Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132

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Studies in History and Philosophy of Biological andBiomedical Sciences

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Making the case for orthogenesis: The popularization of definitelydirected evolution (1890–1926)

1369-8486/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.shpsc.2013.11.009

E-mail address: mark.ulett@duke.edu

Mark A. UlettDuke University, Box 90025, Durham, NC 27708, United States

a r t i c l e i n f o a b s t r a c t

Article history:Available online 22 December 2013

Keywords:Directed evolutionEdward Drinker CopeLeo BergScience popularizationOrthogenesisTheodor Eimer

Throughout the history of evolutionary theory a number of scientists have argued that evolution proceedsalong a limited number of definite trajectories, a concept and group of theories known as ‘‘orthogenesis’’.Beginning in the 1880s, influential evolutionists including Theodor Eimer, Edward Drinker Cope, and LeoBerg argued that a fully causal explanation of evolution must take into account the origin and nature ofvariation, an idea that implied orthogenesis in their views. This paper argues that these orthogenesisdeveloped theories that were more than highly technical and theoretically dubious hypotheses accessibleonly to elite specialists, as certain histories of these ideas might suggest. Some orthogenesists made theircase to a non-specialist audience to gain support for their ideas in the face of widespread controversy overevolutionary theory. Through a case study analysis of three major books by Eimer, Cope, and Berg, thispaper contends that they sought to re-orient the central tenets of the science of evolution to includethe causal impact of variation on evolutionary outcomes. These orthogenesists developed novel and syn-thetic evolutionary theories in a publishing platform suited for non-specialist audiences in an effort toimpact the debates over evolutionary causation prevalent in the late-19th and early 20th centuries.

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1. Introduction and context

The relationship between science and the public has changeddramatically throughout the past few centuries (Bensaude-Vincent, 2001). The complex relationship between the nature ofscience and science popularization often requires investigatorsto focus on a narrow set of scientific theories, practices, or nego-tiations within a limited timeframe or set of related ideas. Thegoal of this special section of papers is to explore the dynamicrelationship between evolutionary theory, popularization ofevolution, and changes internal to the study of evolution (see:Smocovitis, Shapiro, Perez, Sepkowski, this issue). To investigatethis relationship fully, we must understand how these factorschanged over time, drawing conclusions after scrutinizing partic-ular cases closely. This paper contributes to ongoing discussion ofscience popularization by probing the motivations and approachesfor making the seemingly obscure evolutionary theory of ortho-genesis (evolution in definite directions due to limitations on

variation) more widely known outside a specialist audiencebetween 1880 and 1930.

The years between 1880 and 1930 were a fascinating and com-plex period for evolutionary theorizing (Bowler, 1983), yet theinvolvement and impact of non-specialists in these debates re-mains under-explored. This was an era of rapid changes in how sci-entists understood the processes of heredity, development, andevolution. Biologists theorized and intensely debated the mecha-nisms, phenomena, and outcomes that ‘mattered’ for a comprehen-sive explanation of evolution (e.g. Delage & Goldsmith, 1913;Dennert, 1905; Kellogg, 1907). Changes in theories of developmenthad significant implications for theories of heredity and evolution.Reciprocally, changes in theories of heredity held large implica-tions for evolution and development. These ideas were in fluxand deeply interconnected. Concerning evolution, these changesin related theories had large implications for what Steven Jay Gou-ld has characterized as the ‘‘agency, efficacy, and scope’’ of a partic-ular evolutionary mechanism (2002): agency is the unit on which

M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132 125

the mechanism acts; efficacy is the power of the mechanism tooperate in nature; and scope is the extent to which that mecha-nism can explain the diversity and history of life on earth. In thedecades surrounding 1900, evolutionists debated and negotiatedthe explanatory power and evidential basis of various theories ofevolution.1

Focusing closely on how orthogenesists communicated theirideas to non-specialist audiences between 1880 and 1930 showsone perspective of the complex relationship between evolution-ary theory and public, non-specialist audiences. Emphasizingorthogenesis contributes to ongoing discussions in the history ofevolutionary theory and science popularization (e.g. Lightman,2007, 2010). This paper analyzes the major books of three prom-inent and well-respected evolutionists. The Swiss-German zoolo-gist Theodor Eimer wrote Organic Evolution in 1888 (Englishtrans., 1890) in response to the hereditary and evolutionary workof his teacher August Weismann. Building on a lifetime of writingabout evolutionary theory and patterns of evolution, the popularAmerican paleontologist Edward Drinker Cope wrote Primary Fac-tors of Organic Evolution (1896) as a synthetic treatise incorporat-ing his findings from years, and many dollars, spent hunting fornew fossil vertebrates. The Soviet biogeographer and taxonomistLeo Berg produced his treatise on definitely directed evolutiontitled Nomogenesis: or Evolution According to Law in 1922 (Englishtrans., 1926). These three books, written by these three theorists,provide excellent case studies of the motivation and approachesused by orthogenesists make their case to a non-specialistaudience.

