A Segment-ology TIDBIT
I’ve been explaining and discussing and arguing about Match Clusters recently. One debate concerns whether a Cluster is formed around an Ancestor (CA) or a Triangulated Group (TG). I argue that Clustering tends to result in 4 or 8 or 16 or 32 Clusters (or some other number of Ancestors in a given generation), depending on the shared segment cM threshold used. It might seem like I know the Ancestors and/or the TGs for each of my Clusters.
Confession time – I do not!
I’m working hard to determine as many as I can, but the current status is still spotty. I’m having a fairly good experience with TGs (98% of my DNA is covered by TGs); and know some Cas (over 80% of my TGs are known to the grandparent level). But I still have a long way to go on Chromosome Mapping. “Walking the Ancestors Back” on each TG is the name of that game.
I’m fairly new to Match Clustering, and as I look over that data (from my recent Cluster Matrix of AncestryDNA Matches over 20cM), I see lots of bare spots. I do see some trends, but in no way have I determined distant Ancestors (the CAs) for each of my Clusters. Nor have I determined the TGs for each of my Clusters – some Clusters have multiple TGs, and many have no TGs (after all, this Matrix is based on AncestryDNA data). It will take a while to analyze and weigh the information I’m collecting.
I’m working on a better analysis and a report of the one Cluster Matrix I’ve tried so far – stay tuned!
[22AA] Segment-ology: Confessions of a Match Clusterer TIDBIT by Jim Bartlett 20190214