Between the years of 17, James Hutton and William Smith advanced the concept of relative dating.Hutton, a Scottish geologist, first proposed formally the fundamental principle used to classify rocks according to their relative ages.It only sequences the age of things or determines if something is older or younger than other things.Some types of relative dating techniques include climate chronology, dendrochronology, ice core sampling, stratigraphy, and seriation.
Instead of invoking supernatural forces to explain fossils, Steno concluded that fossils were once parts of living creatures.
In 1666, a young doctor named Nicholas Steno was invited to dissect the head of an enormous great white shark that had been caught by local fisherman near Florence, Italy.
Steno was struck by the resemblance of the shark's teeth to fossils, known as "tongue stones", recovered from inland mountains and hills (Figure 11.9).
He then sought to explain how fossil seashells could be found in rocks far from any ocean.
As in the Tyrannosaurus rex Figure 11.10, fossils resemble living organisms.
The concept is considered by uniformitarian geologists to be a major breakthrough in scientific reasoning by establishing a rational basis for relative time measurements.