A Reassessment of the Jewish DNA Evidence

Introduction

The word “Jew” has a mosaic of meanings: it defines a follower of the Jewish faith, a person who has at least one Jewish parent, or a member of a particular ethnic group (“Jewish”). There are many Jews who do not practice Judaism as a religion but define themselves as “Jewish” by virtue of their family’s heritage and identification with the culture and history of the Jewish people.

Thus, Judaism is a mosaic of culture, religion, ethnicity, and for some, a way of life. It is an identity that is not quite a nationality, but neither is it a simple ethnic or cultural phenomenon either. This unusual combination of characteristics, coupled with Jewish resistance over the centuries to assimilation and strong adherence to their religious faith, has contributed to the intense feelings of curiosity, hatred, admiration, attraction and hostility by the rest of the world.

Received: February 15, 2005

Address for correspondence: Ellen Coffman, Ellenlevy66@yahoo.com

Early on, the unique history of the Jews attracted DNA researchers who sought to solve the mystery of the origins of the Jewish people. Researchers had previously relied on linguistic, anthropological and archaeological evidence to try to address this question; genetic genealogical research has opened up a new area for researchers to explore.

One question the DNA studies sought to answer was whether the genetic ancestry of contemporary Jewish populations demonstrated, to any degree, their supposed descent from the ancient Israelites of the Middle East of three thousand years ago. Or rather, did the DNA evidence indicate that Jews were simply a people who came into being in Europe during the Diaspora years, being mainly comprised of those descended from European ancestors? Or, as some historical researchers suggested, did the DNA of Jews mainly reflect ancestry from the Khazars, an ancient tribal people with roots in both Central Asia and Russia who converted to Judaism in the 8^th century?

This paper represents a new examination and reassessment of the Jewish DNA studies to date, presenting possible alternative explanations for the origins and distribution of certain genetic markers among Jewish populations, and in particular, among the group of Jews known as “Ashkenazim.”

Recent genetic research has greatly expanded our understanding of the probable origins and distinct geographic patterns of certain groups of people, including Jews. This recent research has superceded some of the earlier studies on Jewish DNA, allowing a reassessment of the theories of Jewish origins in light of this new research.

The new analysis shows that Jewish ancestry reflects a mosaic of genetic sources. While earlier studies focused on the Middle Eastern component of Jewish DNA, new research has revealed that both Europeans and Central Asians also made significant genetic contributions to Jewish ancestry. Moreover, while the DNA studies have confirmed the close genetic interrelatedness of many Jewish communities, they have also confirmed what many suspected all along: Jews do not constitute a single group distinct from all others. Rather, modern Jews exhibit a diversity of genetic profiles, some reflective of their Semitic/Mediterranean ancestry, but others suggesting an origin in European and Central Asian groups. The blending of European, Semitic, Central Asian and Mediterranean heritage over the centuries has led to today’s Jewish populations.

In examining Y chromosomal diversity in this review, two types of data are considered: Single Nucleotide Polymorphisms (SNPs), and Short Tandem Repeat Loci (STRs). STR markers are characterized by mutation rates much higher than those seen with SNPs. SNPs, on the other hand, are derived from rare nucleotide changes along the Y chromosome, so-called unique event polymorphisms (UEP). These UEPs represent a single historical mutational event, occurring only once in the course of human evolution. UEPs have been given a unified nomenclature system by the Y Chromosome Consortium (2002), resulting in the identification of each UEP with a particular haplogroup.

While I examine both types of Y chromosome data, I rely primarily on SNP data due to its increasing use by researchers as a tool in reconstructing the peopling of the world. Research on the diversity and geographic patterns of haplogroups have provided researchers with a greatly expanded understanding of prehistoric movements of people and a means of better understanding the present-day genetic variation among populations. Research with STR “haplotypes” is also occasionally discussed in this paper, particularly in light of its ability to demonstrate a high rate of endogamy, genetic drift, and founder effects among Jewish populations.

Examination of mitochondrial DNA, on the other hand, is based on the combined polymorphisms of the control region (hypervariable segments I and II, or HVSI and HVSII) along with specific SNPs in the coding regions of DNA found in the mitochondria. Both males and females have mtDNA, which they have inherited from their mothers, whereas Y chromosome DNA is found only in males and is inherited directly from their fathers.

