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General => Ancestral Family Tree DNA Testing => Topic started by: Petros on Tuesday 12 August 25 12:18 BST (UK)
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I have a curious cluster of 6 matches on Ancestry from 13 to 28 cM who all share their descent from James Edward BARRINEAU (1822-1885) and Susan McCrea BROWN (1831-1857) with their ancestors also apparently from South Carolina. However, I have no US ancestry and am unaware of any members of my ancestral families arriving in the US before the 1850s.
Any suggestions for how an early event might yield such matches, especially at 27 and 28 cM. Those two are relatively distant to each other
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Are you sure that you don't mean that you have no US ancestry, that you know of? DNA doesn't lie.
Zaph
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I have no US ancestry that I know of and can trace most of my ancestral lines back to ca 1700, some early with a couple just to around 1800. All my known ancestors are from the Southern half of England.
These DNA matches are to my paternal line which is confined to a small number of counties
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As I found out recently, you only need one 15 minute illicit relationship that you don't know about, 100-odd years ago and you can have a lot of DNA matches who will be very difficult to place on your tree.
Zaph
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My Wife is a Facebook friend to a distant 8cM Half Cousin of hers in the USA whose family emigrated to the USA.
On the same family line another USA Distant 24cM Cousin had a totally different ancestor emigrate to the USA.
It was only via DNA that we found them and made contact.
We were aware that yet another three different members of the same family who also emigrated to the USA.
Believe the DNA.
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Biggles, did you mean just eight centiMorgans for a half cousin? That is unbelievably low.
Zaph
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Hi,
I would say certainly possible, I have a 28cM match with MRCA born 1773 and some further back 10 cM MRCA 1719. You only have to have one ancestor who went off to the States early to get this sort of cluster.
Pedigree collapse can also make people seem closer than they are.
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I have several matches who claim I'm not related as they are US based & have no UK connections but they don't consider siblings of their pedigree line unless they are still alive. They fly straight back through a generation of 10 children but only include their ancestor and are largely clueless to their family as a result.
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Biggles, did you mean just eight centiMorgans for a half cousin? That is unbelievably low.
Zaph
His is a DISTANT Half Cousin, quote what I posted “distant Half Cousin”, H4C3R to be exact and outside DNA Painter’s reporting and at a level we would not generally follow up on.
His 4GGM was already in my Wife’s family tree as was her Husband.
No record of what happened to them in UK records or via passenger records but via the 8cM match’s tree we found that they had emigrated to the USA.
We checked his lineage to be correct and made contact.
We often search Trees for specific family names and in this case he was just one of many and it was only his tree which was of sufficient size that we followed up on him.
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I have a curious cluster of 6 matches on Ancestry from 13 to 28 cM who all share their descent from James Edward BARRINEAU (1822-1885) and Susan McCrea BROWN (1831-1857) with their ancestors also apparently from South Carolina.
Have a read through this: https://www.rootschat.com/forum/index.php?topic=891402.0
What is the largest cM match that is in this cluster? 28cM? Is there a larger match in the cluster you don't know how you are related to.
As outlined in the above post, when you have clusters that don't have any overlaps with larger cM matches, it's likely because they are more distant matches. You're talking more like 7th cousins, so ancestors in the window 1730. At this point the chance of inheriting that specific piece of DNA unbroken is quite small. So it's statistically unlikely to match any, of say, 40 matches that you are related to in the window 1775-.
I have mentioned this before, particularly if the tests are from someone from my grandparents generation, first 1/4 of the 20th C. I've noticed that there are lots clusters, I think all of which don't include matches that are above 30cM - I think 28cM is the biggest. And they all go back to the old US south, mostly to the Carolinas. And I don't think they have any British matches, or very very few. These clusters tend to be huge. I have one that has about 500 shared matches (so far as I can tell). Each match usually has about 100 shared matches.
I've come across numerous of these and don't know what to make of them. One thing I wonder is if they are false positives, where timber has not stripped out some DNA and the result is these huge IBS clusters.
One thing that makes me think that they are real is that I have two tests from mutal 2nd cousins on my grandmother's generational level, and they both have this same massive cluster from the Carolinas. If it was IBS, it would not be likely to show up for both.
I have found, maybe 50-60 matches in that cluster that have common ancestors - not all the same common ancestors. But most of them had the surname Mullinyeux across multiple generations. And the two tests mentioned do have Mollinyeux ancestry from Cambridgeshire. No US ancestry known.
