Royal incest: the arguments for


Over at National Geographic I’ve a short piece on why royals often enjoy an exemption from the incest taboo. The piece is a sidebar to a splendid article by National Geographic science editor Jamie Shreeve on King Tut’s DNA, which revealed, among other things, that boy-king’s parents were siblings. The magazine wanted to put this rather shocking news in context, so they asked me to write about why incestuous marriages and matings have not been terribly uncommon among royalty through the ages.

Or as the article’s subtitle puts it, “Why King Tut’s family was not the only royalty to have close relations among its close relations. ” 650 words or less. Part of the result:

Overlapping genes can backfire. Siblings share half their genes on average, as do parents and offspring. First cousins’ genomes overlap 12.5 percent. Matings between close relatives can raise the danger that harmful recessive genes, especially if combined repeatedly through generations, will match up in the offspring, leading to elevated chances of health or developmental problems—perhaps Tut’s partially cleft palate and congenitally deformed foot or Charles’s small stature and impotence.

If the royals knew of these potential downsides, they chose to ignore them. According to Stanford University classics professor Walter Scheidel, one reason is that “incest sets them apart.” Royal incest occurs mainly in societies where rulers have tremendous power and no peers, except the gods. Since gods marry each other, so should royals.

Incest also protects royal assets. Marrying family members ensures that a king will share riches, privilege, and power only with people already his relatives. In dominant, centralized societies such as ancient Egypt or Inca Peru, this can mean limiting the mating circle to immediate family. In societies with overlapping cultures, as in second-millennium Europe, it can mean marrying extended family members from other regimes to forge alliances while keeping power among kin.

And the hazards, while real, are not absolute. Even the high rates of genetic overlap generated in the offspring of sibling unions, for instance, can create more healthy children than sick ones. And royal wealth can help offset some medical conditions; Charles II [a Hapsburg king who suffered terrible congenital problems because he came from a heavily inbred family] lived far better (and probably longer, dying at age 38) than he would have were he a peasant.

A king or a pharaoh can also hedge the risk of his incestuous bets by placing wagers elsewhere. He can mate, as Stanford classicist Josiah Ober notes, “with pretty much anybody he wants to.” Inca ruler Huayna Capac (1493-1527), for instance, passed power not only to his son Huáscar, whose mother was Capac’s wife and sister, but also to his son Atahualpa, whose mother was apparently a consort. And King Rama V of Thailand (1873-1910) sired more than 70 children—some from marriages to half sisters but most with dozens of consorts and concubines. Such a ruler could opt to funnel wealth, security, education, and even political power to many of his children, regardless of the status of the mother. A geneticist would say he was offering his genes many paths to the future.

It’s a fun piece, methinks — fascinating to write, and it actually ends with a bit of a love story, set to island music. Check it out. And don’t miss the sumptuous article on Tut’s DNA.

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