The Gene Wars

By Diana Muir Appelbaum, Paul S. Appelbaum

What can science teach us about the validity of nationalist claims?

In each case, genetic data would seem to lend scientific proof to these groups’ claims of historical primacy. After all, if Philip of Macedon’s blood courses through the veins of the Macedonians, but not the Greeks, then Macedonian arguments for political control of his historical kingdom would appear to be enhanced in some ineffable way. Whether genetic data can carry this burden of proof is a question to which we will turn shortly; first, however, it is important to recognize that not everything purporting to be good genetics actually is. Many of the data or interpretations thereupon that have been enlisted in the gene wars are of dubious validity—including those relied upon by the Macedonians, Sami, and Palestinians. Given that claims of this sort are only likely to increase as more genetic data become available, understanding the problems with the methods and conclusions of these studies is essential to evaluating the contentions of competing groups.

Complex genetic studies are inherently challenging for the layman to assess. In theory, the peer review process used by scientific journals to determine which papers to accept for publication should ensure that published findings do not suffer from obvious flaws. But the process is imperfect, and the result is a body of scientific literature riddled with work of questionable validity, by virtue of either the data generated or the interpretations offered. The studies relied on by Macedonians, Sami, and Palestinians each illustrate some of the problems that afflict this area of research.

Recall that Macedonian claims are based on a single study showing Greeks to have a disproportionate percentage of sub-Saharan alleles of a particular cell surface marker, compared to the more typically Mediterranean pattern that they themselves display.³⁶ The authors of this study succumbed to what can only be called scientific hubris in asserting that the cultural, historical, and genetic identity of Macedonians may be established according to their results. If there is a cardinal rule of science, it is to be exceedingly leery of drawing conclusions on the basis of a single study. After all, extraordinary claims such as this demand the strongest levels of proof. In the absence of any plausible basis on which to assert that modern Greeks descend in substantial part from sub-Saharan Africans, only truly convincing data, replicated independently, should be accepted as proof of that claim.

The primary defect of the Macedonian study is that the authors relied on a single genetic marker, the HLA-DRB1 gene, to determine the genetic closeness of a large number of ethnic groups from Africa, the Near East, and the Mediterranean. Commenting on the work of this research group, Luigi Luca Cavalli-Sforza—probably the world’s leading expert on studies of this sort—and his colleagues stated, “Using results from the analysis of a single marker, particularly one likely to have undergone selection, for the purpose of reconstructing genealogies is unreliable and unacceptable practice in population genetics.”³⁷ How many markers are appropriate? Experts suggest that distinguishing reliably between even distantly related groups from different continents requires roughly 60 SNPs for 90-percent accuracy, and perhaps 100-160 for 99-100-percent accuracy.38 Even if a smaller number of haplotypes can be used on account of their relatively unique characteristics (each haplotype incorporates multiple SNPs or other mutations), the right number for assessing the relatedness of populations will never be just one. As Cavalli-Sforza and colleagues conclude, “the ordinary process of [peer review]” should preclude publication of papers of this sort.³⁹

Indeed, when another research group attempted to replicate the analysis of the HLA-DRB1 allele distributions among Macedonians, they found that their closest relatives were—of all peoples—the Greeks, the very group from which the Macedonians have been attempting to distinguish themselves.⁴⁰ As would be expected, Macedonians and Greeks clustered with other European populations on genetic maps, far from the aggregation of North African and sub-Saharan groups. Although these results have not stopped Macedonian nationalists from proclaiming their lineage superior to that of the Greeks, they effectively neutralize the earlier study, leaving Macedonians bereft of scientific support for their claims.