The role of orthogenesis in the history of evolutionary theory issomewhat unclear. This is in part a consequence of the mischarac-terization of theories of orthogenesis by advocates of neo-Darwin-ism. For example, noted evolutionist Ernst Mayr wrote that ‘‘untilnatural selection was fully understood, many evolutionists, fromLamarck to H.F. Osborn to Teilhard de Chardin, postulated the exis-tence of a non-physical (perhaps even non-material) force whichdrove the living world upward towards ever-greater perfection(orthogenesis)’’ (Mayr, 1982). While aspects of this quotation rep-resent small portions of individual theories, many proponents oforthogenesis were, on the whole, materialists and mechanistsrather than cosmic teleologists or vitalists advocating non-physi-calist forces. Another opponent of orthogenesis, albeit more sym-pathetic than Mayr, Julian Huxley used ‘‘the eclipse ofDarwinism’’ metaphor to characterize these theories in this period.The historian Peter Bowler adopted this metaphor (Bowler, 1983;Huxley, 1942) that presumes Darwinism’s triumphant return andthe inevitable failure of alternatives like orthogenesis (Largent,2009). Beyond mischaracterizations and problematic metaphorsof orthogenesis, other histories present the theory as highly techni-cal and theoretically complex (Levit & Olsson, 2006). Indeed, scan-ning the literature of orthogenesis we find many foreign conceptsand complex Greek-based words that seem to support this notion:bathmysm, physiogenesis, kinetogenesis, aristogenesis, genepista-sis, halmatogenesis, and kyesamechania. In this period of evolu-tionary theory it was common to postulate laws of developmentand evolution, a theoretical construct used to characterize phe-nomena operating under constraints or in regular patterns. Theseterms and law-based thinking strike the twenty-first century read-er as a bizarre and problematic, potentially indicative of highlyspecialized and dubious theorizing. But these traditional descrip-tions of orthogenesis are not entirely correct.

1 There were numerous different theories of evolution under consideration at this time, inetc.

2 For the purposes of this paper the term ‘‘neo-Darwinism’’ is used consistently with hoWeismann, who considered natural selection to be capable of fully accounting for evolutioconsistently in Organic Evolution in reference to Weismann’s evolutionary theory based on

There was more going on among the proponents of orthogene-sis than jargonizing and dunder-headed theorizing only accessibleto the scientific elite. Focusing on three major books by Eimer,Cope, and Berg this essay shows that these authors intended theirbooks to be read by a wide, non-specialist audience. They eachstructured their books such that their theories answered generalquestions in evolution: Eimer argued that orthogenesis providesthe best explanation of evolutionary novelty; Cope maintained thathis theory of orthogenetic evolution could account for the full evo-lutionary history of the fantastic new fossils dug out of the Wes-tern territories in the United States in the late 1800s; and Bergpromoted an account of evolution as a highly structured andnon-random process.

The second argument in this paper posits that orthogenesistswent beyond crafting their books for a non-specialist audience;they developed novel and synthetic theories that placed the ori-gin and nature of variation as a central and indispensable causalcomponent of any comprehensive explanation of evolutionarycausation. Eimer, Cope, and Berg all contended that a theory ofevolution that excluded the impact of new variation on evolution-ary trajectories was incomplete. The brief analysis conducted inthe second half of this paper shows that the central motivationsfor writing their books was to re-orient the basic factors on whichevolutionary theory was grounded to focus on the role ofvariation.

These two theses, that orthogenesis was not only for specialistsand that it focused on the causal role of variation in evolution, pro-vides new perspectives on what orthogenesists were doing andhow they did it. Within the context of science popularization, thetheories in these non-specialist books were significant pieces ofnew theory; this was not simply a case of scientists translatingpure science into language comprehensible to lay-audiences. Assuch, this paper shows how orthogenesists were a part of a differ-ent approach to science popularization. Because they sought topopularize an alternative to the prevailing theory of neo-Darwin-ism,2 they endeavoured to influence the core tenets of evolutionarythinking in a period of intense theoretical upheaval. This approachshows that the boundaries between elite specialists and amateursas implied by traditional models of science popularization-as-trans-lation does not apply in this case.

2. Making the case for orthogenesis

The decades between 1880 and 1930 pose a challenge to histo-rians of evolutionary theory in part because there was no clearhegemony over the most significant mechanism of evolutionarycausation. One consequence of this turmoil is that the reasonswhy scientists would endeavor to make their work appealing tonon-specialist audiences are not immediately clear. Nevertheless,the debates over the mechanism of evolution saw specialists mak-ing their work accessible to wide, non-specialist audiences to gainsupport for their theory. Evolution was a theory of general interestin this time period, and investigators from across various academicdisciplines were interested in the outcomes of the debates overevolutionary causation. Focusing on evolution generally, andorthogenesis specifically, shows that these theories had not be-come so specialized that the central ideas were inaccessible tonon-specialists. This first section emphasizes how major propo-nents of orthogenesis presented their ideas for a non-specialistaudience.

cluding: neo-Darwinism, saltationism, orthogenesis, neo-Lamarckism, orthoselection,

w it was employed in the early 1890s. The term denoted the views of individuals likenary change (Bailey, 1894). Eimer’s translator, Joseph T. Cunningham used this termgerm-plasm heredity (Eimer, 1890).

