How my AncestryDNA Match stands up in Gedmatch

In my last post, I evaluated one of my "shaky leaf" matches whom AncestryDNA predicted would have a shared ancestor with me. We compared our online family trees and determined that we were connected via the Long/Lang line of Jasper County, Georgia. This match was instrumental in both of our research efforts because conflicting documentation regarding the Long/Lang surname had made it difficult to place our ancestors with the correct set of parents. This DNA match allowed us to confidently place our ancestors within the same family of John and Margaret Lang.

I have to admit, by the time I finished writing this last post, I was pretty hooked with using AncestryDNA. But I know when something seems too good to be true, it usually is. I knew there were going to be limitations with the AncestryDNA service going in to it. And I wanted to put this to the test. Unfortunately, my suspicions were confirmed:  My AncestryDNA match and I were not really connected, genetically speaking,  via the Lang/Long line!

My Pedigree:

My descent from John and Margaret Lang is as follows:
Basheba Long & Washington Phelps
Lucinda S Phelps & Burwell Binns
Milton A Binns & Susan Ann Dupree
John Milton Binns & Perthinia "Pert" Brooks
John Brooks Binns & Blanche Kathryn Hill
B Binns and D Smith - my grandparents
T Smith & M Godwin - my parents
Ginger Smith - me

I have tested myself, both of my parents, and 3 of my 4 grandparents to date. If I received any DNA from my Lang / Long ancestors, I would have inherited it from my Father, who inherited it from his mother, my grandmother, B. Binns. However I tested all of us at FamilyTreeDNA and tested only myself at Ancestry.com. In order to compare any DNA results from AncestryDNA to results from FamilyTreeDNA, they must first be uploaded to a 3rd party website called Gedmatch.com. GedMatch allows you to compare autosomal DNA across all 3 testing companies - Ancestry.com, 23AndMe, and FamilyTreeDNA. It's FREE and easy to use!

What I Did:

I convinced my match to upload her AncestryDNA results to Gedmatch.com. Once uploaded, I compared her results to my grandmother, B. Binns, who descends from our Lang / Long ancestors. I expected to see a good match since my grandmother is closer to the shared ancestor than I am. Surprisingly, there was NO MATCH. Not only was there no match, but my match did not share the same segments of DNA with my grandmother that she shared with me.

Here is a list of segments S.A.T. shares with me:

Chr	Start Location	End Location	Centimorgans (cM)	SNPs
3	25052678	30683436	7.2	1487
7	88445250	91973622	3.0	731
7	117280746	123629411	3.5	933
13	66743336	69809017	1.9	739
18	22684849	25803725	3.3	977

Largest segment = 7.2 cM

Total of segments > 1 cM = 18.9 cM

Estimated number of generations to MRCA = 6.8

Here is a list of segments S.A.T. shares with my grandmother:

Chr	Start Location	End Location	Centimorgans (cM)	SNPs
1	95871096	98378320	1.6	970
2	34843826	37164843	2.6	705
3	47546444	53219643	1.0	801
10	73326487	77694862	2.8	759
12	20794787	22833572	3.1	812

Largest segment = 3.1 cM
Total of segments > 1 cM = 11.1 cM
Estimated number of generations to MRCA = 7.2

There are no overlaps between where she matches my grandmother and where she matches me.


Is this For Real?

If you look at how S.A.T. matches to me, you will see that the MOST that we match on is 7.2 cM on ch 3. Our total matching segments are only 18.9 cM. This is a very low resolution match in my opinion. In order for someone to be considered a "match" in FamilyTreeDNA, they have to share at least one segment of DNA that is 7 cM long - this requirement IS met in this example. The 2nd requirement by FamilyTreeDNA is to have a minimum of 20 cM total DNA shared between two people to be considered a match. S.A.T. and I only share a total of 18.9 cM, so this would not fulfill the requirement to be considered a match in the FamilyTreeDNA system. So is this a real match or not?

Not Maternal..., so Paternal?

Although I was discouraged, I did not let this set back keep me from looking at my match more closely. Although she wasn't a match to my grandmother as I expected, I then compared her to the rest of my family members, including my grandfather and my mother and her father. She DID come back as a match to my paternal grandfather.

Here is a list of common chromosome segments between my match and my grandfather:

Chr	Start Location	End Location	Centimorgans (cM)	SNPs
3	25052678	30677144	7.2	1475
5	50991761	54288881	2.9	846
6	151277980	153997386	4.8	924

Largest segment = 7.2 cM
Total of segments > 1 cM = 14.9 cM
Estimated number of generations to MRCA = 7.0

Here is a list of common chromosome segments between my match and me:

Chr	Start Location	End Location	Centimorgans (cM)	SNPs
3	25052678	30683436	7.2	1487
7	88445250	91973622	3.0	731
7	117280746	123629411	3.5	933
13	66743336	69809017	1.9	739
18	22684849	25803725	3.3	977

Largest segment = 7.2 cM

Total of segments > 1 cM = 18.9 cM

Estimated number of generations to MRCA = 6.8

You can see that my match shares the SAME chromosome segment on ch 3 from 25052678 to 30683436 with me that she shares with my grandfather. That segment is 7.2 cM long. This means that our genetic connection came down to me through my grandfather, not my grandmother, and that our common ancestors ACCORDING TO THE DNA, are not the Langs or Longs, but a different set of ancestors shared on my grandfather's side.

I am happy to have connected with my match on the Lang / Long line, and to have extended my tree out further with the addition of her line; However, I can no longer conclude that "DNA proves that my Basheba Long was the daughter of John Lang" ...because I am a DNA match to other descendants of John Lang....

This is where we have to draw the line between DNA testing and genealogy and make distinctions about what each one can do. My mantra has always been, "If you're going to do it, then do it right!" The bottom line is that you can't really use one research method independent of the other. You can't rely solely on the DNA to give you answers and sometimes the paper trail just isn't enough.

Conclusion:

AncestryDNA is a good tool to use to find connections and to expand your paper trail or family tree. However, its usefulness is limited with regards to DNA because the chromosome data is not made available to the testee. In this example, I found a connection with my DNA match via our online trees and genealogical paper trails. However, when I input the raw DNA data into Gedmatch.com, I realized that the DNA connection, represented by the DNA that is shared between us, was not carried down to me from my Lang or Long ancestors like the paper trail suggested. A side by side comparison of the segments my match shared with me to the ones she shared with my grandmother clearly showed that I did not receive the segments that I shared with this match from my grandmother who is a direct descendant of the Langs/Longs. Additionally, when I compared my match to my grandfather, it was clearly apparent that the segments I shared with my match were carried down to me through my grandfather because he, too, shared those same segments with my match.

Now, who's going to break it to my match that we have to go back to the drawing board and start over???

Related Posts: 

My AncestryDNA Test, part 1 - A look at the Closest Matches

My AncestryDNA Test, Part 2, The Shaky Leafs