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Nicholas Steno, portrait (ca. 1675)
Portrait of Nicholas Steno (ca. 1675).
Nicholas Steno
(1638-1686) was a Danish Catholic bishop who also worked as an
anatomist. He is recognized as a pioneer in the study of layered
sedimentary rock formations as organized sequences which could be
identified, found elsewhere, and compared. In 1667, Steno first
described in published form the principle of superposition, that
younger rock layers and their fossil contents are higher than older
ones.
This
concept of sequential layering (called Steno’s Law of Superposition)
is the most basic principle of stratigraphy. It means that both
the rock and their contents in lower layers are older than those in
upper layers, unless some later processes, such as an earthquake,
disturbed this arrangement. Since the original layering of these rocks
was horizontal (prior to any faulting or folding of the rocks), it
follows that diagonal, folded, or vertical layers have been altered
either by earthquakes or by mountain building forces such as volcanos,
which may have lifted certain formations higher than others.
Regarding
the creation of fossils, Steno well understood that as the rocks
formed, the remains of life were turned into fossils and preserved in
that layer. He explained the replacement process of
fossilization in terms of the then current belief that matter was
composed of tiny “corpuscles” (somewhat comparable to molecules). Steno
proposed that the corpuscles in sharks teeth were replaced individually
by mineral corpuscles. Thus while gradually turning from tissue to
stone, the shark's teeth retained their original form. This is not very
different from currently accepted explanations of fossilization by
mineral replacement.
The recognition that fossils derived from
originally living creatures had also previously been made by a few
original thinkers, including Leonardo da Vinci. Steno, however, with
his study of sedimentary rock formation, was the first to specifically
explain how fossils were snapshots of life at specific times in Earth’s
history, and that rock layers or strata formed slowly over time.
Together these two concepts lie at the basis of today’s paleontology
and geology
Reference:
Steno, N. 1667. Nicolai
Stenonis Elementorum Myologiae Specimen, seu Musculi Descriptio
Geometrica, cui accedunt canis carchariae dissectum caput et dissectus
piscis ex canum genere. Florentiae : ex typ. sub signo Stellae, via Bibliothèque interuniversitaire de médecine, Paris.
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