Here are two researches which examine the Slavic-Turkic origins of the Ashkenazim Jews:
1- The Ashkenazic Jews: A Slavo-Turkic People in Search of a Jewish Identity, by Paul Wexler, Publisher: Slavica Pub; First edition. (December 1, 1993), ISBN-10: 0893572411
2- Jewish European Ancestry: Contrasting the Rhineland and the Khazarian Hypotheses by Eran Israeli-Elhaik, Department of Mental Health, Johns Hopkins University Bloomberg School of Public Health, McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Published: 14 December 2012
The Ashkenazic Jews: A Slavo-Turkic People in Search of a Jewish Identity, by Paul Wexler
This book, a linguist’s reassessment of early European Jewish history, will be of interest to anyone who has ever wondered how the Jewish people, lacking their own territorial base and living as a minority among often hostile non-Jewish peoples over the four corners of the globe, succeeded in preserving a separate identity for close to two thousand years.
The book makes a number of innovative and controversial claims about the relationship of the contemporary Jews to the Old Palestinian Jews. Recognizing the limitations of historical documentation, this book shows how facts about Yiddish and Modern Israeli Hebrew (presented in four recent books) can assist historians and archeologists in evaluating known data and artifacts as well as generate a new hypothesis about the origins of the Ashkenazic Jews, the north European Jews who have consituted the majority of the Jews in the world for the last several centuries.
In Wexler’s view, the Ashkenazic Jews most likely descend from a minority ethnic Palestinian Jewish emigre population that intermarried with a much larger heterogeneous population of converts to Judaism from Asia Minor, the Balkans and the Germano-Sorb lands (the Sorbs are a West Slavic population that still numbers about 70,000 in the former German Democratic Republic). Widespread conversions to Judaism that began in Asia Minor in the Christian era and ended with the institutionalization of Christianity among the Western Slavs in the beginning of the second millennium saved the tiny ethnic Palestinian Jewish population in the diaspora from total extinction.
The major non-Jewish contributors to the ethnogenesis of the Ashkenazic Jews were Slavs, though there was probably also a minor Turkic strain — both in the Caspian-Black Sea area (the descendants of the Khazars, a mainly Turkic group that converted to Judaism in the eighth century) and in the Balkans and Hungary. In all of these areas, the Turkic population early became submerged with the coterritorial Slavs. In addition to Yiddish terms of Slavic, Greek, Romance and German origin which express aspects of the Jewish religion and folk culture, the book shows that many elements of Ashkenazic folklore and religion themselves were of Slavic origin — either West (Sorbian and Polabian) or Balkan Slavic.
There is a lengthy discussion of the evidence for widespread conversion to Judaism in Asia Minor, southern Europe and the Germano-Sorbian lands up to the twelfth century and the reasons why pagan and Christian Slavs converted to Judaism. While historians have been disputing the extent of conversion to Judaism, Wexler thinks the linguistic and ethnographic evidence make the conversion evidence highly plausible. In addition, Jewish linguistic evidence refutes the traditional claims that Yiddish is a variant of High German and that Modern Hebrew is a “revived” form of Old Hebrew; new hypotheses are proposed: that Yiddish began as a Slavic language (specifically a Judaized form of Sorbian) that was re-lexified to High German at an early date, and that Modern Hebrew is, in turn, Yiddish that became re-lexified to Hebrew, and thus is also a form of Sorbian.
These facts support the author’s hypothesis of the Slavic origins of the Ashkenazic Jews, and the bulk of their religion and folk culture. The book proceeds to show how, under the conditions of relative separation from the non-Jewish population that developed after the twelfth century, the north European Jews developed elaborate processes of “Judaizing” their pagan and Christian Slavic religion and folk culture — by inserting unusually large amounts of Hebrew elements into colloquial Judeo-Sorbian/Yiddish and by reinterpreting and recalibrating religious and ethnographic practices according to biblical and talmudic precedents; customs known to be obsolete among the Christians were retained by the Jews as “Jewish” practices.
