## 1. The Origins of Darwin's Theory


### 1.1 Historiographical Issues



Charles Darwin's version of transformism has been the subject of
massive historical and philosophical scholarship almost unparalleled
in any other area of the history of science. This includes the
continued flow of monographic studies and collections of articles on
aspects of Darwin's theory (Richards and Ruse 2016; Ruse 2013a,
2009a,b, 2008; Ruse & Richards 2008; Hodge & Radick 2003
[2009]; Hosle & Illies [eds] 2005; Gayon 1998; Bowler 1996;
Depew & Weber 1995; Kohn 1985a). The continuous production of
popular and professional biographical studies on Darwin provide ever
new insights (Ruse et al. 2013a; Johnson 2012; Desmond & Moore
1991, 2009; Browne 1995, 2002; Bowlby 1990; Bowler 1990). In addition,
major editing projects on Darwin's manuscripts and
Correspondence, now completed through 1878, continue to reveal details
and new insights into the issues surrounding Darwin's own
thought (Keynes [ed.] 2000; Burkhardt et al. [eds] 1985-; Darwin
1836-1844 [1987]). The Cambridge Darwin Online website (see Other Internet Resources) serves as an international
clearinghouse for this worldwide Darwinian scholarship.



A long tradition of scholarship has interpreted Darwin's theory
to have originated from a framework defined by endemic British natural
history, a British tradition of natural theology defined particularly
by William Paley (1743-1805), the methodological precepts of
John Herschel (1792-1871), and the geological theories of
Charles Lyell (1797-1875). His conversion to the uniformitarian
geology of Charles Lyell and to Lyell's thesis of gradual change
over time during the voyage of the *HMS Beagle* (December
1831-October 1836) has been seen as fundamental in his formation
(Norman 2013; Herbert 2005; Hodge 1983a). Complementing this
predominantly anglophone historiography has been the
social-constructivist analyses emphasizing the origins of
Darwin's theories in British Political Economy (Young, 1985:
chps. 2, 4, 5). Recently, it has been argued that a primary generating
source of Darwin's inquiries was his involvement with the
British anti-slavery movement, a concern reaching back to his
revulsion against slavery developed during the *Beagle* years
(Desmond & Moore 2009).



A strain of revisionist historiography, on the other hand, has
de-emphasized some of the novelty of Darwin's views; questions
have been raised regarding the validity of the standard biographical
picture of the early Darwin; new emphasis has been placed on
Darwin's relations to the German Romantic movement, to British
and Scottish medical developments, and to his early formation in
Scottish science and philosophy (R.J. Richards 1999, 2002; Desmond
1989; Manier 1978). Such revisions to a long-standing historiography
in the understanding of the genesis of Darwinian theory are indebted
to the wealth of manuscripts and correspondence that have become
available since the 1960s and which are now electronically accessible
at the Darwin Online "Papers and Manuscripts" section (see
Other Internet Resources).



These materials have drawn attention to previously ignored aspects of
Darwin's biography. In particular, the importance of his
Edinburgh period from 1825-27, largely discounted in importance
by Darwin himself in his late *Autobiography*, has been seen as
critical for his subsequent development (Desmond & Moore 1991;
Hodge 1985). As a young medical student at the University of Edinburgh
(1825-27), Darwin developed a close relationship with the
comparative anatomist Robert Edmond Grant (1793-1874) through
the student Plinian Society, and in many respects Grant served as
Darwin's first mentor in science in the pre-*Beagle*
years (Desmond & Moore 1991, chp. 1). Through Grant he was exposed
to the transformist theories of Jean Baptiste Lamarck and the
Cuvier-Geoffroy debate centered on the Paris *Museum
nationale d'histoire naturelle* (see entry on 
evolutionary thought before Darwin,
Section 4). This Scottish period also developed in Darwin an abiding
interest in invertebrate zoology that would later emerge in full in
his important work on the barnacles (Stott 2004; Love 2002; Sloan
1985).



Similarly, there has been a new appreciation of the importance of
Darwin's work in physiological botany and entomology during his
studies in Cambridge from 1827-31 under the guidance of his
mentor John Stevens Henslow (1795-1861), who exposed him to the
physiological botany of Swiss botanist Alphonse De Candolle
(1806-93). Through Henslow he was also led to the writings of
John Herschel, Alexander von Humboldt (1769-1859), and Charles
Lyell. Deeper understanding is now possible concerning Darwin's
work in geology at Cambridge with Adam Sedgwick (1795-1873). All
of this has considerably deepened the understanding of his scientific
and intellectual preparation for the theoretical work that transpired
during the voyage of the *H.M.S. Beagle* (Sloan 2003b
[2009]). Some scholars now interpret Darwin's initial
reflections on transformism to have developed from lines of thought
stimulated by Humboldt's version of German philosophy of nature
as much as from the traditional sources usually assumed in Lyell,
Herschel and British natural theology (R.J. Richards 2005, 2002:
chp. 14). This scholarly work, while not rejecting the importance of
traditional British sources, has revealed the multiplicity of origins
of Darwin's reflections that display the interaction of British
traditions with Continental developments in life science and
philosophy, including those of German origin (R.J. Richards 2002;
Sloan 2003a, 2007).



The continued scholarly interest in the origins of Darwin's
theory reflects not only the concerns of historians of science, but
also those who see a continued relevance of Darwin's own
writings as sources of creative reflection for contemporary work in
evolutionary biology (Gayon 2003). This phenomenon, however, presents
difficulties for the historical understanding of Darwinism.
Particularly within anglophone philosophy of biology, the emphasis on
the lines of the development of Darwin's evolutionary theory
that have led to the consensus position achieved in the so-named
"Synthetic" theory of evolution of the 1930s (Smocovitis
1996; Mayr & Provine [ed.] 1980; Provine 1971), has tended to
obscure the complex history of Darwin's own theoretical
reflections and the history of Darwinian theory since 1859 (Depew
& Weber 1995; Bowler 1983).



These internal complexities in the heritage of Darwin's works
have shaped Darwinism into more than one tradition, with pre-existing
social and intellectual contexts playing a critical role in the
interpretation of Darwin's achievement. French biology, for
example, still pays greater respect to Lamarck than is true in
anglophone literature (Laurent [ed.] 1997). Several commentators
currently seek to de-emphasize the contrasts between the presumably
failed theories of Lamarck and those of Darwin that figure largely in
British and American literature, or else see some greater
compatibility between a "molecularized" understanding of
evolution and Lamarckianism (Gissis & Jablonka [eds] 2011). The
long heritage of Kantianism and German Idealism has influenced lines
of the German interpretations of Darwin up to the present (Hosle
& Illies [eds] 2005). The general importance of prior social and
intellectual context in the reception of Darwin's work is a
topic of active research that will be summarized in greater detail
below.


### 1.2 Darwin's Early Reflections



In its historical origins, Darwin's theory was different in kind
from its main predecessors in important ways (Ruse 2013b; see also the
entry on 
 evolutionary thought before Darwin).
 Viewed against a longer historical scenario,
Darwin's theory does not deal with cosmology or the origins of
the world and life through naturalistic means, and therefore was more
restricted in its theoretical scope than its main predecessors
influenced by the reflections of Buffon, Herder, and German
*Naturphilosophen.* It also differed from the historical
developmentalism of his German contemporary, the paleontologist
Heinrich G. Bronn (Gliboff 2008, 2007). This restriction also
distinguished Darwin's work more immediately from the grand
evolutionary cosmology put forth anonymously in 1844 by the Scottish
publisher Robert Chambers (1802-71) in his immensely popular
*Vestiges of the Natural History of Creation*, a work which in
many respects prepared Victorian society in England, and pre-Civil War
America for general evolutionary theories (Secord 2000; MacPherson
2015). It also distinguished it from the theories of his contemporary
Herbert Spencer (1820-1903) summarized below.



Darwin's theory first took written form in reflections in a
series of notebooks begun during the latter part of the
*Beagle* voyage and continued after the return of the
*Beagle* in October of 1836. His reflections on the possibility
of species change are first entered in March of 1837 ("Red
Notebook") and are developed in the other notebooks (B-E)
through July of 1839 (Darwin 1836-1844 [1987]; Hodge 2013a,
2003). Beginning with the reflections of the third or "D"
Notebook, composed between July and October of 1838, Darwin first
worked out the rudiments of what was to become his theory of natural
selection. In the parallel "M" and "N"
Notebooks, dating between July of 1838 and July of 1839, and in a
loose collection called "Old and Useless Notes", dating
from approximately 1838-40, he also developed many of his main
ideas on human evolution that would only be made public in the
*Descent of Man* of 1871 (see below).


