Bully for Brontosaurus

by Stephen Jay Gould

  More generally, I like to apply a somewhat cynical rule of thumb in judging arguments about nature that also have overt social implications: When such claims imbue nature with just those properties that make us feel good or fuel our prejudices, be doubly suspicious. I am especially wary of arguments that find kindness, mutuality, synergism, harmony—the very elements that we strive mightily, and so often unsuccessfully, to put into our own lives—intrinsically in nature. I see no evidence for Teilhard’s noosphere, for Capra’s California style of holism, for Sheldrake’s morphic resonance. Gaia strikes me as a metaphor, not a mechanism. (Metaphors can be liberating and enlightening, but new scientific theories must supply new statements about causality. Gaia, to me, only seems to reformulate, in different terms, the basic conclusions long achieved by classically reductionist arguments of biogeochemical cycling theory.)

  There are no shortcuts to moral insight. Nature is not intrinsically anything that can offer comfort or solace in human terms—if only because our species is such an insignificant latecomer in a world not constructed for us. So much the better. The answers to moral dilemmas are not lying out there, waiting to be discovered. They reside, like the kingdom of God, within us—the most difficult and inaccessible spot for any discovery or consensus.

  23 | Fleeming Jenkin Revisited

  THE EUROPEAN REVOLUTIONS of 1848 played a pivotal role in several famous lives. Karl Marx, exiled from Germany, published the last issue of his Neue Rheinische Zeitung in red, then moved to England, where he constructed Das Kapital in the reading room of the British Museum. The young Richard Wagner, espousing an idealistic socialism that he would later reject with vigor, manned the barricades of Dresden, then fled from Germany to avoid a warrant for his arrest and missed the premiere of Lohengrin.

  Another man, destined for a lesser but secure reputation, experienced a touch of the same excitement. In February 1848, Henry Charles Fleeming Jenkin, a fourteen-year-old boy from Scotland, found himself in Paris surrounded by rebellion. He wrote to a friend in Edinburgh: “Now then, Frank, what do you think of it? I in a revolution and out all day. Just think, what fun!”

  In 1867, the same Fleeming Jenkin would taste revolution of a different kind—this time as a transient participant, not a mere observer. In his much revised fifth edition of the Origin of Species, Charles Darwin made a substantial concession by admitting that favorable variations arising in single individuals could not spread through entire populations. (In retrospect, Darwin need not have conceded. He based his admission on a false view of heredity. In a Mendelian world, unknown to Darwin, such favorable variations can spread—see subsequent discussion in this essay. Nonetheless, Darwin’s concession represents a small but celebrated incident in the history of evolutionary thought.) Darwin wrote:

  I saw…that the preservation in a state of nature of any occasional deviation of structure…would be a rare event; and that, if preserved, it would generally be lost by subsequent intercrossing with ordinary individuals. Nevertheless, until reading an able and valuable article in the North British Review (1867), I did not appreciate how rarely single variations whether slight or strongly marked could be inherited.

  Nearly every book in the history of evolution recounts the tale and refers to the author of this “able and valuable article” as “a Scottish engineer” or, more often, “an obscure Scottish engineer.” The author was Fleeming (pronounced Flemming) Jenkin. Darwin, more explicit and vexed in private letters than in public texts, wrote to Joseph Hooker in 1869: “Fleeming Jenkin has given me much trouble….”—and to Alfred Russel Wallace a few days later: “Fleeming Jenkin’s arguments have convinced me.”

  All evolutionists recognize (and mispronounce by excessive literalism) Fleeming Jenkin as the man who forced an explicit, though unnecessary, concession from Darwin. But we know nothing about him and tend to assume that he rose from general obscurity for one small moment in our sun—a lamentable parochialism on our part.

