Sunday, September 7, 2014

How my AncestryDNA Match stands up in Gedmatch

Old Man Wagging Finger
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 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 allows you to compare autosomal DNA across all 3 testing companies -, 23AndMe, and FamilyTreeDNA. It's FREE and easy to use!

What I Did:

I convinced my match to upload her AncestryDNA results to 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:

ChrStart LocationEnd LocationCentimorgans (cM)SNPs

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:

ChrStart LocationEnd LocationCentimorgans (cM)SNPs
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:

ChrStart LocationEnd LocationCentimorgans (cM)SNPs

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:

ChrStart LocationEnd LocationCentimorgans (cM)SNPs

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.


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, 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


  1. Ginger
    Have you heard about/seen the Google Chrome browser extension, AncestryDNA Helper?
    It's free (in the Chrome web store) and was developed by an Ancestry subscriber. It scans all your matches (even multiple tests) and adds a some features that AncestryDNA's interface is missing. (It seems to find more surname matches than Ancestry's search. And there is an icon added to show matches in common with any other tests you manage.) Sadly, it does not add a chromosome browser. The scan data goes to you own computer and not out there somewhere else. Though it only works on Chrome, it has helped me greatly in going thru my matches. It does take a quite a while to do the first initial scan. I had two tests (150 pages and 175 pages of matches) and it took about 10-12 hours and then about 13-14 hours to complete the scan. You can stop and resume scanning or just let it run during the night though you might need to tell the computer not to go to sleep so it does not get hung up. There are brief instructions in the extension, there's a user created how to pdf in the yahoo group but you need a yahoo email to get to it.
    By the way, there are up to 50 matches on a page. So count how many individual matches are on the last page and then times the number of remaining pages by 50 and add. To figure the number of matches at the distant cousin level, start subtracting the number of the other closer relationship levels from the total.

    AncestryDNA Helper also lets you download a list of your matches or ancestors of your matches to an Excel file. That's proven useful also.

    Gone Researching

    1. Hi Goneresearching, Yes, I have installed the extension for another dataset that I am working on. It is very nice! and I love being able to search by user names! Thanks for the explanation.

  2. Kind of disappointing but hopefully you'll find the connection on your grandfather's side. I really wish AncestryDNA will get a chromosome tool what's the use of going as far as testing without making accurate comparisons? Great post!

  3. Hi Victori thanks for your kind words. I think more and more people are becoming aware of the need for the chromosome browser and other tools. But Ancestry seems to be hanging back which is unfortunate.