Peter,
We are talking apples and oranges, and this has always been the disagreement I have had with the way WikiTree has approached DNA.
For the moment, let me agree with everything you wrote except that you are wrong in that I believe “Roberta Estes is mistaken.” Both Roberta and I have been involved with autosomal DNA from the beginning. I understand the terms she uses and the context of the articles she writes.
Roberta writes:
“Unless you are dealing with very close known relatives, like the Ferverda first cousins, there is no other way to prove a genetic connection to a specific ancestor.”
And
“One of the reasons genealogists always suggest testing older family members and as many cousins as possible is because triangulation becomes much easier with known cousins from particular lines to point the way to the common ancestor.”
I am sure we read these quotes differently.
I think some context is necessary....
One of the most frequently asked questions involves 3 matches that are “In Common With (ICW) each other in the DNA Relative lists. The top question is, “Do we share a common ancestor?” The answer is always, “You don’t know if you share a common ancestor unless you use triangulation.”
This answer is always used in the context of relationships that are unknown. I totally agree with her on the importance of mapping segments and fully support the method and reasons she writes in that article. Do you?
Roberta documents the 3 steps used to prepare for Triangulation and then on what to do with Triangulation results.
Step 1. DNA Matching – The tester’s DNA matches that of other testers at the company where they tested, or at Gedmatch.
Step 2. Ancestor Matching - Identify a common ancestor or ancestral line based on their previous work, aka, [Traditional] genealogy and family trees.
Step 3. Segment Matching - Utilizing chromosome browsers or downloaded match lists including segment information to identify actual DNA segments that match other testers.
Just so that there is no confusion, She uses spreadsheets, and this is done before any triangulation. In summary, find all the segments that are shared between every DNA tester in which the tree connects them. This includes 5th Cousins and above.
Here is another look at the steps....
1. The DNA Matching worksheet will contain a list of all DNA Matches from all sources.
2. The Ancestor Matching worksheet will be an extension of the DNA Matching worksheet. These identify single ancestors as far up the tree as possible, but when two common ancestors, you identify the Ancestral Line by identifying the children of the 2 Most Recent Common Ancestors. In both these cases, Traditional Genealogy is used. It's obvious don't do this with those DNA Relatives that do not have connected trees.
This specific ancestor identified DOES NOT have to be the Most Common Ancestor
Roberta suggests using Hints from Ancestry.com to help find these connections or a Surname search on FTDNA or Ancestry.com.
3. The Segment Matching worksheet is used to identify the actual DNA segments shared between two DNA testers who have known relationships supported by trees. Each segment is mapped to a single ancestor.A single ancestor may have more than one segment.
There is no upper limit as to the collection of these DNA segments. A 5th cousin match is the same as a 2nd cousin match.
Also, We collect all this information before the Triangulation step. Nothing has been stored in these worksheets involving triangulation at this time.
Roberta writes: Triangulation – The process used to combine all three of the above steps in order to assign specific segments of the tester’s DNA to specific ancestors
Once all segments have been assigned to an ancestor for those DNA testers have known trees, The triangulation process assigns DNA segments from DNA Testers without trees using the segment information of known DNA Relatives which are already stored away in the spreadsheet.
Roberta uses triangulation to help those without trees find connections by using the segment information that is mapped to known trees.
For example, the segments that I share with a known 3rd cousin 1x removed are mapped and used as the source. Then I compare all my DNA Relatives with those segments to see if any of the segments triangulate. If they do, I can at least say that those unknown DNA Relatives share a common ancestor along a particular family line of mine, and that of the particular family line of my known cousin. This helps me and them narrow down where to search for documentation that connects us.
As Roberta wrote: Triangulation is used "to point the way to the common ancestor.” but it does not necessary identify the common ancestor.
Lazarus does something very similar and automatically. An example of this is my deceased maternal grandmother’s DNA Relatives who Roberta would have identified by hand, are listed at LL895346.
There is no doubt that these people in her list are related to me via my maternal grandmother and not my maternal grandfather.
I prefer to spend my time working on making new connections, rather than “further confirming what I have already confirmed.”
