The Great Fossil Enigma (23 page)

Lindström returned to his experiments, hoping that acetic acid would transform his bituminous limestones into a fossil wonderland, but those rocks dissolved poorly. Undeterred, he located some purer Ordovician limestones, and in these he found his first conodonts. He now realized the potential of his discovery, for he could order and correlate rocks in ways his colleagues could not. He could imagine himself a solitary pioneer in a new field of Swedish study, and he worked day and night to produce his first paper, beginning his collecting for it in 1953. That landmark paper brought recognition, and before long, he saw his career stretching out before him, with the chair at Uppsala, then occupied by Per Axel Thorslund, already in his sights.

Like others, Lindström published his own summary reflections on the field early in his career. As his career had begun in a rather precocious manner, it is perhaps unsurprising that his summary took the form of a monograph – the first of its kind in the field – published in early 1964. The publisher had been sent in Lindström's direction by Anders Martinsson, a brilliant and universally admired micropaleontologist. Extremely competitive and temperamental, Martinsson was then at the University of Uppsala, which was Sweden's palaeontological center and Lindström's goal. Lindström later wondered, with a smile on his face, whether Martinsson had recommended him to the publisher in order to distract him with a book that would never be recognized by those who elected that university's chair of paleontology. The book certainly did not help Lindström's career, but the Uppsala dream effectively died, so Lindström thought, when he had the audacity to suggest that Sweden's Ordovician rocks were deposited in deep water. The Swedish long beards knew that this was not the case. In that country's small and claustrophobic geological world, you were either in or out; Lindström was now out. Luckily, Otto Walliser threw him a lifeline from Germany, having located a chair for his Swedish friend in Marburg. German science had no problems with Lindström's unorthodox ways. In 1966, Ziegler moved back to Marburg from the Geological Survey, when the opportunity arose, drawn not least by the chance to work with Lindström, whom he considered the “senior conodont scholar.”
²⁴

Had any of Lindström's Swedish colleagues really understood conodonts, they might have been rather less dismissive of his book. Simply called
Conodonts
, it was rather more than a textbook. Unaware of what was in the still unpublished
Treatise
, Lindström used the book to reimagine conodont science. It brimmed with imaginative ideas, many of which had a real impact. It was positively reviewed in the British press (it was published in English), being deemed both timely and well executed and seeming to invent a science of “conodontology.”
²⁵
It was the grandest of the reviews of conodont science, which marked the rebirth of the subject. Like the others, it was infected with optimism.

In Germany, Sweden, and Britain, the return of peace saw the rise of entirely new communities of conodont workers, but in the United States change was more subtle and generational. Iowa then became important for producing conodont workers, and among these was Walt Sweet, whose education had benefited from the
G.I.
bill after the war. He had ended up at Iowa because his college mentor in Colorado had graduated from there; there was no more logic or ambition to it than that. What Sweet found there was a kind of paleontology that doubtless had something of Branson and Mehl's Missouri about it. Miller, who became Sweet's supervisor and friend, had been one of Branson's students and had inherited Branson's obsession with publication. “Miller published like crazy,” Sweet later reflected. “He was big on illustrations but short on real innovations.” It was Branson and Mehl's personal encouragement that had persuaded Furnish to work on Lower Ordovician conodonts in the late 1930s. “Bill was A. K.'s assistant on a large project involving nautiloids in the U.S. Nat. Museum's vast collections,” Sweet remembers. “It is my recollection that A. K. kept Bill busy on this project night and day and that Bill undertook the conodont study as his own PhD project, which he conducted late at night and at other times when A. K. did not demand his presence.” Shortly afterward Furnish was off to Saudi Arabia to work for
ARAMCO
, not to return to Iowa City until 1953. When Sweet arrived in 1950, he was the only one interested in conodonts. However, he remained for the most part a cephalopod man at Iowa, though he spent his summers back in Colorado teaching on a field course and working on the Harding and Freemont – strata that, respectively, contained conodonts and cephalopods.

