The Habsburg Jaw And The Cost Of Royal Inbreeding

Intermarriages within European ruling dynasties were common until recent times, with even Queen Elizabeth II marrying her third cousin. However, the Spanish Habsburgs took this tradition to extreme levels of risk. Out of the 11 marriages within their reign over Spain from 1516 to 1700, a staggering nine were incestuous.

Experts widely attribute the downfall of the Spanish Habsburgs to generations of intermarriage. This practice led to a gradual decline in the family's genetic health, culminating in Charles II, the final male successor, who was incapable of fathering children, marking the end of Habsburg dominance.

Despite the family's lineage, intermarriage gave rise to distinct physical traits, notably the iconic Habsburg jaw, also known as mandibular prognathism. This condition, characterized by a protruding lower jaw, was famously displayed by Charles V, the first Spanish Habsburg monarch, leading to a humorous incident where a peasant joked about flies.

While the Habsburgs' reign in Spain officially began in 1516, their influence across Europe dates back to the 13th century. Philip I of Burgundy's marriage to Joanna of Castile in 1496 solidified their Spanish dominion, eventually leading to Charles V's ascension to the throne in 1516.

However, the Habsburgs knew that their hold on power was fragile. To maintain control, they sought royal spouses exclusively within their family, inadvertently setting the stage for their own downfall. In addition to facing social stigma, incestuous unions led to increased rates of genetic disorders and high child mortality.

The intermarriages not only perpetuated deleterious recessive genes but also spread them across Europe. Queen Victoria's unwitting propagation of recessive haemophilia exemplifies this phenomenon. Among the Habsburgs, the most notorious inherited trait was the distinctive Habsburg jaw.

While not part of the Spanish Habsburg lineage, Marie Antoinette, the famed French queen, couldn't entirely escape the family's distinctive features. Despite her renowned beauty, she was noted for her "projecting lower lip," giving her a perpetual pout.

Yet, Marie Antoinette's challenges pale in comparison to those faced by Charles II, the last Habsburg ruler of Spain, who ascended the throne in 1665.

Dubbed "El Hechizado" or "the hexed one," Charles II grappled with a pronounced lower jaw that hindered his eating and speech. Alongside his prominent Habsburg jaw, the king was short, frail, impotent, intellectually challenged, plagued by numerous digestive issues, and didn't utter a word until he reached four years of age. One French ambassador, tasked with assessing a potential marriage prospect, described his findings as follows “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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