Like the Y chromosome data, mtDNA sequences are sorted into major phylogenetic haplogroups as well. Recent analysis on both mtDNA and Y chromosome SNPs have allowed researchers to further divide many haplogroups into sub-branches, known in the DNA literature as “sub-clades.” The geographic distribution of mtDNA haplogroups and their sub-clades also adds to our understanding of relationships of groups of people, including Jewish populations.

The Birth of European Judaism

This section is intended to provide the reader with a brief history of the Jews in Europe as well as define terms used frequently in the Jewish DNA studies, such as “Diaspora,” “Sephardim,” and “Ashkenazim.” Furthermore, since Jews appear to have both Israelite/Middle Eastern and European genetic ancestry, an understanding of the Jewish experience in Europe is important in explaining how European ancestry became an integral part of the Jewish genetic makeup. However, this section is not intended to be an extensive recounting of the history of the Ashkenazi people.

The birth of European Judaism begins with the Diaspora. “Diaspora” is a term derived from the Greek work meaning “scattering.” While the word was originally used by ancient peoples to identify any group that was exiled or resettled from their homeland, the term has now become particularly associated with the Jewish exile from ancient Israel and resettlement elsewhere.

The Jews resettled in many distant lands, even as far as China. This work, however, focuses specifically on the Ashkenazi Jewish experience. Jews were subdivided into groups depending on where they resettled. Ashkenazi Jews are the Jews of France, Germany, and Eastern Europe. Sephardic Jews are the Jews of Spain, Portugal and North Africa. Mizrachi/Oriental Jews are the Jews of the Middle East. Certain Jewish communities do not fit into these distinctive groupings – in particular, the Falasha Jews of Ethiopia and the Chinese Jews.

Contemporary Jewry is comprised of approximately 13 million people, of whom 5.7 million live in the United States, 4.7 million live in Israel, and the remainder resides throughout the world (Ostrer 2001). Approximately 90% of the Jews of the U.S. are of Ashkenazi origin, while among the Jews of Israel, 47% are Ashkenazi, 30% are Sephardic, and 23% are of Mizrachi/Oriental origin (Ostrer 2001). Within Jewish groups, membership in three male castes (Cohen, Levi, and Israelite) is determined by paternal descent (Behar et al. 2003).

The history and genetic ancestry of Sephardic Jews is dealt with in only a cursory fashion here. There have been only very limited genetic studies on Jews of Sephardic descent, while in contrast, many DNA studies have explored the genetic ancestry of Ashkenazi Jews. Thus, the primary focus of this work is on Ashkenazim DNA results, but also included is a comparison of Sephardic and Ashkenazi results pertaining to Y chromosome haplogroups J and E.

The word “Ashkenazi” is derived from the Hebrew word for Germany, while “Sephardic” is derived form the Hebrew word for Spain. The word “Ashkenazi” was first used in medieval rabbinical literature to define western European Jews. An interesting story was related by author Arthur Koestler, who noted that the term “Ashkenaz” is also mentioned in the Hebrew bible, referring to a people living somewhere in the vicinity of Armenia. Probably for this reason, the Khazars, a people who lived in and around this area in ancient times and converted to Judaism in the 7^th- 8^th centuries, came to believe they were the descendants of these biblical people. Some scholars argue that they began to call themselves “Ashkenazim” when they migrated to Poland in the 13^th century. Eventually, perhaps, the term came to describe the community as a whole, not just the Khazarian immigrants (Koestler 1976, pp. 181-182).

While the Jews of today are connected historically and religiously to the Jews of ancient Israel, the DNA evidence also indicates that a significant amount of Jewish ancestry can be traced directly back to their Israelite/Middle Eastern ancestors. However, these ancestors represented a heterogeneous mix of Semitic and Mediterranean groups, even at their very beginnings.

The Israelite Kingdom arose in the 11^th century BCE in an area between modern-day Lebanon, Jordan and Saudi Arabia. Current archaeological evidence indicates that the Israelite kingdom arose out of the earlier, Bronze Age Canaanite culture of that region, and displayed significant continuity with the Canaanites in culture, technology, language and ethnicity (Dever 2003, pp. 153-154).

