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In Darwin’s Shadow: Excerpt

Epilogue: Psychobiography and the Science of History

In Darwin’s Shadow is the gripping story of the heretical British naturalist Alfred Russel Wallace who co-discovered natural selection independently of his more well-known contemporary Charles Darwin. Utilizing a number of never-before-used archival sources that brings to bear new interpretations of this most fascinating scientist, best-selling author Michael Shermer applies his training in both the history of science and psychology to reveal the life, science, and personality of Wallace to unravel the mystery of his scientific, quasi-scientific, and non-scientific ideas. Shermer’s unique approach goes beyond narrative storytelling to analyze the science, culture, and ideas that lie beneath the life story, in what is a path-breaking approach to biography. Shermer presents the two major points of intersection and conflict between Wallace and Darwin, one so radical that Darwin accused his younger colleague of intellectual murder!

Chapter 5 — A Gentlemanly Arrangement:
Alfred Russel Wallace, Charles Darwin & the Scientific Priority Dispute

When the 19th-century British naturalist, Alfred Russel Wallace, returned home\ from eight years in the jungles of the Malay Archipeligo in the Spring of 1861, he boasted an almost unbelievable collection of 125,660 total specimens, including 310 mammals, 100 reptiles, 8,050 birds, 7,500 shells, 13,100 butterflies, 83,200 beetles, and 13,400 “other insects.” In addition to collecting, Wallace also wanted to put the seemingly infinite variety of nature’s pieces together into a puzzle so that as a historical scientist he could solve the riddle of what his friend and colleague, Charles Darwin, called the “mystery of mysteries” — the origin of species. It was this combination of broad observational scope and penetrating theoretical depth that set Wallace apart from most of his contemporaries and led him to his discovery about the mutable nature of species and the interdependency of organisms in their geographical location. Wallace was demonstrating the practice of science at its best — the blending of process and product into an art form described by Sir Peter Medawar as “the art of making difficult problems soluble by devising means of getting at them” (1984, pp. 2–3).

The art of the soluble. Our understanding of how Darwin and Wallace discovered the mechanism and process of evolution helps us see that the fitful and sometimes quirky progress of science is more explicable as an interaction of steady historical trends punctuated by serendipitous flashes of insight or discovery. As Thomas Kuhn and others have demonstrated, the history of science is not an asymptotic curve of stately progress toward Truth and the unfolding of the shroud covering Reality. Rather, it consists of long periods of paradigmatic status quo, occasionally interrupted by shifts in the shared cognitive structure, resulting in a new and different way of interpreting nature. The particulars of a specific historical event, however, do not always fit Kuhn’s universal concept, as each is unique to itself. Because of the contingent nature of history, no two paradigms or paradigm shifts are ever the same. The history of the independent discovery of natural selection by Charles Darwin and Alfred Wallace, and the resolution of the ensuing priority dispute, provides a case study in the scientific process and the interactive nature of contingency and necessity in history.

A Question of Priority

The matter of who was “first” in the discovery and description of natural selection has recently been “stirred up,” and has essentially remained unresolved for two reasons:

  1. missing evidence in the form of the letter and essay from Wallace to Darwin in the spring of 1858 makes empirical resolution impossible;
  2. the generally pugnacious zero-sum game (win-lose) model of priority held by scientific communities and the patent/copyright office, does not recognize the interactive and social nature of the scientific process.

It should be noted that Wallace’s “co-discoverer” status with Darwin is generally accepted by most biologists and historians (e.g, Mayr, 1982; Beddall, 1988). The question some raise, however, is this: should Wallace be given even more credit? Barbara Bedall (1968, 1988) and John Langdon Brooks (1984) have provided the best scholarly treatments of the priority question, while Arnold Brackman’s A Delicate Arrangement (1980) is an emotional appeal for Wallace’s case. Brackman suggests that Charles Lyell and Joseph Hooker, with Darwin’s knowledge (but not his direction), conspired to negate Wallace’s credit, while simultaneously boosting Darwin’s.

