The Great Fossil Enigma (34 page)

Walliser was not convinced by Schindewolf's explanation either, but he knew Schindewolf's data were good and that the phenomenon of global extinction he described was real. That fascinated him and soon began to affect the way he interpreted rocks and fossils in the field, particularly after 1965. That year he visited Iran and discovered a Devonian sequence that was lithologically and paleontologically identical to that back home. He thought this remarkable because it meant that particular changes of environment must have taken place across an extraordinarily wide area, perhaps even globally. What especially fascinated Walliser was the fact that the rocks themselves were capable of showing this change. He now understood that seemingly local phenomena, such as nodules in Devonian strata, were not local at all and that the peculiar characteristics of particular beds in one locality – such as their predisposition to slip and slide (a quality he tested by chewing the rock!) – could be global in their distribution too.
⁶
Walliser's fascination with these unexplained global phenomena grew.

As he traveled farther afield, particularly to Asia, so his initial findings would be confirmed. He became a connoisseur of rock sequences, increasingly convinced that nature preserved natural global markers recording moments of transformation in the earth's history. However, his views were not shared by those more utilitarian stratigraphers engaged in dividing rocks up into neat, globally recognized parcels. Walliser became an outspoken advocate for locating and using natural boundaries in rock sequences. His critics preferred to drive their boundary-defining, and metaphorical, “Golden Spikes” into sequences where nothing much happened but where the replacement of one species by another could be recognized globally. He did have some early successes, however, such as in setting the maj or Silurian-Devonian boundary at a meeting in Bonn in 1960. But such victories were rarely permanent. Mass extinctions were often associated with difficult lithologies and incomplete rock sequences; even an imaginary Golden Spike cannot be driven into rocks that are not there. Consequently, throughout the 1960s, the artificial scheme gained ground and was adopted by all the various grandly named subcommissions that sought to define and adjudicate on these global boundaries. Walliser found himself in the minority, frustrated by the victory of utilitarianism over nature.
⁷
In the story of the conodont, of course, this is not an unfamiliar theme.

Walliser was not entirely alone. In 1969, his friend Digby McLaren of the Geological Survey of Canada was at last willing to admit to the vital importance of these natural boundaries where a range of unrelated animals and plants became extinct, adding, pointedly, “[boundaries] which we are trying to define out of existence.” In his presidential address to the Paleontological Society that year, McLaren said these boundaries were of two types. The first was quiet and merely man-made for convenience, but the second recorded some “event” “across which something happened.” It was to explain a boundary of this second kind – a major extinction in the Devonian known as the Kellwasser Event, which he had first recognized in the 1950s – that he “landed a meteorite in the ocean with effects that had been described by [Robert] Dietz in an article in
Scientific American”
in 1961: “Dietz…suggests a giant meteorite falling in the middle of the Atlantic Ocean today would generate a wave twenty thousand feet high.” McLaren pondered the consequences of a similar event for his now extinct animals, and acknowledged, “This will do.”
⁸

Given the reception Schindewolf's alien causes had received, McLaren knew that he risked being labeled a crank. The preferred explanation for mass extinction was the rise and fall of sea level resulting from ice ages and major vertical movements in landmasses. (We need to remember that the vast majority of fossils – and therefore recorded extinctions – are of sea animals.) To this audience, then, McLaren's meteorite was unexpected and unneeded. The response to it is perhaps typified by one English contemporary, Michael House, who believed McLaren had said this “doubtless with tongue in cheek.” House viewed the problem through spectacles constructed from geology's most important guiding principle, uniformitarianism, a belief that the world of the past was created by the same gradual processes we continue to see today. Science neither needed nor had a place for catastrophes of this kind. But this was not how McLaren saw it at all: “I do not believe this explanation is farfetched…. We must look for more than everyday happenings to explain many geological features.”
⁹

It was, however, simply speculation; there was no evidence of an impact, even if some contemporary astronomers – beyond earshot of the geological community – thought sizable meteorites must have collided with the earth in the past.

These late 1960s discussions of extinction caught the attention of others in the conodont community, forcing them to think new thoughts. Dave Clark, at the University of Wisconsin in Madison, for example, saw in extinction an opportunity for separating true species from their mimics and imitators. This insight arose from work that Clark's doctoral student, James Miller, was undertaking to disentangle the evolution of individual conodont elements in the late Cambrian. With an expectation of finding just four conodont elements in each kilogram of rock, Miller – who now replaced Müller as the most prolific worker on these earliest of conodonts – was nevertheless able to demonstrate that identical elements evolved in quite separate branches of the evolutionary tree. Clark recognized that Miller's great advantage was to study that first burst of evolution, as it permitted him to build upon a clean slate. It suggested to Clark that if one wanted to replicate Miller's trick anywhere else in the family tree, it would be necessary to locate a point of mass extinction and build the family tree from there, in that subsequent explosion of evolution Schindewolf had recognized.
¹⁰
Clark's interest in extinction reflected a utilitarian desire to be able to precisely identify his fossils; the attraction was not to indulge in imaginative speculation. He began, then, by asking when extinctions took place in the conodont world. Clark wanted a way to visualize changing diversity beyond the range charts of species and genera widely used by stratigraphers. He wanted to know not the pattern of life but the pattern of extinction.

