Since ancient times, Greek philosophers have tried to interpret fossils. In the 15th century, Leonardo Da Vinci claimed that the traces of a biblical deluge would not have formed clear layers. It was not until the 19th century that Charles Lyell described fossils as the remains of animals and plants that lived in another era.
Fossils are the marks of extinct species. There are divided in 3 categories :
Casts are simple mud prints, most of the time of the hard parts that need time to be decomposed.
Mummies corresponds to a complete or partial preservation of the extinct specie.
Mineralisations corresponds to a gradual transformation of the organic material into stone.. In exceptional cases, it may be the softparts.