain
of the accidental and of the miraculous. To them the more the empirical
rvorld was shown to be governed by secondary causes acting according
to God-given laws, the more powerful and ominiscient God was shown
to be. With rare exception, every author included in this volume, whether
, o r e L e t t e r s( 1 9 0 3 ) ,l : 1 5 4 .
1 5 .J u n e1 7 ,1 8 6 0M
1 6 .A u g u s t1 3 , 1 8 6 1i,b i d . ,1 : 1 9 2 .
, o r e L e t t e r s( 1 9 0 3 ) ,1 : 1 9 3 .
1 7 .A u g u s t2 1 , 1 8 6 1 M
6+
in favor
Dalwin and I-Iis Critics
of evolutionary
theory or against it, strongly supported
of God's relation to natural
accidental,
put
had
be shown not to be accidentar, either beof God or by subsuming
made
thereby limiting
constant
God governing
"The
one which
the world
sistent, is the conception
Darwin
of
is inco'sistent
will.
with
on the relation
with
Tlie
one which
betwee'
from
scie'ce,
wheweil
of a
is conlaws.,,1s
science ancl religion
for his theory. He prefaced
quotations
of the
As Mill
is the conception
of a God governir-rg the r,vorld by invariable
to gain a fair hearing
the origin
them under law.
on the domain
of theism, one consiste't
by acts of variable
used this position
in an attempt
edition
inroads
the need for God's direct intervention.
it, there were two conceptions
one inconsistent.
this view
phenomena.
Accidental occurrences could
cause of the direct inter-vention
Pliysics since Ne*'ton
Teleology
and
the fir.st
Bacon
to the
shourd be placed in the path of scientific inquiry
because no larv could be discovered r.r'hich was contrary
to God's will. In
the sixth editiorr he added a third quotation to this same effect
by Bishop
Butler' All Darwin wanted to do was to extend the domain of secondary
effect that no irnpediment
causes to include the creation of species. Although in the past the
creation
of species had been considered miraculous and outside the realm of
lziw,
so had many other phenomena which had been shown to be law-governed.
Darwin
u'as acting within the currently acceptecl tradition of expanding
the realm of law.
wl'rewell
recognized
wanted
that
to retain
the creation
such an explanation
of species as miraculous
was not
a tenet of physical
but he
science
but of natural theology.rs wheu'ell's bare recognition that the origin
species was even susceptible to a naturalistiö explanatio'
gave heart
Lyell, who had pr-oved so uncharacteristically
timid on the evoiution
of
to
species' In a letter to I{erschel, he r,r,rote, "whewell,
in his excellent treatise
Sciences, aprlears to me to go nearly so far as to contemplate the possibility at least of the introcluction of fresh species
being gov-
erned by general laws."2o
There were those like sedgwick
and Agassiz who wished to retai'
to lend significance to their teleological clairrs. A majority
losophers and scientists, however, gradually abandoned the notion of
creation but still wished to retain teleology as a significant doctrine.
special
of phispecial
white-
head, Dewey, and Peirce all espoused creative evorution. walrace, Asa
Gray,
18. Mill (1969), p. 135.
19. Whewell (1837), 3:640.
2 0 . L y e l l , M a y 2 4 , 1 8 3 7 ,L i f e o l L y e l t ( l B B l ) , 2 : t Z ,
and Lyell belabored Darwin with argurnents for admitting divine provrdence, especially with respect to man's mental and moral faculties. For
exarirple,Lyell hailed Wallace's suggestion that "there be a Supreme Will
and Power which may not abdicate its function of interference but may
guide the forces and laws of Nature." What these men did not realize
ivas that by pushing God further and further in the background as the
unknowable author of natural 1aw, regardless of the nature of these 'laws,
they frad prepared the way for his total expulsion. Like l{ant's Ding an
rirlz, he was remote, obscure, unknowable, somehow underlying everything
and very important but of no conceivable consequenceto any endeavor.
'feleological supplements were as otiose to evolutionary theory as they were
to contemporary versions of Newtonian theory. The superficiality of teleological claims in a deterministic universe was not totally lost on the educated
public. For example, one writer observed with respect to tl-rehabit of naturalists to interpolate tl-reir writings with references to God: "It appears
to them that, unless they clrag the Creator into every second paragraph,
their essaywill not possessthe necessaryreligious veneering for the public
t;ste."21
Darwin was not impervious to the pathos in the dile-ttto which confronted his colleagues. Neither a world ruled by deterninistic laws nor
one in which chance played an important role seemed bearable. Even
though Darwin had not intended to write atheistically, his theory robbed
rhe traditional solution to this dilemma of all its plausibility. The closest
Danvin came to a resolution of the conflict between teleology and the
facts of natural history was his suggestion that God instituted the general
larvs,whereas the details were left to chance:
of
on the Inductive
creation
65
My theology is a simple muddle; f cannot lool< at the universe as
the result of ülind chance, yet I can see no evidence of beneficent design,
or indeecl of design o[ any ]<ind, in the details. As for each variation
that has ever occurrecl having been preordained for a special end, I
can no more believe in it than that the spot on which each drop of
rain falls has been specially ordained.22
On the other hand, I cannot anyhow be content€d to view this wonderful universe, and especially the nature of man, and to conclude that
everything is the result of brute force. I am inclined to look at everything
as resulting from designed laws, with the details, whether good or bad,
2 1 . A n o n y r n o uP
s ,o p u l a rS c i e n ' cRee u i e w( 1 8 6 6 ) ,5 : 2 1 5 '
, o r e L e t t e r s( 1 9 0 3 ) ,1 : 3 2 1 .
2 2 . J u l y 1 2 , 1 8 7 0M
66
Dalwin
and His Critics
left to the working out of what we may call chance. Not that this
at all satisfr,esrrre.23
Bentley and whewell had argued that God had instituted natural
and taken care of the details. Darwin believed that perhaps God instituted
natural laws, but he could not be responsible for specific applications bot
because of their triviality in some cases and because of their cruelty i
others. But it should be recalled that by .,chance" Darwin meant
by laws not as yet known. Darwin,s solution was. a circuitous
of determinism. Interpreted realistically, teleology was incredible. Given
Essences
i.,
sufficiently sophisticated interpretation, it was of no relevance to science.2a
.teleology.permeated Western thought, essentialism was even more Per'
. The number and variety of metaphysical systems generated on the
and in England was staggering. Realists maintained that the
existed in nature, perhaps in individuals thernselves (Aris) , or both in nature and in the mind of the creator (Neoplatonists) .
ts süch as Cuvier, Owen, and Agassiz are often referred to
23. Darwin, May.22, 1860,Lile and Letters (1g87). 2:10524. The issr.reof teleology has had a recent ."r,,.jer"" brrt in entirely different
terris. several
and biologists have attempted to analyze ieleological
-philosophers
systems
_naturalistically in terms of genetic pl.ograms, negative feedbacL, urä so
o n . S e eM a y r ( 1 9 6 1 ) a n d C a n f i e l d ( 1 9 6 6 ) .
flidealists" in this respect, but the term is not very apt. Idealism is
contrasted with materialism, idealists maintaining that only ideas
(material objects are just clusters of ideas), and materialists maini.ng that only matter exists (minds are merely brain processes). Although
i:
and Darwin.might legitimately be called materialists, Cuvier, Owen,
i:Agassiz were hardly idealists in this sense. Rather they were iderilists
i,'tbesense that they tended to explain the order in nature by reference
..ideal types. In short, they wefe essentialists. As metaphysically aloof
öminalists might be, they too were strongly predisposed to essentialism.
iduals were the only independent existences. A scientist could divide
iduals into classes as he pleased-just so long as these classes were
iete. Nominalists were as much essentialists as the Aristotelians and
ists, but witlout their metaphysical justification.
dichotomy cuts across the preceding distinctions.
empiricist-rationalist
rfihe
iricists maintained that all knowledge had its source in experience
could be analyzed completely in terms of it. Rationalists rnaintained
that sense experience played no role in the acquisition of knowledge
else that truth could not be decided completely by reference to sense
ience. The mind played an.active role. As'one might expect, empiricists
d to be nominalists and materialists, whereas rationalists were frey disposed to idealism, though numerous excePtions can be found
iio both generalizations. In this chapter, the effect of these metaphysicai
ions on the acceptance of evolutionary theory will be traced.
69
Darwin and FIis Critics
Essences
Alvar Ellegärd (1957 and 1958) sees the disagreement over the immutability of species as a conflict between empiricist and "idealist" philosophies of science. Although our story would be much neater if this were
ls so
an unfathomable chasm . . The universe, so far as known to us'
of
cases
all
true
in
is
t$nstitlrtecl,that whatever is true in any one case,
I(inds
description'
a certain description; the only difficulty is, to find the
' '"3
are Classesbetween which there is an impassiblebalrier
'fhough Mill's empiricist ontology did not directly require the existence
proof
of discrete natural kincls, his logic of justification clid' At bottom,
E'
was suppiied by eliminative induction. "Either A, I), or C can cause
be
to
A ancl B are absent. Hence, C must cause E'" For this inference
specibe
must
event
of
l<ind
of
a
certain
causes
alternative
the
r.aiid, all of
of this
fred and all but one eliminatecl. As Darwin discovered in his use
elimination
actual
themselves-the
present
difficulties
type of argument, two
that
of the alternatives and their complete specification. The consequence
the
kinds
if
that
was
proof
of
notion
for
Mill's
et,olutionary theory had
not a
in question were species of plants 'and animals, then there were
elimiby
complete
Induction
kittds'
finite number of sharply distinguishable"
but
theory'
his
"prove"
not
Darwin
did
rlrtion \'vasimpossible. Not only
be
forever
would
proof
a
such
also, given evolution by gradual variation,
6B
true, it is not. Empiricists and "idealists," while not equally opposed to
the concept of species evolving, were stili both opposed. Evolution by random variation and natural selection conflicted with teleology. Any evolution
at all, regardless of the mechanism, as long as it is graduai, conflicted
with the essentialist notion of natural kinds-and on the necessityof such
natural kinds, empiricists and "idealists" were in agreement. The doctrine
of the existence of static, immutable natural kinds underlay ail of the prevrously discussedtopics-inductive proof, occult qualities, and teleology-and
evolutionary theory struch a strong blow against this doctrine.
