Jewish Endogamy, or "In every generation they rise up against Us"

Hebrew commandments on door of Duomo in Florence, Italy

Since I wrote about the Shared cM Project, I learned that endogamous populations, or people who have married within the same ethnic or cultural group, have higher amounts of shared cM when you compare their DNA. My mother's entire family is Ashkenazi Jewish, a group closely studied by geneticists and genetic genealogists that perfectly illustrates this idea.

All Ashkenazi Jews descend from a small "bottleneck population" of maybe 350 people who lived between 1200-1400. There is little evidence of what exactly happened roughly 30 generations ago, but the scientific term "bottleneck" is a euphemism for what my ancestors had to endure: killings, persecution, and subpar living conditions. The medieval persecution of European Jews includes massive events like massacres during the Crusades, the expulsion from England in 1290, pogroms following the Black Death's arrival in 1347, pogroms throughout Iberia in 1391, the expulsion from France in 1394, and the final expulsions from Spain in 1492 and Portugal in 1497.

To repurpose the popular phrase: "Nevertheless, we persisted!" Year after year at Passover, we Jews recite from the Haggadah:

In each and every generation they rise up against us to destroy us. And The Holy One, blessed be He, rescues us from their hands.

Genealogists like Lara Diamond have carefully explained how DNA matches are different for Ashkenazi Jews and their descendants. We have multiple lines of shared ancestry the further back you go, and these small bits of common DNA add up. Websites like Ancestry.com may infer that we are closer relations than we actually are, given how much DNA we share. Larger amounts of shared cM are even found among people of partial Ashkenazi Jewish descent, like myself.

My mother's first cousin did an AncestryDNA test, and I wonder if the amount of DNA we share is similary increased. I also wonder how matches on my grandfather Rueda's side might be impacted, as the settlers of the remote area of Santander Department, Colombia largely married cousins over many generations.

Questions? Comments? Please email me at ruedafingerhut [at] gmail.com