Sunday, April 21, 2013

Natural Selection among the Hapsburgs

Philip II of Spain exhibited
the signature Hapsburg
pointed jaw.
Geneticists at a Spanish university claim that the Spanish Hapsburgs evolved to mute the effects of inbreeding. Inbred marriages, such as those between between first cousins or between uncles and nieces, were common in the Hapsburg pedigree and multiplied over time for political and dynastic reasons. Such marriages increased the odds that children would inherit two copies of a recessive mutation that causes disease or disability. Indeed, inbreeding was the probable cause for the high rates of disease in the Spanish royal family.

However,  natural selection might have played a role in weeding out those individuals who bore the worst disabilities so that mutations would not be passed on to subsequent generations. The scientists theorized that natural selection would operate through early death. If natural selection was indeed purging the family of harmful mutations, then early deaths would become less frequent over time. The scientists studied 4000 individuals across more than 20 generations of Hapsburgs and found evidence that there were substantially more deaths among the family's children between 1450 and 1600 than between 1600 and 1800. However, infant mortality rose over time, leading the geneticists to posit differences between the effects of very harmful mutations, which were eventually purged by natural selection, and mutations that caused problems only some of the time.

Other geneticists disagree with the researchers' conclusions. You can read the article here.

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