One n-right expect Wheweil to argue for the existence of natural kinds,
since his metaphysics depended on it. In writing his History Whewell was
happy to discover that the most eminent physiologists of his day believed
that indefinite divergence from original type was impossible. "Species haae
a real existence in nature, and a transition from one to another does not
exist."l The impossibility of evolution-or transmutation, as it was usually
called-was not a generalization from experience for Whewell but a necessary prerequisite for knowledge. "Our persuasion that there must needs
be characteristic marks by which things can be defined in words, is founded
on the assumption of the necessarypossibility of reasoning."2 In Whewell's
view, if evolutionary theory were true, hnowledge was impossible-not a
small drawback to the theory. Peirce (1877) recognized that the "Darwinian
controversy is, in large part, a question of logic" and Dewey (1910) tliat
"the real significance of Darwinian evolution was to introduce a new 'mode
of thinking,' and thus to transform the 'logic of knowledge'."
Contrary to Ellegärd's belief, the empiricist philosophies of Herschel and
Mill both depended upon tlie existenceof discrete natural kinds. Mill dis.
tinguished between two types of uniformities in nature: those of succession
in time and those of coexistence. The former were expressed in causal
laws, the latter in definitions. Mill's four (sometimesfive) methods of induction were designed to discover succession of kinds of events in time, on
the assumption that these kinds had already been discovered.Mill concurred
in the essentialist position that natural kinds wele those classeswhich are
"distinguished by unknown multitudes of properties and not solely by a
few determin2fs 6ns5-\a/hich are partitioned off from one another by
1 . W h e w e l l( 1 8 3 7 ) ,3 : 6 2 6 .
2 . W h e w e l l( 1 8 4 0 ) , 1 : 4 7 6 .
irnpossible.
reference to
Ltill lustinea his belief in the existence of causal laws by
inducjustified
enumerative
by
the larv of universal causation. It alone was
but
coexistence,
universal
of
tion. I{e could fir]d no justification for a law
biologists
eminent
most
the
he accepteclit anyway on the authority of
permitted
oi his clay. Mill's belief in a finite number of cliscrete kinds
also perIt
elimination'
hirn to retain his notion of induction by complete
The
form.
in
universal
nritted him to maintain that all causal laws were
a
was
form
in
onlv reason for a causal law to be less than universal
had
kinds
natural
iailure to distinguish natural kinds accurately' Once
immutable
beenaccurately distinguished, universality was guaranteed' Thus'
Whewell's'
to
were as central to Mill's philosophy as they were
essences
induction
Whewell was quick to point out that Mill's four methods of
the
discover'
difficult to
"take for granted the very thing which is most
interpretarerluction of phenomena to formulae'" Induction, in Whewell's
were
tion, provided these formulae. Whewell believed that observations
not think that
necessaryfor scientific knowledge. Though Whewell did
that they were
the lundamental ideas of science were innate, he dicl think
progress of
the
in
but
facts,
as
observed
out
necessary.They might start
necessary
As
truths'
necessary
as
known
be
to
science they would come
they
could
nor
just
experience,
from
truths they could not be derivable
3 . M i l l ( 1 8 7 4 ) ,P P '8 0 , 2 0 1 ,4 7 1 .
70
Darwin and His Critics
Essences
be verified solely by reference to it. Rather they courd be known to be
necessary truths only by intuition. The mind superinduces concepts on
the facts. These concepts are appropriate if they are clear and distinct
.of the permanence of species. (See the comments by CarPenter in his review.) For essentialists,such difEculties and disagreelnentswere only technical problems to be overcome by more careful examination of the data.
,There hnd to be diagnostic characters. For Darwin no such characters
(the traditional rationalists' criterion) and if they fit. the facts closely (but
considerable latitude is permitted for rei4terpreting the facts to fit tlrc
concepts). one of the notable features of whewell's phitosophy of science
is that he includes no mechanism for periodic conceptual revorutions. Ile
seems to assume that in each area of science there will be one and only
one scientific revolution and that in physics that revolution had already
occurred. In physics, at least, no future revolutions could occur. A{though
whewell's views on science do not preclude a series of conceptual revolu.
tions in a particular branch of science, they are certainly biased toward
a linear interpretation of scientific progress. In point of fact, whewell hrm"
self had an extremely reactionary attitude toward any advances in science
after his formative years.
A belief in a finite number of discrete kincls of entities underlay both
Mill's and Whewell's notions of verification. It also was one of the major
factors in the prevalence of occult qualities in science. science deais with
classesof entities. on the essentialistview, these classesmust be clistinguish.
able by characters which universally covary. Time and again no such
set of universally covarying observable characters could be found.
Hence, these classeshad to be distinguishable by unobservabre characters.
Sometimes this maneuver met with considerable success(e.g., in distinguishing elements by their atomic weight a'd number) . sometimes it did not
(e.9., distinguishing life from nonJife by the presenceof a vital force).
In reading the scientific and philosophic works of the period, the modern
reader often finds himself wondering how essentialismcourd have had the
slightest appeal or could have seemed in the least plausible. The answer
can be found in its apparent applicability to physical geometry. Here, there
was no doubt as to which characters were essential and which were accldental. Maybe all reptiles did not have three-chambered hearts, but all
triangles had three sides. Geometric figures were the chief examples of
natural kinds in essentialist philosophies from Plato and Aristotle to
whewell and Mill. species of plants and animals were the second most
popular exarnples. When the diversity of the organic worid was only very
poorly known, organic speciesseemed to be as distinct as those of geometry.
By the time of Darwin, however, biologists had been forced to recognize
that they were not quite so distinct. In fact, the scandalous state of taxonomy was one of the chief arguments used by Darwin against the doctrine
7l
ex.istedfor speciesextended in time.
Inorganic elements also, on occasion, were cited as examples of natural'
kinds, though they ran a very poor third to those of geometry and natural
history. (See Jenkin's review.) What must be kept in mind is that for
esentialists aLI natural l<inds were equally immutable. Some appreciation
of how incredible Darwin's theory must have sounded to his contemporaries
can be obtained by realizing that for them one speciesof living creature
evolving into another was as impossible as a pentagon evolving into a
hexagonor lead into gold. Not only did evolutionary theory seem to PresuPpose spontaneous generation, but also it smacked of alchemy. One can
understandDarwin's reticence about Ihaking public his views on the evolu:
tion of specieswhen one discovers that half a century later, after scientists
had becomeused to the notion of evolution, Frederick Soddy (1877-1956)
feared to make public his conviction that transmutation of chemical ele.ments was possible lest the chemists "have his head off." In 19i7, when
one chemical eiement was actually transmuted into another, a Darwin ntad
his hand in this evolutionary adventure-Darwin's grandson, C. G. Darwin'a
Although phiiosophers generally agree that science can have no implications for true metaphysics, theoretical innovations in science from Darwin
to Dinstein have necessitated a complete re-evaluzrtion of the notion of
natural kinds. The result of this re-evaluation has been the recognition
that separate stories must be told for geometric, biological, and chemical
species.Philosophers of science contemPorary with Darwin tried to tell
one story which would be adequate both for the "cleductive sciences" like
and
,seometry and arithmetic and the "inductive sciences" like physics
biology.
Whewell in the I(antian tradition assimilated the axioms of physics to
the axioms of geometry. A1l were a priori. Experience might serve as an
impetus to the formation of such ideas, but once conceived,their truth could
be known a priori. This position seemedplausible enough {or general spatial
irjeas,such as triangles having three sides and parallel lines never meeting,
but it began to become somewhat strained when the ideas of causation
ancl clesign were included on the list of a priori truths about the empirical
world and broke down entirely under such empirical laws as those of Kepler
4 . S c h o n l a n(d1 9 6 8 ) ,p . 1 5 9 .
72
Essences
Darwin and Ilis Critics
and Newton. Mill, on the other hand, assimilated the axioms of geometry
to those of physics, and in this view, he was joined by Herschel. All were
inductions from experience. Certain ideas spring from experience, almost i
spontaneously, iike very basic notions of space, time, and causation, but l
they neverthelesswere empirical claims, whose truth could be decided by '
scientific investigation. Kepler's laws certainly seemed straightforwardly empirical. A body could fulfill all the requirements for being a planet ancl
still fail to move in accordance with l(epler's iaws, but the basic axiours
of geometry seemed immune to verification or falsification by experiment
or observation. The parallel postulate for sure was thought to be a posterion,
yet there seemed to be no way to confirm or refute it.
Although the current received doctrine in history is that no historical
dispute should be elucidated or resolved by contrasting it with the present
views on the subject, it seems grossly unfair to leave the reader in the
same state of confusion in these natters as that which prevailed in the
nineteenth century. The question is whether the axioms of tl-re formal and
empirical sciencesare self-evident truths superinduced on the facts by the
mind, or truths inductively collected from the facts. For both, the answer
is neither. Both sides were mistaken, but the mistal<i was conceptual, not
factual. According to the current view, a sharp distinction must be draun
between pure, uninterpreted systems, such as. pure geometry, and tlie
theories of empirical science, such as physical geometry. All the statements
in pure geometry, wl-rether axioms, definitions, or theorems, are tautoiogical
and in no sense about physical space. Nor are they truths of reason or
of the mind. In Euclidean geometry, parallel lines never meet, and no
physical or psychological observation is relevant to this. claim. However,
axiornatic systems can be given physical interpretations. For example, the
phrase "straight line" in Euclidean geometry can be taken to denote light
rays, transforming it into a physical geometry. In such an interpretation,
the parallel line postulate is not a priori true. It is false. As an axiom
in pure geometry, the parallel line postulate is a priori tr-ue but in no
sense about physical space. As an axiom in physical geometry, it is about
physical space and false a posteriori. Until this radical distinction was made)
no philosopher could hope to understand the relation between the formal
and empirical sciences.5
Within empirical science a further distinction must also be made. Species
5. The problem of the relation betweenmathematics.andnatural sciencehas
had a long history. Periodically,early thinkers set forth ideas very close to tnose
now held on the subject;
being ruths of the mind.
e.g., Buffon.
