Editing Paleontology (section)

==Applications==
{{Life timeline}}
Paleontology both draws from and contributes to the fields of geology and biology, despite historically being dismissed as an undemanding science. Analysis and description of fossils allows the researchers to illustrate biological, geological, ecological and tectonic changes and phenomena which have implications for our understanding of science in the present. Many disciplines and areas of study interact with paleontology and overlap in some areas with the field. Through this overlap, paleontology has the ability to better our understanding of the origin, diversity and evolution of life, and can be used by other fields to investigate patterns in the fossil record.<ref name="hall2002"/> In the modern day, paleontology is viewed as important by researchers. Its study enables scientists to understand the history of life. It can explain different worlds of the past and the impact of a changing climate and biodiversity, and paleontology helps expand our understanding of both evolution and extinction. Subfields of paleontology also enable geologists to robustly establish the ages of various rock formations.<ref name="benton2020-1"/>

===History of life===
{{main|History of life}}
Paleontological discoveries have discussed the origins and history of life for centuries, with very little knowledge of life before the [[Cambrian]] for a significant amount of time. Fossils from prior to the Cambrian were limited to 2.1 billion year old fossilized [[algae]] and possibly "plants" until the discoveries of fauna in the [[Bitter Springs Group]] and [[Apex chert]] of Australia, the [[Mistaken Point Formation]] of Canada, and the [[Doushantuo Formation]] of China, all of which have significantly expanded knowledge of the [[Ediacaran biota]] that includes a range of life from microscopic single-celled organisms to macroscopic multicellular life. Fossil discoveries have also improved knowledge about the Cambrian explosion with the discoveries of multiple new [[lagerstätte]] deposits. The [[Burgess Shale]] was one of the first such deposits and has been further explored, and around 40 other Burgess-type localities are now known globally. These localities are filled with soft-bodied taxa that show the decline of the Ediacaran biota and the emergence of other kinds of [[metazoa]]n life. The refinement of Cambrian stratigraphy will also improve the understanding of these early faunas and how they changed over time.<ref name="kelley2013"/>

Through advances in paleontology many other evolutionary paths have become better understood even in more recent life. The [[evolution of birds]] is now understood to have occurred from gradual evolutionary changes in [[saurischian]] dinosaurs up to the point where it is difficult to draw a line between what dinosaurs are or are not birds. The origins of dinosaurs themselves are better understood from the discoveries of multiple near-dinosaur taxa. Discoveries within the [[Eocene]] of fossil mammals have allowed for the [[evolution of whales]] to be nearly completely understood, with the fully terrestrial [[mesonychid]]s becoming gradually [[semiaquatic|amphibious]] before becoming aquatic swimmers. Relatives of modern whales such as ''[[Basilosaurus]]'' were obligate swimmers, but even then had not developed the [[bauplan]] of modern [[cetacean]]s that occurred over further gradual evolution. The evolution of reptile groups such as ichthyosaurs and [[turtles]], while still controversial, is much better understood with finds such as the early incompletely-shelled turtle ''[[Proganochelys]]''.<ref name="kelley2013"/>

[[Human evolution]] is also much better understood from progress in paleontology, including both the evolution of [[hominid]]s from basal [[primates]] as well as the speciation and origins of humans within the hominids. Fossils of ''[[Australopithecus]]'' and ''[[Ardipithecus]]'' show that humans never transitioned through an [[ape]]-like stage, instead being bipedal with adaptations for [[arboreal locomotion]]. ''Adripithecus'' is known from lowland [[forest]] environments, and not grasslands, suggesting the origins of humanity within a variable and unpredictable habitat. The evolution of humans within the genus ''[[Homo]]'' is similarly complex and does not follow a clean linear path as sometimes described. Some species of ''Homo'' may have overlapped in time and place with others, but all show that then evolution of the genus was likely in [[Early expansions of hominins out of Africa|Africa]]. Advancements and new discoveries have also shown that the [[neanderthal]]s were a complex society with the use of [[tools]], [[clothes]], and having their own [[mythology]]. [[DNA]] from neanderthals and humans show substantial differences, but also that there was interbreeding between populations.<ref name="kelley2013"/>

===Extinction events===
{{main|Mass extinction}}
{{multiple image
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|image1=Main floristic types from the Maastrichtian - journal.pone.0052455.g007-left.png
|image2=Main floristic types from the Danian - journal.pone.0052455.g007-right.png
|footer=Illustrations of the main floral ecosystem before (left) and after (right) the K-Pg extinction
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The idea of a mass extinction has been around since the beginning of paleontology and is generally accepted as true events that drive the evolution of life. However, the question of what makes an extinction event a "mass extinction" is still uncertain. On the scale of geologic time, mass extinction events happen rapidly, and such rapid events can be caused by both gradual environmental processes and large-scale catastrophes. A notable exception to this rule is the [[Cretaceous-Paleogene extinction event]], which is believed to have been caused by an [[asteroid impact]] which caused global [[wildfires]] and a disruption of the [[nutrient cycle]] in the ocean. If this is the case, it would be an unprecedentedly rapid extinction event, occurring over the course of one or a few years. However, even this extinction's cause is debated. Some have suggested that it was caused by [[marine regression]] or [[volcanism]] that occurred near or at the same time as an impact. No other extinction events can be linked clearly with an extra-terrestrial cause. [[Glaciation]] and subsequent [[global warming]] has been suggested as a cause for the [[Late Ordovician mass extinction]], and the volcanic activity of the [[Siberian traps]] [[large igneous province]] has been suggested as the primary cause for the [[Permian-Triassic mass extinction]]. The causes of the [[Late Devonian mass extinction]] and the [[Triassic-Jurassic mass extinction]] remain mostly uncertain to this day.<ref name="kelley2013"/>

