New York Review of Books
Richard C. Lewontin
December 6, 2012
Legacy: A Genetic History of the Jewish People
by Harry Ostrer
Oxford University Press, 264 pp., $24.95
The Genealogical Science: The Search for Jewish Origins and the Politics of Epistemology
by Nadia Abu El-Haj
University of Chicago Press, 311 pp., $35.00
Palazzo Patriarchale, Udine/De Agostini Picture Library/Bridgeman Art Library
Giovanni Battista Tiepolo: The Sacrifice of Isaac (detail), 1726–1739
The question of ancestry has been of human concern in virtually all cultures and over all times of which we have any knowledge. Whether it be a story about the origin of a particular tribe or nation and its subsequent mixture with other groups, or curiosity about a family history, there is always the implication that we understand ourselves better if we know our ancestors and that we, within ourselves, reflect properties that have come to us by an unbroken line from past generations. As treasurer of the Marlboro Historical Society in Vermont, I am the recipient of requests for printed copies of the Reverend Ephraim Newton’s mid-eighteenth-century history of our town, 70 percent of whose pages consist of “Genealogical and Biographical Notes” and a “Catalog of Literary Men.” Over and over our correspondents write of the “pride” they have in descending from these early settlers.
Surely pride or shame are appropriate sentiments for actions for which we ourselves are in some way responsible. Why, then, do we feel pride (or shame) for the actions of others over whom we can have had no influence? Do we, in this way, achieve a false modesty or relieve ourselves of the burdens of our own behavior? As a descendant of late-nineteenth-century Eastern European immigrants I cannot depend on Reverend Newton’s pages to explain my frequent contributions to The New York Review , but neither have the extensive “begats” in Genesis 10 or Matthew 1 been more enlightening.
My own skepticism notwithstanding, the belief is widespread that knowledge about the personal characteristics of ancestors who have never directly entered into our lives is relevant to our own formation. Moreover, that relevance is seen not simply as arising from our conscious knowledge about those ancestors, but from a deeper source, our genetical inheritance, which also would operate to form us in part, irrespective of our consciousness of the past. That belief is summed up in the title of Harry Ostrer’s book, Legacy: A Genetic History of the Jewish People . It is also implied in the title of a book by Raphael Falk, Zionism and the Biology of the Jews , whose English translation from the Hebrew original has yet to appear. 1 While the term “race” is not used explicitly in these titles, in large part because the term is so loaded, there is considerable discussion of the Jews as a race or, using a less charged word, as a “people.”
“Race” is a term of uncertain etymology and many meanings. It may refer to a whole species (the “human race”), a collection of loosely related individuals with a common appearance (the “white race”), a nation (the “race of Englishmen”), or a single family (“he was the last of his race”). Compounding the ambiguity is the substitution of “people” or “tribe” that seems to shed the historical fardels with which “race” is burdened. Are the Navajo a tribe, a people, or even a race? In a former time, when the classification of humans depended on manifest physical features like skin color, facial and hair form, and skull shape, members of a “race” as opposed to a “people” were claimed to be recognizable as such by the external physical features common to all individuals of the same “race.”
In all these usages the implication is one of common ancestry tracing back ultimately to some relevant founding group, but obviously all such ancestries must incorporate members of other groups at various times in their histories. Even Cain managed to find a wife in the Land of Nod or else he married his sister. For the German National Socialists, having more than two Jewish grandparents was sufficient to define a Jew. But if every defined human group necessarily has, at any moment in its history, some ancestry from a variety of other collections of humans, how are we to delineate those groups and reconstruct their family histories?
Ordinary genetics is not sufficient. Each of us has one copy of our chromosomes from our mother and one copy from our father. But of the chromosomes I got from my mother, half of those came from her mother and half from her father so, roughly speaking, I resemble my maternal grandmother only in a quarter of my genes. It doesn’t take many generations before I resemble a particular remote great-grandparent in a very small fraction of my genes. If one of my ancestors four generations ago were black, there is a good chance I would have inherited none of her pigment genes or so few that they would not be apparent in my own skin color.
This random inheritance of genes makes it very difficult to reconstruct the variety of ancestors in remote past generations. Fortunately for those interested in the reconstruction of ancestry there are two useful exceptions to the rule that we inherit only a random one of the two sets of genetic information possessed by each of our parents. One of those exceptions is the single Y chromosome carried by males but not by females. The Y chromosome carries very few genes. We know this to be true because, very rarely, an individual is born having received, as usual, one X chromosome from the female parent but, abnormally, neither an additional X chromosome nor a Y chromosome from the male parent. This individual, called an “XO” type, is a sterile female but otherwise is normal. This general normality in the face of having only a single X chromosome but no Y chromosome tells us that the usual effect of a Y chromosome is essentially only to cause a switch from female to male development.
As a consequence, variation among Y chromosomes can be used to reconstruct ancestry without the confounding effect of possible natural selection for one or another variant. Every son inherits his father’s Y chromosome, which was passed, intact, through the sequence of male ancestors to the present generation. Thus, by examining the Y chromosome DNA from a group of males in some generation and comparing it to the Y chromosomes of various other populations, we can reconstruct the contribution of males from various sources in previous generations to the present population. In particular we can ask what proportion of the Y chromosomes in a given population came from some particular group of historical interest. For example, we can estimate how much Arab slave traders contributed genetically to the present black populations of southeast Africa if the Y chromosomes of the Arabs contain characteristic DNA sequences that are rare or absent elsewhere, but in unusually high frequency among the present African inhabitants of Tanzania.
The other exception to random inheritance is not in the chromosomes, but in cellular particles called ribosomes that contain not DNA but a related molecule, RNA, which has heritable variation and is of basic importance to cell metabolism and the synthesis of proteins. Although the cells of both sexes have ribosomes, they are inherited exclusively through their incorporation in the mother’s egg cell rather than through the father’s sperm. Our ribosomes, then, provide us, both male and female, with a record of our maternal ancestry, uncontaminated by their male partners.
Harry Ostrer, who is a professor of genetics at Albert Einstein College of Medicine, and Raphael Falk, who is one of Israel’s most prominent geneticists, depend heavily on our ability to trace ancestry by looking at the DNA of Y chromosomes and ribosomes. Their books are responses to the widespread desire to trace that ancestry and to describe the degree to which the world’s present distribution of Jews consists, with a few possible exceptions like the Kaifeng Jews of China, of people with ancient common roots. For Falk, as the child of German Jews threatened with the Final Solution, the longing for Zion was expressed, as in his parents’ case, “primarily as a wish for relief from the persecutions and other hardships of Jewish life in the Diaspora.” For Ostrer, on the other hand, as he writes in his preface:
The difference between the motivations of the authors is manifest in the properties each assigns to heredity. The element of “pride of ancestry” that permeates Ostrer’s text leads him, especially in his chapter on “Traits,” to extensive discussions of intellectual and professional accomplishment and the degree to which they may reflect innate biological capacity. While he can hardly be described as a naive biological determinist, it seems clear that he leans in the direction of attributing some importance to the biology of the Jews in forming their social accomplishments. He asserts that