Fossils have been interpreted in various ways, according to the prevalent thought of the age. The very term "fossil" has changed in meaning, coming from the Latin fossilis, 1 as something dug up, to the more specific modern meaning as evidence of earlier life. The changing views about fossils were informed by and shaped the course of wider geological thought.
In 1565, Conrad Gesner finished his book On Fossil Objects2, which is notable for three innovations which with hindsight can be seen as invaluable in the development of paleontology and historical geology. Firstly, it includes a great number of illustrations, which Gesner himself explained as useful "so that students may more easily recognize objects that cannot be very clearly described in words."3 Secondly, it is the first time that a collection of "fossils" is referred to plainly, and Gesner went so far as to include the catalogue of a friend's collection in his volume.4 Thirdly, Gesner's book is the first with a clear motivation to increase scholarly communication about "fossils".5
In other natural sciences of the time, these innovations were the standard. Gesner's work is unusual only in the sense that he reformulates the way "fossils" are considered, to match contemporary flora and fauna studies. Dry gardens and preserved animals were collected for study, much indeed as were antiquities. With plants and animals it was a second best attempt to contemplate non-local specimens; for "fossils" such collections were imminently suitable. In addition, stimulating interest in fossils was a more important task, in the sense that sites for their collection were much more localized. Unlike collecting a buck, "fossils" might be turned up only in the course of other work, such as quarrying or preparing a foundation, requiring immediate collection by someone already there.
While Gesner, and Agricola before him, were important in the development of the study of fossils, we must not confuse matters by projecting questions not then formulated back into their work. While they did seek a more sophisticated method of organizing the subject than mere alphabetical order, at the time this was not thought of in terms of separating those "fossils" of organic from those of inorganic origin. Partly this was a result of the difficult nature of the "actual" fossils with which they were dealing. Between strange preservation and bizarre creatures unknown in life, what we now know was much less than obvious. From Gesner's juxtaposition of certain fossils with modern creatures, it is reasonable to believe he thought that some of his "fossils" were the remains of once living creatures.6 This is especially compelling with regards to glossopetrae (tongue stones) and sharks' teeth, and is also suggested by presentation of a fossil crab with a modern crab. Yet it is one thing to believe some "fossils" are the remains of animals, and another to consider the matter of major import. Both the Neoplatonism of Gesner's time and the reformed Aristotelianism that followed provided explanations for the similarities between "fossils" and other objects, which fit with their understanding of the universe. The Neoplatonist saw the universe as an intertwined web, with correspondences between higher and lower levels of creation. It was just as natural that some stones look like sea urchins as it was that mandrake have the form of man, or starfish resemble heavenly bodies. While the Aristotelians struck a sharper line between the living and non-living world, they still considered spontaneous generation possible, nor were they opposed to "seed" developing simulacrum of organisms within the earth out of stony materials. It is important to understand that this "mystical" interpretation was not a result of religious conservatism, but was the product of two dominate and 'progressive' frameworks. 7 Before a modern explanation of fossils could become tenable, the very understanding of the universe had to change.
In order for it to become acceptable to consider a certain class of "fossils" as organic remains, proof against in situ production was required. The most important issue is not so much how this was proved, but why. Steno can be considered to have started the revolution through his digression on tongue stones in his The head of a shark dissected. and continued it in Of Solids Naturally Contained within Solids. Robert Hooke was also a defender of the once organic nature of certain fossils, largely as an outgrowth of philosophical views.8 Simply put, he could see no purpose to be served by fossils not being the remains of the creatures they seemed to imitate. Taking the universe to be sensible, and no longer holding to the principle "as it is above, so is it below", the only explanation for identity of form was identity of function. "To ascribe to Nature the production of truly fibrous bones is the same as saying that Nature can produce a man's hand without the rest of the man."9
With hindsight we could say that Hooke and Steno and various other contemporaries were right, but the matter is much more complex. Between Hooke and us the matter goes through many twists and turns. Like Mendel, Hooke and his work play little part in the main course of the development of a science of paleontology and historical geology, being "rediscovered" once it could be pointed to as an "ancestor" to the winning theory. Two major problems proved to be stumbling blocks. On the one hand the method of deposition posited did not account for all the evidence.12 Desmarest is perhaps the best paternity candidate for vulcanism, a position mostly noted for explaining basalt through volcanic activity as opposed to sediments being melted through coal veins igniting underground. The line of thought founded by Hutton and further elucidated and supported by Playfair rounds out the collection with the plutonist position, which is separated from that of the vulcanists through greater motive force being attributed to molten activity. While Hutton's theory has been considered the "winner" of this contest in the writings of geologists such as Geike, Werner's explanation of sedimentation is closer to the truth than Hutton's positation of heat.13 What does this have to do with fossils? The controversy simply slided out of prominence because of the interesting work of Cuvier and Brongniart.