A much larger body of work exists on Sami genetics—which creates its own set of problems. Studies of Sami mitochondrial DNA do indeed suggest links to ancient European populations, but examination of the Y chromosomes of the Sami presents a different picture. Studies have shown that many Sami men carry Y chromosome markers associated with other Finno-Ugric-speaking populations, such as Estonians and Finns.⁴¹ The expansion of Finno-Ugric-that is, the moment when the group speaking the parental language broke up, and languages in the family begin to diverge—is dated by linguists to between 4,000 and 6,000 years ago. Which is to say, Finno-Ugric speakers likely arrived after the post-glacial re-settlement of Scandinavia.⁴²

The most probable explanation, though debates over the interpretation of the genetic data continue, is that as the glaciers receded from Europe, the continent was re-populated from southwest to northeast by survivors who had taken refuge in southern Europe. Sami carry a higher percentage of mitochondrial DNA markers from this group than do most European populations, and from this derive their assertions of indigeneity. Several thousand years later, the now-dominant Indo-European groups arrived from the east and, in all likelihood, some time later the major Finno-Ugric migration—carrying the markers found on many Sami Y chromosomes—began.⁴³ Thus, based on their maternally transmitted DNA, we might say that the Sami are an ancient, indigenous population; looking at their paternal line, however, we might conclude that they are more recent arrivals even than the Scandinavian groups with which they contend for territorial sovereignty.⁴⁴ In other words, like most ethnic groups today, Sami genetics reflect a mixture of populations over the millennia. Advocates, however, can be counted on to select the most supportive findings, and assertions of Sami indigeneity are never tempered by references to the Y chromosome data that undercut the absolute nature of the Sami narrative.⁴⁵

The comparative genetics of Palestinians and Jews demonstrate other pitfalls in generating and interpreting data. When populations are genetically diverse for the markers of interest, as most groups are, the selection of the samples to be studied is crucial. Since the numbers of subjects involved are usually small by epidemiologic standards, selecting a truly representative group is critical to drawing valid conclusions. For example, the study that compared HLA cell surface markers in Palestinians and Jews looked at 165 Palestinians, 94 Moroccan Jews, and 80 each of Ashkenazi and “non-Ashkenazi” Jews, and it is not clear that efforts were made to avoid sampling persons from the same extended family, clan, or region, and who may thus bias the results toward their particular genetic profile.⁴⁶ Likewise, is it unclear whether consideration was given to sampling those local populations most likely to have deep indigeneity in the region, such as Samaritans, Palestinian Christians, and Aramaic-speaking Christians. Surprisingly, many genetic studies provide little information about how their subjects were selected and what their characteristics are. For some kinds of medical research, whether the sample studied is representative of a broader population makes little difference. But when conclusions are being generalized to entire ethnic groups, what may be methodological fine points in other circumstances here become critical.

Moreover, given that current contentions about the genetic basis for Palestinian claims of historical primacy (or at least equality) are based on studies demonstrating similarity between Palestinian and Jewish genomes, the question “Compared to what?” becomes vital. For instance, when researchers at the Hebrew University reported “substantial overlap” between Israeli and Palestinian Arab Y chromosome haplotypes and those of Jews, they compared both groups to a sample drawn from northern Wales.⁴⁷ Of course, when compared with people from Wales, Jews and Arabs indeed look quite similar. However, when they compared Israeli Jews with the same Arab sample, but this time included comparisons with Kurds, Armenians, Turks, Syrians, Jordanians, Lebanese, and Bedouin, the picture looked quite different. Although all of the Middle Eastern populations bore some similarities to each other (a fairly robust finding confirmed in other works), “Jews were found to be more closely related to groups in the north of the Fertile Crescent (Kurds, Turks, and Armenians) than to their Arab neighbors.”⁴⁸ For some, this will evoke the biblical account of Abraham’s origins in Ur of the Chaldees, and raise the possibility that the story contains echoes of an ancient population movement. Alternatively, Jews, Kurds, Armenians, and Anatolian Turks may all carry the genetic markers of ancient indigenous populations of the Fertile Crescent, while Palestinian Arabs and Bedouin may largely descend from the Arab conquerors, with their distinctive genetic signifiers. All these hypotheses are highly tentative until confirmed or disproved by further genetic data. What is certain, however, is that one gets a very different picture of the genetic relatedness of Jews and Palestinians when their respective genetic portfolios are placed in the context of the Middle East, rather than compared with distant Wales.

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