DNA Research #DNA RE: FT DNA - volume and threshold of matches #dna

David Ellis

Steve Stein writes:

Is there any way to either let FTDNA know that I am not interested
in lower level matches, or to have the match display default to a filter?

This is a known issue with FTDNA. Unlike the other DNA services, which by
default exclude segments less than 7 cM >from their totals, FTDNA appears to
have no option to adjust the totals downward to mitigate the effects of
Ashkenazi Jewish endogamy. One thing you can do is view promising matches
in the Chromosome Browser, which does allow you to choose a minimum segment
size of 1, 5, 7 or 10 cM to display.

I have been using a modified version of Lara Diamond's criterion for looking
further into DNA matches. She recommends a total of at least 100 cM with
longest segment at least 20 cM. I add one more criterion, a second segment
at least 10 cM. This excludes matches with one long segment and only
background noise, which I have found to be tantalizingly out of my
genealogical reach. No rule of thumb is foolproof; you can't avoid false
positives and false negatives.

The most important piece of guidance is to get as solid a paper trail as you
can before assessing your DNA matches. When reviewing a promising match,
look for the holes in your paper trail. My most promising unidentified
match seems to be a third cousin once removed. I've found siblings of all
eight of my great-grandparents and nine of my sixteen great-greats; this
match appears to be a great-grandchild of a sibling of one of seven of my
great-greats that I haven't identified. Quite an interesting brick wall.

Let me close with a success story. After eight years of fruitlessly
pursuing hundreds of promising DNA matches and failing to connect our family
trees, Ancestry DNA connected me with a previously unknown third cousin from
a family branch that I thought had all died in the Holocaust. I never found
her grandfather's birth record in Galicia, but I did find births of three
sisters in the JRI-Poland database, with subsequent listings in the US
Holocaust Memorial Museum's list of persecuted people. Her grandfather
survived a concentration camp and came to the US, believing he was the only
survivor. He didn't know he had an aunt who had left Galicia for the US in
1904, nine years before his birth. He was living in New York, less than a
mile away >from his first cousin, my grandmother, and the two of them never
knew of the existence of each other. Fifty years later, his granddaughter
found me because she noticed her great-grandfather and her grandfather's
sisters in my family tree.

David J Ellis
Natick, MA 01760

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