  My own career has included two fortuitous and peculiar intersections with Fleeming Jenkin—so I decided that I must write a column about him now, before a third encounter elevates coincidence to inescapable pattern. I was an undergraduate at Antioch College from 1958 to 1963. Antioch was (and is) a wonderful school in the finest American tradition of small liberal arts colleges. But it doesn’t boast much in the way of library facilities for scholarship based on original sources. One day in 1960, I was browsing aimlessly through the stacks and found a crumbling run of the North British Review for the mid-nineteenth century. I recognized the name from Darwin’s citation, and my heart skipped a beat as I hoped against hope that the volume for 1867 lay within the series. It did, and I then spent a more anxious minute convinced that I had the wrong title or that the issue for the right month would be missing. It wasn’t. I found Jenkin’s article and rushed to the pre-Xerox wet processor (anachronistically named smellox by a friend of mine several years later, in honor of the unpleasant chemical that left its signature even after drying). I fed dimes into the machine and soon had my precious copy of the original Fleeming Jenkin. What a prize I thought I had. I was sure that I possessed the only copy in the whole world. (Can you imagine what one peek at the Harvard library does to such naivete?) I have carried that copy with me ever since, assigning its properly Xeroxed offspring to classes now and again, but never dreaming that I would write anything about Jenkin.

  Then, last month, I was browsing through a friend’s Victorian literature collection, aimlessly running my eye along the titles of Robert Louis Stevenson’s complete works. I found Treasure Island, Kidnapped, and all the other items of my old “Author’s” card game. But my heart skipped another beat at the next title: Memoir of Fleeming Jenkin. The “obscure Scottish engineer” had achieved sufficient renown (in areas far from my own parish, where he only dabbled, however successfully) to win a full volume from Stevenson’s pen. I kicked myself for sectarian assumptions in the granting of “importance,” vowed to learn more about Jenkin (and to tell my fellow evolutionists), and raided the stacks of Widener Library, where I found several copies of Stevenson’s memoir, amidst (no doubt) a liberal sprinkling of North British Reviews for 1867 (which, smelloci gratia, I didn’t need).

  An interesting man, Fleeming Jenkin—and made all the more appealing by the strength of Stevenson’s prose. Jenkin spent most of his life in Edinburgh, where he campaigned for the improvement of home sanitation, conducted some of Britain’s first experiments with the phonograph, produced and directed amateur theatricals, hated golf (for a Scotsman, I suppose, about as bad as an American who barfs on apple pie), and became the first professor of engineering at the University of Edinburgh. Most important, he was a close friend and colleague of Lord Kelvin and spent most of his career designing and outfitting transoceanic cables with the great physicist.

  Stevenson’s book has a lovely, archaic charm. It describes a moral perfection that cannot be, and belongs to the genre of guiding homilies based on lives of the great. If Jenkin ever gazed at a woman other than his wife, if he ever raised his voice in anger or acted in even momentary pettiness, we are not told. Instead, we get glimpses of a simpler and formal world based on unquestioned certainties. In 1877, Jenkin writes to his absent wife about their son: “Frewen had to come up and sit in my room for company last night and I actually kissed him, a thing that has not occurred for years.” The Captain, Jenkin’s aged father, dies at age eighty-four but achieves solace in his last hour from a false report on the rescue of General “Chinese” Gordon at Khartoum: “He has been waiting with painful interest for news of Gordon and Khartoum; and by great good fortune, a false report reached him that the city was relieved, and the men of Sussex (his old neighbors) had been the first to enter. He sat up in bed and gave three cheers for the Sussex regiment.”

  Stevenson’s memoir contains exactly one line on Jenkin’s 1867 foray into evolutionary theory: “He had begun by this time to write. His paper on Darwin…had the merit of convincing on one point the philosophe
r himself.” Evidently, Jenkin needed neither evolution nor the North British Review to merit Stevenson’s extended attention. I felt a bit ashamed at my own previous parochialism. Do grocers know Thomas Jefferson (or was it Benjamin Franklin) only as the man who invented that thing that gets the cereal boxes down from the top shelf?

  The backward reading of history has cruelly misserved many fine thinkers, Jenkin included. (Professionals refer to this unhappy tactic as “Whiggish history” in dubious memory of those Whig historians who evaluated predecessors exclusively by their adherence to ideals of Whig politics unknown in their own times.)