While the Canaanites were a Western Semitic people indigenous to the area, they appear to have consisted of a diverse ethno-cultural mix from the earliest times. It is from this diverse group that the evolution of the Israelites occurred. Although little is known about these groups, they probably included some of the following populations:

Amorites: Western Semites like the Canaanites. They were probably the pastoral nomadic component of the Canaanite people.
Hittites: A non-Semitic people from Anatolia and Northern Syria.
Hurrians (Horites): A non-Semitic people who inhabited parts of Syria and Mesopotamia. Many kings of the early Canaanite city-states had Hurrian names.
Amalekites: Nomads from southern Transjordan. Even inimical references to this group in the Hebrew Bible “tacitly” acknowledge that the Israelites and Amalekites shared a common ancestry.
Philistines: Referred to in ancient texts as “Sea Peoples.” They invaded and settled along the coasts of ancient Canaan. Their culture appears to stem from that of Mycenae.

(Dever 2003, pp. 219-220).

While the Israelite kingdom clashed with a number of world powers over the centuries, including Egypt, Babylon, and Persia, it was the Romans who would destroy the Second Temple in 70 CE, violently sacking Jerusalem and scattering the Israelite population from their homeland. Many Jews were taken as slaves to Rome and its colonies (Konner 2003, p. 86). This watershed moment in the history of the Jewish people is often considered by many researchers to represent the true beginnings of the Jewish Diaspora.

Ironically, however, many scholars believe the Ashkenazi population probably had its earliest roots in Rome, where Jews began to establish communities as early as the second century B.C. While some of these Jews were brought to Rome as slaves, others settled there voluntarily. There were as many as 50,000 Jews in and around Rome by the first century CE, most who were “poor, Greek-speaking foreigners” scorned for their poverty and slave status (Konner 2003, p. 86). Eventually, however, many of these slaves gained their freedom, continuing to live in and around Rome.

By the first century, however, the Jewish Diaspora had already spread to a number of regions of the world, many of which may have contributed to the make-up of the early Ashkenazi Jewish community. These include the Aegean Island of Delos, Ostia (a main port of Rome), Alexandria, and other places in Macedonia and Asia Minor (Konner 2003, p. 83). Jews also began to migrate north of the Alps, probably from Italy (Ostrer 2001).

By 600 CE, Jews were present in many parts of Europe, with small settlements in Germany, France and Spain. More to the east, there were also small Jewish settlements along the Black Sea, as well as larger communities in Greece and the Balkans (Konner 2003, p. 110).

By the 12^th-13^th centuries CE, Jews were expelled from many countries of Western Europe, but were granted charters to settle in Poland and Lithuania (Ostrer 2001). The Ashkenazi Jewish population expanded rapidly in Eastern Europe, growing from an estimated 15,000-25,000 people in the 13^th-15^th centuries, to two million by 1800 and eight million in 1939 (Ostrer 2001, Behar 2004b). Thus, Jewish settlement in Eastern Europe became the dominant culture of the European Jews, and then of most Jews throughout the world.

The DNA Evidence for Israelite Ancestry: The Jewish Priests and Cohanim DNA Study

The search for Israelite/Middle Eastern DNA among contemporary Jewish populations properly begins with Dr. Karl Skorecki’s landmark genetic study of the Cohanim, the priests of the Jewish religion. The study came about based on the following story:

Dr. Skorecki, a Cohen of Eastern European descent (Ashkenazim), was attending synagogue one morning. During the service, a Cohen of Sephardic descent from North Africa was reading from the Hebrew bible. According to Jewish tradition, all Cohanim (plural of “Cohan” or “Cohen”) are direct descendants of Aaron, the brother of Moses, and serve important priestly functions within the Jewish religion. The line of the Cohanim is patrilineal, allegedly being passed from father to son without interruption from Aaron, for 3,300 years, or more than 100 generations. Dr. Skorecki wondered if this claim could actually be tested. Could he find scientific evidence to support the oral tradition of an ancient priestly lineage? Did he and the Sephardic Cohen possess a set of common genetic markers indicating they shared a common ancestor?

Dr. Skorecki, a nephrologist already involved in molecular genetic research, contacted Dr. Michael Hammer of the University of Arizona, a pioneer in Y chromosome research, and the Cohanim DNA study was born. Their findings clearly indicated that the Cohanim did indeed share a common ancestor. They discovered that a particular haplotype was found in 97 out of the 106 participants tested. This haplotype has come to be known as the “Cohen Modal Haplotype” or “CMH”. According to the study, calculations for dating the CMH yielded a time frame of 106 generations from the ancestral founder of the lineage – approximately 3,300 years ago (Thomas et al. 1998).

