Wednesday, 28 November 2018

The Comicreader’s Guide to the Historiography of Science

Abstract. This is neither a comic nor a piece of history or science. It is rather a meta-level comparison of two narrative formats—comic or graphic novel with historiography. The insights gained from this comparison are then applied to examples from the history of evolutionary theory, in order to show how the analogy can serve as a tool for visualizing particular narrative structures and functions.

The explanatory role of narrative is a topical issue in philosophy and history of science (see Morgan and Wise 2017, and articles following in this special issue called Narrative in Science). In this quest, images are often used as analogies that can visualize narrative structures and their functions (e.g., Morgan 2017). John Lewis Gaddis, for example, begins his excellent book The Landscape of History with Caspar David Friedrich’s painting The Wanderer above a Sea of Fog (fig. 1). This summons up Gaddis’s own sense of what historical consciousness is all about. Historians focus their attention, from whatever vantage point they can find, on where they have been and turn their back on concerns of the present (Gaddis 2002, p. 2).

Fig. 1.: The Wanderer above the Sea of Fog by Caspar David Friedrich (around 1817). Hamburger Kunsthalle, Hamburg, Germany (picture taken by Elke Waldorf).

Soon, however, Gaddis needs to exchange this gazebo retrospective with other illustrative allegories and metaphors for the historian’s perspective. An eagle-eye (remote sensing) view can see what is happening in the valleys of the metaphorical landscape but will miss the action going on under canopies or roofs. Participant or protagonist reports can provide the latter, but will be limited to their individual experiences (see section 3, below).
    By chapter two, Gaddis’s metaphors are in disarray. A map is better than the eagle-eye view at conveying the idea that the landscape (history) is a representation that has been construed by someone. But he needs to depart from these static metaphors and to admit that historians can manipulate time, matter, and space in ways that neither a look-out, a map-reader, or a protagonist could. Historians can scale dimensions up and down by zooming in and out of situations. Zooming in, they can spy out particular events, like immaterial ghosts, without ever getting embroiled in the action (like time-travelers in movies). They can not only de-materialize themselves but also render the past scenery concrete or abstract. And they can retard and speed up the passage of time by jumping large swaths of time with a few sentences only to expand a crucial moment by treating it at a length that takes much longer to read or enact. That is, Gaddis needs to add allegories of dimension jumping, time traveling, and the like to the wanderer’s retrospective from a promontory.
   This suggested to me that comics may provide a more versatile analogy for historiographic narratives, even though the proposition may seem preposterous at first. It will seem less so after understanding the comic as a narrative format rather than a genre. Most people think of the comic or graphic novel as a genre and do associate it with either funny animals (e.g., Donald Duck) or superheroes. However, this is far from gauging the diversity of comics. Some are (auto-)bio-graphic novels (e.g., Bechdel 2007 on her family life, father’s suicide, and homosexual coming out; Dewilde 2016 on his surviving the terror attack on the Parisian night club Bataclan and finding back into life thereafter), some are journalistic war-zone reportages (e.g. Sacco 2009) or documentaries (e.g., Mandel and Bouagga 2017 on the refugees’ Jungle of Calais) and many deal with science in an instructional, educational, or edutainment form. Narratives of any genre can be put into the format of a comic or graphic novel. The format has been analyzed by McCloud (1994), Eisner (2001), Jüngst (2010) and many other comic makers and experts. All agree that it is a sequential art requiring a succession of still images. Whereas the story of a comic or graphic novel can be translated into many different media (e.g., film, audio play, text), the format is limited to media that can feature sequences of still images whether on paper, walls, or in digital media.
    The advantage of the comic over other narrative formats is that its structures and functions are rather obvious. They almost illustrate themselves. Therefore, the comic format is a good foil against which to compare narrative structures and functions in the history of science, which is a far more complex animal. Not each element, function, form of representation, or perspective in comics finds an analogon in the history of science but, in comparing these narrative formats, differences can be as informative as similarities.

1 The comic format
Comics and graphic novels will be obvious representations, even if they are documentary or biographic by genre. Therefore, the comic format has the advantage that nobody gets confused about the status of the narrative as a representation that has been constructed. This is not true for history writing, where their representational status needs emphasizing (Gaddis 2002).
    Comics are montages of both words and images (Eisner 2000, 8) where visual regimes (like perspective, symmetry, or resolution) are integrated with narrative ones (like grammar, syntax, plot). This is also true for pieces of history or science. Admittedly, the graphic character of comics dominates over the textual, whereas the reverse is true for history or science. The comic format is, nevertheless, closer to the history of science than purely graphic formats, like art canvas. The analogy between the comic and historiographic format is already closer than with others, before their texts are even written and their images even drawn.

1.1 Typical elements and their narrative functions
Figure 2 shows a prototypic comic strip with the usual elements being labelled in red. These elements are panels, gutters, captions, balloons, soundwords, and speedlines. The panels are snapshots of the story. They illustrate the narrative. The panels are separated by gutters. While these seem to be empty spaces, the readers need to construct the narrative from the snapshots by actively filling the void of the gutters with the help of their imagination. The readers have their minds in the gutters. The captions are explanatory comments that provide context. Balloons contain direct speech or thoughts of the protagonists. Soundwords evoke sound and speedlines evoke motion in the imagination of the readers.

Fig. 2: Typical elements of a comic (after Jüngst 2010, 14, red labels added).

1.2 Comparing the comic with the historiographic format
Comics and graphic novels lose their tension, when the information of the words simply duplicates that of the images. While this must be avoided in many genres put into the shape of a comic or graphic novel, such redundancy may be desired in educational or information comics. For example, in comics made for learning foreign languages images illustrate the meaning of words. Therefore, words and images represent the same things. Likewise, suspense is a desideratum in text-based thrillers and whodunits but not in scientific or historiographic writings.
    The comic panels (snapshots of the story) are analogous to pieces of the historical record. In history of science, these can be publications, data sets, pieces of correspondences, etc. The work of constructing a story from these snapshots is not left to the readers but provided by the author. This work is necessary for several reasons. First, the pieces of the historical record usually do not readily suggest a narrative by mere juxtaposition. Second, the pieces of the historical record are not necessarily snapshots of only one narrative. Sometimes they are too detailed and need to be stripped down, in order to represent a snapshot in the proposed narrative. Sometimes they are too meager and need to be augmented, in order to do so. And generally, they are very heterogeneous in media type and content. Some are texts, some diagrams, some data sets, some images, some theories, some methods, some instruments, some abstract, some concrete. Mere juxtaposition does not suggest a narrative. For these reasons, historians fill the spaces (gutters) between their record pieces with a lot of text that relates one piece to the next. Historians have their minds in the gutters.
    Balloons have their analogon in quotes and soundwords have a less direct analogon in metaphors and figurative speech. A soundword is an item of text that evokes a sound in the mind of the reader. Conversely, a metaphor or figure of speech is a piece of text that evokes an image in the mind of the reader. Historical narratives have no need for a special element evoking motion, like speedlines do in comics, because motion is simply described by words (e.g., ran, drove, speedily).
    What would happen, if a history comic transformed into a history book? The context providing captions would increase to pages of text. The gutters would expand even wider and fill with text forming whole chapters. The panels would shrink and attain various forms ranging from vintage images to vintage pieces of text. Soundwords would turn into metaphors and allegories and often migrate into the gutters. Speedlines would be replaced by words of motion and balloons by quotes of relevance. Text would thus invade the panels. Whenever authors conceived of producing their own illustrations of a historic situation or process, however, images would also invade the gutters. That way, the graphic novel would turn into a book of history as was well-nigh prerequisite, if the process was to count as a transformation of the comic into the historiographic format.

