Ancestry.com’s new “Genetic Communities”

The ethnicity calculations used by ancestry.com and many other commercial DNA testers are toxic hokum. Wonderful marketing tools precisely because they appeal to the lizard back-brain in all of us, they gloss over the fact that there is no such thing as “ethnicity”. Peoples and differences and communities there are aplenty, but ahistorical essences that define groups as this ethnicity or that? Puh-lease.

Ancestry’s assertion that “the ethnicity estimate provides a distant picture of a customer’s genetic origins, perhaps hundreds or thousands of years ago”, is just plain wrong. What you get is a comparison of your test results with a (pretty paltry) reference panel, reasonably accurate to four generations, less accurate to five, sometimes useful to six and almost always worthless before then. A distant picture it is not. (For more on the flaws of this stuff, see UCL’s “Debunking Genetic Astrology“.)

138 on the Irish reference panel? There are more on any 16A Dublin bus.

So when ancestry.com announced “Genetic Communities” as a new feature of its DNA service, I was sceptical, to say the least.  Then I saw the map produced by their analysis of my own test, and I was blown away. None of my family tree is on ancestry, so it was produced purely by DNA analysis. And they hit the bulls-eye on the detailed North Connacht and Galway origins of all 16 of my 3 X great-grandparents.

That’s my mother’s people where all the communities overlap. 

How could they do this, working purely from the DNA? According to the white paper accompanying the new service, a “genetic community” is simply a group of people from more or less the same place who married each other over multiple generations, a nice, loose target, and much more sensible than “ethnicity”.  They arrived at their more-than-300 communities by detailed meta-analysis of the DNA matches in more than 2 million samples. Instead of just comparing my test with all the others and seeing to whom I was most related, they took all those to whom I was related and examined who they were related to. And so on and so on.

It was then possible with the aid of an algorithm for detecting densely connected sub-networks within large datasets (the “Louvain Method“, if you must know) to identify the groups most closely related to each other. They then went on to use their own online trees to associate these groups with particular locations, and then ran the whole process again and again to zero in on sub-sub-groups. The granularity of the results is truly extraordinary. In Ireland alone, there are (so far) seventeen different subgroups, ranging from East Donegal to West Cork to North Connacht to Connemara. Each group is presented alongside a series of good short histories explaining the history of the area over the past two centuries and its outmigrations to the US.

Ancestry has used the critical mass of its huge collection of DNA test results to provide a genuine, scientifically-grounded genetic atlas of the past 200 years, no less.

I still have my quibbles (to misquote Charlton Heston, “They’ll prise the quibbles from my cold, dead hands”.) There are unexplained sciency-looking variations in the size of the location circles on the map: what do they represent? Are they unique to each test analysis, or generic? How were the precise-looking boundaries of the communities arrived at? Above all, why is it not possible to see the data underlying the maps by clicking through?

But quibbles they remain. The whole thing is nothing short of deadly.

29 thoughts on “Ancestry.com’s new “Genetic Communities””

  1. Hi, John,

    I am researching my Fordes from Leitrim, and I was surprised for a few minutes that I did not have a genetic community there. But I sat back and and thought about my mother’s Sullivans and Sheas from Kerry. I have always known their stories, and we have always stayed in touch. They had lived in Kerry almost forever, and I had 172 autosomal matches to Kerry. I realized that it WAS brilliant. Not just DNA, but as people in real estate say, “location, location and location” And fir my clans, not just in Kerry, but where they chose to settle when they migrated. You went where already had family “pioneers” to house you and help you get a job- a “Soft landing” for an immigrant.

    I am still very interested in my MacConshnamha Fordes, about whom I knew very little, because my father would not discuss them. Must encourage more Leitrim Fordes to do an autosomal test.

    Pretty clever on Ancestry’s part, but I really see the value.