Not only did the genetic researchers corroborate the oral history of an ancient Jewish priestly caste, but they also confirmed the genetic link between both Sephardic and Ashkenazi populations, indicating that before the two populations separated, those who shared the CMH also shared common Israelite ancestry. Today, the CMH is considered not only the standard genetic signature of the priestly Cohanim, but also the yardstick by which all Jewish DNA is compared for determination of Israelite genetic ancestry. Thus, if a haplogroup is not shared by both Sephardim and Ashkenazim at a similar frequency, then it is generally not considered to be of Israelite origin.

Skorecki and Hammer reported that the CMH occurred within Y chromosome haplogroup J (Skorecki et al. 1997). We now know significantly more about haplogroup J than when these studies were originally published. Haplogroup J consists of an ancestral form (J*) and two subgroups – J1 and J2. Although you can have the CMH in either J1 or J2, it is the genetic signature in J1 that is considered the Jewish priestly signature.

What is not widely reported is that only 48% of Ashkenazi Cohanim and 58% of Sephardic Cohanim have the J1 Cohen Modal Haplotype (Skorecki et al. 1997). So nearly half of the Ashkenazi Cohanim results are in haplogroups other than J1. Overall, J1 constitutes 14.6% of the Ashkenazim results and 11.9% of the Sephardic results (Semino et al. 2004). Nor is Cohanim status dependent on a finding of haplogroup J1.

Additionally, many other haplogroups among the Ashkenazim, and among the Cohanim in particular, appear to be of Israelite/Middle Eastern origin. According to Behar (2003), the Cohanim possess an unusually high frequency of haplogroup J in general, reported to comprise nearly 87% of the total Cohanim results. Among the Sephardim, the frequency of 75% is also notably high (Behar 2003). Both groups have dramatically lower percentages of other haplogroups, including haplogroup E. Given the high frequency of haplogroup J among Ashkenazi Cohanim, it appears that J2 may be only slightly less common than J1, perhaps indicating multiple J lineages among the priestly Cohanim dating back to the ancient Israelite kingdom.

However, J1 is the only haplogroup that researchers consider “Semitic” in origin because it is restricted almost completely to Middle Eastern populations, with a very low frequency in Italy and Greece as well (Semino et al. 2004). The group’s origins are thought to be in the southern Levant. Its presence among contemporary Sephardic and Ashkenazi populations indicates the preservation of Israelite Semitic ancestry, despite their long settlement in Europe and North Africa. Further, the CMH is considered the putative ancestral haplotype of haplogroup J1 (Di Giacomo et al. 2004).

Table 1 compares the Jewish J1 CMH to the J1 modal haplotypes of other Middle Eastern populations:

Table 1

Modal Haplotypes* in J1 Populations

J1 GROUPS	D Y S 0 1 9	D Y S 3 8 8	D Y S 3 9 0	D Y S 3 9 1	D Y S 3 9 2	D Y S 3 9 3
CMH	14	16	23	10	11	12
Bedouin	14	15	23	10	11	13
Palestinian	14	17	22	11	11	13

*6-Locus Haplotype.

Researchers believe that marker 388=17 is linked with the later expansion of Arabian tribes in the southern Levant and northern Africa (Di Giacomo et al. 2004). There were two migrations of J1, the first occurring in the Neolithic period, spreading J1 to Ethiopia and Europe (Semino et al. 2004). A second wave of J1 occurred in the 7^th century, spread by Arab expansion from the southern Levant into North Africa. This secondary migration is also distinguished by a mutational event at marker YCAII—YCAIIa=22 and YCAIIb=22 (Semino et al. 2004).

The Cohanim study was widely misinterpreted by the public as indicating that all Jews were in haplogroup J and had the CMH. Furthermore, many non-Jews in haplogroup J mistakenly believed that they must have some Jewish ancestry hidden in their past to explain their DNA results. As it turned out, most non-Jews were in subgroup J2 rather than J1 (Semino et al. 2004). Interestingly, Jews were later found to have as much J2 ancestry as J1.

