Editing Extinction event (section)

=== Breakthrough studies in the 1980s–1990s ===
[[File:LWA with Walt.JPG|thumb|[[Luis Walter Alvarez|Luis]] (left) and [[Walter Alvarez]] (right) at the [[Cretaceous–Paleogene boundary|K-Pg boundary]] in [[Gubbio, Italy]] in 1981. This team discovered geological evidence for an asteroid impact causing the K-Pg extinction, spurring a wave of public and scientific interest in mass extinctions and their causes]]
For much of the 20th century, the study of mass extinctions was hampered by insufficient data. Mass extinctions, though acknowledged, were considered mysterious exceptions to the prevailing [[Gradualism|gradualistic]] view of prehistory, where slow evolutionary trends define faunal changes. The first breakthrough was published in 1980 by a team led by [[Luis Walter Alvarez|Luis Alvarez]], who discovered trace metal evidence for an [[Impact event|asteroid impact]] at the end of the [[Cretaceous]] period. The [[Alvarez hypothesis]] for the [[End-Cretaceous extinction event|end-Cretaceous extinction]] gave mass extinctions, and [[Catastrophism#Current application|catastrophic]] explanations, newfound popular and scientific attention.<ref name="Alvarez">{{cite journal | vauthors = Alvarez LW, Alvarez W, Asaro F, Michel HV | date = June 1980 | title = Extraterrestrial cause for the cretaceous-tertiary extinction | journal = Science | volume = 208 | issue = 4448 | pages = 1095–1108 | pmid = 17783054 | doi = 10.1126/science.208.4448.1095 | bibcode = 1980Sci...208.1095A | s2cid = 16017767 | citeseerx = 10.1.1.126.8496 }}</ref>
[[File:Sepkoski 1997 extinction graphs.png|left|thumb|upright=1.4|Changes in diversity among genera and families, according to Sepkoski (1997). The "Big Five" mass extinctions are labelled with arrows, and taxa are segregated into Cambrian- (Cm), Paleozoic- (Pz), and Modern- (Md) type faunas.]]
Another landmark study came in 1982, when a paper written by [[David M. Raup]] and [[Jack Sepkoski]] was published in the journal ''[[Science (journal)|Science]]''.<ref name=Raup/> This paper, originating from a compendium of extinct marine animal [[Family (biology)|families]] developed by Sepkoski,<ref name=Sepkoski_1982>{{cite report |author=Sepkoski, J.J. Jr. |year=1982 |title=A compendium of fossil marine families |series=Milwaukee Public Museum Contributions in Biology and Geology |volume=51 |pages=1–125 |url=https://www.mpm.edu/sites/default/files/files%20and%20dox/C%26R/library/bio-geo/%23051%20MPM%20Contributions%20in%20Biology%20and%20Geology%20Number%2051.pdf }}</ref> identified five peaks of marine family extinctions that stand out among a backdrop of decreasing extinction rates through time. Four of these peaks were statistically significant: the [[Ashgillian]] ([[End-Ordovician extinction event|end-Ordovician]]), [[Late Permian]], [[Norian]] ([[End-Triassic extinction|end-Triassic]]), and [[Maastrichtian]] (end-Cretaceous). The remaining peak was a broad interval of high extinction smeared over the later half of the [[Devonian]], with its apex in the [[Frasnian]] stage.<ref name="Raup" />

