🚀 go-pugleaf

In <10276@ut-emx.UUCP> ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:
>Not being a geneticist, I have frequently wondered, but never looked into,
>the question of why an infrequent mutation like Tay-Sachs, which has such
>a devastating effect on those unfortunates who are homozygous for it, has
>such a relatively *high* incidence among Ashkenzaic Jewry (I believe that
>1/30 individuals is heterozygous).

I think I know the answer to this one, but you're not gonna like it...

A good friend of mine at UPenn was a pre-med who came from a family of
doctors (as a matter of fact, the fact that his uncle is a senior physician at
the medical school's hospital saved his life once, but that's another story).
The family was Ashkenazic Jewish, German overachiever subvariety.

Harry once told me that one of his doctor cousins had researched this problem
and come to some really startling conclusions (which, for reasons which
will become obvious, he never got to test conclusively).

Everybody know how the sickle-cell trait works in Blacks? If you're homozygotic
for it, you lose; it's lethal. But if you're heterozygotic for it, you win --
you're resistent to malaria. A useful adaptation for Blacks in sub-Saharan
Africa, so the trait is widespread in the Black population despite its
deadliness.

Harry's cousin guessed something similar might be true for Tay-Sachs. He
figured there had to have been some historically recent advantage to being
heterozygotic for the trait, or it'd have been selected right out.

So he went looking for a disease or other environmental factor that was
endemic to south central Russia and the Pripyet Marshes around the time the
ancestors of the Ashkenazim emerged as a distinct population there. Something
sufficiently dangerous that resistance to it was a net win over significantly
higher infant mortality; something for which no less costly adaptation has
been shown in any other human population; and something for which some later
suggestion of significant resistance in the Ashkenazim could be found.

He found it. A  bacterium called `pasteurella pestis' -- the bubonic plague.

I don't know if he ever tried controlled in vitro test of this hypothesis; in
vivo, of course, would be horribly dangerous. But if true, it would explain
an *awful* lot about the tragic history of the Jews in Europe. Perhaps the
Ashkenazim really *were* (inadvertent) plague-spreaders. Standard theory about
the ghettos escaping the worst effects because of `superior sanitation' always
had sounded kind of thin to me.

Someday I hope to read a definitive book on epidemiological catastrophies in
social history that features details on this one and the ergotism explanation
for the late-medieval witchcraft hysterias as star cases. Sadly, it hasn't been
written yet.
-- 
      Eric S. Raymond                     (the mad mastermind of TMN-Netnews)
      Email: eric@snark.uu.net                       CompuServe: [72037,2306]
      Post: 22 S. Warren Avenue, Malvern, PA 19355      Phone: (215)-296-5718