  Jenkin has suffered because commentators extract from his 1867 article just the one small point that provoked Darwin’s concession—and then analyze his argument in modern terms by pointing out that a twentieth-century Darwin could stick to his Mendelian guns. No modern evolutionary biologist, to my knowledge, has ever considered Jenkin’s treatise as a whole and appreciated its force, despite its errors in modern terms. I shall attempt this rescue but bow first to the constraints of history and discuss the point that secured Jenkin’s slight renown in evolutionary circles.

  Darwin and Jenkin accepted the usual notion of heredity prevalent in their times—a concept called blending inheritance. Under blending inheritance, the offspring of two parents tend to lie halfway between for inherited characters. Jenkin pointed out to Darwin, or so the usual and quite inadequate story goes, that blending inheritance would challenge natural selection because any favorable variant would be swamped out by back-breeding with the predominant parental forms. Jenkin’s own example will make his argument clear. It also serves as a sad reminder of unquestioned racism in Victorian England—and as an indication that, for all our pressing problems, we have improved somewhat during the past century:

  Suppose a white man to have been wrecked on an island inhabited by negroes…. Suppose him to possess the physical strength, energy, and ability of a dominant white race…grant him every advantage which we can conceive a white to possess over the native…. Yet from all these admissions, there does not follow the conclusion that, after a limited or unlimited number of generations, the inhabitants of the island will be white. Our shipwrecked hero would probably become king; he would kill a great many blacks in the struggle for existence; he would have a great many wives and children, while many of his subjects would live and die as bachelors…. In the first generation there will be some dozens of intelligent young mulattoes, much superior in average intelligence to the negroes. We might expect the throne for some generations to be occupied by a more or less yellow king; but can any one believe that the whole island will gradually acquire a white, or even a yellow population…for if a very highly favored white cannot blanch a nation of negroes, it will hardly be contended that a comparatively dull mulatto has a good chance of producing a tawny tribe.

  In other words, by blending inheritance, the offspring of the first generation will be only half white. Most of these mulattoes, since full blacks so greatly predominate (and following prohibitions against incest), will marry full blacks, and their offspring of the second generation will be one-quarter white. By the same argument, the proportion of white blood will dilute to one-eighth in the third generation and soon dwindle to oblivion, despite supposed advantages.

  Darwin, or so the story goes, saw the strength of this argument and retreated in frustrated impotence toward the Lamarckian views that he had previously rejected. Whiggery then comes to the rescue. Inheritance is Mendelian, or “particulate,” not blending (though Darwin died long before the rediscovery of Mendel’s laws in 1900). Traits based on genetic mutations do not dilute; genes that determine such traits are entities or particles that do not degrade by mixing with genes of the other parent in offspring. Indeed, if recessive, a favorable trait will appear in no offspring of the first generation (in matings between the favored mutant and ordinary partners carrying the dominant gene). But the trait does not dilute to oblivion. In the second generation, one-quarter of the offspring between mixed parents will carry two doses of the advantageous recessive gene and will express the favored trait. Any subsequent matings between these double recessives will pass the favored trait to all offspring—and it can spread through the population if concentrated by natural selection. (Skin color and height seem to blend because they are determined by such a large number of particulate genes. The average effect may be a blend, yet the genes remain intact and subject to selection.)

  But this usual story fails when we properly locate Jenkin’s point about blending in the wider context of an argument that pervades the entire essay—and do not simply extract the item as a kernel deserving modern notice while discarding the rest as chaff. As historian Peter J. Vorzimmer notes in his excellent book, Charles Darwin: The Years of Controversy (1970), Jenkin presented his arguments about blending in discussing only one particular kind of variation—single favorable variants substantially different from parental forms.

