Fracastoro Develops His Theory of Fossils Summary

  • Last updated on November 11, 2022

Fracastoro, through scientific observation, was one of the first to theorize that fossils are the remains of once-living organisms, the remnants and traces of the history of life on earth.

Summary of Event

Prior to the speculations of Girolamo Fracastoro, fossils were viewed as inorganic products of the mineral kingdom formed in situ. During the Middle Ages, definitions of fossils were based on assumptions made by Aristotle, who believed fossils resulted from the petrified and then sedimented remains of an abundance of organisms that came to life through spontaneous generation. Fossils, believed to be formed by many different forces, were classified as oddities of nature, carved stones, or mineral concretions that were by-products of the motions of the stars, seminal vapors, or unidentified petrifying or plastic forces. To further compound the confusion, religious dogma of the time designated all fossils to be relics of Noah’s ark and the great flood. Fracastoro, Girolamo Leonardo da Vinci Leonardo da Vinci Gesner, Conrad Fracastoro, Girolamo

By the early sixteenth century, three questions came to dominate discussions about fossil origins: Are fossils inorganic? Are they relics of Noah’s ark? Are fossils the product of a long history of past life on Earth? Fracastoro and his contemporary, Leonardo da Vinci, favored the theory that fossils represented a record of a long history of life on Earth.

Da Vinci’s notebooks contain many acute and accurate observations of living mollusks and their ecology and notes on the process of sedimentation. Da Vinci recognized that similarities between living marine life and fossils were so exacting that a causal explanation was necessary to account for a fossil’s existence. Da Vinci noted fossils were preserved in various stages of growth and exhibited markings of a life history on their surfaces such as bore holes and parasites. He further speculated that fossils were embedded in stratified rock and were consolidated from “drying out.”

Fracastoro was the sixth of seven sons born to a patrician Veronese family. As an adolescent, he was sent to Padua, Italy, for formal education. Fracastoro studied literature, mathematics, philosophy, astronomy, and medicine. After graduating in 1502, he became an instructor of logic at the University of Padua. In 1508, he left the university and returned to Verona to establish residency and dedicate himself to his studies and the practice of medicine.

Fracastoro maintained a villa in Incaffi, on the slopes of Monte Baldo, a location that became a gathering place for philosophical and scientific meetings attended by many leading religious, scientific, and philosophical thinkers of the time. These gatherings expanded Fracastoro’s cultural interests into philosophy, the liberal arts, and the natural sciences. It was probably during his stays at Monte Baldo that Fracastoro became familiar with fossils and the significant scientific and philosophical questions that their existence brings to light.

In 1517, Fracastoro observed fossil mollusks and crabs that had been discovered in the foundations of buildings in Verona. He believed they were the remains of once-living shellfish buried after the landscape changed over time, and he argued against suggestions that they were embedded because of a biblical flood or because of a molding force from within the Earth. Fracastoro’s interpretation of fossils as organic remains embedded during the continual process of geological and geographical change was clearly secular. He suggested that the existence of fossils could be explained completely in terms of natural law. It is important to note, though, that Fracastoro was an Aristotelian thinker and that it was acceptable to define fossils also as spontaneously generated. Fracastoro referred to the process of spontaneous generation to explain some of the more difficult fossil samples he observed.


Because Leonardo da Vinci recorded his theories regarding the marine origin of fossils into his famous coded private notebooks, his ideas had little to no influence on later researchers of fossils. Fracastoro’s theories of fossils reflected a similar viewpoint—fossils that looked like modern marine life represented past marine life—and his ideas, made public, would inspire Conrad Gesner’s De rerum fossilium, lapidum, et gemmarum maximè, figuris et similitudinibus liber De rerum fossilium, lapidum, et gemmarum maximè, figuris et similitudinibus liber (Gesner) (1565; on the shapes and resemblances of fossils, stones, and gems); Andrea Chiocco’s Musaeum Francisci Calceolari Veronensis (1622), which quotes Fracastoro; and Nicolaus Steno’s pivotal work De solido intra solidum naturaliter contento dissertationis prodromus (1669; The Prodromus to a Dissertation Concerning Solids Naturally Contained Within Solids, 1671). Though Steno does not quote Fracastoro in his publication, most scholars believe he was familiar with and influenced by Fracastoro’s ideas.

Steno’s work, considered the founding text of modern geological science, examines the general question of how one solid (fossil) could be contained within another solid (rock strata). It also contests the biblical Noachian deluge explanation of fossils. Steno believed that strata were formed by the deposition of sediments in water; what looked like organic remains found within stratified rock must represent once-living organisms that existed in water at the time the sediments were deposited. Through direct observation, Steno also theorized that the process of sedimentation takes place at a slow rate over long periods of time. This was a revolutionary proposal not only for the formation of fossils but also for the formation of rock strata.

Fracastoro’s contribution to the beginnings of modern geological and paleontological thought are indeed significant, but his greatest contributions to the scientific revolution came from two major works in the field of medicine, specifically epidemic diseases. Fracastoro is credited with publishing the first insights into the spread of contagious disease by personal contact and through inhaling airborne contagions and by indirect contact through items such as clothing. In 1530, Fracastoro published a thirteen-hundred-verse poem entitled Syphilis sive morbus Gallicus (Syphilis: Or, A Poetical History of the French Disease Syphilis (Fracastoro) , 1686; better known as Syphilis), a mythical tale discussing the possible causes and diffusion of the sexually transmitted disease syphilis; Syphilis;Fracastoro on by 1547, he had published a formal treatise on the subject entitled De contagionibus et contagiosis morbis et eorum curatione libri tres (1546; De contagione et contagiosis morbis et eorum curatione De contagione et contagiosis morbis et eorum curatione (Fracastoro) , 1930). The publication of this work assured Fracastoro a lasting place in the history of epidemiology. In the book, he provides detailed descriptions of numerous contagious diseases and speculates on how each is spread. Fracastoro further speculates diseases are spread by “seeds.” The idea of “seeds” causing disease would become the basis for modern germ theory some three hundred fifty years later.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Gould, Stephen Jay. “Pathways of Discovery: Deconstructing the ’Science Wars’ by Reconstructing an Old Mold.” Science 287 (January 14, 2000). A brief discourse on the history of interpreting fossils and the paths of logic required in making the connections between empirical observation and logical conclusions to their origins.
  • citation-type="booksimple"

    xlink:type="simple">Harrington, J. W. Dance of the Continents: New York: V. P. Tarher, 1983. A fine, general geology book including passages on the lives and philosophies of early geological thinkers and innovators.
  • citation-type="booksimple"

    xlink:type="simple">Lederberg, Joshua. “Pathways to Discovery: Infectious History.” Science 288 (April 14, 2000). A history and descriptive outline of the early interpretation of infectious diseases, including the pivotal role played by Girolamo Fracastoro.
  • citation-type="booksimple"

    xlink:type="simple">Rudwick, M. J. S. The Meaning of Fossils. New York: Elsevier, 1972. A good, general reference on the history of paleontology and the roles played by early scientists in the field.

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