However,
Buffon
viewed
mathematics
as
IJ
.of inorganic objects differ in several important respects from species of
of chemical elements was
i.Flants änd animals. Earlier the transmutation
,:eOnrpar.cdto the evolution of species, but the two
Processes are very differinto a like quantity
of
one
element
quantity
ent. Pliysicists change a small
number,
i..ni another'element. Lead and gold, defined in terms of their atomic
were trans- '
i still renrain lead and gold. Even if all the lead in the universe
in the
lead
for
be
reserved
-'. nruted into other elements, a spot would still
it
rnore,
once
to
form
were
ti:ni*nsification of eiements. If eventually lead
element
physical
a
which
' vould be lead, Pure and simple. The process by
.. is generatedand its past history are irrelevant to its identity.
'Ihe situation is quite different with respect to speciesof living creatures.
Biologistscommonly maintain that speciesmust be monoPhyletic. Various
but the two most prevalent
definitionsof "monophyly" have been sr.rggested,
definitions are (a) a taxon is monophyletic if it is derived by descent
from a single immediately ancestral species; and (b) a taxon is mono'
phyletic if it is derived by descent from a single immediately ancestral
täxon of its own or lower rank. On interpretation (a) a family is monophyletic only if every speciesincluded in the family is derived from another
intpgcies in the family or at most one immediately ancestral speciesnot
rluded in the taxon. In interpretation (b) a famll:y is monophyletic only
if every speciesincluded in the family is derived from another speciesin
the lamily or from one or more species not included in the family, as
long as all of these speciesbelong to the same family.
In either interpretation species become historical entities. Having the
appropriate Past history is necessaryfor a speciessto be the species that
it is. For example, if a speciesof dinosaur were to evolve from present-day
reptiles which was in every respect, save its phylogenetic history, identical
ts an extinct species of reptile, it would still be a new, separate species'
This view of species as being monophyletic evolutionary units is the currently clominant view.6 Tl-rere is also a minority view that animal species
should be treated like chemical elements defined symPtomatologically,T
and at least one philosopher agrees with this position.s Thus, Darwin's
theory had two seemingly contrary implications for the relation of biology
to physics. Its naturalism brought biology and physics into closer accord,
but its apparent reliance on historical concepts tended to drive the two
apart again.
6 . S e eS i m p s o n( 1 9 6 1 )a n d M a y r ( 1 9 6 9 ) .
7. Sokaa
l n d S n e a t h( 1 9 6 3 ) .
B. Smart(1963).
75
Darwin and l{is Critics
Essences
Darwin dismissedtheological explanations of the origin of speciesbecause
they were not properly scientific. Ile also dismissed explanations in terms
of "plans," divine or otherwise. They, too, were empty verbiage. Explana-
.ntre not so much refuted by Darwin as discounted. Similarly, the theologisal and metaphysical objections to evolutionary theory gradually subsided,
not becausetheir authors had been converted, but because no one whose
tions in terms of coherence of plan had been common in biology for well
over a century before Darwin, especially in the writings of ideal morphologists like Goethe, Cuvier, Owen, and Agassiz. As long as one believed
in God, and these plans could be interpreted literally as thoughts in the
mind of the creator, then such explanations had some explanatory force,
but if reference to God is left out of the explanatory picture, then all that
is left are the plans. Rather than being explanations, the existence of such
"plans" calls for explanation. In England, at least, Darwin's aversion to
scientific explanations in terms of explicit reference to God and conformity
to plan was shared by a growing number of scientists.For example, Edward
Forbes,e in 1854, published an explanation of the distribution of living
creatures in geological time in terms of polarity, "a manifestation of force
of development at opposite poles of an ideal sphere." Forbes divided geological time into two periods-the Neozoic and Paleozoic.The distribution of
generic types then {ormed a figure eight with its constriction during the
Triassic and Permian epochs. Although Forbes argued that this distribution
occurred in time, the explanatory ideal plan was atemporal. To put
Darwin's reaction to Forbes's explanation simply, it made him sick. trither
it rvas nothing rnore than a description of the distribution of generic types
in time or else it was lihe magnetism turning a table.1oDarwin could not
see how references to ideal plans could explain anything. To say that the
hand of a man or a monkey, the foot of a horse, the flipper of a seal,
the wing of a bat, and so forth, have all been formed on the same ideal
plan "is no scientific explanation."rl One of the purposes of evolutionary
theory was to provide a naturalistic explanation for such homologies.l2
Modern readers of the Origin of Species tend to grow impatient with
Darwin for going to such lengths to argue against sp3cial creation and
divine plans. They are no longer considered even viable candidates for
scientific explanations. The decision was not so clearcut in Darwin's day,
Many philosophers and some scientistsstill looked upon miracles and ideas
in the mind of the creator as acceptable elements in a scientific explanation,
though most scientists were loath to discuss the issue. These "explanations"
matterecl was listening any more. The
change can be seen in the
diserence between the aggressive confidence of Agassiz's first review of
i.thr Origln ot' Speciesin 1860 and the petulant timidity of his final comments
in 1874. Even in his original review of the Origin, Agassiz acknowledged
ihat lome naturalists looked upon his idea of creation by God's mental
exertion as a kind of bigotry and his holding the view a sign of non
üafil)or ntentis.Fourteen years later he hardly dared mention his pet theory
of creation by repeated acts of divine cognition. Owen went so far as to
assert that the leading naturalists of the day, referred to by Darwin as
Sp€cial creationists, had neuer mai1.tained the view that species n'ere
$peciallycreated by divine action. Rather, he along with the other so-called
rpecial creationistshad always maintaintjd that some unknown law governed
rhe introduction and extinction of species.Lyell, to the contrary, had the
candor to admit that he "formerly advocated the doctrine that species
t'ere primordial creations, and not derivation."t3 FTe differed from the
catastlophistsonly in his belief that specieswere creatöd and extinguished
serially,ratl-rerthan in wholesalelots.
Naturalistic explanations,had become the order of the day. The authors
included in this anthology by and large agreed that scientific theories were
to be judged only by scientific standards. Even the philosopher primed
b.vAgassizfor his review of the Origin, Francis Bowen, admitted "all that
has been claimed for the proper independenceof true physical science,-that
its conclusions are to be tested by their own evidence, and not by their
agreement or want of agreement with the teachings of Scripture, with
reeeiveddoctrine in theology or philosophy, or with any foreign standard
whatsoever."laLike Newton's hypothesis non fingo, this proclamation was
easierto declare than to implement becausethe boundaries between science,
philosphy, and theology began to blur when one approached the problem
of man's menta.l powers and morai nature. These faculties had always
beentl.reprovinces of philosophy and theology. While perusing the following
reviervs,the modern reader may be puzzled by the disproportionate attention
given to Darwin's explanations of the hive-making habits of bees and the
slave-rnakinghabits of ants. The emphasis was not misplaced. Darwin was
9. Forbes(1854)
, p.430.
10.Darwin,July2, 1854,
AIo1'e
LetLcrs(1903)
, l:?7.
l l . D a r w i n ( 1 8 7 1, )p p . 3 l - 3 2 .
I2, Scc llopkins, Mivart, and \Arrigbt revicws in this volume
o f - F o r b c s ' sp r i r r c i i r l e o f p o l a r i t y .
'..bpinion
13.Lyell (187g), p.469; seealso the reviewsof Hooker,Carpenter,Wollaston,
fol additional
opiuions
and Fawcett in this volume.
14. Bowen (1860), p. 476'
I
:
76
Darwin and His Critics
Essences
taking his first steps toward the explanation of man's higher faculties. I-Iis
intentions were not lost on his reviewers. The conclusions ol true physical
science were to be judged only by scientific standards, but Darwin was
trespassing on the property of philosophy and theology and deserved to
be criticized by their standards, and this authors like Sedgwick and Bowen
proceeded to do. In doing so, they were not intruding on the proper domain
of science. Rather, in Bowen's words, the "intrusion, if. any, comes from
the other side. It is now the naturalist, the pure physicist, who, quitting
but they occur rarely. Given what we know of genetics and population
biology, gradual evolution is the rule. Huxley's suggestion has been taken
up periodically by scientists (e.g., Goldschmidt ärrd Schindewolf). From
a pulely scientific point of view there is no a priori reason {or preferring
one tylle of evolution over the other. From a metaphysical point of view,
therc is. Speciation by saitation would permit the retention of the discrete-'
his own territory, but, as he professes,still relying exclusively on physical
evidence, seeksto build up metaphysical conclusions."l5
Even after the boundary between philosophy and science was redrawn
to distinguish between psychology and epistemology, the adjustments rn
philosophy necessitatedby evolutionary theory were of the most fundamental hind. Either one of the chief examples of natural kinds had to be
dismissed as not actually being natural kinds, or else the notion of natural
kind had to be reworked. Some philosophers chose the forrner alternativc
and retreated to geometry. Bos bos was not properly a natural kind. Equilateral triangles were. Relativity theory drove the adherents of natural kinds
out of their last sanctuary. Some philosophers took the second alternative
and tried to produce a metaphysics which did not depend on the essentialist
notion of natural kinds. The extreme difficulty of this undertaking can
be seen in the development of philosophy during the last fifty years.t6
Later criticisms of evolutionary theory tended to be directed at Darwin's
mechanisms---chance variation and natural selection. Perhaps species evolved
and a naturalistic mechanism is called for, but Darwin's explanation was
inadequate. The two modifications of evolutionary .theory most frequently
suggested were the substitution of evolution by saltation for Darwinian
gradual evolution and the addition of a force or principle internal to organisms to direct them in their evolutionary development. The former
served to salvage the discreteness of natural kinds, the latter to save
teleology.
