Italian Ancestry of Ashkenazi Jews

March 8, 2014

Genetic similarities between Italians and Ashkenazi Jews are due to the fact that about half of Jews' ancestry is European, a lot of which came from Italy when diaspora males migrated to Rome and found wives among local women who then converted to Judaism. The same process happened again to a lesser degree in other parts of Europe as Jews migrated further north, west and then east, but according to genome-wide autosomal DNA, their highest European admixture is Italian.

Overall, it seems that at least 80% of Ashkenazi maternal ancestry is due to the assimilation of mtDNAs indigenous to Europe, most likely through conversion. The phylogenetic nesting patterns suggest that the most frequent of the Ashkenazi mtDNA lineages were assimilated in Western Europe, ~2 ka or slightly earlier. Some in particular, including N1b2, M1a1b, K1a9 and perhaps even the major K1a1b1, point to a north Mediterranean source. It seems likely that the major founders were the result of the earliest and presumably most profound wave of founder effects, from the Mediterranean northwards into central Europe, and that most of the minor founders were assimilated in west/central Europe within the last 1,500 years. The sharing of rarer lineages with Eastern European populations may indicate further assimilation in some cases, but can often be explained by exchange via intermarriage in the reverse direction.

The Ashkenazim therefore resemble Jewish communities in Eastern Africa and India, and possibly also others across the Near East, Caucasus and Central Asia, which also carry a substantial fraction of maternal lineages from their 'host' communities. Despite widely differing interpretations of autosomal data, these results in fact fit well with genome-wide studies, which imply a significant European component, with particularly close relationships to Italians. As might be expected from the autosomal picture, Y-chromosome studies generally show the opposite trend to mtDNA (with a predominantly Near Eastern source) with the exception of the large fraction of European ancestry seen in Ashkenazi Levites.

Evidence for haplotype sharing with non-Ashkenazi Jews for each of the three main haplogroup K founders may imply a partial common ancestry in Mediterranean Europe for Ashkenazi and Spanish-exile Sephardic Jews, but may also, at least in part, be due to subsequent gene flow, especially into Bulgaria and Turkey, both of which witnessed substantial immigration from Ashkenazi communities in the fourteenth and fifteenth centuries. Gene flow could have been substantial in some cases—ongoing intermarriage is likely when these communities began living in closer proximity after the Spanish exile. A partial common ancestry for all European Jews—both Ashkenazi and Sephardic—is again strongly supported by the autosomal results.

Jewish communities were already spread across the Graeco-Roman and Persian world >2,000 years ago. It is thought that a substantial Jewish community was present in Rome from at least the mid-second century BCE, maintaining links to Jerusalem and numbering 30,000-50,000 by the first half of the first century CE. By the end of the first millennium CE, Ashkenazi communities were historically visible along the Rhine valley in Germany. After the wave of expulsions in Western Europe during the fifteenth century, they began to disperse once more, into Eastern Europe.

These analyses suggest that the first major wave of assimilation probably took place in Mediterranean Europe, most likely in the Italian peninsula ~2 ka, with substantial further assimilation of minor founders in west/central Europe. There is less evidence for assimilation in Eastern Europe, and almost none for a source in the North Caucasus/Chuvashia, as would be predicted by the Khazar hypothesis—rather, the results show strong genetic continuities between west and east European Ashkenazi communities, albeit with gradual clines of frequency of founders between east and west.

Costa et al. "A substantial prehistoric European ancestry amongst Ashkenazi maternal lineages". Nature Communications, 2013.