As briefly outlined in Part I of this essay, when Wallace was in the Malay Archipelago in March, 1858, he had a sudden realization that “there is a general principle in nature which will cause many varieties to survive the parent species, and to give rise to successive variations, departing further and further from the original type.” These departations eventually become new species, his theory of which gave Wallace a mechanism to solve Darwin’s “mystery of mysteries.” He jotted down his theory in an essay entitled “On the Tendency of Varieties to Depart Indefinitely from the Original Type,” and “sent it by the next post to Mr. Darwin,” apparently on March 9. When Darwin received the package (assumed to be on June 18) he expressed his shock to his friend, the great geologist Charles Lyell (in a letter dated the “18th”): “I never saw a more striking coincidence. If Wallace had my manuscript sketch written out in 1842, he could not have made a better short extract! Even his terms now stand as heads of my chapters.” On July 1, 1858, Darwin and Wallace were awarded co-credit for the discovery at the Linnean Society meeting, though Darwin’s name was listed first because of his having worked on the problem for so much longer.

Both Brooks and Brackman claim, based largely on missing evidence and therefore inference from tangential data, that Darwin received Wallace’s letter and essay earlier than the announced June 18 date. Brackman claims and Brooks suggests that Darwin might have fleshed out the missing pieces of his theory from Wallace’s essay, then feigned distress at Wallace’s parallel theory. Motive, of course, is virtually impossible to prove, but the chronological sequence can be analyzed. The strongest associative evidence is another letter sent by Wallace to Frederick Bates, the younger brother of his naturalist colleague and Amazon companion Henry Walter Bates. The letter is assumed to have beeen sent the same day, March 9, and appeared in London on June 3. The clearly-dated, post-marked letter (no envelope — the letter itself was addressed and post-marked), is in possession of the grandson Alfred John Russel Wallace. In the letter Wallace tells Bates of the seemingly incoherent diversity of insect coloration in the Malay, and notes that “such facts as these puzzled me for a long time, but I have lately worked out a theory which accounts for them naturally” (AJRW, l. 40). That theory, “lately worked out,” was the essay sent to Darwin, the original autograph manuscript and cover letter of which is missing.

A Delicate Arrangement or a Gentlemanly One?

Thomas Huxley’s son, Leonard, called the Wallace situation “a delicate arrangement.” Arnold Brackman argues that since Darwin had been working on his theory for 20 years, and that because he was an established scientist with a recognized role within the scientific community, when this young amateur naturalist appeared with a theory to match or better Darwin’s, Lyell and Hooker determined that if Darwin was not given the lion’s share of the credit, no one would accept Wallace’s theory. The “delicate arrangement” was, according to Brackman, as follows: Wallace was not part of the traditional scientific community in England (owing to his working-class background and lack of formal university training), and since he spent most of his professional life (thus far) outside the country, it was necessary for there to be an organized “conspiracy” by the intellectual circle surrounding Darwin to lessen the value of Wallace’s contribution. Wallace, with a working-class mentality, deferred to his superior (Brackman, pp. 1–96). Brackman concludes:

No matter how heinous is a conspiracy, the participants — especially if it is successful — are apt to develop a plausible rationale for gilding it. “I do not think that Wallace can think my conduct unfair in allowing you and Hooker to do whatever you thought fair,” Darwin wrote to Lyell. The message was clear: Lyell and Hooker bore historical responsibility for the cover-up. Darwin did not “allow” Lyell and Hooker to act independently. In this instance, he appeared helpless, informed powerful friends of his impending doom, pointed subtly in the direction of a solution, let his friends solve the problem by dubious means, and went along with the solution — claiming it, of course, as theirs (p. 78).

There is no doubt that the Darwin-Wallace situation was a “delicate” one. Any time there is a question of scientific priority the situation could be nothing but delicate. But the respect and deference shown by both Darwin and Wallace toward each other provides us with evidence that though the arrangement may have been a delicate one, it was worked out between the two men in a gentlemanly way. In a letter dated January 25, 1859, for example, Darwin wrote to Wallace:

I owe indirectly much to you and them [Lyell and Hooker] for I almost think that Lyell would have proved right and I should never have completed my larger work, for I have found my abstract hard enough with more poor health. Everyone whom I have seen has thought your paper very well written and interesting. It puts my extracts (written in 1839, now just twenty years ago!), which I say in apology were never for an instant for publication, in the shade (Marchant, pp. 111–112).

Wallace was equally generous in his accreditation to Darwin, as this passage from a letter written on May 29, 1864, shows:

You are always so ready to appreciate what others do and especially to over-estimate my desultory efforts, that I can not be surprised at your very kind and flattering remarks on my paper. I am glad however that you have made a few critical observations and am only sorry you were not well enough to make more, as that enables me to say a few words in explanation (pp. 128–129).

