Tag Archive | Ashkenazi

Endogamy and DNA

I really enjoyed the presentation Paul Woodbury of Legacy Tree Genealogists did about Endogamy last year at the SCGS Jamboree so I am delighted to present this guest post from him on that topic.

Personally I struggle with the endogamy in my mother’s family tree. My jewish grandad was an only child so there are not that many close cousins on his side. However due to endogamy my maternal aunts have hundreds of 2nd-3rd/4th cousin matches. No wonder I spend more time working with the easier Norwegian DNA from my Dad!

Endogamy and DNA By Paul Woodbury

Autosomal DNA testing is a valuable resource for genealogists seeking to overcome recent brick walls in their family history, particularly in instances where traditional historical research is limited or unavailing. At Legacy Tree Genealogists, we frequently use autosomal DNA test results to answer questions regarding adoption, unknown paternity, or ancestors who are difficult to trace. However, there are some factors that can complicate the use of autosomal DNA in tracing ancestors. One of those factors, which is what we will be discussing in the article, is Endogamy.

Endogamy is the custom of marrying only within the limits of a local community, clan, or tribe over the course of many generations. The reasons for this genetic isolation could be cultural or religious (as with Ashkenazi Jews and Low-German Mennonites) or geographic (as with island and tribal populations). Members of endogamous populations may descend from a limited pool of “founder” ancestors who represented the initial genetic makeup of their population. After many generations and hundreds of years of isolation from outside pedigrees, genetic profiles of population members can easily be distinguished from the DNA of outside populations. However, this can also cause pedigree collapse.

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A Jewish Adoptee Finds His Birth Family

This is the story of how I helped a Jewish adoptee find his birth family using DNA testing.

DNAadoption.com helps adoptees with DNA, including classes

First, here is a simplified explanation of the technique that an adoptee uses to find his birth parents using DNA:

  1. Do an autosomal test at each of the main companies. Once the results are in …
  2. Look through the family trees of 2nd, 3rd, and 4th cousin DNA matches for a common ancestral couple or two.
  3. Build private, unsearchable family trees down from each common couple to find someone in the right place at the right time.
  4. Get other people on those lines to test when their results will narrow it down some more.
  5. Males can also do a Y DNA test which might give them a surname if there are any close matches.

Obviously the more you know about the birth parents the easier this is. For more details on this technique see http://dnaadoption.com/index.php?page=methodology-for-autosomal-results or sign up for a class there.

Sadly these DNA search methods do not work well for adoptees from endogamous populations, such as Ashkenazi Jews (AJ) because everyone in that group shares as much DNA with each other as a 4th or 5th cousin. Even worse, most Jewish family trees stop at the grandparents or great grandparents because they do not continue across the ocean. Another problem is that even second cousins can have different Americanizations of their original surnames and let’s not forget that surnames are very recent in this population, about 1815 for most.

That is why there are so very few jewish adoptee successes, so I am celebrating this one with a blog post.

The DNA Search Story

I got an inquiry from, let’s call him Roger Stein, an adoptee curious about his birth parents who matched a cousin of mine at GEDmatch. GEDmatch is a site where you can compare tests done at different companies. His story follows, with all the names changed for privacy. If you do not want the DNA details just skip to the section titled “Contact.”
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Looking for Ashkenazi DNA Success Stories

A week from Sunday I am doing a presentation on the value of DNA testing for Jewish genealogists at a local group, the San Diego Jewish Genealogical Society. I have a nice talk planned, but it is missing a key ingredient, some success stories from my own research.

SDJGSsiteSmllThanks to some of my friends and fellow genetic genealogists I have a few good stories to share but if any of my readers have a success to contribute, please use my contact form to send it along!

While I have found over 30 new cousins on my Norwegian side with DNA so far, I have no confirmed cousins on my German and half Jewish side. It seems that genetic testing is not very popular in Germany. As my mother’s family came here in 1935, that is where most of my non-Jewish matches would be.

The problem with the Jewish side is that Ashkenazim share so much genetic material from past cousin marriages and population bottlenecks, that we tend to look like 4th and 5th cousins to each other in our DNA. Even though I am only 25% jewish (actually 28% at 23andme), I share some DNA with my Galician Ashkenazi husband with whom I doubt I have any common ancestors for many hundreds of years. I have blogged about these issues before, just click the tag Ashkenazi to read a few of those posts.

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Using Ashkenazi Jewish DNA to Find Family

Reading about this holocaust survivor’s discovery of missing family via DNA had me crying –
http://www.ynetnews.com/articles/0,7340,L-4589762,00.html – but it also got me thinking about how few jewish DNA success stories there are. Perhaps that is changing now that more people are testing.
A7734 on facebook
The screenshot at the left is from facebook page A7734 about Menachem’s search. It shows him and the genealogist who helped him, looking at the first picture of his parents he had ever seen.

Frankly, success stories with jewish DNA are rare.  I have none to report from my family. I emailed all my Ashkenazi researching friends to see if anyone had a good success story. Not very many are out there. If you have one, please send it along.

The endogamous nature of jewish DNA is part of the problem. Everyone looks like a close relative in the DNA matching. Another part of the problem is that so few Ashkenazim know their ancestors past their great-grandparents. Too many records were destroyed in WWII, among other problems researching.

In my experience, if an Ashkenazi Jewish (AJ) DNA match is not showing as a 2nd cousin or better it is unlikely that you will find the relationship. An experienced Israeli researcher told me to ignore anyone without at least one long segment match of 23 cM.

Below are a few tips from search angel Gaye Tannenbaum who frequently works with AJ DNA.

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Ashkenazi DNA: we are all descended from 350 people in medieval times

Most of my DNA explorations have centered around my Dad’s Norwegian DNA because so many Norwegians have tested and the populations of those ancestors are only mildly endogamous; so it is easy to find new cousins and fun to work with those results.

My grandfather and me 1955

My grandfather and me, summer 1955

My mother’s father was a German Jew. The number of DNA matches this gives me, my brother, and my two maternal aunts is astronomical. Frequently I will match someone from Eastern Europe for five or six large segments who cannot share an ancestor with us for the last 200-300 years and is even listed as a “distant cousin.”  If they were Norwegian, that amount of shared DNA would make them my 2nd cousin.

This has been so frustrating that I just about stopped working on my Jewish DNA. A fellow Jewish researcher told me to ignore matches who did not have at least one 23cM shared segment!

Today there were dozens of news articles about the European Jewish founder effect suggesting that all Ashkenazim are descended from about 350 people who lived in about 1300 A.D. or so. This, combined with a fair amount of endogamy, would explain the large amount of shared DNA among European Jews.
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