Sickle-cell anemia is a truly discriminating disease: 99% of its U.S. victims are black. The result of a genetic mutation that occurred in Africa centuries ago, it reduces susceptibility to malaria in the 8% to 10% of U.S. Negroes who carry it. But in those (about 1%) actually harmed by it, periodic crises distort the normally spherical red blood cells into crescent-like ("sickle") structures, which then block the narrow capillaries. This deprives nearby tissues of needed oxygen and causes severe pain. The disease kills at least half its victims before the age of 20; only a handful live beyond 40, and...
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