DNA matches/ethnicity headache

[Vicky the Viking]

More of a grumble than anything really. Had a very frustrating morning chasing my tail (not unusual!)

I have an unknown grandfather on one side of my tree, and a probable NPE for a great grandfather on the other side.

Ancestry has revised my ethnicity estimate to 22% Jewish, of Lithuanian/Russian/Polish origin. This can only have come from one of these two unknown men.

Because of the percentage, I am now favouring the grandfather, rather than GGF. They are from geographically separate areas so no chance of mixing up these two events.

22% is what you'd expect from a GF of Jewish origin, yes? (Although it's not outside the possibility of inheriting this much DNA from a GGF)

Anyway. MyHeritage has pulled up a DNA match for someone who is likely my half first cousin once removed. (There's a big age difference between myself & the match) This is my closest match and he does not match any contacts from my known grandparents.
However, he is (a) uncontactable, and (b) doesn't have much of a tree, just his father's name & dates & a mother's maiden name (she is probably still alive).


I have a name for my match, and approx age. The name is Anglicised, and fairly common. (No details as he's obviously still alive) So I started from scratch and tried to construct a tree for him.
Despite having his fathers name and date of death from his tree, I can't get any further!

There are 2 trees on Ancestry with the man I think is his father (same death date) but these show different sets of parents! Both are from Leeds. One seems to be of English origin, (2 generations baptised & married in C of E churches) and the other married in the synagogue (this is the tree I am favouring).

Any ideas how I can find out which is the correct set of parents? I am floundering around in the dark with no other close matches that can help.

I need to look at his grandfather on his mother's side too, but I can't even locate their marriage! Her surname is even more common (probably not Jewish) and there is nothing matching for the right dates in the right area. (Is it possible he has not got the correct details?)

[PhotoFamily]

Ancestry has revised my ethnicity estimate to 22% Jewish, of Lithuanian/Russian/Polish origin. This can only have come from one of these two unknown men.

Because of the percentage, I am now favouring the grandfather, rather than GGF. They are from geographically separate areas so no chance of mixing up these two events.


22% is what you'd expect from a GF of Jewish origin, yes? (Although it's not outside the possibility of inheriting this much DNA from a GGF)

ISOGG:

25%

1700.00

Grandparent/grandchild, aunt-or-uncle/niece-or-nephew, half-siblings

So, yes, grandparent appears likely. It is possible, however, that you have Jewish contributions from both of your unknowns, which could skew your percentages.

Anyway. MyHeritage has pulled up a DNA match for someone who is likely my half first cousin once removed. (There's a big age difference between myself & the match) This is my closest match and he does not match any contacts from my known grandparents.
However, he is (a) uncontactable, and (b) doesn't have much of a tree, just his father's name & dates & a mother's maiden name (she is probably still alive).

It is important to understand that there was a lot of endogamy in the Ashkenazim. It can make relationships appear closer (sometimes much closer) than they really are. I don't know if MH takes that into account with their relationship estimation, but I doubt it.

I have a name for my match, and approx age. The name is Anglicised, and fairly common. (No details as he's obviously still alive) So I started from scratch and tried to construct a tree for him.
Despite having his fathers name and date of death from his tree, I can't get any further!

There are 2 trees on Ancestry with the man I think is his father (same death date) but these show different sets of parents! Both are from Leeds. One seems to be of English origin, (2 generations baptised & married in C of E churches) and the other married in the synagogue (this is the tree I am favouring).

Any ideas how I can find out which is the correct set of parents? I am floundering around in the dark with no other close matches that can help.

I need to look at his grandfather on his mother's side too, but I can't even locate their marriage! Her surname is even more common (probably not Jewish) and there is nothing matching for the right dates in the right area. (Is it possible he has not got the correct details?)

Standard recommended procedure is to build the tree (in this case, two trees) and look for descendants that could have been the unknown parent - meaning they were in the right place at the right time at about the right age.

If you want to build trees on ancestry and invite volunteer assistants, that may help.

I hope you're "fishing all the ponds" - AncestryDNA, FamilyTreeDNA, 23andme, Gedmatch, LivingDNA. Free uploads to ftDNA, gedmatch and LivingDNA.

[Vicky the Viking]

My DNA is on Ancestry, MyHeritage, LivingDNA and Gedmatch. This is the closest match I have on any of them. This guy on MyHeritage does have an Ancestry account, but his DNA isn't on there. I've got thousands of Jewish matches on Ancestry and Gedmatch but none of them close enough to help. I don't have a DNA match to any trees with my putative GF's name (His grandfather's name appears in a couple of trees but none have a DNA match, though Ancestry don't tell you if the tree owner has tested unless you do match)

I can't get my head round this endogamy thing. On average I'm going to have 25% DNA.from each of my 4 grandparents. The fact that an endogamous population have more DNA in common with each other surely isn't going to affect that? I can see it makes relationships within that group seem closer, but surely it can't have much of an effect on an outside population?

[PhotoFamily]

I can't get my head round this endogamy thing. On average I'm going to have 25% DNA.from each of my 4 grandparents.

Right.
We are really talking about two different but related topics: separate "matching" from "ethnicity". Also separate "Grandparents contributions to that ethnicity" from "Matching"

I agree that your unknown grandfather was likely to be 100% Jewish, of Lithuanian/Russian/Polish origin. But what if, instead, he were 50 or 75%, and your unknown g'grandfather were, say 50% Jewish, of Lithuanian/Russian/Polish origin? If you have results from his children (or possibly some other descendants who are known not to have Jewish ancestry), you could eliminate that possibility.

The fact that an endogamous population have more DNA in common with each other surely isn't going to affect that? I can see it makes relationships within that group seem closer, but surely it can't have much of an effect on an outside population?

It can affect the calculation of relationship. Because they intermarried for generations, their genetics are much more homogeneous. More people have the same combinations of SNPs.

This explanation is undoubtedly better than mine:

https://isogg.org/wiki/Endogamy

I'm not saying that your best match is not as close as he appears from quantity shared - I'm just saying you need to keep another possibility in mind.

I assisted with a woman whose father was unknown. Her ethnicity showed that she was about 1/4 Ashkenazim. She appeared to have wonderful Jewish matches, but after working on the close matches for about a year, had to back off because they would go nowhere. Finally, an even better good match appeared, and she was able to build a tree out and find her unknown father.

[PhotoFamily]

One of the problems with MH and AncestryDNA - they don't use/give X-Chrom matching. While it is of limited usage, it can provide direction on occasion. For instance, if you had an X match with your close match on MH, you would know that it came from his mother's line, since men receive their one X chromosome from their mothers.

Sigh. I had heard that MH was going to start reporting X chrom segments, but haven't seen a result from that.