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Categorizing Has Consequences

25 Eliezer_Yudkowsky 19 February 2008 01:40AM

Followup toFallacies of Compression

Among the many genetic variations and mutations you carry in your genome, there are a very few alleles you probably know—including those determining your blood type: the presence or absence of the A, B, and + antigens.  If you receive a blood transfusion containing an antigen you don't have, it will trigger an allergic reaction.  It was Karl Landsteiner's discovery of this fact, and how to test for compatible blood types, that made it possible to transfuse blood without killing the patient.  (1930 Nobel Prize in Medicine.)  Also, if a mother with blood type A (for example) bears a child with blood type A+, the mother may acquire an allergic reaction to the + antigen; if she has another child with blood type A+, the child will be in danger, unless the mother takes an allergic suppressant during pregnancy.  Thus people learn their blood types before they marry.

Oh, and also: people with blood type A are earnest and creative, while people with blood type B are wild and cheerful.  People with type O are agreeable and sociable, while people with type AB are cool and controlled. (You would think that O would be the absence of A and B, while AB would just be A plus B, but no...)  All this, according to the Japanese blood type theory of personality.  It would seem that blood type plays the role in Japan that astrological signs play in the West, right down to blood type horoscopes in the daily newspaper.

This fad is especially odd because blood types have never been mysterious, not in Japan and not anywhere.  We only know blood types even exist thanks to Karl Landsteiner.  No mystic witch doctor, no venerable sorcerer, ever said a word about blood types; there are no ancient, dusty scrolls to shroud the error in the aura of antiquity.  If the medical profession claimed tomorrow that it had all been a colossal hoax, we layfolk would not have one scrap of evidence from our unaided senses to contradict them.

There's never been a war between blood types.  There's never even been a political conflict between blood types.  The stereotypes must have arisen strictly from the mere existence of the labels.

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