Like many of the genetic genealogists out there, I’ve come to love DNA Painter as a tool for getting the most out of my DNA test data. So, today I want to share how I use it to help me better understand my DNA matches.

In order to keep this post fairly short and sweet, I’m going to assume that anyone reading this will have some familiarity with the basic concepts in genetic genealogy. If you don’t, you might want to read about using your match list at Ancestry, or check out some of my advice for beginners, relating to DNA testing, or visit one of the many other blogs or Facebook groups out there that are geared toward genetic genealogy.

DNA Painter is a fantastic tool for many reasons, but I especially love it because it gives me one place to keep all my segment data from the various test companies (Family Tree DNA, MyHeritage, and 23&Me) or third-party applications (GEDmatch) that provide it, visually identifying which segments were inherited from which ancestors. Why is this helpful? Here’s an example.

Let’s say I have a match at 23&Me who is entirely unknown to me. We’ll call him K.C. (All initials of living individuals have been changed in this post.) He has no information in his profile on 23&Me regarding where he lives, when he was born, or any surnames he’s researching. Half his ancestry is Northwestern European, and the other half is Ashkenazi Jewish, so we’re almost certainly related on the Northwestern European side. His breakdown within that category isn’t especially helpful; we’re both a mix of British & Irish, French & German, and Broadly Northwestern European in varying proportions, which represents my paternal side. I don’t know where he lives or when he was born, and his name is sufficiently common that standard internet search techniques (e.g. searching for death notices in which he’s named as a surviving relative, or searches of databases such as Ancestry and Newspapers) don’t offer any clues. He’s pretty much a mystery.

An examination of Relatives in Common offers some insights, however. 23&Me reports that K.C. and I have relatives in common, which include E.T., E.S., and K.M., and that we all share DNA overlap, which is typically an indication that a particular segment of DNA was passed down to each of us from a common ancestor. Unfortunately, the situation with the latter two matches is not much better than it is with K.C. There’s not much information to go on in their profiles, and I don’t know how I’m related to them. However, I do have one glimmer of hope that I can leverage: E.T. is my second cousin. In “View DNA Details” at the 23&Me site, I select, “Compare with More Relatives,” and take a closer look at Chromosome 7, where we all share DNA, using myself as the base comparison (Figure 1).

In the diagram above, the underlying gray represents my paternal Chromosome 7. The purple segments are where my second cousin, E.T., shares DNA with me on that chromosome. As per the key, the orange segment represents shared DNA that I share with K.C., the yellow is shared DNA with E.S., and the blue is shared DNA with K.M. The areas where the colored regions stack on top of each other are areas of triangulation, where we all match each other, presumably because we share a common ancestor. But which ancestor might that be?

While my match list at 23&Me doesn’t provide any clues in that regard, my ancestral chromosome map from DNA Painter does. My ancestral chromosome map represents a visual summary of all of my known DNA match data from any test company or third-party application which provides segment data. Each time I’m able to document a genealogical relationship between myself and a living relative whose DNA data are found at one of those websites, I can “paint” the segments of shared DNA onto my ancestral chromosome map, and assign those segments to the common ancestral couple from whom that DNA match and I both descend. The more complete I can make my map, the more useful it is at informing my understanding of unknown DNA matches.

Let’s take a look at my paternal Chromosome 7 on my map from DNA Painter (Figure 2).

The map consists of a number of colored bars of varying lengths. Each bar represents a segment of DNA shared between me and a living DNA match. I’ve removed the names of the matches in most cases, although the colored bars that are relevant to this discussion are identified by black bars on the right, labelled with the pseudo-initials of the DNA match.

The key tells us that my ancestral map of my paternal Chromsosome 7 consists of DNA segments that can be traced to one of three ancestral couples: Wenzeslaus Meier and Anna Goetz (my great-great-grandparents), Katherine Walsh and John Frank Roberts (my great-grandparents), and Robert Walsh and Elizabeth Hodgkinson (my great-great-great-grandparents). Figure 2a shows a family tree, for reference.