Even Darwin's strongest supporters took great pride in keeping one toe
dry. Huxley, for example, thought Darwin had loaded himself "with an
unnecessary difficulty in adopting Natura non facit saltum so unreservedly."rz By and large, Darwin was right. There are genetic mechanisms
which result in new species' evolving in a single generation (polyploidy),
1 5 .I b i d . , p . 4 4 7 .
.
16.D. L. l-lull (1974)
17.L. Huxley (1902)
, p. I89.
77
nessof natural kinds, a tenet central to essentialism.
Gray, Wallace, and Lyell all argued for the inclusion of some vestige
of teleology in evolutionary theory. On this score, they were joined by
a host of other scientists,including Owen and Mivart. Mivart, for instance,
reasonedthat just as there was a principle internal to an individual organism
rvhich determined its regular embryological development, there must also
be a similar principle to determine the evolutionary development of species'
By reasoning in this manner, these scientistswere returning to something
like the Aristotelian notion of imrnahent teleology. In this case, however,
thc cnd was not a cyclical returning to the same type but a progression
from one type to another. Darwin could find no evidence of such a directing
internal influence and steadfastly refused to admit it. Once again, Darwin
seemsto have been right. We now know why organisms go through their
regular cycles of development-the information coded in their DNA. This
infonnation has been built up through eons of natural selection. No hint
of a mechanism by which the future development of a species may also
be incorporated into this code has been discovered. The truly amazing
feature of Darwin's intellect was the frequency with which he was able
to "guess" correctly, even though he iacked the requisite data and anything
like an adequate theory governing the phenomena. Modern evolutionary
theory is closer to the original Darwinian formulation today than it has
ever been.18
which are almostdiamerically
lB. PeterVorzimmer (1970) comesto conclusions
opposed to those expressedin this Introduction with re5Jardto Darwin's adherence
to gradual evolution and innate directive forces. Vorzimmer thinks that Mivart's
criticisms of Darwin's theory "had been the prime instrument in badgering the
elderly Darwin into the state of frustrating confusion which marked him on the
cve of his retirement" (p. 250). See the discussion of Mivart's review of The
Descent of Man (1871.) in this volume for further examination of vorzirhmer's
analysisof the situation.
Douglasf. Futuyma
StateUniversityof NewYorkat StonyBrook
Evolution
:
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Chapter19 (Evolutionof Genesand Genomes)
by ScottV.Edwards,HarvardlJniversity
Chapter20 (Evolutionand Development)
by Iohn R. True,StateUniversityof NewYork at StonyBrook
Übersetzungvon AndreasHeld
Spektrum
x-/l
AxlDBmscHEn
vEtLAo
I
Zuschriften und Kritik an:
ElsevierGmbH, SpektrumAkademischer
Verlag,Merlet Behncke-Braunbeck,
Slevogtstraße
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Mail: [email protected]
Autor:
Douglas J. Futuyma
Lehn^rmuleh
Titel der Originalausgabe:
Evolution
Amerikanische Originalausgabe2005 bei SinauerAssociates,Inc.,23 Plumtree Road, Sunderland,MA 01375,USA
Copyright @ 2005 by SinauerAssociates,Inc.. A1l rights reserved.
I S B N : 0 - 8 7 8 9 3 -18 7 - 2
www.slnauer.com
Sources of the scientists' photographs appearing in Chapter I are gratefully acknowledged:
Q. Darwin and A. R. Wallace courtesy of The American Philosophical Library
R. A. Fisher courtesy of Joan Fisher Box
J. B. S. Haldane courtesy of Dr. K. Patau
S. Wright courtesy of Doris Marie Provine
t
'
E. Mayr courtesy of Harvard News Service and E. Mayr
'-.
G. L. Stebbins,G. G. Simpson, and Th. Dobzhansky courtesy of G. L. Stebbins ,*--lM. Kimura courtesy of William Provine
"
'J
Übersetzer
Andreas Held
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Inhaltsüberblick
Kapitell ' E v o l u t i o n s b i o l o1g i e
s :l a s s i f i k a tui onndP h y l o g e n1i e7
e sL e b e n K
Kapitel2:, D e rS t a m m b a udm
43
Kapitel3: Evolutionsmuster
67
in denFossilbelegen
Kapitel4,' Evolution
aufderErde91
desLebens
Kapitel5" EineGeschichte
Kapitel1,;,D i eG e o g r a p hdi e rE v o l u t i o1n1 7
139
derBiodiversität
KapitelT, DieEvolution
161
Variabilität
dergenetischen
S DieEntstehung
Kapitel
-,
Kaprtelg ' V a r i a b i l i t ä1 t8 9
225
nachdemZufallsprinzip
Drift:Evolution
Kapitella'. Genetische
247
undAnpassung
Selektion
KapitellI , Natürliche
:
269
Selektion
Theorie
dernatürlichen
Kapitel12 Diegenetische
phänotypischer
297
Merkmale
Kapitell:J" DieEvolution
325
Kapitel14 ' KonfliktundKooperation
Kuoitel15 ', Arten353
g7 9
Kapitel16 A r t b i l d u n 3
a05
Fortpflanzungserfolg
KapitellT Fitness:
vonWechselbeziehungen
DieEvolution
KapitellB Coevolution:
Arten429
zwischen
449
Kapttellg DieEvolution
vonGenenundGenomen
Kapitel20 Evolution
473
undEntwicklung
Kapitel2t Makroevolution:
derArtebene501
Evolution
oberhalb
523
Kapitelz2 Evolutionswissenschaft,
undGesellschaft
Kreationismus
EVOLUTIONARY BIOLOG I
a1l sorts (especially on plants) and to publish many more alticles and books, of which The
Dcscent of Man is the most renowned. Darwin's books reveal an irrePressibly inquisitive
man, fascinated with all of biology, creative in devising hypotheses and in bringing evidence to bear upon them, and profoundly aware that every fact of biology, no matter how
seemingly trivial, must fit into a coherent, unified understanding of the world.
rvissbegierig
Erstelien
n'sEvolutionaryTheory
Darvvi
TIrcOrigin of Specieshas two major theses.The first is Darwin's theory of descent with
modification. It hoids that all species,living and extinct, have descended,without interruption, from one or a few original forms of life (Figure 1.3B).Speciesthat diverged from
but accumulateddifferencesover gleat SPans
a common atcestor were at firSt very simila-5,
of time, so that some are now radically different frorn one anothel Darwin's concePtion
of the courseof evolution is profoundly different from Lamarck's, in which the concept
of common ancestrvplays aimost no role'
The second theme of TfteOrigin of Speciesis Darwin's iheory of the causal agents of evolutionary change.This was his theory of natural selection:"if variations useful to äny oreanicbeing ever occul assuredlyindividuals thus characterisedwill have the best chance
äf b"irrg pieserved in the struggle for life; and from the strong principle of inheritance,
thesewill tend to produce offsPdng similarly characterised'This principle of peqqve:
don, or the survival of the fittest, I have called natural selection."This theory is a vaRlaTransfornational evolution
Generation I
Abstammuirg
Ursachen
Nachkommer / Erhaltrurg, I(onservierung .,,Variationstheorie"
Generation 3
Generation 2
Reproductive
age (RA)
Birth (B)
Unterbrechung
BR,\B
RA
O--+C
O+O
O +O
OO
O +O
O +O
Time+
Vuiational evolution
Reproductive
age (RA)
Birth (B)
o
o
@
+
Generation3
Generation 2
Generation I
RAB
B
O------*O
+C-------O
tle
+
O ------
+
,--@
q -::l--> 6
+
O
o
c
(D
tlme+
Figure 1.4 A diagrammatic contrast between transformational and variational theories of
change,shown across three generations. Within each generation, individuals are
::_olutior,taly
representedearlieiand later in
their liver]Th" i.tdiridrr^ls in the leit column [Spalte] in each
ge-neration
are the olfspring of thosein the right column of the preceding Ivoihärgehen.tlgeneration' In transfo.maüonai
evolutiory indiviäuals are altered a'uring the"ii lifetimäs, and-tfreir
F^t:"qT{ [N.achkonrmen]are born wiih these alterations. In variatiorial evolution, hereditarily
. rt
l:t:,',t::!
liffutent forms at ihe beginning of the history are not transformed, but instead diffär
survlval
and reproductive rate-flrortp;lanzungsrate], so that their proportions change from
one generaHonto
änother.
,
C H A P T E R1
,,Transforrnationstheorie" noN+L
of change, diffeling profoundly fiom Lamarck's TRANSFORMATTONAL
rFrF^D,,
T.rEoBy
in which individual oiganisms chänge (Figur.e i,4).
what is often called "Darwin's theory of evolution" actually includes five theories
(Mayr 1982a):
Aussage,BeJrauptung
erstellte
Craclualisrnus
Spt'tirrge/ Saltationen
Zrryisclrenstnfen
ii
r1
anPassel-r
Abkörnrnlinse
adaptiv
Lebensgewohnherten 7
I(onknlrenzdruck
D i v c r g e r r zA, r rp a s s u r r g snut e r schiede. Lücke
vorherrschend / Vererbrrrrgquantitativer Melkmale / abnehmen
Vermisclrer.r
partikuläre Verelbrurg
überdauerrr
7,'Eaolution as such is the simple plapgqtig4 that the characteristics of lineages of or_
garusrns change over time. This idea was not original with Dar\f in, but iiwas Darwin who so convincingly marshaled the evidence for evolution that most biologists
soon accepted that it has indeed occurred.
2. Conmton descentis a radicaliy different view of evolution than the scheme Lamarck
had proposed (see Figure 1.3). Dar-win was the first to argue that species had diverged from common ancestors and that all of life could be portrayed as one grear
family tree.