The misinterpretation of the Cohanim results was damaging in some ways to the wider understanding of Jewish genetic ancestry. For example, one widely published media quote went like this: “This genetic research has clearly refuted the once-current libel that Ashkenazi Jews are not related to the ancient Hebrews, but are descendants of the Kuzar (sic) tribe – a pre-10^th century Turko-Asian empire which reportedly converted en masse to Judaism.” Further, it was claimed that “[r]esearchers compared the DNA signature of the Ashkenazi Jews against those of Turkish-derived people, and found no correspondence” (Kleinman 1999).

However, it would soon become very clear that Jewish DNA was much more complicated than was presented by the media in their reporting of the Cohanim data. And Jewish Khazarian ancestry would come to the public’s attention yet again when another DNA study was conducted, this time on the Jewish priestly group known as the Levites.

The Khazars: A Jewish Kingdom in Europe

Author Arthur Koestler (1976) is generally credited for bringing the unique history of the Khazars to the attention of the public. The decades that have past since the publication of his book have not dampened its highly controversial nature.

The country of the Khazars lay in the area between the Black and Caspian Seas, between the Caucasus Mountains and the Volga River. There, between the ever-invading Muslim Arabs and the Christian Byzantine Empire, a peculiar thing occurred – a Jewish empire arose. In 740 CE, the Khazarian King, his court and military ruling class all embraced the Jewish faith. This large scale official conversion of an ethnically non-Jewish people is well attested to in Arab, Byzantine, Russian and Hebrew sources (Koestler 1976, pp.13-15).

The rationale behind such conversion continues to both puzzle and fascinate historians – why would a people, despite political pressure from two great powers, chose a religion which had no support from any political power, but was rather persecuted by all? Whatever the reason, the Jewish Khazars continued to rule their kingdom until the 12^th-13^th century, when their empire finally dissolved. The fate of the Khazars after the fall of their empire remains a subject of great controversy among researchers.

The Khazars are often described as “a people of Turkish stock,” although such description is misleading (Koestler 1976, p. 13). Although the Khazars spoke a Turkish dialect believed to be related to that spoken today by the peoples of the Chuvash Soviet Republic, their ethnic origins remains a matter of debate. Many of the Eurasian tribes driven westward by the Chinese, including the Huns, were labeled under the generic term of “Turk.” The origin of the word “Khazar” most likely derives from the Turkish root “gaz,” meaning “to wander” or simply “nomad.” (Koestler 1976, p. 21).

Given that the Khazarian kingdom arose in the area of today’s Ukraine, it is likely that there was a significant amount of indigenous Eastern European ancestry among this group. And, in fact, the various descriptions of the Khazars provided by ancient writers attest to the probable heterogeneous ethnic mixture in this group.

According to an 11^th century Arab chronicler Ibn-al-Balkhi, the Khazars are

. . . to the north of the inhabited earth towards the 7^th clime, having over their heads the constellation of the Plough. Their land is cold and wet. Accordingly their complexions are white, their eyes blue, their hair flowing and predominately reddish, their bodies large and their natures cold. Their general aspect is wild” (Koestler 1976, p. 19). An Armenian writer described them as having “insolent, broad, lashless faces and long falling hair, like women. (Koestler 1976, p. 20).

A slightly more flattering picture is provided by Arab geographer Istakhri:

The Khazars do not resemble the Turks. They are black-haired, and are of two kinds, one called the Kara-Khazars [Black Khazars] who are swarthy verging on deep black as if they were kind of Indian, and a white kind [Ak-Khazars], who are strikingly handsome. (Koestler 1976, p. 20)

However, Koestler (1976, p. 22) cautions the reader not to place too much weight on this description, since it was customary among Turkish peoples to refer to the ruling classes as “white” and the lower clans as “black.”

It is clear that the Khazars were closely connected to the Huns, who themselves are an ethnic mystery. The Byzantine rhetorician Priscus, who was part of an embassy to Attila the Hun’s court in 448 CE, reported that a people known as the “Akatzirs” or “White Khazars” were subjects of the Huns. According to Koestler (1976, p. 23), “Priscus’s chronicle confirms that the Khazars appeared on the European scene about the middle of the fifth century as a people under Hunnish sovereignty, and may be regarded, together with the Magyars and other tribes, as a later offspring of Attila’s horde.” After the collapse of the Hunnish Empire following Attila’s death, the confederation of tribes known as the Khazars eventually gained supremacy in the southern half of Eastern Europe, retaining control of this region for nearly four centuries.

