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General => Ancestral Family Tree DNA Testing => Topic started by: M_ONeill on Sunday 23 July 23 03:53 BST (UK)
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A few days ago I got my results back from AncestryDNA and one small thing that surprised me was that doing the origin trick showed me that I have one tiny segment (0.05%) that Ancestry has labelled internally as 'Jewish Peoples of Europe', though shows up as 'unassigned' in my official results due to falling below the percentage threshold.
Now, I'm fully aware that such an incredibly miniscule segment could very well be noise, or a mis-reading, but as there's some amount of circumstantial evidence in my own research (and that of other people I'm working with), that suggests it might be legitimate, I'm at least looking into the possibility.
Just as an example, I have one match (12cm) whose tree contains an English family line with a distinct surname I've been researching quite extensively in Ireland. Their tree goes back to an individual b. c1608 who they claim adopted the surname and was originally a member of the Sephardic 'Crypto-Jewish' community of converso emigrants from Portugal (the strong Portuguese connection is another thing of note in the research regarding the Irish family). They sadly don't have an attached source for this claim, so I don't know if it's a family story or an attested piece of history. I'll be contacting said match in a couple of days to see if they're up for sharing info.
When looking at where I match with this person in a chromosome browser, they don't share this particular segment of unassigned DNA in question - but someone who is a shared match between the two of us does. Going through their shared matches finds more people who share the same segment; I have at least ten after a day's searching. Said segments often even sharing the same start and end points. GEDmatch usually puts the estimated most recent common ancestor about seven generations out.
Now as someone new to diving this deeply into DNA I want to ask: am I potentially on to something meaningful here, or is it a wild goose chase? Is finding so many people with the same segment of shared DNA something of note, or with such a small segment could it just be random chance at work?
Thanks in advance for your answers!
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I am on my phone, so can't send a lengthy reply. Someone else will no doubt help. A 12cM match on its own can also have a relatively high chance of being false. Only at about 20cM or more can you reliably consider match lengths to be 100% accurate.
If you and the 12cM match have shared matches at higher match lengths then there may be something in it. You would need to investigate and establish those relationships with documented paper based research to be certain.
Treat ethnicity estimates with a large dose of scepticism. They are the least reliable aspect of DNA testing. I don't use them for research and I wouldn't even consider looking into an ethnicity estimate of only a couple of percent or less.
As an example of how autosomal matches become increasingly more likely to be identical by chance at lower match lengths, I have experimented with reducing the lowest match length to 3cM on GEDmatch and picking other tests for comparison at random. I found a "match" to every single individual that I ran a comparison against, often across several segments at small match lengths.
I have to say that I wouldn't start my DNA research by looking at lower matches. I would start with the highest, plotting them in your tree, and work your way down to the lower ones if necessary. I only include shorter matches if I need them to corroborate my paper research in the absence of, or in addition to longer matches.
Before starting on investigating DNA matches, if you haven't done it already, I would also recommend researching your tree so that it is as deep and wide as possible. E.g. don't just restrict it to your direct ancestral lines, but also research the siblings of your ancestors at each generation, their marriages and children, and bring each of those forward to the present as far as you can. It will help tremendously with identifying matches, as you will often recognise the name of your match - often totally unrelated to your direct family - or the name of one of their ancestors within a few generations back.
Good luck with your research.
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Totally agree with Phil.
If you do your research on how the likes of Ancestry calculates Ethnicity you should then deduce what is presented is an Estimate and very Questionable given the small database
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Given it's Ireland and such a tale, it is likely to be via word of mouth. Useful, but these details can get twisted. As an example, I was told a bit of genealogical details of my family when I was young. I made the diligence of recording this when I was in my teens. If I was today recording this information, I would have noted that a certain gg-grandfather died when falling into a mill. But it was actually my other gg-grandfather. As other tales, my grandmother told me that us her parents were Armenian refugees from the genocide, which was not true. While another family member had it that a certain family lived at a certain home in the lat 17th century, which turned out to be true.
If you can find a direct male descendant of this family, you could get them y tested ($89). That should probably give enough details to show if they are likely Jewish, but there is also the issue of infidelity. If you consider your seven generation tree of 128 ancestors, the chances are that about 1-5 are born of infidelity.
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Thanks for the replies, all! I agree entirely regarding not starting off with smaller DNA matches; I should note that this is most certainly a sidebar to my work on the main portion of my tree. It's only because it possibly intersects with another line of more solid research that I'm looking into it at all.
Looking further into my 12cM Ancestry match (we'll call him 'A'), GEDmatch puts our match slightly higher, but not by much: 13.7cM. I have 8 shared GED matches with A. The highest of these matches is a kit we'll call 'B'. The one-to-one tool shows me and B share 17.8cM, with A and B sharing 38.7cM, largest segment 28.7. There appear to be no matching segments that overlap between all three of us, however.