Darwin’s Surprise or Chagrin?

What is surprising, if anything, is Darwin’s apparent surprise at the receipt of Wallace’s essay. A clipping of a letter from Wallace to Darwin dated (in Darwin’s hand) September 27, 1857, clearly shows that Wallace was continuing work on the problem of the origin of species that he had begun with the publication of his 1855 paper (“On the Law which has Regulated the Introduction of New Species”), for which he voices to Darwin his disappointment in a lack of response: “[cut off] … of May last, that my views on the order of succession of species were in accordance with your own, for I had begun to be a little disappointed that my paper had neither excited discussion nor even elicited opposition. The mere statement and illustration of the theory in that paper is of course but preliminary to an attempt at a detailed proof of it, the plan of which I have arranged, and in part written, but which of course requires much [cut off] and collections, a labor which I look [cut off]” (DAR 47:145).

It seems clear from this passage, albeit truncated through deliberate cutting, that the only thing Darwin could have been surprised about was how quickly Wallace completed a “detailed proof” of the theory that did, in fact, parallel Darwin’s and result in the 1858 essay sent to Down in the spring. (The deliberate cutting up of letters, manuscripts, notes, and various forms of correspondence by Darwin was his regular, rather disjointed method of organizing his major publishing projects. When one requests the original manuscript for the Descent of Man at the Cambridge Library, for example, one receives a box filled with clippings, snippets, notes cribbed on the backs of envelopes, and the like. Darwin collected these and labeled them as to their source, date of receipt, the chapter into which they would fit, etc. The above letter clipping from Wallace to Darwin, and labeled by Darwin, fits this pattern.) But it leaves one to wonder what plan Wallace was working on that he had already written part of, since the 1858 essay was composed in the course of two nights in late February, a full five months after this letter to Darwin. Did his feverish discovery overturn the ideas he was developing in this 1857 plan? If not, what happened to this manuscript? If so, then why did Wallace not expand the 1858 essay into a longer book-length manuscript? One possible answer may be found in a letter written between these two dates, to Bates on January 4, 1858, in which Wallace discusses what appears to be this same “plan” or “work” (AJRW, l. 41):

To persons who have not thought much on the subject I fear my paper on the succession of species [the Sarawak Law of 1855] will not appear so clear as it does to you. That paper is, of course, only the announcement of the theory, not its development. I have prepared the plan & written portions of an extensive work embracing the subject in all its bearings & endeavouring to prove what in the paper I have only indicated. I have been much gratified by a letter from Darwin, in which he says that he agrees with “almost every word” of my paper. He is now preparing for publication his great work on Species & Varieties, for which he has been collecting information 20 years. He may save me the trouble of writing the 2nd part of my hypothesis, by proving that there is no difference in nature between the origin of species & varieties, or he may give me trouble by arriving at another conclusion, but at all events his facts will be given for me to work upon. Your collections and my own will furnish most valuable material to illustrate & prove the universal applicability of the hypothesis.

Here a plausible scenario presents itself. Wallace, after years of collecting and observing, formed a hypothesis — “On the Law which has regulated the Introduction of New Species” (the 1855 “Sarawak Law”). Lacking further supportive evidence for a mechanism to drive evolutionary change, coupled to the fact that he perceived his paper to be largely ignored by the scientific community, Wallace continued about his business of naturalist in relative anonymity, but never abandoned his ultimate quest to understand the origin of species. He knew that Darwin had been working on the problem for 20 years and was currently writing his “big species book” (originally entitled Natural Selection, later changed to Origin of Species). Wallace, in no position (either logistically in his travels, or scientifically in his research) to complete a work thorough enough to be received positively, decided to sit back and wait to see what Darwin would produce. If Darwin was successful (that is, if Wallace agreed with his arguments), then Wallace would have no need to repeat what had already been done (“He may save me the trouble of writing the second part of my hypothesis”). If Darwin was not successful (“he may give me trouble by arriving at another conclusion”), then Wallace could respond accordingly with his own theory and data. It seems clear that Darwin’s Origin satisfied the first set of criteria, and Wallace never did write his own “big species book” until he published Darwinism in 1889, the title of which indicates his own leanings on the priority question.