Through the 1980s, Raup and Sepkoski continued to elaborate and build upon their extinction and origination data, defining a high-resolution [[biodiversity]] curve (the "Sepkoski curve") and successive [[evolutionary fauna]]s with their own patterns of diversification and extinction.<ref>{{Cite journal | author = Sepkoski, J.J. Jr. |year=1981 |title=A factor analytic description of the Phanerozoic marine fossil record |journal=Paleobiology |language=en |volume=7 |issue=1 |pages=36–53 |doi=10.1017/S0094837300003778 |bibcode=1981Pbio....7...36S |s2cid=133114885 |issn=0094-8373 |url=https://websites.pmc.ucsc.edu/~pkoch/EART_206/09-0120/Supplemental/Sepkoski%2081%20Pbio%207-36.pdf}}</ref><ref>{{cite journal | vauthors = Sepkoski JJ, Bambach RK, Raup DM, Valentine JW |year=1981 |title=Phanerozoic marine diversity and the fossil record |journal=Nature |language=en |volume=293 |issue=5832 |pages=435–437 |doi=10.1038/293435a0 |bibcode=1981Natur.293..435S |s2cid=4282371 |issn=1476-4687 |url= http://www.tomwbell.net/uploads/5/6/9/7/56976837/293435a0__1_.pdf}}</ref><ref>{{Cite book | vauthors = Sepkoski JJ |title=Geological Implications of Impacts of Large Asteroids and Comets on the Earth |date=1982-01-01 |chapter=Mass extinctions in the Phanerozoic oceans: A review |publisher=Geological Society of America |series=Geological Society of America Special Papers |volume=190 |pages=283–290 |language=en |id=Special Paper 190 |doi=10.1130/SPE190-p283 |isbn=0-8137-2190-3  |chapter-url=https://pubs.geoscienceworld.org/gsa/books/book/350/chapter/3796461/Mass-extinctions-in-the-Phanerozoic-oceans-A}}</ref><ref>{{Cite journal | vauthors = Sepkoski JJ |year=1984 |title=A kinetic model of Phanerozoic taxonomic diversity. III. Post-Paleozoic families and mass extinctions |journal=Paleobiology |language=en |volume=10 |issue=2 |pages=246–267 |doi=10.1017/S0094837300008186 |bibcode=1984Pbio...10..246S |s2cid=85595559 |issn=0094-8373 |url=https://www.cambridge.org/core/product/identifier/S0094837300008186/type/journal_article|url-access=subscription }}</ref><ref name=Sepkoski_1986>{{cite book | vauthors = Sepkoski JJ |year=1986 | chapter = Phanerozoic overview of mass extinction | title = Patterns and Processes in the History of Life |series=Dahlem Workshop Reports |pages=277–295 | veditors = Raup DM, Jablonski D |place=Berlin & Heidelberg, DE |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-642-70831-2_15 |isbn=978-3-642-70833-6 | chapter-url=http://link.springer.com/10.1007/978-3-642-70831-2_15 |access-date=2022-08-14 }}</ref><ref>{{cite journal | vauthors = Sepkoski JJ | year = 1989 | title = Periodicity in extinction and the problem of catastrophism in the history of life | journal = Journal of the Geological Society | volume = 146 | issue = 1 | pages = 7–19 | pmid = 11539792 | doi = 10.1144/gsjgs.146.1.0007 | bibcode = 1989JGSoc.146....7S | s2cid = 45567004 }}</ref> Though these interpretations formed a strong basis for subsequent studies of mass extinctions, Raup and Sepkoski also proposed a more controversial idea in 1984: a 26-million-year periodic pattern to mass extinctions.<ref name=Raup1984/> Two teams of [[astronomer]]s linked this to a hypothetical [[brown dwarf]] in the distant reaches of the [[Solar System]], inventing the "[[Nemesis hypothesis]]", which has been strongly disputed by other astronomers.