1.3 A difference that sheds a light on a philosophical issue
One unresolved issue of the history and philosophy of science concerns the relation of narrative and, respectively, scientific data or historical records (Morgan and Wise 2017). Does the narrative make (construe) sense of of the data and records, or does it discover their meaning? At first sight, the comic-format analogy seems to support the position that the images (analogous to data and records) imply the narrative, whereas the dominance of text in historical publications seems to support the opposite. Assume, however, a person with a brain damage of its narrative faculties. That person would neither be able to read the story from the images of a comic, no matter how narrow or absent the gutters, nor would it be able to get the narrative from the text of a history, no matter how detailed in prose and relieved of esoteric data and vintage records. Likewise, the significance of scientific data or historical records may often remain obscure without a narrative, but the narrative will remain an irrelevant fancy without data and records. That is, the difference between the dominance of images in comics and text in histories can be used instructively.

2 Graphic regimes in comics
2.1 Duration in comics (manipulating the time)
The space-time analogy is an inherent feature of sequential art (Eisner 2000, 25; McCloud 1994, 100). The sense for the passage of time works by associating spatial with temporal distance. Excluding literary tricks like flashbacks and so on, the chronology of images establishes a sense of time passing by. The comic reader connects images as though they were snapshots of a process in time. Just how much time passes from panel to panel is not determined by an external chronometer that ticks away independently of the narrative. It can be anything from a split second to an aeon. Again, the sequential art is closer to text-based narratives, where sentences can bridge various amounts of time, than non-sequential arts.

2.2 Forms of representation (transforming the matter)
Comics can represent something in a concrete, abstract, or metaphorical form. The form of representation can switch from one panel to the next and different forms of representation can even be interlaced within one panel. Figure 3 shows a page from a science-comic featuring all three forms of representation. The top panel even interlaces concrete with abstract representations. By abstract I do not mean the abstraction of iconic from real images as in the middle panel (fig. 3, the figure of Barak Obama). Such icons still represent things that eyes could see in reality. The arrows in the top panel of figure 3, however, represent scientific conceptions that are not visible to the eye. Here, the arrow coming in from the sun represents electromagnetic waves in the range of visible light. The arrows that go out from the earth and bounce back from the outer atmosphere, however, represent a mixture of things: electromagnetic waves in the infrared range (that is, heat waves) are partly reflected back to earth, but their energy is also absorbed by molecules and converted into the kinetic energy of these molecules. As kinetic energy of molecules it can no longer escape into space. That the visual representation of the greenhouse effect is incomplete, however, is irrelevant to the current point that comics can visualize abstract concepts of science.

Fig. 3: From The Great Transformation. The top panel interlaces concrete and abstract representations as well as tele- and macroscopic perspectives. The bottom panel is a metaphorical representation (after Hamann et al. 2014, 19, red explanations added).

2.3 Perspectives (jumping the dimensions of scale)
Comics jump dimensions of scale easily. For example, one panel may show a remote (telescopic) perspective on a situation and the next a macro-, micro- or even submicroscopic perspective. While this jumping of dimensions of scale usually occurs between panels, the different perspectives can also be interlaced within one panel. As already seen in the previous section, the top panel of figure 3 interlaces an abstract representation of the greenhouse effect with a concrete, though iconic, representation of Hans Joachim Schellnhuber. But is also interlaces a telescopic with a macroscopic perspective. Such jumps between and interlacing of perspectives also occurs in other forms of narrative. They are even necessary in order to overcome a rock-paper-scissors like dilemma of single perspectives in historiography (see following section 3).

3 A rock-paper-scissors dilemma of single perspectives
3.1 The gazebo retrospective
Gaddis (2002) opened his book with a gazebo perspective and suggested that it could represent the perspective of historians focusing on the past and firmly turning their back on present concerns. However, it may as well represent a limited perspective, where the author has an elevated point of view but does not see the goings-on in the valleys of the landscape. Abridged accounts, as can often be found in educational rather than historical or scientific publications, lead from a presumed past to a fancied present by connecting the landmarks of a research history in a straight line. They do not check whether the nether regions of that history support the straight narrative. Take the online lesson Key Events in the History of Biological Study by Meredith Mikell (2018) at the online learning platform It states:
“Around the same time, British naturalist Charles Darwin proposed his theory of evolution by natural selection in his work, On The Origin of Species, following his famous voyage on the HMS Beagle to the Galapagos Islands. He was not the first or only scientist to suggest evolution as the cause of biodiversity; Alfred Wallace had independently also proposed that evolution occurs as descent with modification. The theories of Darwin and Wallace were highly controversial at the time, but establishing the concept of evolution is considered to be the single most important contribution to the study of biology. These concepts were furthered by the works of Gregor Mendel on inheritance, for which he was considered the father of genetics.” (Mikell 2018)
The next paragraph jumps to the molecular structure of DNA and credits Rosalind Franklin with the discovery of the double helix rather than James Watson and Francis Crick. Leaving the factual errors aside, this is an abridgement connecting landmark publications in a straight line without any regard of the contorted historical paths in between. Figure 4 (left) illustrates this, by allegory, with a path that seems to pass over three hilltops in a roughly straight line. One problem with the abridged gazebo account of Mikell (2018) is that the Mendelians turned against the Darwinians and proposed mutation as the ultimate source of variation instead of Darwin’s conditions of existence or Weismann’s sexual reproduction (Stoltzfus and Cable 2014). From an eagle-eye perspective (fig. 4, right), the street turns out to be curvy and loop back on itself at times.

Fig. 4: Path over hills. Left: gazebo perspective. Right: Map-reader's view. Circles represent hills.

