Under evolutionen, kan nogle strukturer mister deres oprindelige funktion og blive [[rudimentære strukturer]].<ref name="Fong">{{cite journal |last1=Fong |first1=Daniel F. |last2=Kane |first2=Thomas C. |last3=Culver |first3=David C. |date=november 1995 |title=Vestigialization and Loss of Nonfunctional Characters |journal=Annual Review of Ecology and Systematics |location=Palo Alto, CA |publisher=Annual Reviews |volume=26 |pages=249–268 |doi=10.1146/annurev.es.26.110195.001341 |issn=1545-2069}}</ref> Sådanne strukturer kan have ringe eller ingen funktion i en nuværende art, men alligevel har en klar funktion i forfædrene eller andre nært beslægtede arter. Eksempler indbefatter [[pseudogener]],<ref name="ZhaoLei Zhang1">{{cite journal |author1=ZhaoLei Zhang |last2=Gerstein |first2=Mark |date=august 2004 |title=Large-scale analysis of pseudogenes in the human genome |journal=Current Opinion in Genetics & Development |location=Amsterdam, the Netherlands |publisher=Elsevier |volume=14 |issue=4 |pages=328–335 |doi=10.1016/j.gde.2004.06.003 |issn=0959-437X |pmid=15261647}}</ref> de ikke-funktionelle rester af øjne i blinde grotteboende fisk,<ref name="Jeffery1">{{cite journal |last=Jeffery |date=maj-juni 2005 |first1=William R. |title=Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish |journal=Journal of Heredity |location=Oxford |publisher=Oxford University Press on behalf of the American Genetic Association |volume=96 |issue=3 |pages=185–196 |doi=10.1093/jhered/esi028 |issn=0022-1503 |pmid=15653557}}</ref> vinger i flyvende fugle,<ref name="Maxwell1">{{cite journal |last1=Maxwell |first1=Erin E. |last2=Larsson |first2=Hans C.E. |date=maj 2007 |title=Osteology and myology of the wing of the Emu (''Dromaius novaehollandiae'') and its bearing on the evolution of vestigial structures |journal=[[Journal of Morphology]] |location=Hoboken, NJ |publisher=John Wiley & Sons |volume=268 |issue=5 |pages=423–441 |doi=10.1002/jmor.10527 |issn=0362-2525 |pmid=17390336}}</ref> og tilstedeværelsen af hofteben i hvaler og slanger.<ref name="transformation445" /> Eksempler på rudimentære strukturer hos mennesker omfatter [[Visdomstand|visdomstænder]],<ref name="Silvestri1">{{cite journal |last1=Silvestri |first1=Anthony R., Jr. |last2=Singh |first2=Iqbal |date=april 2003 |title=The unresolved problem of the third molar: Would people be better off without it? |url=http://jada.ada.org/cgi/content/full/134/4/450 |journal=[[Journal of the American Dental Association]] |location=Chicago, IL |publisher=[[American Dental Association]] |volume=134 |issue=4 |pages=450–455 |doi=10.14219/jada.archive.2003.0194 |issn=0002-8177 |pmid=12733778 |access-date=19. juni 2015 |archive-date=23. august 2014 |archive-url=https://web.archive.org/web/20140823063158/http://jada.ada.org/content/134/4/450.full |url-status=dead }}</ref> [[haleben]],<ref name="Fong" /> vermiform appendiks,<ref name="Fong" /> og andre adfærdsmæssige levn såsom gåsehud <ref name="Coyne1">{{harvnb|Coyne|2009|p=62}}</ref><ref name="Darwin2">{{harvnb|Darwin|1872|pp=101, 103}}</ref> og primitive reflekser.<ref name="Gray1">{{harvnb|Gray|2007|p=66}}</ref><ref name="Coyne2">{{harvnb|Coyne|2009|pp=85–86}}</ref><ref name="Stevens1">{{harvnb|Stevens|1982|p=87}}</ref>
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