Genealogy / I have Jewish DNA, but only know of Polish ancestry . [120]

As some of you know, significant numbers of Jews converted to Roman Catholicism in the 18th and 19th centuries and assimilated into Polish society and married ethnic Poles. The following are sources I found useful for the historical documentation:

Adam Kaźmierczyk's article "Converted Jews in Kraków, 1650-1763" in Gal-Ed: On the History and Culture of Polish Jewry vol. 21 (2007) on pages 17-52.

Paweł Maciejko's 2011 book The Mixed Multitude: Jacob Frank and the Frankist Movement, 1755-1816.

Magda Teter's article "Jewish Conversions to Catholicism in the Polish-Lithuanian Commonwealth of the Seventeenth and Eighteenth Centuries" in Jewish History vol. 17, no. 3 (2003) on pages 257-283.

As for genetic evidence, in addition to 1% or 2% in Ashkenazi autosomal DNA components that some Catholic Poles receive when they test with companies like Family Tree DNA, in my book The Maternal Genetic Lineages of Ashkenazic Jews, I identified the following mtDNA haplogroups in Poles as being of Ashkenazic origin: H3p, K1a1b1a, K1a9, K2a2a1, and L2a1l2a.

Genealogy / How common was Polish-Jewish intermarriage? [21]

As I wrote in my book The Maternal Genetic Lineages of Ashkenazic Jews, the mitochondrial haplogroups H11a2a2 and W3a1a1 are shared between Ashkenazic Jews and Polish Catholics so I think it is likely that Ashkenazim inherited these from Polish women.

According to pages 5-6 of the study "Genome-wide data from medieval German Jews show that the Ashkenazi founder event pre-dated the 14th century", the majority of the Slavic DNA in Ashkenazim was incorporated by the 14th century and intermarriages in later centuries only affected the Ashkenazic genome to the extent of about 2 to 4 percent at most. Some of the Jews living in Erfurt in the 14th century already had a huge proportion of Slavic DNA, making up as much as about 40 percent of their individual genomes.

But some of the earlier Slavic elements appear to have been Czech rather than Polish. Their study's admixture models in Figure 3 only use Russians as a proxy population to represent the concept of what they call Eastern European ancestry. Russian ancestry doesn't exist in Jews.

History / Khazar migrations to Eastern Poland, Belarus, and Ukraine [106]

Q1b and R1a1 aren't the Khazar lineages in Ashkenazic Jews.

N9a3 is one that actually seems to be Khazar because the Ashkenazic branch is phylogenetically descended from the kind (N9a3a1b) that Turkic-speaking Bashkirs have, as I wrote on pages 85-86 in my book The Maternal Genetic Lineages of Ashkenazic Jews. Some Mongolic-speaking Daur people from northeastern China also belong to that Bashkir variety (GenBank sample ON127764 from the supplementary data set to "Genetic Diversity Analysis of the Chinese Daur Ethnic Group in Heilongjiang Province by Complete Mitochondrial Genome Sequencing"). It won't be surprising if a N9a3 carrier eventually turns up in a medieval Khazar gravesite.

There were four sources for red hair in Ashkenazim, from four different gene variants. The red hair allele for rs201326893 existed among Tsarfati Jews in Norwich, England in the 12th century as well as Rhineland-descended Jews in Erfurt, Germany in the 14th century so that variant wasn't brought to Jews by the Khazars. Red hair in Jews probably came from northwestern Europe and the Levant.

The surname Kaczor is Polish for a male duck. It has no connection to the Khazar people.