Da Vinci and petrified shells

Leonardo da Vinci and palaeontology | part 2

(Click this link for part 1)

What is the true nature of petrified shells? Background picture from Leonardo’s Codex.

Among the corpus of Leonardo’s writings, the Codex Leicester has been acknowledged as a fundamental document in the history of geology and palaeontology. Leonardo compiled the Leicester code between 1504 and 1506, with some folios added up to 1510. In folios 8 to 10, Leonardo analytically examined the subject of body fossils, tackling one of the vexing issues of his contemporaries: why do we find petrified seashells on mountains?

Leonardo answered the question by interpreting the nature of the sedimentary strata and the fossil molluscs found inside them. At the same time, da Vinci put forth a confutation of the Inorganic theory, according to which so-called petrified shells are natural curiosities that grew in the ground spontaneously.

The real nature of fossils continued to be under heated debate centuries after Leonardo’s correct assumptions. The protracted duration of the Inorganic theory is related with the cultural fundamentals of this idea. included in Aristotle’s legacy was the belief of vis plastica, a plastic force that led to an inorganic origin of fossils. This notion led to considerable speculation during the Renaissance, such as the idea that fossils were ludi naturae or sports of nature.

Vitruvian Man and a fossil shell.

At the end of the 18th century the Inorganic theory was still popular, as demonstrated by the so-called plastic virtue suggested by the Oxford naturalist Robert Plot. The Inorganic theory also influenced the idea of the Spermatic Principle—supported by Edward Lhwyd among the others—that maintained the growth of fossil objects as a response to the actions of an organic essence or seed. Such interpretations were gradually discarded by the end of the 18th century, when the nature of body fossils was definitively recognized as being the remnants of living beings from former times.

The fossil burrow (ichnofossil) Chondrites and the presumed autoportrait of Leonardo da Vinci.

Nevertheless, the true nature of ichnofossils – e.g. burrows, tracks, trails – have been misunderstood until 1900s. What was the idea of Leonardo about ichnofossils? I will explore it in the next post!

Adapted from: Baucon, A. 2010. Leonardo da Vinci, the founding father of ichnology. Palaios 25 0963251