Seeking an alternate explanation, other writers proposed that the fossils had formed within the rocks as a result of mysterious forces.
In other words, fossil shells, bones, and teeth were never a part of a living creature! For Steno, the close resemblance between fossils and modern organisms was impossible to ignore.
In another example: lets assume that we have outcrops of a granite with very distinct texture in one area, and a sedimentary sequence close by, but no direct physical contact between the two rock units.
He then sought to explain how fossil seashells could be found in rocks far from any ocean.The reason was that the fossils of clams, snails, and other marine animals were found in tall mountains, miles from any ocean. Some religious writers believed that the shells were washed up during the Biblical flood.But this explanation could not account for the fact that fossils were not only found on mountains, but also within mountains, in rocks that had been quarried from deep below Earth's surface.Sedimentary rocks are deposited one on top of another.Therefore, the youngest layers are found at the top, and the oldest layers are found at the bottom of the sequence.