Abraham's genetic threads

By Razib Khan | May 15, 2012 11:46 pm

Every few days my Google Alerts have been dropping in my inbox reviews of Harry Osters’ Legacy: A Genetic History of the Jewish People. The latest is in the The Tablet, A Case for Genetic Jewishness:

For a Jewish genetics researcher, being told in print that ‘Hitler would certainly have been very pleased’ by your work can’t be pleasant. But that’s what happened in 2010 to Harry Ostrer, a geneticist at the Albert Einstein College of Medicine, when he and his colleagues published a study showing that Jews in three different geographical areas had certain collections of genes that made them more biologically similar to one another than they were to non-Jews in the same regions. The work also showed that Jews around the world could trace their ancestry to a group of people who lived in the Middle East 2,000 years ago; that meant, however, that certain genetic signatures could be used to identify Jews, indicating that Jews share a common biological identity beyond their religious affiliation—which is what inspired the Hitler crack.

I don’t plan on reading Legacy because I already read the paper which it is based on, Abraham’s Children in the Genome Era: Major Jewish Diaspora Populations Comprise Distinct Genetic Clusters with Shared Middle Eastern Ancestry. It is now open access, so you can read it too. As implied in the article in The Tablet the biggest finding in this paper is that most of the world’s Jewry seem to share tracts of the genome which are ‘identical by descent’ (IBD). You don’t have to be a geneticist to intuit that being IBD implies relatively recent and elevated shared descent from a common set of ancestors. In particular the authors were looking for segments of the genome where individuals shared the same sequence of genetic markers. Very long sequences indicate a relatively recent common ancestor, while many short ones suggest more distant but numerous common ancestors.

From looking at these patterns of relatedness the authors infer that despite the genetic variation in the modern Jewry, most of the world’s Jews, from Iran to Morocco to Lithuania, share common ancestry from a source population which flourished ~2,500 years ago. All that being said, genetics is only part of the puzzle here. In the discussion the authors suggest that “Yet, the sharing of Iranian and Iraqi Jews of a branch on the phylogenetic tree with the Adygei suggests that a certain degree of admixture may have occurred with local populations not included in this study.” I argue in my post The Assyrians and Jews: 3,000 years of common history, a clear and distinct category of “Jew” as opposed to generic North Levantine in the year 500 BC probably does not make biological sense, though it might make culturally sense (and “generic North Levantine” is obviously not accurate, as most of these individuals had strong tribal or ethnic identities at the time). Finally, I don’t think I highlighted in my earlier commentary that these data imply that the rise of Christianity and Islam fundamentally stabilized the genetics of the Jewish people, insofar as much of the admixture upon the core base in the peripheral populations seems to predate the rise of these religious civilizaitons. Once Christianity and Islam marginalized the Jews, the gene flow from non-Jews to Jews diminished greatly. This is curiously analogous to the cultural involution which Jews also underwent during this period.

CATEGORIZED UNDER: Anthroplogy, Human Genetics
MORE ABOUT: Human Genetics, Jews

Comments (15)

  1. Dm

    Once Christianity and Islam marginalized the Jews, the gene flow from non-Jews to Jews diminished greatly
    To presently extant Jews. The consequence of living in a diaspora for many generations, and at the same time being open to cultural and genetic inflows, is that one’s self-identification melts away as well. So there may have been a lot of strong inflows in some segments of the Jewish world, it’s just their descendants no longer identify as Jewish.

    Back 2,500 + ybp, since the Jewish population remained to a large extent a local majority group, there was little “identity survival penalty” of higher admixture rate, and that’s why we still see a strong genetic footprint from those days.

  2. Nihaya Khateb

    “genetics is only part of the puzzle” , I am convinced rather the opposite. The fact that Jews are still a “race” and are forming a distinct genetic comunity is a strong proof for the fact that genetic determinism is still matter. The solid fact that it is very hard to strangers to enter the jewish comunity contributes to these data about genetic stability for 2500 years. Statistically, only minority of the jews out-bred with other nations, so the major genom was preserved.

  3. #2, it’s cultural determinism. you’re confusing cause and effect. and #1 makes a good point. the jews of kaifeng disappeared in the 20th century in large part due to intermarriage. so the power of jewish nationhood in maintaining coherency is subject to an ascertainment bias.

  4. John Emerson

    Jews may not have wanted Hitler to know certain things, but Jews have traditionally believed that Jews are all kin.

  5. Tom Bri

    A question. To what extent do the non-Jewish populations in lands where Jews have lived for long periods, North Europe for example, show these same markers? I guess I am asking about the extent of outflow of genes from Jews to Gentiles, related to DM’s comment above.

