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DARWIN'S CENTURY -- EVOLUTION AND THE MEN WHO DISCOVERED IT |
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Glossary Uniformitarianism, that scientific school of thought generally associated with the names of James Hutton and Sir Charles Lyell which assumed that geological phenomena were the product of natural forces operating over enormous periods of time and with considerable, though not necessarily total, uniformity. With modifications it has become the geological point of view of the twentieth century. In the early nineteenth century it stood In considerable opposition to Catastrophism, a geological approach which Interpreted the stratigraphic features of the planet as representing a succession of sudden, violent, and cataclysmic disturbances in the geologic past Interspersed between long periods of calm. These disturbances were often regarded as world wide and totally, or almost totally, lethal in their effect upon the life of the globe. The theory implies the work of forces unknown in the present era and there thus lingers about the doctrine a certain aroma of the supernatural even though not always directly expressed or avowed by its more scientific proponents. The fact that life was supposedly created anew after each such episode enhances this aspect of the theory. Essentially catastrophism represents a compromise between the Mosaic account of creation and the increasing geological knowledge of the late eighteenth and early nineteenth centuries. The biological analogue of catastrophism is Progressionism, the assumption that life has risen from simple to more complex forms throughout the successive eras of the geological past. The doctrine does not imply actual phylogenetic descent from one form to another, but rather a succession of more and more advanced creations until finally man appears as the crowning achievement. The unity of biological form is thus not the product of "descent with modification" but rather a succession of creations linked only by an abstract unity existing In the mind of God. Opposed to this point of view was the short-lived Non-progressionism of Lyell which was the biological equivalent of extreme uniformitarianism. Non-progressionism opposed the theory of successive and advancing creations by seeking to demonstrate that the higher and more complex forms of life such as the birds and mammals were actually to be found in ancient deposits. The theory was expressed somewhat ambiguously and with qualifications. It did not long survive but essentially it represents a pre-Darwinian attempt to avoid the supernaturalism so abhorrent to the uniformitarian geologists with their preference for natural rather than unknown mysterious forces. In the end Developmentalism, later to be called evolution, arose out of the merging of progressionism with the natural philosophy of uniformitarianism. This could only take place when Charles Darwin supplied, through the principle of natural selection, a natural (i.e., uniformitarian) explanation for the past changes which had taken place in the flora and fauna of the world.
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