Jaw-dropping secret of the Habsburg jaw
Regal feature seen as sign of blue blood ‘WAS spread by inbreeding’
THE jutting Habsburg jaw seen in some of Europe’s most prominent royal families has long been suspected to be the result of inbreeding.
Now scientists have shown a direct connection between marriages of people who are too closely related and the genetic condition.
The deformity was a distinctive feature of members of the Habsburg – or Hapsburg – dynasty of Spanish and Austrian kings and their wives for more than 200 years.
Research in the Annals of Human Biology combined diagnosis of facial deformities using historical portraits with genetic analysis of the degree of relatedness.
Lead researcher Professor Roman Vilas, of the University of Santiago de Compostela in Spain, said: ‘The Habsburg dynasty was one of the most influential in Europe, but became renowned for inbreeding, which was its eventual downfall.
‘We show for the first time that there is a clear positive relationship between inbreeding and appearance of the Habsburg jaw.’
Ten surgeons who specialise in the face and the jaw were asked to score the degree of severity of facial deformity in 66 portraits of 15 members of the Habsburgs.
They looked for 11 features of mandibular prognathism, or Habsburg jaw, as well as seven features of maxillary deficiency – the most recognisable of which are a prominent lower lip and an overhanging nasal tip.
They found the most pronounced effect of the first condition was in Philip IV, king of Spain from 1621 to 1665. And those most strongly affected by maxillary deficiency included Maximilian I (ruler of the Holy Roman Empire from 1493), his daughter Margaret of Austria and the last in the Habsburg line: Charles II, Philip IV’s son.
The scientists detected a strong relationship between the degrees of inbreeding and mandibular prognathism – as well as a less pronounced link between inbreeding and maxillary deficiency.
The study also found a link between the two conditions, suggesting Habsburg jaw is in fact characterised by them both and they share a genetic basis. The extent of inbreeding was calculated from a family tree including more than 6,000 individuals from more than 20 generations.
The authors say their findings are ‘the first evidence of inbreeding depression on the human face’.
Why inbreeding leads to the facial deformity is unclear. However, the experts suggest it is because mating with relatives increases chances of offspring inheriting identical forms of a gene from both parents.