  6. #5, random north europeans have jewish segments out of the blue. e.g., the pickrell affair. but it is a small number. not enough jews.

  7. #5, random north europeans have jewish segments out of the blue. e.g., the pickrell affair. but it is a small number. not enough jews.

  8. ryan

    What about in Spain, where there were repeated periods when people were forced into becoming conversos, some of whom kept their faith hidden (and may ultimately have rejoined Jewish communities elsewhere), but many others of whom simply became Catholics?

  9. ryan

    I didn’t find any discussion of Spanish populations in Abraham’s Children. Basques are among the reference populations they look closely at, but I doubt that’s what you’re pointing me to. Are you referring to another paper or did I miss something in Abraham’s Children?

  10. #10, popres data set has spaniards. if they found something they probably would have reported it. i ran IBS with ashkenazi jews once and other europeans. don’t recall them being that close to the ashk jews (though that’s a summary, not ibd).

  11. ryan

    Well, as you know the relationship would likely be stronger with Sephardis than with Ashkenazim. I don’t draw any conclusions from the fact these authors didn’t report on any Iberian populations. They also didn’t report on Assyrian Christians, a population that your recent post suggested had quite close relationships to certain Jewish populations. I think there are things missing here, perhaps to intentionally emphasize discrete boundaries over continuities, though their aside about the Adygei and “populations not included” suggests less polemical intent. It does leave me wondering.

  12. #12, they’d need to do some rather sophisticated analysis to discern what you are wondering about. the reason is simple: the authors argue that the substantial european admixture into ashkenazi and sephardic jews is from western mediterranean populations. this includes the iberians. so you need to trace IBD, but differentiate that IBD ~2,000 years ago, to IBD ~1,000 years ago. i know some researchers who are doing this with european data, and the time intervals are going to be very wide (and these are people with more computational resources than this team).

  13. Paul Givargidze

    @ ryan: Dr. Ostrer and I traded a few emails a couple of years ago regarding the testing of Assyrians. I got the impression he was genuinely interested in including Assyrians as part of a future analysis of the Near East. So, hopefully, one day, we will see something from his team.

    I would like to add three additional notes regarding possible Assyrian-Jewish genetic links, presumably from a very distant time in the past:

    1. Genetic screening in the Persian Jewish community: A pilot study. Kaback et al. 2010

    “Pseudocholinesterase deficiency…BCHE is the name for the genetic locus: an autosomal recessive condition common within the Persian and Iraqi Jewish populations.”

    “Approximately 1 in 10 Persian Jews were found to be heterozygotes for a single point mutation in this gene.”

    Based on the very limited number of Assyrians tested at 23andMe, carrier incidence in Assyrians for this condition may be similar to that observed in Iraqi and Iranian Jews. My mother and I included.

    2. Screening for Carriers of Tay-Sachs Disease among Ashkenazi Jews — A Comparison of DNA-Based and Enzyme-Based Tests. Triggs-Raine et al. 1990

    “Our DNA analyses of obligate carriers of Tay-Sachs disease identified all the common mutations known to cause the disease in the Ashkenazi population. The three known mutations accounted for 98 percent (61 of 62) of the mutant alleles in the group of Ashkenazi obligate carriers. The frequency of identified mutations increases to 99 percent (93 of 94) of the alleles of all patients and carriers, or to 99 percent (78 of 79) of the alleles of all patients with infantile disease, if other obligate carriers described in the literature are included. These mutations were not restricted to the Ashkenazi population, since the insertion mutation was found in four non-Ashkenazi subjects, and the exon 7 mutation in a non-Ashkenazi (described as Assyrian) patient.”

    3. Possible Y chromosome links between Assyrian and Ashkenazi men (e.g. L943).

  14. Dm

    #8 Ryan, Conversos didn’t “simply” become regular Catholics, there still had their separate identity partly by coercion, partly by choice. And soon, the Crowns moved to expel the Conversos and the Moriscos out of Iberia, ensuring that their contribution to the gene pool of modern Spain is small. The great expulsions brought most of the “recent converts” to North Africa, but many went to the Colonies too, resulting in documented traces of Sephardic admixture across Latin America and in South Asia.

    As Razib recently discussed in Cuba threads, Middle Eastern and/or North African components of Cuban genotypes can’t be explained by a much smaller admixture in today’s Spaniards … but perhaps can be explained by the enrichment in Conversos and Moriscos in the early Colonial migration out of Spain and Portugal.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com


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