For example, the Slavo-Germanic glass-breaking ceremony intended to scare the devil away from the merrymakers at a wedding, was reinterpreted as remembrance of the destructions of the two Temples in Jerusalem. The ethnographic and religious evidence is taken mainly from discussions in the Germano-Slavic Hebrew religious literature of the thirteenth through sixteenth centuries which reveal that many rabbis were quite aware of the non-Jewish origins of Ashkenazic folklore and religious practices. Where the rabbis could not convince the masses to abandon pagan-Christian customs, they were obliged to retain them, but in a “Judaized” form. The book offers a correction to the unsubstantiated views of the late Arthur Koestler in his The Thirteenth Tribe (London 1976), that the Ashkenazic Jews are largely descended from Turkic Khazars who converted to Judaism in the Caucasus in the eighth century.
Wexler believes Koestler was right about a Slavo-Turkic basis for the north European Jews — but that he erred in assuming the preponderence of Turks over other ethnic groups, and in placing the “homeland” of the Ashkenazic Jews in the Caucasus. Where Koestler’s evidence, mainly non-linguistic, was scanty and totally unreliable, Yiddish and Ashkenazic folk culture and religion provide a wealth of varied evidence that support a primarily Slavic ethnic origin for the Ashkenazic Jews.
In opposition to the popular view that the Slavic imprint in Ashkenazic Jewish culture is a “late borrowing”, Wexler sees the Slavic elements as an “inheritance” from the pagan Slavic cultures which were to become for the most part submerged and reformed under the impact of Christianity.
Hence, Ashkenazic Judaism is essentially a Judaized form of Slavic pagan and Christian culture and religion (rather than an uninterrupted evolution of Palestinian Judaism) — and the best repository of pagan Slavic folk culture that survives to our days. Wexler also proposes that the other Jewish diasporas — e.g. the Sephardic, the Arab, Iranian, Chinese, Indian, Ethiopian and Yemenite — are also largely of non-Jewish origin.
The book compares the notion of Jewish peoplehood with attempts at rewriting the past found in many other societies. There is a bibliography of some seven hundred items and an index of examples.
Jewish European Ancestry: Contrasting the Rhineland and the Khazarian Hypotheses, by Eran Israeli-Elhaik
The question of Jewish ancestry has been the subject of controversy for over two centuries and has yet to be resolved. The “Rhineland hypothesis” depicts Eastern European Jews as a “population isolate” that emerged from a small group of German Jews who migrated eastward and expanded rapidly. Alternatively, the “Khazarian hypothesis” suggests that Eastern European Jews descended from the Khazars, anamalgam of Turkic clans that settled the Caucasus in the early centuries CE and converted to Judaism in the 8th century. Mesopotamian and Greco–Roman Jews continuously reinforced the Judaized Empire until the 13th century.
Following the collapse of their Empire, the Judeo–Khazars ﬂed to Eastern Europe. The rise of European Jewry is therefore explained by the contribution of the Judeo–Khazars. Thus far, however, the Khazars’ contribution has been estimated only empirically, as the absence of genome-wide data from Caucasus populations precluded testing the Khazarian hypothesis. Recent sequencing of modern Caucasus populations prompted us to revisit the Khazarian hypothesis and compare it with the Rhineland hypothesis.
We applied a wide range of population genetic analyses to compare these two hypotheses. Our ﬁndings support the Khazarian hypothesis and portray the European Jewish genome as a mosaic of Near Eastern-Caucasus, European, and Semitic ancestries, thereby consolidating previous contradictory reports of Jewish ancestry. We further describe a major difference among Caucasus populations explained by the early presence of Judeans in the Southern and Central Caucasus. Our results have important implications for the demographic forces that shaped the genetic diversity in the Caucasus and for medical studies.
Contemporary Eastern European Jews comprise the largest ethno-religious aggregate of modern Jewish communities, accounting for approximately 90% of over 13 million Jews worldwide (Ostrer 2001). Speculated to have emerged from a small Central European founder group and thought to have maintained high endogamy, Eastern European Jews are considered a “population isolate” and invaluable subjects in disease studies (Carmeli 2004), although their ancestry remains debatable between geneticists, historians, and linguists (Wexler 1993; Brook 2006; Sand 2009; Behar et al. 2010).