The September 27, 1857, clipping indicates that, if anything, Darwin should have been a little chagrined instead of surprised, having already been warned by Lyell that he should publish. Darwin’s response to this portent indicates his dislike of publishing solely for the sake of priority, yet stating his own fear of being forestalled. On May 3, 1856, Darwin wrote to Lyell: “I rather hate the idea of writing for priority, yet I certainly should be vexed if anyone were to publish my doctrine before me” (F. Darwin, 1887, p. 68). His hand forced by Wallace in 1858, Darwin found a solution to his apparent dilemma (i.e., publish for priority sake only, or be completely scooped) by writing a book that was midway between a brief sketch and a magnum opus — The Origin of Species.

What We Shall Never Know

With the primary evidence missing in this historical mystery, we can only speculate on what really happened at Down. The extreme interpretation of a conspiratorial cover-up is not supported by the evidence. If Darwin were going to rig (or allow to be rigged) the editorial presentation of the papers to award him priority; or worse, plagiarize from Wallace certain needed ideas (such as the divergence of species, as Brooks suggests), why announce the arrival of Wallace’s essay and submit it for publication in the first place? Why not either just take what was needed, or, if Wallace’s essay added nothing new to the theory, just destroy the essay and letter and blame the loss on an inefficient postal service, or the mishandling of his mail at Down, or whatever? If one is going to accuse Darwin of such devious finagling as delicate arrangements or plagiarization, then would not the same guileful and scheming personality think of complete elimination of Wallace’s essay as a successful strategy?

There is no question that much confusion surrounds the critical period of the spring and summer of 1858, and Brooks’s epilogue, “What Really happened at Down House?,” draws the pieces together and he wisely concludes: “The simple answer is that no one knows” (p. 258). But then Brooks proceeds “to sketch an alternative reconstruction” in which he concludes that Darwin’s letter to Lyell, dated “Down, 18th” and assumed by most to be June 18, was “probably written May 18, 1858” but “it is my view, however, that Darwin did not mail the letter then. Probably after much soul-searching, he restudied Wallace’s Ternate manuscript and, with recourse again to Wallace’s 1855 paper, wrote the material on [divergence] and inserted it into the text of his chapter on ‘Natural Selection’” (pp. 261–263).

Brooks’s subsequent analysis of various manuscripts and letters after that incident, then, are all based on the assumption that Darwin received Wallace’s letter and essay on May 18. But the analysis is inconsistent. Earlier in the book Brooks says that “the evidence indicates that Darwin must have received Wallace’s manuscript on either of two dates in May. Receipt on May 18 would leave 25 days for completion of those folios [on divergence] by June 12 [the date Darwin noted his thoughts on divergence in the manuscript]; May 28–29 would leave scarcely two weeks. But it must be conceded that desperation will make the pen move quickly” (p. 257). Conspiratorial historicism makes the pen move too quickly. First Brooks gives us the dates of May 18 or May 28–29 for the arrival of Wallace’s letter and essay, then he tells us he thinks the “Down 18th” letter to Lyell announcing the arrival of Wallace’s letter and essay was actually written on May 18, thus completely negating the May 28–29 option. But even worse, Brooks assumes the Wallace-Bates letter that arrived in London (and post-marked) June 3, was in the same batch as the Wallace-Darwin letter and essay. This is not a historical fact, but an inference, but even if true, this makes both May dates impossible, and, assuming Darwin did not lie in the letter to Lyell about the arrival of the Wallace material on the same day (the 18th), then the arrival date must be June, not May.

H. L. McKinney (1972) has consistency problems as well. He first concludes that the mail from Malaya to London averaged 10 weeks in transition, and thus “10 weeks from 9 March, when the communication was mailed, is precisely 18 May, one month before Darwin acknowledged receiving it.” McKinney then points to the Wallace-Bates June 3 letter and concludes: “It is only reasonable to assume that Wallace’s communication to Darwin arrived at the same time and was delivered to Darwin at Down House on 3 June 1858, the same day Bates’s letter arrived in Leicester.” To account for the delay from May 18 to June 3, McKinney explains: “Knowing the numerous delays in such matters, we should perhaps allow some leeway, although one month appears to be an excessive allowance.“ (p. 139). Fine, but then why no “delays” and “leeway” for the Bates letter? And what was Darwin doing with Wallace’s manuscript in that time? McKinney wisely ends his discussion “with a series of question marks,” but then hints that Darwin might have been filling in the gaps “on divergence in his long version of the Origin; he finished that section on 12 June” (p. 141).

