Last week I reported in this space about a problem I was having with GEDmatch. A match named Lauren had eleven matches with my families (using the one-to-many search) which her father George did not share, but were definitely not from her mother. When I dug deeper, I saw that George in fact matched all eleven when I used the one-to-one search.
I sent a link to that blog to the GEDmatch team and gave them the relevant kit numbers. Since then, I have been going back and forth with John Olson and I am pleased to report that we have a solution which John asked me to pass on to my readers.
How the basic one-to-many works
As we know, most of us endogamous folk have a few tens of thousands of matches on GEDmatch, but they only show the first 2000. (Early GEDmatch showed only 1500 matches, which proved inadequate.) "First" in this case means the lowest numbers in the "autosomal generations" column, which is the default sorting key. Other matches are available on the one-to-one searches, but when you manage a large number of kits, as I do, looking for those one-to-ones is not practical.
Most of my kits are given a name beginning with "*0Pikh..." so they will all sort together, near the top and I had always understood that when I sorted on the name column, they would show the first 2000 names from the entire match list. It turns out that this is not the case. The first 2000 matches are fixed and any sorting works only within that set of matches.
In this specific case, George's first 2000 matches go up to 3.9 generations while Lauren's go up to 4.5 generations.
Here are the last four matches of each of them:
George's matches with the eleven "missing" kits are all further than the last of the 3.9 generations that are displayed.
This may be a problem peculiar to endogamous populations where the number of matches is huge. Perhaps non-endogamous populations will have in their first 2000, matches that go to 5.0 generations or more.
And George may have more matches under 4.0 than most endogamous kits. But I see that I also go up to 3.9 generations and my two first cousins (not siblings) with one Jewish parent, both go to 4.4 generations. Frankly, 3.9 generations is not enough, nor is 4.4, so we need a way to enlarge the match list.
The Tier1 one-to-many gives you a choice among seven match limits, from a low of 500 up to 100,000. Both George and I have bit more than 40,000. My two first cousins with one non-Jewish parent have about 29,000 and 33,500 total matches. And it covers all the matches, with the same sorting capacity that I have gotten used to.
The 100,000 match limit search took me less than a minute, so it's not terribly burdensome.
"ONE-TO-MANY" IS DEAD. LONG LIVE "ONE-TO-MANY!"