Ancestral DNA %

Those of you with Autosomal DNA tests often ask why you don’t have genetic matches to cousins with documented shared ancestry.

We all inherit a different mix of parental DNA with 50% coming from Mom and 50% from Dad. However, my 50/50 is a different 50/50 than my sister’s, for example. The same thing applies to cousins. The amount of shared DNA decreases with every generation that separates us from our most recent common ancestor. Even if my cousin takes a DNA test that won’t guarantee that we will match each other.

Percentage of Inherited DNA

When reviewing your Autosomal DNA (atDNA) results, you might find some matches to people who also claim to descend from a more distant ancestor. That’s a genetic clue, and not conclusive proof of that shared ancestry.

Proof takes the triangulation of of more than one match sharing the same DNA segment/s. This is easier to discover if your most recent common ancestor is no more than a few generations away. Further generations means the percentage of ancestral DNA you inherited from that ancestor is very small. Finding multiple cousins who share that exact tiny segment is a challenge.

To maximize your chances of proving your extended ancestry with atDNA testing, I recommend the following:

  1. Start with an AncestryDNA test. They have a huge database. You’ll probably get 10 times the number of Guthrie matches there than you do anywhere else.
  2. Transfer your results to Family Tree DNA using their free Autosomal DNA Transfer Process. This gets you access to a second database, but it also allows you to officially add your kit to the Guthrie DNA Project.
  3. Join the Guthrie DNA Project. This provides you with access to free help interpreting your results and lets you participate in our growing understanding of how we relate to one another.