Tuesday, February 23, 2016

Triangulation Example

Some ISOGG group members at Facebook have been wanting to see examples of triangulation at the 6th cousin level. My Melvin family segment triangulations would be closest to this cousin range. One match is a 5th cousin 1x removed, which is pretty much equivalent. This triangulation is with descendants of  John Melvin b. abt. 1776, Maryland and Mary Redden b. abt. 1777 Maryland. The Melvin segment matches are as follows (see chart above, which includes my Aunt, myself, and two other distant cousins):
  1. The light blue segment, on chromosome 1, represents my Aunt on my Paternal side. She shares this 22.1 cM segment with a 3rd cousin. This match is a descendant of our common ancestors John Melvin and Mary Redden.
  2. The light pink segment, on Chromosome 1, of the same size is my segment match with the same person as my Aunt. This is a 3rd cousin 1 x removed to me.
  3. The smaller dark pink segment sandwiched between the ones described above belongs to another John Melvin and Mary Redden match. This 14.2 segment is also shared by my Aunt and myself. This match is a 5th cousin to my Aunt, and a 5th cousin 1x removed to me.
  4. The green segment is where the 3rd cousin range match, to my aunt and myself, matches our 5th cousin range match. These 5th cousins share a slightly larger segment which is 18.6 cMs. You'll notice it extends passed the segments my aunt and I share.
Elijah Hicks and John Melvin sign
marriage bond
Both of our Melvin matches have good trees. Our 5th cousin range match has all lines going out at least 6 generations. Looking at other possible lines which may also be the source of these segments I don't see any other matching ancestors.

My proof of relationship to this Melvin family is through  US Census research, a bible record, and the Elijah Hicks and Nancy Melvin marriage record.

Examining whether these segments are likely IBD it would seem that they are in that cM range. Checking to see if my mother shares the same segment on chromosome 1 with all of these matches. No she doesn't match. You can see here my comparison between my paternal aunt with my mother. All of our Melvin matches matched between 165,698,481 to 180,598,459 on chromo 1,:

My Mom and my Paternal Aunt's shares in the same place as a 3rd cousin and 5th  Melvin cousin match

Looking a little more for possible places where our ancestors may have crossed paths I made this chart. Are we all from the same ethnic background? Could these be population segments? My paternal aunt and I have a fairly unique ethnic makeup. My 3x great-grandparents William Owens b. 1820 and Nancy Hick b. 27 Oct 1831 and their ancestors make up our only Colonial American line.

Here you see our lines are Austro-Hungarian, French Canadian, Colonial American, and Irish Catholic.  When looking at the places of origin for the Melvin matches of my aunt and I, we find both have quite a bit of Colonial Ancestry. I don't see any other shared ancestors between either of the other two testers. We all have Colonial Ancestry, but no other shared ancestors. My Colonial line on the paternal side is very small. Neither tester has French Canadian roots like my Aunt and I. Neither has Burgenland, Austria ancestry, as my Aunt and I do. They don't have Irish Catholic roots either. Our 3rd cousin match has a large Scandinavian line, which none of the rest of us have.

I think it's more likely than not that this Melvin Family triangulation is a good triangulation.

Some of those who would discredit triangulation would say, well it could just be a coincidence that we all match in the same place on chromosome 1. They would also say it's nearly impossible to share segments with cousins in that range. Chances of matching at all at that range are minuscule. It would be like being struck by lightening to triangulate at that cousin distance, so they would say. What are the chances we would all match in the same place and share the same ancestors? Wouldn't that be as unusual if you are sticking with statistical probability? I have a feeling we have a long way to go before we even really know what the statistical probabilities are? We aren't able to do enough comparisons, or look at enough possible triangulations to get an idea of how likely or unlikely they are to occur. A company is holding a huge amount our genome information, but they aren't sharing it with customers. They will sell genomes for medical research though.

PS This company now has no chromosome browser in 29 countries!

1 comment:

Jason Lee said...

Looks like you've built a good case. Far stronger than anything you can build with distant cousin hints using the tools at Ancestry.

"PS This company now has no chromosome browser in 29 countries!"

Ha! That's funny.