The Habsburg Jaw And The Cost Of Royal Inbreeding

She notes that such marriages were not uncommon in the ruling houses of Europe well up until the last century (Queen Elizabeth II actually married her own third cousin). She notes that it was Spain’s Habsburg family (a/k/a The House of Austria), which ruled the “country for 184 years, had 9 out of the 11 total marriages during their reign that were “consanguineous; that is, they were marriages between close blood relatives”. Historians found that it was the inbreeding of these marriages that led to the downfall of the royal house.

PLOS one provides the scientific evidence of genetics “that inbreeding was a major cause responsible for the extinction of the dynasty when the king Charles II, physically and mentally disabled, died in 1700 and no children were born from his two marriages.

Dimuro writes:

But while the line was intact, this inbreeding caused this royal family to exhibit a number of peculiar physical traits, especially one known as the Habsburg jaw. The most salient indicator of the family’s inbreeding, the Habsburg jaw is what doctors refer to as mandibular prognathism. This condition is marked by a protrusion of the lower jaw to the point that it’s significantly larger than the upper jaw and creates an underbite sometimes bad enough that it can interfere with your speech and make it difficult to fully close your mouth.

When the first Spanish Habsburg ruler, Charles V, arrived in Spain in 1516, he couldn’t fully close his mouth due to his Habsburg jaw. This reportedly caused one bold peasant to shout at him, “Your majesty, shut your mouth! The flies of this country are very insolent.”

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In addition to being socially and culturally taboo, incestuous marriages are harmful in that they lead to higher rates of miscarriages, stillbirths, and neonatal deaths (only half of the Habsburg children survived to the age of 10, compared with the 80 percent survival rate of children from other Spanish families of the same time period).

Marriage between close family members also increases the chance that harmful recessive genes — which would normally peter out thanks to healthy dominant genes from non-related parents — will continue to be passed down (Queen Victoria of the United Kingdom unwittingly spread the recessive hemophilia across the entire continent thanks to the continued inter-marrying of the European royal families).

The End of the Line:

Most often, these unions took the form of marriages between first cousins, double-first cousins, and uncles/nieces.   Conceivably as a direct result of these marriages between relatives, infant and child mortality rose to 50% among Spanish Habsburgs, much higher than the average for the period. But the final Habspurg king of Spain, Charles II, was perhaps the most unfortunate result of these unions.   Also know as “El Hechizado” (“The Hexed”), Charles was severely deformed. The so-called “Habsburg Lip”, a form of mandibular prognathism often seen among members of the Habsburg Dynasty, was so pronounced in Charles’ case that it was difficult for him to speak.   An enlarged tongue, gastrointestinal problems, mental retardation, and possible growth problems meant that Charles was raised almost as an infant until the age of 10.  Even as he grew older, he was never able to govern effectively.