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 book'. 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 M 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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