But generally speaking, when I find those clusters it's just a complete mystery, with no obvious surname link.
One thing that makes them suspicious is 1) the size; and 2) that they always seem to be from the old south and not, say, Massachusetts, Maine or New York. The size of them suggests it could be an issue with tinder.
Going back to what I initially mention about these clusters with smaller maximum cM - my rule, assuming the test subject is born in the window 1950, that if the maximum cM in a cluster is X, the MRCAs are in the window Y:
X => Y
< 20cM => 1700
30cM => 1730
35cM => 1760
40cM => 1775-1800
That's a general rule. It could be something different. The reason I have it is I group clusters by location ans assign them an approx window for MRCAs. This lets me guess where they may link in to a tree. See attachment. You can place them where they better look like they fit in and then look for possible marriages between the clusters.
Also worth keeping in mind is that when you find MRCAs in the matches of these clusters with a smaller max. cM, is that there can be multiple generations between the MRCAs in your matches and the overall MRCAs. As it just happens that a few people inherited a big chunk from one ancestor and it stays in a few descendants to a level that can be useful in aDNA.
So in your example, you have MRCAs in the tests in the window 1830, but if the biggest match is 28cM, your MRCA (assuming its not a false positive) is more likely to be in the window 1730.
It's also worth considering that the genealogical record from the old south is not good. I'm not sure what sources they use, but I don't think there are BMDs, or few. Many southern trees are highly suspect. In going through many on Ancestry you can see many variations. So it's just too much of a mess to really be worth putting time into. And how would you know if there was an immigrant ancestor to the Carolinas? Unlikely there is a source. I believe many people were transported to the south up to about 1776. So there would be a lot of possible links. But it's most likely any amateur trees botch in the nearest possible match in the Americas, rather than the immigrant ancestor, for whom there may be no source of the immigration.
I do have one of these clusters where there are MRCAs in the matches with a surname from my ancestry. Maybe that's the link, maybe it's not.
Generally speaking, US matches where the link is prior 1800 are a wild goose chase.
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I have found, maybe 50-60 matches in that cluster that have common ancestors - not all the same common ancestors. But most of them had the surname Mullinyeux across multiple generations. And the two tests mentioned do have Mollinyeux ancestry from Cambridgeshire. No US ancestry known.
But generally speaking, when I find those clusters it's just a complete mystery, with no obvious surname link.
One thing that makes them suspicious is 1) the size; and 2) that they always seem to be from the old south and not, say, Massachusetts, Maine or New York. The size of them suggests it could be an issue with tinder.
Hi, 4b2 and OP.
I think this is exactly what you would expect with pedigree collapse. As far as I understand from there documents, Ancestry assume that no people are related for Tinder. Whilst this may be true for the last 100 years or so in the USA it’s not pretty much everywhere else.
The south was relatively sparsely populated like much of rural USA so much like Europe if your family was in an area early, the the chances of pedigree collapse are much higher, so you will have 20cM matches who are closer to 10cM matches in time. You can see you are related, but it is before records began or before the 1600’s even. So it is not USA ancestry so much as USA descent, someone emigrated a long time ago and you are seeing that signature in the resulting US population.
Happy Hunting
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I think this is exactly what you would expect with pedigree collapse...
The south was relatively sparsely populated like much of rural USA so much like Europe if your family was in an area early, the the chances of pedigree collapse are much higher, so you will have 20cM matches who are closer to 10cM matches in time. You can see you are related, but it is before records began or before the 1600’s even. So it is not USA ancestry so much as USA descent, someone emigrated a long time ago and you are seeing that signature in the resulting US population.
Happy Hunting
Your suggestion is that there is a relatively small pool of ancestors in the south/Carolinas, that lead to a greater representation of the footprints of certain ancestors in the gene pool, and thus these matches could be more distant?
What are your thoughts on when false positives creep into Ancestry? At what cM level. a quick Grok give >= 15cM should be about 0% false positives.
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Hi 4b2
Thanks for the comments and insights on the issues. It is likely to remain a puzzle to me as I don't know which of the South Carolina couple born in the 1820s is the connection nor do I have any insight on who from a number of my ancestral lines disappeared from England to the US in the 1700s.
I have found a couple of other large clusters of matches in the US but in those I can trace the connections. One goes back to a 4 x GGF whose grandson emigrated to Canada in the 1840s. This yields a number of relatively high matches including a 5C2R who is a 44 cM match! Another cluster also went via CAnada to Salt Lake City