Yes, The Legal Genealogist is aware of the upcoming change at AncestryDNA to eliminate the smallest of our small-segment matches.
Yes, I’m aware this will mean potentially thousands of matches not showing up any more.
And I have some advice about this:
Let me repeat that.
So… the announcement from AncestryDNA explains that “Our updated matching algorithm will increase the likelihood you are actually related to your very distant matches. As a result, you’ll no longer see matches (or be matched to people) that share less than 8 cM with you – unless you have added a note about them, added them to a custom group or have messaged them. These changes to the matching algorithm will reduce the total number of DNA matches you have and the number of new matches you will receive. It may also affect the number of ThruLines you may see.”1
And the genetic genealogy community went into a tizzy bemoaning all the lost data and lost research opportunities and how could Ancestry do this and they’re only out for the money.
Let me say it again.
First off, you can save any that you for some reason think are really essential.
Second, few if any of these are really essential.
Let’s start with the “you can save any” part. If you really think you need this information, pop over to Roberta Estes’ DNAeXplained blog and follow her excellent guidance in the post “Ancestry to Remove DNA Matches Soon – Preservation Strategies with Detailed Instructions.”2
In short, these get saved if you’ve ever added a note about one of these matches, added them to a group (including adding a star), or sent them a message. And you can do that now if for some reason you think they’re really essential..
But let’s consider the second part: few if any of these are really essential.
After all, if in all the time you’ve had these matches, you haven’t added a note, added them to a group or sent them a message, just how important are these matches?
The truth is, for the vast majority of researchers — the very serious professional geneticists excepted — they’re not important at all.
First, a huge percentage of these small segment matches are false positives. Those that aren’t tend to be so far back in time that the average researcher will never be able to discover which of our many many ancestors might have been the source of that segment. The best discussion of this aspect of this change is in Blaine Bettinger’s post, “Losing Distant Matches at AncestryDNA.”3
Second, even if the match is a real one — not a false positive — the odds are it’s to someone who’s going to end up being about a sixth cousin.4
So… my sixth cousins and I share a set of fifth great grandparents. We all have 128 fifth great grandparents. So… how many have we actually identified so we might possibly begin to figure out how a match matches us?
For me, looking at my tree completeness report at DNAPainter.com, it’s pretty depressing:
It’s 25 out of those 128 people. Just 20%. At the sixth great grandparent level, I’ve only identified 18 of 256 — just seven percent.
Some of that is because of a brick wall at one of my maternal second great grandfathers. Some of it is because of an illegitimacy in 1855 Germany. Neither of those is likely to be solved with tiny DNA matches of questionable origin who may not be real matches at all.
In part, it’s because there are just too many people in my match list to begin to manage or cope with. I checked this morning to see just about many matches I have at the level of the smallest segment Ancestry is going to eliminate — the 6cM level.5
It took me 20 minutes to scroll to the bottom of my list of 6cM matches. Turns out I have 13,989. Of those, 3,402 have no trees at all. Another 3,441 don’t have their DNA linked to a tree.
I can’t work with 13,989 matches who may not be real matches at all. I can’t begin to work with the 6,000+ who don’t even have a tree linked to their DNA.
Now I can hear the splutters already. But what about those who do have a tree and do have an ancestor in their tree in common to mine?
Of 13,989 matches at the 6cM level, only 122 have someone in their tree who’s also in my tree.
How many of these have I messaged because of the DNA match? None.
How many of these have ever messaged me? None.
And — most important — of all those who share a common ancestor with me, how many could I have found simply by following a tree hint? All of them.
So… what does it add to my proof that a tree hint comes from someone who matches my DNA at the 6cM level? Just about nothing until and unless I can show that the DNA couldn’t have come from some other proposed common ancestor. And until my tree completeness is a whole lot better than 7-20% — and unless my match’s tree completeness is a whole lot better as well — I can’t show that.
And let’s look at another metric here. Just as we know that there are an awful lot of false positives at the 6-7cM level, where we’re going to lose these reported matches, we know that the vast majority of matches above 20cM are for real. And it’s at that 20cM level that Ancestry reports shared matches (you only see the shared matches who might be fourth cousins or closer, and Ancestry defines that at the 20cM level).
So I took a look at the number of matches I have at AncestryDNA with whom I share 20cM or more of DNA. As of today, there are 3,072 of them. How long is it going to take me to seriously work with 3,000+ matches — any one of whom offers a much much better chance of actually discovering something genealogically useful than any of those 6cM matches?
Just looking at those with whom I share the smallest amount in that group — those with whom I share exactly 20cM — I have 530 matches. Take out the ones with no tree at all and I have 387 to work with.
How long is it going to take me to seriously work with 387 potential matches?
I have enough to work with. I’m literally drowning in data I can’t even get to. This is the case for the vast majority of us — with just maybe the very serious professional geneticist-researchers excepted.
Losing these very small probably-false matches is No Big Deal.
This is why our response to this Ancestry announcement should be very simple.
Cite/link to this post: Judy G. Russell, “Chilling with AncestryDNA,” The Legal Genealogist (https://www.legalgenealogist.com/blog : posted 19 July 2020).
- “Updates coming soon to DNA matches,” announcement header on DNA match lists, Ancestry.com (https://www.ancestry.com : accessed 19 July 2020). ↩
- Roberta Estes, “Ancestry to Remove DNA Matches Soon – Preservation Strategies with Detailed Instructions,” DNAeXplained, posted 16 July 2020 (https://dna-explained.com/ : accessed 19 July 2020). ↩
- Blaine T. Bettinger, “Losing Distant Matches at AncestryDNA,” The Genetic Genealogist, posted 17 July 2020 (https://thegeneticgenealogist.com/ : accessed 19 July 2020). ↩
- You can check this. Head over to DNAPainter.com, click on Tools, choose The Shared cM Project 4.0 tool v4, and enter 6 and then 7 in the filter box. You’ll see that the odds are really high that you’re looking at a sixth or more distant cousin. ↩
- cM remember is the abbreviation for centimorgan, a unit of measuring how closely two DNA matches are related. The bigger the number, the more closely related. See ISOGG Wiki (https://www.isogg.org/wiki), “centiMorgan,” rev. 2 Jan 2019. ↩