3.2 Remote perspectives
The eagle-eye perspective has its own shortcomings. In our landscape analogy, the eagle does not see what goes on under canopies and roofs. The peers of a field might seem to move coherently into the same direction, when a closer surveillance would record significant disagreements among them. Unless such disagreements boil over into overt controversies, they often get glossed over in statements made from an eagle-eye perspective, in order to give an overview or introduce to the general topic. It is a small step from there to historical oblivion.
   For example, such amicable disagreements were important for the advance of theory on the evolutionary significance of sexual reproduction in the 1970s. Here is the context. In the late 1960s, evolutionary biologists took a U-turn that transformed sexual reproduction from the default mode of reproduction into an anomaly and, conversely, turned asexual reproduction into the expected but anomalously rare default mode. Weismann (1889, chap. 5) had rejected the conditions of existence as the ultimate source of heritable variation. Since he needed such a source of heritable variation, lest natural selection grind to a halt, he seized sexual reproduction as that source instead. Fisher (1930) and Muller (1932) in turn replaced it by mutation as the ultimate source of heritable variation, but they kept sexual reproduction as a mode of speeding up the population-wide process of adaptation. This implied a benefit of sex for groups, like populations or species, which got explicitly rejected in the late 1960s. Without this group benefit of sex, however, the ubiquity of sexual reproduction among animals and plants turned into an anomaly.
   The pioneers George Williams, John Maynard Smith, and Bill Hamilton were not mental triplings. They disagreed on fundamental issues like the cost of sexual reproduction or the relevance of parasites for its evolutionary maintenance. In particular, Williams (1975) conceived the cost of sex as the cost of reducing the relatedness, r, of parents to their offspring from 1 to 0.5, whereas Maynard Smith (1978) conceived it as the cost of males that contribute nothing (except sperm) to reproduction. Williams’s cost occurs in all sexual reproduction, whereas Maynard Smith’s is absent from species where gametes are of equal size or both parents care equally for the offspring.
   Likewise, Hamilton’s model assumptions disagreed with Williams’s. Hamilton modeled the differential effect of pathogens and parasites, that can quickly adapt to overcome their host’s defences, on asexual mutants in species with otherwise obligate sexual reproduction (e.g., Hamilton et al. 1990). Williams (2000) challenged the applicability of these red-queen models to organisms with a complex life-cycle of the strawberry-coral type. They produce (philopatric) offspring that stays close to its parents (and its parents’ pathogens and parasites) as well as dispersing offspring that gets away from the parents. However, the philopatric offspring is clonal and the dispersing offspring recombinant. If fast adapting parasites were the selective pressure keeping sexual reproduction beneficial, organisms with this life-cycle should do the opposite (see Dagg 2016; 2017 for details on these disagreements).
   Accounts of such amicable but important disagreements are more likely to be gotten from the reports of participants (e.g., Trivers 2010; 2015, 195) or, vicariously, through preserved pieces of correspondence (see Dagg 2016), biographical notices, etc. Lumping these pioneers together on issues they disagreed about is unhelpful historically though not necessarily in other respects:
“It is important to realize that the ‘cost of sex’ [meaning Maynard Smith’s cost of males] and the ‘cost of meiosis’ [meaning Williams’s cost of reducing relatedness] are not different concepts.” (Bell 1982, 63)
“George Williams, whose evolutionary ideas have always seemed convergent like those of a twin or older brother from whom I was parted at birth.” (Hamilton 1996, 354)
“Anisogamy leads to a cost of sex, whether the gamete types are produced by the same individual (hermaphroditism) or by different reproductive morphs (males and females) of the same population (Maynard Smith 1971a, 1978; Williams 1975; Bell 1982).” (Jokela et al. 2009, S43)
The first quote is factually wrong, the second states a sentiment rather than a fact, and the third is a simplification lumping three scholars together (in parenthesis).

3.3 The protagonist’s or participant’s report
Gaddis (2002, 4) mentions early on that the participants in a story usually lack an expanded horizon beyond their immediate experience, unless they can find some lookout point. This leads us back to the need of a gazebo and to a rock-paper-scissors like dilemma in historiography. Each perspective has its advantages over the antecedent and its disadvantage over the subsequent.
   The participant’s account of Robert Trivers (2010; 2015, 195), for example, relates how George Williams challenged one of Bill Hamilton’s theories during a memorial session for the deceased Hamilton.
“George got up and said, “I wish Bill were here today, because I have a bone to pick with him.” He then proceeded to pick that bone for the entire talk. It had to do with the evolution of sex and patterns of evidence that George had pointed out years ago that contradicted (so George said) aspects of Bill’s parasite approach. I thought it was wonderful. There were those who said that his talk was inappropriate, and why didn’t he just tell stories. But I thought it was perfect for the occasion. Both vintage George Williams – no wasted motion with that organism! – and a tribute to the enduring importance of Bill’s ideas.” (Trivers 2015, 195)
This account leaves the reader clueless as to what the disagreement of Williams with Hamilton was actually about. It lacks some lookout point from which to see the antecedent theories of Hamilton (red-queen model) and Williams (strawberry-coral model) as well. Fortunately, Williams (2000) managed to put his challenge on record (see previous section) in what seems to have been one of his last attempts at doing science before he drifted off into Alzheimer’s. Unfortunately, it has been utterly ignored—possibly—because it occurred in an obituary rather than a regular scientific article.
In conclusion, one perspective is not sufficient for historiography. Therefore, the comic format seems to be a better analogy for what is required.

4 Applying the analogy to examples
4.1 The Song of the Dodo
David Quammen’s The Song of the Dodo (Quammen 2012) belongs to the genre of popular science writing. And its concerns are not purely historical but also the environmental crisis and species extinction. But it contains enough history of science and literary craftsmanship to illustrate some narrative analoga to the comic format.
   Quammen (2012, chap. 1) begins with describing the cutting of a Persian carpet into pieces as a metaphor for habitat fragmentation, unraveling of ecosystems, and species extinction. The comic-format analogon to metaphor is a soundword like:

Chapter 2 opens with cases of species and sub-species that used to live on particular islands, like Madagascar, Bali, or Lombok, but are now extinct (Quammen 2012, 17f). These concrete examples are narrated from a map-reader’s perspective. These mementos of the environmental crisis serve to fetch readers with contemporary environmental concerns where they stand and lead them on to a history of science journey. That journey begins with a gazebo retrospective (p. 18f) that enumerates some landmarks of island biogeography: Charles Darwin’s Origin of Species, Alfred Wallace’s Island Life, Joseph Hooker’s publications on the botany of New Zealand, and The Theory of Island Biogeography (MacArthur and Edward Wilson 1967). Quammen does not molest his readers with this abstract theory itself, but they do get a hunch that such a theory exists.
   Quammen (2012, 19f) continues with some biographic information about Alfred Wallace and Charles Darwin. Before the biography style can put lay-readers off, however, he launches into full participation by interlacing the story of Wallace’s journey in the Malay Archipelago with accounts of his own journey on the tracks of Wallace. By this clever move, Quammen is able to tell the stations of Wallace’s journey from the participant’s perspective. Pieces of Wallace’s historical record get sprinkled into the personal experiences of Quammen or vice verse.
   Thus, before he even launched the story of Alfred Wallace in the Malay Archipelago, Quammen has run an impressive gamut of narrative ploys. He has jumped perspectives from map-reader’s view over gazebo retrospective to participant’s report. He has varied his forms of representation from metaphoric to concrete and even left a hint at the existence of an abstract theory. And he has interlaced the past with the present.