    Thanks for posting,

    Peggie Ford(e) Cosgrove
    New London CY USA

  2. Dear Mr. Grenham, thank you for clarifying the DNA analysis thing for me. I already know that from an ethnicity point of view I am truly Irish.( can’t tell a short story etc. Ha) I have inherited irish eyes and Irish temper, but to temper that I also inherited Irish compassion love of laughter and talk etc. We have traced my ancestry back to my Great grandfather who was born in Ireland (town unknown) in 1810 as was his wife . the unfortunate thing is that His name was Thomas James O’Neill born Ireland1810 nd died in Howard county USA ,. He and My Great Grandmother are buried in St. Mary of the Mills Cemetery in Laurel, Howard Co. Md. they lived in Savage, Maryland .I am now stuck not knowing where they arrived or the ship they arrived on or the date or why they left Ireland. I am told that there are over 2 million Thomas J. O’Neill’s listed on records in Ireland. I am 80 years old now and just hoped to know under what circumstances they left Ireland and how and why they arrived here in Maryland. I love being a member of Your Irish Heritage with Mike and Carina and really love you blog.
    Cordially.
    Mary O’Neill Leidner

    1. I too am having trouble with my Neil Neill O’NEILL family as they kept changing their name. My grandmother was Julia O’Neill born in Hamilton Scotland her fathers marriage cert has James Neill his birth cert has his father as John Neil. As far as I have been able to ascertain James Neill was born in Rathdrum in County Wicklow I don’t know if this is of any help to you.

  3. John, your blog pulled me in hook line and sinker as I thought the entire community presentation was bunk. Then your result shocked me. The Ancestry community for me is upper midlands. My great grandfather said he was from Cork. Right he left from Cork. I know my great grandparents and the only match of a Peter Edward Byrne birth with the known grandparents is in Wexford. I settled for that years ago. When I say the Ancestry community, I rejected it. Now with your comment I will broaden my research and trust the new lead. Thanks

  4. there is a member on ancestry.com redz1115 who seems to also be researching this person. you might want to contact through ancestry as tree is private.

    1. Ditto for my dad. Both his maternal grandparents (Willie Colbert and Eileen Houlihan) were born in Athea, Co. Limerick, and immigrated to the U.S. circa 1901. His genetic circle is also “Irish in Limerick and Kerry”. Mine, being one generation back, is “Irish in Southern Ireland” (95% likely). Or the whole Southern thing could also be due to my dad’s 3 immigrant paternal great-grandparents — 1 from Co. Offaly, 1 from Co. Kilkenny, and 1 from (likely) Co. Cork.

      Interesting, but nothing I didn’t already know….

  5. All the Genetic Communities showing up for the DNA tests on my account are correct. I do wonder why some aren’t showing up though. My mom for instance, has only Munster related communities. Yes, most of her known ancestors were from Cos. Cork and Kerry, but she also had Ulster Scots from Co. Donegal. No sign of them.

  6. If I have a paper trail showing 7 of my 2x great grandparents coming from Ireland, how come this isn’t reflected in my communities?

  7. Spot on John you nailed every point. The Genetic Community was very accurate the “ethnicity” report I would not even elevate to the lofty status of Hokum.

  8. It’s my understanding that the size of the location circles is based on the number of ancestral individuals who are tied to those locations based on the participants’ trees.

  9. Well my base Ancestry DNA has me 83% Irish 10% Europe West and 3% Great Britain. My mother is an O’Neill and there is Irish on both sides. My community came back as “Very Likely” French Settlers along the St. Lawrence River and “possible” Ulster Irish. It seems to have taken one possible line as more prominent than the other. Trying to figure it out.

    1. The irish Catholics immigrants to Canada mostly went to quebec because of being Catholic. And some awful coffin ship tales. They intermarried with the French and quite quickly lost their irish identities- . I have a friend from Quebec who barely admitted anything other but French and his name was Foley. So many of your Irish relations are mixed in there—

  10. I’m working on a one name study under a relatively informed premise that anyone with both Irish roots and with my surname or the variant Brunker are related due to numerous coincidences and proven migrations within the island.

    Until Y chromosomes are included in the mix Ancestry’s product is only useful to me for lighting up Dublin, Meath, Louth and Monaghan on a map and then, Carlow and Naas/Blessington for me maternally. Already got there the old fashioned way.

    I wonder also on their definition of Irish. The recent studies of travellers show the potential for subsets within subsets. A family with centuries of Mayo heritage versus one with centuries of North Dublin/Louth heritage are surely wildly different? Maybe there’s enough in common for them to be Irish then enough differences to position the circles provincially?

    I suppose one advantage of this product is that it will help people in “new countries”, and even some old ones, realise that we’re more interrelated as a species than they may think. Such a project will hopefully undermine extremists shouting nonsense based on non existent “purity”.

    In any case, congratulations on your confirmation. I’m sure this means that you can safely align your rugby support to Connaught.

    1. Someones genotype classified 100% east Asian can have mexican genetic communites because genotype doesn’t dictate culture/communities hence why ethnic and even geographical labels are problematic for genotypes.