What became a matter of dispute among historians was the fate of the Jewish Khazars after the destruction of their empire in the 12^th-13^th centuries. Koestler argued that remnants of the Khazar tribes migrated into regions of Eastern Europe where the greatest concentrations of Jews were found, eventually merging with those pre-existing communities. In fact, Koestler’s controversial argument was that the Khazars emigrated in substantial enough numbers to have had a significant genetic impact on contemporary Jewish ancestry.

With the advent of DNA studies, the question of whether contemporary Jews could trace any part of their ancestry back to the Khazars became a tantalizing mystery to try to solve. While the Cohanim DNA writers attempted to close the book on this question, evidence from another important genetic study, that of the Jewish Levite priests, made it apparent that the Khazarian debate was far from over.

The Levites: The DNA of the Jewish Khazarian Priests

The other Jewish priestly caste is known as the “Levites.” Like the Cohanim, Levites are recorded in the Hebrew Bible as direct descendants of Aaron, Israel’s first High Priest. In fact, the Cohanim are actually a special subsection of the Levites (Telushkin 1997, p. 125).

In the second study published on the Cohanim, researchers reported that despite a priori expectations, Jews who identified themselves as Levites did not share a common set of markers with the Cohanim (Thomas et al. 1998). Unfortunately, the reporting that the Levites did not share a genetic signature from a common patrilineal ancestor with the Cohanim flew in the face of Jewish tradition. This led to some rather bizarre and disparaging explanations, like the following from Rabbi Yaakov Kleiman (1999) in Jewish Action:

It is interesting to note that the tribe of Levi has a history of lack of quantity…After the Babylonian exile, the Levi’im (plural) failed to return en masse to Jerusalem, though urged by Ezra the Scribe to do so (They were therefore fined by losing their exclusive rights to maser.). Though statistically, the Levi’im should be more numerous than Cohanim, in synagogues today it is not unusual to have a minyan with a surplus of Cohanim, yet not one Levi.

In point of fact, the Levites were shown to have a common set of genetic markers – just not the CMH. These markers were not even part of the same J1 haplogroup as found in the Cohanim. The majority of Levites shared a common haplotype, indicating a shared common ancestor among them, but this haplotype occurred within haplogroup R1a and, more specifically, within subgroup R1a1. Furthermore, this haplogroup was found only in the Ashkenazi Levites; it was not shared with the Sephardic Levite population in the same fashion as the CMH. Given the fact that the Ashkenazi Levites did not share R1a with their Sephardic counterparts, it appeared that this haplogroup had entered the Jewish population sometime during the Diaspora.

In one of the first studies to closely examine the high levels of R1a among Levites, researchers found that R1al formed a “tight cluster” within the Ashkenazi Levites (Behar et al. 2003). This suggested to the researchers a very recent origin of this group from a single common ancestor (Behar et al. 2003).

In a subsequent Levite study, the modal haplotype reported for Ashkenazi R1a1, known as “H6,” was reported to occur twice as often as the second most common R1a1 haplotype among Ashkenazim, known as “H10” (Nebel et al. 2005). Out of a sample of 55 individuals, 25 had haplotype “H6” and 12 had haplotype “H10” (Nebel et al. 2005, Supplementary Material).

Table 2

Haplotypes* for Ashkenazi R-M17

HAPLOTYPE

H10

*6-Locus Haplotype

Behar believed that among Ashkenazi Jews, R1a1 was essentially restricted to Levites. However, we know from subsequent research that R1a1 comprises nearly 12% of Ashkenazi results, while the Levites only make up about 4-5 % of the Jewish people (Nebel et al. 2005). Thus, these results extend well beyond the Levite priestly class to approximately 5-8% of the Cohanim and Israelites (the non-priestly Jewish population) as well.

Haplogroup R1a1 is relatively rare within Middle Eastern populations, but very common among Eastern European and Scandinavian populations (Behar et al. 2003). It is found at a frequency of 7% in some Near Eastern groups (Behar et al. 2004b). However, given that Sephardic groups did not share R1a1 frequencies with the Ashkenazim, it was apparent that Jewish R1a1 was probably not of ancient Israelite origin.