Back on Ancestry, looking through my matches, I have found two other people who appear to descend from the same family line as A. These three people all claim two shared ancestors born in the 1720s, but from there on back it gets a little messy. The trees don't agree on who the husband's father was. A claims one name, linking back to the potential Sephardic ancestor in their tree, but looking at the ages in said tree, the named ancestor would have been 14 when they fathered the son. The other matches claim another name, from another part of England, but going by the ages in that tree, this man would have been 75(!) when he fathered the son!
Looking at the above, I'm starting to think that my connection to A isn't a false match - but I think I'm going to need to do some parallel research on the trees involved before any conclusions are drawn!
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Ah, 4b2, we crossed replies!
It's funny that you should mention the Y-DNA test, as it was the results of a very distant cousin (confirmed through research and DNA matches) of mine's Y-DNA test that kicked off the research in question. Namely with two cases of this rather specific surname appearing amid a block of the other, more expected surnames from a common ancestor.
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Looking at the above, I'm starting to think that my connection to A isn't a false match - but I think I'm going to need to do some parallel research on the trees involved before any conclusions are drawn!
If a low cM match has shared matches with other people from a line, I consider it highly likely it's not a false match. If a low cM match has no shared matches, I don't pay much attention to it.
It would be good if Ancestry lowered or removed the 20cM limit for shared matches.
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If a low cM match has shared matches with other people from a line, I consider it highly likely it's not a false match. If a low cM match has no shared matches, I don't pay much attention to it.
It would be good if Ancestry lowered or removed the 20cM limit for shared matches.
Indeed, since they started giving new matches as a group I seem to get large numbers of new matches in the 10-20 cM range who have no shared matches, and generally no trees of any significance
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A few days ago I got my results back from AncestryDNA and one small thing that surprised me was that doing the origin trick showed me that I have one tiny segment (0.05%) that Ancestry has labelled internally as 'Jewish Peoples of Europe', though shows up as 'unassigned' in my official results due to falling below the percentage threshold.
Jewish Peoples of Europe would usually refer to Ashkenazi Jews. Sephardic Jews have a much more complicated DNA makeup and are more genetically diverse, having more often inbred with local populations where they have found themselves, whereas Ashkenazi Jews are a very homogenous population that have intermarried over many many centuries mainly in central and eastern Europe. So even if that very small segment were accurate, it would more likely refer to a distant Ashkenazi Jewish ancestor rather than a Sephardic one. Sephardic Jews will often show large proportions of North African, Italian, Middle Eastern and Balkan DNA, with smaller amounts of West Asian or Sub Saharan African.
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The chromosome browser cut off points for matches vary btween sites but are quite low so if the match isn't showing in chromo browser results it must be a very small segment, possibly from an ancestor predating traditional genealogy records or as a result of ancestors from an endogamous population. There are what are known as 'pile up' regions where hundreds of false matches can share a segment/segments totalling around 7-8cM and they are reported as dna matches in results.
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Thanks for the replies, all!
Jewish Peoples of Europe would usually refer to Ashkenazi Jews. Sephardic Jews have a much more complicated DNA makeup and are more genetically diverse, having more often inbred with local populations where they have found themselves, whereas Ashkenazi Jews are a very homogenous population that have intermarried over many many centuries mainly in central and eastern Europe. So even if that very small segment were accurate, it would more likely refer to a distant Ashkenazi Jewish ancestor rather than a Sephardic one. Sephardic Jews will often show large proportions of North African, Italian, Middle Eastern and Balkan DNA, with smaller amounts of West Asian or Sub Saharan African.
That's a useful thing to know, thanks, Melba! I had assumed that, going by the rather vague name, they were trying to cover a very broad umbrella of European Jewish populations. As mentioned in my last post, the possible Sephardic link suggested by my match with 'A' is looking a bit more wobbly (though not necessarily completely 'disproven', either) due to disagreement over particular ancestors among my matches sharing that line. I've reached out to A to see what evidence if any they have for the link to that particular family branch.
I have done a more general search for (non DNA-matched) trees with A's claimed Sephardic ancestor, and there are a lot of trees with the same family line in it (an Ancestry search kicks out almost 500 of them), as well as exactly the same name change.
The number of people with this identical family line is somewhat more than I would usually expect from people simply copying and pasting trees - but then again these trees (unlike A's) also go back couple of generations a fairly famous Rabbi from the Portuguese Sephardic community in Amsterdam of the 17th century. So it could be either a genuine, well researched genealogy shared by a lot of people, or a case of 'borrowed glory' from a famous name, I've yet to decide an opinion on that question.