4.2 Dispelling the Darkness
While John van Wyhe’s Dispelling the Darkness (2013) also deals with Alfred Wallace, it is an entirely different animal from Quammen’s Dodo. Whye begins his narrative with an account of how Alfred Wallace conceived his idea of species transmutation through natural selection while suffering a fit of tropical fever on the island Ternate. That is, he begins with a biographic protagonist’s perspective. His chapter 8, however, can serve to illustrate the narrative analogon of zooming in from a telescopic to a macroscopic scale and simultaneously retarding the passage of time to slow-motion. In this chapter, Wyhe addresses the plagiarism-claim that Wallace’s famous Ternate essay, which galvanised Darwin into writing up his theory, must have reached Darwin earlier than the latter admitted. For this, Wyhe manipulates the dimensions of scale and time.
   The chapter begins with describing the island of Ternate (featuring several vintage maps), continues with describing Wallace’s house (featuring a floor map of Wallace’s house and a photography of a similar house). Wyhe reviews previous theories about these happenings (gazebo retrospective), before he zooms in to human life-size and decelerates, in order to dissect the happenings of February 1858. He takes on the hat of a ship-company’s clerk, who details the time-tables of departures and arrivals, as well as the hat of an archivist, who matches Wallace’s notebook entries with these time-tables.
   It is not my job, here, to judge the correctness of Wyhe’s conclusions. His chapter stands exemplary for many scholars who have studied the time-tables of potential ships for the Ternate essay in minute detail. In the current context, it illustrates the narrative strategies of jumping dimensions of scale and manipulating the passage of time in history of science writings.

5 Conclusion
I started by suggesting that the comic format is a particularly versatile analogy for historiography. Limiting the use of analogy in history to this one would, nevertheless, constrain authors unduly. If one wished to enrich one’s prose with a diverse oeuvre of metaphors, figures of speech, paintings etc. such a constraint would indeed be gagging. I do not propose to limit the use of analogy in historiography but, figuratively, try to open a new window to fruitful analogizing. I have no other aim, here, or conclusion. A long quote from The Landscape of History indicates that John Lewis Gaddis would have appreciated the use of such a versatile analogy and the fresh air that the young sequential art would have brought to historiographical considerations.
“I fear that this chapter has staggered, even more than the others, under the weight of the metaphors I’ve inflicted on it […]. I make no apologies for metaphors, however, mixed or otherwise. […] For it seems to me that empathy – whether with respect to the past, the present, or the future – absolutely requires them. If we’re to be open to impressions, which is what I’ve argued empathy means, we’ve also got to be comparative. And that, in turn, is just another way of saying that something is “like” something else. […] If metaphors help us think – if, to use yet a final one, they can open windows and let in fresh air – then we have every reason to rely on them, and to do so unashamedly. We need all the help we can get.” (Gaddis 2002, 128)
If the comic analogy is a solution to a problem that John Gaddis never had, then that will be due to the fact that he is an accomplished history writer. The above sections showed, nevertheless, that differences in the comic and historiographic format can be used instructively (section 1.3) and that similarities can be used to to gauge the narrative craftsmanship of a history writer (section 4). This analogy may well turn out to be a useful lamp for seeing structures and functions in historiographic narratives via comparing them with the graphic techniques of comics. If the comic analogy helps any student to decipher or compose a history of science, this article will have served its purpose.

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Bell, Graham. 1982. The Masterpiece of Nature: The Evolution and Genetics of Sexuality. Berkeley and Los Angeles: University of California Press.
Dagg, Joachim. 2016. On Recognising the Paradox of Sex. Philosophy & Theory in Biology 8.
Dagg, Joachim L. 2017. How Counterfactuals of Red-Queen Theory Shed Light on Science and Its Historiography. Studies in History and Philosophy of Biological and Biomedical Sciences 64, 53–64.
Dewilde, Fred. 2016. Mon Bataclan : Vivre encore. Paris: Lemieux Editeur.
Eisner, Will. 2000. Comics & Sequential Art. Expanded Ed. Paramus, NJ: North Light Books.
Fisher, Sir Ronald Aylmer. 1930. The Genetical Theory of Natural Selection. Oxford: The Clarendon Press.
Gaddis, John Lewis. 2002. The Landscape of History: How Historians Map the Past. Oxford: Oxford University Press.
Hamann, Alexandra, Claudia Zea-Schmidt, and Reinhold Leinfelder. 2014. The Great Transformation. Climate – Can We Beat the Heat? Comic. Berlin: Wissenschaftlicher Beirat der Bundesregierung Globale Umweltveränderungen.
Hamilton, W. D. 1996. Narrow Roads of Gene Land. Volume 1. Oxford: Oxford University Press.
Hamilton, W. D., R. Axelrod, and R. Tanese. 1990. Sexual Reproduction as an Adaptation to Resist Parasites (a Review). Proceedings of the National Academy of Sciences, 87.9, 3566–73.
Jokela, Jukka, Mark F. Dybdahl, and Curtis M. Lively. 2009. The maintenance of sex, clonal dynamics, and host-parasite coevolution in a mixed population of sexual and asexual snails. The American Naturalist, 174(S1), S43-S53.
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Maynard Smith, John. 1978. The Evolution of Sex. Cambridge: Cambridge University Press.
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Tuesday, 13 November 2018

Motives and merits of counterfactual histories of science

A preprint of my new article is here. The published version is in Studies in History and Philosophy of Biological and Biomedical Sciences:

In the article, I propose a simple way for distinguishing construed from genuine contingencies—the so-called temponaut's test. Suppose the historian in question travelles back in time and, inadvertently, puts his counterfactual history into action. Here's an illustration (that is not in the published article) of the temponaut's test applied to a construed contingency. 😜

Friday, 25 May 2018

Plagiarism software hardly finds significant overlap between Darwin (1859) and Matthew (1831)

[Update 26.5.2018: Now with control assay (blind sample) at the end, in order to render the conclusion valid.]

