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The Habsburg Jaw And The Cost Of Royal Inbreeding

Although unions between blood relatives were prevalent among the European ruling dynasties until relatively recent times (even Queen Elizabeth II married her third cousin), the Spanish Habsburgs took this practice to an exceptionally risky extent. Remarkably, of the 11 marriages that transpired among them during their 184-year reign over Spain from 1516 to 1700, an astonishing nine of them were incestuous.

Indeed, contemporary scholars broadly assert that the Spanish Habsburgs' decline can be attributed to successive generations of intermarriage. As a result of this practice, the family's genetic lineage steadily deteriorated, ultimately culminating in Charles II, the last male successor, who was physically incapable of fathering offspring, effectively marking the conclusion of Habsburg dominance.

What Is The Habsburg Jaw?

Nevertheless, as long as the family's lineage persisted, this intermarriage practice resulted in the emergence of distinctive physical characteristics within the royal family, notably the renowned Habsburg jaw. The most prominent manifestation of their inbreeding, the Habsburg jaw, is medically referred to as mandibular prognathism. This condition is characterised by the lower jaw protruding to a considerable extent, making it notably larger than the upper jaw and leading to an underbite, occasionally severe enough to affect speech and the ability to completely close the 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.”

The House Of Habsburg

While their formal reign over Spain commenced in 1516, the Habsburgs, initially hailing from German and Austrian origins, had wielded influence over various European territories since the 13th century. Their Spanish dominion was set in motion when Philip I of Burgundy, who ruled over lands that encompass present-day Luxembourg, Belgium, France, and the Netherlands, married Joanna of Castile in 1496. Joanna was the female successor to the throne of much of what is now Spain.

After a decade of political wrangling and skirmishes with competitors for power in Spain, Philip I took the throne of Castile in 1506, six years after having fathered Charles V, who himself took the Spanish throne in 1516.

However, just as these Spanish Habsburgs themselves had received the crown through marriage, they knew that it easily pass out of their hands in the same way. In their determination to keep the Spanish monarchy within the family, they began to look for royal spouses only within their own family.

The Cost Of Inbreeding

Apart from securing the Habsburg dynasty's hold on the throne, this intermarriage had unintended consequences that ultimately contributed to the dynasty's decline. It was not just the crown that was transmitted from one generation to the next, but a set of genes that gave rise to congenital disorders.

In addition to being socially and culturally stigmatized, these incestuous unions were detrimental in that they resulted in heightened rates of miscarriages, stillbirths, and neonatal fatalities. In fact, only half of Habsburg children survived to reach the age of 10, in stark contrast to the 80 percent survival rate observed among children from other Spanish families during the same period.

Moreover, marriage between close relatives elevated the likelihood that deleterious recessive genes, which would typically diminish in impact due to the presence of healthy dominant genes from non-related parents, continued to be inherited. An example of this can be seen in Queen Victoria of the United Kingdom, who inadvertently propagated recessive haemophilia across the entire continent due to the continued intermarriage within European royal families.

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

Royals Affected By 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 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.

The End Of The Line

Nicknamed El Hechizado (“the hexed one”), Charles II had a lower jaw so pronounced he struggled to eat and speak. In addition to his Habsburg jaw, the king was short, weak, impotent, mentally handicapped, suffered numerous intestinal problems, and did not even speak until he was four years old. One French ambassador sent to scope out a prospective marriage wrote back that “The Catholic King is so ugly as to cause fear and he looks ill.”

Charles II's father, Philip IV, married his niece, a perilously close familial connection that rendered him both Charles's father and great-uncle. Due to centuries of consanguineous marriages leading up to the birth of the final heir, modern researchers have determined that the inbreeding coefficient (the likelihood of inheriting two identical genes due to the parents' degree of relatedness) was nearly as high as that of a child born of an incestuous union.

Charles II, Habsburg jaw and all, proved unable to father any offspring; some researchers speculate that he might have been infertile. At the age of 39, in 1700, his body succumbed, marking the culmination of two centuries' worth of deleterious traits being passed down to a single individual.

Ironically, the attempt to maintain power within the family ultimately weakened the Habsburgs. They lost the Spanish throne due to the very intermarriage process they had initially believed would ensure its preservation.

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