So which is it? Either the Bates letter is damning evidence, or it is not. Brooks and McKinney cannot have it both ways. They cannot use the Wallace-Bates letter as evidence that the Wallace-Darwin materials arrived on June 3, and then have Darwin writing Lyell announcing same on May 18 (as Brooks does); or that the Darwin letter was delayed while the Bates letter was not (in McKinney’s case). Either way, to accuse one of the greatest scientists in history of committing one of the most heinous crimes in science on one of the most important aspects of his theory, one better have compelling evidence. Modern skeptics are fond of saying that extraordinary claims require extraordinary evidence. These claims against Darwin are truly extraordinary but the evidence is not.

In addition, Darwin’s contribution to the joint Linnean Society papers did not include materials developed in 1858; rather, he included a letter to the American scientist Asa Gray, written in September, 1857. If Darwin had cribbed divergence from Wallace, they why submit this older version? And why was divergence listed in the table of contents for Natural Selection in March, 1857? And how could he have explained divergence to Asa Gray, almost a year before the Wallace essay?

In 1858 Darwin was knee deep in producing a massive, multi-volume work entitled Natural Selection. He planned on taking several more years to complete it, and without outside pressure to publish he was in no hurry. He had seen the fallout of other theorists who had published prematurely, and he was not about to be subjected to that kind of criticism. But Wallace’s 1858 letter and essay, whether they arrived in May or June, changed all that. Darwin was forced to publish a “shorter” (490-page) book the following year — The Origin of Species. Unless the Wallace letter miraculously turns up, we shall never know what “really happened.” The most logical conclusion is that under the circumstances the delicate arrangement was handled in the most gentlemanly way possible.

The Zero-Sum Model of Scientific Priority

In 1947, the mathematician John von Neumann published Theory of Games and Economic Behavior, in which he described the zero-sum model where the gain of one participant means the loss of the other, and the more one gains the more the other loses. If I win six games of tennis, my opponent must lose six games, and thus they sum to zero (6+-6 = 0). This antagonistic, win-lose model completely misses the interdependent, sometimes cooperative, and always social nature of the scientific process. Wallace’s priority credit and recognition for scientific achievement can and should be significantly enhanced without taking anything away from Darwin. Richard Dawkins, in The Selfish Gene (1976), describes these symbiotic relationships — called by Robert Trivers “reciprocal altruism” (1971) — as common throughout plant and animal relationships, including human interactions.

To describe these reciprocal relationships, Dawkins adopts the Prisoner’s Dilemma (PD) model developed by Axelrod and Hamilton (1981), a game in which two prisoner’s have several options: they can cooperate with each other and get light sentence terms; or if one defects while the other cooperates, the defector is freed while the cooperator gets an even longer jail sentence; or both can defect, in which case both receive longer jail stays. When this game is iterated, or repeated, the majority of responses produced are cooperative, as this strategy leads, in the long run, to “the greatest good for the greatest number.” In the short run, that is, in a noniterated or one-trial game, defection is the rule. But over time consistent defectors lose out. Dawkins demonstrates that for animals and humans, those who adopted the zero-sum model were losers.

The zero-sum model is at the heart of most disputes of scientific priority, because it assumes that the only way one scientist can profit is through the loss of another scientist. Clearly Newton and Newtonian scholars saw Newton’s gain in the priority of the invention of the calculus to be Leibniz’s loss, and vice versa, leading to centuries of debate and disagreement. Likewise, many authors seem to perceive Darwin’s gain as Wallace’s loss, and Wallace’s gain as Darwin’s loss. Because of this it becomes difficult in most of these debates to tease out the facts from the emotion, the information from the rhetoric. This disputative posturing on both sides wedges historians into a defensive stance that compels an attack-or-be-attacked response. Thus, the antagonism between scholars and historians in both camps could be attenuated by the rejection of the zero-sum model. Darwin, and especially Wallace, clearly rejected the zero-sum model, as both recognized the gain to be had through cooperative interaction. Consider this exchange of letters between the two men. The first, an April 6, 1859, letter from Darwin, reveals a man paying the highest respect for a fellow winner in this game of scientific cooperation (Marchant, pp. 113, 131):

You cannot tell how I admire your spirit, in the manner in which you have taken all that was done about establishing our papers. I had actually written a letter to you, stating that I could not publish anything before you had published. I had not sent that letter to the post when I received one from Lyell and Hooker, urging me to send some ms. to them, and allow them to act as they thought fair and honourably to both of us. I did so.

