By Richard Weiss, Director of Programs, DNAadoption.com
Ancestry.com does a great job of finding common ancestors between DNA matches when both parties have trees. The layout is easy to navigate, intuitive, and well integrated, but sometimes the WRONG person or couple is shown as providing the shared DNA. This problem can occur when you share multiple common ancestors with a match but you or your match have have not yet found all of them.
Let’s look at an example of this.
In September 2016, I received a new match at AncestryDNA – B41. Based on a comparison of B41’s tree and my tree, Ancestry provided a “Shared Ancestor Hint” indicating that Barnabas Pratt was our common ancestor and that we were 5th cousins three times removed (5C3R) as shown below.
Figure 1: Ancestry’s “Shared Ancestor Hint”
Note that Ancestry’s “Shared Ancestor Hint” in the above image indicates that B41 and I match through my paternal side.
Perhaps this post needs the subtitle , “My Perfect Cousin Goes to GEDmatch.”
Most of us can keep track of information in spreadsheets. So how to do that with DNA? Well, the idea is to keep a list of matching DNA segments so that a new match can be compared to your known family members. That way you may be able to see where they fit in.
If you have tested at 23andme or Family Tree DNA, you can download your list of matches with their matching DNA segments either directly from your testing company or by using the tools at DNAgedcom. However AncestryDNA does not provide a list of matching segments.
Extract from my Dad’s Master DNA Segment Spreadsheet (click for a larger version)
Why would you want those? The short answer is to figure out which line a new DNA cousin belongs to. For the long answer, read on. For more posts about DNA spreadsheets click here or in the tag cloud, lower right hand column.
AncestryDNA testers can make a DNA segment spreadsheet by using any of a number of utilities at the GEDmatch web site. Start by uploading your raw DNA data (click here for that “how to” post). Your results will usually be ready for full comparisons the next day. Then buy the tier 1 utilities for at least one month ($10).
My preference for making a first spreadsheet is to use the Tier 1 GEDmatch Matching Segment Search. Then I go through the top matches from the ‘One-to-many’ matches report with that spreadsheet as a reference. I add notes on what I discover to my new spreadsheet.
Here is the step by step of what I did for my perfect cousin J.M. whose AncestryDNA results I blogged about in my previous post.
This is the first time I have had a cousin’s DNA test come out showing an ancestry composition that was 100% a single ethnicity. My cousin J.M. was not in the least bit surprised as she expected to be all Scandinavian. Five of her eight great-grandparents were born in Norway and the other three were born in the U.S.A. to Norwegian immigrants. But I was quite surprised because there is usually at least a trace of something else.
She shares my Norwegian born Munson (Monsen) great-grandparents as her great-great-grandparents making us 2nd cousins once removed. She tested at AncestryDNA to help me figure out where a related adoptee might fit in (no luck on that). The fact that she has a genetic genealogist for a cousin who would tell her what it all meant helped convince her as well.
I usually send cousins to my page comparing all the autosomal tests and let them choose. However I prefer Ancestry.com DNA testing for the interested, but non-genealogically serious, relatives who are online because it is so easy to see the relationships and use the green leaf hinting system. Also I was tired of having only one circle and her test would give me a second one. Those with colonial ancestry have plenty of circles and NADs (New Ancestor Discoveries) but we recent immigrants (1870s and 1880s) are lucky to have any. Last but not least, it was the cheapest test at the time she ordered it.
Now why is she perfect? It is not just the 100% Scandinavian but amazingly her top four matches are all second cousins from different pairs of great-grandparents! I have never seen that before either. Of course most of my tested relatives being from relatively recent immigrants, have no second cousins and almost no thirds showing at Ancestry .
Here are J.M.’s matches:
No matter how expert you think you are, there is always something to be learned from others.
When I saw that Michelle Trostler of DNA Detectives on Facebook and Identify Family was giving a talk on getting started with AncestryDNA for my local DNA special interest group, the North San Diego County Genealogical Society, I knew I should go, and I am glad that I did.
Personally, I use the Ancestry.com DNA testing service the least of the big three because all my ancestors are relatively recent arrivals (late 1800s and 1930s) so I do not have as many DNA matches there as elsewhere. Thus I know far less about using that site than the others.
Michelle is a knowledgeable and confident speaker. You can hear her at the upcoming i4GG seminar in San Diego as well.
Here are some of the tips from her talk that I found particularly useful.
You know you have an obsessive personality when a cousin’s DNA results come in and you put off as many plans as you can for the next 3 days in order to explore them. At least I have some observations to report on the new Ancestry chip as well as more data for my study of the Wold family.
Wold line cousins Kitty, Ed, MM
According to Ancestry, this new chip has dropped some less interesting SNPs and replaced them with medically relevant ones as well as ones more useful for determining ancestry composition. The details are at http://blogs.ancestry.com/techroots/customer-testing-begins-on-new-ancestrydna-chip/
GEDmatch only tokenized 455K of the 700K SNPs from that new chip. However when I imported the raw data into a spreadsheet I saw that there were 668,961 lines of data as opposed to the previous 701,495 (then subtract 20 for the header), so not that different a number. New is chromosome 26 which is for the mitochondrial DNA.
My Wold cousin MM is the cousin whose doorstep I arrived on, Ancestry kit in hand, because I really really wanted her results. Those of you who have been to my Triangulation talk or read the article here may have noticed that I had no other cousins tested who are descended from my great-grandmother’s brother Charlie, the one presumed to be Kristine’s great-great-grandad. MM’s test has rectified that although she is descended from a different wife of Charlie’s than Kristine.
Since MM is the half first cousin of Kristine’s grandfather, she and Kristine are half first cousins twice removed. Do they match at the expected level?