Measuring tree completeness
One of the single most important factors in determining the likelihood that somebody we match as a DNA cousin matches us in a particular way is tree completeness.
That’s the degree to which we — and our match — have identified all of the ancestral lines from which our shared DNA might have come.
Or, in the words of Blaine T. Bettinger, The Genetic Genealogist, “how complete are the trees you are comparing? In other words, how confident are you that the DNA couldn’t have come from other shared ancestors?”1
Or, to say it another way, how many of our second or third or fourth great grandparents have we really identified so that we can see whether the DNA we share with a cousin would likely have come from this set of known and identified fourth great grandparents and not from that set of unknown and unidentified fourth great grandparents?
As Blaine has explained, “Consideration of Tree Completeness (how much of two trees you’re actually comparing when you’re looking for a common ancestor) is essential when utilizing DNA evidence. … Use caution when making conclusions based on trees with big holes! There are ways to deal with this (like location, etc.), but we can’t deal with the issue if we don’t recognize that it exists.”2
Now all of us — The Legal Genealogist included — have holes in our family trees. Branches where we know we have work to do to fill in the leaves we need.
But it hasn’t always been easy to see those holes when we’ve needed to. In other words, it’s been hard to know when we need to work around the holes with location and other clues.
When DNA Painter has made it as easy as filling in some blanks, or uploading a GEDCOM file.[3. See
Which it then paints into a gorgeous — and telling — chart:
You can, if you’d like, hover over any particular ancestor and see the line of descent in that chart:
Or, if you prefer, you can see in a pedigree-tree format. Here’s just a portion of my paternal side in that format:
It will also tell you, in no uncertain terms, where you’re falling short as a matter of basic mathematics:
Sigh… I have a lot of work to do… including some just-plain data entry stuff…
Now… one small but annoying problem I saw was the program’s inability to handle some foreign language characters in a GEDCOM upload. My father’s side of my tree is filled, for example, with umlauts — those double dots over a vowel in the German language that change the way it’s pronounced. Those get rendered in a GEDCOM upload as a question mark. It handles these just fine when you type them or copy-and-paste them online.
Those with a free DNA Painter account can have one tree for free to go along with their one free DNA Painter profile once the tool is publicly released to all. Those of us who think DNA Painter is about the next best thing to sliced bread and subscribed the minute it became a subscription service can have as many as 50 trees to go along with our 50 profiles — it’s available to subscribers now. And breaking maternal and paternal trees into two for each of the profiles we manage is a really nice way of organizing these.
So shelling out the $30 for six months or $55 for a year is a small price to pay for the utility of being able to see all of the issues with our tree completeness for ourselves and for the profiles we manage — not to mention supporting a terrific tool and its future development.
Ensuring that we’re using DNA evidence effectively means knowing when our job is filling in the blanks — either with more research to identify specific ancestors or with other clues like location.
This tool helps us see just when that’s critical.
Well done, DNA Painter.
Cite/link to this post: Judy G. Russell, “Filling in the blanks,” The Legal Genealogist (https://www.legalgenealogist.com/blog : posted 28 July 2019).
- Blaine T. Bettinger, “The DNA Era of Genealogy,” The Genetic Genealogist, posted 17 Dec 2016 (https://thegeneticgenealogist.com/ : accessed 28 July 2019). ↩
- Blaine T. Bettinger, Facebook status entry, Genetic Genealogy Tips & Techniques group, posted 12 Feb 2018, Facebook.com (https://www.facebook.com/groups/geneticgenealogytipsandtechniques/ : accessed 28 July 2019). ↩