The Great Fossil Enigma

by Simon J. Knell

  Müller was rather annoyed at Lindström's dismissal of his work, based as it was on mere opinion. He remained silent until the Pander Society's first major symposium in 1969. By then the Cambrian conodont was beyond dispute. Each year had added a new site. Cambrian conodonts were now known from as far away as Iran, China, and Australia. They remained, however, rare objects in the Upper and Middle Cambrian, and one doubtful report even suggested they might be found in the Lower Cambrian.25

  As Müller almost singlehandedly began the process of giving the family tree its root system, so a rather different argument was taking place in the upper branches. Here Walter Youngquist, a postwar product of the Iowa school who for a short time became the most active worker in conodont stratigraphy, claimed to have discovered conodonts in the matrix of some Triassic cephalopods from Idaho in 1949. He was pretty sure these were Triassic fossils, but he recalled Branson and Mehl's response to an earlier German discovery of Triassic conodonts. In 1941, it had been logical for these two men to consider such fossils as mere contamination, reworked into these younger rocks following the erosion of Permian or other strata. But then, in 1946, American D. B. Eicher of Standard Oil had reported finding Triassic conodonts in Egypt, which Branson and Mehl had also doubted. The wily Youngquist did not want the same fate to befall his finds, so he sent the same slide of specimens to Chalmer Cooper, Eicher, Ellison, Furnish, Hass, and Mehl, along with a list of pertinent questions: Are these conodonts? Have you seen specimens exactly like these in the Paleozoic? Given evolutionary trends, are these compatible with a Triassic age? Do they look like they have been reworked? With Branson out of the picture, both Ellison and Mehl thought these new fossils similar to the German ones Mehl had earlier dismissed. To a man, Youngquist's respondents thought that the fossils conformed to what one might expect Triassic conodonts to be like, and that none appeared to have been reworked. Cooper and Hass also told Youngquist that the National Museum possessed similar fossils, found just fifty miles away from Youngquist's find location. Any residual doubts these men possessed arose from their ignorance of the Permian fauna, but here Youngquist was a little ahead of the game; he had sufficient information to know his new fossils were different from those found in the Permian. Now he was sure that Triassic conodonts really did exist.26

  With the conodonts considered rare but proven survivors of the great extinction at the end of the Permian, it was now possible to imagine the animal existing well beyond the Triassic – perhaps up to the next great extinction at the end of the Cretaceous. But Stauffer's reported discovery of conodonts in Cretaceous rocks in 1940 seemed to be a clear case of contamination and Marburg doctoral student and Triassic specialist Reinhold Huckreide's search for conodonts above the Triassic in the Alps in 1955 ended in failure. Indeed, his Triassic fossils showed such senile and variable characteristics that he was convinced he was seeing an animal on the verge of extinction. Then, in 1956, East Berlin's Kurt Diebel reported “authentic conodonts” from the Upper Cretaceous of Cameroon, West Africa. This led to Huckriede's suggestion that the animal must have been restricted to a particular sea, though he had his serious doubts about Diebel's fossils, which looked characteristically Triassic. He simply could not believe that they really were of Cretaceous age.27

  Diebel's material had actually been collected in 1897–88, and consequently some now doubted its reliability. Hass called for a worldwide search.28 Others, however, welcomed the Cretaceous conodont. Lindström, who was working away at his conodont book, was convinced by Diebel's finds: “The fauna is too well preserved to have been derived from mechanical reworking through erosion of older, conodont-carrying sediments. Moreover, no such older sediments are available in the neighbourhood…. From its appearance the fauna can easily be accepted as Mesozoic and younger than the Triassic.” He thought it simply marvelous: “Through more than 300,000,000 years the same structural plan persisted essentially unaltered.” Each zero emphasized just how remarkable this unknown creature this was.29

  Müller attended a micropaleontology conference in Nigeria in 1965 and spoke on Diebel's problematic fossils, but any hopes he might have had to resolve this matter in the field were dashed by “political circumstances.” Like Huckriede, Müller thought the conodonts must have had a restricted distribution at this time as they had not been found anywhere else despite a great deal of micropaleontological work on Jurassic and Cretaceous rocks. This encouraged the thought that the animal might still exist, swimming in a sea somewhere.30 After all, the Coelacanth had risen, Lazarus-like, from the dead as recently as 1938, and it too had been thought to have perished along with the dinosaurs in the Cretaceous. The impenetrable Congolese swamp held many mysteries, including the mythological Mokele-Mbembe. Might another mysterious creature still exist somewhere off the African coast?

