Editing Extinction event (section)

==Evolutionary importance==
{{Life timeline}}
{{See also|Evolutionary radiation|Macroevolution}}

Mass extinctions have sometimes accelerated the [[evolution]] of [[life|life on Earth]]. When dominance of particular ecological niches passes from one group of organisms to another, it is rarely because the newly dominant group is "superior" to the old but usually because an extinction event eliminates the old, dominant group and makes way for the new one, a process known as [[adaptive radiation]].<ref>
{{cite book | vauthors = Benton MJ | author-link = Michael Benton | title = Vertebrate Palaeontology | publisher = Blackwell | year = 2004 | chapter = 6. Reptiles Of the Triassic | chapter-url = http://www.blackwellpublishing.com/book.asp?ref=0632056371 | isbn = 978-0-04-566002-5 }}</ref><ref>{{cite journal | vauthors = van Valkenburgh B | year = 1999 | title = Major patterns in the history of carnivorous mammals | journal = Annual Review of Earth and Planetary Sciences | volume = 27 | pages = 463–93 | doi = 10.1146/annurev.earth.27.1.463 | bibcode = 1999AREPS..27..463V | url = https://zenodo.org/record/890156 }}</ref>

For example, [[mammaliaformes]] ("almost mammals") and then [[mammal]]s existed throughout the reign of the [[dinosaur]]s, but could not compete in the large terrestrial vertebrate niches that dinosaurs monopolized. The [[Cretaceous–Paleogene extinction event|end-Cretaceous]] mass extinction removed the non-avian dinosaurs and made it possible for mammals to expand into the large terrestrial vertebrate niches. The dinosaurs themselves had been beneficiaries of a previous mass extinction, the [[Triassic–Jurassic extinction event|end-Triassic]], which eliminated most of their chief rivals, the [[crurotarsans]]. Similarly, within [[Synapsida]], the replacement of taxa that originated in the earliest, [[Pennsylvanian (geology)|Pennsylvanian]] and [[Cisuralian]] evolutionary radiation (often still called "[[pelycosaur]]s", though this is a [[paraphyletic]] group) by [[Therapsida|therapsids]] occurred  around the [[Kungurian]]/[[Roadian]] transition, which is often called [[Olson's Extinction|Olson's extinction]]<ref name="Brocklehurst 2018">{{cite journal |last1=Brocklehurst |first1=Neil |title=An examination of the impact of Olson's extinction on tetrapods from Texas |journal=PeerJ |date=15 May 2018 |volume=6 |pages=e4767 |doi=10.7717/peerj.4767|doi-access=free |pmid=29780669 |pmc=5958880 }}</ref><ref name="Brocklehurst 2020">{{cite journal |last1=Brocklehurst |first1=Neil |title=Olson's Gap or Olson's Extinction? A Bayesian tip-dating approach to resolving stratigraphic uncertainty |journal=Proceedings of the Royal Society B: Biological Sciences |date=10 June 2020 |volume=287 |issue=1928 |pages=20200154 |doi=10.1098/rspb.2020.0154 |pmid=32517621 |url=https://doi.org/10.1098/rspb.2020.0154 |language=en |issn=0962-8452|pmc=7341920 }}</ref> (which may be a slow decline over 20 Ma<ref name="Didier & Laurin 2024">{{cite journal |last1=Didier |first1=Gilles |last2=Laurin |first2=Michel |title=Testing extinction events and temporal shifts in diversification and fossilization rates through the skyline Fossilized Birth-Death (FBD) model: The example of some mid-Permian synapsid extinctions |journal=Cladistics |date=June 2024 |volume=40 |issue=3 |pages=282–306 |doi=10.1111/cla.12577 |pmid=38651531 |language=en |issn=0748-3007|doi-access=free }}</ref> rather than a dramatic, brief event).

Another point of view put forward in the [[Escalation hypothesis]] predicts that species in ecological niches with more organism-to-organism conflict will be less likely to survive extinctions. This is because the very traits that keep a species numerous and viable under fairly static conditions become a burden once population levels fall among competing organisms during the dynamics of an extinction event.

Furthermore, many groups that survive mass extinctions do not recover in numbers or diversity, and many of these go into long-term decline, and these are often referred to as "[[Dead Clade Walking|Dead Clades Walking]]".<ref>
{{cite journal | vauthors = Jablonski D | title = Survival without recovery after mass extinctions | journal =   Proceedings of the National Academy of Sciences| volume = 99 | issue = 12 | pages = 8139–8144 | date = June 2002 | pmid = 12060760 | pmc = 123034 | doi = 10.1073/pnas.102163299 | bibcode = 2002PNAS...99.8139J | doi-access = free }}
</ref>
However, clades that survive for a considerable period of time after a mass extinction, and that were reduced to only a few species, are likely to have experienced a rebound effect called the "[[push of the past]]".<ref name="POTPa">
{{cite journal | vauthors = Budd GE, Mann RP | title = History is written by the victors: The effect of the push of the past on the fossil record | journal = Evolution; International Journal of Organic Evolution | volume = 72 | issue = 11 | pages = 2276–2291 | date = November 2018 | pmid = 30257040 | pmc = 6282550 | doi = 10.1111/evo.13593 }}
</ref>

Darwin was firmly of the opinion that biotic interactions, such as competition for food and space – the 'struggle for existence' – were of considerably greater importance in promoting evolution and extinction than changes in the physical environment. He expressed this in ''[[The Origin of Species]]'':
: "Species are produced and exterminated by slowly acting causes ... and the most import of all causes of organic change is one which is almost independent of altered ... physical conditions, namely the mutual relation of organism to organism – the improvement of one organism entailing the improvement or extermination of others".<ref>{{cite book | vauthors = Hallam A, Wignall PB | author1-link = Hallam, Anthony | year = 2002 | title = Mass Extinctions and their Aftermath | place = New York, NY | publisher = Oxford University Press }}</ref>