Recently, several large-scale studies have attempted to chart the genetic diversity of Jewish populations by genotyping Eurasian Jewish and non-Jewish populations (Conrad et al. 2006; Kopelman et al. 2009; Behar et al. 2010). Interestingly, some of these studies linked Caucasus populations with Eastern European Jews, at odds with the narrative of a Central European founder group. Because correcting for population structure and using suitable controls are critical in medical studies, it is vital to examine the hypotheses purporting to explain the ancestry of Eastern and Central European Jews.
One of the major challenges for any hypothesis is to explain the massive presence of Jews in Eastern Europe, estimated at eight million people at the beginning of the 20th century. We investigate the genetic structure of European Jews, by applying a wide range of analyses— including three population test, principal component, biogeographical origin, admixture, identity by descent (IBD), allele sharing distance, and uniparental analyses—and test their veracity in light of the two dominant hypotheses depicting either a sole Middle Eastern ancestry or a mixed Middle Eastern–Caucasus–European ancestry to explain the ancestry of Eastern European Jews.
The “Rhineland hypothesis” envisions modern European Jews to be the descendents of the Judeans—an assortment of Israelite–Canaanite tribes of Semitic origin (ﬁgs. 1 and 2) (supplementary note S1, Supplementary Material online). It proposes two mass migratory waves: the ﬁrst occurred over the 200 years following the Muslim conquest of Palestine (638 CE) and consisted of devoted Judeans who left Muslim Palestine for Europe (Dinur 1961).
Whether these migrants joined the existing Judaized Greco–Roman communities is unclear, as is the extent of their contribution to the Southern European gene pool. The second wave occurred at the beginning of the 15th century by a group of 50,000 German Jews who migrated eastward and ushered an apparent hyper baby-boom era for half a millennium (Atzmon et al. 2010). The Rhineland hypothesis predicts a Middle Eastern ancestry to European Jews and high genetic similarity among European Jews (Ostrer 2001; Atzmon et al. 2010; Behar et al. 2010).
The competing “Khazarian hypothesis” considers Eastern European Jews to be the descendants of Khazars (supplementary note S1, Supplementary Material online). The Khazars were a confederation of Slavic, Scythian, Hunnic–Bulgar, Iranian, Alans, and Turkish tribes who formed in the central–northern Caucasus one of most powerful empires during the late Iron Age and converted to Judaism in the 8th century CE (ﬁgs. 1 and 2) (Polak 1951; Brook 2006; Sand 2009).
The Khazarian, Armenian, and Georgian populations forged from this amalgamation of tribes (Polak 1951) were followed by relative isolation, differentiation, and genetic drift in situ (Balanovsky et al. 2011). Biblical and archeological records allude to active trade relationships between Proto-Judeans and Armenians in the late centuries BCE (Polak 1951; Finkelstein and Silberman 2002), that likely resulted in a small scale admixture between these populations and a Judean presence in the Caucasus.
After their conversion to Judaism, the population structure of the Judeo–Khazars was further reshaped by multiple migrations of Jews from the Byzantine Empire and Caliphate to the Khazarian Empire (ﬁg. 1). Following the collapse of their empire and the Black Death (1347–1348) the Judeo–Khazars ﬂed westward (Baron 1993), settling in the rising Polish Kingdom and Hungary (Polak 1951) and eventually spreading to Central and Western Europe.
The Khazarian hypothesis posits that European Jews are comprised of Caucasus, European, and Middle Eastern ancestries. Moreover, European Jewish communities are expected to be different from one another both in ancestry and genetic heterogeneity. The Khazarian hypothesis also offers two explanations for the genetic diversity in Caucasus groups ﬁrst by the multiple migration waves to Khazaria during the 6th–10th centuries and second by the Judeo–Khazars who remained in the Caucasus.