3. Qls!'tglhuis
Darwin's proposition that the differences between even radically different organisms have evolved incrementally, by srnall steps through intermediate
forms. The alter.ative hypothesis is that large diffe'ences evolve by leaps, or sALrAttoNs, r,t'ithout intermediates.
4. Populational clmnge is Darwin's thesis that evolution occurs by changes in the proportions of individuals within a population that have different inherited charaCteristics (see Figure 1.48). This concept was a completely original idea that contrasts
both with the sudden origin of new species by saltation and with Lamarck,s account of evolutionary change by transformation of individuals.
5. Natural selection was Darwin's brilliant hypothesis, independently conceived by
Wallace, that changes in the proportions of different types of individuals are caused
by differences in their ability to survirze and reproduce-and
that such changes result in the evolution o{ adaptations, features that appear "desigrred,, to fit organisms to their environment. The concept of nafural selection revolutionized nöt only
biology, but Western thought as a whole.
Darwin proposed that the various descendants of a common ancestor evolve different
features beiauie they are adapfive .-a"t atff"t'"t-rt "conditions of life"-different
habitats
or habits. Moleovel, the pressure of competition favors the use of different foods or habitats by different species- He believed that no matter how extensiveh' a species has d!
verged from its ancesto{, new hereditary variations continue to arise, sothat given enough
time, there is no evident limit to the amount of diversence that can occur_
Where,thougtu do these heredituty variutio.ri.oil
f.om? This was the grear ggp in
Danrrin's theory and he never filled it. The problem was serious, beca,rse accoidinglo the
prgvail!4g belief in BLENpTNcrNHERrrANcE,variation should decrease, not incre4se. Because
offspring are often intermediate between their parents in features such as color or size, it
was widely believed that characteristics are inherited iike fluids, such as different colors
of paint. Blending white and black paints produces gray, but mixing fwo gray pairts doesn't yield black ol white: variation decreases. Darwin never knew that Gregor Mendel had
irr fact solved the problem in a paper published in 1865. Mendel's theorli of pen:rrculars
INHERITANCE
proposed that inheritance is based not on blending fluids, but on particles
that pass unaltered from genelation to generation-so that variation can pers:is.!.The co.tcept of "mutation" in such particles (later called genes) developed only after 1900 and was
not clarified until considerably later.
EvolutionaryTheoriesafter Darwin
folgte
Paläontologre / r'erg;leicher-rde
Morpirologie
Fossilbelege,
Fossilfunde
Altlrough Theorigin of speciesraised enormouscontroversy,by the 1870smost scientists acceptedthe historical reality of evolution by common descent.There ensued,in
the late nineteenth and early twentieth centuries,a "golden age" of p4lepqlqlegy, comparative morphology, and comparativeembryology,during which a great deai of information on evolution in the fossil record and on relationshipsamong organismswas
amassed.But this consensusdid not extend to Darlsin's theorv of the causeof evolu-
adaptation Anpassung, Adaptation / environment Umwelt
E V O L U T I O N A RB
YI O L O G Y
tion, natural selection.For about 60 years after the publication of TheOrigin of Species,
ali but a few faithful Darwinians rejectednatural selection,and numerous theorieswere
proposedin its stead.Thesetheoriesincluded neo-Lamarckiaryorthogenetic,and mu,
iationist theories(Bowler 1989).
Nro-LevlqncrrsM [Neolamarckismus] includes severaltheories based on the old idea
of inheritance of modifications acquired during an organism's lifetime. Such modifications might have been due, for example,to the direct effect of the environment on development (as in plants that develop thicker leaves [Blätter] if grown in a ho! dry environment). In a famous experiment, August Weismann cut off the tails of mice for many
generationsand showed that this had no effecton the tail length of their descendants.Exiensive subsequentresearchhas provided no evidence that specific hereditary changes
can be induced by environmental conditions [UrnweltbedingungenJ under which they
wouid be advantageousIvorteilhaft].
Theoriesof oRtHocrNnsIsIOrthogenese,Orthoevoh-rtion],or "straight-line evolutiory"
held that the variation that arisesis directed towald fixed goals,so that a speciesevolves
in a predeterrnined[vorherbestimmt] direction without the aid of natural selection.Some
paleontoiogistsheld that such trends need not be adaptive and could even drive species
toward extinction IAussterben]. None of the proponents [Befüru.orter] of orthogenesis
ever Proposeda mechanism for it.
Mureuomlst theories fMutationstheorien,Mutationismus]were advancedby some
geneticistswho observedthat discretelydifferent new phenotypes IPhänotypen]can
ariseby a processof mutation. They supposed that such mutant forms constituted new
species,and thus believed that natural selectionwas not necessaryto accountfor the
origin of species.Mutationist ideas were advancedby Hugo de Vries, one of the biologistswho "discovered" Mendel's neglected paper in 1900,and by Thomas Hunt Morgan,the founder ol Drosophilagenetics.The last influential mutationist was Richard
Goldschmidt (7940),an accornplished geneticist who neverthelesserroneously argued
that evolutionary change within speciesis entirely different in kind from ihe origin of
new speciesand higher taxa [(Taxa;Singular: Taxon)].These,he said, originate by sudden, drastic changesthat reorganize the whole genome. Although most such reorganizationswould be deleterious [nachteilig], a few "hopeful monsters" would be the progenitors [Vor1äufer'.]
of new groups.
TheEvolutionary Synthesi
s
Theseanti-Darwirrianideas were refuted [widerlegt, angefochten]in the 1930sand 1940s
by_the evolutionary synthesis or modern syntheiis, foiged from [geformt aus] the conki-butionsof geneticists,systematists,and paleontologistswho reconciled
[abglicheryab,
stimmtenl Danrrin's theory with the facts of genetics(Mayr and provine 1980;smocovitis 1996).RonaldA. Fisherand JohnB. s. Haidane in England and sewall wright in the
unitedstates.developeda mathematicaltheory of population genetics
Ipop*ulationsgenetikl,which showed that mutation and nafural seleciion togethercauseidaptive evolution: mutation is not an alternative to natural selectiorybutls rather its raw material.
tqov of geneticvariation and changein natural populations was pioneeredin RusIh:
siaby sergeichetverikov and continueä by Theodosius Dobzhansky,who
moved from
Russiato the united states.ln his influential book Geneticsand the
origin of species(1937),
conveyed the ideas of the population genericiststo other*bioiogists,thus in?-*l*tly
ttuT:*t their appreciationof the ge.,eti.
busis of ävolution.
*.uio. contributors to the synthesisincluded the zoologists Ernst Mayr, in Sys,_Y:1".
O.rigittof Species
(1942),andBernhardRensch,in EuorutionAboae'theSpecies
iT,:i::::!,the
tne b-otanistG. Ledyard Stebbins,inVariation and Eaobttionin plants (1950);
:"j',Lt^"rJ,
lil $-eut"ontologistGeorgeGaylordSimpson,tnTempoandModein Euolution
\1944)
l\..rchLntccr.J,
Th'eMajor Fe'attLres
of Eaolution(1953).Theseauthorsarlll^t'l^t_T*ttor
öqcu Persuasivelythat mutation, recombination,
nätural selection,and other processes
sEWALLWRIGHT
9
lo
C H A P T E R1
ERNSTMAYR
G. LEDYARDSTEBBINS,
GEORGEGAYLORDSIMPSON,AND THEODOSIUS
DOEZHAN5KY
openttnsToithin species
(which Dobzhansky termed microevolution) account for the origin of newspecies
atxdfor themajor,Ionglermt'eaturesof eaolution(termed macroevolution).
stichhaltig
Genotyp
zurückzufuhren
Cene
behaiten
Merkmale
polvgene Vererbtmg
Allele
verstärkt / Rekombination
Genorte, Genloci (Singular: Genlocus)
bedingt, hat zur Folge
Frequenzen, Häufigkeiten
'-'_-*"ö*-'ö
Vpr',lränor
rno
zufällig
genetischeDrift, Gendrift
macroevolution
Makroevolution
Fundamentalprinciplesof evolution
The principal claims of the evolutionary synthesis are the foundations of modern evolutionary biology. Although sorne of these principles have been extended, clarified, or
modified since the 1940s,most evolutionary biologists today acceptthem as fundamenta1ly valid. These,thery are the furdamental principles of evolution, to be discussedat
length throughout this book.
1. Thephenotype(observedcharacteristic)is dffirent ftom theK!\fupg(the set of genes
in an individual's DNA); phenofypic differencesamong individual organisms may
be due partly to genetic differencesand partly to direct effectsof the environment.
2. Environmental effectson an individual's phenotype do not affect the genespassed
on to its offspring. In other words, acquiredcharacteristics
arenot inherited.
3. Hereditary variations are based on particles-genes-that retain their identity as they
passthroughthegenerations;
theydo not blendwith other genes.This is true of both
discretely varying traits (e.g.,brown vs. blue eyes)and continuously varying haits
(e.g.,body size, intensity of pigmentation). Genetic variation in continuously varying traits is based on severalor many discrete,particulate genes,each of which affects the trait slightly ("polygenic inheritance").
4. Genesmutate, usually at a fairly low rate, to equally stable altemative forms,
known as alleles.The phenotypic effect of such mutations can range from undetectableto very great.The variation that arisesby mutation is amplified by recombination among allelesat different loci.
5. Eaolutionarychangeis a populationalprocess:
it entails,in its most basic form, a
changein the relafive abundances(proportions or .frequencies)
of individual organisms with different genotypes (hence, ofteru with different phenotypes) within a
population. One genotype may gradualiy replaceother genofypesover the course
of generations.Replacementmay occur within only certain populations, or in all
the populations that make up a species.
6. The rate of mutation is too low for mutation by itself to shift a population from one
genotype to another.Instead,the changein genotype proportions within a population can occur by either of two principal processes:random fluctuations in proportions (geneticdrift), or noruandom changesdue to the superior survival and/or reproduction of some genotypescompared with others (i.e.,natural selection).
Natural selectionand rarrdom genetjc drift can operate simultaneously.