126 M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132

2.1. Eimer’s case

Historians generally recognize Theodor Eimer as one of ortho-genesis’ strongest advocates (Bowler, 1977, 1983; Gould, 2002;Levit & Olsson, 2006). He was famous for his increasing disagree-ment with Darwin’s late twentieth century advocate Weismannover the possibility that acquired characters could be inherited.After several decades of studying variation and evolution in definitedirections in lizards and butterflies, Eimer published a major bookon the subject titled Organic Evolution: as the Result of the Inheritanceof Acquired Characters According to the Laws of Organic Growth in1888. The goal of this book was to bring various forms of evidenceto bear on the problem of directed evolution. Eimer designed this tobe the first in a series of books to prove evolution in definite direc-tions. The British marine biologist and neo-Lamarckian Joseph T.Cunningham translated Eimer’s book into English because hethought that the Anglophone scientific community was acceptingWeismann’s perspectives on variation, heredity, and evolutionwithout due consideration of other perspectives (Cunningham,1890). Both Eimer and Cunningham thought that orthogenesiswas worthy of communicating to a broad, non-specialist audience.

Eimer used two noteworthy strategies to make his work appeal-ing to non-specialists. First, he argued in the preface to OrganicEvolution that his scholarly articles and scientific theories had notreceived adequate consideration by his peers.

‘‘But it seemed that very few investigators in the province of thedoctrine of evolution troubled themselves about the wall-lizard,or about facts obtained from such a common animal, or aboutthe conclusions to be drawn from them. It is possible, indeed,that the title of my papers was not very inviting. I ought to haveput Darwinism first, and the wall-lizards second’’ (Eimer, 1890,p. 5).3

Eimer felt ignored, a sentiment that he employed in subsequentpublications (Eimer, 1898). This made Eimer sympathetic in hisreaders’ eyes, positioning him as the underdog and challenger toDarwin’s champion Weismann. It set up his adversarial tone inrefuting Weismann’s argument that natural selection was sufficientto explain all evolution (see: Churchill, 1968, 1999; Winther, 2001).This strategy shows that Eimer intended to capture the interest ofnon-specialist readers because proclaiming that your work has beenignored by specialists is not a particularly effective approach whenpublishing for those specialists. He intended to capture the interestof a wide audience with the impact of his as-yet ignored theory.

The second approach Eimer used was to focus his book on thegeneral explanatory strengths of orthogenesis and the weaknessesof natural selection through the topic of the origin of novel charac-teristics. He was not quibbling over small details or academicminutiae but focusing on the ‘big picture’ of evolution. Eimer knewthat evolutionary theories emphasizing natural selection could noteasily account for incipient features and the evolution of underde-veloped characters, a problem that Darwin noted in his On the Ori-gin of Species (1859) and many others had subsequentlycommented on (Mivart, 1871; Müller & Wagner, 1991). Eimer ar-gued that new characters would develop if the physical or chemi-cal environment changed an organism’s development or growthprocess (1890, p. 25). The chemical, physical, morphological, andphysiological features of an organism would constrain and forcenovel features to take place in specific directions. This was not aside argument in Organic Evolution; the origin of novel characteris-tics accounts for 40% of the entire volume. He gave an account ofsome of the major novelties in the history of life, including: unicel-

3 The title of this paper translates to ‘‘Researches on the variation of the Wall-Lizard:Darwinism’’ (1874). Indeed he should have put ‘‘Darwinism’’ first!

lular organisms, multicellularity, muscles, striated muscles, sensecells, the nervous system, and voice and speech. The topic on whichEimer devoted the most effort was the origin of human mental fac-ulties, which was of general interest to non-specialists at the timesince it had a direct impact on the view of human origins. Conse-quently, Eimer’s two major argumentative strategies, making himthe sympathetic underdog and playing to orthogenesis’ strengths,indicate that he attempted to make his work to be accessible tonon-specialists.

2.2. Cope’s case

Another major figure in the history of orthogenetic theory wasEdward Drinker Cope. He came from a wealthy family of Pennsyl-vania Quakers, which afforded him the luxury of spending a gooddeal of money to dig up dinosaur bones in the territories in theAmerican West in the 1870s and 1880s (Davidson, 1997; Osborn,1931). Not only was he the leader of some of these expeditions,he often paid to have numerous groups in the field sending himnew fossils. But even before he started digging up bones in theWest, Cope had developed a theory of orthogenesis based on whathe called the ‘‘law of acceleration and retardation’’ in two early pa-pers published in 1868 and 1871. These papers provided him withthe theoretical framework to further develop his phylogenies andevolutionary concepts.