      Genetic communities work because they take genetic clusters added with family trees that actually give a time and location then mix it with documented history.

      Your ancestors genetic pattern is concentrated in ireland, some were also culturally Irish but many were culturally English.

  11. HIt me straight on… MAYO and GALWAY. Knew the MAYO…heard rumblings about GALWAY. But that GALWAY person came via Lancashire… No paperwork yet discovered who it is. Based on what I have discovered – GALWAY person would either be my maternal Great Great grandfather… either a CONNOR or a CAUFIELD ( COFFEY).

    Way more fun than the annual Easter Egg Hunt.

  12. Thanks for your article.
    I am still confused because my DNA came back as 70% Irish and <1% Great Britain, however my genetic communities were 40% possibility of Southern England and 20% possibility of Ulster Irish.

    The Southern England makes perfect sense because so many from my family tree were from there. The Ulster Irish had me delving deeper and I realised there were the Doherty's originally from Donegal so that then made sense.

    However, how can I have 70% Irish and only the one 20% chance of a genetic community in Ireland, when I do know other family came from Louth, Limerick and possibly Offaly?

    Also how can I have 40% chance of Southern England when <1% on my DNA for Great Britain?

  13. John,
    I have results very similar to yours slightly shifted towards the Shannon and this reflects my Dunmore and Clonfert clusters with more recent NW Tipperary.
    As you say. They hit the bulls eye and nothing short of deadly.
    They have raised the bar for FTDNA, 23andme, Genographic and Living DNA.
    The results are based on the cohort of 775K samples described in the Nature paper. Their database now exceeds 3M samples and I have heard projections of 5M this year and 20M for 2020. So the level of granualarity can only improve.

  14. My genetic community result was very accurate and specific it placed me in the Cork Community. My father’s side going as far back as I can all came from rural North West Cork. Whereas my mother’s parents were born in Dublin but her paternal grandparents were from Kildare and Offaly and her maternal grandfather was a Best born in Dublin but Best is not originally an Irish name, her maternal grandmother was a Reilly from Dublin. However, Dublin like most big Cities attracts people from all parts of Ireland so more chance that the genetic community will be mixed up.

  15. Our results were spot-on for my brother and me since our mom was born in Milltown, Kerry and settled in Boston. Our DNA results were very likely to be Kerry in Ireland. Kerry was our only community and we can trace her maternal and paternal lines back to the early 1800’s there.

  16. Very interesting indeed. We don’t have the money to test a friend with Ancestry and am glad we did the Y67 at FTDNA which shows he is Clan Colla Null 425. So we know his ancestry is in the area of Counties Monaghan and Fermanagh. It would be interesting to see what the Ancestry autosomal GCs would show show for the Irish on his maternal side. We have a pretty solid answer with the Y-DNA. We have done the autosomal at FTDNA.

  17. I need info on both sides of my Irish Heratage please. My Gr. Great Grandfather was James Henry Drennan who was married to Maragret McCabe and on my Mothers side Thomas Stapleton who married Nora Snay (french we believe.) Please can you help me.

  18. My Genetic Communities also came up as expected. It’s 95% confident that I’m Connacht Irish, 60% confident that I’m in North Connacht and 20% confident that I’m in Galway. That matches up right since my grandmother was from Galway but at the same time not far from the Roscommon-Galway border. Now I just want to get a Y-DNA test done. I’ve done a test with Living DNA for the research project but since I’m not male, it won’t show up. My dad doesn’t like the idea of people having his DNA sample so that leaves my brother. The mitochondrial test is more interesting than useful.

  19. Just received dna results..i am ulster irish, East Donegal and Scot..I know my father was John Gannon born in Perthshire to James Gannon and Alice Morgan and know little beyond that. Can you help me with best way to locate aunts,uncles or first cousins.

  20. Thanks for your post about Ancestry.com’s DNA test and genetic communities. I was thoroughly confused when I got my results. On the one hand it showed my DNA as 54% Great Britain (which is defined as England, Scotland and Wales), with 0% Irish; while on the other hand I had but one genetic community – Ulster Irish. My maternal grandfather was Patrick John McCabe, who was most likely born in County Cavan or County Monaghan. While it’s clear that I’m a mutt, I couldn’t figure out how this mutt could have no Irish blood. Your post taught me to pay more attention to the genetic community, since it’s taken from a vastly larger sampling.

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