Fossils, Interpretations of

Fossils, the remains of once-living organisms or their behavior, have long been known to humankind, but interpreted differently depending on time and place. Since their first recorded discovery by ancient Greeks, Romans, and Native Americans, fossils have been explained as the remains of gods and giants, used to support notions of natural magic, treated as petrified organisms killed in Noah's Flood, and ultimately regarded as some of the strongest evidence for Darwinian evolution. The scientific study of fossils began in the 16th century and has changed dramatically, depending on the prevailing views of the scientific community and the technology available to researchers. Today, the science of paleontology is a vibrant discipline strongly integrated with geology, biology, chemistry, and other sciences.

Although fossils were discovered and often interpreted by the ancient Greeks, Romans, and Native Americans, the first rigorous and systematic studies of fossils were carried out by 16th-century European naturalists. To these naturalists, the word fossil referred to a range of natural curiosities dug from the earth, including stones, gems, and the remains of once-living organisms that comprise today's concept of fossils. Early naturalists, however, had a difficult time recognizing the organic nature of fossils, due both to philosophical constraints and to the very practical difficulty of identifying often fragmentary and eroded specimens. Several encyclopedic works, including Georg Bauer's (1494–1555) On the Nature of Fossils and Conrad Gesner's (1516–1565) On Fossil Objects, recognized the extraordinary similarity between some fossils and living organisms, but were hesitant to describe these specimens as the remains of once-living creatures. Instead, many naturalists of the time considered fossils to be the result of natural magic or a “plastic force” that could reproduce the shapes of common objects in situ in solid rock. These views were tied into an overarching natural philosophy that saw the world as a harmonious and interlocking web of affinities, guided by supernatural powers.

Although often hinted at by philosophers (including Xenophanes of Colophon and Leonardo da Vinci), the organic nature of fossils was first rigorously demonstrated by Nicolaus Steno (1638–1687), a Danish anatomist and crystallographer. In dissecting the head of a giant shark that washed up near Livorno, Steno noticed an uncanny resemblance between the creature's teeth and glossopetrae, a type of odd stone common on Malta that was thought to have curative and magical powers. While others had previously noted the resemblance, they were at a loss to explain how petrified sharks' teeth were found on land, often on mountains thousands of feet above sea level. Noting that glossopetrae resembled a modern shark tooth in every respect, Steno wrote that these stones must be the remains of once-living organisms, a conclusion he generalized to other fossils that resembled living creatures or their organs, such as bones, shells, and leaves. This conclusion was strongly supported by [Page 545]early microscopist Robert Hooke (1635–1703), who used this new instrument to examine the microscopic composition of fossils, which he found to be nearly identical to the microstructure of the living organisms they resembled.

with the organic nature of fossils now secure, most researchers at the time regarded fossils and their entombing rocks as products of Noah's Flood. However, based on field excursions in Tuscany, Steno recognized that rocks are found in layers made of different materials, which he hypothesized as representing a sequence of different events in the history of the earth. The notion of sequential periods in earth history was supported by noted French anatomist Georges Cuvier (1769–1832), whose careful comparisons of fossil sloth and elephant specimens to their modern counterparts recognized the former as distinct species. By now, exploration of the New World made it implausible that these fossil species would be found alive in an unexplored corner of the globe, indicating to Cuvier that they must have gone extinct. Up until this point, early naturalists such as Martin Lister (c. 1638–1712) and John Ray (1627–1705) regarded extinction as impossible, as it would imply imperfection in God's creation. To Cuvier, the reality of extinction suggested that earth history could be divided into distinct periods punctuated by “revolutions,” an idea that soon found support in the geological fieldwork of Jean-André De Luc (1727–1817). Furthermore, Cuvier himself carefully studied the thick rock sequences exposed in the gypsum quarries at Montmartre, and found evidence of several very different faunas of fossil mammals, which gradually became increasingly differentiated from modern faunas further back in time. Additional exploration, especially in Great Britain, revealed several distinct periods in geological history, including an era dominated by reptiles (dinosaurs, plesio-saurs, ichthyosaurs, etc.).

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