In 1878 Cope purchased the American Naturalist, which gavehim extensive editorial and managerial control over the contentsof this publication. At this time, however, American Naturalistwas not the technical scientific journal that we read today.Throughout its first forty years American Naturalist was a monthlymagazine of Natural History (Dexter, 1956). It was designed andpublished with the express intent of combining science and popu-lar interests. It included many images and was ‘‘addressed to alllovers of nature’’ (Conklin, 1944, p. 32). American Naturalist dis-cussed reports on expeditions, museums, movements, publica-tions, deaths, and natural history benefactors. Cope used hiseditorial position to his advantage; according to Henry Fairfield Os-born, Cope published no fewer than 776 articles in this magazine(1930). His latest fossil finds were often the subjects of his articles.

Cope’s fossils became the primary evidence in his 1896 bookPrimary Factors of Organic Evolution, wherein he sought to weaveAmerican paleontology into a coherent account of evolution basedlargely on his work published earlier in American Naturalist. Know-ing that readers would be familiar with this work, he repurposedmuch of this non-specialist material in his book. Primary Factorsbegins by taking readers through the history of vertebrate evolu-tion showing how fossils from the American West reveal that evo-lution takes place in definite directions. Non-specialists wouldhave been familiar with some of these fossils, and Cope’s accountof their origin places the fossils observed in the halls of the Amer-ican Museum of Natural History and other museums in orthoge-netic trajectories. For those among his audience unfamiliar withthe particulars features of the fossils, the more general audience,Cope provided them with over a hundred images in Primary Factorsto help them visualize the organisms.

Cope employed a second strategy to make his work generallyaccessible to non-specialists: he related his theory to the causalentities and relationships in basic physics. Cope devised an ‘‘energytheory of evolution’’ in the early 1890s. Building off his preliminaryhypothesis in a 1871 paper, he relied on a series of easily accessiblearguments that showed the similarity between the energies of evo-lution and energies in physics (see: Cope, 1894). He described the

a Contribution to the Theory of Evolution From Constitutional causes, and also to

M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132 127

physical shapes of organisms as the consequence of direct interac-tion between the organism and the environment in an attempt tophysicalize his theory.

He used examples, as can be seen in Fig. 1, to make his energytheory comprehensible in simple terms by relating it to basic phys-ics and common experience. Fig. 1 shows a bent arm in a coat; thephysical bending of the arm produces a folding pattern as a re-sponse. Much as the movement of the arm shapes the coat, Copeargued that the physical forces of the organism’s movement shapethe vertebral column. You can see how he argued that the foldingpattern of the coat is mirrored in the vertebral column. Cope usedthis argument from analogy to show that relatively simple physicscan explain the structure of the vertebrae. Anyone with a coatcould relate.

2.3. Berg’s case

The prominent taxonomist and biogeographer Leo Berg was ahighly regarded naturalist and prolific thinker who wrote exten-sively on ichthyology, geography, ethnography, taxonomy, andevolution. His major contribution to evolutionary theory camefrom his book Nomogenesis: or Evolution According to Law first pub-lished in 1922 in Russian and translated in 1926 into English. Bergused a large array of facts from a variety of disciplines in Nomogen-esis. He argued at the outset that the purpose of the book was ‘‘toshow that the evolution of organisms is the result of certain pro-cesses inherent in them, which are based on law’’ (Berg,1969[1926], p. xvi). By ‘‘law’’ he meant a deep structure inherentin organic matter. He viewed the constraints placed on variationby the developmental process to be one of the most significantand controlling factors in the biological world.

For the purposes of this paper, one of Berg’s many argumentsdisplayed how his general idea was presented in a manner acces-sible to non-specialists. While he made a lot of arguments aboutthe philosophy and biology of chance, he presented one set ofimages originating from the British polymath D’Arcy WentworthThompson’s book On Growth and Form (1917). They were remark-ably effective in portraying Berg’s ideas. Drawings of the basic fea-tures of an organism sit on top of a Cartesian coordinate grid to

Fig. 1. Cope’s illustration of the physical cause of the structural pattern in the vertebral

present its features against a background space. As did Thompson,Berg visually modified the background space of one image in orderto morph one fish into another (Fig. 2).

This first drawing shows a parrot fish (genus Scarus) common inthe tropics. This long fish with prominent dentition can be visuallytransformed into the form of a marine angelfish (genus Pomacan-thus) by manipulating the coordinate system. If the perpendiculargrid is morphed into an oval, then the conceptual morphology ofone fish genus can be transformed into another. Similarly, Bergtransformed a porcupine fish (Diodon) into the spectacularly differ-ent oceanic sunfish (Molidae). Berg used the same form of argu-ment to show the morphological relationship between the skullof man and the skull of the chimpanzee (Berg, 1969[1926], pp.112–113).

In these images, Berg revealed one important strategy em-ployed to communicate his basic idea to a non-specialist audience.He made an explicit argument for the connection between organ-ismal transformations and mathematical transformations. He usedthe geometrical coordinates to show that organismal variation isrestricted in the same way that geometrical relationships are con-strained. Given certain parameters, variations can only proceed indefinite directions. Berg used these images in his argument toclearly and succinctly show that the biological world is highly or-dered and deeply structured.

