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Maybe the princess shouldn’t marry her uncle.

Tease: Maybe the princess shouldn’t marry her uncle.


Intro: Welcome to “Dumb Ideas that Changed the World.” The views expressed are solely those of the host and do not reflect the opinions of this station or its funders.


“Blue bloods” and “good breeding” conjure images of elites and aristocracy. Or, maybe you think people should rise and fall on their own merits—without arranged marriages to protect old bloodlines.


In the old world, good breeding meant marrying close cousins, or uncles, or cousins who were also uncles! Inbreeding became as valued as wealth in maintaining hereditary power in the upper classes.


Was preserving royal blood a good idea? I mean, no one does the same thing for a thousand years unless it works, right? Well, no.


UCLA’s Sebastian Ottinger studied royal endogamy and state performance over nine centuries. The results were clear and disturbing: inbreeding was strongly linked to government failure. The territory of kingdoms contracted, along with the national economy. Good things happened when the monarch came from diverse bloodlines; calamity when the opposite was true.


Centuries of inbreeding ravaged the Habsburgs, who ruled much of Europe. King Charles the Second is the poster boy, with his mental deficiency, grotesque “Habsburg jaw,” and infertility that ended the dynasty in Spain. He was so inbred that his parents were genetically closer than if they’d been brother and sister. That’s just dumb.


You may think I’m committing an unfair hindsight bias. “How could they know?” But you would be wrong. The dangers of inbreeding were well known to the Catholic Church, which fought to outlaw it ever since the sixth-century. Meticulous records allowed French Catholics to forbid marriage even to a sixth cousin. Now that’s a diverse gene pool. The Aristocracy observed these strict rules, but royal families across Europe flouted them. The church always competed with old marriage customs, winning some and losing some.


Harvard’s Joe Henrich says the church’s success in promoting outsider marriage, known as exogamy, was not only healthier, but paved the way for individual rights, creativity, and democracy. Now that’s a smart idea.


I’m Jeff Gentry



Best reference: Ottinger, S., & Voigtländer, N. (2021). History’s Masters: The Effect of European Monarchs on State Performance. NBER Working Papers, 2830428382, 1–36.


Dumb Ideas that Changed the World copyright 2023 by Jeff Gentry. All rights reserved.

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