 To summarize a complex issue, these Notebook reflections show
Darwin proceeding through a series of stages in which he first
formulated a general theory of the transformation of species from
common ancestry. He then attempted to work out a causal theory of
life that would explain the tendency of life to complexify and
diversify (Hodge 2013a, 2003, 1985; Sloan 1986). This causal inquiry
into the underlying nature of life , and the explanation of
life's innate tendency to develop and complexify, was then
replaced by a shift in focus away from inner tendencies of life. It
was replaced by a concern with external forces controlling population,
which was, following Thomas Malthus's (1766-1834), assumed
to expand geometrically. This shift allowed him to develop the
implications of population increase for the transformation of
species.



By universalizing the Malthusian "principle of
population", Darwin introduced an "inertial"
principle into his theory, although such language is never used in his
text. Newton's first law, for example, established his physical
system upon the tendency of a body in motion to persist either at rest
or in uniform motion in a straight line, requiring a causal
explanation for any deviations from this initial state. But Newton did
not seek a deeper metaphysical explanation for this tendency.
Similarly, the principle of population supplied Darwin with the
assumption of an initial dynamic state of affairs that was not itself
explained within the theory--there is no attempt to account
causally for this tendency of living beings universally to reproduce
geometrically. The principle of population might therefore be regarded
as functioning axiomatically, defining a set of initial conditions
from which any deviance from this ideal state demands explanation.
This theoretical shift enabled Darwin to bracket his earlier efforts
to develop a causal theory of life, and focus instead on the means by
which the dynamic force of population was controlled. This allowed him
to emphasize how this control on population worked in company with the
phenomenon of slight individual variation and changing conditions of
life to produce a gradual change of form and function. Darwin would
later claim that he was able empirically to support the claim that
living populations do tend to increase in this way, but he does not
offer a causal theory of life to explain this tendency
(*Origin* 1859: chp. 3, 63-68).


## 2. Darwinian Evolution


### 2.1. The Concept of Natural Selection



The primary distinguishing feature of Darwin's theory that separates it
from previous explanations of species change centers on the causal
explanation he offered for how this process occurred. Prior theories,
such as that of Jean-Baptiste Lamarck, relied on the inherent dynamic
properties of matter, or in some of the German reflections, on special
dynamic forces, such as those building upon the "Formative
Drive" (*Bildungstrieb*) theory of Johann Blumenbach
(1752-1840) (Zammito 2018: chps. 7-9). The change of
species was not, in these pre-Darwinian efforts, explained through an
adaptive process. Darwin's emphasis after Notebook D on the
factors controlling population increase, rather than on a dynamic
theory of life grounded in vital forces, however, accounts for many of
the differences between Darwin's theory and those of his
predecessors and contemporaries.



These differences can be summarized in the concept of natural
selection as a central ingredient of Darwinian theory. However, the
exact meaning of this concept, and the varying ways he stated the
principle in the *Origin* over its six editions
(1859-1872), has given rise to multiple interpretations of the
meaning of this principle in the history of Darwinism.



One way to see the complexity of Darwin's own thinking on these
issues is to follow the textual development of this concept between
the close of the Notebook period (1839) and the publication of the
*Origin of Species* in 1859. This period of approximately
twenty years involved Darwin in a series of reflections that form
successive strata in the final version of his theory of the evolution
of species. Understanding the historical sequence of these
developments also has significance for subsequent controversies over
this concept and the different readings of the *Origin* as it
went through successive editions, and as it was received in other
cultural contexts (see below,
 Section 3).
 It also has some bearing on assessing Darwin's relevance for
more general philosophical questions, such as those surrounding the
teleology of nature.



The earliest set of themes in the manuscript elaboration of natural
selection theory can be characterized as those developed through a
strong analogy between human art and the workings of nature
(Theunissen 2013). As this was expressed in the first coherent draft
of the theory, a 39-page manuscript written in 1842, this discussion
transferred the concept of selection of forms by human agency in the
creation of the varieties of domestic animals and plants, to the
active selection in the natural world by an almost conscious agency, a
"being more sagacious than man (not an omniscient
creator)" (Darwin 1842 [1909: 6] [1996: 91]). This agency
selects out those features most beneficial to organisms in relation to
conditions of life, analogous in its action to the selection by man on
domestic forms in the production of different breeds. Interwoven with
these references to an almost Platonic demiurge are appeals to the
selecting power of an active "Nature":



> 
> 
> Nature's variation far less, but such selection far more rigid
> and scrutinizing[....] Nature lets [an] animal live, till on
> actual proof it is found less able to do the required work to serve
> the desired end, man judges solely by his eye, and knows not whether
> nerves, muscles, arteries, are developed in proportion to the change
> of external form. (1842 [1909: 9] [1996: 93])
> 
> 
> 



These themes were continued in the 230 page draft of his theory of
1844. Again he referred to the selective action of a wise imaginary
being whose selection was made with greater foresight and wisdom than
human selection. This agency worked as a secondary cause in a larger
plan of a superintending creator, allowing that 



> 
> 
> the process of selection could go on adapting, nicely and wonderfully,
> organisms, if in ever so small a degree plastic, to diverse ends. I
> believe such secondary means do exist. (Darwin 1844a [1909: 87] [1996:
> 103])
> 
> 
> 



Darwin returned to these issues in 1856, following a twelve-year
period in which he published his *Geological Observations on the
Volcanic Islands* (1844b), the second edition of his *Journal
of Researches* (1845), *Geological Observations on South
America* (1846), the four volumes on fossil and living barnacles
(1851, 54, 55), and *Geological Observations on Coral Reefs*
(1851). In addition, he had published several smaller papers on
invertebrate zoology, on geology, and had reported on his experiments
on the resistance of seeds to salt water, a topic that would be of
importance in his explanation of the population of remote islands.



These intervening inquiries, conducted between 1844 and 1856,
positioned Darwin to deal with the question of species permanence
against an extensive empirical background. The initial major synthesis
of these investigations takes place in his long manuscript, or
"Big Species Book", commenced in 1856, known in current
scholarship as the "Natural Selection" manuscript. This
formed the immediate background text behind the published
*Origin*. Although incomplete, "Natural Selection"
provides insights into many critical issues in Darwin's
thinking. It was also prepared with an eye to the scholarly community.
This distinguishes its form of argument from that of the subsequent
"abstract" which became the published *Origin of
Species*. "Natural Selection" contained tables of
data, references to scholarly literature, and other apparatus expected
of a non-popular work, none of which survived in the published
*Origin*.



The "Natural Selection" manuscript also contained some new
theoretical developments of relevance to the concept of natural
selection that are not found in earlier manuscripts. Scholars have
noted the introduction in this manuscript of the "principle of
divergence", the thesis that organisms under the action of
natural selection will tend to radiate and diversify within their
"conditions of life"--the contemporary name for the
complex of environmental and species-interaction relationships (Kohn
1985b, 2008). Although the concept of group divergence under the
action of natural selection might be seen as an implication of
Darwin's theory from his earliest formulations of the 1830s,
nonetheless Darwin's explicit definition of this as a
"principle", and its discussion in a long later insertion in the
"Natural Selection" manuscript, suggests its importance
for Darwin's mature theory. The principle of divergence was now
seen by Darwin to form an important link between natural variation and
the conditions of existence under the action of the driving force of
population increase.



Still evident in the "Natural Selection" manuscript is
Darwin's implicit appeal to some kind of teleological ordering
of the process. The action of the "wise being" of the
earlier manuscripts, however, has now been given over entirely to the
action of a selective "Nature", now referred to in the
traditional feminine gender. This Nature,



> 
> 
> ...cares not for mere external appearance; she may be said to
> scrutinise with a severe eye, every nerve, vessel & muscle; every
> habit, instinct, shade of constitution,--the whole machinery of
> the organisation. There will be here no caprice, no favouring: the
> good will be preserved & the bad rigidly destroyed.... Can we
> wonder then, that nature's productions bear the stamp of a far
> higher perfection than man's product by artificial selection.
> With nature the most gradual, steady, unerring, deep-sighted
> selection,--perfect adaption [sic] to the conditions of
> existence.... (*Natural Selection* 1856 [1974:
> 224-225])
> 
> 
> 



The language of this passage, directly underlying statements about the
action of "natural selection" in the first edition of the
published *Origin*, indicates the complexity in the exegesis of
Darwin's meaning of "natural selection" when viewed
in light of its historical genesis (Ospovat 1981). The parallels
between art and nature, the intentionality implied in the term
"selection", the notion of "perfect"
adaptation, and the substantive conception of "nature" as
an agency working toward certain ends, all render Darwin's views
on teleological purpose more complex than they are typically
interpreted from the standpoint of contemporary Neo-selectionist
theory (Lennox 1993, 2013). As will be discussed below, the changes
Darwin subsequently made in his formulations of this concept over the
history of the *Origin* lead to different conceptions of what
he meant by this principle and underlie most contemporary meanings of
natural selection.



