Editing Paleontology (section)

===Extinction===
{{main|Extinction}}
[[File:Edwards' Dodo.jpg|thumb|left|The [[dodo]] of [[Mauritius]] which has gone extinct in modern times]]
Fossils have been documented from at least as far back as [[Ancient Greece]]. However, the belief of philosophers including [[Plato]] and [[Aristotle]] was that anything that existed had existed forever and would exist forever, or was along a continuum of perfection without any gaps. As a result of this fundamental belief, evidence of extinction was ignored or explained away by naturalists for most of recorded history. It was not until the work of Cuvier with the publication of his ''Recherches sur les ossemens fossiles'' (or ''Investigations on fossil bones''), that extinction was understood and considered the principal basis for paleontology as a science. By the early-mid 19th century, it was no longer controversial that fossil animals existed in a sequential order and as a result that fauna and flora were changing over time. Cuvier himself denied that there was any direct continuity from any of these fossils to organisms alive in the present day, and thus that all were extinct. However, he also did not believe the idea that any presently extant organisms had been alive in the past. Instead he believed that over time great "revolutions" occurred in which all living organisms went extinct, and new ones arose, which was consistent with belief in the Biblical Flood. It was not until English naturalist [[Charles Darwin]] suggested that extinction and evolution both occurred together, that a full explanation could be given for changes of life over time. The fossil record showed that there was not a predetermined length of time for which a particular organism (or group of organisms) existed, and it also gave evidence for periods where a large percentage of organisms went extinct at once, which could be the result of mass extinction events.<ref name="simpson1985"/>

Extinction can be seen as the final step of evolutionary change for any species. While modern biologists assess rates of extinction can be through the presence or absence of [[species]] in nature, paleontologists are limited in their understanding of this by the inherent rarity of fossils and the incompleteness of the fossil record. These difficulties make it more challenging to infer what [[extinction rate]]s were in the past, and can make it difficult to differentiate between a true extinction and a "pseudoextinction", where one species evolves directly into another. Extinction of a species can occur from a variety of causes, and the intensity of extinction rates vary significantly over time. At least five mass extinction events are recognized to have occurred during the history of Earth, and it is also possible that the Earth is currently undergoing a [[sixth extinction]] as a result of human activity. However, mass extinction events only account for a small percentage of total species extinctions. Most extinctions occur as a result of other causes at differing times throughout Earth's history, which is sometimes called the [[background extinction rate]].<ref name="purvis2000"/> For most organisms in the fossil record, it is impossible to determine the cause of extinction in particular or even general cases.<ref name="simpson1985"/>