We Jews call ourselves a family, and in many ways — for better and for worse — we act as if we were. We continue to preserve common laws, habits, language, texts and historical memories, as well as the belief that all of these are the gifts of an unknowable Deity who began our place in history by exchanging covenantal promises with our ancestors Abraham, Isaac, Jacob and then — at Sinai, this coming week on Shavuot — with the descendants of Jacob’s sons.
We have preserved these shared habits and beliefs for millennia, over a large fraction of the populated world. They are the very model of strong ideas in action. They exemplify the durability and reality of religious belief in the unknowable, and the survival of belief in the face of millennia of risk.
Do these facts mean that the Jews of today are a biological family as well, linked by descent from shared ancestors? There are no DNA sequences common to all Jews and absent from all non-Jews; there is nothing in the human genome that makes or diagnoses a person as a Jew.
Why, then, has there been such a fuss about the recent pre-publication release of a report, “Natural History of Ashkenazi Intelligence,” by three researchers at the University of Utah?
It has been taken by some as proof that indeed Jews are genetically different from others, and moreover, that because the differences are in the biology of intelligence, Jews are simply born smarter. But the paper says no such thing.
In fact, it does not say anything in particular about Jews as a whole. As its title indicates, it is a paper about the intelligence of today’s Ashkenazim, the people — Jews or the descendants of Jews who no longer consider themselves Jewish — whose ancestors arrived in Europe after the fall of the Second Temple, survived expulsions from England, France and Germany in the 1200s to 1400s, pogroms in Poland and Lithuania in the 1500s and 1600s, exterminations in Nazi-occupied Europe from 1939 to 1945, gulags and forced secularization in the former Soviet Union until the 1990s, and are alive today.
This review of many studies from many laboratories presents some interesting findings about Ashkenazim today, and a testable hypothesis to explain them. The argument goes like this:
First, that adult intelligence measured by IQ tests shows today’s Ashkenazim to be about 10 IQ points sharper in quantitative and abstract skills than their non-Ashkenazic neighbors in America, Europe and Israel;
Second, that for the 1,500 years beginning about 600 C.E., Ashkenazim could support themselves only in work that required ease and subtlety with numbers and abstract ideas — forget Tevye, think Shylock;
Third, that this IQ difference is inherited as a greater brain size and complexity;
Fourth, that these biological differences are the expression of genetic differences that have the side effect of producing some children with Ashkenazic inherited disease;
And finally, that therefore the biological burden of the diseases associated with Ashkenazim — both the cancer-associated ones like BRCA-1 mutation and the nerve-cell storage diseases like Tay-Sachs — are the byproducts of 1,500 years of externally-imposed genetic selection for high IQ.
There are many problems with accepting this case.
First, it adds complexity to a simpler explanation — that is, that the Ashkenazim are the descendents of a small number of survivors of pogroms, and that these inherited diseases are not the byproduct of a useful thing like high IQ, but are simply the inherited token of ancient persecutions.
Second, it argues for inheritance of some aspects of intelligence without others, an outcome that seems hard to understand in the bigger-and-better-brain model they propose.
Third, where it is simply testable, the tests to prove their hypothesis are not done: if carriers of the mutations associated Tay-Sachs, BRCA-1 and the like are benefiting from having inherited bigger and better brains, then they should outstrip their non-carrier siblings in IQ tests.
And finally, it argues that Ashkenazim are the product of unique circumstances and offers no strong evidence for a comparable example elsewhere, a serious flaw in any scientific hypothesis.
But let us say for the sake of argument that further work will show this paper to be correct, and that Ashkenazim as a population have higher IQs as part of their birthright. Is this good for the Jews? It is neither good nor bad. It is simply irrelevant; Judaism is not inherited through DNA.
The paper reports that the Ashkenazic genetic differences from the rest of their North European neighbors are not found in Sephardic and Yemenite families who make up the majority of the Jews of Israel. On the other hand, the DNA evidence reported here tells us that, on average over the many generations of the last two millennia, about one in 200 ancestors of today’s Ashkenazim were themselves the children of at least one non-Jewish parent. Forgetting that King David’s ancestors included Ruth the Moabite, some may wish to think that Ashkenazim have no non-Jewish ancestors, but the evidence goes the other way.
The Jews of centuries ago who codified prayers understood that while being born a Jew was precious and important, it was not necessary and it certainly was not sufficient. The central ideas and actions of a Jew have always had to be taught and learned; they have never been inherited.
Like every creator of the texts that make up the canon of today’s Judaism — from Ezra the Scribe, through the redactors of the Mishnah, to the creators of the Babylonian and Jerusalem Talmuds, to certainly Rambam if not also Rashi — the majority of Israelis today would not have, nor need, the presumptive advantages of a supercharged Ashkenazic IQ. Nor is this a Jewish problem, because whether Ashkenazim inherited a cluster of genetic diseases through selection for high IQ or for any other reason, they still have and will continue to have the same Jewish obligation to teach their children from these texts, and to say the Sh’ma to remind themselves of this obligation, twice every day.
People — our species — are one family in precisely the same way that Jews are not. However the story of Ashkenazic inherited diseases comes out, the facts already known should make us all sensitive to the larger issues of inherited disease, and of genetic difference. In light of the DNA evidence we already have, the Jewish obligation to stretch the definition of normal variation to include the greatest possible diversity of inherited appearances and capacities is as clear in its own way as the countervailing trend is in current medical science.
Robert Pollack is a professor of biological sciences and director of the Center for the Study of Science and Religion at Columbia University.