Eozoön Canadense "The Dawn Animal of Canada" Author(S): Charles F
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Eozoön Canadense "The Dawn Animal of Canada" Author(s): Charles F. O'Brien Source: Isis, Vol. 61, No. 2 (Summer, 1970), pp. 206-223 Published by: The University of Chicago Press on behalf of The History of Science Society Stable URL: http://www.jstor.org/stable/229975 Accessed: 16-04-2017 23:08 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/229975?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms The History of Science Society, The University of Chicago Press are collaborating with JSTOR to digitize, preserve and extend access to Isis This content downloaded from 150.135.211.246 on Sun, 16 Apr 2017 23:08:20 UTC All use subject to http://about.jstor.org/terms Eozoon Canadense "The Dawn Animal of Canada" By Charles F. O'Brien* I 17OZOON CANADENSE, "the dawn animal of Canada," was found in the Pre- Lcambrian rocks of eastern Canada in 1858. The discovery startled the geological world, since at the time few paleontologists believed that such metamorphic rocks could preserve fossils or even that life could have existed so long ago. In fact, what we now call Precambrian was then commonly designated by the term Azoic-lifeless. It is not surprising, then, that the authenticity of Eozoon canadense was disputed. The ensuing controversy lasted for nearly fifty years and developed into one of the most contentious issues in nineteenth-century geology. While the inorganic nature of Eozoon has long been established and Eozoon is no longer of scientific interest, the controversy has significance for the history of science. It provides an example of the manner in which every aspect of nineteenth-century paleontology was scrutinized for its bearing on evolution. It is also a classic case of the confrontation of younger specialists with each other and with the older generation of broadly trained "naturalists." There were two chief reasons for the persistence of the dispute. Most obvious and most important was the inability of early paleontology to settle the matter. The second reason, seldom stated by the disputants, was the significance of Eozodn in the larger issue of derivation of species. For, were Eozoon proved to be organic, evolutionists would be confronted with the most impressive of all gaps in the paleontological record, a gap that would give pause to even the most ardent evolutionist. On the other hand, if this gap were successfully explained or overcome by the finding of subsequent forms related to Eozoon, the evolutionists could rejoice in having found, at the earliest date of known animal life, the simplest form of life, a form reasonably akin to the "one primordial form" of Darwin's speculation.' In short, there was something at stake for both sides in the greater scientific controversy. Darwin himself was interested in Eozoon and its promise for his position. He intro- duced Eozoon into the fourth edition of The Origin of Species: "After reading Dr. Carpenter's description of this remarkable fossil, it is impossible to feel any doubt regarding its organic nature.'2 Darwin cited Eozoon in his famous tenth chapter, "On * Clarkson College of Technology, Potsdam, Charles Darwin:A Variorum Text (Philadelphia: New York 13676. Univ. of Pennsylvania Press, 1959), pp. 28-31, 1 Charles Darwin, On the Origin of Species, 515. (In the 6th and final edition, this sentence facsimile of the 1st ed. of 1859 (Cambridge: was altered to read: "The existence of the Harvard Univ. Press, 1964), p. 484. Eozoon in the Laurentian formation of Canada is 2 Morse Peckham, ed., The Origin of Species by generally admitted"; ibid., p. 515). 206 This content downloaded from 150.135.211.246 on Sun, 16 Apr 2017 23:08:20 UTC All use subject to http://about.jstor.org/terms THE DAWN ANIMAL OF CANADA 207 the Imperfection of the Geological Record," as an indication that gaps in the pale- ontological record were being filled, and that as the origins of life were pushed back, natural selection became a more reasonable mechanism of evolution. 