Sweet took up an academic position at Ohio State University in Columbus in June 1954 and remained there for his entire career. In 1956, he obtained a Fulbright Research Grant, which enabled him to spend a year studying nautiloids at the University of Oslo in Norway. While there, he traveled to Lund and Stockholm and became acquainted Lindström, Stensiö, Jarvik, and others. Lindström made a return visit in 1959 or 1960, spending six months in Columbus, and the two became close friends. It was in part a result of this that Stig Bergström (“small, officious, very good, very sharp and with a photographic memory”)
²⁶
arrived in Columbus in 1960 to undertake his doctoral degree under Sweet's supervision. This was before Sweet considered himself a conodont specialist. Bergström traveled to Sweden briefly in the hope of finding one of those rare academic positions there but then returned to stay in Columbus, where he was hired as an assistant professor and curator of the Orton Geological Museum in 1968. He became a professor of geology in 1972, and a few years later, director of the museum and a U.S. citizen. He and Sweet became close collaborators.

Sweet's full conversion to conodonts occurred rather later than others mentioned in this chapter. The turning point came when Miller and Furnish failed to complete their promised biological description for the cephalopod volume of the
Treatise.
Frustrated, Moore asked Sweet to take it up. He knew Sweet had no choice in the matter because his own work was in the volume waiting to be published. So that was how Sweet spent the summer of 1964. Never really a biologist, he cribbed whatever information he could: “By the time I got through with that volume I decided that there was never ever going to be a time when nautiloid cephalopods are worth a damn stratigraphically.” It was with these thoughts in his head that he found himself converted unexpectedly into a conodont specialist. He had already set his students to do some self-contained stratigraphic projects using conodonts and was delighted to see the results of their work. Although he had published on conodonts in the 1950s, it was this work by his students that completely altered his research focus. In the years ahead, he and Bergström would have a major impact on the way others visualized the unknown animal. Near the end of his career, Sweet would also write the only other solo English-language monograph dedicated to these fossils. And like his mentors in Iowa, Sweet would turn his department in Columbus, Ohio, into a conodont factory, pouring forth conodont specialists.

Before World War II, the science of conodonts had laid down its roots. It had not fully realized its potential, and thinking was constrained by geographical isolation and the dominance of American utilitarianism. The science that emerged after the war was quite different and little connected it to that earlier period. Now it branched out and blossomed, liberated by acids and in the possession of this new generation of actors who were set on pursuing a better future. Geographical isolation vanished – at least in the West. The fossil and its workers began to build international connections almost immediately. There was to be one aspiring and sophisticated global science.

 

IN GERMANY, EVERY STUDENT OF PALEONTOLOGY LEARNED OF
their compatriot Roland Brinkmann's 1920s centimeter-by-centimeter study of the English Oxford Clay. His three thousand beautifully preserved, ornate, and nacreous
Kosmoceras
ammonites recorded the reality of evolution with wonderful picture-book clarity, each twist and turn on their evolutionary journey permitting a moment in time to be defined and used to order and correlate rocks elsewhere.
¹
Brinkmann's study traced the evolution of these fossils through just fifteen meters of the clay. Now Beckmann's disciples, armed with the gift of efficient acid preparation and the ubiquitous and rapidly evolving conodont, aimed to perform the same trick on a far grander scale – through the whole of the German Devonian. Quick to recognize the heroic possibilities of this new challenge, in the mid-1950s, this generation believed they possessed nothing less than the makings of a worldwide standard.

These new German workers were perhaps more attuned to evolutionary thinking than were their American forebears before the war. Otto Walliser, for example, was a devout Darwinian. For him, it was this that made paleontology attractive. While many in America were also now Darwinians, this had not always been the case. Before 1930, according to George Simpson, professor of vertebrate paleontology at Columbia University in New York, most paleontologists in North America believed in evolution but few placed any significance on “natural selection” – that element that distinguished Darwin's theory from the work of other evolutionary theorists. There, for the majority, “Darwin was dead.” If the American paleontologists thought about evolution at all then, it was “evolution by random mutation” or “evolution by the inheritance of acquired characters.” Simpson recalled that his own teacher, when lecturing on the subject, “gave equal billing to all the conflicting theories on the causes of evolution…but personally espoused none of them.” Evolution was in open season, with relatively little to constrain personal interpretations.
²

