July 14, 2020

Family sex is behind the "Habsburg jaw"

The "Habsburg jaw", a deformation of the chin characteristic of this dynasty in Spanish and Austrian kings and their wives, can be attributed to inbreeding, according to a study published Monday in the magazine Annals of Human Biology. Generations of mixed marriages ensured for more than 200 years the influence of the family in a European empire that included Spain and Austria, but they led to his disappearance when the last Habsburg monarch (Charles II) was unable to have an heir.

So far, the authors of this new study say in a press release, no research has confirmed whether the distinctive chin known as the "Habsburg jaw" was the result of inbreeding (this family is known in Spain as the dynasty of the Austrias). “The Habsburg dynasty was one of the most influential in Europe, but it became famous for inbreeding, which was its final fall. We show for the first time that there is a clear positive relationship between consanguinity and the appearance of the Habsburg jaw, ”says lead researcher Roman Vilas, from the University of Santiago de Compostela.

This work combines the analysis of historical portraits with genetic studies, and to carry it out the researchers recruited ten maxillofacial surgeons. These had to analyze facial deformity in 66 portraits of 15 members of the aforementioned dynasty, most of them preserved in the Museum of Art History in Vienna and the Prado Museum in Madrid.

Thus, the tables were analyzed to diagnose eleven characteristics of mandibular prognathism, also known as the "Habsburg jaw", and seven characteristics linked to maxillary deficiency, including the most recognizable, the prominent lower lip and an outstanding nasal tip. From this analysis, surgeons scored the degree of mandibular prognathism and maxillary deficiency of each member of the Habsburg family.

For example, they saw that Maria de Burgundy, who married Maximilian I in 1477, showed the lowest degree in both traits, however, mandibular prognathism was more pronounced in Philip IV, king of Spain and Portugal from 1612 to 1640. The maxillary deficiency was diagnosed to a greater extent in five members of the family: Maximilian I (regent since 1493), his daughter Margarita of Austria, his nephew Carlos I of Spain, the great-grandson of Carlos Felipe IV and the last of the Habsburg line, Carlos II.

The study authors detected a correlation between the two diseases, and suggest that the "Habsburg jaw" is in fact characterized by both and that they share a common genetic basis. The extent of inbreeding was calculated from a large-scale family tree, with more than 6,000 individuals belonging to more than 20 generations. The researchers detected a strong relationship between the degree of consanguinity and the degree of mandibular prognathism; The relationship with maxillary deficiency was also positive, but it was only statistically significant in two of the seven characteristics diagnosed.

The causes of the relationship between consanguinity and facial deformity remain unclear, but the authors point out that the main effect of mating between relatives is an increase in the chances that offspring inherit identical forms of a gene of both parents (genetic homozygosity). This reduces the genetic fitness of people, so the "Habsburg jaw" should be considered a recessive condition, summary. EFE

. (tagsToTranslate) Science (t) History

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