Dinosaurs in perspective Part 3

Dinosaur palaeontology in decline

Paradoxically, the culmination of Dollo’s remarkable work on this dinosaur and his international recognition as the ‘father’ of the new palaeobiology in the 1920s marked the beginning of a serious decline in the perceived relevance of this area of research within the larger theatre of natural science.

In the interval between the mid-1920s and the mid-1960s, palaeontology, and particularly the study of dinosaurs, rather unexpectedly stagnated. The excitement of the early discoveries, notably those in Europe, was succeeded by more the spectacular ‘bone wars’ that gripped America during the last three decades of the 19th century. These centred on a furious – and sometimes violent – race to discover and name new dinosaurs, and had all the hallmarks of an academic equivalent of the ‘Wild West’. At its centre were Edward Drinker Cope (a protege of the polite and unassuming Professor Leidy) and his ‘opponent’ Othniel Charles Marsh at Yale University. They hired gangs of thugs to venture out into the American mid-West to collect as many new dinosaur bones as possible. This ‘war’ resulted in a frenzy of scientific publications naming dozens of new dinosaurs, many of whose names still resonate today, such as Brontosaurus, Stegosaurus, Triceratops, and Diplodocus.

Equally fascinating discoveries were made, partly by accident, during the early 20th century in exotic places such as Mongolia by Roy Chapman Andrews of the American Museum of Natural History in New York (the real-life hero/explorer upon whom was based the mythical ‘Indiana Jones’); and in German East Africa (Tanzania) by Werner Janensch of the Berlin Museum of Natural History.

More new dinosaurs were continually being discovered and named from various places around the world, and although they created dramatic centrepieces in museums, palaeontologists seemed to be doing little more than adding new names to the roster of extinct creatures. A sense of failure took hold to the extent that some even used dinosaurs as examples of a theory of extinction based on ‘racial senescence’. The general thesis was that they had lived for so long that their genetic constitution was simply exhausted and no longer capable of generating the novelty necessary for the group as a whole to survive. This supported the idea that dinosaurs were merely an experiment in animal design and evolution that the world had eventually passed by.

Not surprisingly, many biologists and theoreticians began to view this area of research with an increasingly jaundiced eye. New discoveries, though undeniably exciting, did not seem to be providing data that would lead in any particular direction. Discovery required the scientific formalities of description and naming of these creatures, but beyond that all interest seemed essentially museological: to be brutal, the work was seen as the equivalent of ‘stamp collecting’. Dinosaurs, and many other fossil discoveries, offered glimpses of the tapestry of life within the fossil record, but beyond this their scientific value seemed questionable.

Several factors justified this change of perception: Gregor Mendel’s work (published in 1866, but overlooked until 1900) on the laws of particulate inheritance (genetics) provided the crucial mechanism to support Darwin’s theory of evolution by means of natural selection. Mendel’s work was elegantly merged with Darwin’s theory in order to create ‘Neodarwinism’ in the 1930s. At a stroke, Mendelian genetics solved one of Darwin’s most fundamental worries about his theory: how favourable characteristics (genes or alleles in the new Mendelian language) could be passed from generation to generation. In the absence of any better understanding of the mechanism of inheritance in the mid-19th century, Darwin had assumed that characters or traits, the features subject to selection according to his theory, were blended when inherited by the next generation. This, however, was a fatal flaw, because Darwin realized that any favourable traits would simply be diluted out of existence if they were blended during reproduction from generation to generation. Neodarwinism clarified matters enormously, Mendelian genetics provided a degree of mathematical rigour to the theory, and the revitalized subject rapidly spawned new avenues of research. It led to the new sciences of genetics and molecular biology, culminating in Crick and Watson’s model of DNA in 1953, as well as huge developments in the fields of behavioural evolution and evolutionary ecology.

Unfortunately, this fertile intellectual ground was not so obviously available to palaeontologists. Self-evidently, genetic mechanisms could not be studied in fossil creatures, so it seemed that they could offer no material evidence to the intellectual thrust of evolutionary studies during much of the remainder of the 20th century. Darwin had already foreseen the limitations of palaeontology in the context of his new theory. Using his inimitable reasoning, he noted the limited contribution that could be made by fossils to any of the debates concerning his new evolutionary theory. In a topic of the Origin of Species devoted to the subject of the ‘imperfections of the fossil record’, Darwin noted that although fossils provided material proof of evolution during the history of life on Earth (harking back to the older progressionists’ arguments), the geological succession of rocks, and the fossil record contained within in it, was lamentably incomplete.

Dinosaur paleobiology: a new beginning

It was not until the 1960s and early 1970s that the study of fossils began to re-emerge as the subject of wider and more general interest. The catalyst for this re-awakening was a younger generation of evolutionarily minded scientists eager to demonstrate that the evidence from the fossil record was far from being a Darwinian ‘closed topic’. The premise that underpinned this new work was that while evolutionary biologists are obviously constrained by working with living animals in an essentially two-dimensional world – they are able to study species, but they do not witness the emergence of new species – palaeobiologists, by contrast, work in the third dimension of time. The fossil record provides sufficient time to allow new species to appear and others to become extinct. This permits palaeobiologists to pose questions that bear on the problems of evolution: does the geological timescale offer an added (or different) perspective on the process of evolution?; and, is the fossil record sufficiently informative that it can be teased apart to reveal some evolutionary secrets?

Detailed surveys of the geological record began to demonstrate rich successions of fossils (particularly shelled marine creatures) -considerably richer than Charles Darwin could ever have imagined, given the comparative infancy of palaeontological work in the middle of the 19th century. Out of this work emerged observations and theories that would challenge the views of biologists over the modes of biological evolution over long intervals of geological time. Sudden massive, worldwide extinction events and periods of faunal recovery were documented which could not have been predicted from Darwinian theory. Such events seemed to reset the evolutionary timetable of life in a virtual instant, and this prompted some theorists to take a much more ‘episodic’ or ‘contingent’ view of the history of life on Earth. Large-scale, or macroevolutionary, changes in global faunal diversity over time seemed to be demonstrable; these again were not predicted from Darwinian theory and required explanation.

Most notably, however, Niles Eldredge and Stephen Jay Gould proposed the theory of ‘punctuated equilibrium’. They suggested that modern biological versions of evolutionary theory needed to be expanded, or modified, to accommodate patterns of change seen repeatedly among species in the fossil record. These consisted of prolonged periods of stasis (the ‘equilibrium’ period) during which relatively minor changes in species were observable, and contrasted with very short periods of rapid change (the ‘punctuation’). These observations did not fit well with the Darwinian prediction of slow and progressive change in the appearance of species over time (dubbed ‘evolutionary gradualism’). These ideas also prompted palaeobiologists to question the levels at which natural selection might function: perhaps it could operate above the level of the individual in some instances?

As a consequence, the whole field of palaeobiology became more dynamic, questioning, and also outward-looking; it was also prepared to integrate its work more broadly with other fields of science. Even highly influential evolutionary biologists such as John Maynard Smith, who had had little truck with fossils at all, were prepared to accept that palaeobiology had valuable contributions to make to the field.

While the general field of scientific palaeobiology was re-establishing its credentials, the mid-1960s was also a time of important new dinosaur discoveries; these were destined to spark ideas that are still important today. The epicentre of this renaissance was the Peabody Museum at Yale University, the original workplace of ‘bone-fighter’ Othniel Charles Marsh. However, this time it was in the person of John Ostrom, a young professor of palaeontology with a strong interest in dinosaurs.

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