Cuvier was basically a zoologist and his work with fossils can be interpreted in that light. His ability to reconstruct and classify fossil animals on the basis of a few broken bones was legendary.14 Brongnairt's curiosity was piqued regarding how this menagerie stacked up, and together Brongniart and Cuvier produced a stratigraphic map of the Paris basin.15 Two things became clear as a result of this work. Werner's divisions, based as they were on inclination, were wrong. The fossils of the flat-lying Paris Basin soft chalk matched those of parts of the steeply-dipped Alpine limestones. Secondly, it became evident that there had been extinctions and that the lower levels were less taxonomically advanced.16 Paradoxically, Cuvier was strongly opposed to current chain-of-being theories, and came into bitter conflict with Lamarck and Saint-Hilaire. Contemporaries considered Cuvier the clear winner in what can be considered a classic of scientific personal warfare; yet he was wrong. Fossil species are in fact predecessors of modern forms.
Cuvier considered the reason for the extinctions to be sudden inundation and retreat by waters. His evidence was the presence of freshwater and also terrestrial fossil-bearing strata, and the occasional discovery of frozen mammoth carcasses in glaciers. This is a catastrophic theory, and also actualist.
A second major controversy of the eighteenth-century, and one still at work during the nineteenth-century, was that between the catastrophists and the uniformitarians. A major problem in the writing of science history has been a confusion of what the positions were. Some of this comes from baiting arguments, where one side would accuse the other of being responsible for the vaguely similar writings of a crank. The more difficult factor is that there is both a method and a system of uniformitarianism.17 The method of uniformitarianism is actualistic, taking study of present processes and using that knowledge to make interpretations of the past. Yet it is possible to be actualistic without concluding that the processes at work now are the only processes that have ever been at work. Considering the natural forces Europeans knew, it was perfectly tenable that additional power was needed for valley and mountain construction. This catastrophic view did not imply a miracle; simply that much as a clock winds down, the earth no longer had the vigorous action of bygone times. The theory of uniformitarianism, on the other hand, holds that the forces of the present are those of the past. It is based "upon the supposition that the operations of nature are equable and steady"18. Empirically, there is no reason to hold the one above the other. However, heuristically there is a major difference, for if you hold that the powers of the present are those of the past then the past is imminently knowable and sensible. It allows events to be causal and not coincidental, which can be seen in the light of being purposeful. Playfair's argument in Illustrations19 regarding the cutting of valleys by the rivers that flow in them is persuasive in a context of a "nonmystical" world. A Neoplatonist or Aristotelian would be able to present an equally rational explanation according to their understanding of the universe. It is a question of what sort of answer provides meaning, which ultimately depends on the context. From uniformitarianism, Hutton produced the concept of deep time. While there were many volleys back and forth between catastrophic and uniformitarian theories, it was deep time that became the deciding matter.
Deep time was difficult for many people to accept for a variety of reasons. One reason was it increased the age of the earth beyond that included in Scripture, which was considered a reasonable record of man's history. It is important to understand that this was not a simple case of religious intolerance of science, as it has often been presented. This was a milieu where the history of the earth and the history of man were but strands in a single yarn. In addition, time was made nearly infinite, which was philosophically a problem in that any contradiction or shortcoming could be referred to time and swallowed up. In addition, the realm of astronomy and physics had a problem relating to heat.
William Thomson, better known as Lord Kelvin, considered that the age of the earth according to Hutton's deep time was greater than the possible longevity of the sun. From his calculations, the sun would have burned out long before even a fraction of what uniformitarians gave as the age of the earth. In addition, he could not see how the heat gradient of the earth could be at current levels if the earth had such an extreme age. According to his estimates, the earth was 98 million years old; indeed it could be as little as 20 million or as much as 400 million years old.20 Of course, the problem was a matter of presuming that all the information needed to make an estimate was known. Kelvin's estimates were made previous to the understanding of the power of the atom, which was the source of the missing heat. Interestingly, the same understanding that invalidated Kelvin's claims against deep time proved to be what was needed to produce absolute dating.
I think it is worth noting that science is a product of its time, like all other human constructs. Unlike how the Victorians presented it, the history of science is not built of the Right Answers. Science is judged according to the paradigm of the time, which in the end shifts because its Right Answers somehow contradict themselves. For this reason, the "failures" are just as important, if not more so, than the "successes"; they indicate the path taken to where we are now, and how that road was made.