The hurried preparation and publication of the *Origin* between
the summer of 1858 and November of 1859 was prompted by the receipt on
June 18 of 1858 of a letter from Alfred Russel Wallace that outlined
his remarkably similar views on the possibility of continuous species
change under the action of a selection upon natural variation. This
event had important implications for the subsequent form of
Darwin's published argument. Rapidly condensing the detailed
arguments of the "Natural Selection" manuscript into
shorter chapters, Darwin also universalized several claims that he had
only developed with reference to specific groups of organisms, or
which he had applied only to more limited situations in the
manuscript. This resulted in a presentation of his theory at the level
of broad generalization. The absence of tables of data, detailed
footnotes, and references to the secondary literature in the published
version also resulted in predictable criticisms which will be
discussed below in
 Section 3.


### 2.2. The Central Argument of the *Origin*



The structure of the argument of the *Origin* has been the
topic of considerable literature and can only be summarized here
 (Darwinism,
 this encyclopedia; Hodge 2013b; Hoquet 2013; Waters 2003; Depew 2008; Ruse 2008;
Lennox 2005). Darwin himself described his book as "one long
argument". The exact nature of this argument is, however, not
immediately transparent, and alternative interpretations have been
made of his reasoning and rhetorical strategies in formulating his
evolutionary theory.



The scholarly reconstruction of Darwin's methodology employed in
the *Origin* has taken two primary forms. One approach has been
to reconstruct it from the standpoint of currently accepted models of
scientific explanation, sometimes presenting it as a formal deductive
model (Sober 1984). Another, more historical, approach interprets his
methodology in the context of accepted canons of scientific
explanation found in Victorian discussions of the period (Ruse 2013b;
Waters 2003; Hull 2003; Lewens 2008; Ruse 2008; Lennox 2005; Hodge
1983b). The degree to which Darwin did in fact draw from the available
methodological discussions of his contemporaries--John Herschel,
William Whewell, John Stuart Mill--is not fully clear from
available documentary sources. The claim most readily documented, and
defended particularly by M. J. S. Hodge (1977, 1983a), has emphasized
the importance of John Herschel's *A Preliminary Discourse on
the Study of Natural Philosophy* (1830), which Darwin read as a
young student at Cambridge prior to his departure on the *HMS
Beagle* in December of 1831. In Herschel's writings he would
have encountered the claim that science seeks to determine "true
causes"--*verae causae*. This concept Newton had
specified in the *Principia* as the third of his "Rules
of Reasoning in Philosophy" (see the entry on
 Newton's philosophy, 
 Section 4). This was
to be the goal of scientific explanation. Such causes, in
Herschel's formulation, were those necessary to produce the
given effects; they were truly active in producing the effects; and
they adequately explained these effects (Herschel 1830; Lennox 2005;
Waters 2003). These criteria distinguished a satisfactory scientific
account from the simple "saving of phenomena" by plausible
explanations in the tradition of scientific conventionalism. The
impact of Herschel's arguments on Darwin's intellectual
development was evidently profound, although there is no direct
textual reference to Herschel's concept of a *vera causa*
itself in the Notebooks and other early writings.



The other plausible methodological source for Darwin's mature
reasoning was the work of his older contemporary and former Cambridge
mentor, the Rev. William Whewell (1794-1866), whose three-volume
*History of the Inductive Sciences* (1837) Darwin read with
care after his return from his round-the-world voyage. Again, the
impact of Whewell's explicit theory of scientific method, as set
forth in his *Philosophy of Inductive Science* (first ed. 1840)
in the pre-*Origin* period is difficult to document, with no
direct evidence of the reading of Whewell's *Philosophy*
in the Darwin reading Notebooks or *Correspondence* from his
formative years before the publication of the *Origin*.



Nevertheless, a plausible argument has been made that the actual
structure of Darwin's text is more closely similar to a
"Whewellian" rather than to a "Herschelian"
model of argument (Ruse 1975, 2013c). In Whewell's 1840 account, the emphasis of
scientific inquiry is, as Herschel had also argued, to be placed on
the discovery of "true causes". But evidence for the
determination of a *vera causa* was to be demonstrated by the
ability of disparate phenomena to be drawn together under a single
unifying "Conception of the Mind", exemplified for Whewell
by Newton's universal law of gravitation. This
"Consilience of Inductions", as Whewell termed this
process of theoretical unification under a few simple concepts, was
achieved only by true scientific theories employing true causes
(Whewell 1840: xxxix). In a restatement of this principle in a revised
edition of his *Philosophy of Inductive Science* published only
a year before the *Origin*, Whewell argued that 



> 
> 
> the cases in which inductions from classes of facts altogether
> different have thus *jumped together*, belong only to the best
> established theories which the history of science contains. (Whewell
> 1858: 88) 
> 
> 
> 



It has therefore been argued that Darwin's theory fundamentally
produces this kind of consilience argument, and that his methodology is more properly aligned with that of Whewell.



In rhetorical structure, the *Origin* more evidently develops
what can be termed a "constructive" argument, with a
complex style of presentation indebted to what has been called
"situated argumentation", similar to the views developed
by contemporary Oxford logician and rhetorical theorist Richard
Whately (1787-1863) (Depew 2008). It proceeds by drawing the
reader into Darwin's world by personal narration as it presents
a series of limited issues for acceptance in the first three chapters,
none of which required of the reader a considerable leap of
theoretical assent, and most of which, such as natural variation and
Malthusian population increase, had already been recognized in some
form in the literature of the period.



These ingredients are then assembled together in chapter four into a
remarkable synthesis that rapidly extends the claims by generalization
to cover the full range of life, both in time and in space. With
Darwin's carefully-designed rhetorical strategy of presentation,
only by chapter four would the reader know the full character and
broad implications of the claims being developed in the early
chapters. By the end of that chapter, the reader would be presented
with a remarkably comprehensive theory of the relations of living
forms, and the mode of their origin, both in the present and in the
past history of the planet.



Opening with a pair of chapters that draw upon the art-nature analogy
developed in the manuscripts, Darwin framed the argument with an
account of the probable origin of domestic animals, and by inference,
of domesticated plants (Theunissen 2013). These forms are presumed to
have arisen through the action of human selection on the slight
variations existing between individuals within the same species. A
possible interpretation of this process as implying directional, and
even intentional, selection, was at the same time downplayed in the
published work through the importance given by Darwin to the role of
"unconscious" selection, a concept not encountered in the
Natural Selection manuscript. This denotes the selection practiced
even by aboriginal peoples who simply seek to maintain the integrity
of a breed by preserving the best forms. The domestic breeding analogy
is, however, more than a decorative rhetorical strategy. It repeatedly
functions for Darwin as the principal empirical example to which he
could appeal at several places in the text as a means of visualizing
the working of natural selection in nature, and this appeal remains
intact through the six editions of the *Origin*.



From this model of human selection working on small natural variations
to produce the domestic forms, Darwin then developed in the second
chapter the implications of "natural" variation, delaying
discussion of the concept of natural selection until chapter four. The
focus of the second chapter introduces another important issue. Here
he extends the discussion of variation developed in chapter one into
an attack on the traditional "Linnaean" understanding of
classification as a sorting out of species by means of essential
defining properties. It is in this chapter that Darwin most explicitly
develops his own position on the nature of organic species in relation
to his theory of descent. It is also here that he sets forth the
ingredients for his attack on species "essentialism".



Darwin's analysis of the "species question" is a
complex issue that has many implications for how his work was read by
his contemporaries and successors. This still forms a topic of
extensive discussion in the literature (see
 species
 and
 Darwinism,
 this encyclopedia; Mallet 2013; Hodge 2013b; R.A. Richards 2010; Wilkins 2009;
Stamos 2007; Sloan 2008, 2013). His sometimes contradictory statements
on this issue--alternating between overt denials of the reality
of species in some places, and clear affirmation of the reality of
species in others--have been seen by some scholars as an
intentional rhetorical strategy (Stamos 2007; Beatty 1985).



Prior tradition had been heavily affected by Buffon's
novel conception of biological species in which he made a sharp
distinction between "natural" species defined by such
properties as fertile interbreeding, and "artificial"
species and varieties defined by morphological traits and measurements
upon these (see the entry on
 evolutionary thought before Darwin,
 Section 3.3). This distinction was utilized selectively by Darwin. Particularly as
conceptualized by German natural historians of the early
nineteenth-century, "Buffonian" species were defined by
the unity of common descent, and distinguished by their historical and
ontological character from the taxonomic species of Linnaean natural
history. This distinction between "natural" and
"logical" species had maintained a distinction between
problems of practical classification of preserved specimens, and those
relating to the unity of natural species, which most maintained as
fixed on the basis of reproductive unity and the sterility criterion
(Sloan 2008).