Wallace responded with an equally generous dose of recognition in this passage from a May 29, 1864 letter:

As to the theory of Natural Selection itself, I shall always maintain it to be actually yours and yours only. You had worked it out in details I had never thought of, years before I had a ray of light on the subject, and my paper would never have convinced anybody or been noticed as more than an ingenious speculation, whereas your book has revolutionized the study of Natural History, and carried away captive the best men of the present age.

(It is interesting to note that not only Alfred Wallace, but his grandson John, were and are satisfied with the historical priority outcome. After a lengthy conversation on this question, John Wallace told me: “I can’t understand what all the fuss is about. Grandfather was satisfied with the arrangement, none of us desire to call it ‘Wallace’s theory of natural selection,’ but many of the Darwin people seem defensive about it.” There is no doubt about the latter, but it is understandable because the aforementioned Wallace defenders have embraced the zero-sum model, causing them to give more credit to Wallace while simultaneously taking credit away from Darwin. Darwin scholars, of course, adopt the zero-sum model in defense, as they feel Wallace’s gain is Darwin’s loss.)

The Sum-Plus Model of Scientific Priority

A sum-plus model — the gain of one person is the gain of another — recognizes the contingent, cooperative, and interdependent nature of scientific discovery. Both Darwin and Wallace profited by the profit of the other. Both were winners in the game to understand the origin of species. An 1870 letter of “reflection” from Darwin to Wallace shows the special win-win nature of their relationship: “I hope it is a satisfaction to you to reflect — and very few things in my life have been more satisfactory to me — that we have never felt any jealousy towards each other, though in one sense rivals.” In the most gentlemanly fashion Wallace always politely addressed Darwin in virtually every letter written, and Darwin nearly always responded in kind. “I was much pleased to receive your note this morning,” reads a typical letter opening from Wallace to Darwin. “Hoping your health is now quite restored,” “I sincerely trust that your little boy is by this time convalescent,” and so on (DAR:106, 107). Darwin and Wallace used each other and each other’s ideas to their mutual benefit, and the world of science is better off for it.

One of the other problems with the sum-zero model is an assumption of identity between ideas made in priority disputes. This assumption of identical ideas leads to the conclusion that only one individual can be first in discovery. But a law of nature is really the product of both discovery and description of a phenomenon. Two individuals may make the same discovery, but they may not make the same description. This is the case with Darwin and Wallace, where their theories of evolution by means of natural selection are similar and complimentary, but not identical. Through their numerous intellectual exchanges in letters, papers, and books, they stimulated one another with in both knowledge and theory, with a net gain profit for both, making them genuinely codiscoverers.

The historical record has read differently, however, beginning with the ranking of the joint papers read at the July 1, 1858, Linnean Society meeting which placed Darwin’s 1844 extract and his 1857 Asa Gray letter ahead of Wallace’s 1858 essay. If considered by dates of ideas alone, then the ranking is chronologically correct. (It is also alpabetically correct, which was how the names were listed.) But, in fact, what has happened is that Darwin has become a household name and Wallace all but forgotten. This historical reality, of course, was not caused by the ranking of their names at this meeting. In actual fact, according to the Linnean Society President, Thomas Bell, in a reflection of the year’s activities, nothing of significance happened in 1858: “The year which has passed … has not, indeed, been marked by any of those striking discoveries which at once revolutionize, so to speak, the department of science on which they bear” (Bell, 1859, pp. viii–ix). Obviously Bell and his colleagues did not grasp the significance of the theory of natural selection at its time of presentation. Darwin’s fame and importance accrued over many decades of sound scientific work, not through a “delicate arrangement” and clandestine priority ranking of his name over Wallace’s. Besides, other than later noting that his paper “was printed without my knowledge, and of course without any correction of proofs,” Wallace was certainly delighted to finally gain the recognition of the scientific community he had desired for so many years, as he indicated to his mother on October 6, 1858, while still in the Malay Archipelago: “I have received letters from Mr. Darwin and Dr. Hooker, two of the most eminent naturalists in England, which has highly gratified me. I sent Mr. Darwin an essay on a subject on which he is now writing a great work. He showed it to Dr. Hooker and Sir C. Lyell, who thought so highly of it that they immediately read it before the Linnean Society. This assures me the acquaintance and assistance of these eminent men on my return home” (Marchant, p. 57).

