DNA Testing Advice | Why Test Older Generations

Sunny Morton

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The best DNA testing advice includes testing relatives in the oldest living generation. Why? This short case study shows why you should be inviting your older relatives to take DNA tests (and share their results with you).

When you start getting DNA testing advice, you’re bound to hear this one: be sure to test the oldest generation. Why? After all, you’re most curious about YOUR heritage. If you test an older relative from one side of the family, their results will only include tell you about that branch of the family.

That is true. And yet, when you start really digging into DNA test results for the purposes of building your family tree or getting deeper insights into your heritage, you’ll want their results. Because their results only belong to one side of your tree, they can help you assign parts of your genetic heritage to their lines. The next generations back are that much closer to the past. Their ethnicity results can reveal genetic ties to historical communities that may have faded from your generation. Their connections to your shared DNA matches are often closer, which can lead to much better insights about how you are all related.

Here’s how it looks with myself, my dad and his mother at AncestryDNA.

Ethnicity Inheritance and Sideview

The newest tool on AncestryDNA sorts our DNA into the halves inherited by each parent, which can themselves be assigned some ethnicity percentages. (Read more on that here.) Because my grandmother has tested, I now have this breakdown for HER parents. The “You” in the chart below is my grandma: the parents shown are my great grandparents. That’s a pretty good reach into the past for an ethnicity estimate, don’t you think?

Comparing AncestryDNA Ethnicity and Communities

But let’s dig deeper. My Swedish heritage comes almost exclusively (as far as I can tell) from this grandmother, whose own maternal grandmother Elvina was born in Denmark to Swedish migrants. Predictably, and as shown below, that ethnicity shows up the most in my grandma (47%); a little less in my dad (31%) and even less in me (23%).


What do those ethnicity results really mean? Get our free guide to DNA ethnicity.

Get Free DNA Ethnicity Guide


If I didn’t know already where my Sweden/Denmark ethnicity results came from, these climbing percentages would point me clearly up my grandmother’s branch of my tree. In this specific example, though, the the ethnicity category doesn’t currently distinguish between Sweden and Denmark. If my paper trail only went as far as my Danish-born 2x great grandmother Elvina, I would likely (and wrongly) conclude that she was Danish.

That’s why I appreciate my grandma’s AncestryDNA Communities. These point to more specific geographic places of origin than ethnicity results because they are based on genetic similarities to people who, as a group, share origins in specific places. But you have to test someone whose ties to a specific place are recent enough to show it in their genes. Communities only work at a relatively close range. I don’t have any Swedish or Danish Communities, and neither does my father. But, as the granddaughter of a (Danish-born) Swede, HIS mother DOES have relevant Communities. Southern Sweden is the largest; it rings the Nordöstra Skåne & Västra Blekinge region, which itself rings the even more specific location of Älmhult.

According to our paper trail, Elvina’s father was born within that middle ring–and her mother was born within the smallest ring, a few kilometers north of Älmhult. My grandmother’s AncestryDNA Communities practically form a bullseye over her great grandparents’ birthplaces! If I didn’t know about their birthplaces from genealogical research, these Communities would point the way. And even if records didn’t lead anywhere, the interactive timeline and brief narrative history (which includes why people migrated away from Sweden) puts my ancestors’ story in historical context.

Now, it’s true that my grandma’s Ancestry’s Communities (or MyHeritage’s Genetic Groups or 23andMe’s Recent Ancestor Locations) could be wrong. That needs to be said. But in many cases, they add one more compelling source to your overall research findings. This one verifies what we’d already documented in the paper trail.

What about DNA matches?

In testing my grandmother, and having full access to her results (thank you, grandma!), I also have access to her list of DNA matches. And guess what? Our match lists are not the same.

Because I’m genetically downstream of my grandma, you’d expect that if she’s related to someone, then so am I. But here are two important principles about the way DNA matching works:

1) DISTANCE MATTERS. With every generation, the genetic distance between matches widens. Only 90% of actual third cousins share DNA, and by the time you get to fourth cousins, you’ll only share DNA with them about half the time. This means my grandma will likely have genetic connections that have faded by my generation. Diahan Southard explains it below:


2) CLOSENESS MATTERS, TOO. When my grandma is more closely related to our shared matches than I am (which is true for almost all of them), it can be easier to identify those shared matches in relation to HER. Below, I show an obvious example. It’s a match I didn’t immediately recognize because his username is not his full name. I have 15 possible genetic relationships with this match (if I click “See More” I’ll see them all). But on my grandma’s match list the answer is easy. There’s only one possible relationship (usually) at such close range. It’s her brother.

So, maybe you HAVE taken a DNA test. But you want to know more. If you have older relatives who might be willing to test, invite them to test. Invite your parents and their siblings. Invite your grandparents and their siblings. Anyone further up the tree from you who might have a better view of the past from the top.

Which DNA test should I have them take?

Good question. If you are happy with where you tested and the tools your testing company has to offer, invite them to test with the same company. Even so, you might consider comparing all the DNA testing companies–and sending in your own sample along with your relative’s to a testing company that has the tools and numbers of testers you want.

Compare Best DNA Tests


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