Remarkable in Darwin's argument, however, is the way in which he
draws selectively from these preexistent traditions to undermine the
species "realism" assumed within these. One
tradition--what can be considered in his immediate context the
Linnaean tradition--regarded species in the sense of universals
of logic or class concepts, whose "reality" rested in many
cases on divine creation. The alternative "Buffonian"
tradition viewed species in the sense of material lineages of descent
whose fixity was determined by some kind of immanent principle, such
as an "internal mold" or specifying vital force (see
 evolutionary thought before Darwin
 3.3). The result in Darwin's hands is a complex interweaving of
concepts of varieties, races, sub-species, tribes, and natural
families that can be shown to represent different traditions of
discussion in the literature of the period. This creative conflation
also led to many confusions about how Darwin actually did conceive of
species and species change in time (Sloan 2008).



Darwin addresses the species question by raising the problems caused
by natural variation in the practical discrimination of taxa at the
species and varietal levels. Although the difficulty of taxonomic
distinctions at this level was a well-recognized problem in the
literature of the time, he subtly transforms this *practical*
problem into a *metaphysical* ambiguity--the fuzziness of
formal taxonomic distinctions is seen to imply a similar ambiguity of
"natural" species boundaries.



For example, natural variation is employed by Darwin in chapter two of
the *Origin* to break down the distinction between species and
varieties as these concepts were commonly employed in the practical
taxonomic literature. The arbitrariness apparent in making
distinctions, particularly in plants and invertebrates, meant that
such species were only what "naturalists having sound judgment and wide experience" defined them to
be (*Origin* 1859: 47). These arguments form the basis for
claims by his contemporaries that Darwin was a species
"nominalist", who defined species only as conventional and
convenient divisions of a continuum of individuals.



But this feature of Darwin's discussion of species only in part
captures the complexity of his argument. Drawing also on the tradition
of species realism developed within the Buffonian tradition, Darwin
also affirmed that species and varieties are defined by common descent
and material relations of interbreeding. Darwin then employed the
ambiguity of the distinction between species and varieties created by
taxonomic variation in practical taxonomy to undermine the ontological
fixity of "natural" species. Varieties are not simply the
formal taxonomic subdivisions of a natural species as conceived in the
Linnaean tradition. They are, as he terms them,
"incipient" species (*Origin* 1859: 52). This
subtly transformed the issue of local variation and adaptation to
circumstances into a primary ingredient for historical evolutionary
change. The conclusions to be drawn from this argument were, however,
only to be revealed in chapter four of the text.



Before assembling the ingredients of these first two chapters, Darwin
then introduced in chapter three the concept of a "struggle for
existence". This concept is introduced in a "large and
metaphorical sense" that included different levels of organic
interactions, from direct struggle for food and space to the struggle
for life of a plant in a desert. Although described as an application
of Thomas Malthus's parameter of geometrical increase of
population in relation to the arithmetical increase of food supply,
Darwin's use of this concept in fact reinterprets
Malthus's principle, which was formulated only with reference to
human population in relation to food supply. It now becomes a general
principle governing all of organic life. Thus the organisms comprising
food itself would also be included. Through this universalization, the
controls on population becomes only in the extreme case grounded
directly on the traditional Malthusian limitations of food and space.
Normal controls are instead exerted through a complex network of
relationships of species acting one on another in predator-prey,
parasite-host, and food-web relations. This profound revision of
Malthus's arguments rendered Darwin's theory deeply
"ecological" as this term would later be employed. The abundance of red clover in England Darwin sees as dependent on the numbers of pollinating humble bees which are controlled by mice, and these are controlled by the number of cats, making cats the determinants of clover abundance. The
abundance of Scotch Firs is limited by the number of cattle, to cite
two examples employed by Darwin (*Origin* 1859: 72-74).
This recognition of complex species-species interactions as the
primary means of population control also prevents one from reading the
*Origin* as a simple extension of British political economy and
the competition embedded in Victorian industrialization to the natural
world.



With the ingredients of the first three chapters in place, Darwin was
positioned to assemble these together in his culminating fourth
chapter on natural selection. In this long discussion, Darwin develops
the main exposition of his central theoretical concept. For his
contemporaries and for the subsequent tradition, however,
Darwin's concept of "natural" selection was not
unambiguously clear for reasons we have outlined above, and these
unclarities were to be the source of several persistent lines of
disagreement and controversy. It is not clear, for example, whether
Darwin conceives of natural selection as an *efficient* or as a
*final* cause; whether it is an emergent *result* of
other causes; or if it is a simple *description* of the working
together of several independent causal factors without its own causal
status. Judging from the text of the *Origin* itself, it is
difficult to verify the claim that natural selection was itself
considered by Darwin to be a *vera causa* in Herschel's
sense. The importance of the *vera causa* principle for
Darwin's argument has been claimed by several scholars (Hodge
2013b; Waters 2003 [2009:
124-27]). But from textual evidence, Darwin reserved this designation in the
*Origin* for "community of descent", for the causes
of "ordinary generation", or even for the mistaken beliefs
of "special creationists" (*Origin* 1859: 159, 352,
482; Depew 2008: 243).



In the initial definition of natural selection presented in the first
edition of Darwin's text, it is characterized as
"preservation of favourable variations and the rejection of
injurious variations" (*Origin* 1859: 81). When Darwin
elaborated on this concept in chapter four of the first edition, he
continued to describe natural selection in language suggesting that it
involved intentional selection, continuing the strong art-nature
parallel found in the manuscripts. For example:



> 
> 
> As man can produce and certainly has produced a great result by his
> methodical and unconscious means of selection, what may not nature
> effect? Man can act only on external and visible characters: nature
> cares nothing for appearances, except in so far as they may be useful
> to any being. She can act on every internal organ, on every shade of
> constitutional difference, on the whole machinery of life. Man selects
> only for his own good; Nature only for that of the being which she
> tends. Every selected character is fully exercised by her; and the
> being is placed under well-suited conditions of life. (*Origin*
> 1859: 83)
> 
> 
> 



The manuscript history behind such passages prevents the simple
discounting of these statements as mere rhetorical imagery. As we have
seen, the parallel between intentional human selectivity and that of
"nature" formed the original model upon which the concept
of natural selection was originally constructed.



Criticisms that quickly developed over the overt intentionality
embedded in such passages, however, led Darwin to revise the argument
in editions beginning with the third edition of 1861. From this point
onward he explicitly downplayed the intentional and teleological
language of the first two editions, denying that his appeals to the
selective role of "nature" were anything more than a
literary figure, and he moved decisively in the direction of defining
natural selection as the description of the action of natural laws
working upon organisms rather than as an efficient or final cause of
life. He also regrets in his *Correspondence* his mistake in
not utilizing the designation "natural preservation"
rather than "natural selection" to characterize his
principle (letter to Lyell 28 September 1860, Burkhardt et al. 1993 8:
397; also see
 Darwin Correspondence Project in Other Internet Resources).
 The adoption in the fifth edition of 1869 of contemporary Herbert
Spencer's designator, "survival of the fittest"
(Spencer 1864: 444-445; *Origin* 1869: 72), as a synonym
for "natural selection", further emphasized this shift of
meaning away from the concept that can be extracted from the early
texts and drafts. Thus the formulations of the principle in the final
statements of the late 1860s and early 70s underlie the tradition of
later "mechanistic" and non-teleological understandings of
natural selection, a reading developed by his disciples who, in the
words of David Depew, "had little use for either his natural
theodicy or his image of a benignly scrutinizing selection"
(Depew 2008: 253).



The conceptual synthesis of chapter four also introduced discussions
of such matters as the conditions under which natural selection most
optimally worked, the role of isolation, the causes of the extinction
of species, and the principle of divergence. Many of these points were
made through the imaginative use of "thought experiments"
in which Darwin constructed possible scenarios through which natural
selection could bring about substantial change. Although these were
not regarded by his critics as empirical evidence for his claims, it
has been argued that these assisted Darwin in satisfying certain
criteria of adequacy as set forth by John Herschel's
methodological canons (Lennox 2005). One prominent way Darwin captured the complexity of this process is reflected in the single diagram to appear in all the
editions of the *Origin* (Velasco 2013). In this illustration
was summarized the image of gradual change from common ancestral
points, the depiction of the frequent extinction of most lineages, the
general tendency of populations to diverge and fragment under the
pressure of population increase, and a way of envisioning relations of
taxonomic affinity to time. It also depicted the persistence of some
forms that are unchanged over long geological periods in which stable
conditions prevail.



![Graph labeled on the horizontal-axis with the letters A to L and on the vertical-axis with Roman numerals I to XIV. From A branch up several dashed lines; all but two stop before reaching vertical-level I; from those two branch up several more dashed lines, some stop before the next vertical-level those that don't sprout up more lines, repeat though in some cases no line from a particular branch reaches the next vertical-level. Further description in the text following.](treediagram.png)

Figure: Tree of life diagram from
*Origin of Species* (*Origin* 1859: between pages 116
and 117).