Possibly entirely coincidental, but I do happen to match with another person who has an ancestor in England of around the same time period and with the same Portuguese/Sephardic surname, though using a different English last name as an alias. This match and I share a very small amount of cMs, so I'm at the moment not looking into that too seriously. Just an interesting side-note that I happen to have two matches with two aliased people of the same surname (and I would guess the same religion, going by the combination of alias, Portuguese Sephardic surname, and the usage of the names Isaac and Abraham).
The chromosome browser cut off points for matches vary btween sites but are quite low so if the match isn't showing in chromo browser results it must be a very small segment, possibly from an ancestor predating traditional genealogy records or as a result of ancestors from an endogamous population. There are what are known as 'pile up' regions where hundreds of false matches can share a segment/segments totalling around 7-8cM and they are reported as dna matches in results.
I'm pretty sure I can see this segment of DNA in Ancestry's chromosome viewer (see attached image), as it's the only piece of unassigned DNA I can see anywhere on my chromosomes. It's on a part of my paternal Chromosome 1.
Annoyingly, Ancestry doesn't seem to have anyway to find out precisely where this segment is in terms of start and end points, so I can't look at GEDmatches or DNA Painter to compare it to other specific tests.
You're of course right that it could be a pile-up, though I think it at least doesn't appear in any of the common pile-up regions shown on DNA painter.
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Thanks for the replies, all!
Jewish Peoples of Europe would usually refer to Ashkenazi Jews. Sephardic Jews have a much more complicated DNA makeup and are more genetically diverse, having more often inbred with local populations where they have found themselves, whereas Ashkenazi Jews are a very homogenous population that have intermarried over many many centuries mainly in central and eastern Europe. So even if that very small segment were accurate, it would more likely refer to a distant Ashkenazi Jewish ancestor rather than a Sephardic one. Sephardic Jews will often show large proportions of North African, Italian, Middle Eastern and Balkan DNA, with smaller amounts of West Asian or Sub Saharan African.
That's a useful thing to know, thanks, Melba! I had assumed that, going by the rather vague name, they were trying to cover a very broad umbrella of European Jewish populations. As mentioned in my last post, the possible Sephardic link suggested by my match with 'A' is looking a bit more wobbly (though not necessarily completely 'disproven', either) due to disagreement over particular ancestors among my matches sharing that line. I've reached out to A to see what evidence if any they have for the link to that particular family branch.
I have done a more general search for (non DNA-matched) trees with A's claimed Sephardic ancestor, and there are a lot of trees with the same family line in it (an Ancestry search kicks out almost 500 of them), as well as exactly the same name change.
The number of people with this identical family line is somewhat more than I would usually expect from people simply copying and pasting trees - but then again these trees (unlike A's) also go back couple of generations a fairly famous Rabbi from the Portuguese Sephardic community in Amsterdam of the 17th century. So it could be either a genuine, well researched genealogy shared by a lot of people, or a case of 'borrowed glory' from a famous name, I've yet to decide an opinion on that question.
If you are looking at this one ancestor in 1608, the reality is you have no genetic material from that person in your genes whatsoever. When you go back that far, say about 14 generations, without pedigree collapse you would have 16,384 ancestors, lets make it 15000 expecting some pedigree collapse. Take a look at this blog post:
https://gcbias.org/2013/11/11/how-does-your-number-of-genetic-ancestors-grow-back-over-time/
In this, they have various charts, including one that shows how your numbers of ancestors grows each generation:
"Your number of genealogical ancestors, in generation k, is growing exponentially (I cropped the figure as otherwise it looks silly). Your number of genetic ancestors at first grows as quickly as your number of genealogical ancestors, as it is very likely that an ancestor a few generations back is also a genetic ancestor. After a few more generations your genetic number of genetic ancestors begins to slow down its rate of growth, as while the number of genealogical ancestors is growing rapidly fewer and fewer of them are genetic ancestors. "
To take some figures from their chart (ignoring pedigree collapse):
Up to the 6th generation back, you inherit at least some DNA from all your ancestors.
But from the 7th generation, you inherit no DNA from 4.7% of your ancestors i.e. about 6/128 ancestors
From the 8th generation, you inherit no DNA from 14% of your ancestors i.e. about 36/256 ancestors
From the 9th generation, you inherit no DNA from 32% of your ancestors i.e. about 164/512 ancestors
From the 10th generation, you inherit no DNA from 54% of your ancestors i.e. about 553/1024 ancestors
And in the 11th generation, you inherit no DNA from 71% of your ancestors i.e. about 1454/2048 ancestors
So, you can see, by the 14th generation, you will have inherited no DNA from most of your genealogical ancestors.
Of course, if you think you have some male line descendants of that immigrant ancestor living, you could Y-DNA test a few initially using a cheaper method, such as 23andme. If that throws up an unusual result, you could then get a full sequence at FTDNA.