2.4. Reception and popularization of orthogenesis

So far this paper has presented evidence that Eimer, Cope, andBerg all intended their work to be accessible by a non-specialistaudience. The obvious question to follow this conclusion is: werethey received this way? Several authors reviewed these books ina variety of different scientific and popular outlets, including: sci-entific journals, literary and general-interest periodicals, maga-zines, and newspapers. Taken together, these three books werereviewed in the following scientific, semi-popular, and popularplaces: Nature, Science, The Psychological Review, The PhilosophicalReview, The Academy, The Monist, The Speaker: The Liberal Review,The Edinburgh Review, The Cambridge Review, American Naturalist,Popular Science Monthly, The Manchester Guardian, and The New

column and the analogous pleating pattern exhibited by bending an arm in a coat.

Fig. 2. Berg’s use of D’Arcy Thompson’s fish morphs in Nomogenesis. The Scarus (2a) can be visually transformed into a Pomacanthus (2b), and a Diodon (2c) into a Mola (2d),when the geometrical planes are manipulated.

128 M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132

York Times. The wide readership of these book reviews alonestrongly suggests that many people interpreted these books as rel-evant for non-specialists. Whether the book was loved or loathed,it was almost always deemed appropriate reading material for any-one interested in evolution.

Frequently reviewers of these orthogenetic books interpretedthem directly into the framework of debates over neo-Darwinismand other mechanisms of evolution (Allen, 1890; Anonymous,1890a, 1890b, 1890c, 1890d, 1890e; Cope 1890). One review of Ei-mer’s book in the widely read Cambridge Review took issue with Ei-mer’s neo-Lamarckism and orthogenesis, suggested that readers ofEimer’s book peruse the many fine biological cases in the book butignore the theory (Anonymous, 1890c). Another response in theEdinburgh Review was interesting in that the author appeared tobe scoring the Eimer/Weismann battle like a boxing match. ‘‘Thecontroversy between the professors of Tübingen and Freiburg isto us a very interesting one. So far Professor Eimer appears, inour judgment, to have, on the whole, the best of the dispute. Buteffective as he is in his attack upon professor Weismann’s doc-trines, he exhibits marvelously little capability in defense’’ (Win-dle, 1890). While not necessarily advocating Eimer’s theories, his

reviewers nevertheless show that his book was of interest and rel-evant for non-specialists interested in evolutionary topics.

Perhaps unsurprisingly, Cope’s book received rave reviews inAmerican Naturalist. The review praises the author on his excellentillustrations, straightforward organization, and the publishers onmaking it conveniently sized for the busy traveler (Anonymous,1896, pp. 566–568). H. S. Williams (1896) gave Primary Factors aserious and lengthy consideration in the journal Science. He wrote:‘‘Most, if not all of the particular views of the author found in thisbook have been more or less fully elaborated in previous papers;but in their connected systematic form, combine with the viewsof other workers to constitute a consistent doctrine of evolution,we have in ‘‘Primary Factors’’ a valuable text-book for teachersand students’’ (Williams, 1896, p. 459). Other reviews display sim-ilar convictions (Cattell, 1896; Schiller, 1896; Tyler, 1897).

Berg’s Nomogenesis also received mixed reviews, but commen-tators also noted its value for non-specialists. In writing the for-ward for a later English translation of this book, Dobzhanskygave Berg’s efforts in Nomogenesis high praise saying that ‘‘Bergwas one of the outstanding intellects among Russian scientists.The breadth of his interests and the depth as well as amplitude

Fig. 3. The use of the term ‘‘orthogenesis’’ from 1883–1950 journals according topercentage.

M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132 129

of his scholarship were remarkable’’ (Dobzhansky, 1937, p. xi). De-spite disagreeing with Berg’s theory, Dobzhansky argued that sheerscope of his empirical evidence was important for students of biol-ogy to learn.

So there is evidence that these orthogenesists wrote books fornon-specialists, and the reviews of these works indicate that theintended audience was liable to be interested in these theories.This leads to the question: to what extent were debates over ortho-genesis taking place in popular or general scientific journals, as op-posed to highly technical specialist publications? A search throughJSTOR and Nature from 1893 to 1950 returned 503 results on theterm ‘‘orthogenesis’’, displayed in Fig. 3.

The journal demographics are quite interesting as well. Half ofthe uses of the term come from Nature, Science, The ScientificMonthly, Quarterly Review of Biology and a variety of generalistphilosophical journals. A further eleven percent was from AmericanNaturalist, which became more technical in the middle of this per-iod, but nevertheless intended many papers for non-specialists(Conklin, 1944). Finally, forty percent came from more specializedscientific journals or were cases where orthogenesis was men-tioned once or very infrequently. This shows that a significant por-tion of the debate over orthogenesis occurred in journals intendedfor a non-specialist audience. This is clear evidence that this strat-egy of making their case to a wide audience was indicative of abroader phenomenon, not just these cases outlined in this paper.