Some folks incessantly claim that that Charles Darwin (1859: On the Origin of Species) plagiarized Patrick Matthew (1831: On Naval Timber and Arboriculture) by touting similarities in usage in combination with findings that merely show that Victorian naturalists and publishers were connected by less than six degrees of separation. The latter is only to be expected, given that science was a much smaller endeavor back then. Mere connections leading from Matthew to Darwin via acquaintance or citation, along x degrees of separation, does not prove conscious plagiarism by Darwin. Here, I check both books with a plagiarism-detection software, in order to test the claim about similarities in usage proving plagiarism.

The software
WCopyfind is an easy to use software that compares text-files. In order to compare vintage books, like Darwin's On the Origin of Species (1859) and Matthew's On Naval Timber and Arboriculture (1831), you only need to download them as plain text from sites like, or Project Gutenberg and save them in a format that the program can process (e.g., .docx). The program is very lean, fast and easy to use. The download takes a mere second and getting started a mere half an hour. Just click on the link above and try it yourself.

The interface looks like this.

In the image shown above, the parameters are set to report matching strings with a length of four words or more ("Shortest Phrase to Match: 4 Words"). The parameter "Most Imperfections to Allow: 2" means that, here, the program will bridge up to two non-matching words within a phrase thus allowing for some editing. The parameter "Minimum % of Matching Words: 80%" also allows for editing in that only 80% of two passages or phrases need to be identical and will still be reported. "Fewest Matches to Report: 1 Words" actually means that even 1 matching 4-word phrase (not "1 words") will be reported. This is the lowest bar and one match can be expected by mere chance in book of such length.

Basic check
All the above parameter settings are as recommended by the maker of WCopyfind, except the string-length to be matched. Here, the maker recommends a string-length of 6 matching words for reporting. With this default setting, however, there will be 0% overlap between Darwin's and Matthew's book.

There must be some rounding involved in this reported 0% overlap, because some hits can still be found in viewing both texts side-by-side. But these are entirely fortuitous and would occur in any two texts of a certain length. They signify no plagiarism as the immediate context of the matching phrases shows.

For example, such a search yields matches of the following kind: "we have also seen in the," which Darwin continues with "second chapter" and Matthew with "moss of Balgowan."

Other matches require some more context, in order to get the fortuitous triviality of the match:
"in many cases it is most difficult to" (Darwin 1859) vs

"in cases where it is difficult to" (Matthew 1831).
The green words are the ones that have been bridged and the red words constitute the 6-word match. However, the immediate context of this match is completely different in both books:
"Although in many cases it is most difficult to Conjecture by what transitions an organ could have arrived at its present state yet, considering that the proportion of living and known forms to the extinct and unknown is very small, I have been astonished how rarely an organ can be named, towards which no transitional grade is known to lead." (Darwin 1859)

"Forests of Ficus sylvestris are sometimes destroyed by insects under the bark, in cases where it is difficult to decide whether external circumstances, such as a dry warm season, has been promotive of the increase of the insect itself, or has induced some disorder in the plant, rendering the juices more suitable aliment to the worm." (Matthew 1831)
One actually needs to reduce the string-length down to 4 words, in order to get to the point, where the phrase that Mike Sutton, criminologist of Nottingham Trent University, takes to signify that Darwin plagiarized Matthew:
"this process of natural selection" (Darwin 1859) vs

"this natural process of selection" (Matthew 1831).
The immediate contexts:
"Therefore, I can see no difficulty, more especially under changing conditions of life, in
the continued preservation of individuals with fuller and fuller flank-membranes, each modification being useful, each being propagated, until by the accumulated effects
of this process of natural selection, a perfect so-called flying squirrel was produced." (Darwin 1859, p. 181)

"Mans interference, by preventing this natural process of selection among plants,
independent of the wider range of circumstances to which he introduces them, has increased the difference in varieties, particularly in the more domesticated kinds and even in man himself, the greater uniformity, and more general vigour among savage tribes, is referrible to nearly similar selecting law the weaker individual sinking under the ill treatment of the stronger, or under the common hardship."(Matthew 1831, p. 308)
It is true, both contexts are evolutionary, but does that prove plagiarism by Darwin of Matthew? The perfect matches amount to 2% of Darwin's book and 4% of Matthew's, most of it the trivial stuff that is clearly coincidental. And allowing for the bridging of words and only 80% matching words in phrases did not change this for the overall matches.

Control assay (blind sample)
The problem with purely random word-salads is that they are not grammatical. That is, two word-salads will show less matches, by pure chance, than two independent texts, because grammar, rules, as well as an era's fashion of speech force language into similar strings of words at times. A blank sample or control assay must, therefore, compare two texts that are from the same time and culture, whose authors did not imitate each other. I assume (with no expertise in English literature on my part)* that Oscar Wilde's (1854-1900) tastes were sufficiently different from that of Amanda Minnie Douglas (1831-1916), author of juvenile fiction like the Little Girl... and Helen Grant... series, and that they did not copy each other. I compared their novels The Picture of Dorian Gray (1890) and A Little Girl in Old Boston (1898) using identical parameter settings as above.

* I assumed that a homoerotic book by an openly homosexual author would have little in common with the girly romance novel of a spinster.

Here, the perfect matches amount to 3% in Douglas's book and 4% in Wilde's and, respectively, the overall matches amount to 3% and 5%. This is slightly higher than in the comparison of Darwin's Origin with Matthew's Naval Timber (see above) suggesting that there is no more reason to assume that Darwin plagiarized Matthew than to assume that spinster Douglas plagiarized scandalous Wilde. Surely, the 2% and 4% overlap between Darwin's and Mathew's book, respectively, is within the range of what is to be expected from any pair of books of roughly the same age and culture.

A note of caution to those who are fond of relying on algorithms rather than reading and thinking themselves, the program missed a four-word-shuffle, because it found an overlapping perfect three-word match first. That is, the program overlooked the following matches:
"but it seems somehow" (Douglas 1898, p. 11) vs

"but somehow it seems" (Wilde 1890, p. 14).
Instead, Wilde's sentence is matched with another of Douglas, because of a three-word match that required no bridging:
"Now, it seems to me I never could learn French." (Douglas 1898, p. 99)
"It is a silly habit, I daresay, but somehow it seems to bring  great deal of romance into one's life." (Wilde 1890, 14)
Obviously, neither the perfect three-word match nor the four-word-shuffled match has any significance concerning plagiarism. Apparently, four-word-shuffled matches do occur by mere coincidence at times. One should, therefore, take the occurrence of such a match between Darwin (1859) and Matthew (1831) with a grain of salt.