Around the same time, Sepkoski began to devise a compendium of marine animal [[genera]], which would allow researchers to explore extinction at a finer taxonomic resolution. He began to publish preliminary results of this in-progress study as early as 1986, in a paper that identified 29 extinction intervals of note.<ref name=Sepkoski_1986/> By 1992, he also updated his 1982 family compendium, finding minimal changes to the diversity curve despite a decade of new data.<ref name="Sepkoski_1992">{{cite report | vauthors = Sepkoski Jr JJ |year=1992 |title=A compendium of fossil marine animal families |edition=2nd |series=Milwaukee Public Museum Contributions in Biology and Geology |volume=83 |pages=1–156 |pmid=11542296 |url=https://www.mpm.edu/sites/default/files/files%20and%20dox/C%26R/library/bio-geo/%23083%20MPM%20Contributions%20in%20Biology%20and%20Geology%20Number%2083.pdf }}</ref><ref>{{cite journal | vauthors = Sepkoski JJ | year = 1993 | title = Ten years in the library: New data confirm paleontological patterns | journal = Paleobiology | volume = 19 | issue = 1 | pages = 43–51 | pmid = 11538041 | doi = 10.1017/S0094837300012306 | bibcode = 1993Pbio...19...43S | s2cid = 44295283 }}</ref> In 1996, Sepkoski published another paper that tracked marine genera extinction (in terms of net diversity loss) by stage, similar to his previous work on family extinctions. The paper filtered its sample in three ways: all genera (the entire unfiltered sample size), multiple-interval genera (only those found in more than one stage), and "well-preserved" genera (excluding those from groups with poor or understudied fossil records). Diversity trends in marine animal families were also revised based on his 1992 update.<ref name="Sepkoski_1996">{{cite book | vauthors = Sepkoski JJ |chapter=Patterns of Phanerozoic Extinction: A Perspective from Global Data Bases |year=1996 |title = Global Events and Event Stratigraphy in the Phanerozoic |pages=35–51 | veditors = Walliser OH |place=Berlin & Heidelberg, DE |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-642-79634-0_4 |isbn=978-3-642-79636-4 | chapter-url=http://link.springer.com/10.1007/978-3-642-79634-0_4 |access-date=2022-08-14}}</ref>

Revived interest in mass extinctions led many other authors to re-evaluate geological events in the context of their effects on life.<ref>{{cite journal | vauthors = Jablonski D | date = August 1991 | title = Extinctions: A paleontological perspective | journal = Science | volume = 253 | issue = 5021 | pages = 754–757 | pmid = 17835491 | doi = 10.1126/science.253.5021.754 | bibcode = 1991Sci...253..754J }}</ref> A 1995 paper by [[Michael Benton]] tracked extinction and origination rates among both marine and continental (freshwater & terrestrial) families, identifying 22 extinction intervals and no periodic pattern.<ref>{{cite journal | vauthors = Benton MJ | date = April 1995 | title = Diversification and extinction in the history of life | journal = Science | volume = 268 | issue = 5207 | pages = 52–58 | pmid = 7701342 | doi = 10.1126/science.7701342 | bibcode = 1995Sci...268...52B | url = http://doc.rero.ch/record/14806/files/PAL_E1962.pdf }}</ref> Overview books by O.H. Walliser (1996) and [[Anthony Hallam|A. Hallam]] and P.B. Wignall (1997) summarized the new extinction research of the previous two decades.<ref>{{Cite book | veditors = Walliser OH |year=1996 |title=Global Events and Event Stratigraphy in the Phanerozoic: Results of the International Interdisciplinary Cooperation in the IGCP-Project 216 "Global Biological Events in Earth History" |publisher=Springer Berlin Heidelberg |isbn=978-3-642-79636-4 |location=Berlin, Heidelberg |language=en |doi=10.1007/978-3-642-79634-0 |url=http://link.springer.com/10.1007/978-3-642-79634-0}}</ref><ref>{{Cite book | vauthors = Hallam A, Wignall PB |title=Mass Extinctions and Their Aftermath  |publisher=Oxford University Press |year=1997 |location=Oxford}}</ref> One chapter in the former source lists over 60 geological events that could conceivably be considered global extinctions of varying sizes.<ref>{{cite book | vauthors = Barnes CR, Hallam A, Kaljo D, Kauffman EG, Walliser OH |year=1996 | chapter = Global Event Stratigraphy |title = Global Events and Event Stratigraphy in the Phanerozoic |pages=319–333 |place=Berlin & Heidelberg, DE |publisher=Springer Berlin Heidelberg | doi = 10.1007/978-3-642-79634-0_16 |isbn=978-3-642-79636-4 }}</ref> These texts, and other widely circulated publications in the 1990s, helped to establish the popular image of mass extinctions as a "big five" alongside many smaller extinctions through prehistory.