/ microevolution
Mikroevolution
;::
t
$
E V O L U T I O N A RB
YI O L O G Y
7. Even a slight intensity of natural selectioncan (under certain circumstances)bring
about substantial evolutionary changein a realistic amount of time. Natural selection
as well as for the earliest
cannccountfor bothslight andgreatdffirencesamongspecies,
stagesof evolution of new traits. Adapiations are haits that have been shaped by
nafural selection'
8. Natural selectioncan alter populations beyond the original range of variation by
increasingthe frequenclr of allelesthat, by recombination with other genesthat affect the sametrait, give rise to new phenotyPes.
9. Natural populations are geneticallyvariable, and so can often evolve rapidly when
environmentalconditions change.
10. Populationsof a speciesin different geographic regions differ in characteristicsthat
have a geneticbasis'
11, The differencesbetween different species,and between different populations of the
samespecies,are often based on differencesat severalor many genes,many of
which have a small phenotypic effect.This pattern supports the hypothesis that the
differencesbetween speciesevolve by rather small steps.
12. Differencesarnong geographic populations of a speciesare often adaptive, and thus
are the consequenceof natural selection.
13. Phenotypically different genotyPesare often found in a single interbreeding population. Speciesare not defined simply by phenotypic differences.Rather,different
speciesrepresentdistinct "gene pools"; that is, speciesare grouPs of interbreeding
oi potentially interbreeding individuals that do not exchangegeneswith other such
glouPs.
14. Speciationis the origin of two or more speciesfrom a single corrunon ancestor.Speciation usually occursby the geneticdifferentiation of geographically segregated
populations.Becauseof the geographic segregation,interbreeding does not prevent
incipient geneticdifferencesfrom developing.
15. Among living organisms,there are many gradations in phenotypic characteristics
among speciesassignedto the samegenus,to different genera,and to different
families or other higher taxa. Such observationsprovide evidence that higher taxa
ariseby the prolonged, sequentialaccumulation of small differences,rather than by
the sudden mutational origin of drastically new "type-s."
16. The fossil record includesmany gapsamong quite different kinds of organisms.Such
gapsmay be explainedby the incompletenessof the fossil record.But the fossil
recordalsoincludes examplesof gradationsfrom apparently ancestralorganismsto
quite different descendants.Thesedata support the hypothesisthat the evolution of
large differencespISg994Cl4Ie!qC!tA!y. Hence the principles tha! explain the evolution of populationsand speciesmay be exhapolatedto the evolution of higher tara.
Allelfrequenz
sich unteleinander kreuzend
Genpools
Artbildung, Speziation
Differenzierung / getrennt
einsetzend,begimend.
Gattung
Entstehung
schreitet stufenweise voran
_'"-_'ö-_--__'-hnchoererhnpf
EvolutionaryBiology sincethe Synthesis
Sincethe evolutionary synthesis,a great deal of researchhas elaboratedand testedits basic principles.Beginning in the 1950sand accelerating [sich beschleunigend] since, advancesin geneticsand molecular biology have virfually revolutionized the study of evol"jt9" and have opened entirely neü research areis, such as molecular evolution.
Molecularbiology has provided täob for studying a vast number of evolutionary topics,
lucl3s mutation, geneticvariatiory speciesdifferences,deveiopment, and the phylogenetrchistory of life.
S,il.: the mia-lSOOs,
evolutionary theory has expanded into areassuch as ecology,an.
imal behavior,and reproductive biology,
äna detäitea theories have been develolld to
explain the evolution äf particulur Una!äf
characteristicssuch as life span, ecologiial dishas been renewed byfrovoca$b1dory and social behävior. The study of *uo*"of"Uon
., , I":t^l*:Oretations of the fossil record und by ,,"* methods for studying phytogeneticreVerwandischaftsbeziehungen].
ai
methods
illl-Thpt Istamnresgeschichtliche
mo." sophisticatedand available,virtually new"fieids of-ät"."tui
evolutionary study
. HLl1":"le
navedeveloPed.
Ambng thesefields is Hlor-scuranEvoLUTroN
ImolekulareEvolution]
MOTOO KIMURA
11
12
CHAPTER
1
Nerr tralther:rie der molektrlaren
Evoh-rtion, Mutationstlreone
evoluti or1äre Entwicl<lun gsbiologie
einschränken
evolutiouäre Genomik
ganze Genorne
(analyses of the processesand history of change in genes), in which the xsurnaL
rHeoo,,
oF MoLEctr-AR EvoLUTIoNhas been particularly important. This hypoihesis, develope4 qspecially by Motoo Kimura (1924-7994), holds that most of the evolution of Di\A
s;_
quences occurs by genetic drift rather than by natural selection. Ev!:r-urro_Nanyorv.rLoi_
MENTALBrolqcy is an exciting field devoted to understanding how developmental
processes both evolr'e and constrain evolution. It is closell'tied to developmentuiliotog;;
one of the most rapidly moving fields of biology today. EvoLurroNeRv crNorr4rcs.q6ncerned lt ith variation and evolution in multiple genes or even entire genomes, is bei.o
born. The advances in these fields, though" are coÄplement"a Uy
;;.f;
"iffiireGrd,
discoveries, and new ideas about long-standing topics in evolutionary
biology, such as
the evolution of adaptations and of new species. This is an exciting time to löarn about
evolution-or
to be an evolutionarv biolosist.
Philosophicallssues
Foleen,Ausrvirkurrgen
lehnte alr
endlos
Stasis
Erdbeben
Zweck
überflilsr1t
r.ermehren
ft'uchtbar; produktir, / r'erunsi chernd
Wasserstoffbrirckenbindungen
Thousands of pages have been written about the pl-rilosophical and social implications of
evolution. Darwin argued that every characteristic of a species can vary and can be alteied
radicaily, given enough time. Thus he reiccled the essentialism that western philosophy
had inherited from Plato and Aristotle and put variation in its place. Darwin also helpeä
to replace a static conception of the n'orld-one
virtually identical to the Creator's perfect
creation-with
a world of ceasglesschange. It was Darwin who extended to living things,
including the human species, the principle that change, not stasis, is the natural order.
Above all, Darwin's theory of random, purposeless variation acted on by blirrd, purposeless natural selection provided a revoiutionary new kind of answer to almost all questions that begin with "Why?" Before Darwiry both philosophers and people in general
answered "Why?" questions by citing purpose. Since only an intelligent mind, with the
capaci{z for forethought, can have purpose, questions such as "Why do plants have flowers?" or "Why are there apple trees?"-or diseases, or eartlrquakes-were
answered by
imagining the possible puIpgEC that God could have had in creating them.'Ihis kind of
explanation was made completely supelfluous by Darwin's theory of natural selection.
The adaptations of organisms-long
cited as the most conspicuous evidence of intelligent
design in the universe-could
be explained by purely mechanistic causes. For evolutionary biologists, the flower of a magnolia h as a function, but not a purpose. it was not designed in order to pgqp_Agatethe species, much iess to delight us with its beauty, but instead came into existence because magnolias with brightly colored flowers reproduced
more p1q1if4e1b than magnolias r.rrith less bdghtiy colored flowers. The unsettling implication of this purely material explanation is that, except in the case of human behavior, we need not invoke, nor can we find any evidence for, any design, goal, or purpose
anywhere in the natural world.
It must be emphasized that all of science has come to adopt the way of thought that
Darwin applied to biology. Astronomers do not seek the purpose of comets or supemovat
nor chemists the purpose of hydrogen bonds. The concept of purpose plays no part in scientific explanation.
Ethics,Religion,and Evolution
Handehr
u'örtliclr
ln the world of science, the reality of evolution has not been in doubt for more than a hundred years, but evolution remains an exceedingly controversial subject in the United States
and some other countries. The creationist movement (creatonism) opposes the teaching
of evolution in public schools, or at least demands "equal time" for creationist beliefs.
Such opposition arises from the fear that evolutionary science denies the existence of God,
and consequently, that it denies any basis for rules of moral or ethical conduct.
Our knowledge of the history and mechanisms of evolution is certainly incompatible
with a literql reading of the creation stories in the Bible's Book of Genesis, as it is incompatible with hundreds of other creation myths that people have devised. A literal reading
of some passages in the Bible is also incompatible with physics, geology, and other natu-
creationist movement (creationism) kreationistischeBewegung (Kreationismus)
:1,:
i;l
1;.,l
{i..
,it
t:::
't,
i{
\i
r
524
C H A P T E R2 2
TheEvidencefor Evolution
The evidence for evolution has been presented throughout the preceding chapters ot
this book. The examples provided represent only a very small percentage of the studies that might be cited for each particular line of evidence. In this section, we will simply review the sources of evidence for evolution and refer back to earlier chapters for
detailed examples.
The fossil record
i 1r:-rri'"]"1-"
i_ jrt ii_t.til.:.:a:rijtt
i!
Jli'iI
\ |LI
I)
Ll:
The fogsil rqqarci is extremely incomplete, for reasons that geologists understand well (see
Chapter 4). Consequently, the transition4l qlaggg that we postulate in the origin of many
higher taxa have not (yet) been found. But there is absolutely no truth to the claim, made
by many creationists, that the fossil record does not provide any intermediate forms. There
are many examples of such forms, both at low and high q1o4g,4q!qlCv_ql9;
Chapter 4 provides several examples in the evolution of the classesof tetrapod vertebrates.Critically
important intermediates are still being found: just in the last few years, several Chinese
fossils, including feathered dinosaurs, have greatly expar-rdedthe record of the -origin of
birds. The fossil record, moreovet docurnents two important aspects of character evolution: mos4lc ey_Sl1-tigl(e.9., the more or less independent evolution of different features
in the evolution of mammals) and gladual change of individual features (e.g., cra11allu
paerty and other features of hominins).