  Those reading and believing Lindström's textbook saw a “big, blank interval” standing between the Triassic and Cretaceous in which no conodonts had been found. Perhaps they thought that, with a little patience, this gap might also be filled. They did not have to wait long. In 1967, two Japanese workers reported conodonts from the Upper Jurassic.31 Lindström's optimism seemed to have been rewarded, but in fact this turned out to be the last straw.

  Unconvinced by the Japanese and African fossils, Triassic specialist Cameron Mosher led the assault against them. By 1969, he knew sufficient of the evolution of the Triassic conodonts to be able to demonstrate that post-Triassic examples simply did not exist. They were merely contamination. He could show that those from Cameroon were exactly like those found in the Middle, rather than Upper, Triassic. The Japanese fossils looked like those Huckriede had found in the Triassic, but the Japanese workers – convinced by the Cretaceous fossils – had imagined them as a missing link between the Cretaceous and Triassic forms. Now with the Cretaceous fossils in freefall, Mosher and Müller asked the geologists at Kyoto University to reinvestigate the site of the Jurassic finds. The results of that investigation proved inconclusive. This did not matter, however, for Mosher soon unraveled the final stages of conodont evolution in the Triassic. That period showed a rise in the number of highly specialized and rapidly evolving forms that could not have persisted as relics into these later periods.32 Such forms tended to exploit short-term niches. Ironically, then, the post-Triassic fossils were merely contamination. If anything, it made Branson and Mehl's initial doubting of Triassic forms all the more reasonable. Contamination really was a problem. Perhaps to no one's surprise, no further post-Triassic conodonts appeared, and the family tree was clipped back. The Cretaceous conodont, however, remained where it had been, printed on the pages of Lindström's book, encouraging dabblers and outsiders alike to imagine – well into the 1970s – that Cretaceous conodonts really did exist.

  By 1970, the tree might not have been perfected, but who could doubt the strength of the evidence? Who could doubt paleontology's contribution to understanding evolution or, indeed, the importance of that knowledge to the correlation of rocks across time and space? Fluid and organic, continuous and gradual, the conodont evolved as Simpson and others had imagined in the 1950s, and Brinkmann before them. But this work had taken place without high-level evolutionary theorizing.33 Then, in 1972, paleontology was again shaken out of its lazy suppositions by Stephen Jay Gould and Niles Eldredge. Gould was to become the public face of American paleontology in the late twentieth century. His rise to public notice began now as he took on the role of the “bulldog of evolutionary biology,” later to be considered a “living legend” by U.S. Congress.34 Eldredge had been a fellow student with Gould at graduate school and had become a staff member of the American Museum of Natural History. Together they challenged the belief that species evolved gradually from large populations. They suggested that the gradualism the conodont workers and others had seen was merely a result of their own earlier conditioning.35 It had long been understood, they claimed, even by Darwin himself, that the fossil record is composed of species suddenly appearing, maintaining some constanc
y, and then disappearing. The formation of new species required the separation of a species into two or more discrete populations in which evolution could take place independently. In time – and virtually no time at all in geological terms – the populations would become so distinctive that they could not interbreed. Consequently, the fossil record would show the sudden appearance of species; it could not show gradual change. The branches of the tree did not sweep gracefully upward, they said, but appeared suddenly in midair, tentatively connected at right angles to each other. The species so formed continued unchanged. Eldredge and Gould called this their theory of “punctuated equilibria,” but their first assault met with considerable opposition, and the two withdrew to regroup, returning in 1977 to answer “all the hubbub.”36