Some readers might think that the string "natural process of selection" is charged with meaning in a way that "but somehow it seems" is not and, therefore, the former string carries biological significance in a way that the latter does not. However, the first time that the string "natural process of selection" has been used in publication (as far as the digitized record goes) was by Sigmund Spaeth (1829. The Encyclopedia Americana, Vol. 19, pp. 636-639). This entry in an encyclopedia, however, carries no significance concerning natural history. It is about music appreciation and contains the four words in a context that has nothing to do with biology:
"Program music will generally be found easier to grasp than absolute music, and this is again a natural process of selection." (Spaeth 1829, p. 638)

Sunday, 22 April 2018

Why Charles Darwin did not own the Two Essays by W.C. Wells (1818) before the Beagle voyage or after

Tall claims
John S. Warren (2017. Darwin's missing links. History of European Ideas 43(8): 929-1001) claims that Charles Darwin bought William Charles Wells's (1818, Tow Essays: One upon single vision with two eyes; the other on dew. ...) before he even embarked on the voyage of the HMS Beagle. Charles Darwin read Herschel's Premier Discourse at Cambridge, who praised Wells's Essay on Dew as a role model for anybody attempting to do science. Warren promptly concludes:
Darwin required no prompting; he quickly acquired a copy ofWells’ ‘Essay on Dew’.259 The copy in Darwin’s library in Down House is identified in the Darwin Digital Library of Evolution, Bibliography and the ‘Key to Annotations’ as ‘Pre-B’ and ‘Down’: it was in Darwin’s private library pre-Beagle voyage, later located at Down House; that is, since the Beagle sailed in December 1831, the paper was acquired no later than 1831 (Appendix 1).260
259 Wells, Two Essays.
260 American Museum of Natural History (AMNH), 2005. Accessed January 25 and September 27, 2009. See also Appendix 1.
Appendix 1
The Darwin Library and DDLE are currently accessible on the AMNH website through the following links, as at 13th January, 2017: Darwin Manuscript Project (DMP) Website ( To go straight to the William C Wells reference, the current URL is ( (Publications in EvoLit.bib p. 23). Excerpt from AMNH, 2005. ‘Darwin Digital Library of Evolution’ ( web-page listing for the relevant section of the alphabetical letter ‘W’, showing William Charles Wells’ ‘Two Essays’ in Darwin’s private library, with immediately adjacent names. Wells’ book was acquired by Darwin before the end of 1831. The entry for Wells, 1818 is annotated, ‘*’ (the identifier for Darwin’s private library), ‘Pre-B’ (pre-Beagle voyage, but not known on board), and ‘Down’ (Darwin’s library, later located at Down House, Kent): see the Darwin Digital Library of Evolution, ‘Key to annotations’.
Whatever the historical significance of Wells's Essay on Dew (1814. Article IV.—An Essay on Dew, and several Appearances connected with it. The Quarterly Review; London Vol. 12(23): 90-99) the significance for the history of biology of the later published Two Essays lies in neither of the two essays, but in an appended "account of a female of the white race, part of whose skin resembles that of a negro ..." This last account contains an anticipation of natural selection as a means of adaptation of races to their different conditions. That is, Wells did not go as far as to suggest the origin of new species through natural selection, but he got pretty close.

Screwed records
Now, Warren took an information provided by Charles Darwin's Library (at the website of the Biodiversity Heritage Library, BHL) as stating that Darwin owned that book before he even embarked on the Beagle Voyage. (In fact, Warren refers to the American Museum of Natural History, but that link does not exist anymore and the AMNH now relays you to the BHL's Charles Darwin Library.) This would be unproblematic, if the key to annotations had traveled along with the alphabetical list, but it hasn't. Page 84 of this list states: 
The crucial part, here, is that in square brackets: "Down, pre-B, ED." Unfortunately, the Charles Darwin Library or BHL does not give any information as to the meaning of these abbreviations (annotations). While SCRIBD still has a relic of the original list collated by the staff of the AMNH, this only tells us that the key to the annotations can be found in the book Charles Darwin's Marginalia edited by Di Gregorio & Gill (1990, Garland, New York).

Thankfully, Greg Priest (@greg_m_priest) tweeted the key to the symbols and the page with the entry of Wells's Two Essays.

Di Gregorio (ed.) 1990. Charles Darwin's Marginalia: Key to symbols

"ED" seems to be missing from the key to symbols and Warren (2017) simply ignored it. He took the annotation to mean "book located at Down House, Kent" and "book owned prior to Beagle voyage but not known on board," as the key to symbols states for the meaning of "Down" and "pre-B."
However, Warren went further than that. He claimed that Charles Darwin bought the book while in Cambridge and owned it ever since, studiously avoiding the question what that "ED" at the end of the annotation might mean. In my opinion, it hints at one of the many Erasmus Darwin's rather than our Charles. That is, even if Di Gregorio's annotation was correct, it would not mean that Charles Darwin had bought the book before his Beagle voyage and owned it ever since.

However, the information of Di Gregorio, the BHL and AMNH is probably wrong anyway.

The first record
H. W. Rutherford (1908. Catalogue of the library of Charles Darwin now in the Botany School, Cambridge. Compiled by H. W. Rutherford, of the University Library; with an Introduction by Francis Darwin. Cambridge: Cambridge University Press) was the first at Cambridge University, who collated a list of the books that actually did enter their collection of Charles Darwin's books in 1908, and Francis Darwin wrote the introduction to that catalogue.

The first thing to notice is in Francis Darwin's Introduction:
THE library of Charles Darwin has now found a permanent home in his own University, and it is perhaps appropriate that it should be in the Botany School, since it was a Cambridge professor of Botany who, more than any one man, determined his career as a naturalist.
The collection is not identical with that at Down. Thus the books he wrote and some few others from Down are in my own possession. There are also a few books of mine which, for the sake of convenience, are kept in the Darwin library: these are marked with an asterisk in the catalogue. (Rutherford 1908, p. vii, emphasis added) #
#[The books from Francis Darwin's private possession have probably been integrated into the collection by now.] Next thing to notice is the explanation of the abbreviations:
* Books thus marked were not in the Library at Down. ... (Rutherford 1908, p. xiv, emphasis added)
  And, finally, there is the entry for W. C. Wells:
*Wells (William Charles). Two Essays: one upon single vision with two eyes; the other on Dew: &c. 8vo. London, 1818. 24 (Rutherford 1908, p. 89)
The first record by H. W. Rutherford (1908) clearly contradicts Di Gregorio's annotation "Down, pre-B, ED," which has first been adopted by the AMNH and then by the the Biodiversity Heritage Library. While this annotation suggests Down House as the location of the book, the asterisk of Rutherford and the introductory statements by Francis Darwin state that Francis added this book to the collection, which has since been called the Darwin Library. That is, it was not from Down House or, anyway, not from Down House while Charles Darwin still roamed it.

Maybe it came down to Francis Darwin from Erasmus Darwin (either one). Maybe Francis stored it with some other books of his in Down for a while, before they went to Cambridge. Maybe the collator of the BHL's list made some mistake. Whatever the explanation of the screwed-up information at the BHL, it can surely not be taken as proof that Charles Darwin owned Well's Two Essays long before he even went on the Beagle voyage.

