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Given an ancient age of the earth, and the evidence of forms of life dramatically different from present-day species, naturalists by the 1800s began to envision a past history of the earth. Physical processes had molded and formed its structure, but what about the species of a past world?
Georges Cuvier established a new science of comparative anatomy, building principles of functional morphology for the interpretation of fossil animals. He became a master of reconstruction, reading the evidence of the bones. By comparison to modern animals, he deduced principles of functional design; that allowed him to determine an animal's appearance, ecology, and even behavior. Laws of nature could be seen in the useful structures of animals.
In this figure, Cuvier is illustrating the similarity of two modern forms of sloth (top) with a fossil find from Paraguay. The conclusion was exciting, in following orderly laws of nature, but unsettling: ancient forms were extinct, similar enough to be classified in modern groups, but distinct enough to be separate species.
That there had been no evolution, connecting ancient and modern forms of such similarity, was evident in the lack of changes in the 3000 years since this Egyptian ibis was mummified for a tomb. Cuvier's analysis compared the remains to modern birds, and found identity. With evolutionary transformation inconceivable, a sensible conclusion was that the layers of rock and extinct species were evidences of separate creations. Each layer was the remains of a distinct epoch of life, with its distinct assemblage of species. The history of life was a record of revolutions.
But was this evidence of progress? Cuvier denied any progression or directional history of life. The similarities of form were a necessity of structural rules for good functional design; natural origins of species, or descent, undermined such functional stability. But other naturalists were not so swayed by the necessity for stability, and Cuvier engaged in highly publicized controversy with new "transmutationists," Geoffroy St. Hilaire and Lamarck.
It was a highly public debate, in part because it was waged by the elite of natural history at the Paris Museum of Natural History, and in part because the public was fascinated by these fossils. Museum and private exhibits of reconstructed animals, in particular, excited the imagination and gathered a large popular audience. Evolutionary ideas were severely criticized, failing to sway most naturalists, but a public discussion of biological stability vs. progress had been opened by broad interest in the history -- and possible causes -- of past epochs of life.
The fossils appeared in strata, with the deepest layers obviously being the oldest. The ancient fossil beds held species not seen on Earth today. Moreover, the associations of fossils in each layer implied a completely distinct ecology, such as tropical climates in Europe, or ancient marine environments where today it is dry land. The theoretical solution was to see each distinct layer as evidence of a distinct epoch of life. Each came into being, all at once, as a "special creation." Each was destroyed, to be replaced by the new climate and species.
As Richard Owen, Superintendent of Natural History at the British Museum, lectured ("On the Extinction of Species; being, A Conclusion of the Fullerian Course of Lectures on Physiology, for 1859"),
"But we likewise, by these investigations, gain a still more important truth, viz. that the phenomena of the world do not succeed each other with the mechanical sameness attributed to them in the cycles of the Epicurean philosophy; for we are able to demonstrate that the different epochs of the earth were attended with corresponding changes of organic structure; and that, in all these instances of change, the organs, as far as we could comprehend their use, were exactly those best suited to the functions of being. Hence we not only show intelligence evoking means adapted to the end; but, at successive times and periods, producing a change of mechanism adapted to a change in external conditions. Thsu the highest generalizations in the science of organic bodies, like the Newtonian laws of universal matter, lead to the unequivocal conviction of a great First Cause, which is certainly not mechanical."
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