  The conodonts had not been the subject of Eldredge and Gould's attack. Indeed, they admitted to knowing little about these fossils. But Gil Klapper was intrigued. Having worked on species variability, he had, in 1969, supplied Alan Shaw with Devonian conodonts for his presidential address to the Society of Economic Paleontologists and Mineralogists. In his speech, Shaw was at his most provocative, attacking the utility of the species concept and using Klapper's fossils to make the point. What becomes a species, he said, is the result of a “non-objective art”: “Each paleontologist puts out his own work of art – that is, his species concept – in the hope, or faith, that his particular form of non-objectivity will find favor among his fellow artists.” Success relied upon salesmanship, and lists were only trusted if the author's name was known. Shaw suggested that paleontologists would be better recording morphological change and dispensing with species names altogether. As an oilman, he was interested in the utilitarian possibilities of fossils and was asserting a view that built upon those charts of variability that Austin thought so empowering. It was the antithesis of Gould's view. Gould was absolutely wedded to the notion of species being fixed and knowable, and he and Eldridge ridiculed all the doubting – this crisis of confidence in species – as being “unsurpassed in the annals of paleontology for its ponderous emptiness.”37

  Klapper, with Glenister, introduced Gould and Eldredge's ideas into their teaching, and with David Johnson, Klapper set about using conodont data to test punctuated equilibria. They published a description of the Y-shaped branching of populations into two species – the kind of branching epitomized by Helms's diagram – locating intermediate forms that suggested gradualism. Gould and Eldredge responded, proposing that these intermediate forms might be hybrids rather than moments in evolution. They suggested that Klapper and Johnson might have engaged in circular reasoning and selected their ancestors having started with this gradualistic trajectory in mind. Gould and Eldredge remarked, “We cited the evidence of…Polygnathus in detail not primarily to reveal the fragility of stories built upon it; for most ‘phylogenies’ based on fossils rely on flimsy data. Rather, we wish to demonstrate that most cases presented as falsifications of punctuated equilibria are circular because they rely, for their gradualistic interpretations, not upon clear evidence, but upon the gradualistic presuppositions they claim to test.” They continued, “Klapper and Johnson epitomize their conclusions in an evolutionary tree, unambiguously presented. These are diagrams that work their way into textbooks, there to convince the uninitiated that paleontologists can specify with assurance the (gradualistic) history of life.”38 Though Gould and Eldredge were fundamentally opposed to the views adopted by Shaw, they were no less of the opinion that there had been rather too much interpretive “art.” Klapper, who was already convinced that Gould and Eldredge's model operated in some circumstances but not all, communicated directly with Gould and became even more convinced by these new arguments.

  A second paper by Eldredge and Gould in 1977 continued this program for change. Perhaps they were now less ignorant of the conodont as the fossil equivalent of Drosophila, for they wrote, “Populations evolve, not individuals or, still less, anatomical parts of individuals.” The universal evolutionary change that underpinned the conodont workers’ ambitions and had so effectively produced global correlations was theoretically incomprehensible to Gould: “If such problems as these routinely occur when we deal with closely related population samples within a single depositional basin, then the wholesale application of such a research strategy to problems of international correlation (as Shaw, 1969, and Barnett, 1972, have recently done with conodont data) presents many problems and carries little prospect that self-correcting results can emerge. The assumptions underlying such a procedure are simply too vast and too ill-founded. It can't work.” Eldredge may, however, have empathized a little with conodont workers, as he too had utilized the “stage of evolution” argument in his studies of trilobites.39 Gould, however, was firmly of the opinion that such interpretation illustrated “the most pervasive and nefarious influence that phyletic gradualism has had on the development of biostratigraphic methodology.”

  Gould was at this time pioneering a view of evolution as a succession of particular, unique, and unrepeatable events: “Infraspecific trends in vertical outcrop of one local area may not be repeated in an adjacent region.”40 Replay the history of life, Gould believed, and an entirely different tree of life would take shape. Gould's interest in history would have told him that the past was contingent on particular conditions and events. He saw the history of life in similar terms.