Tuesday, 17 April 2018

Darwin's Questions & Experiments notebook. One entry, many interpretations

Here's an entry from page 3 of Darwin's "Questions & Experiments" notebook (1839-46).

The poor performance
A naive and surprised reaction will be based on the fact that the only work on forest trees one usually ever heard of is Patrick Matthew's book On Naval Timber and Arboriculture, because it has some relation with natural selection. Thinking that Matthew was the only source for anything on forest trees will lead to an interpretation as follows:

First Interpretation: The fact that Darwin shows interest in forest-trees and their variability in nursery gardens proves that he had read Matthew (1831).

However, this is not the only possible interpretation, especially if you know something about the pertinent literature from around 1831.

Second Interpretation: There were others before Matthew (1831) writing about forest trees and their cultivation. An interest in the issue does neither prove nor disprove a knowledge of Matthew (1831).

Finally, having actually read and understood Matthew (1831) can even lead to the opposite of the first interpretation.

Third Interpretation: The question whether forest-trees sport more in nurseries than in nature as a consequence of the special conditions in nurseries, like manuring, indicates that Darwin had not read Matthew (1831) or else he would not have asked this. Matthew (1831, 308) had made it clear that the variability only appears to be increased under domestication, because of the lack of natural selection there. For Darwin to get there, it would still take years of studying barnacles and other organisms.
"Man's interference, by preventing this natural process of selection among plants, independent of the wider range of circumstances to which he introduces them, has increased the difference in varieties, particularly in the more domesticated kinds; and even in man himself, the greater uniformity, and more general vigour among savage tribes, is referrible to nearly similar selecting law—the weaker individual sinking under the ill treatment of the stronger, or under the common hardship." (Matthew 1831, p. 308)
One could, then, continue with a useless controversy about this entry and what it signifies about Darwin's knowledge or ignorance of Matthew (1831) or quip something like: "Had Darwin asked whether Forrest Gump sports much in nursery gardens, I'd surely know the answer." However, the entry also provides the chance to do something more interesting.

The historical performance
Let's first look at the context of Darwin's notebook entry. The very first question at page 3 about crossing two halfbred (we'd say heterozygous) animals and their offspring being uniform already shows that Darwin was on the track of hybridizers* in particular rather than on Matthew's general observations about the variability of trees in forests and nurseries.

* [By the way, Gregor Mendel was one of these hybridizers, and he would later answer Darwin's question with a resounding "No." He started from two strains of peas that differed in one trait (e.g., colour of the flowers), but were truebred (that is, homozygous) for that trait. Crossing this parental P-generation yielded a halfbred (that is, heterozygous) F1-generation, which was was uniformly showing the dominant trait. But crossing these halfbred F1 plants with each other yielded an F2-offspring showing the parental traits in the ratio 3:1. Hence, the answer is "No!" to Darwin's first question at page 3: "If two halfbred animals exactly alike be inbred, will offspring be uniform?"]

Furthermore, Darwin's entries at page 21 of the same notebook show that he had a particular problem with trees and inbreeding. He believed that some degree of out-breeding was necessary for the health of organisms but could not understand how that should be possible in in mixed forests. Here, the scattering of trees of the same species should lead to close inbreeding between flowers of the same tree despite insects or wind.
     Darwin even wondered whether fruit trees can flower and their fruit ripen in Scotland—a question he'd never have jotted down had he been in the know of Matthew's writings.
"(2) History of fruit trees far north in Scotland — do they flower — do they live healthily, or does fruit merely not ripen. — The point to attend to is whether good & plenty of pollen is produced. & 2d if so, whether concepcion takes place, — the mere fact of seeds ripening has scarcely any no relation to hybrids." (Darwin's Q&E notebook, p. 21)
     At the same time, experiments by hybridizers, like William Herbert, had shown that hybridization can boost the variability of the offspring generally referred to as "sporting." If trees were inbred in mixed forests, and their out-breeding had similar effects as the hybridizing in experiments by hybridizers, the close proximity of trees of the same species in nurseries should lead to an increase of sporting in their offspring.
     Darwin's further question about the manuring of trees in nurseries ("are the is the ground much manured") hints at another doctrine, which had been well established among horticulturalists and animal breeders of Darwin's time, but has since been refuted. Horticulturalists and animal breeders, like Thomas Knight, believed that conditions of domestication or cultivation (such as an excess of food or shelter from harsh conditions) boost the variability of the offspring. And so did Darwin. Matthew (1831), however, did not subscribe to this doctrine. He did not explicitly refute it, but what he wrote was not in accord with it either. Concerning his personal experience with planting and growing trees he commented in the footnote that domestic trees vary no more than forest trees:
"In fairness, it may be proper to explain, that the greater part of the trees we have thus cultivated have been of Pyrus, although we commenced the practice with common forest trees—yet the pear and apple vary nothing from the oak and ash in the primary stage of life" (emphasis added, Matthew 1831, p. 215, footnote )
That means, had Darwin read Matthew (1831), he might not have asked this question about the effects of domestic conditions on variability in the first place.

The analytical performance
The scan and the transcript provided by Darwin Online are not very good. Let's take a closer look at a better scan provided by the American Museum of Natural History.

The first thing to notice, here, is that the transcription (by David Kohn) has added a footnote "a" after "forest-trees." What does it say? It says: "aDo forest-trees] ‘No’ added over ‘Do’"
Apparently, we must look closer still!

What we see, now, is that Darwin has overwritten the first word, either "Do" with "No" or vice verse. Here are samples of Darwin's "D" and "N" from other pages in the same notebook as well as the Do/No overwrite at page 3 in large.

Taking the question mark at the end of the sentence as an indication that the original sentence must have been a question, the original first letter must have been a "D" in "Do forest-trees sport much in nursery gardens?" That means, Darwin has overwritten the "D" with an "N" and thus turned a question into an answer. He apparently concluded something about the effect of either out-breeding or manuring in nurseries. So here's an interesting project for an accomplished sleuth in trying to find out what this overwrite signifies.

Thursday, 1 March 2018

Comparing the respective transmutation mechanisms of Patrick Matthew, Charles Darwin and Alfred Wallace

The original article has been published at the Biological Journal of the Linnean Society 123(4): 864-78 (2018): [This link should bring you to the full article as it is a guest entrance, that is, a back-entrance through the paywall.] A pre-print version is available here.

The elaborate acknowledgements
I'd like to take the chance to be more elaborate, here, than in the published paper. David Lloyd was a peer reviewer who waved anonymity. He and two anonymous reviewers helped to improve the paper a lot, especially on Alfred Wallace. A rant about the second reviewer (there were four in total) could follow, but everybody knows what "reviewer no. 2" means. I must praise the gumption of the editor in chief, John Allen, however. When I challenged the one glib and uncomprehending sentence that constituted the 2nd review, he bethought himself and revised his decision from rejection to re-write. Finally, thanks to Alexandra Elbakyan for literature.

