Royal Inbreeding and the Hapsburg Jaw

If you've viewed exhibits of European portraits and noticed some with prominent lower jaws and lower lips, you'd have seen evidence of the Hapsburg jaw. That's a genetic disorder from something called consanguineous marriage. Or, to put it simply, inbreeding which royal families did to keep blood lines pure. They didn't know it would cause congenital deformities.

The origin of the Hapsburg jaw may be in a Polish royal family with Maximilian the First, a Holy Roman Emperor from the fifteenth century. Many generations of royal inbreeding spread the Hapsburg jaw throughout Medieval Europe.

The Hapsburg dynasty ended with King Carlos the Second of Spain whose tongue was so large he couldn't chew or talk well and drooled. He was intellectually disabled and died just short of his thirty-ninth birthday.

To confirm that marriage with relatives closer than second cousins caused the Hapsburg jaw, ten maxillofacial surgeons viewed sixty-six portraits of fifteen members of the Hapsburg dynasty. They looked for eleven features of the disorder and found them in at least seven family members. Researchers also studied a family tree that included six thousand people over twenty generations and established a link between inbreeding and the disorder.

Today, consanguineous marriage still exists in parts of the world. In the US, marriage between first cousins is illegal in half the states' but legal or not, even between second cousins it's frowned on for good reason.