Admixture between previously diverged populations yields patterns of genetic variation that can aid in understanding migrations and natural selection. An understanding of individual admixture (IA) is also important when conducting association studies in admixed populations. However, genetic drift, in combination with shallow allele frequency differences between ancestral populations, can make admixture estimation by the usual methods challenging. We have, therefore, developed a simple but robust method for ancestry estimation using a linear model to estimate allele frequencies in the admixed individual or sample as a function of ancestral allele frequencies. The model works well because it allows for random fluctuation in the observed allele frequencies from the expected frequencies based on the admixture estimation. We present results involving 3,366 Ashkenazi Jews (AJ) who are part of the Kaiser Permanente Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort and genotyped at 674,000 SNPs, and compare them to the results of identical analyses for 2,768 GERA African Americans (AA). For the analysis of the AJ, we included surrogate Middle Eastern, Italian, French, Russian, and Caucasus subgroups to represent the ancestral populations. For the African Americans, we used surrogate Africans and Northern Europeans as ancestors. For the AJ, we estimated mean ancestral proportions of 0.380, 0.305, 0.113, 0.041 and 0.148 for Middle Eastern, Italian, French, Russian and Caucasus ancestry, respectively. For the African Americans, we obtained estimated means of 0.745 and 0.248 for African and European ancestry, respectively. We also noted considerably less variation in the individual admixture proportions for the AJ (s.d. = .02 to .05) compared to the AA (s.d.= .15), consistent with an older age of admixture for the former. From the linear model regression analysis on the entire population, we also obtain estimates of goodness of fit by r2. For the analysis of AJ, the r2 was 0.977; for the analysis of the AA, the r2 was 0.994, suggesting that genetic drift has played a more prominent role in determining the AJ allele frequencies. This was confirmed by examination of the distribution of differences for the observed versus predicted allele frequencies. As compared to the African Americans, the AJ differences were significantly larger, and presented some outliers which may have been the target of selection (e.g. in the HLA region on chromosome 6p).

Banda et al. "Admixture Estimation in a Founder Population". Am Soc Hum Genet, 2013.

Two major differences among the populations in this study were the high degree of European admixture (30%-60%) among the Ashkenazi, Sephardic, Italian, and Syrian Jews and the genetic proximity of these populations to each other compared to their proximity to Iranian and Iraqi Jews. This time of a split between Middle Eastern Iraqi and Iranian Jews and European/Syrian Jews, calculated by simulation and comparison of length distributions of IBD segments, is 100–150 generations, compatible with a historical divide that is reported to have occurred more than 2500 years ago. The Middle Eastern populations were formed by Jews in the Babylonian and Persian empires who are thought to have remained geographically continuous in those locales. In contrast, the other Jewish populations were formed more recently from Jews who migrated or were expelled from Palestine and from individuals who were converted to Judaism during Hellenic-Hasmonean times, when proselytism was a common Jewish practice. During Greco-Roman times, recorded mass conversions led to 6 million people practicing Judaism in Roman times or up to 10% of the population of the Roman Empire. Thus, the genetic proximity of these European/Syrian Jewish populations, including Ashkenazi Jews, to each other and to French, Northern Italian, and Sardinian populations favors the idea of non-Semitic Mediterranean ancestry in the formation of the European/Syrian Jewish groups and is incompatible with theories that Ashkenazi Jews are for the most part the direct lineal descendants of converted Khazars or Slavs. The genetic proximity of Ashkenazi Jews to southern European populations has been observed in several other recent studies.

Atzmon et al. "Abraham's Children in the Genome Era: Major Jewish Diaspora Populations Comprise Distinct Genetic Clusters with Shared Middle Eastern Ancestry". Am J Hum Genet, 2010.

7 comments

Maternal grandma said...

What happened, genetically to the thousands of Roman/Italian converts to Juadaism (e.g. emperor Titus's sister)whose descendants followed the Gothic kings into Rhineland and N. France in the early dark ages? There were numerous Greek-speaking synagogues in ancient Rome and a few Latin-speaking synagoges as well. Is there genetic studies showing the date of the admixture in ancient times between Italians, Greeks, and Jews living in Italy who left the country later? For example, there was a Jewish migration from Lucca to Mainz in 920 CE as the Ashkenazi communities were being established there which later migrated to Lithuania and then to Poland. National Genographic Project gives the Ashkenazi DNA of some as 54% Greek or Tuscan and 21% Iranian (ancient DNA admixture) along with 19% N. European and 2% African, 4% E. Asian, where the East Asian comes from the 5% E. Asian in most Iranians. Any clues on Ashkenazim being partly descended from Italians and Greeks mixed with Persians? Thanks for any references to articles.

starfishlady said...