[While the enigma of Matthew's education is only mentioned in the introductory paragraphs, a great amount of new information concerning it has been collected by a team (Anne Carroll, Julian Derry, Mike Weale, and I) and I have collated it in a blog piece lest I forget the links and details. In my opinion, this is a fine example of a person (Patrick Matthew from Newbigging—not Gourdiehill) that has for a long time rotten in the archives as a person of no historical significance whatsoever, brought back to life and linked to a question of historical significance.]

After a rash rejection by the Journal of the History of Biology, Mike Weale has, for some time, engaged in a ping-pong game of him commenting on the manuscript and me sending him corrected versions back. I also invited Julian Derry to become co-author around that time, but the plan never panned out for various reasons. Nevertheless, Julian's input via e-mail discussions was as helpful as that of Mike Weale.

The historical significance of Matthew's transmutation mechanism
Despite these important roles of Julian Derry and Mike Weale, the three of us reconstruct Matthew's views differently. (Reconstruction is inevitable for a record as incomplete as Matthew's. It's as if we have a most complete fossil record for Darwin, most of it for Wallace, but only a jaw, and a leg, and a tail for Matthew.) Let me sketch the differences between Weale, Derry and me as aptly as possible. Figuratively speaking, if the theories of Matthew, Darwin, and Wallace were vintage cars, Weale thinks that all three have basically similar machinery under the bonnet. On the contrary, I think that the machinery of all three includes natural selection somehow and leads to species transmutation somehow, but apart from that superficial similarity, they differ significantly. Finally, Derry thinks that Matthew's machinery includes natural selection but is a motor for keeping species fixed. Transmutation, however, lies in the trunk not under the bonnet. It jumps out and gives the car a push-start only after the motor for species fixity suffered a catastrophic break-down.
    I think Matthew's scheme proposed species transmutation with natural selection also being in it, but not as central as in Darwin's mature theory. On the contrary, Matthew's scheme suggests that natural selection works species fixing except after catastrophes have ripped remnant species apart and thrown them into habitats which they did not naturally occupy before the catastrophe. That is, natural selection only ever works (anagenetically) to adapt a lineage to its environment and the catastrophe does the lineage splitting. Natural selection does play some role, here, during the process of species transformation and lineage splitting IMHO (but not in Derry's). Despite these disagreements, both Mike Weale and Julian Derry were very helpful for me (unlike a notorious Patrick-Matthew-troll who immediately resorts to fussilades of ad hominem attacks at the slightest sign of disagreement).

In Darwin's mature theory, natural selection and the principle of divergence were sufficient to effect divergence and speciation in symparty. Darwin (1859, pp. 105) thought that the populations on islands were too small, variants would therefore occur too rarely, and the evolutionary process would therefore be too slow to account for all species.  (They did not know about genetic drift and how it can accelerate evolutionary change in small populations back then). Here is Darwin's reasoning against island biogeographies as the main origins of species:
"If, however, an isolated area be very small, either from being surrounded by barriers, or from having very peculiar physical conditions, the total number of the individuals supported on it will necessarily be very small; and fewness of individuals will greatly retard the production of new species through natural selection, by decreasing the chance of the appearance of favourable variations.
If we turn to nature to test the truth of these remarks, and look at any small isolated area, such as an oceanic island, although the total number of the species inhabiting it, will be found to be small, as we shall see in our chapter on geographical distribution; yet of these species a very large proportion are endemic,—that is, have been produced there, and nowhere else. Hence an oceanic island at first sight seems to have been highly favourable for the production of new species. But we may thus greatly deceive ourselves, for to ascertain whether a small isolated area, or a large open area like a continent, has been most favourable for the production of new organic forms, we ought to make the comparison within equal times; and this we are incapable of doing.
Although I do not doubt that isolation is of considerable importance in the production of new species, on the whole I am inclined to believe that largeness of area is of more importance, more especially in the production of species, which will prove capable of enduring for a long period, and of spreading widely. Throughout a great and open area, not only will there be a better chance of favourable variations arising from the large number of individuals of the same species [page break]
there supported, but the conditions of life are infinitely complex from the large number of already existing species; and if some of these many species become modified and improved, others will have to be improved in a corresponding degree or they will be exterminated. Each new form, also, as soon as it has been much improved, will be able to spread over the open and continuous area, and will thus come into competition with many others. Hence more new places will be formed, and the competition to fill them will be more severe, on a large than on a small and isolated area. Moreover, great areas, though now continuous, owing to oscillations of level, will often have recently existed in a broken condition, so that the good effects of isolation will generally, to a certain extent, have concurred. Finally, I conclude that, although small isolated areas probably have been in some respects highly favourable for the production of new species, yet that the course of modification will generally have been more rapid on large areas; and what is more important, that the new forms produced on large areas, which already have been victorious over many competitors, will be those that will spread most widely, will give rise to most new varieties and species, and will thus play an important part in the changing history of the organic world." Darwin (1859, p. 105f)

     However, if evolution through natural selection was defined as a mechanism that includes the principle of divergence as an active part, then Wallace does not have it either nor do modern evolutionary biologists, who mostly subscribe to a model of allopatric speciation. Such a position would distinguish Darwin's theory to the extent of isolating it from modern evolutionary biology. Therefore, it seems better to say that Matthew's scheme proposed species transmutation with natural selection in a lateral function, Wallace's scheme proposed species transmutation through natural selection in a biogeographic island setting, and Darwin's mature scheme proposed species transmutation through natural selection plus the principle of divergence (biogeography and isolation being facilitating factors).

A comparison of the evolutionary mechanisms of Patrick Matthew, Charles Darwin, and Alfred Wallace highlights their differences. In Matthew’s scheme, catastrophes initiate periods of radiation and speciation until a fully stocked environment gets into stasis. Catastrophes first needed to exterminate competing species before the survivors could radiate into free niches and diversify into new species. In Darwin's early theory conditions of life, such as prevail under domestication, first need to increase the variability of a species, before natural selection can transform it. In Darwin's mature theory competition replaced conditions as the main drive behind evolutionary change and sympatric speciation becomes possible. Wallace’s theory differed from both Matthew’s and Darwin’s. Interspecific competition was neither a brake halting transmutation (as in Matthew’s) nor intraspecific competition a sufficient drive for it. While each theory integrated natural selection with variability, competition and changed conditions in distinct ways, each allowed for species transmutation somehow. The result was similar (transmutation), but the mechanisms yielding that result (the integration of natural selection with variability, competition, change in conditions) differed significantly.