Sunday, November 3, 2019

Genetic Journey Back to Jacob

When Leah saw that she had left bearing,
she took Zilpah her maid, and gave her Jacob to wife.
And the sons of Zilpah, Leah's handmaid; Gad, and Asher:
these are the sons of Jacob, which were born to him in Padanaram.
Genesis 30:9/35:26


"It is clear that modern-day Judaism carries a core set of ancient lineages tracing back to the Middle East, plus a large fraction of newer genes brought in by more recent mixing. Is this core set of genes enough to conclude they indeed trace back to biblical times? Indeed so.


Ancient Jewish communities (most of which are still in existence) were founded in Africa (Algeria, Libya, Morocco, Tunisia, Ethiopia, SE Africa), Asia (the Levant, Asia Minor, Yemen, Baghdad, Iran, India, Burma), Europe (Spain, Italy, Central Europe), and possibly other places.
Some of these are more ancient (e.g. Yemen) than others (e.g. the Ashkenazi). Some were also founded by fewer people (e.g. Ethiopia). But all of them claim descent from the Jews of ancient Israel.
Some of these groups grew large, but others remained quite small,
causing significant levels of inbreeding over time. For example, the NW African colonies may have been settled along Phoenician trade routes. They managed to hold on during many centuries of conflict, but never managed to grow very large.
Thus, high rates of endogamy exist in those small pockets. They did receive an influx of Sephardic Jews after Ferdinand and Isabella expelled the Jews from Spain in 1492, but even today one can see evidence for the two different groups in the genomes of those people.

A direct paternal lineage from the patriarch Jacob is generally thought to define Jewishness.
Yet, early analyses with limited data concluded that more than one Y chromosome haplogroup exists among modern Jews.
Does this contradict the biblical narrative?
Actually, no.

When comparing the Y chromosome haplotypes found in Jewish and non-Jewish Middle Easterners, it is clear that they share a
common pool of sequences. The two together are distinct from non-Jewish groups in Europe, North Africa, and South Africa.
But the majority of non-Middle Eastern Jews also trace back to a Middle Eastern Y chromosome source, meaning all three groups (Middle Eastern Jews, Middle Eastern non-Jews, and European Jews) come from the same paternal stock. Hammer et al. (2000) conclude that a major portion of the diversity of Jewish Y chromosomes:
“… traces to a common Middle Eastern source population several thousand years ago. The implication is that this source population included a large number of distinct paternal and maternal lineages, reflecting genetic variation established in the Middle East at that time. In turn, this source diversity has been maintained within Jewish communities, despite numerous migrations during the Diaspora and long-term residence as isolated subpopulations in numerous geographic locations outside of the Middle East."
The multiplicity of distinct ancestral paternal lineages is due to the extensive mixing between Jews and non-Jews throughout their history plus the possibility of founder effects at different places in Jewish history.
In other words, it is possible that a ‘non-Jewish’ Y chromosome is found at higher-than-expected frequencies in specific Jewish populations today simply because it happened to be represented in one of the men who founded a small colony.

Among the Sephardic Jews, Y chromosomes from a diverse background can be found.
The majority come from haplogroup J (strongly associated with Middle Eastern peoples).
But others are from E1b1a and E1b1b (common in Africa and other places), R1a (up to 30% in Ashkenazi men), R1b (the most common lineage in Europe), Q (Asia), I (Europe, but rare), and G (mainly Western Asia).
The distribution of haplogroups found among the Spanish Sephardim was similar to a Jewish population in Turkey (sometimes included within the term ‘Sephardim’). This pattern also held for Jewish men from NE Portugal.
Nearly one third of the Y chromosomes were European (R1b, common in Eastern Europe), and over one half were ‘Middle Eastern’ (37% J and 16% T).

Further analysis of fully sequenced Y chromosomes indicates that the Ashkenazi individuals who carry the ‘European’ Y chromosomes of haplogroup R are not, in fact, related to the European branches in the Y chromosome family tree.
Even though this family might be common in Europe, the Jewish versions were found to branch off earlier and to be more closely related to Middle Eastern men who carry haplogroup R.
The clear implication is that this is an old, pre-Diaspora, possibly non-Jacob-descent Y chromosome family which is now found within the greater Jewish population. The majority of lines really do go back to a Middle Eastern setting.

A surprising percentage of men across Judaism who claim to belong to the Levitical priesthood (the Cohanim) share a common Y chromosome within a subgroup of haplogroup J.
This is despite the fact that they have been separated in some cases for approximately 2,500 years. This Y chromosome type has been named the Cohen Modal Haplotype (CMH), and men who carry it are more closely related to each other than they are to the other Jews in the communities in which they live. The CMH is rare in non-Levitical Jews, is found in 50% of Levites, and occurs in a much higher proportion of the Cohanim.
This leads us to a fascinating anecdote that combines history, genetics, and oral traditions.


The Lemba are a tribe from SE Africa with distinct customs and
language. Their oral tradition claims they are Jewish, descendants of men involved in long-distance trade. But they are Bantu speakers and are surrounded by Bantu-speaking peoples.
Analysis of their Y chromosomes revealed that more than half are of Middle Eastern origin.
Mitochondrial DNA, however, reveals no evidence of West Asian roots. This is consistent with the tradition that they were descended from Jewish traders coming down the coast from the north. But the history is further confirmed by the fact that the CMH is found within a certain subset of the Lemba.
 So not only did a group of Jewish men become marooned in southernmost Africa, and not only did they marry local women... but it appears that a descendent of Aaron was among them.

Among European Jews, Y chromosomes and mtDNA yield different patterns. More than one half of the mtDNA of Ashkenazi Jews can be traced back to three unrelated women from the same haplogroup K.
This represents a major population expansion and a significant founder event. These mitochondrial lines are almost non-existent in non-Jewish populations. But note that nearly half of the mitochondrial lineages do not belong to one of these three matriarchs.
Just under one half belong to haplogroup H, which is more associated with Europeans.

Due to high levels of inbreeding in their close-knit communities, Jewish groups carry a surprising number of otherwise rare, recessive genetic diseases.
For example, a major variant of the Creutzfeldt–Jakob disease has been associated with an origin in Spain and subsequent spreading caused by the 1492 expulsion of the Jews from Spain.
Bloom Syndrome is another rare, autosomal, recessive disorder most common in Ashkenazi Jews. But it is also found among Spanish-speaking individuals in Central America. Most likely, the individuals living in the Americas that are carriers had a Sephardic Jewish ancestor from Spain (confirmed by ancestry in several families).
Disease studies are fascinating in their own right, but since there are specific genetic anomalies associated with Jewish populations, this tells us that outbreeding with non-Jews was always limited.

Jews today absolutely fit both the biblical expectations and their
oral and written history since the completion of the Old Testament canon.
From the detailed history of the Jewish nation preserved in the Biblical narrative, it should be clear that they started as a mixed population, maintained a degree of mixing with their neighbors, and continue to mix with outsiders today.
However, as a Middle Eastern tribal community, they should have Middle Eastern genetic roots, and the evidence tells us they certainly do."
RobertCarter/CMI