Prognathism in humans can occur due to normal variation among [[phenotypes]]. In human populations where prognathism is not the norm, it may be a malformation, the result of injury, a disease state or a hereditary condition.<ref>{{MedlinePlusEncyclopedia|003026|Prognathism}}</ref>▼

Not all alveolar prognathism is anomalous, and significant differences can be observed among different ethnicities.{{sfn|Vioarsdóttir|O'Higgins|Stringer|2002|pp=211–229}}▼

=== {{anchor|Mandibular prognathism}} Mandibular prognathism (progenism) ===▼

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Pathologic [[Mandible|mandibular]] prognathism is a potentially disfiguring genetic disorder where the lower [[jaw]] outgrows the upper, resulting in an extended [[chin]] and a [[crossbite]]. In both humans and animals, it can be the result of [[inbreeding]].{{sfn|Vilas|Ceballos|Al-Soufi|González-García|2019|pp=563-571}} In brachycephalic or flat-faced dogs, like [[shih tzu]]s and [[Boxer (dog)|boxers]], it can lead to problems such as underbite.{{sfn|Beuchat|2015}}▼

In humans, it results in a condition sometimes called ''lantern jaw'', reportedly derived from 15th century [[Lantern|horn lanterns]], which had convex sides.<ref>{{OMIM|176700|PROGNATHISM, MANDIBULAR}}</ref>{{efn|The [[Oxford English Dictionary|OED]] uses a slightly different definition, "long thin jaws, giving a hollow appearance to the cheek".<ref>{{OED|lantern jaw|id=105665}}</ref>}} Traits such as these were often exaggerated by inbreeding, and can be traced within specific families.{{sfn|Vilas|Ceballos|Al-Soufi|González-García|2019|pp=563-571}}▼

Although more common than appreciated, the best known historical example is '''Habsburg jaw''', or Habsburg or '''Austrian lip''', due to its prevalence in members of the [[House of Habsburg]], which can be traced in their portraits.{{sfn|Vilas|Ceballos|Al-Soufi|González-García|2019}} The process of portrait-mapping has provided tools for [[geneticist]]s and [[Pedigree chart|pedigree]] analysis; most instances are considered [[polygene|polygenic]],{{sfn|Wolff|Wienker|Sander|1993|pp=112–116}} but a number of researchers believe that this trait is transmitted through an autosomal recessive type of inheritance.<ref name="Безуглый 2020">{{cite journal |last1=Безуглый |first1=Т. А. |title=Влияние На Человека Признаков, Передаваемых По Аутосомно-Рецессивному Типу (на Примере Династии Габсбургов) |trans-title=Influence on the Human Traits Transmitted According to the Autosomal-Recessive Type (on the Example of the Habsburg Dynasty) |date=2020 |url=https://www.elibrary.ru/item.asp?id=44270977 |language=ru }}</ref>{{sfn|Vilas|Ceballos|Al-Soufi|González-García|2019}}▼

Allegedly introduced into the family by a [[Cymburgis of Masovia|member]] of the [[Piast dynasty]], it is clearly visible on family tomb sculptures in [[St. John's Archcathedral, Warsaw|St. John's Cathedral, Warsaw]]. A high propensity for politically motivated intermarriage among Habsburgs meant the dynasty was virtually unparalleled in the degree of its inbreeding. [[Charles II of Spain]], who lived 1661 to 1700, is said to have had the most pronounced case of the Habsburg jaw on record,{{sfn|Mitchell|2013|pp=303-308}} due to the high number of [[consanguineous]] marriages in the dynasty preceding his birth.<ref name="Безуглый 2020"/>{{sfn|Vilas|Ceballos|Al-Soufi|González-García|2019}}▼

Prior to the development of modern dentistry, there was no treatment for this condition; those who had it simply endured it. Today, the most common treatment for mandibular prognathism is a combination of [[orthodontics]] and [[orthognathic surgery]]. The orthodontics can involve [[Dental braces|braces]], removal of teeth, or a [[mouthguard]].<ref>{{cite web |url=https://www.colgate.com/en-us/oral-health/developmental-disabilities/treating-prognathism-ways-to-correct-abnormal-jaw-alignment |title = Treating Prognathism: Ways To Correct Abnormal Jaw Alignment}}</ref>▼

==In insects==▼