3 Eozoon presented a difficult challenge. It occurred in rocks that were so old and so highly metamorphosed that paleontologists had previously doubted even the possi- bility of finding organic remains in them. Furthermore, the most ardent supporters of the organic origin of Eozodn admitted that their best specimens were so thoroughly altered that the details of organic structure were difficult to discern. On the other hand, when those who insisted that Eozoon was a mineral substance looked into their microscopes, they did not see even traces of organic structure. They saw instead a curiously regular arrangement of minerals; such an arrangement, they said, was un- usual but not unprecedented. However, just as the supporters of Eozoon persistently failed to produce the unassailable specimen, the opponents were unable to establish any mineralogical sequence which would successfully explain the particular form and composition of Eozoon. In the absence of conclusive evidence on either side, the con- troversy dragged on for almost thirty years. It was not until the 1890s that the issue was decided in favor of the inorganic origin of Eozoon. II Eozoon began its checkered career in 1858 when a collector for the Geological Survey of Canada brought some unusual rocks to Sir William Logan, the director of the Survey. These specimens came from the Grand Calumet limestone on the Ottawa River. Logan, who was not a paleontologist, recognized the similarity between these specimens and some rocks brought to him some years earlier from the Burgess lime- stone near Perth, Ontario. The similarity consisted in the alternation of concentric layers of siliceous and calcareous compounds. What attracted Logan's attention was the fact that the particular siliceous and calcareous compounds differed in the two specimens. The Grand Calumet specimen was composed of crystallized pyroxene and carbonate of lime; the Perth specimen of loganite and dolomite. The presence of the same form with different minerals led Logan to speculate that the specimens were really fossils with different in-fillings. 4 Logan displayed these specimens at the meeting of the American Association for the Advancement of Science in 1859 and brought them to England in 1862. However, microscopic analysis failed to reveal any evidence of organic structure, and Logan left England with few believers in the organic origin of Eozoon.5 Little was done with Eozoon until 1864, when Logan observed similar forms in the Grenville limestone near Ottawa. This time microscope slices were prepared, and the alleged organic structure 3 Charles Darwin, On The Origin of Species Canadense," American Journal of Science, 1865, (6th ed., New York :Appleton, 1873), p. 287. 2nd ser., 40:344-362 (this article appeared 4 William Logan, "On the Occurrence of anonymously but is credited to Dana in John M. Organic Remains in the Laurentian Rocks of Nickles, Geologic Literature on North America, Canada," Quarterly Journal of the Geological Washington:GPO, 1923, pp. 1-2, 271). The only Society ofLondon, 1865, 21:45-48. Other accounts secondary account is contained in George P. of the finding of Eozoon include: William B. Merrill's The First One Hundred Years of Carpenter, "On the Structure, Affinities and American Geology (New Haven :Yale Univ. Press, Geological Position of Eozoon Canadense," 1924), pp. 564-579. The Intellectual Observer, 1865, 7:278-302, and James Dwight Dana, "On the History of Eozo6n 5 Carpenter, "On the Structure," p. 286. This content downloaded from 150.135.211.246 on Sun, 16 Apr 2017 23:08:20 UTC All use subject to http://about.jstor.org/terms 208 CHARLES F. O'BRIEN was noticed. The slices were then brought to J. William Dawson, the Principal of McGill University and a prot&ge of Sir Charles Lyell. Dawson was already well known for his classic study, Acadian Geology. The McGill geologist confirmed the presence of organic remains and identified the fossil as a foraminifer, hundreds of times larger than any of the microscopic Foraminifera yet found6: I have had the happiness to submit these remarkable specimens to microscope examina- tion, at the request of Sir W. E. Logan, and have arrived at the conclusion that they are of animal nature, and belong to the very humblest type of animal existence known, that of the Rhizopods, though they far outstrip in magnitude any known modern representative of that group. The discovery of this remarkable fossil, to be known as the Eozo6n Canadense, will be one of the brightest gems in the scientific crown of the Geological Survey of Canada.7 Dawson's identification, confirmed by the leading authority on Foraminifera, William B. Carpenter, was accepted by most naturalists. The accounts of the finding of Eozodn printed in various journals clearly implied widespread acceptance of the organic origin of Eozodn. James Hall of the New York Geological Survey thought Eozodn organic. Hall wrote to T. Sterry Hunt, a mineralogist at McGill who, with Dawson, insisted on the authenticity of Eozodn: "It [Eozodn] is the greatest discovery in geology for half a century at least."8 Dana's account of the history of the discovery implied agreement with Dawson and Carpenter.