No. 119: Sep-Oct 1998
Plagues are not all bad, and the Black Death (bubonic plague) that swept into Europe from Asia in 1346 was no exception.
It is now common knowledge that bacteria, insects, plants, and even humans can build up resistances to poisons, diseases, and antibiotics.
Mutations are always occurring; some good, some neutral, some bad. It has been found that a human mutation designated CCR5-delta 32 confers immunity to AIDS if inherited from both parents. People carrying the CCR5-delta 32 mutation lack the receptors to which the AIDS virus must attach itself if it is to infect the person.
What has all this to do with the Black Death?
"Although the origin of the mutation is obscure, it appears to have suddenly become relatively common among white Europeans about 700 years ago. That increase suggests that something must have occurred about that time to greatly favor the survival of people carrying the mutation."
What biological catastrophe decimated Europe 700 years ago? The Black Death. One-quarter to one-third of the Europeans succumbed between 1347 and 1350. The Black Death strongly modified the European gene pool, increasing the frequency of CCR5-delta 32. This mutation may not have had any direct effect on the plague itself. It may just be a quirk of fate that the survivors of the Black Death had a higher frequency of the CCR5-delta 32 mutation, and it is doubly quirky that the mutation confers a resistance to AIDS, which is a recent human affliction.
About 10% of whites of European origin now carry the CCR5-delta 32 mutation. The incidence is only 2% in central Asia. The mutation is completely absent among East Asians, Africans, and American Indians.
(Brown, David; "AIDS Resistance Might Be a Legacy of Plague Survival," Dallas Morning News, May 18, 1998. Cr. D. Phelps)
Comment. This is all very interesting but also totally circumstantial.