It is very interesting to look at the overlapping DNA segments of one’s matches in order to figure out where they may have come from and how they might be related. It also helps with tracking these relationships and comparing the results from different sources. Personally I know when someone matches my 2nd cousin Dick that the relationship is on dad’s father’s line. My next task will be to start diagramming the possible relationships based on who matches whom among all our new distant cousins.*
To find the DNA segments where you match another person at 23andme that you are sharing with you put your cursor on “My Results” in the very top menu bar and then click on “Ancestry Tools” at the bottom of the second column of selections to get the page that lists Family Inheritence: Advanced. Within this function you select the person to compare to on the left and all those to do it with on the right. So typically I take a new person and compare them to me, my brother and my Dad; then various cousins. You need to select the table version to get the numbers shown in the spreadsheet below.
Here is how I track overlapping segments. I make one spreadsheet for each person I am looking at, sorted by chromosome, segment start, segment end and length. I use the same columns as the 23andme table view of my genome shares but add one column at the beginning marked with a P or M (paternal or maternal side match) whenever I know it. Then I add a column for the most recent common ancestor (MRCA), one for known relationship (when found), and another one for notes where I put comments like “same match with Kitty, no match to Dick, matches Jane elsewhere).
Here is a sample from my spreadsheet entries on chromosome one for my Dad, with the names blacked out. I typically only add people I have shared genomes with at 23andme or have had contact with through other sites. The template for this spreadsheet is in my Downloads area. Since this post was written I have started using a second spreadsheet to manage the details of my correspondance with matches, that template is also in the Downloads area.
Another spreadsheet that is very useful is the master sheet of all your matches that you can download from 23andme‘s Countries of Ancestry (COA). To do that go to ancestry labs and click on “My Results” in the very top menu bar and then “Countries of Ancestry”.Wait for the page to load and then scroll down until you see a big button that says:
Download yourname‘s Ancestry Finder Matches (CSV)
Click on that to download the file. Open that file in excel and sort it by chromosome and segment start in order to look at the overlaps.
I like to look at this sheet to check on “hotspots” where there are many matches. However you need to be sharing to compare people you match to each other. For example, one distant cousin overlaps with Dick on the master chart but when I compare him and Dick to each other there is no match there. Thus I know that person’s segment is from the other side, maternal not paternal. Every chromosome is paired and so every segment is really there twice. This even if the numbers match up you need to compare them to each other to be sure there is a match.
Then of course there is the fun of looking at each other’s pedigrees for the paper trail to a common ancestor. It is a lot easier when they are on Geni.com as well. Sometimes the relationship is quite far back. Here is a list of the MRCAs I have found so far with some of our new distant cousins:
- Gunnar Olafsen Gangså 1570-1639
- Ingeborg Djupesland (Bårdsdatter) b 1650
- Knut Pedersen Åmot 1786-1851 (a fourth cousin)
- Ola Narvesen Glaim 1621-1714
- Bjorn Ve (1725-1792) (a fifth cousin)
Part of the problem for us is that when you are born of the youngest son of the youngest son in these large Norwegian families your generations get longer than every one else’s so often we are once or twice removed in generations from our new cousins of our own age.
*Since this post was written I have created several tools to make a picture of segments. One to show what DNA you have inherited from which ancestor, see the ancestor chromosome mapping tool page. Another tool to look at multiple shared segments from many possible relatives, the overlapping segment mapper. Additionally a tool for a detailed view of a single chromosome. the one chromosome mapper.