Tuesday, June 07, 2005

Ashkenazic genetics

A new study, claiming that Ashkenazic Jews underwent a process of natural selection that made them especially intelligent, is making waves in the media. I fully admit I don't understand much of what I read about it. But the gist seems to be this: the genetic diseases which are almost unique to Ashkenazic Jews reveal something about the genesis of Ashkenazic genes. The evidence points, according to this study, to a process of natural selection. What kind of selection would be taking place? Presumably one that was influenced by the concentration of Jews in commerce and their need for high intelligence.

This sounds kind of strange to me. I will try to present some of the facts of early medieval Jewish demographics, to the limited extent that I understand them. First of all, Jews continued to work in a range of occupations, including agriculture, into the 11th century. Haym Soloveitchik recently showed how deeply Jews were involved in wine production in Germany, into the 14th century. Though it doesn't seem to be explicit there (his emphasis is on their economic involvement), halachic considerations demand that at least some of the physical work was being done by Jews. [H. Soloveitchik, Principles and Pressures: Jewish Trade in Gentile Wine in the Middle Ages, Tel Aviv 2003, pp. 80-90 and passim]

Update: I need to add this quote from a short piece on the same topic that Soloveitchik published in English.

"And, in an era before Jews are identified with credit, neither did their
Christian neighbours see them as creditors, anymore than customers of today view Bloomingdale's or Marks and Spencer as creditors rather
than as merchants."

Haym Soloveitchik, 'Halakhah, Taboo and Moneylending', The Jews of
Europe in the Middle Ages (Tenth to Fifteenth Centuries):
Proceedings of the
International Symposium held at Speyer, 20-25 October 2002
, ed. Christoph
Cluse, Turnhout 2004, p. 301

Second, they lived in very small communities. These communities tended to consist of one or two extended families, which gave rise to the problem of convening a court that did not include relatives of either side in a dispute. [H. Soloveitchik, The Use of Responsa as a Historical Source: A Methodological Introduction, Jerusalem 1990, p. 30]

Third, nuclear families tended to be fairly small (Grossman thinks that Stow's conclusion, that the rate of growth was almost negative, but they were still not very large - four children). [A Grossman, The Early Sages of Ashkenaz, 2nd ed., Jerusalem 1988, p. 441]

Doesn't it make more sense to simply assume that all this created a very limited gene pool?


Blogger micha said...

The idea of limited gene pool is favored among Jewish historians. (As told to me by R' Dr David Berger [no relation].)

However, it doesn't quite work for a different reason. Ashkenazi and Sepharadi IQ on mathematics and learning capacity (the latter being Prof. Reuvein Feuersteun's "Intrumental Enrichment" theory.

IOW, they show no difference in intelligence in any domain where socioeconomic factors play a minimimal role. Which means we need an explanation that covers a far wider population than the original Ashkenazim.

3:46 PM  
Anonymous francine marino said...

I also found the theory unsound considering that Tay Sachs causes massive and global neurological deterioration rendering the child, among other things, profoundly retarded. What intellectual edge did the researchers see in that genetic illness?

I'll go with your explanation.

Keep those enlightening and entertaining nuggets coming!

Francine Marino

6:13 PM  

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