Confirmation of the high frequency of Haplogroup R1a1 among Ashkenazim as compared to other Jewish and non-Jewish Middle Eastern populations was found in a genetic study on Samaritan and Israeli groups (Shen et al. 2004). Although population samples were small, consisting of twenty participants from Ashkenazi Jewish groups, all were Eastern Ashkenazim of Polish ancestry. Ashkenazi results were compared to other Jewish groups from Iraq, Libya, Morocco, Ethiopia and Yemen, as well as to non-Jewish Samaritan, Druze and Palestinian populations. Shen found that haplogroup R was found in 10-30% of all the groups, with the exception of Palestinians and Ethiopian Jews, though the majority belonged to R1b and R*. In contrast, the Ashkenazim had the highest percentage of haplogroup R (30%), with two-thirds of those results found in haplogroup R1a (Shen et al. 2004).

As for when R1a1 first entered the Jewish community, Behar (2003) estimated a mean TMRCA (time to the most recent common ancestor) of 663 years before the present using the Simple Stepwise Mutation Model and a mean time of 1,000 years before present under the Linear Length-Dependent Stepwise Mutational Model. This calculation was striking because it fit precisely within the time period that Koestler believed the mass migration and absorption of the Khazars by the larger Eastern European Jewish communities occurred.

R1a1 is found in very high frequencies not only in the area of Eastern Europe where the Khazarian kingdom is reported to have existed, but also in many Central Asian populations as well, where some of the Khazarian population may have originated (Nebel et al. 2005). Furthermore, the most common Ashkenazi haplotype, H6, is identical to the most common haplotype found among European R1a1 (YHRD 2003). Ashkenazi H10 is identical to the fifth most common European R1a1 haplotype.[1]

Behar (2003) noted that Ashkenazi R1a1 haplotypes clustered closely with those seen in Sorbian and Belarusian groups in Eastern Europe, yet the haplotypes were dissimilar enough to convince him that these groups were not the original source population for Ashkenazi R1a1. While the Ashkenazi H6 haplotype is also one of the most common haplotypes among the Sorbian and Belarusian populations, the modal haplotypes found among these two Eastern European groups do not appear among Ashkenazim (Behar, 2003). However, it is possible that genetic drift could have led to the loss of other Jewish R1a1 lineages (Behar, 2003).

Nebel (2005) emphasized that the R1a1 haplogroup must have entered the Jewish gene pool from outside sources because the ancestral haplotype (H6) is almost completely absent in Sephardic Jews, Kurdish Jews and Palestinian population samples. He suggested that R1a1 in Ashkenazim “may represent vestiges of the mysterious Khazars.” However, he also argued for a single founder event early on in the Jewish Diaspora, proposing that the TMRCA for R1a1 among Ashkenazi was approximately 62.7 generations ago, or 1567 years ago.

However, the proposal that R1a1 originated with a single founder event early in the Diaspora has become increasingly unlikely as research on Jewish DNA progresses. Since R1a1 is spread fairly evenly in haplotype distribution and frequency throughout the Ashkenazi populations from various countries (Germany, Lithuania, Czechoslovakia, Hungary, Romania, Poland, Russia and the Ukraine), then the founders must have entered the community either before it expanded and spread to Eastern Europe, or merged separately into both eastern and western Ashkenazi groups. However, Nebel (2005) is forced to assert an extremely early TMRCA due to his belief that R1a1 must have originated with a single founder or very small group of founders. In order for R1a1 to reach its high frequency (12%) among the Ashkenazim from a single founder, a very early date must be proposed for the introgression of this haplogroup. Under this scenario, R1a1 entered the Jewish community when it was extremely small and in its formative stage. Gene flow from a single R1a founder at this early stage would likely have a huge impact on the expanding Ashkenazi population.

However, it appears that the most recently revised mutational dating techniques lend support to Behar’s (2003) later date when applied to Jewish R1a1 haplotypes. If we assume that R1a1 entered the Jewish community around 1300 CE, then there would need to be enough founders to leave a 12% genetic impact on the population. Given that the Ashkenazi population at that time is estimated to be approximately 25,000 persons, it would be nearly impossible for a single founder to make such a significant genetic impact (Behar et al. 2004b). Adopting this conservative estimate of 25,000 persons, approximately two to three thousand R1a1 males probably entered the Ashkenazi community between the 12th-13^th centurie