The Habsburgs were once the most powerful family in the world, ruling over countries such as the Holy Roman Empire, England, France, Germany, Russia, Poland, Hungary, Portugal, Spain, and the Netherlands. Their lineage lasted for 700 years.
In order to secure its influence, the family relied on generations of intermarriage, but this lack of genetic diversity eventually ended up being their downfall. Now, a new study has confirmed that facial deformities in Habsburg bloodline, colloquially known as the “Habsburg jaw”, can be traced to inbreeding.
The most famous example of mandibular prognathism, otherwise known as “Habsburg jaw”, was Charles II of Spain. He was the last king of the Spanish Hapsburgs line, a dynasty where uncle-niece, first cousins and other consanguineous unions were prevalent. In many ways, Charles was the culmination of hundreds of years of inbreeding in a royal blood empire — thought to be perfect. In reality, the last Habsburgs were anything but perfect.
Charles II died prematurely aged 39 but not before his foolish behavior plunged his kingdom into chaos eventually leading to the War of Spanish Succession. This was the first world war of modern times with theatres of war in Spain, Italy, Germany, Holland, and at sea. It’s estimated the war resulted in 400,000 casualties.
Here’s how one biography describes King Charles (Carlos) II:
“The Habsburg King Carlos II of Spain was sadly degenerated with an enormous misshapen head. His Habsburg jaw stood so much out that his two rows of teeth could not meet; he was unable to chew. His tongue was so large that he was barely able to speak. His intellect was similarly disabled. His brief life consisted chiefly of a passage from prolonged infancy to premature senility. Carlos’ family was anxious only to prolong his days and thought little about his education, so that he could barely read or write. He had been fed by wet nurses until the age of 5 or 6 and was not allowed to walk until almost fully grown. Even then, he was unable to walk properly, because his legs would not support him and he fell several times. His body remained that of an invalid child. The nature of his upbringing, the inadequacy of his education, the stiff etiquette of his court, his dependence upon his mother and his superstition helped to create a mentally retarded and hypersensitive monarch.”
Facial deformities, as well as a history of mental illness, run deep in the Habsburg family line. However, until now no study has confirmed that the distinct “Habsburg jaw” was the result of inbreeding.
Francisco Ceballos, is a geneticist who for the last couple of years has been studying genomic inbreeding in world populations. Ceballos and colleagues enlisted the help of 10 maxillofacial surgeons who were asked to use their expertise and judge facial deformity in 66 portraits of 11 Habsburg family members.
Many of these portraits are curated by some of the world’s foremost art museums, including the Prado Museum in Madrid and the Kunsthistorisches Museum in Vienna. The study only employed paintings where it has been historically confirmed that the authors had personally seen the individual portrayed.
The experts scored each family member on their degree of mandibular prognathism and maxillary deficiency (a prominent lower lip and an overhanging nasal tip respectively). Meanwhile, the researchers calculated the inbreeding coefficient of the Habsburg kings and queens by examining genealogical databases, which included more than 6,000 individuals belonging to more than 20 generations.
“Our main objective of our research is to understand the genetic architecture of the human face. And for that, we use the Habsburg as true human genetic laboratories. The main question is if the “Habsburg face” is affected by the inbreeding they practiced. The “Habsburg jaw” is not just a prognathism problem but the combination of two “issues”: mandibular prognathism (MP) and maxillary deficiency (MD). That is why it should be named “Habsburg face”. By studying the effect of inbreeding over those traits we can learn a lot about their genetic architecture: Is it ruled by a few genes with strong effects? Or by a plethora of genes with mild effects? Are these effects recessive or dominant?” Ceballos told ZME Science.
According to the results, Mary of Burgundy, who married into the family in 1477, showed the least degree of both traits. The most pronounced prognathism was found in Philip IV, King of Spain and Portugal, who ruled from 1621 to 1640. The greatest degree of maxillary deficiency was found in five family members: Maximilian I (regent from 1493), his daughter Margaret of Austria, his nephew Charles I of Spain, Charles’ great-grandson Philip IV and the last in the Habsburg line, Charles II.
The researchers analyzed the effects of inbreeding over the degree of mandibular prognathism and maxillary deficiency by employing statistical methods, finding that the two traits share a common genetic basis.
“The ‘Aha!’ moment was when we discovered that the MD is affected indeed by inbreeding, and that the Habsburg face is indeed related to their consanguinity. This is the first time that science backs up this statement,” Ceballos told me over e-mail.
It is yet unclear, however, how facial deformity and inbreeding are connected. That’s not to say that there aren’t any possible explanations. Mating between relatives is known to increase the odds of offspring inheriting identical forms of a gene from both parents (genetic homozygosity). This can reduce an individual’s genetic fitness. Charles V, for instance, was believed to suffer from at least two conditions caused by recessive mutations in different genes: pituitary hormone deficiency (which can result in infertility) and distal renal tubular acidosis, a cause of kidney failure.
“While our study is based on historical figures, inbreeding is still common in some geographical regions and among some religious and ethnic groups, so it’s important today to investigate the effects,” lead researcher Professor Roman Vilas from the University of Santiago de Compostela said in a statement. “The Habsburg dynasty serves as a kind of human laboratory for researchers to do so, because the range of inbreeding is so high.”
In the future, the research team plans on investigating the genetic architecture of the human face more broadly by including other royal dynasties.
“We were able to answer many questions, like the heritability of these traits and other insights of their genetic architecture. Also we are using these dynasties (not just the Habsburgs) to get insights into the genetics of fertility, life expectancy, etc. We also calculated the inbreeding coefficient of every royal family of Europe until nowadays,” Ceballos said.
“It is possible to study the genetics of the human face: the mirror of the soul by using the information we have about our European royals. As we have shown in different papers, these royal dynasties are a magnificent genetic human laboratory, where science, history and art come together. We can learn a lot of modern genetics from them, even without having any single molecule of DNA,” he concluded.
The findings appeared in the journal Annals of Human Biology.