Remarkable about Darwin's diagram of the tree of life is the
relativity of its coordinates. It is first presented as applying only
to the divergences taking place at the varietal level, with varieties
represented by the small lower-case letters within species A-L
of a "wide ranging genus", with the horizontal time
coordinates measured in terms of a limited number of generations.
However, the attentive reader could quickly see that Darwin's
destructive analysis of the distinction between "natural"
and "artificial" species and the relativity of the
species-variety distinction, worked out in chapter two, allowed this
diagram to represent eventually all organic relationships, from those
at the non-controversial level of diverging varieties within fixed
species, to those of the relations of species within different genera.
Letters A-L could also represent taxa at the level of Genera,
Families or Orders. The diagram can thus be applied to relationships
between all levels of the Linnaean hierarchy with the vertical
coordinates representing potentially vast expanses of time, and the
horizontal coordinates the degree of taxonomic divergence over time.
In a very few pages of argument, the diagram was generalized to
represent the most extensive group relations, encompassing the whole
of geological time. Extension of the dotted lines at the bottom could
even suggest, as Darwin argues in the last paragraph of the book, that
all life was a result of "several powers, having been originally
breathed into a few forms or into one" (*Origin* 1859:
490). This could suggest a naturalistic origin of original forms
either by material emergence, or through the action of a vitalistic
power of life. It could also be read as implying the action of a
supernatural cause.



In response to criticisms of his unclarity on this latter point,
Darwin quickly added to the final paragraph in the second edition of
1860 the phrase "by the Creator" (1860: 484), which
remained in all subsequent editions. Coupled with the quotations on
the frontispiece that remained in all editions of the work, this could
imply for some readers Darwin's intent to locate work within the
tradition of British natural theology and the long tradition running
back to the Scholastics that conceptualized creation by secondary law.
Conceptual space was thereby created for a reading of the
*Origin* by some contemporaries, notably by the Harvard
botanist Asa Gray (1810-88), as compatible with traditional
natural theology (Gray 1860; Lennox 2013).



The sweep of the theoretical generalization that closed the natural
selection chapter, one restated even more generally in the final
paragraph of the book, required Darwin to deal with several obvious
objections to the theory that would occupy him through the numerous
revisions of the text between 1859 and 1872. As suggested by David
Depew, the rhetorical structure of the original text developed in an
almost "objections and response" structure that resulted
in a constant stream of revisions to various editions of the original
text as Darwin engaged his opponents (Depew 2008; Peckham 1959
[2006]). Anticipating at first publication several obvious lines of
objection, Darwin devoted much of the text of the original
*Origin* to offering a solution in advance to predictable
difficulties. As Darwin outlined these main lines of objection, they
included first the apparent absence of numerous slight gradations
between species, both in the present and in the fossil record, of the
kind that would seem to be predictable from the gradualist workings of
the theory (chps. 6, 9). Second, the existence of organs and
structures of extreme complexity, such as the vertebrate eye,
structures that had since the writings of Galen in Hellenistic
antiquity served as a mainstay of the argument for external
teleological design, needed some plausible explanation (chp. 6).
Third, the evolution of the elaborate instincts of animals and the
puzzling problem of the evolution of social insects that developed
sterile neuter castes, proved to be a particularly difficult issue for
Darwin in the manuscript phase of his work and needed some account
(chp. 7). As a fourth major issue needing attention, the traditional
distinction between natural species defined by interfertility, and
artificial species defined by morphological differences, first dealt
with in Chapter Two, required an additional chapter of analysis in
which he sought to undermine the absolute character of the
interbreeding criterion as a sign of fixed natural species (chp.
8).



As a fifth topic, in chapter ten, Darwin developed his position on the
fossil record. At issue was whether the known fossil record displays a
gradual progression of forms from simple to complex, as might be
argued by Lamarckian transformists, or whether it supported the claim
for the persistence of major groups throughout the record as might be
held by someone endorsing the tradition of Cuvier (see the entry on
 evolutionary thought before Darwin,
 Section 4.1). The thesis of geological progressionism had in fact
been denied by none other than Darwin's great mentor in geology,
Charles Lyell in his *Principles of Geology* (1830-33;
Desmond 1984; Bowler 1976). Darwin defended the progressionist view in
this chapter.



To each of the lines of objection to his theory, Darwin offered his
contemporaries plausible, if not for many critics compelling, replies
(Hull 1973). Additional arguments were worked out through the
insertion of numerous textual insertions over the five revisions of
the *Origin* between 1860 and 1872, including the addition of a
new chapter to the sixth edition dealing with
"miscellaneous" objections. For reasons related both to
the condensed and summary form of public presentation, and also as a
reflection of the bold conceptual sweep of the theory, the primary
argument of the *Origin* could not gain its force from the data
presented by the book itself. Instead, it presented an argument from
unifying simplicity, gaining its force from the ability of
Darwin's theory to draw together a wide variety of issues in
taxonomy, comparative anatomy, paleontology, biogeography, and
embryology under the simple principles worked out in the first four
chapters (chps. 11-13). In important respects, this
"consilience" argument might be seen as best reflecting
the impact of William Whewell's methodology (see above),
although Whewell is not cited in any of the editions.



The explanatory methodology of Darwin's theory also provided him
with a means of defeating certain major objections, such as those
drawn from the existence of organs of great complication and function.
To deal with the question of the vertebrate eye in chapter six, for
example, Darwin offered a few speculations on how such a structure
could have developed by the gradual selection upon the rudimentary
eyes of invertebrates. But the primary solution offered was the
ability of his theory to draw together in its total argument numerous
lines of inquiry that would not otherwise receive a coherent
explanation. In such a case one would 



> 
> 
> admit that a structure even as perfect as the eye of an eagle might be
> formed by natural selection, although in this case he does not know
> any of the transitional grades. (*Origin* 1859: 188) 
> 
> 
> 



Here again, one might see Whewell's notion of a
"consilience of inductions" at work.



As Darwin envisioned it, with the acceptance of his theory, "a
grand untrodden field of inquiry will be opened"
(*Origin* 1859: 486) in biology and natural history. The
long-standing issues of species origins, if not the ultimate origins
of life, as well as the causes of their extinction, had been brought
within the domain of naturalistic explanation. It is in this context
that he makes the sole reference in the text to the claim that
"light will be thrown on the origin of man and his
history" (*Origin* 1859: 488).


## 3. The Reception of the *Origin*


### 3.1 The Popular Reception of Darwin's Theory



The broad sweep of Darwin's claims, the brevity of the empirical
evidence actually supplied in the text, and the implications of his
theory for several more general philosophical and theological issues,
immediately opened up a controversy over Darwinian evolution that has
waxed and waned over more than 150 years. As is well-known, Darwin
developed his argument rhetorically with the claims of its explanatory
superiority over the doctrine of "special creation", which
he posed as the main alternative to his account. This stylized
opposition to "creationism", rather than to the arguments
raised by the traditions of Cuvier, Buffon, and Lyell that
demonstratively formed the basis of the scientific opposition to
transformism before Darwin (see the entry on
 evolutionary thought before Darwin),
 was a point of considerable criticism by contemporaries such as
Richard Owen, who held no such theory of special creationism (Bowler
2013a). But the rhetorical strategy of opposing his theory to theistic
creationism served to define much of the popular debate over
Darwin's theory in the succeeding period, and continues to
define it in the present.



On the level of popular culture, Darwin's theory fell into a
complex social situation that took on different features in different
national traditions. In the anglophone world, the great popularity of
the anonymous *Vestiges of the Natural History of Creation* of
1844, which had reached 11 editions and sold 23,350 copies by December
of 1860 (Secord "Introduction" to Chambers 1844 reprint
[1994: xxvii]), with several more editions to appear by the end of the
century, certainly prepared the groundwork for the general notion of
the evolutionary origins of species by natural law. The
*Vestiges*'s grand schema of a teleological development
of life from the earliest beginnings of the solar system in a gaseous
nebula to the emergence of humanity under the action of a great
"law of development", had also been popularized for
Victorian readers by Alfred Lord Tennyson's epic poem *In
Memoriam* (1850). This provided a context in which some could read
Darwin as supplying additional support for the belief in an optimistic
historical development of life under teleological guidance with the
promise of ultimate historical redemption. Such readings also rendered
the *Origin* seemingly compatible with the progressive
evolutionism of Herbert Spencer (1820-1903; see the entry on
 Herbert Spencer).
 Spencer's writings have been shown to be an important vehicle
by which Darwin's views, modified to fit the progressivist views
expounded by Spencer, were first introduced in non-Western contexts
(Jin 2019a,b; Yang 2013; Lightman [ed.] 2015; Pusey 1983; Elshakry
2013) Most of this popular reception ignored or revised Darwin's
concept of evolution by natural selection to fit these progressivist
alternatives (Bowler 1983). The popular image often depicted of a
great public outcry against Darwin's work has been shown by
careful historical analysis to be generally mythical, or at least in
need of careful discrimination by social group, national tradition,
and religious affiliation (Bowler 2013a; Ellegard 1958).



