Editing Cave bear (section)

===Evolution===
Both the cave bear and the brown bear are thought to be descended from the [[Plio-Pleistocene]] Etruscan bear (''[[Ursus etruscus]]'')<ref name=Kurten1976>{{cite book |author=Kurtén, B. |year=1976 |title=The Cave Bear Story: Life and death of a vanished animal |publisher=Columbia University Press |location=New York, NY}}</ref><ref name=Rabader2000>{{cite book |vauthors=Rabeder G, Nagel D, Pacher M |year=2000 |title=Der Höhlenbär. Species 4 |publisher=Thorbecke Verlag |location=Stuttgart, DE}}</ref><ref>{{cite book |vauthors=Argant A, Crégut-Bonnoure E |year=1996 |contribution=Famille des Ursidae |editor1=Guérin, C. |editor2=Patou-Mathis, M. |title=Les grands mammiferes Plio-Pleistocenes d'Europe |pages=167–177 |publisher=Masson |location=Paris, FR}}</ref> that lived about 5.3&nbsp;[[Mya (unit)|Mya]] to 100,000&nbsp;years ago. The last common ancestor of cave bears and brown bears lived between 1.2&ndash;1.4&nbsp;Mya.<ref name="Loreille2001">{{Cite journal |author=Loreille, O. |display-authors=etal |year=2001 |title=Ancient DNA analysis reveals divergence of the cave bear, ''Ursus spelaeus'', and brown bear, ''Ursus arctos'', lineages |journal=[[Current Biology]] |volume=11 |issue=3 |pages=200–203 |bibcode=2001CBio...11..200L |doi=10.1016/S0960-9822(01)00046-X |pmid=11231157 |doi-access=free}}</ref> Middle Pleistocene remains of the cave bear lineage are assigned to ''[[Ursus deningeri]]'' (Deninger's bear),<ref name=":0" /> which is known from remains spanning from Europe to China.<ref>{{Cite journal |last1=Jiangzuo |first1=Qigao |last2=Wagner |first2=Jan |last3=Chen |first3=Jin |last4=Dong |first4=Cuiping |last5=Wei |first5=Jianhua |last6=Ning |first6=Juan |last7=Liu |first7=Jinyi |date=2018-11-01 |title=Presence of the Middle Pleistocene cave bears in China confirmed – Evidence from Zhoukoudian area |url=https://linkinghub.elsevier.com/retrieve/pii/S0277379118303354 |journal=Quaternary Science Reviews |language=en |volume=199 |pages=1–17 |doi=10.1016/j.quascirev.2018.09.012}}</ref> The transition between Deninger's bear and the cave bear is given as the last interglacial, although the boundary between these forms is arbitrary, and intermediate or transitional [[taxa]] have been proposed, e.g. ''Ursus spelaeus deningeroides'',<ref name=Argant1991>{{Cite journal|author=Argant, A. |title=Carnivores quaternaires de Bourgogne |year=1991 |journal=Documents des Laboratoires de Géologie de la Faculté des Sciences de Lyon |volume=115 |pages=1–301}}</ref> while other authorities consider both taxa to be chronological variants of the same species.<ref name=MazzaRustioni1994>{{Cite journal |author1=Mazza, P. |author2=Rustioni, M. |title=On the phylogeny of Eurasian bears |year=1994 |journal=Palaeontographica Abteilung A |volume=230 |issue=1–3 |pages=1–32|doi=10.1127/pala/230/1994/1 |bibcode=1994PalAA.230....1M |s2cid=247508689 }}</ref>

Cave bears found anywhere will vary in age, thus facilitating investigations into evolutionary trends. The three anterior [[premolar]]s were gradually reduced, then disappeared, possibly in response to a largely vegetarian diet. In a fourth of the skulls found in the ''Conturines'', the third premolar is still present, while more [[Synapomorphy|derived]] specimens elsewhere lack it. The last remaining premolar became conjugated with the true [[Molar (tooth)|molars]], enlarging the crown and granting it more cusps and cutting borders. This phenomenon, called ''molarization'', improved the [[mastication]] capacities of the molars, facilitating the processing of tough vegetation. This allowed the cave bear to gain more energy for hibernation, while eating less than its ancestors.<ref>{{cite web |url=http://www.altabadia.it/orsispelei/evoluzione_i.htm |title=Gli orsi spelèi delle Conturines / Ursus Spelaeus |website=Altabadia.it |access-date=2011-09-26 |df=dmy-all}}</ref>

In 2005, scientists recovered and [[DNA sequencing|sequenced]] the [[nuclear DNA]] of a cave bear that lived between 42,000 and 44,000 years ago. The procedure used genomic DNA extracted from one of the animal's [[teeth]]. Sequencing the DNA directly (rather than first replicating it with the [[polymerase chain reaction]]), the scientists recovered 21 cave bear [[gene]]s from remains that did not yield significant amounts of DNA with traditional techniques.<ref name="Noonan2005">{{Cite journal |author=Noonan, James P. |display-authors=etal |year=2005 |title=Genomic Sequencing of Pleistocene Cave Bears |url=https://digital.library.unt.edu/ark:/67531/metadc786565/ |journal=[[Science (journal)|Science]] |volume=309 |issue=5734 |pages=597–599 |bibcode=2005Sci...309..597N |doi=10.1126/science.1113485 |pmid=15933159 |s2cid=34704597 |doi-access=free}}</ref> This study confirmed and built on results from a previous study using [[mitochondrial DNA]] extracted from cave bear remains ranging from 20,000 to 130,000 years old.<ref name=Loreille2001/> Both show that the cave bear was more closely related to the [[brown bear]] and [[polar bear]] than it was to the [[American black bear]], but had split from the brown bear lineage before the distinct eastern and western brown bear lineages diversified, and before the split of brown bears and polar bears. The [[Genetic divergence|divergence]] date estimate of cave bears and brown bears is about 1.2–1.4&nbsp;Mya.<ref name=Loreille2001/> However, a recent study showed that both species had some hybridization between them.<ref>{{Cite journal|last1=Barlow|first1=Axel|last2=Cahill|first2=James A.|last3=Hartmann|first3=Stefanie|last4=Theunert|first4=Christoph|last5=Xenikoudakis|first5=Georgios|last6=Fortes|first6=Gloria G.|last7=Paijmans|first7=Johanna L. A.|last8=Rabeder|first8=Gernot|last9=Frischauf|first9=Christine|date=27 August 2018|title=Partial genomic survival of cave bears in living brown bears|journal=[[Nature Ecology & Evolution]]|language=En|volume=2|issue=10|pages=1563–1570|doi=10.1038/s41559-018-0654-8|issn=2397-334X|url=https://escholarship.org/content/qt6qr394rt/qt6qr394rt.pdf?t=poma92|pmid=30150744|pmc=6590514|bibcode=2018NatEE...2.1563B }}</ref>