  Like many areas of paleontology, conodont studies possessed a resilience in these debates because the rock record provided the ultimate truth. Only here might one locate objective fact. So as these arguments raged, most in the conodont community were untouched by them. That is not to say that they were not interested but simply that the arguments had little direct impact on their work. At that moment, the finishing touches were being put to the second appearance of conodonts in the Treatise on Invertebrate Paleontology – now these fossils occupied a whole volume. Here Helms's evolutionary tree, coauthored with Ziegler, was updated but little altered. Gradualism stood its ground here at least, and it did so by turning a blind eye. Conodont workers were already reflecting upon the success that had resulted from their own way of looking: “The first job of conodonts was to demonstrate the value of “nuts and bolts” in stratigraphy. This is being done and on a larger scale than many paleontologists would have guessed. A complete reliable and world-wide zonation of Middle Cambrian to Upper Triassic strata based on conodonts may be possible.” But this Treatise would suffer the fate of the first one: Delayed in publication, it too would be out of date by the time it finally appeared in 1981.

  The revolution that had taken place in the 1960s permitted the conodont to come of age as a scientific object. The animal itself had acquired an evolutionary identity that had been mapped perfectly across time and was second to none. But in this decade, there were tremors that had their origins in earlier times, when Branson and Mehl, and American science in general, decided to deny the truth of the assemblage. Ziegler had risen to the top of conodont stratigraphy by a refined use of the kind of study these Missouri workers had undertaken. But as he rose to the top on the basis of mapping individual conodont fossils, the biological truth of the animal continued to seep out into the everyday of conodont science. It seemed almost inevitable that the abstract basis on which Ziegler's science was based would be challenged.

  After a short but violent paroxysm, and about midnight, between the 11th and 12th of August, a luminous cloud enveloped the mountain. The inhabitants of the sides and foot of the volcano betook themselves to flight, “but before they could save themselves, the whole mass began to give way, and the greatest part of it actually fell in and disappeared in the earth.” This was accompanied by sounds like the discharge of heavy cannon.

  HENRY DE LA BECHE

  The Geological Observer (1851)

  EIGHT

  Fears of Civil War

  IN 1967, WILLI ZIEGLER STOOD ON THE SUMMIT OF A utilitarian mountain. Now, as he surveyed the world's Devonian rocks, he fancied that he had within his gra
sp the means to correlate them all. This mountain had been built through the efforts of generations of stratigraphers who had turned the conodont into an abstract timepiece. Buried somewhere near the mountain's base were Kindle's call to action and Ulrich's erroneous assertions. The greater mass was American and had been shaped by Branson and Mehl and few others. The summit, however – where Ziegler now stood, flag in hand – was largely German. Here, inspired by Beckmann's proof of the conodont's potential in the German Devonian, a whole generation had raced for glory, their heads filled with thoughts of mapping the evolution of animal parts. Only on the upper slopes did Ziegler scramble ahead, driven by ambition, extraordinary resources, and sheer hard work.

  The practical science that had built this mountain had found no need for the animal, but after 1950, its biology was hard to ignore; the assemblage had become, for almost everyone, an undeniable truth. It was now impossible to look into drawers of these fossils and not see a deception, an act of denial, a piece of non-science – perhaps even pure nonsense. Matters had not been helped by the willingness of those who had believed in the assemblage to nevertheless toe the line. But then, in the 1950s, everyone also knew that the conodont was important only for the huge stratigraphic potential it possessed. This, however, produced a seemingly insoluble dichotomy: Should they keep the fossil as an abstract tool and in so doing deny the animal its biology or should they adopt the animal as the essential basis for rigorous science but then risk shaking this mountain to its core? The conodont workers had cleverly thought they might “have their cake and eat it.” Better to change the law, they thought. But when the parataxa plan failed, Raymond Moore – frustrated by the conodont workers’ nonconformism – thrust his own solution upon them, effectively telling them to let the animal sleep and continue their old utilitarian ways. Moore was, however, no conodont worker, and he did not have to deal with the contradictions and unrealized potential that daily faced those who were. Inevitably, among some of those studying these fossils there developed a creeping sense that the science could not go on living a lie. It was the animal itself that told them this, for in tantalizing glimpses it began to reveal sufficient of itself to challenge the charade. Gently, it seemed to push for its own recognition. In time, surely someone would take a stand?