The Habsburg Jaw

Holy Roman Emperor Charles V

Marie-Antoinette of Austria

From All That's Interesting:

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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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). For the Habsburgs, the most well-known trait that was passed down was the Habsburg jaw.

One of the most famous Habsburgs (not of the Spanish Habsburgs, however) did not entirely manage to dodge the family trait either: Marie Antoinette [Queen] of France, although famously good-looking, had “a projecting lower lip” that made it seem as though she had a constant pout. But Marie Antoinette got off easy compared with the last Habsburg ruler of Spain, who took the throne in 1665. (Read more.)