A Segment-ology TIDBIT

To paraphrase Lewis Carroll: If you don’t have an objective, any path will take you there.

I sometimes think about this with respect to genetic genealogy. Over 30 million people have taken a DNA test – there are probably many objectives, whether stated or not.

Over the past few years our community has developed a range of tools; and folks ask: “Which tool should I use? Which one is best for me?” Well… it depends. It depends on your objective(s).

You may have several objectives… I’m asking you to write one down. Edit your objective statement until it’s clear and concise. Make a simple sentence. Then we can think about the tools… which ones will help you achieve your objective.

Let’s look at some examples of objectives and the tools we might use. NB: These are *my opinions*.

  1. Determine my ethnicity (aka admixture, heritage, geographic mix, etc) percentages. You only need reading skills for this one. Take a test and read the results.


  1. Find my close cousins who have done DNA testing. Test at AncestryDNA and build a Tree of your Ancestors there. Then look at the ThruLines program for Matches who share a Common Ancestor with you (back as far as 7 generations). Also test at the other three major companies – you never know where a close cousin might test. For extra credit: verify their line of descent; contact them and share information.


  1. Determine a bio-parent. Let your Matches provide a pointer. At AncestryDNA, list your top Matches with Trees; list their ancestors; analyze these lists to find 4 families; build the families down and find two intermarriages – who are probably the grandparents. Sometimes it’s as easy as it looks, sometimes the answer is elusive. The point is: for this objective you often don’t need any of the Clustering or Triangulation tools. Your objective is very close, and your close Matches often have the information you need.


  1. Organize (group) my Matches on my Ancestors. Use Shared Match Clustering and/or DNA Segment Triangulation methods. Both of these methods work very well. It’s still up to you to determine the Common Ancestor within each group. The point is: These methods group your Matches on Ancestors.


  1. Determine which segments came from which Ancestors. This is Chromosome Mapping. We need DNA segment Triangulation to map the DNA – a lot of grouping work using data from GEDmatch, MyHeritage, 23andMe and FamilyTreeDNA. We need to determine a lot of Common Ancestors with a wide range of Match cousins – a lot of genealogy work (best done, IMO, at AncestryDNA – and often involving extending Matches’ Trees). We need to build the evidence for each ancestral line & segment combination. The point is: Several tools are needed – and it’s a major project.


Recommendation: Write down an objective statement. Then select the tools that will get you to your objective most effectively. For most of us, genetic genealogy is a hobby – so use whatever tools work best for you, and have fun.


[22BG] Segment-ology: What Is Your Objective? TIDBIT by Jim Bartlett 20220508