3. Variation in orthogenetic theory

The first argument in this paper outlined how Eimer, Cope, andBerg crafted their ideas for non-specialists, yet the question re-mains: what was the central idea that these books were designedto communicate to this audience? Put a slightly different way,what were the driving motivations and central theoretical pur-poses of these texts? Retaining the focus on Organic Evolution, Pri-mary Factors, and Nomogenesis, the second argument in this paperoutlines the motivations for writing these books as well as a shortdescription of how the nature and cause of variation was central totheir theories of evolutionary causation. These theories were com-prehensive and synthetic sets of ideas that could account for mostor all phenomena of importance in evolution. As such, Eimer, Cope,and Berg tried to re-orient popular support of evolution around theimpact of variation on evolutionary causation and outcomes.

3.1. Variation in Eimer’s theory

Eimer’s introduction to Organic Evolution provided readerswith a clear and succinct picture of the motivation for writing

this book. Eimer wrote: ‘‘It seemed to me long ago of the great-est importance to undertake an investigation of the questionwhether the modification (variation) of the species is governedby definite laws’’ (1890, p. 1). This quotation introduces the restof Eimer’s book in which he set out to answer three basic ques-tions: what are the causes of variation? Is the modification ofspecies governed by growth? And how does growth influenceevolution? Perhaps surprising to historians familiar with his laterwork, Eimer’s first argument in Organic evolution asserts thetruth of natural selection, meaning that it would operate giventhe pre-existing conditions of hereditary transmission, variation,and differential survival (1890, p. 1). It is in this framework thatEimer presented the central purpose for writing the volume: toilluminate and enumerate the necessary and sufficient conditionsfor, and limitations to, the origin of variation and the impact ofthese limitations on possible evolutionary outcomes. Based onevidence from earlier in his career, and recent studies, Eimer’scentral line of thinking was that organisms cannot vary in anypossible direction, only a few. His basic theoretical motivationwas that all new morphologies are an expression of the processof growth and development (e.g. Eimer, 1890, p. 26). Eimer thenbuilt off these central motivations and elaborated a series oflaws of growth and development that served to generalize thephenomenon of limited variation.

In a sub-chapter titled ‘‘the fundamental causes of the manifoldvariety of organic forms,’’ Eimer expressed his basic logic of causal-ity concentrating on the origin of variation:

According to my conception, the physical and chemical changeswhich organisms experience during life through the action ofthe environment, through light or want of light, air, warmth,cold, water, moisture, food, etc. and which they transmit byheredity, are the primary elements in the production of themanifold variety of the organic world. From these materials thissupplied the struggle for existence makes its selection. Thesechanges, however, express themselves as growth (Eimer,1890, p. 22).

Eimer outlined his basic mechanisms of variation that impact evo-lution based on this conception of the causes of new variation,and the limitations to possible trajectories of evolution imposedby ‘‘laws of growth’’. Historians have focused on Eimer’s adher-ence to the inheritance of acquired characters (e.g. Bowler,1979, 1983). While it was an important part of his theory, hisemphasis in Organic Evolution and later works was squarely cen-tered on the impact of the causes and limitations to variationon evolution.

3.2. Variation in Cope’s theory

Similar to Eimer’s book, the introduction and organization ofCope’s Primary Factors reveals a strong focus on variation. Copewrote that his three central aims in the book were to show thatvariation is initiated by physical causes, variations can be inher-ited, and to coordinate the facts of evolution with the facts of sys-tematic biology (taxonomy) (Cope, 1896, p. 14). He accomplishedthese goals through a three-tiered argument. The first part of hisbook deals with the nature of variation, and Cope used extensivepaleontological evidence to support his claims. He argued that var-iation cannot take place in all possible directions, only along a fewtrajectories. Part two of Primary Factors dealt with the causes ofvariation, specifically focusing on the physical, chemical and ki-netic causes; Cope argued for a simple schema of causes of newvariation as based on physical causes easily observed in the world.The final part of Cope’s work discussed the inheritance of variation.Here Cope brought together his theorizing on heredity, variation,

130 M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132

and the causes of evolution. Based on theories developed through-out his career (Cope, 1868, 1871, 1894), he articulated a full ac-count of evolutionary causation.

Describing Cope’s complete account of evolutionary causation,like Eimer’s and Berg’s, is beyond the scope of this paper owing tothe nuance and numerous ideas involved. At the core of his ideawas the origin of new morphological variants. He developed amultifaceted theory of energies of evolution that captured the no-tion of the efficient cause of new variations (1896, p. vi).4 Basedon the hereditary generalizations of Weismann, Cope articulateda neo-Lamarckian version of evolutionary causation that includedan explanation of why and how new variation originated basedon various energies passed from one generation to the next. Whilethis energy conception of evolution may strike modern readers asforeign, Cope’s purpose in developing this theory was to includea physicalist account for the causes of changes in development(growth and differentiation) and evolution (novel features and tra-jectories). These energies of evolution were not mystical or anti-materialist. They were conjectured energies that could accountfor the impact of physical forces on organisms (as observed inFig. 1). The energy of an organism’s interaction with its environ-ment influenced the hereditary material, thereby producing theinheritance of traits acquired in life. Cope’s energies of evolutionrepresent an attempt to maintain a physicalist and materialist the-ory. He endeavored throughout his book to place the originalcauses of variation, the limitations to variation, and the impact toevolutionary outcomes as the core of his theory of evolutionarycausation.