We know that my paternal copy of every autosome (Chromosomes 1-22) will contain DNA inherited from both my dad’s mother, Marie Boehringer, and my dad’s father, Harry Roberts. We can take this a step further. Any DNA which I inherited from my paternal grandmother, Marie Boehringer, must have been given to her by either her father, John Boehringer, or her mother, Anna Meier. Similarly, any DNA which I inherited from my paternal grandfather must have come from either his father, John Frank Roberts, or his mother, Katherine Walsh. So each and every one of my paternal autosomes could be said to be a mixture of Roberts, Walsh, Boehringer, and Meier DNA. Bear in mind that the same pattern would be true for the chromosomes I inherited from my mom; those chromosomes must represent the four surnames of her grandparents.)

Going back now to the chromosome map, the map gets further refined as I am able to identify DNA matches with whom I share more distant ancestry. As mentioned, there’s a green segment on the map that represents DNA inherited from my great-great-great-grandparents, Robert Walsh and Elizabeth Hodgkinson. They were the grandparents of Katherine Walsh, so it makes sense that this green segment of DNA would necessarily overlap with the royal blue DNA segment that I share with a Walsh/Roberts descendant. If it somehow overlapped with the light blue of the Meier/Goetz line, it would be an indication that I’d made some errors in assigning segments to ancestors. That green segment now helps me refine my understanding of my DNA in that region. When I only have the royal blue segment to consider, I know only that either John Frank Roberts or Katherine Walsh contributed that DNA. However, thanks to the additional data—that green segment—I know that the portion of the royal blue “Roberts/Walsh DNA” that overlaps with the green “Walsh/Hodgkinson DNA” in Figure 2 must have come from Katherine Walsh and not John Frank Roberts.

Now let’s see how this map can give me a starting point for understanding how I’m related to those unknown DNA matches, K.C., E.S., and K.M. As mentioned, E.T. is the only one of these DNA matches shown in Figure 1 to whom I know how I’m related; she’s my second cousin. So let’s start by focusing only on the segments of Chromosome 7 where I match her (Figure 3).

Since there’s a lot going on, visually, in the ancestral chromosome map shown in Figure 2, I’ve marked with stars those three segments where E.T. matches me, so it’s a little easier to focus on them (Figure 4).

As you can see in Figures 1 and 3, there’s a break between the segments of DNA that I share with E.T., represented as that gray region disrupting the purple regions, that runs from (approximately) position 32,356,335 to position 55,601,336. This represents DNA that E.T. and I do not share. This break is highlighted in the zoomed-in, side-by-side comparison of the chromosome map from 23&Me with the ancestral chromosome map from DNA Painter (Figure 5).

Notice that the first half of that gap corresponds to that 13 cM segment of DNA, colored in green, that I share with I.N., whose common ancestors with me were Robert Walsh and Elizabeth Hodgkinson. So, this tells me that in the first part of the gap region where I don’t share DNA with E.T., I inherited my DNA from the Walsh line. That’s important, because when we go back to Figure 1, the first part of that gap is where I share DNA with those unknown DNA matches, K.C., E.S., and K.M. So this tells me that it’s very likely that the common ancestors from which all of us descend are from the Walsh/Hodgkinson line (Figure 6).

Ta da!

At this point, you may be saying, “Who cares?!” But I think it’s incredibly cool and powerful that I can go from having no information at all about three of my DNA matches on 23&Me, to suddenly knowing that we must be related through some common ancestor of either Robert Walsh or Elizabeth Hodgkinson, even when I have no matches in the 23&Me database to cousins with whom Robert and Elizabeth are the most recent common ancestral couple. Thank you, DNA Painter!

Please note that DNA Painter also offers the option to paint segment data from unknown matches directly into one’s chromosome map, so I could have made this same observation about my relationship to K.C., E.S., and K.M. that way. However, my personal preference is to keep my chromosome map “clean” and not add segment data until I determine how the match is related to me. In the end, it doesn’t matter so much how we make these observations; the point is that we have the tools that make the observations possible. Going forward, I can write to these matches to see if they’ll give me further information about their family trees, I can look for clues in the family trees of additional shared matches, and I can play the long game and see what other matches are added to the test company databases over time that might shed some light on the situation. Ultimately, DNA matches can offer fantastic clues to help answer genealogical questions and identify unknown ancestors, so it’s worth taking the time to explore those matches.

© Julie Roberts Szczepankiewicz 2021