The term “Habsburg jaw” references a jaw deformity present in many members of a German royal family collectively known as the Habsburgs. The deformity is believed to be a combination of two conditions that may share the same genetic causes. These conditions are mandibular prognathism and maxillary deficiency. Mandibular prognathism is a protrusion of the lower jaw while maxillary deficiency is an underdevelopment of the upper jaw. The severity of these conditions within the Habsburg family is thought to be the result of the inbreeding that they practiced in order to retain their power.
Typically, inbreeding causes certain traits because it increases the likelihood that anyone who is the result of the practice will receive the same mutation from both parents. This inheritance increases instances of conditions that, to be present, require a mutation on both of an individual’s versions of a gene. However, Habsburg jaw is a bit different because the conditions that cause it are generally believed to result from single genetic mutations. This may mean that it was not the presence of the characteristic itself but the degree of its severity that was caused by incest.
The Pedigree
The Habsburgs’ practice of inbreeding originated from the very beginning of their dynasty and increased throughout the generations. Between the years 1516 and 1700 A.D., about 80 percent of the marriages within the Habsburg clan were incestuous. This included relationships between first cousins and even double-first cousins. Ultimately, their long history of inbreeding led to the destruction of their male line.
The Last Habsburg
Though King Charles II of Spain was not the last Habsburg descendant, his death marked the end of the official male line of the dynasty. He suffered so greatly with his jaw deformity that he was known to have difficulty speaking and could not press his upper and lower rows of teeth together. Unfortunately, he also had other health issues that are thought to be because of his family’s inbreeding. His legs could not support his weight and he was believed to be infertile. He married twice but could not produce any children before his premature death due to poor health at just 39 years old. As he had no heirs, his death caused a 12-year war in Europe and brought a sad end to the infamous Habsburg dynasty.