He began by plotting the number of form genera present in each major period of geological time together with the number that went extinct in that period. He knew the picture he drew was coarse and that his data were imperfect, and he was therefore not surprised when the technique threw up some odd artifacts of method. The Silurian, for example, appeared to be a period of crisis for the conodont animal when, really, the low number of species reflected the period's relatively short duration. As if to record the path he had traveled and perhaps prevent others from falling into the same trap, Clark published the diagram nevertheless. He then improved this picture by increasing its resolution and plotting only those species that first appeared within a given period. Now his plot showed extinction periodically overtaking evolution. In other words, there were moments of decreasing diversity – of impending crisis. Turning these two measures (new species emerging and old species becoming extinct) into ratios, he could then plot what he called an “index of evolution,” which showed graphically when the conodont animal was in crisis and when it hit boom times. It was to prove an influential study and one to which Clark would return a decade later, wondering why the conodonts supported two peaks in their life history rather than one.
¹¹

Inspired by Valentine and the new plate tectonics, Lars Fåhræus saw in Clark's diagrams the opportunity to give these tiny lives a tumultuous Wagnerian interpretation.
¹²
Everything about the conodont – its form, distribution, diversity, and evolution – Fåhræus believed, could be mapped against an earth composed of violent volcanic island arcs, massive plates of continental crust drifting through climatic zones, and huge continental collisions. It was presumed that the conodont lived, like nearly all marine life, at the continental margins and was thus both an opportunist and a victim as continents separated and came together. He constructed a pictorial representation with his rectangular representations of the earth's landmasses performing their ballet to the timing of Clark's extinction overture. The earth's violent revolutions were reflected in smaller revolutions in the conodonts themselves. Or to turn things on their heads, as every conodont worker would, one now might examine a tiny conodont and believe that it reflected in its form the trials and tribulations of a whole planet. Fåhræus's pictorial explanation required little further explanation (
figure 10.1
); it met Schopf's ideal of the grand paleontological hypothesis better than any other. It linked life to events in the earth's history and did so using plate tectonics, the flavor of the decade.

10.1.
Fåhræus's choreography. The upper graph is based on Clark's data and similar to the graphs Clark drew. The solid line marks appearances of new species, while the dashed line indicates extinctions. Where the former is below the latter, conodont diversity is in decline. Fåhræus suggested that this tiny animal's success was partly determined by the changing configurations of Earth's landmasses – here indicated by black rectangles – which resulted in changes in environmental diversity. Reproduced with permission from L. Fåhræus,
Conodont Paleoecology
(1976).

Walliser knew that if the topic of mass extinction was to be tackled empirically, it would need funding. This was big science, requiring collaboration. He managed to convince some of his German colleagues that the project was worthwhile, but when no money was forthcoming their enthusiasm naturally waned. Then, in the late 1970s, a former colleague from Tübingen who had moved to the United States asked Walliser if he would become secretary general of the International Palaeontological Association
(IPA).
Walliser admitted that he had never heard of the
IPA
. Indeed, nor had any of his colleagues. On enquiring, he discovered it was a body representing the world's paleontological societies. Given Walliser's international outlook, sociable nature, and desire to pursue his big idea, he realized the organization might be just what he needed.

Walliser's arrival at the
IPA
resulted in a complete reappraisal of its business and ambitions.
¹³
The big idea was developing, and with it an international community. But still there was no funding. Then the Alvarez meteorite hit and everything changed. With mankind now imagining something nasty hiding in the night sky, and McLaren remade as a prophet, Walliser at last found his funding. What had once been a rather arcane scientific problem had suddenly become front page news.

He announced what was the
IPA'S
first ever research project in 1982, securing funding for five years from the International Geological Correlation Programme
(IGCP)
not long afterward.
¹⁴
Walliser launched Project 216, Global Biological Events in Earth History, at the International Geological Congress in Moscow in August 1984 and immediately began to build the multidisciplinary community of researchers necessary for this big science. Beginning with his own network of contacts and members of the
IPA
, who in turn used their own, in time the project would attract participants from forty-nine countries. This really was science on a grand scale.