Why do I not share the same Genetic Communities with my known relatives?
Q I’ve included the ethnicity and Genetic Communities from Ancestry’s ‘DNA Compare’ tool so that you can see what I’d expected to find on the DNA communities comparison. The first three matches are related to me via a set of Irish great grandparents as they are descended from siblings of my paternal grandfather and the last two are much closer matches who are related to me via my paternal grandfather.
We all share a reasonable percentage of Irish ethnicity but none of them share any of the same Irish Genetic Communities with me. Why would that be the case when we all descend from the same Irish ancestors?
Judith Irwin
A I suspect your situation is a consequence of the vagaries of autosomal DNA inheritance combined with the way the algorithms behind ‘Genetic Communities’ work.
All of the people you are comparing against have Irish ethnicity percentage-wise (some quite high) so it’s likely they have been included in some Irish Genetic Communities but possibly just not exactly the same ones as you and that’s fairly common. It’s also possible they haven’t ended up in any of them. Do note that there is an * in front of Yvonne’s and Denise’s names which means they are only sharing the ethnicities/communities that you have in common and you can’t see any communities they have that you don’t as you can with David, Hazel and Nick. Make sure you scroll down the entire ‘DNA communities’ comparison page to check none of those three have ticks in other Irish communities further down.
The bottom line is that we all inherit a different mix of DNA from our ancestors, we all end up with a different mix of matches and, as a result, the algorithm will pick up some different communities for our relatives. In the example on page 67, I have the same Donegal lines as my cousins but I just haven’t ended up in those communities. I may yet be placed in them via a future update. This is one of the reasons why testing additional relatives can be so useful; it gives us more of our ancestors’ DNA to work with and allows us to see the bigger picture. Across all of my paternal tests, I likely have all of the Genetic Communities pertaining to my Irish ancestry but if I look solely at my own communities, I will see a much smaller proportion of them. I share many identified matches on sthe correct Irish lines with the relatives in my examples – we all descend from the same ancestors from the same areas of Ireland but only some of us have been placed in the corresponding communities. I don’t think there’s anything wrong or unusual in what you’re seeing but the key is always in the match list and, especially, the shared matches. Look at your shared matches with each of these identified relatives and make sure they are correctly matching other identified relatives on the same lines. If they are, then all is fine and it is just that Ancestry’s algorithm is not placing them in the same communities as you. Also if you have been invited to any of their results, swap them over to being the base person for the comparison and compare them to their shared matches as I did with my cousin. ML