Many discoveries in the fossil record fit predictions made based on phyiogenetic or
other evidence. The earliest fossil ants, for instance, have the lyqAplike features that had
been predicted by galsrl1olagiet_s,and the discovery of feathered dinosaurs was to be expected, given the q!4qq4ruq that birds are modified dinosaurs. Likewise, phylogeneiic
analyses of living organisms imply a sequence of branching events, as well as a sequence
of origin of the diagnostic characters of those branches. The fossil record often matches
the predicted sequences(as we saw in Chapters 4 and 5): for example, prokaryotes plg
qgde eukaq/otes in the fossil record, wingless insects (the phylogenetically basal bristle:
tails) precede winged insects, fishes precede tetrapods, amphibians precede amniotes, algae precede vascular plants. ferns and "gyll4Alpglalq" precede flowering plants.
Phylogenetic and comparative studies
, : , . . i r i . l ' , 1 i i ,i r . \ , . ; r , . r : . i i Although many uncertainties about pfrylogsletLqfcleüS4üpg
persist (e.g., the blanch;
. , I ' . I i r r i - . , , i . t L ; i ; r ' , r i , r i i I , , 4.!g_aldcl of the major groups of birds), phylogenies that are well supported by one class
rl,.rr \ r'l /,.\ i:.]tilll
'..'l'- i..i.rl.'r.: |ii,
| |
:i:::,--ttt-r:r
".
t:. li it:ti,.:tl
il
llir'l;t
rl
l
r'- lit'i::i1l,r:rr|
.i';
-ifrirr.'i
J'i,
lr
!_,,
rir\:,ll.il
lrr.irlr, lr
of charactersusually match the relationships implied by other evidence quite well (see
Chapter 2). For example, 14qle_rrl4lphyle€enleg support many of the relationships that
have long been postulated from morphological data. These two data sets are entirely independent (the molecular phylogenies are often based on sequencesthat have no bioIogical function), so their correspondencejustifies confidence that the relalionships are
real: that the lirya&eq form glogplrylejiSg{o,Up! and have indeed descended frorn common ancestors.
The largest monophyletic group encompassesall organisms. Although Darwin allowed
that life might have originated from a few original ancestors, we can be confident today
that a1lknown living things stem from a single ancestor because of the many features that
are universally shared. These features include most of the qoda4g in the genetic code, the
machinery of nqelel! 4c1dre+liealis4, the mechanisms of transcription and translation,
proteins composed only of "left-ha_nded" (t=:qqnq) amino acids, and many aspects.ol
fundamental biochemistry. Many genes are shared among all organisms, including ihe
three major l'empires'1 (Bacteria,Archaea, and Eukaryota; see Chapters 4 and 19), ana
these genes have been successfully used to in{er the deepest branches in the tree of life.
$+cteaaliltc have shown that the differences among rc]4lcd species often form gracual series, ranging from slight differences to great diffärences with stepwise intermediates (e.g.,Figure 3.21).Such intermediates often make it difficult to establisl-rclear-cut families or other higher taxa, so that classification often becärmesa somewhat,4!i1r44y cloice
between "splltting" species among many taxa and "lumping" them into ferv. Systemanc
E V O L U T I O N A RSYC I E N C EC, R E A T I O N I S M
AN
, D SOCIETY
studies have also demonstrated the common origiry or hSglo_bry, of characteristics that
may differ greatly among taxa-the most familiar examples being the radically different forms of limbs among tetrapod vertebrates. Homology of stmctures is often more evident in early developmental stages than in adult organisms, and contemporary dgyelqg
mental biology demonstrates that Hox gg4gq and other developmental mechanisms are
shared among animal phlzla that diverged from common ancestors a billion or more years
ago (see Chapter 20).
529
Hrtmolirqie
Enth'icl<lr.:
ngsb iolosle
Hor-Cenc
I-ierstämme
Genes and genomes
The revolution in molecular biology and genomics is yielding data about evolution on a
Iarger scale than ever before. These data increasingly show the extraordinary commonal{y of all living things. Because of this commonality, the structure and function of genes
and genomes can be understood through comparisons among species and evolutionary
models. (Indeed, it is only because of this common ancestry that there has ever been any
reason to think that human biochemistry, physiology, or brain fr,rnctiorymuch less genome
function, could be understood by studying ygeqt flies, rats, or cats!)
Molecular studies show that the genomes of most organisms have similar elements,
such as a great abundance of noncoding pseudogenes and satellite DNA and a plethql4
of "selfish" transposable elements that generally provide no advantage to the organism.
These features are readily understandable under evolutionary theory, but would hardly
be expected of an intelligenf omnipotent designer. Molecular evolutionary analyses have
shown in great detail how new genes arise by processes such as unequal crossing over,
and how duplicate ge4Cqdiverge in functiory increasing the genetic repertoire (see Chapter 19). Some DNA polymorphisms are shared between species,so that, for example, some
maior histocompatibi
of humans are more similar and more closely related
to chimpanzee sequencesthan to other human sequences(see Figure 12.238).What more
striking evidence of common ancestry could there be?
Among the many other ways in which molecular studies affirm the reality of evolution, consider just one more: molecular clocks. They are far from perfectly accurate, but
sequence differences between species nevertheless are roughly correlated with the time
since common ancestry, judged from other evidence such as biogeography or the fossil
record (see Chapters 2'and 4). The sequence differences do not simply encode the phg4q
typlgd{fele4gq that the organisms manifest, and the phenotypic differences themselves
are much less correlated with time since common ancestry No theory but evolution makes
sense of these patterns of DNA differences among species.
Centrnrik
Ccmeirrsamkcit
g e m e i n s . r n r eA b s t a m n rL rn g
nichtcoclierenrlc i'ser-r
rlogene /
S a t e l l i t e n - D \ A / I ' a i l l e. , , e e o i s t i s c h e " t r a n s l r o n i e r b a r cE l c m e n l e i
;r1lrnäcl'rtig
u n g l e i c h e sC r o s s i n g - o v e r
d r,rpiizii..rte
Oc.ne
Polvrnorphismen
H a u p t - F l i s t o k o r n p at i b i l i t ä t s S t - q u tn z en
m L r l e k u l . r r eU h l r - . n
'.1,-i.,rh,'ri.,-1.,.
I i,r f.'r*
h i,., 1
Biogeography
We noted in Chapter 6 that the geographic distributions of organisms provided Darwin
with abundant evidence of evolutiory and they have continued to do so. For example, the
distributions of many taxa correspond to geolbgical events such as the movement-of land
masses and the formation and dissolution of connection.sbetween them. We saw that the
phylogeny of Hawaiian species matches the sequenceby which the islands came into existence. We saw that diverse ecological niches in a region are typically filled not by the
same taxa that occupy similar niches in other parts of the world, but by different monophylg!4€Iqqp! that have undergone independent adapl!vg_I44i41iq4 (such as the anoles
of the Greater AnLilles). We sary as did Darwin, that an isolated region such as an island
is not populated by all the kinds of organisms that could thrive there, as we might suppose a thoughtful designer could arrange. Instead, whole groups are commordy missing,
and human-introduced species often come to dominate.
VerLrreitrrngen
Auflirsr-rng
irkologischt Niscl-ren
r-nouophr')eti schc.Cn-rpp.erl
a d a p t r rc R . r c t a t i o u
GnrßeAntillen
F a i l u r e so f t h e a r g u m e n t f r o m d e s i g n
Since God cannot be known directly, theologians such as Thomas Aqqtleq have long attempted to infer His characteristics from His works. Theologians have argued, for instance, that order in the universe, such as the predictable movement of celestial bodies,
implied that God must be orderly and rational, and that He created according to a plan.
From the observation that organisrr's have characteristicsthat sewe their survivaf it could
:
t7
Thomas von Acltrin
,
Himnrelskörper-
53()
C H A P T E R2 2
tvohh'oIIeurl
Segen
g n a r l e n l o sa u s g e l a c l - r t
Antrieb
Desigr.rargurlen t
Falce, Cegenstancl rles Spottes
Eventualitäten
rutli urc.ntärc(r'erkii urr-nerte)Organe
Bt'cken / Obc.rschenkelknocher.t
venvachscne Fliigeldecken / funkIior.rs]oseStatrbblätter ocler Stempel
r g e t r r . l r n t e e s c h l t c h t l i c h/ ' . r r r' I r r r _i i r r5r ' l -i'r ' l rz r r i l l r i r ' , ' r Z t r . t a n . l
cktotherur, u,echseln,alm
Aortenbiigt-n / Enc'lothelme,Gleich\\'.1rme
pentacl.rktvleliiinffingriee) Extre.mität
gelenkig
endosymbionlisch / I'}hotosynthese
zr:fällig
Inbegriff
Siclrelzellanämie
auf Kosten
homozVgot
heterozvroter Träger
in Ern ägur.rgzu ziehen
erhalten
Umstände
similarly be infefred that God is a rationaf intelligent designer who, furthermore, is beneficent: He not only conJerred on living things the boon of existence,but equipped them for
all their needs. Such a beneficent God would not create an imPerfect world; so, as the
philosopher Lerbniz said, this must be "the best of all possible worlds." (Leibniz's position was actually more complicated, but his phrase was mercilessly ridiculed by Voltaire
in his marvelous satire Candide.)The adaptive design of organisms, in fact, has long been
cited as evidence of an intelligent designer. This was the thrust of William Paley's (1831)
famous example: as the design evident in a watch implies a watchmaker, so the design
evident in organisms implies a designer of life. This "argument from design" has been renewed in the "intelligent design" version of creationism, and it is apparently the most frequently cited reason people give for believing in God (Pigliucci 2002).
Of course, Darwin made this particular theological argument passd by providing a naiural mechanism of design: natural selection. Moreoveq, Darwin and subsequent evolutionary biologists have described innumelable examples of biological phenomena that
are hard to reconcile with beneficent intelligent design. just as Voltaire showed (in Candide) that cruelties and disasters make a mockery of the idea that this is "the best of all
possible worlds," biology has shown that organisms have imperfections and anomalies
that can be explained only by the continggnclg! of history, and characteristics that make
sense only if natural selection has produced them. If "good design" were evidence of a
kindly, omnipotent designel, would "inferior design" be evidence of an unkind, incompetent, or handicapped designer?
