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Liña 21:
 
=== Selección natural ===
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Some mammals naturally have reduced amounts of fur. Some [[semiaquatic]] or [[aquatic animal|aquatic]] mammals such as [[cetacean]]s, [[pinniped]]s and [[hippopotamuses]] have evolved hairlessness, presumably to reduce resistance through water. The [[naked mole-rat]] has evolved hairlessness, perhaps as an adaptation to their subterranean life-style. Two of the largest extant mammals, the [[elephant]] and the [[rhinoceros]], are largely hairless. The [[hairless bat]] is mostly hairless but does have short bristly hairs around its neck, on its front toes, and around the throat sac, along with fine hairs on the head and tail membrane. Most hairless animals cannot go in the sun for long periods of time, or stay in the cold for too long. <ref name=ADW>{{cite web|last=Thomson|first=Paul|title=Cheiromeles torquatus|url=http://animaldiversity.ummz.umich.edu/accounts/Cheiromeles_torquatus/|publisher=Animal Diversity Web|accessdate=29 October 2013|year=2002}}</ref>
 
Algúns mamíferos reduciron de forma natural a súa cantidade de pelo. Algúns mamíferos acuáticos ou semiacuáticos como os [[cetáceo]]s ou [[hipopótamo]] evolucionaron cara a unha pel espida, presumiblemente para reducir a resistencia á auga. A [[rata-toupa espida]] tamén perdeu o pelo, quizais como unha adaptación ao seu estilo de vida subterráneo. Dous dos grandes mamíferos existentes, o [[elefante]] e o [[rinoceronte]], teñen moi poucos pelos. O [[morcego espido]] case non ten pelos pero teñen curtos pelos bastos arredor do pescozo, nas súas dedas frontais, e arredor do saco da súa gorxa, xunto con pelos finos na cabeza e membrana da cola. A m aioría dos animais sen pelo non poden estar ao sol durante moito tempo ou permaneceren en zonas frías por tempo prolongado. <ref name=ADW>{{cite web|last=Thomson|first=Paul|title=Cheiromeles torquatus|url=http://animaldiversity.ummz.umich.edu/accounts/Cheiromeles_torquatus/|publisher=Animal Diversity Web|accessdate=29 October 2013|year=2002}}</ref>
Humans are the only primate species that have undergone significant hair loss. The hairlessness of humans compared to related species may be due to loss of functionality in the [[pseudogene]] KRTHAP1 (which helps produce [[keratin]]) in the human lineage about 240,000 years ago.<ref>{{Cite journal
 
Os seres humanos son a única especie de primates que evolucionaron experimentando unha significativa perda de pelo corporal. Isto pode deberse á perda da funcionalidade do [[pseudoxene]] KRTHAP1 (que axuda a producir [[queratina]]) na liñaxe humana hai uns 240.000 anos.<ref>{{Cite journal
| doi = 10.1007/s004390000439
| last1 = Winter | first1 = H.
Liña 42:
| year = 2001
| pmid = 11214905
}}</ref> MutationsAs inmutacións theno genexene HR canpodn leadorixinar tounha completecompleta hairperda lossde pelo, thoughaíndo que thisisto isnon noté typicaltípico innos humanshumanos.<ref>{{cite web|url=http://www.nature.com/srep/2011/110706/srep00032/full/srep00032.html|accessdate=2012-03-13|title=Molecular evolution of HR, a gene that regulates the postnatal cycle of the hair follicle}}</ref>
 
=== Selección artificial ===
Sheep have not become hairless, however, their pelage is usually referred to as "wool" rather than fur.
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===Artificial selection===
Humans have artificially selected some domesticated mammalian species to have breeds that are hairless. There are several breeds of hairless cats, perhaps the most commonly known being the [[Sphynx (cat)|Sphynx cat]]. Similarly, there are several breeds of [[hairless dog]]s. Other examples of artificially selected hairless animals include the [[Skinny pig|hairless guinea-pig]], [[nude mouse]], and the [[Fancy rat#Hairless rat|hairless rat]].
 
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