Weird History
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How One Of The Most Powerful Families In History Destroyed Itself Through Inbreeding

Updated August 20, 2019 531.6k views11 items

The chaos of the Habsburg family tree brought down the dynasty and is one of the most famous cases of royal inbreeding throughout history. The Habsburg line traces its roots to the Middle Ages and extended its influence through the early 20th century. Some of the most famous names in European history had links to the family: Marie Antoinette was a Habusburg, as was Archduke Franz Ferdinand, the man whose death triggered the start of World War I.

Habsburg dynastic power reached its height in the 16th and 17th centuries. As the Spanish and Austrian lines of the House of Habsburg dominated Europe, they married one another and kept bloodlines pure. Cousins married cousins and uncles married nieces; keeping track of who was related to who in the complex matrix of the House of Habsburg inbreeding - not to mention how they were related - is mind-boggling to the modern observer.

Habsburg inbreeding and intermarriage brought together bloodlines in a way that caused physical and mental illnesses, ultimately resulting in infertility on a royal scale. Confusing and fascinating, the Habsburg dynasty inbred itself into oblivion.

  • Sixteenth Century Marriages Were All In The Family

    Photo: Artist Unknown / CC BY-SA 3.0

    Increasingly close connections of dynastic marriages within the Habsburg family became problematic from a genetic standpoint in the 16th century, though no one at the time could have possibly known. Interestingly, the Catholic Church had prohibitions on consanguinity (of the same blood lines) in marriage, but the Pope could, and often did, make allowances for royal families.

    With uncles marrying nieces, such as Phillip II of Spain to Anne of Austria in 1570 and Charles II of Austria to Maria Anna of Bavaria in 1571, familial loops closed into tighter and tighter circles. The products of those two marriages, Phillip III and Margarita of Austria, married each other.

  • Charles II Of Spain Was His Own Cousin

    Photo: Luca Giordano / CC BY-SA 3.0

    The more Habsburgs who married, the more incestuous the marriages became. Philip III of Spain and Margarita of Austria, who were the offspring of two uncle-niece couples, had two children, both of whom married relatives. Their daughter, Maria Anna of Spain, married Holy Roman Emperor Ferdinand III in 1631 and their son, Philip IV, married the daughter of his sister's marriage, Mariana of Austria, who was his niece and cousin in more than one way.  

    The best-known inbred Habsburg, Charles II of Spain, was a product of this marriage. He was born in 1661 as his own cousin. One of his grandmothers was also his aunt, the other also his great-grandmother. All of his great-grandparents were descended from the same couple, Philip I and Joann. 

    By the birth of Charles II, the Habsburg lines of Spain and Austria were so intertwined they were a genetic catastrophe. Charles II was infertile, had a tongue so large he could barely speak, possessed such an offset jaw his teeth couldn't meet, and was unable to walk until he was nearly fully grown, at which point he had such trouble walking he fell regularly. Charles II was the last ruler of Habsburg Spain; while the Austrian line continued, he marked the end of Habsburg dynastic dominance. 

  • The Holy Roman Empire Was Neither Holy Nor Roman - It Was Habsburg

    Photo: N3MO / Public Domain

    The Austrian Habsburgs controlled the position of Holy Roman Emperor from the 15th century to the early 19th. Even after Charles V of Spain abdicated the title in 1556, the connections between Spanish and Austrian Habsburgs to the role remained solid.

    Habsburg dominance of the title Holy Roman Emperor speaks to the tremendous reach of the family, which was achieved through intermarriage and breeding. To give some indication of the sprawl of Habsburg power, Holy Roman Emperor Charles VI held the following titles, all achieved through centuries of consanguineous marriage and breeding:

    • King of Germany
    • King of Bohemia
    • King of Hungary
    • King of Croatia
    • Archduke of Austria
    • King of Naples
    • King of Sicily
    • King of Sardinia
    • Duke of Luxemburg
    • Duke of Teschen
    • Duke of Parma and Piacenza
    • Count of Flanders
  • As The Family Declined, It Suffered Infant Death And Infertility

    Photo: Artist Unknown / Public Domain

    According to a 2009 genetics study published in multidisciplinary journal PLOS One:

    "[I]nfant and child mortality was very high in the Spanish Habsburg families. From 1527 to 1661, when Philip II and Charles II were born respectively, the Spanish royal families had 34 children, 10 (29.4%) of them died before 1 year, and 17 (50.0%) of these children died before 10 years."  

    The authors, Alvarez, Ceballos, and Quinteiro, argue that the high rate of infant and child deaths in the Habsburg family resulted from the intermarriage and inbreeding. The inbreeding coefficient, as they call it, grew over time; very little fresh blood entered the family line, making serious health problems inevitable. 

    Alvarez, Ceballos, and Quinteiro also looked at birthrates and found "there were 51 pregnancies in the eight families: 5 miscarriages and stillbirths, 6 neonatal deaths, 14 deaths between month 1 and year 10 and 26 survivals at age 10."

    Charles II was the apex of Habsburg inbreeding and how it affected the continuity of the family line. His parents, Philip IV and Mariana of Austria, had five children, only two of whom lived until adulthood. By the time Charles was born in 1661, he was the only surviving child. Charles II was married twice, but was unable to produce a child in either case.