  Darwin was no fool. He had thought about variation as deeply as any man. His longest book, the two-volume Variation of Animals and Plants Under Domestication (1868), summarizes everything he and almost everyone else knew about the subject. Can we seriously believe that he had never thought about problems that blending posed for natural selection—that he needed a prod from an engineer to recognize the difficulty? As Vorzimmer shows, Darwin had pondered long and hard about problems provoked by blending. Jenkin did not introduce Darwin to this basic problem of inheritance; rather, he made a distinction between the kinds of variation that blending affects, and Darwin welcomed the argument because it reinforced and sharpened one of his favorite views. Darwin did not retreat before Jenkin’s onslaught, but rather felt more secure in his preferred belief—hence his expressed gratitude to Jenkin and hence (I assume) Stevenson’s single comment that Jenkin had convinced “on one point the philosopher himself.” Stevenson, the novelist, understood. We have forgotten.

  The real issue has been lost in a terminology understood in Darwin’s time but no longer familiar. Let us return to Darwin’s letter to Wallace, quoting the passage this time in full: “I always thought individual differences more important than single variations, but now I have come to the conclusion that they are of paramount importance, and in this I believe I agree with you. Fleeming Jenkin’s arguments have convinced me.”

  In Darwin’s time, “individual differences” referred to recurrent variations of small scale, while “single variations” identified unique changes of large scope and import—often called “sports.” Debate had focused on whether small-scale and continuous, or occasional and larger, variations supplied the raw material for evolutionary change. Darwin, the quintessential continuationist of this or any other age, had long preferred recurrent small-scale changes but had continued to flirt (largely by weight of tradition) with larger sports. Now, the simple point of Jenkin’s argument: Note that he speaks of one white man identified (in the racist tradition) as vastly superior to the natives—in other words, a single sport. Jenkin’s famous blending argument refers only to single, marked variations—not to the continuous recurrent variations that Darwin preferred. By accepting Jenkin’s view, Darwin could finally rid himself of a form of variation that he had never favored.

  As for recurrent, small-scale variation (individual differences, in Darwin’s terminology), blending posed no insurmountable problem, and Darwin had resolved the issue in his own mind long before reading Jenkin. A blending variation can still establish itself in a population under two conditions: first, if the favorable variation continues to arise anew so that any dilution by blending can be balanced by reappearances, thus keeping the trait visible to natural selection; second, if individuals bearing the favored trait can recognize each other and mate preferentially—a process known as assortative mating in evolutionary jargon. Assortative mating can arise for several reasons, including aesthetic preference for mates of one’s own appearance and simple isolation of the favored variants from normal individuals. Darwin recogn
ized both recurrent appearance and isolation as the primary reasons for natural selection’s continued power in the face of blending.

  With this background, we can finally exhume the real point and logic of Jenkin’s essay—an issue still very much alive, and discussed (through all his factual errors) in a most interesting and perceptive way by Fleeming Jenkin. Jenkin’s essay is a critique of Darwin’s continuationist perspective—his distinctive claim, still maintained by the evolutionary orthodoxy—that all large-scale phenomena of evolution may be rendered by accumulating, through vast amounts of time, the tiny changes that we observe in modern populations. I call this conventional view the “extrapolationist” argument; I also share Jenkin’s opinion (but for different reasons) that this traditional mode of thinking cannot explain all of evolution. I find it supremely ironic that the one small section of Jenkin’s article not about Darwin’s claim for continuity (his argument that single sports will be swamped by blending) has become the only part that we remember—and, to make matters worse, usually misinterpret. Such, however, is the usual fate of Whig heroes and villains.

  A simple, almost pedantic, précis of Jenkin’s argument should rescue his larger point. Jenkin’s essay proceeds in four parts. The first, on limits of variation, admits that Darwin’s favored style of recurrent, continuous variation does occur and can be manipulated by natural selection to change the average form of a species. But, Jenkin argues, such variations always fiddle in minor ways with parts already present; they cannot construct anything new. Thus, natural selection can make dogs big, small, blocky, or elongate—but cannot change a dog into something else. Jenkin expresses this argument in his powerful metaphor of the “sphere of variation.” Natural selection may move the average form anywhere within the sphere, but not beyond its fixed limits: