In this post, I would like to look at using three DNA tools in conjunction with each other. Those tools are AncestryDNA’s Shared Ancestor Hints (SAH’s), Visual DNA Mapping, and Triangulation. This will be a triangulation of DNA tools, so to speak.
The above diagram is meant to show Shared Ancestry Hints at the top. The lower left is the visual mapping and the lower right is a symbol for triangulation. In my last blog, I looked at an SAH and visual mapping example. This blog will bring in another tool: triangulation.
Shared Ancestry Hints (SAH’s)
SAH’s are probably the least reliable of the three DNA analysis tools, but they are like the front man or salesman. They are the first easy introduction to a possible shared ancestor based on a DNA match. They are also the least intelligent. Ancestry takes a tree and takes a DNA match and blindly puts them together. Here is my wife’s aunt Lorraine’s SAH that I looked at in my previous Blog:
Fortunately, Ann uploaded her DNA to Gedmatch. Here is how the match looks between Ann and Lorraine:
This is a huge amount of DNA shared for the proposed 8th cousin relationship. This Charles Pouliot at the SAH was born in 1631.
This method, developed by Kathy Johnston, compares three siblings and draws a map showing the DNA that the three siblings received from their four grandparents. Here is the map I made in my previous Blog for my wife’s Aunt Lorraine and her two siblings:
After looking at the map for Lorraine and comparing it to the SAH, I determined that the Chromosome 4 DNA match between Ann and Lorraine could not be on the Pouliot side as hinted at by the SAH. Lorraine’s match with Ann was squarely in the largest maroon LeFevre segment between 33 and 40 above. As the goal of the previous Blog was to compare the SAH with visual mapping I did no further analysis. I could not prove that the match indicated LeFevre or LeFevre ancestor DNA. I also could not prove that it did not represent LeFevre or LeFevre ancestor DNA.
As the above analysis was limited by the goal of that Blog, I wanted to look further into the DNA match between Lorraine and Ann in this Blog.
Triangulation is the matching of three or more people with each other on the same segment of the same chromosome. This specific DNA matching suggests a common ancestor that sent his or her DNA down to the three or more matching people. Further the matching would in most cases rule out spurious, false or Identical by Chance (IBC) matches.
candidates for triangulation
The people that I am looking to triangulate are:
- Ann and Lorraine
- Lorraine’s siblings Richard and Virginia
- Lorraine’s Pouliot second cousins. A Pouliot DNA match on Chromosome 4 has been ruled out by Visual Mapping, but there could be a match on the other 3 Chromosome matches.
- Lorraine’s 1st maternal cousins. These two match on the LeFevre and Pouliot sides.
Of the three siblings, only Lorraine matched Ann on Chromosome 4. Ann did not match the two Pouliot 2nd cousins at standard Gedmatch thresholds. Ann also did not match one of Lorraine’s first cousins, but matched the other one – Joseph:
Here is a graphic of the testers. I forgot to mention John above. He also did not match Ann.
This graphic shows Pouliot at the top, but the mapping showed that the Chromosome 4 match came from the LeFevre side. Here is Martin LeFevre courtesy of cousin Patricia:
back to the triangulation
Lorraine matches Ann and Ann matches Lorraine’s 1st cousin Joseph between 32 and 40 on Chromosome 4. Do you think that Lorraine matches her first cousin at this location? The answer can be seen at Joseph’s matches on the Gedmatch Chromosome Browser:
These are Joseph’s matches to:
Joseph and Lorraine have a large match between 13 and 65M. That means that Triangulation has been established between SAH Ann, Lorraine and Joseph.
What Have I Shown?
I have shown that:
- The match between Ann and Lorraine on Chromosome 4 is real.
- That match indicates that Ann, Lorraine and Joseph have a common ancestor
What I don’t know:
- Right now I have not determined the common ancestor indicated by the Triangulation. AncestryDNA indicates a choice of 15 ancestors shared between Ann and Lorraine. One of those, the Pouliot ancestor shown on the SAH has been ruled out. That leaves 14 other French Canadian names to look at!
- I don’t know which segments were considered in the AncestryDNA match as Ancestry does not choose to share that information. Gedmatch showed matches in 4 segments on 4 chromosomes. AncestryDNA only showed two matching segments.
Looking at Lorraine and Ann’s genealogy: Shared Ancestral Names and Shared Matches
Here are the shared ancestral names between Lorraine and Ann:
Further, Ann and Lorraine have shared AncestryDNA matches. Here are the shared ancestral names with one of those shared DNA matches that has a tree:
A good place to start looking would be at Bergeron, Bouchard, Fortin, Girard, and Paradis.
Here is another Shared Match with a smaller tree:
This seems to limit the look to Bouchard, Fortin and Girard. Just to make life interesting, all these names are also in the better documented Pouliot tree. Yes, that is the same Pouliot where the DNA between our matches did not come from.
Here is the Tree I have for LeFevre:
See, I have a few blanks. On this tree, it appears that Bergeron (shown twice) could be a good bet to pursue. Perhaps Lorraine got Bergeron DNA from Martin LeFevre’s paternal and maternal sides. Under that scenario, she could have shared one of those 4 segments with both Ann and Joseph on Chromosome 4.
some late breaking news
Since starting this Blog, I decided I needed to spruce up the French Canadian side of my wife’s Ancestry Tree. I’ve worked on that a little and see there is at least one Bergeron common ancestor between Ann and Lorraine on the LeFevre side:
The SAH Anne’s ancestry is on the left and my wife’s LeFevre’s ancestry is on the right. I checked some other possible common names and found no obvious matches. Perhaps the above Jean-Baptiste Bergeron is the one who sent down his DNA to three of his descendants.
Here is what the shared genealogy looks like on a chart:
I would expect a new Shared Ancestor Hint at AncestryDNA based on the updated genealogy I filled in.
Summary and Conclusions
- The Shared Ancestor Hint was like the salesman that got his foot in the door. His sales pitch, however, was based on shaky information. That shaky information is the ancestor trees as many others have pointed out. There is also an inclination by some to extend the trees of the names that they are more familiar with rather than extending all the family names back in time. For example, my wife’s grandmother was a LeFevre. When I was researching, I didn’t take the time to follow every line back to France via Quebec. Instead, I researched the familiar LeFevre line.
- The visual mapping showed that the Shared Ancestor Hint could not indicate a match between the DNA and the common ancestor shown (Pouliot). This was a tearing down phase that showed something to be wrong, but did not show what was right
- The triangulation was a re-building. It showed that the Chromosome 4 match was indeed valid and pointed to a common ancestor.
- As a result of the Chromosome 4 triangulation, it showed that it would be worthwhile to further pursue who the common ancestor may be between Ann, Lorraine and Joseph. My initial shot at that indicated a possible Bergeron common ancestor.