The period of ecological recovery following a mass extinction is also a significant time for biodiversity and [[adaptive radiation]]. The term "disaster species" has been applied to the organisms that follow an ecological disruption, and there are many known from the fossil record. Following the Cretaceous-Paleogene extinction, there is a large spike in the abundance of fossil [[fern]]s that is interpreted as an early post-extinction flora that would later be overtaken by different floral communities. There is a similarly rapid diversification of small, [[generalist species|generalist]] mammals for the first 3 million years before more diverse faunal communities evolved. However, not all mass extinctions have similarly rapid diversification events. The recovery period following the Permian-Triassic extinction took up to 10 million years. The recovery of ecosystems from mass extinctions involves the evolution of novel ecological relationships between groups of animals that would not have been possible in the pre-extinction ecosystem.<ref name="kelley2013"/>

===Biostratigraphy===
{{main|Biostratigraphy}}
[[File:Western Europe latest Oligocene ruminant biostratigraphy evolution.png|thumb|left|Biostratigraphy of [[ruminant]]s from the [[Oligocene]] of western Europe]]
Fossils have been used for stratigraphic correlation since at least the 18th century. Observed changes in the fossils found through geologic time led to the principle of [[ecological succession]], however this study was not elaborated on until the 1960s. The first and last appearance of a taxon in the fossil record can be used to compare the relative ages of different [[lithography|lithographic]] sections of sediment. This principle allows for relative ages of different sediments to be determined more precisely. These "[[index fossil]]s" are combined with measurements of [[volcanic ash]], paleomagnetic reversals, or pre-dated sediments to make precise measurements of geologic time.<ref name="kelley2013"/> For example, the [[Jurassic Period]] was named and defined based on ten main subdivisions identified through the English and French assemblages of [[ammonites]], some of which are still in use today.<ref name="ogg2012"/> Biostratigraphy is also applied to the analysis of [[stratotype]] sections and boundaries of geologic time units. It can also use the first or last appearance date of a taxon to establish time periods that are independent of their constituent strata.<ref name="kelley2013"/>

The geologic time scale is based primarily on the biostratigraphy (correlating strata) and equivalent biochronology (correlating times) of the appearance and disappearance of various fossil taxa. Some factors can introduce uncertainty into this process including the quality or quantity of sampled fossils. Different graphical and numerical methods are used in the construction of the geologic time scale. Even the [[Ediacaran]], which is poorly represented through fossils, can be assessed using biostratigraphy in combination with [[chemostratigraphy]] and absolute dating.<ref name="narbonne2012"/> The biostratigraphy of the [[Ordovician]] and [[Silurian]] is based primarily on fossils of [[graptolites]] and [[conodonts]].<ref name="cooper2012"/> Other common groups used in zonation include ammonites, [[foraminifera]], and [[palynology|plant pollen]], where it is preserved.<ref name="davydov2012"/>

===Classification===
{{main|Evolutionary taxonomy}}
[[File:Tree of life by Haeckel.jpg|thumb|[[Ernst Haeckel]]'s "tree of life", illustrating an early understanding of how evolution relates to classification]]
The adoption of phylogenetics into paleontology may be one of the most significant changes in evolutionary biology. Biological classification through phylogenetics is able to [[quantitatively]] describe the relatedness of organisms through reconstructions of evolutionary trees. Phylogenetics was first applied to the fields of [[entomology]] and [[ichthyology]], winning favor after extensive debates. Phylogenetic systematics is able to test and retest hypotheses of classification, with results being displayed in the form of [[cladogram]]s. The broad adoption of phylogenetics also coincided with the advent of molecular biology, with computational analyses able to combine the two advancements and create phylogenetic trees based on the genetics of organisms. Classification systems have also shifted in favor of phylogenetics, with the [[Linnean classification]] scheme being recognized as an imperfect method of organization that resulted in the general abandonment of most [[taxonomic rank]]s due to their inconsistency and lack of true description of evolution.<ref name="kelley2013"/>

Further applications of classification in paleontology include more focused issues targeting the distinction between [[microevolution]] and macroevolution. Microevolution is the interpretation of how evolution impacts the ability of single individuals to survive over others, while macroevolution focuses on the ability of species to survive over others. While some viewpoints believe that microevolution and macroevolution are separate processes, with morphological change arising from speciation rather than gradual [[anagenesis]] of a population, others believe that all scales of individuals and species are affected by natural selection. The clearest examples of evolution into species arises from geographic isolation, but there is an ongoing discussion around the importance of biotic versus [[abiotic]] factors in evolution.<ref name="kelley2013"/>