It has been quite surprising to me to see how often 23andme claims Norwegian relatives are more closely related than they in fact turn out to be. This particularly shows up among those descended from the farms around the Stordalsvatnet (a large glacier lake upstream from Etne in Hordaland Norway) such as Skjold, Frette, Tveito, Lussnes, Sande, Hovland, and Håland to name just a few (Click here for a picture towards Frette from google maps). So when last at the library in Salt Lake City, I photographed pages from the Etnesoga farm books for all these ancestral farms in order to discover the many ways these folk intermarried in recorded genealogical time. I have been entering all this data on GENI and ancestry but have yet to discover good ways to display family trees with so many cousin marriages.
So Dad has an expected 3rd to 4th cousin “MB” from Etne who shares 4 good sized segments and .66% of her DNA with him. She is in fact twice a 4th cousin once removed and once a 6th cousin to him (so far). Most delightful however is that she has four generations of family tested. So here is a picture made with my segment mapper tool of her versus her daughter (.55%), two grandsons (.52% and .38%), a great granddaughter (.39%) and a great grandson (.26%). Clicking on the picture will take you to a copy of the actual output with mouse-over popups showing the centimorgan (cM) values.
As expected, her daughter is a solid blue line as she has half of all her DNA, thus one of every chromosome pair, from her mother. Looking at the two sons, you can see that they inherit some of the same DNA and some different. Notice how all of chromosome 21 has been passed intact all the way to her g-granddaughter. This is the smallest chromosome. The X inheritance is also of interest as MB’s daughter gave each son only one piece from her mother, and not the same pieces. This fits with what I have seen with sluggish recombination on the X
So now to look at their DNA versus my Dad and a few other relatives. MB’s grandparents from Etne are first cousins to each other and my Dad has a grandfather from Etne who is their 3rd cousin once removed (and their 5th cousin 1R). So here is Dad versus these six people . He matches MB on 4 segments which is really a lot of DNA for such a distant relationship Also notice that these DNA segments have been passed along with almost no loss in size when they do get inherited (click the image to see the full html page with mouseovers).
My picture has the same matches from chromosomes 12 and 16 that Dad has with all of these Etne cousins whereas my brother has the chromosome 1 and 12 matches.
I have lots more cousins tested who are descended from these interrelated families. Here is a 4th cousin of mine (3rd 1R to Dad) who also has another ancestral relationship to MB besides the one shared with me. His sister has the same matches except for the one on chromosome 5 and his first cousin has only a tiny match (6cM) on chromosome 8 with MB and her daughter.
And here is what they share with my first cousin PG, some X at last!
I have another 3rd cousin once removed on the Skjold line who matches MB and family but since all the matches are below 6cM they are not conclusive and somewhat inconsistent (one segment seems to skip the mother but was probably just too small to register)
I really enjoy this display of DNA inheritance; so pleased to have so many Etne cousins tested. Now to recruit a few more by sending them a link to this article!