Only evolutionary history can explain vestigial organs-the rudiments of once-functional features, such as the tiny, useless pelvis and femur of whales, the reduced wings
under the fused wing covers of some flightless beetles, and the nonfunctional stamens or
pistils of plants that have evolved separate-sexed flowers from an ancestral hermaphroditic condition. Likewise, only history can explain why the genome is full of "fossil" genes:
pseudogenes that have lost their function. Only the contingencies of history can explain
the arbitrary nature of some adaptations. For instance, whereas ectothermic ("coldblooded") tetrapods have two aortic arches, "warm-blooded" endotherms have only one.
This difference is probably adaptive, but can anything except historical chance explain
why birds have retained the right arch and mammals the left?
Becausecharacteristics evolve from pre-existing features, often undergoing changes in
functiory many feafures are poorly engineered, as anyone who has suffered lower back
pain or wisdom teeth can testify. Or-rcethe pentadactyl limb became developmentally
car-ralized,tetrapods could not evolve more than five digits even if they would be useful:
the extra " finger" of the giant panda's hand is not a true digit at all, and lacks the flexibiiity of true fingers because it is not plqlggi (see Figure 21.8). Similarly, animals would
certainly be better off if they could synthesize their own food, and corals do so by harboring endosymbiotic algae-but no animal is capable of photosynthesis.
If a designer were to equip species with a way to survive environmental change, it
might make sense to devise a Lamarckian mechanism, whereby genetic changes wouid
occur in response to need. Instead, adaptation is based on a combination of a random
process (mutation) that cannot be trusted to produce the needed variation (and often does
not) and a process that is the very epitome of waste and seeming cruelty (natural selection, which requires that great numbers of organisms fail to survive or reproduce). It
would be hard to imagine a crueler instance of nafural seiection than sickle-ceil anemia,
whereby part of the human population is protected against malaria at the expenqgof hundreds of thousands of other people, who are condemned to die because they are homozygous for a gene that happens to be worse for the malarial parasite than for heterozYgous carriers (see Chapter 12). Indeed, Darwin's theory of the cause of evolution was
widely rejected just because people found it so distasteful, even horrifying, to cgntemplate. And, of course, this process often does not preserve species in the face of change:
lirr"d *u äxtinct. Were they the prodilore than 99 percent of ali species that have
"n".
ucts of an incompetent designer? Or one that couldn't foresee that species would have to
adapt to changing circumstances?
-
SY
C I E N C EC, R E A T I O N I S N
AN
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EVOTUTIONAR
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531
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Many species become exti4c;! because of gql4petition, p.$de!iq4, and parasitism. Some
of these interactions are so appalling that Darwin was led to write, "What a book a devils' chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel
works of Nature!" Darwin knew of maggql9 that work their way up the !4q41-123$gges
into the brains of sheep, and wasp larvae that, having consumed the internal organs of
a living caterpillat burst out like the monsters in the movie Ällen. The life histories of parasites, whether parasitic wasp or human immunodeficiency virus, ill fit our concept of an
intelligent, kindly designe(, but are easily explained by natural selection (see Chapter 18).
No one has yet demonstrated a characteristic of any species that serves only to benefit
a different speciet or only to enhance the so-called balance of nature-for, as Darwin saw,
"such could not have been produced through natural selection." Becausenatural selection consists only of differential reproductive success,it results in "sel{ish" genes and
genotypes, some of which have results that are inexplicable by intelligent design (see
Chapter 14). We have seen that genomes are brimming with sequencessuch as transposable elements that increase their own numbers without benefiting the organism. We have
seen maternally tuansmitted cytople!r4!!€e4e! that cause male sterilitY in many plants,
and nuclear genes that have evolved to override them and restore male fertility. Such conflicts among genes in a genome are widespread. Are they predicted by intelligent design
theory? Likewise, no theory of design can predict or explain features that we ascribe to
sexual selection, such as males that remove the sperm of other males from the female's
or chemicals that enhance a male's reprodlrctive sllccess but shorten
replodgqlivell4!!,
his mate's life spen. Nor can we rationalize why a beneficent designer would shape the
many other selfish behaviors that natural selection explains, such as cannibalism, siblicide, and inJanticide.
: i o r b e n . r r r s / K o n k r r r r t ' r r zi I ' ] r , i L l , r Iir'rt o srltr.t'cklir'lt
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v r r l l u e p a c k tn r i i
m r i t t e r i i c h i i b e r t r a g t ' r r oC v t o p r l ; 5 p 1 . 1
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Evolution and its mechanisms, observed
Anyone can observe erosiory and geologists can measure the movement of continental
plates, which travel at up to 10 centimeters per year. No geologist doubts that these mechanisms, even if they accomplish only slight changes on the scale of human generations,
have shaped the Grand Canyon and have separated South America from Africa over the
course of millions of years. Likewise, biologists do not expect to see anything like the origin of mammals played out on a human time scale,but they have documented the mechanisms that will yield such grand changes, given enough time.
Evolution requires genetic variation, which originates by mutation. From decades of
genetic study of initially homozygous laboratory populations, we know that mutations
arise that have effects, ranging from very slight to drastic, on all kinds of phenotypic characters (see Chapter B). These mutations can provide new variation in quantitative characters, seemingly without limit. This variation has been used for millennia to develop
strains of domesticated plants and animals that differ in morphology more than whole
families of natr-rralorganisms do. In experimental studies of laboratory populations of microorganisms, we have seen new advantageous mutations arise and enable rapid adaptation to temperature changes, toxins, or other environmental stresses.Laboratory studies have documented the occurrence of the same kinds of mutations, at the molecular
level, that are found in natural populations and distingr"rish species. These mutations include base pair substitutions, gene duplications, chromosome rearrangements, and transposition of transposable elements. No geneticist or molecular biologist doubts that the
differences among species in their genes and genomes originated by natural mutational
processesthat by and large, are well understood.
We know also that most natural populations carry a great deal of genetic variation that
can yield rapid responsesto artificial or natural selection(seeChapters 9,7I, and 12).We
have seen allele frequency differences among recently established populations that can
be confidently attributed to genetic drift (seeChapter 10). Evolutionary biologists have
documented 1itera11y
hr,rndreds of examples of natural selection acting on genetic and phenotypic variation (see Chapters 12 and 13). They have described hundreds of casesin
which populations have responded to directional selection and have adapted to new en-
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C H A P T E R2 2
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reproduktive Isolatiorr
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vironmental factors, ranging from the evolution of resistance to insecticides, herbicides.
and antibiotics to the evolution of different diets (see Chapter 13).
Speciation generally takes a very long time, but some processes of speciation can also
be observed. Substantial reproductive isolation has evolved in laboratory populations,
and species of plants that apparently originated by polluploidy and by hybridization have
been "re-created" de novo by crossing their suspected parent forms and selecting for the
species' diagnostic characters (see Chapter 16).
hr summary, the major causesof evolution are knowry and they have been extensively
documented. The two major aspects of long-term evolutiorL anagenesis (changes of chaiacters within lineages) and cladogenesis (origin of two or more lineages from common
ancestors)/ are abündantly supported by evidence from every possible source, ranging
from molecular biology to paleontology. Over the past century, we have certainly learned
of evolutionary processesthat were formerly unknown; we now know for example, that
some speciesmay arise from hybridizatiory and that some DNA sequencesare mobile and
can cause mutations in other genes. But no scientific observations have ever cast serious
doubt on the reality of the basic mechanisms of evolution, such as natural seleclion" nor
on the reality of the basic historical patternt such as transformation of characters and the
origin of all known forms of life from common ancestors. Contrast this mountain of evidence with the evidence for supernatural creation or intelligent design: thereis no sucheaidencewhateuer.
Refuting Creationist Arguments
U n z u J ä r r g l i c l r k e i/t i r r E n t r a r r g e l t u r g
anderer l\4öglichkeiterr
kurz
Creationists attribute the existence of diverse organisms and their characteristics to miracles: direct supernatural intervention. As we have seen, it is impossible to predict miracles or to do experiments on supernatural processes, so creationists do not do original
research in support of their theory.* Thus "creafion science," rather than providing positive evidence of creatiory consists entirely of attempts to demonstrate the falsehood or
inadequacy of evolutionary science and to show that biological phenomena must, by default, be the products of intelligent design. Here are some of the most commonly encountered creationist arguments, together with capsule counterarguments.
1. Evolution is outside the realm of science becauseit cannot be observed.
Daseinsfolmer
Evolutionary changes have indeed been observed, as we saw earlier in this chapter.
In any case, most of science depends not on direct observation, but on testing hypotheses against the predictions they make about what we should observe. Observation of the postulated processesor entities is not required in science.
2. Evolution cannot be proved.
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Nothing in science is ever absolutely proved. "Facts" are hypotheses in which we can
have very high confidence because of massive evidence in their favor and the absence
of contradictory evidence. Abundant evidence from every area of biology and paleontology supports evolutiory and there exists no contradictory evidence.
3. Evolution is not a scientific hypothesis becauseit is not testable: no possible observations could refute it.
Many conceivable observations could refute or cast serious doubt on evolutiory such
as finding incontrovertibly mammalian fossils in incontrovertibly Precambrian rocks.
In contrast, any puzzling quirk of nature could be attributed to the inscrutabie will
and infinite power of a supernatural intelligencg so creationism is untestable.
"About the only quasi-exception to this statement was thet claim to have found commingled lternrischtl
human and dinosaur footprints in fossilized sediments in a riverbed in Texas, supposedly showing that .
these organisms were contemporaneous IZeitut'rro>:cnl. Even if this claim had pioved tobe true, it would
not have falsified evolution; but in any case, most creationists now acknowledge that the "humm" prilts _
are a mixture of fraudulent carvings {betriigcrische \4eißclarlreitenl and natural depressions [\ fr tiuitrngenJ.
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