He could barely eat because of his disfigured jaw. He suffered from rickets, hallucinations, and an oversized head. He was impotent and infertile. Charles II of Spain, king of one of the largest empires in the world, was barely able to talk or walk - all because his dynasty was so inbred.
Royal inbreeding caused mutations and birth defects that could be even worse than the already estimable genetic mutations from incest. In fact, Charles II of Spain's inbred birth made him more inbred than the children born of a union between brother and sister. And that's what ultimately explains Charles II of Spain's cause of death: by 35 all his hair fell out and he could barely walk, and before he turned 39 he died without an heir, plunging Europe into a bloody war as various nations vied for his crown.
Charles II of Spain's family tree was intentionally inbred. His father married his own niece, meaning that Charles's mother was also his cousin, and his dad was also his uncle. And that was just the beginning: the Spanish Habsburgs intermarried on purpose for over 200 years, making them among the weirdest royals in history.
With all these genetic issues, it's difficult not to wonder: what did Charles II of Spain look like? His prominent Habsburg jaw made it nearly impossible for the king to eat, and he constantly drooled. He was short, thin, and weak. But the family hired artists to make him look strong and healthy. Still, there was no hiding the outcome of centuries of inbreeding. Charles was the last Spanish Habsburg, a powerful dynasty that killed itself through inbreeding.
Although painters tried to depict Charles II as a healthy, strong king, they hid the truth of the ruler's genetic conditions. Charles suffered his entire life from frequent diarrhea and vomiting, among other genetic conditions that made him constantly ill. And he had the famous Habsburg jaw. The jutting jaw made it nearly impossible for Charles to chew his food, and his enormous tongue caused constant drooling.
And Charles didn't grow out of the problems. As an adult, he could barely speak because of his distorted face, and hardly anyone could understand him. Charles married twice - first at the age of 18, and then at 29 - but was unable to have children either time, with one wife complaining that Charles was impotent.
It's one thing to say that Charles's parents were uncle and niece. But the Habsburg gene pool was even worse than that specific relation would indicate, because the family had generations of inbreeding - all of which led to Charles II.
Two of Charles's great-grandfathers married their own nieces, while another married his first cousin. Because his parents were closely related, Charles was also his own mother's first cousin and his father's great-nephew. His grandmother was also his aunt. Charles's family tree traced back to a single couple: Philip and Joanna of Castile, who lived in the 16th century. Shockingly Charles's gene pool was so inbred that he was even more inbred than the offspring of a brother-sister mating.
Charles likely suffered from two genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis. The first, caused by a mutation in the gene necessary to produce hormones in the pituitary gland, was responsible for Charles's short stature, infertility, and impotence. It could also cause weak muscles and digestive problems.
The second, caused by a gene mutation, makes it difficult for the kidneys to get rid of acid through the urine. It can lead to bloody urine, weak muscles, and a large head relative to the size of the body. Research performed by scholar Gonzalo Alvarez from the University of Santiago de Compostela confirmed that inbreeding caused the downfall of the Habsburg dynasty.
Charles's father, King Philip IV, was only 10 years old when his parents arranged his first marriage, to the daughter of the French king. Out of their eight children, only two were boys, and both died before inheriting the throne. After the death of his first wife, Philip remarried his own niece, Mariana of Austria. The couple had two daughters and two more sons who died as children.
When the future Charles II was born in 1661, his parents must have thought he would not live long. Contemporary writings called the baby "big headed" and a "weak breast-fed baby." Charles did not speak until he turned four, and he was unable to walk until the age of eight. In spite of paintings that tried to show him as a healthy baby, Charles was weak and ailing from birth.