The Hapsburgs or House of Austria was a royal dynasty in Europe often associated with having a prominent jawline called “Hapsburg Jaw,” as evident in their surviving portraits. Charles II (see photo above), dubbed the most inbred Hapsburg in history, had a slew of physical disabilities, which researchers suggested was a result of inheriting highly recessive, harmful genes from the then-common practice of marrying and having children between close relatives.
It’s a popular notion that inbreeding results in physical deformity, however one researcher wanted to point out that inbreeding does not necessarily cause, but it exacerbates certain, already existing family traits. So, 100 years of inbreeding down the line, what was once a trait for a perfectly acceptable but still big chin from uncle Philip manifests in the next generation of royalty as an obviously dysmorphic lower face.
The prominent jawline feature is a complex trait, meaning it is a result of many different genes that are either dominant or recessive.
You can find more historical Hapsburg portraits at The Metropolitan Museum of Art in New York, The Prado (Madrid), or Kunsthistorisches Museum (Vienna).
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(Image Credit: Juan de Miranda Carreno / Wikimedia Commons)