It was the American utilitarian mission for paleontology that had created this tendency to dispense with “unnecessary science.” The chief geologist of the Pure Oil Company in Texas, for example, had told his petroleum geologist colleagues in 1927 to map and curate “a history of the development of numerous inter-fingering and diverging races, an outline of their advances, culminations, and disappearances. We have learned that genera make progress along definite lines.” This was economic evolution without the leisure of biological meaning: “Making correlations from field to field and from well to well in the quickest possible time must use all the tools which are available.” This kind of thinking permeated the tiny community of conodont workers in the 1930s, encouraging two Oklahoma paleontologists to believe they could see an evolutionary sequence in a series of leaf-like conodonts from the Lower Pennsylvanian (Upper Carboniferous). Here
Cavusgnathus
appeared to evolve into
Idiognathoides
, which in turn became
Idiognathodus
, as a central channel closed and transverse ridges developed to cover the surface of the tiny fossil. They admitted that there was no stratigraphic evidence for detecting this evolutionary direction but “considered it a case of parallelism after the manner of development of mammalian teeth” from a single reptilian cusp to a corrugated form. This was indeed an invocation of evolutionary “progress along definite lines.” The argument was soon dismantled by Branson and Mehl, but only through improved collecting. They offered no more sophisticated understanding of evolution.
³

The conodont workers were, however, aware that identical forms seemed to have evolved repeatedly at different points in time. These were the products of convergent evolution and called homeomorphs. For example, Branson and Mehl noticed that their Lower Carboniferous
Taphrognathus
and Stauffer and Plummer's Upper Carboniferous
Streptognathodus
were indistinguishable though not the same fossil. In 1938, Bill Furnish had said the only way to see beyond such illusions was to unravel the fossils' evolutionary pasts. In other fossil groups such an undertaking might have been seen as a little idealistic, but the conodont workers had come to think this entirely possible after only a few years of intensive study. Branson and Mehl believed they could see evolutionary trends and thereby guess the form of fossils occupying gaps in the record. They were not alone. Sam Ellison's holistic review of the literature convinced him of the conodonts' value to evolutionary studies. The key to such studies, however, was further collecting rather than a more sophisticated understanding of evolutionary theory. It was careful collecting alone that permitted Carl Rexroad, for example, to demonstrate in 1958 that
Taphrognathus
gave rise to
Cavusgnathus
, which in turn spawned the
Taphrognathus
-imitating
Streptognathodus.
⁴

The beginnings of a change in the way paleontologists thought about evolution came when J. B. S. Haldane's 1932 book
The Causes of Evolution
revealed the impact of natural selection on the genetic makeup of living populations. In truth, few geologists or paleontologists initially took much notice of this work, which seemed to signal that geneticists had taken control of evolutionary study. Indeed, Simpson half joked that geneticists thought paleontology too descriptive to be called a science, that by studying the stony remains of fleshy life, it was incapable of understanding the subtle complexities of evolutionary change: “The paleontologist, they say, is like a man who undertakes to study the principles of the internal combustion engine by standing on a street corner and watching the motor cars whiz by.”
⁵

But Simpson did not stand by and watch his science be pushed aside. Inspired by his colleague Theodosius Dobzhansky's 1937 synthesis of modern genetics with Darwinian theory, he rushed to paleontology's defense, publishing his own book,
Tempo and Mode in Evolution
, in 1944. In it he placed paleontology within this new synthetic view, suggesting that it could contribute “on the rates of evolution, modes of adaptation, and histories of taxa.” Together with an earlier essay, this book reintroduced paleontologists to Darwin. The effect on paleontology was revolutionary. Now evolution was to be understood as “genetic mutation and variation, guided toward adaptation of populations by natural selection.” This emphasis on populations was a radical departure for paleontologists, who had traditionally thought of species in terms of the most typical individual. American paleontologist Carl Dunbar recalled the revolution in 1959: “This whole scheme collapsed like a house of cards in 1940 when George Simpson published his short but epoch-making paper on Types in Modern Taxonomy.”
⁶

However, the notion of a species as an interbreeding population proved something of a challenge for paleontologists dealing with fragmentary, sporadic, and variable finds of long-dead animals and plants – so much so that the “New Paleontology” soon became preoccupied with understanding the meaning of variations of form. Uncertainty grew within the paleontological community. At a major symposium in London in 1954, it seemed that species were no longer fixed or definite; some clearly graded from one form into another across time and space.
⁷
Those attending worried that they could not identify true biological species, only groups of animals that looked morphologically the same. But if paleontologists could not work with biological species, how could their fossils be trusted to show the truth of evolution? Organizer Sylvester-Bradley warned that the “distinction, in fact, between morphological species and biospecies can only be overlooked at the peril of utter confusion.” Paleontologists, uncertain what might conform to a true species, preferred to see variation of form as an “evolutionary plexus.” The only means to determine the boundaries between species was to collect numerous specimens from a single location and horizon and search for breaks in the distribution of forms. If there had been a crisis of faith in Darwinian evolution before the war, a similar crisis in species gathered strength in the 1950s and would continue to dog the science for the next twenty years.

