It is exciting when you find a new DNA cousin who actually has a family tree. However it can take days to wade through it looking for the common ancestor and more often than not, you do not find it. Sometimes that is because the ancestor is too far back in time. Other times it is on a line that is not documented or is just wrong. Also there can be spelling discrepancies or if you have Norwegians, naming differences (father’s name or farm name used for surname).
You would think that there would be good automated tools to do this and you would be right. These are the ones I know of.
Partial results of a GEDmatch compare one GEDcom to all run
A Norwegian, who turned out to be a descendant of my gg-grandparents Jørgen Wold and Anna Knutsdatter of the Drammen area, tested his DNA on 23andme and came up a close match (3rd-5th cousin) to my Dad with 35 cM over three segments of matching DNA (0.48% shared). Most matches called 3rd to 5th have been just two segments and have turned out to not be that close but rather to share two ancestors. However Henrik was on GENI.com and an exploration of his tree found that he was descended from Jørgen Wold’s daughter Olava. This is the first time it has been so quick and easy to find a relationship! He is much younger than I am, so two generations further down the tree. Naturally I had to use the new DNAgedcom feature where I could compare him to all my shared profiles and see who else he matched. Here is the plot of his matches with my family and the larger shares (surnames removed for privacy except from my Dad and brother) created with my DNA segment mapper tool: