Most of us know that incest is wrong, either through cultural conditioning or what appear to be innate evolutionary cues, yet some humans can’t seem to resist the urge to have sex with their relatives. In fact, since the DNA of every living human is 99.9 percent the same, it may be much more common than we think. Still, that doesn’t mean incest can be acceptable in any case. As we will see, breeding with a close relative can result in some dire consequences.
Tut’s family members weren’t the only royals to dip their pens in the family ink. Throughout the ages, incest among royal families was common and even encouraged in order to retain the purity of the bloodline. For two centuries, the Spanish Habsburg dynasty refused to share their power with outsiders, so they continued to inbreed with one another. This practice eventually led to their downfall in 1700, when King Charles II died without an heir.
The Habsburg family was so intent on keeping their royal blood pure that, prior to Charles’s death, 9 of the 11 marriages recorded during the dynasty’s 200-year reign were between biological relatives. Starting in 1550, nobody within the dynasty married outside of their family . Charles himself was the offspring of an uncle-niece marriage. By some estimations, he was one of the most inbred people in history, with 95.3 percent of his genes traceable to just five ancestors. One biography described poor Charles as having an “an enormous misshapen head” and a huge tongue. He also had a jaw that “stood so much out that his two rows of teeth could not meet,” which caused frequent drooling, an inability to chew, and extreme difficulty speaking. Other accounts said the king suffered from intestinal upsets, convulsions, premature ejaculation, and impotence.
Though the dynasty may be long gone, at least its name continues to live on among dental professionals. The condition called prognathism, which is a protruding lower jaw, has been nicknamed “Habsburg jaw” in homage to the impotent, drooling, big-headed king.