Analysis of the various European receptions of Darwin's work
currently forms a scholarly industry in its own right (Bowler 2013a;
Gayon 2013; Glick 1974 [1988], 2013; Glick & Shaffer 2014; Engels
& Glick 2008; Gliboff 2008; Numbers 1998; Pancaldi, 1983 [1991];
Todes 1989; Kelly 1981; Hull 1973). Studies of non-Western receptions
is a newer area in Darwin studies. These display similar patterns, but
also important differences, from the reception in European contexts
(Jin 2019a,b; Yang 2013; Shen 2016; Elshakry 2013; Glick 1988
"Preface"; Pusey 1983). These studies continue to display
a common pattern in which the general reception of Darwin's
theories was conditioned, if not determined, by the pre-existing
intellectual, scientific, social, and political contexts into which
Darwin's theories were inserted.



Three examples--France, Germany, and China--can be
elaborated upon. In France, Darwin's theory was received against
the background of the prior debates over transformism of the 1830s
that pitted the theories of Lamarck and Etienne Geoffroy St. Hilaire
against Cuvier (Gayon 2013; entry on
 evolutionary thought before Darwin,
 4.1). At least within official Parisian science, these debates had
been resolved in favor of Cuvier's anti-transformism. Darwin
was, as a consequence, viewed as endorsing rejected science by leading
figures of French science. As the leading physiologist and
methodologist of French Science, Claude Bernard (1813-78) put
this in 1865, Darwin's theory was to be regarded with those of
"a Goethe, an Oken, a Carus, a Geoffroy Saint Hilaire",
locating it within speculative philosophy of nature rather than
granting it the status of "positive" science (Bernard
1865: 158-159 [1957: 91-92]). The intellectual framework
provided by the "positive philosophy" of Auguste Comte
(1798-1857) also worked both for and against Darwin. On one
hand, Comte's emphasis on the historical progress of science
over superstition and metaphysics allowed Darwin to be summoned in
support of a theory of the progress of science. The *Origin*
was so interpreted in the preface to the first French translation of
the *Origin* made by Clemence Royer (Harvey 2008). On
the other hand, the Comtean three stages view of history, with its
claim about the historical transcendence of speculative and
metaphysical periods of science by a final period of experimental
science governed by determinate laws, placed Darwinism in a
metaphysical phase of speculative nature philosophy, as captured in
the above quotation from Claude Bernard.



In the Germanies, Darwin's work entered a complex social,
intellectual and political situation in the wake of the failed efforts
to establish liberal democracy in 1848. It also entered an
intellectual culture strongly influenced by the pre-existent
philosophical traditions of Kant, of Schelling's
*Naturphilosophie*, German Romanticism, and the Idealism of
Fichte and Hegel (R.J. Richards 2002, 2008, 2013; Gliboff 2008, 2007;
Mullen 1964). These factors formed a complex political and
philosophical environment into which Darwin's developmental view
of nature and theory of the transformation of species was quickly
assimilated, if also altered. Many readings of Darwin consequently
interpreted his arguments against a background of Schelling's
philosophy of nature. Darwin's role in debates over scientific
materialism were also brought to the fore by the enthusiastic advocacy
of Darwinism in Germany by University of Jena professor of zoology
Ernst Heinrich Haeckel (1834-1919). More than any other
individual, Haeckel made *Darwinismus* a major player in the
polarized political and religious disputes of Bismarckian Germany
(R.J. Richards 2008). Through his polemical writings, such as the
*Natural History of Creation* (1868), *Anthropogeny*
(1874), and *Riddle of the Universe* (1895-99), Haeckel
advocated a materialist monism in the name of Darwin, and used this as
a stick with which to beat traditional religion. Much of the
historical conflict between religious communities and evolutionary
biology can be traced back to Haeckel's polemical writings,
which went through numerous editions and translations, including
several English and American editions that appeared into the early
decades of the twentieth century.



To turn to a very different context, that of China, Darwin's
works entered Chinese discussions by a curious route. The initial
discussions of Darwinian theory were generated by the translation of
Thomas Henry Huxley's 1893 Romanes Lecture "Evolution and
Ethics" by
the naval science scholar Yan Fu (1854-1921) who had encountered Darwinism while being educated at the Royal Naval College in Greenwich from 1877 to 1899. This translation was accompanied by Huxley's
"Prolegomena", and was accompanied with an extensive
commentary by Yan Fu drawing heavily upon the writings of Herbert
Spencer. This translation, published under the name of *Tianyan
Lun* in 1898, has been shown to have been the main vehicle by
which the Chinese learned of Darwin's work (Jin 2019a,b; Yang
2013; Pusey 1983). Beginning in 1902 with a partial translation by Ma
Junwu (1881-1940), a Chinese scientist, trained in chemistry and metallurgy in
Japan and Germany, the early chapters of the *Origin* itself
were made available to a Chinese audience. This initial translation of the first five chapters between 1902 and 1906 by
Ma Junwu modified the text to agree with the progressive evolutionism
of Spencer and with Yan Fu's popular *Tianyan Lun.* Only
in September of 1920 did the Chinese have Ma Junwu's full
translation of Darwin's sixth edition. This gave a more faithful
rendering of Darwin's text, including an accurate translation of
Darwin's final views on natural selection (Jin 2019a,b). As a
political reformer and close associate of democratic reformer Sun
Yat-Sen (1866-1925), Junwu's concern with Darwin also was
involved in revolutionary Chinese politics (Jin 2019a).


### 3.2 The Professional Reception of Darwin's Theory



One cannot always distinguish between "popular" and
"professional" receptions of Darwin. The simplest solution
is to confine the latter designation to those who embraced
Darwin's version of a general theory of descent with
modification by people with professional research and teaching
positions in universities and scientific societies, those who were
intimately familiar with the empirical evidence and the technical
scientific issues under debate in the 1860s in geology, comparative
anatomy, embryology, biogeography, and classification theory. This
group can usually be distinguished from lay interpreters who may not
have made distinctions between the views of Lamarck, Chambers,
Schelling, Spencer, and Darwin on the historical development of life.
But this only gives a crude instrument of analysis.



The case of Ernst Haeckel displays this imprecision. He was a leading
professor of zoology at an important German university (Jena), and he
formed a generation of scientific workers in embryology and natural
history who had major impact on the history of the life sciences. From
his position, Haeckel was able to develop Darwinism both as a popular
movement with social and political extensions, and also as a
scientific research program that pursued the study of morphology and
comparative embryology in the light of Darwin's general theory
(R.J. Richards 1992: chp. 6, 2008, 2013; Nyhart 1995).



If we concentrate on the reception by workers holding professional
positions in museums, laboratories, and research and teaching
positions in universities and membership in elite scientific
societies, Darwin's reception was varied (Bowler 1996; Hull
1973). Many prominent members of Darwin's immediate intellectual
circle--Adam Sedgwick, William Whewell, Charles Lyell, Richard
Owen, and Thomas Huxley--had previously been highly critical of
Chambers's *Vestiges* in the 1840s for its speculative
character and its scientific incompetence (Secord 2000). Darwin
himself feared a similar reception, and he recognized the substantial
challenge facing him in convincing this group and the larger community
of scientific specialists with which he interacted and corresponded
widely. With this group he was only partially successful.



Historical studies have revealed that only rarely did members of the
scientific elites accept and develop Darwin's theories exactly
as they were presented in his texts. Statistical studies on the
reception by the scientific community in England in the first decade
after the publication of the *Origin* have shown a complicated
picture in which there was neither wide-spread conversion of the
scientific community to Darwin's views, nor a clear generational
stratification between younger converts and older resisters, counter
to Darwin's own predictions in the final chapter of the
*Origin* (Hull et al. 1978). These studies also reveal a
distinct willingness within the scientific community to separate
acceptance of Darwin's more general claim of species descent
with modification from common ancestors from the endorsement of his
explanation of this descent through the action of natural selection
(Bowler 1983, 2013a). To utilize the categories of a Lakatosian
"research program" analysis of scientific theories in
their historical extension, one can distinguish between a "hard
core" of defining central assumptions, a "protective
belt" of auxiliary hypotheses that protect this central core
from refutations, and a "positive heuristic" of applied
research applications that are subject to continued revision and even
refutation (Lakatos 1970). With these distinctions in mind, it is
difficult to claim that anything more than the belief in descent from
common ancestry was maintained by a broadly international scientific
community at the "hard core" level in the period between
1870-1930. This meant that the historical impact of
Darwin's theories on the professional scientific community must
consider the important deviations from his own formulations (Bowler
1983, 2003).



