DNA Clusters: Mountains and Valleys

Dana Leeds’ recent blog post about “Who Is in a Cluster” demonstrates that although all people in a cluster share DNA with one person in the cluster, they don’t necessarily share DNA with another member of the cluster.

Curious as to what this would look like with my Crawford branch of my tree, I looked at the DNA matches I share with a first cousin once removed. At first, I was trying to map out all of my known matches. However, this became cumbersome since I have a lot of 2nd cousin matches. As I was creating my matches diagram, I realized that I needed to be looking for matches that were for the different surnames.


The blue box represents myself and the yellow box is the cousin used to create the cluster.

  • My ‘Valley’ is the common ancestors between myself and E: Judson Foster Crawford and Josie Winifred Hammond. I have shown two other matches thru these common ancestors: M and M2nd. Not only are we all cousins (myself, E, M and M2nd), but we would all share DNA with everyone else mapped out in the diagram.
  • I have two ‘hills’ in my diagram: Washington Marion Crawford/Mary Foster and Richmond Hammond/Sarah Ralston. PrivateLida  and Private Hattie are both related to the four cousins in the valley but are not related to each other.
  • I have diagrammed 3 mountains representing three lines: Foster/Ostrander – Hammond/Fisk – and Ralston/McCormick.

By visualizing the cluster in this way, I have identified matches that I can use to figure out some of those matches whose trees are sparse or missing. For example, if I look at matches shared with PrivateEliza, I will be identifying matches who are either part of the valley with a common ancestor of Zebulon Foster and Caroline Ostrander or who descend from an ancestor of Zebulon Foster or Carolne Ostrander. I could then create another diagram for this cluster 
This diagram also pointed out a missing ‘mountain’. I don’t have a ‘mountain’ for my Crawford line back to the Nelson G. Crawford or James Crawford generations. Although ThruLines shows that I have some matches who descend from Nelson G. Crawford and James Crawford, only one of those matches shares DNA with the cousin I used to create this diagram. Unfortunately, I didn’t recognize this match when creating the diagram, thus leaving out a ‘mountain’ for Nelson G. Crawford.

Working thru the creation of my diagram, I have made two observations:

  • I should have checked ThruLines to see whether there was a match to fill in the hole in my diagram.
  • Excel likely isn’t the easiest software to use to create this diagram. 

Thank you Dana Leeds for prompting me to look at my DNA results in this way.