Consider Wallace’s position at this time. He was a relatively unknown 35-year-old whose only theoretical work — the 1855 Sarawak Law paper — was largely ignored (or, at least, so he thought). He had been away from England and the center of scientific activity already four years, and was, by all rights, really still cutting his teeth on such weighty theoretical matters. Darwin, by contrast, was 49 years old, fairly well-known in scientific circles, had already published numerous important scientific articles, and had shared his theoretical ideas with the most important scientists in England. Wallace did not feel the loser because he was not. An essay written in two nights, sent to the right place at the right time, put him in the scientific inner circle and into the historical record — his name next to Darwin’s — forever. Anyone who thinks that this was Wallace’s loss should reconsider the circumstances in light of the sum-plus model of scientific priority. The gain of Darwin was the gain of Wallace, not the loss.

Consider also, Wallace’s reception and review of Darwin’s Origin of Species. In only seven months, he told his boyhood friend George Silk on September 1, 1860, “I have read it [the Origin] through 5 or 6 times & each time with increasing admiration. It is the ‘Principia’ of Natural History. It will live as long as the ‘Principia’ of Newton.” Silk was not someone Wallace needed to impress with false praise, as he continued the comparison: “The most intricate effects of the law of gravitation, the mutual disturbances of all the bodies of the solar system are simplicity itself, compared with the intricate relations & complicated struggle which has determined what forms of life shall exist & in what proportions. Mr. Darwin has given the world a new science & his name should in my opinion stand above that of every philosopher of ancient or modern times. The force of admiration can no further go!!!” (AJRW, l. 46).

The Sum-Plus Model and The Nature of History

Wallace, perhaps better than most, understood the sum-plus model of scientific interaction, and provides us with a brilliant example of this interpretation in an article entitled “The Origin of the Theory of Natural Selection,” published in The Popular Science Monthly, as a reply to his being honored with the Darwin-Wallace medal of the Linnean Society of London on the 50th anniversary of the July 1, 1858 joint reading of the papers. The 1908 celebration rekindled interest in reconstructing the events that led to the theory of natural selection, and in the popular media in particular, there was much historical confusion. It had become apparent to Wallace that there was much misunderstanding of what actually happened in the years leading up to 1858. An analysis of his article on this subject not only supports the sum-plus model, it offers us insight into the independent and yet interdependent nature of scientific progress in particular, and historical change in general.

In this article we see Wallace’s generosity in offering more of the share of the credit to Darwin (whom he refers to as “my honored friend and teacher”), while at the same time firmly reestablishing what he did and did not do. The paper also contains a certain amount of the obligatory modesty that is usually elicited when one is being so honored, such as when Wallace states that the share of the credit should be allocated “proportional to the time we had each bestowed upon it … that is to say, as twenty years is to one week” (RES, p. 397). Well, Wallace did discover and describe natural selection all in the course of a week in late February, 1858, but his four years in the Amazonian tropical rain forest and another eight in the Malay Archipelago hardly represents one week to Darwin’s twenty years. It is true, however, that had Darwin published, “after ten years’ — fifteen years’ — or even eighteen years’” instead of the 20 following the opening of his notebook in 1838, Wallace “should have had no part in it whatever, and he would have been recognized as the sole and undisputed discoverer of ‘natural selection’” (p. 397). The fact is, however, Darwin waited 20 years, and would have likely waited considerably longer had Wallace not played the role of the intellectual trigger to set off Darwin’s productive spark.