I think it's a mistake with the way they are interpreting the test. I think that what they are picking up is that all the people of the Mediterranean are related to a single group in ages past. For example, my dad's line started out in Babylon just like the legendary Abraham.

Paul renan-zelezniak said...

I think the Italian interpretation is probably correct - DNA test interpretations need historical support, and the conversion of Italian women was indeed historically recorded. One only needs to read the New Testament to read of these unions, if not involving conversion, at least marriage ( ie Timothy had a Greek father and a Jewish mother )

Jules said...

To Maternal Grandma,
Where did you read that Nat. Geo is doing this?
"National Genographic Project gives the Ashkenazi DNA of some as 54% Greek or Tuscan and 21% Iranian (ancient DNA admixture) along with 19% N. European and 2% African, 4% E. Asian, where the East Asian comes from the 5% E. Asian in most Iranians. Any clues on Ashkenazim being partly descended from Italians and Greeks mixed with Persians?"
I've never seen an article on Genographic stating this and have not seen Dr. Spencer Wells give a speech on this. There is no Ashkenazim grouping listed on Genographic and I thought they just looked at individual markers. They don't seem to compare one group to another as in recent ancestry, but look for markers that a particular population is known for. If those markers fall into Tuscan or Greek, then that is what you are. I am northern Italian and Genographic lists me as Tuscan. I've seen South Italians come in with an Ashkenazi percentage on 23andMe, but never a Tuscan or Northern Italian. Just curious if you could post where you heard this. It is very interesting. I know that South Italians often get confused with Ashkenazi and on Gedmatch they have the AJ population between Southern Italy and Greece. I'd love to know the science of how they pull apart a South Italian from an Ashkenazi person, since both have Levant admixture automatically. Seeing all the South Italians come in with 11 to 14% Ashkenazi on Gedmatch, makes me wonder whether you can pull apart the two populations. I don't see why they'd put them between Greek and Tuscan, since the Tuscans do not come in with Ashkenazi ancestry, unless they really have that ancestry. I do believe that the Ashkenazim might have a significant South Italian ancestry from Roman times onward. They were in Southern Italy a very long time. Greeks and Southern Italians mixed with the Levant people during Hellenistic times. All Europeans come from the people who were in Persia and Iran at some point in time... making all of this yet harder to pull apart.

Jules said...

PS... I think I understand what you are saying Maternal grandma. I have not seen those kinds of results with Ashkenazi people who have done both 23andMe and Genographic. Not one has said they come out with that combination. Usually the person was found to be related to the Greeks (southern Italians) and also come in with a certain northern European component as well as a south Asian component, etc. So they will list Greek and Lebanese, as well as saying they are 60% Mediterranean, 20% northern European and the rest is generic south Asian at 20%. I've never seen them come in with 2% African or 4% E. Asian. I've never seen them come out related to Iranians. I've never seen them come out as Tuscan, but I gather if you are Italkim, then that might be in there. I've seen Lenbonese, but not Iranian. Interesting.

Jules said...

Edit: I meant to say southwest Asian component of 20%. Sorry I misspelled Lebanese.

Anne Hart said...

I'm Greek with pre-1840 relatives from Salonika. When I used to date Greeks pre 1963, the first question the male asked me was whether I was from Cyprus or Turkey. I have no idea why it would matter whether my distant relatives in the far past came from S. or N. Greece, the islands, or the southern part of Greece. My neighbors in Brooklyn's Little Italy of the 1950s was mostly Sicilian. We all look Middle Eastern, but a few Greeks did have red hair and blue or gray eyes. Thought it was fascinating. Proud to be Greek.