Researching a Trace Ancestry/Ethnicity?

[Glen in Tinsel Kni]

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.

[M_ONeill]

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.

[melba_schmelba]

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.