In addition, to the modern historian interested in the relative historical role of contingency (a conjuncture of events occurring without design) and necessity (constraining circumstances compelling a certain course of action), it is interesting to note Wallace’s recognition of the role of both sets of historical forces in the development of scientific discoveries. For example, after first clarifying that he and Darwin independently, not simultaneously, discovered natural selection (“the idea occurred to Darwin in October, 1838, nearly twenty years earlier than to myself in February, 1858,”), Wallace recognizes the role of contingency in scientific discovery, when he notes: “It was really a singular piece of good luck that gave to me any share whatever in the discovery” (pp. 396–397). He then turns to an analysis that shows how a number of contingencies in the lives of both men led to the necessary discovery of natural selection: “we find a curious series of correspondences, both in mind and in environment, which led Darwin and myself … to reach identically the same theory,” including (pp. 398–400, enumeration added):

  1. Being “ardent beetle-hunters, [a] group of organisms that so impresses the collector by the almost infinite number of its specific forms, the endless modifications of structure, shape, color and surface-markings that distinguish them from each others, and their innumerable adaptations to diverse environments.”
  2. Having “an intense interest in the mere variety of living things … which are soon found to differ in several distinct characteristics.”
  3. A “superficial and almost child-like interest in the outward forms of living things, which, though often despised as unscientific, happened to be the only one which would lead us towards a solution of the problem of species.”
  4. Both collectors “were of a speculative turn of mind [and] constantly led to think upon the ‘why’ and the ‘how’ of all this wonderful variety in nature.”
  5. “Then, a little later (and with both of us almost accidentally) we became travellers, collectors and observers, in some of the richest and most interesting portions of the earth” (Darwin’s five-year global circumnavigation and Wallace’s four years in the Amazon and eight in the Malay Archipelago). “Thence-forward our interest in the great mystery of how species came into existence was intensified.”
  6. Both men on their voyages and in their home lives enjoyed “a large amount of solitude … which, at the most impressionable period of our lives, gave us ample time for reflection on the phenomena we were daily observing.”
  7. Both men carefully read Lyell’s Principles of Geology and Malthus’ Principles of Population, the latter “at the critical period when our minds were freshly stored with a considerable body of personal observation and reflection bearing upon the problem to be solved,” that acted on both like “that of friction upon the specially-prepared match, producing that flash of insight which led us immediately to the simple but universal law of the ‘survival of the fittest.’”

All of these contingencies created necessities (what Wallace calls “the combination of certain mental faculties and external conditions”) that drove Darwin and Wallace down parallel paths that became cut ever deeper until they finally crossed in the spring of 1858. This historical tension between what happens by chance and what must be — the contingent and the necessary — for an 85-year old Wallace reflecting back on a life of science, explains why it was Darwin and himself who finished first and “a very bad second,” in the “truly Olympian race” to discover the mechanism of evolutionary change; and why it was not the “philosophical biologists, from Buffon and Erasmus Darwin to Richard Owen and Robert Chambers.” For Wallace, the explanation is simple. These “great biological thinkers and workers” were on different paths at different times that made it impossible for them to “hit upon what is really so very simple a solution of the great problem.” An adequate explanation of a historical development requires a healthy balance of the internal and the external, individual thought and collective culture, or “the combination of certain mental faculties and external conditions that led Darwin and myself to an identical conception” (p. 399).

Finally, Wallace applies his model to the large picture of the development of ideas in general, and comes to the conclusion that “no one deserves either praise or blame for the ideas that come to him, but only for the actions resulting therefrom.” Wallace, of course, is not suggesting that great ideas come from “on high” or any other metaphysical source; rather, the vagaries and nuances of our life and thoughts leads us down certain paths toward conclusions that can only be reached by way of that particular road. Wallace and Darwin shared nearly parallel paths for a time (which later diverged on other issues), and Wallace acknowledges the role of such historical contingencies and necessities in the larger scale of the discovery of scientific ideas: “They come to us — we hardly know how or whence, and once they have got possession of us we can not reject or change them at will.” Wallace also addresses the even larger role of human freedom within historical trends by explaining that it is not the development of ideas but in the “actions which result from our ideas,” that individuals have the most say in their historical context. And here we catch a glimpse of Wallace, the hard working, common man who made a most uncommon discovery: “it is only by patient thought and work, that new ideas, if good and true, become adopted and utilized; while, if untrue or if not adequately presented to the world, they are rejected or forgotten” (p. 400). Such is the nature of science and history.

Abbreviations for Primary Source Archives

AJRW: The private collection of Wallace’s two grandsons, Alfred John Russel Wallace, and Richard Russel Wallace. Letters are designated by letter number, corresponding to a catalogue of the collection.

DAR: Darwin Archives, Cambridge University Library.

RES: Royal Entomological Society. No referencing designation.

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