Some paleontologists were, however, rather less concerned about these problems. They felt simple pragmatism would permit them to sidestep the difficulties of theoretical explanation. Indeed, some saw this population-centered view as liberating. It offered yet another way to make an assault on the proliferation of species names. Ronald Austin recalled how inadequate the literature was at the start of his career: “There was nothing!” A student of Frank Rhodes, he drew inspiration from work done at the Illinois State Geological Survey, where Carl Rexroad, Gil Klapper, Charlie Collinson, and Alan Scott were working on conodonts. Scott and Collinson produced pictorial plots of variability; the variations within them could be subdivided into a number of distinctive morphological types. Austin loved this pictorial simplicity, which surpassed verbose attempts at differentiation in words. Paleontology had always been a pictorial science, and these new diagrams effortlessly showed that species erected on the basis of a few specimens had little validity.
⁸
They offered a way to circumvent the mire of taxonomic description.

The sheer numbers of rapidly evolving conodonts, their easy extraction using acids, the desires of a new generation on the rebound from the war, the reignition of Darwinian evolution, the fine sequences of Devonian rocks, and the possibilities for a global standard for correlation produced the conditions for a German revolution. Plastic in form and potentially large in number, the conodonts seemed the ideal subject for the population-centered study of evolution. Only in such circumstances might paleontologists believe they were studying true – biological – species. The conodont held the potential to become the palaeontological equivalent of the geneticist's fruit fly,
Drosophila.
But unlike the ephemeral fruit fly, the conodont animal had written an evolutionary diary in stone. Every moment of its existence, it seemed, was there for the reading.

Among those who wished to lead this assault on the German Devonian was, as I have mentioned, Klaus Müller. His East German limestones, left over from his doctoral studies and dissolved in acid out of desperation, produced the first evolutionary study of the dominant conodont genus,
Palmatolepis.
The work was followed up by Walter Gross's assistant at Humboldt University in East Berlin, Jochen Helms, who began his own study in Thuringia in 1958. His first results, published in 1961, teased apart the changes that took place in a distinctively noded group of
Polygnathus.
They also revealed to him the problems of recognizing and then delineating the pattern and flow of change taking place in the animal. The rocks themselves formed the background against which these changes were observed. They in effect represented time, but because they resulted from varying rates of sedimentation, and intervals of non-sedimentation, time was distorted in undetectable ways. The cephalopod fossils traditionally used to track time through these rocks helped little. The timescale they offered was simply too coarse.
⁹
Helms understood that these problems would lead to imperfections in his understanding, nevertheless, he knew that these problems would be resolved in time. A greater cause for discomfort was the sheer variety of form, which seemed to conceal the flow and direction of evolution. Eyes alone, he believed, could not make objective sense of this. So he resorted to statistics to produce species and subspecies from the varied forms he possessed. Fortunately the end members of these evolutionary moments – the evolutionary descendents – were much more constant, and he could then trace these forms backward into the morphological soup. By doing so, a picture of evolution, as it had occurred “in Thuringia” hundreds of millions of years before, revealed itself.

Helms could now see a “knotty kind” of
Polygnathus
giving rise to the extraordinarily successful and useful
Palmatolepis.
But, more interestingly, he could see that behind this dominant form, the conservative line of
Polygnathus
continued and, when
Palmatolepis
finally had its day and went into decline, so another branch arose from these roots. This new branch carried the “nodocostata group,” which diversified and began to develop forms reminiscent of
Palmatolepis.
It might have occurred to Helms how perfectly the conodont performed as a “fossil fruit-fly,” for it seemed to echo performances observed by Thomas Hunt Morgan in his pioneering studies of these insects: “There is another result, clearly established by the genetic work on
Drosophila
, that is favorable to the final establishment of a new type or character if it is beneficial. Most, perhaps all, of the mutations appear more than once. This improves their chances of becoming incorporated in the species, and if the mutation produces a character that favors survival the chance of its becoming established is still further increased.”
¹⁰