Compare relative dating and radioactive dating
Fossils are found in a variety of rock, but most often in sedimentary rock, which forms from the accumulation of sediments.The replacement of organic materials with inorganic materials is not always complete, as DNA is sometimes preserved within the fossil.Paleoanthropologists focus much of their research in East and South Africa, because these areas have the most ideal conditions for fossilization and access to the deep layers containing the fossils.
As you move down from the surface, the layers get progressively older.
The chances of fossilization are very slim, because it requires that the remains be quickly buried and be kept in an oxygen-free environment.
Scavenger and bacterial activity must be prevented so that decomposition is limited.
The more fossilized remains available for study, the more information can be obtained and a more complete understanding achieved.
The incomplete fossil record is due in part to lack of discovery, as only some areas are the focus of excavation and investigation.