Of central importance in analyzing this complex professional reception
was the role assigned to normal individual variation and its causes.
In the initial public presentation of his theory, Darwin had relied on
the novel claim that small individual variations--the kind of
differences considered by an earlier tradition as merely
"accidental"--formed the raw material upon which, by
unlimited addition through the action of natural selection, major
changes could be produced sufficient to explain the origin and
subsequent differences in all the various forms of life over time.
Darwin, however, left the specific causes of this variation unspecified beyond some effect of the environment on the sexual organs.
Variation was presented in the *Origin* with the statement that
"the laws governing inheritance are quite unknown" (Darwin
1859: 13). In keeping with his commitment to the
gradualism of Lyellian geology, Darwin also rejected the role of major
"sports" or other sources of discontinuous change in this
process.



As critics focused their attacks on the claim that such
micro-differences between individuals could be accumulated over time
without natural limits, Darwin began a series of modifications and
revisions of the theory through a back and forth dialogue with his
critics that can be followed by revisions to the text of the
*Origin*. In the fourth edition of 1866, for example, Darwin
inserted the claim that the continuous gradualism illustrated by his
branching diagram was misleading, and that transformative change does
not necessarily go on continuously. "It is far more probable
that each form remains for long periods unaltered, and then again
undergoes modification" (*Origin* 1866: 132 [Peckham 1959
[2006: 213]). This change-stasis-change model presumably allowed
variation to stabilize for a period of time around a mean value from
which additional change could then resume. Such a model would,
however, presumably require even more time for its working than the
multi-millions of years assumed in the original presentation of the
theory.



The difficulties in Darwin's arguments that had emerged by 1866
were highlighted in a lengthy and telling critique in 1867 by the
Scottish engineer Henry Fleeming Jenkin (1833-85) (typically
Fleeming Jenkin). Using an argument previously raised in the 1830s by
Charles Lyell against Lamarck, Fleeming Jenkin cited empirical
evidence from domestic breeding that suggested a distinct limitation
on the degree of variation, and denied that selection upon this could
be taken to the extent assumed by Darwin (Fleeming Jenkin 1867; Hoquet
2013). Using a loosely mathematical argument, Fleeming Jenkin argued
that the effects of intercrossing would continuously swamp deviations
from the mean values of characters and result in a tendency of the
variation in a population to return to mean values over time. For
Fleeming Jenkin, Darwin's reliance on continuous additive
deviation was presumed to be undermined by this argument, and only
more dramatic and discontinuous change--something Darwin
explicitly rejected--could account for the origin of new
species.



Fleeming Jenkin also argued that the time needed by Darwin's
theory was simply inadequate, supporting this claim by an appeal to
the physical calculations of the probable age of the earth presented
in publications by Fleeming Jenkin's mentor, the Glasgow
physicist William Thompson (Lord Kelvin, 1824-1907; Burchfield,
1975). On the basis of Thompson's quantitative physical
arguments, Fleeming Jenkin judged the time since the origin of the
solar system to be insufficient for the Darwinian gradualist theory of
species transformation to take place. Jenkin's multi-pronged
argument gave Darwin considerable difficulties and set the stage for
more detailed empirical inquiries into variation and its causes. The
time difficulties were only resolved in the twentieth-century with the
discovery of radioactivity.



As a solution to the variation question, Darwin developed his
"provisional hypothesis" of pangenesis, which he presented
the year after the appearance of the Fleeming Jenkin review in his
two-volume *Variation of Plants and Animals Under
Domestication* (1868, second edition 1875; Olby 2013). Although
this theory had been formulated independently of the Jenkin review
(Olby 1963), in effect it functioned as his reply to it. This offered
a causal theory of variation and inheritance through a return to a
theory resembling Buffon's theory of the organic molecules of
the previous century (see entry on
 evolutionary thought before Darwin
 section 3.2). Invisible material "gemmules" were presumed
to exist within the cells, and according to theory, these were subject
to possible external alteration by environment and circumstance. The
gemmules were then shed continually into the blood stream (the
"transport" hypothesis) and assembled by "mutual affinity for each other, leading to their aggregation into buds or into the sexual elements"
(*Variation* 1875: vol. 2: 370). In this form they were then
transmitted--the details were not explained--by sexual
generation to the next generation to form the new organism out of
"units of which each individual is composed" (ibid.). In
Darwin's view, this hypothesis united together numerous issues
into a coherent and causal theory of inheritance and explained the
basis of variation. It also explained how use-disuse inheritance, a
theory which Darwin never abandoned, could work.



The pangenesis theory, although not specifically referred to, seems to
be behind an important distinction he inserted into the fifth edition
of the *Origin* of 1869 where he made a direct reply to the
criticisms of Jenkin. In this textual revision, Darwin distinguished
"certain variations, which no one would
rank as mere individual differences", from ordinary variations
(*Origin* 1869: 105) [Peckham 1959
[2006: 178-179]]). This revision shifted Darwin's emphasis
away from his early reliance on normal slight individual variation,
and gave new status to what he termed by the sixth edition of 1872 "strongly
marked" variations. The latter were now the form of variation to
be given primary evolutionary significance, and presumably this was
more likely to be transmitted to the offspring, although details are
left unclear. In this form it presumably could be maintained in a
population against the tendency to swamping by intercrossing.
Darwin's struggles over this issue defined a set of problems
that British life scientists in particular were to deal with into the
1930s. The debates over variation placed Darwinism in a defensive
posture that forced its supporters into major revisions in the
Darwinian research program (Gayon 1998; Vorzimmer 1970). The long
period between 1870 and 1930, sometimes characterized as the
"Eclipse" of Darwinism, or at least of his natural
selection theory, was the outcome of these debates (Bowler 1983,
2013a).


## 4. Human Evolution and the *Descent of Man*


### 4.1 The Genesis of Darwin's *Descent*



Darwin had retained his own conclusions on human evolution quietly in
the background while the defense of his general theory was conducted
by advocates as diverse as Thomas Henry Huxley (1825-95) in
England, Asa Gray (1810-88) in the United States, and Ernst
Haeckel (1834-1919) in Germany. Darwin's own position on
the "human question" remained unclear, and his rhetorical
situating of the *Origin* within a tradition of divine creation
by secondary law, captured in the frontispiece quotations from William
Whewell and Francis Bacon, retained in all editions, in some degree
allowed many before 1871 to see Darwin as more open to religious views
than those of some of his popularizers.



It was in February of 1867 that Darwin decided to remove material from
his massive manuscript of the *Variation of Plants and Animals
Under Domestication* and create a "very small volume,
'an essay on the origin of mankind'" (Darwin to
Hooker, 8 February 1867 and CD to Turner, 11 February 1867, Burkhardt
et al. 2006 15: 74, 80). At this time he also sent to several
correspondents a questionnaire asking for information on human
emotional expression. This expanded into a major enterprise in which
he became deeply engaged with the issue of the implications of his
theory for ethics, writing to Asa Gray that "the difficulties of
the Moral sense has [sic] caused me much labor" (CD to Gray, 15 March
1870, Burkhardt et al. 2010 18: 68). This was expanded into a two volume
work by the time it was sent to the printer in June of 1870. By this
date he had also pulled out a separate section from the
*Variation* manuscript that was to become the *Expression of
the Emotions in Man and the Animals*,published in 1872.


### 4.2. Reception of the *Descent*



The dual publication of the *Descent of Man, and Selection in
Relation to Sex* (1871) and the *Expression of the
Emotions* (1872) created a watershed in the public reception of
Darwin's views (Radick 2013). Although Darwin had first worked
out many of his views on human evolution in the early "M"
and "N" Notebooks of 1838-40, public knowledge of
Darwin's own conclusions on human evolution rested on the one
vague sentence on the issue in the *Origin* itself. The
*Descent*, however, made public his more radical conclusions,
and seemed to many of his readers, even those previously sympathetic
to the *Origin*, to throw Darwin's weight behind
materialist and anti-religious forces spearheaded by such individuals
as German physiologist Friederich Ludwig Buchner
(1824-1899), Dutch physiologist Jacob Moleschott
(1822-93), English socialist and Darwin popularizer Edward
Aveling (1849-98), and German zoologist Ernst Haeckel. Although
the question of human evolution had already been dealt with in part by
Thomas Huxley in the *Man's Place in Nature* of 1863, by
Charles Lyell in the same year in his *Geological Evidences of the
Antiquity of Man*, by Alfred Russel Wallace in articles in 1864
and 1870 (Wallace 1864, 1870 and online), and by Haeckel in
his *Naturliche Schopfungsgeschichte* of 1868, these
authors had either not dealt with the full range of questions
presented by the inclusion of human beings in the evolutionary process
(Huxley), or they had emphasized the moral and mental discontinuity
between humans and animals (Lyell, Wallace). Only Haeckel had drawn
out a more general reductive conception of humanity from evolutionary
theory and he had not ventured into the specific issues of ethics,
social organization, the origins of human races, and the relation of
human mental properties to those of animals, all of which are dealt
with in the *Descent*. Darwin's two-volume treatise
presented, as one commentator has put it, "a closer resemblance
to Darwin's early naturalistic vision than anything else he ever
published" (Durant 1985: 294).