3.3. Variation in Berg’s theory

Leo Berg was one of the most hardline orthogenetic theorists inthat he viewed evolution as a deeply structured and definitely di-rected process. Berg was dissatisfied with the notion that naturalselection was a satisfactory explanation of evolutionary phenom-ena; this motivated his efforts to articulate the causes and sourcesof directed evolution. As Berg wrote at the beginning of his preface,‘‘the object of the following pages is to show that the evolution oforganisms is the result of certain processes inherent in them [. . .]Evolution is nomogenesis, development in accordance with defi-nite laws, and not, as was believed by Darwin, development dueto chance’’ (1926, p. xvii). Berg showed great respect for the workof Darwin and his followers, yet he began Nomogenesis with alengthy chapter on the insufficiency of natural selection to accountfor evolutionary phenomena. Berg based his argument on a se-quence of premises that would need to be true for natural selectionto account for all of evolution. He argued that for natural selectionto be the sole arbiter of evolution leading to novel features and in-creased adaptation there must be an ‘‘infinite number of inheritedvariations’’ (1926, p. 24). Using quotations from Pierre Louis deMaupertuis and Ernst Mach to guide his readers towards his per-spective, Berg argued that variation is extremely limited, not infi-nite. Based on the extensive evidence for the limitations tovariation, which he presented throughout his text, Berg concludedthat selection could not account for much of the evolution of in-creased complexity or novel forms. Selection was a stabilizing forcein nature, not a creative one.

A thorough discussion of Berg’s argument in Nomogeneisiswould require a lengthy analysis due to the complexity of his var-ious perspectives on the nature of variation and evolution. Thank-fully, he gave a brief account of his overall theory that displays the

4 Cope used the phrase ‘‘efficient cause’’ numerous times in throughout Primary Factorsterm in Metaphysics (Ross, 1924), Cope used this phrase consistently with Aristotle’s origi

centrality of variation without getting overly involved in otherdetails.

Nomogenesis: Organisms have developed from tens of thou-sands of primary forms, i.e. polyphyletically. Subsequent evolu-tion was chiefly convergent (partly divergent), based upon laws,affecting a vast number of individuals throughout extensive ter-ritory, by leaps, paroxysms, mutations. Hereditary variationsare restricted in number, and they develop in a determineddirection. The struggle for existence and natural selection arenot progressive agencies, but being, on the contrary, conserva-tive, maintain the standard. Species arising through mutationsare sharply distinguished from one another. Evolution is in agreat measure an unfolding of pre-existing rudiments. Theextinction of organisms is due to inner (autonomic) and exter-nal (choronomic) causes (Berg, 1926, pp. 406–407).

The argument for polyphyletic origins indicates Berg’s deep com-mitment to the restrictions on variation due to the laws of growthand development. Limits on variation, he argued, were so definiteand imposing that organisms unrelated through descent wouldevolve similar features over time. Homologous characters werethe product of limitations on variation, not just a shared feature be-tween a common ancestor and its descendants. From these argu-ments of convergent evolution and polyphyletic origins, hisreaders could recognize the centrality of the origin and nature ofvariation for his theory of evolution generally.

This synopses of the motivations and central synthetic theoriesof evolutionary causation espoused by Eimer, Cope, and Berg intheir main texts describe how the nature and origin of variationwas central to their theories. These were not simply argumentsagainst Darwinism. Each of these biologists held a role for naturalselection in their views of evolution, albeit a limited one. They fo-cused on the importance of understanding how variation impactedevolutionary outcomes. All three orthogenesists argued that natu-ral selection alone was insufficient to explain evolutionary phe-nomena generally. Cope articulated the central problem in astraightforward argument. ‘‘Selection cannot be the cause of thosealternatives from which it selects’’ (1896, p. 474). By focusing onlimited variation as a central causal component accounting forthe diversity of evolutionary phenomena in books intended for anon-specialist audience, Eimer, Cope, and Berg attempted to ex-pand the traditional view of evolution to include variation as a cen-tral theoretical component.

4. Conclusion

The three case studies presented in this paper show that severalprominent advocates of definitely directed evolution developedbooks to communicate their theories to non-specialist audiences.In Organic Evolution, Theodor Eimer set himself up as the sympa-thetic underdog and then focused his text on the origin of evolu-tionary novelties. Edward Drinker Cope dedicated a great deal ofPrimary Factors to showing how the new series of fossils dug outof the Western US territories revealed evolution and variation tobe directed processes. Furthermore, he used parallels betweenbiology and physics to make his view of the energies of evolutionwidely accessible to non-specialists. In Nomogenesis, Leo Berg ar-gued that changes occurring in nature were akin to mathematicalfunctions: highly constrained and operating based on deep, law-based structuralism in nature. Not only were these books aimedat a non-specialist audience, contemporary commentators on theseworks generally agreed that they were suitable for non-specialist

and other texts on evolution. While he did not directly reference Aristotle’s use of thenal meaning.

