Editing Paleontology (section)

===Fossils===
{{main|Fossil}}
{{multiple image
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|image1=Onychocrinus exculptus fossil crinoid (Edwardsville Formation, Lower Mississippian; Crawfordsville area, Montgomery County, Indiana, USA) (17204172290).jpg
|image2=Palaeosinopa skull.jpg
|image3=Petrified forest log 2 md.jpg
|image4=Harpactocarcinus punctulatus HMNS.jpg
|footer=Collection of fossils (clockwise from top left): ''[[Onychocrinus]]'', ''[[Palaeosinopa]]'', ''[[Harpactocarcinus]]'', [[petrified wood]]
}}
Prior to the [[19th century in science|19th century]], the word "fossil" was used as a descriptive noun to characterize anything that had been dug out of the ground, including bones, stones, and [[gems]]. Early descriptions of what we now understand to be fossils described their appearances alongside and in the context of other [[mineral]]s, [[crystal]]s, and rocks. These early publications varied in contents of "fossils" across a wide spectrum of inorganic to organic appearances, including true fossils of differing preservation qualities, inorganic concretions, and structures with a resemblance to organisms. Over time the criteria for separating organic fossils from potentially organic or clearly inorganic materials brought about a change in the [[etymology]] of the word "fossil" itself, so accounts before the 19th century may not reflect the same use of the word fossil as modern paleontology. Both inorganic and organic fossils were illustrated in numerous books on the topic throughout the 16th century, with some attributing them to the  work of [[God]] and other suggesting applications in construction or medicine. Fossils were not believed to have been organic, but instead to have exhibited the same kind of "growth" as crystals.<ref name="rudwick1972a"/> Support for a possibly organic nature of fossils began in the [[17th century in science|17th century]], though it remained contentious as different quarries or [[strata]] yielded different fossils, which the scientists of the time did not have the context to explain. The fact that most fossils came from organisms that had never been observed alive anywhere in the world seemed to imply that these organisms were extinct, which was contrary to the belief of a perfect divine creation. Another compounding factor was that fossils of apparently marine animals were found in parts of the world that were well above [[sea-level]]. Some suggested that these fossils had accumulated in horizontal layers under the sea and that subsequent [[tectonics|tectonic activity]] had displaced them from their original positions. As these observations were made over time, it was eventually understood that fossils could be used to make inferences about the history of life from their presence or absence in particular areas over time.<ref name="rudwick1972b"/>

The fossil record is the main tool used by scientists to study the history of life and assess the diversification of life over time. Very little is known about the origins of life and the oldest life forms, and this is likely a result of the poor quality of fossil preservation in older rocks. Older rocks preserve less information on average than those deposited closer to the present, and this effect is compounded across the billions of years that life is believed to have existed.<ref name="benton2000"/> Most fossils are made up of the [[biomineralization|hard parts]] of an organism that have been [[recrystallization (geology)|recrystallized]] by minerals, preserving bone, wood, or shells in a material than can be harder or denser than in life. While the hard parts are the most likely to fossilize, [[soft tissues]] can also leave impressions on sediment before they fully [[decompose]], allowing non-mineralized parts of an organisms anatomy to be preserved. Even more rarely, a complete organism can be encased in sediment before decomposition, preserving it completely. While most fossils are [[body fossils]] (made of the actual body parts of a dead organism), some fossils can also consist of traces of the behaviour or life of organisms. This can include preserved [[burrow]]s, footprints or [[coprolites]], which are grouped together and called [[trace fossil]]s. However, only a small minority of all dead organisms will ever become fossils. Some things can destroy organisms before or even after fossilization, including [[scavenger]]s, [[decomposer]]s, or [[natural disaster]]s, and fossils can even be destroyed after they are formed by [[taphonomic]] processes. Even if a fossil survives burial, it can still be destroyed by [[weathering]] if it is exposed and not collected. The habitat of an organism can also impact its chances of fossilization. Seafloors are more likely to fossilize than land, and rivers or lakes more likely to fossilize than mountains or deserts. Fossilized [[teeth]] are very common, but are not always collected when they are found, and more complete fossils may be more likely to be collected, but they are generally rarer in absolute terms. Even after collection, fossils may not be studied for a long time. They may remain in [[museum]] storage in crates, be on display, or be otherwise unaccessible to scientists.<ref name="cowen2000b"/>