Darwin's extension of his theory to a range of questions
traditionally discussed within philosophy, theology, and social and
political theory, hardened the opposition of many religiously-based
communities to evolutionary theory, although here again, distinctions
must be made between different communities (Ellegard 1958: chp.
14). Such opposition was not simply based upon the denial of the
literal scriptural account of the origins of humankind, an issue that
played out differently within the main religious communions (Haught
2013; Finnegan 2013; Swetlitz 2013; Artigas, Glick, & Martinez
2006; Moore 1979). The more fundamental opposition was due to the
denial of distinctions, other than those of degree, between
fundamental human properties and those of animals. Furthermore, the
apparent denial of some kind of divine guidance in the processes
behind human evolution and the non-teleological character of
Darwin's final formulations of the natural selection theory in
the fifth and sixth editions of the *Origin*, hardened this
opposition. His adoption from Herbert Spencer of designator
"survival of the fittest" as a synonym for "natural
selection" in the fifth edition added to this growing
opposition. As a consequence, the favorable readings that many
influential religious thinkers--John Henry Newman
(1801-1890) is a good example--had given to the original
*Origin*, disappeared. The rhetoric of the *Descent*,
with its conclusion that "man is descended from a hairy
quadruped, furnished with a tail and pointed ears" (1871: vol.
2: 389), presented to the public a different Darwin than many had
associated with the author of the *Journal of Researches* and
the early editions of the *Origin*.



Most striking in comparing the *Origin* to the *Descent*
was the strong emphasis on the workings of the secondary process of
sexual selection in the animal kingdom (E. Richards 2017;
R.A. Richards 2013). Sexual selection--the selection of females
by males or vice versa for breeding purposes--had given a general
statement of this principle in chapter four of the *Origin*,
but this played a minor role in the original argument, and its
importance was denied by contemporaries like A. R. Wallace. Darwin now
developed this secondary form of selection in extensive detail as a
factor in evolution that could even work against ordinary natural
selection. Sexual selection could now be marshaled to explain both
sexual dimorphism and also those character and properties of
organisms--elaborate feeding organs, bright colors on fish and
birds, and seemingly maladaptive structures such as the great horn on
the Rhinoceros beetle--, that might appear to be anomalous
outcomes of ordinary natural selection working to the optimal survival
of organisms in nature. In a dramatic extension of this principle to
human beings, the combination of natural and sexual selection is used
to explain the origins of the human beings from simian ancestors. It
also explains the sexual dimorphism displayed by human beings, and is
the main factor accounting for the origin of human races.


### 4.3 The Ethical Theory of the *Descent of Man*



The many dimensions of "social" Darwinism that were
affected by the *Descent* demand separate articles, as does the
separate impact of the *Expression of the Emotions*, a treatise
that in many respects is different in tone and content from the
*Descent.* It is also the case that many of the social
implications of evolutionary theory were due more to the influence of
Herbert Spencer than to Darwin's own writings, and for this
reason what has been termed "social Darwinism" may have
developed independently of Darwin (Bowler 2013b). In this closing
subsection the author will focus exclusively on one important aspect
of this broader social impact of the *Descent*, the Darwinian
treatment of ethics. This will be examined within its specific
Victorian context, rather than in light of more recent discussions of
altruism within contemporary sociobiology that may owe some filiation
with these Darwinian discussion (see entries on
 morality and evolutionary biology
 and
 biological altruism).



As can be seen from the letter to Asa Gray of March 1870 (Burkhardt et
al. 2010 18: 68) , Darwin was
particularly exercised by the issue of ethics in preparing the
*Descent*. His published treatment focused the long chapter
three of the *Descent* on the issue of the "moral
sense". In approaching ethics "exclusively from the side
of natural history" (*Descent* 1871: vol 1: 71), he
offered some innovations that do not easily map on to standard ethical
positions formulated around the familiar categories of Utilitarianism
and the Kantian heritage of Deontology. The closest connections might
be drawn with certain aspects of contemporary virtue ethics and some
aspects of Natural Law theory, although there are many specific
differences that prevent assimilation to these traditions as well
(Sloan 1999). His closest historical affinities are with the Scottish
moral sense tradition of Adam Smith, David Hume, and particularly as
this was developed in the writings of Darwin's distant relative,
Sir James Macintosh (1765-1832) (R.J. Richards
1987, 1999, 2003,
.



Traditional moral sense theory linked ethical behavior to an innate
property or instinct that was considered universal in human beings,
even though it required education and cultivation to reach its highest
expression (see
 moral sentimentalism
 in this encyclopedia). This inherent property, or "moral
sense", presumably explained such phenomena as ethical
conscience, and it also accounted for altruistic actions that could
not be reduced to a hedonic seeking of pleasure and avoiding pain. It
also did not involve the rational calculation of advantage by the
individual prior to action.



Darwin's reinterpretation of the moral sense tradition within
his evolutionary framework, however, implied important
transformations. The moral sense, for Darwin, was derived by
biological descent from animal instinct, and particularly from the
social instincts developed by natural selection. From this
perspective, Darwin could then argue for a genuine
"homology" of ethical foundations holding between humans
and animals, with the precursors of human ethical behavior found in
the behavior of other animals, particularly those with social
organization. Natural and sexual selection then shaped these ethical
instincts in ways that favored group survival rather than immediate
individual benefit (*Descent* 1871: vol. 1: 98). Human ethical
behavior is therefore grounded in a natural property, and ethical
action can occur without moral calculus or rational deliberation.
Because he considered ethical action to be grounded on a biologically
innate property, Darwin criticized John Stuart Mill's
Utilitarian theory because it relied on acquired habits rather than
something present in humans from the beginning (1871: vol. 1: 71n5).
The innate moral sense is his explanation for self-sacrifice and other
altruistic acts that cannot be attributed to individual self-survival
(1871: vol. 1: 86). Humans can be 



> 
> 
> impelled by the same instinctive motive, which made the heroic little
> American monkey...attack the great and dreaded baboon, to save
> his keeper. (*Descent* 1871: vol. 1: 87)
> 
> 
> 



When moral conflict occurs, this is generally attributed to a conflict
of instincts, with the stronger of two conflicting instincts favored
by natural selection insofar as it favors group benefit
(*Descent* 1871: vol. 1: 84). In human beings the "more
enduring Social Instincts" thus come to override the less
persistent "individual" instincts (1871: vol. 1: 87).



The adequacy of evolutionary ethical naturalism as a foundation for
ethical realism has been a point of contention for Darwin's
contemporaries and successors since the publication of the
*Descent*. For some moral philosophers, Darwin had simply
reduced ethics to a property subject to the relativizing tendencies of
natural selection (Farber 1994: chp. 5). It was, in the view of
Darwin's philosophical critics, to reduce ethics to biology and
in doing so, to offer no way to distinguish ethical goods from
survival advantages. Not even for some strong supporters of Darwinism,
such as Thomas Huxley and Alfred Russel Wallace, was Darwin's
account adequate (Farber 1994: chp. 4). Much of subsequent moral
philosophy was to be grounded upon the canonical acceptance of the
"is-ought" distinction, which developed from this critique of
"evolutionary" ethical theory. Receiving its most
influential expression in G. E. Moore 's (1873-1958)
*Principia Ethica* (1903)--itself an attack on
Spencer's version of evolutionary ethics--, the debate over
the adequacy of evolutionary ethics has continued (Hauser 2006; Katz
(ed.) 2000; Maienschein & Ruse (eds.) 1999).


## 5. Summary and Conclusion



The historiography adopted in this article rejects a simple linear
story of the development of Darwinian theory as a history of
increasingly true theories leading to a present consensus. Instead it
favors a more complicated "competing research programs"
analysis (Lakatos 1970), programs which through historical competition
have resulted in more adequate accounts of the relation of living
beings to historical time and naturalistic processes, but which show
repeated historical competition with one another .



More general philosophical issues associated with evolutionary
theory--those surrounding natural teleology, ethics, the relation
of evolutionary naturalism to the claims of religious traditions, the
implications for the relation of human beings to the rest of the
organic world--continue as issues of scholarly inquiry. If
contemporary neo-selectionist evolutionary theory displays continuity
with select features of the theories of Darwin, alternative
interpretations, such as the current movement known as evolutionary
developmental theory or "evo-devo", mark a return to
presumably discarded traditions of the nineteenth and twentieth
century that considered it essential to link evolution with embryonic
development and with the effects of external conditions on inheritance
(Gilbert 2015; Newman 2015; Laubichler & Maienschein 2013, [eds]
2007; Gissis & Jablonka [eds] 2011; Pigliucci & Muller
[eds] 2010; Amundson 2005; Gilbert, Opitz, & Raff 1996). Such
developments suggest that there are still substantial theoretical
issues at stake that may alter the future understanding of
evolutionary theory in important ways (Sloan, McKenny, & Eggleson
[eds] 2015).