M.A. Ulett / Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014) 124–132 131

audiences whether or not they agreed with the theories them-selves. Furthermore, a brief analysis of JSTOR reveals that the term‘‘orthogenesis’’ was being used in many non-specialist journals,driving the conclusion that orthogenesis was popularized fornon-specialists between 1880 and 1930. These findings suggestthat more work is needed on why and how the debates over evo-lutionary mechanism played out in non-specialist journals andbooks during this period.

The second argument in this paper addresses what theseauthors sought to communicate to their non-specialist audience.They developed comprehensive theories of evolutionary causationthat relied on the nature and origin of variation as a central con-ceptual feature. While the details and the motivations of their the-ories differ in certain respects, at the core of Eimer’s, Cope’s, andBerg’s theories were strong arguments that evolutionists mustincorporate the causes and limitations to variation in order to de-velop a full account of evolutionary outcomes. Given this emphasis,the ‘‘eclipse of Darwinism’’ metaphor historians often use to de-scribe theories like orthogenesis is insufficient to account for theirintellectual efforts throughout this period. These orthogenesistswere not merely eclipsing Darwin, they argued that natural selec-tion was insufficient to explain the suite of complex phenomenaand outcomes under consideration by evolutionists. Certainly theiremphasis on the definite directions of evolution prevailed overselection in their theories, but this is in part because the threeauthors took it as their primary purpose to develop novel and com-plex theories at the center of which stood the limited nature of var-iation, not selection. They proposed a re-orientation of the coretenets of evolutionary theory around the generation of new varia-tion, not an elimination of natural selection.

These three case studies show that these orthogenesists soughtto communicate their theories to a wider, public, non-specialistaudience in order to gain support for the wider notion that varia-tion was central to a full explanation of evolution. They sought toredirect public support of evolution around their principles thatinstantiated the nature and limitations to variation as fundamentaland keystone conceptual features of subsequent theories of evolu-tionary causality. While evolution was not yet a discipline duringthe years orthogenesis was under contention, the debates andnegotiation over the central ontological entities and epistemicgoals of evolutionary thinking and theorizing was clearly vibrant.These three texts by Eimer, Cope, and Berg show that certainamong the scientific elite wanted to rally support around theirideas from interested non-specialists. The primary goal in writingOrganic Evolution, Primary Factors, and Nomogenesis was scientificadvance. These authors were not dumbing-down or translatinghard science for the masses to enjoy, as standard models of sciencepopularization-as-translation might suggest. Instead, they wrotethese books to influence the structure of evolutionary theory bygarnering support from outside a small coterie of specialist evolu-tionists. They wanted to use public, non-specialist audiences to im-pact theory internal to the field of evolution. Consequently,historians can place these orthogenesists alongside other authorsthroughout the history of evolution who sought to use science pop-ularization to rally support for their particular views. As such, thispaper fits nicely alongside the other essays in this special sectioninvestigating the multiple valences and motivations for sciencepopularization. The nuanced and important dynamics betweenevolution and the public will become increasingly clear as histori-ans continue to investigate reciprocity between evolutionary theo-rizing and non-specialist audiences.

While the orthogenesists made a valiant attempt to bring theirideas to non-specialists, they ultimately failed. With the rise of theModern Evolutionary Synthesis in the 1920s through 1940s, themajor players in evolutionary theory developed a core set of prin-ciples that synthesized the sub-disciplines biological sciences

under the banner of a unified evolution (Mayr & Provine, 1980;Smocovitis, 1992, 1996). Ronald Fisher (1930), Sewell Wright(1932) and J. B. S. Haldane (1932) mathematized the central ele-ments of natural selection and Mendelism into population-statisti-cal genetics (Provine, 2001). Additional work by TheodosiusDobzhansky (1937), Julian Huxley (1942); Ernst Mayr (1942);George Gaylord Simpson (1944) and Ledyard Stebbins (1950),around whom the newly forming discipline of evolution centered,set the basic framework for evolutionary theory in the mid-twen-tieth century. Unfortunately for the orthogenesists, their theoriesof definitely directed evolution and the centrality of the natureand origin of variation as causally impacting and driving evolutionhad no place in this new synthesis. The emphasis by the architectsof the Synthesis on random genetic mutation and recombination,and the transformation of gene frequencies in populations throughnatural selection, left no conceptual space for theories concerninghow genetic variation produced novel morphologies. Despite thefailure of the orthogenesists to retain non-specialist supportersand impact the core logic of evolutionary theory in the 1930sand beyond, the approach towards popularizing evolution under-taken by Eimer, Cope, and Berg discussed in this paper lived on.Subsequent generations of evolutionists critical of the explanatoryadequacy of the Modern Synthesis, seeking to expand it, also madetheir case to non-specialists in an effort to influence the directionof evolutionary theory.

Acknowledgments

Many thanks to Myrna Perez Sheldon, Manfred Laubichler,Vassiliki Betty Smocovitis, Brian Hall, Amy Shira Teitel, ChristopherC. Dimond, and Erick Peirson for their insightful comments.

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