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Thread: DNA Relatives Reliability

  1. #1
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    DNA Relatives Reliability

    Just wondering how reliable the 23andme DNA relatives could be. I have many DNA relatives from countries I don't have any known ancestry from. For example, I have 41 relatives from Italy (9 of those having 4 Italian grandparents, the rest mixed with American mostly) and 20 in Greece of which 10 are full Greek. I also have a large amount of Americans who are mostly Northern European of which I have no idea how they could be related. In addition, there's some full blooded Germans, Irish, and Hungarians. The only European ancestry I am aware of is from Albania and I only have a few Albanian matches. I am just confused how I'm related to full blooded North Europeans and if it might be a mistake or I actually do have ancestry from those areas?
    78.1% Lebanese (Lebanon) + 21.9% Kosovar (Kosovo) @ 3.3

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    Good question, one that can also be extended to include the GEDmatch 'One-to-many matches' tool.

    What is the minimum size of matching segment that qualifies as a bonafide DNA relative?

    The default value in GEDmatch is 7cM, however, this is primarily in place to make the calculation less CPU-intensive.

    Is it possible that below a certain threshold, the matching segment could be pure coincidence, or that it is such a distant relative that it is insignificant from a genealogical perspective?

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    Quote Originally Posted by KingofPhoenicia001 View Post
    Just wondering how reliable the 23andme DNA relatives could be. I have many DNA relatives from countries I don't have any known ancestry from. For example, I have 41 relatives from Italy (9 of those having 4 Italian grandparents, the rest mixed with American mostly) and 20 in Greece of which 10 are full Greek. I also have a large amount of Americans who are mostly Northern European of which I have no idea how they could be related. In addition, there's some full blooded Germans, Irish, and Hungarians. The only European ancestry I am aware of is from Albania and I only have a few Albanian matches. I am just confused how I'm related to full blooded North Europeans and if it might be a mistake or I actually do have ancestry from those areas?
    Your matches from Italy, and Greece likely have Albanian ancestry. My mother was half Italian/Albanian. We also get matches to some who have ancestry from Greece (4 grandparent too). One of them once told me that the Albanians had large families, and in the Peloponnese. Funny enough that is one of the regions that my mother has a likely match to in the new beta opt in reports.
    Maternal Grandfather's Y Line: J-ZS1711
    Paternal Grandmother’s mtDNA: U5a1

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    Quote Originally Posted by KingofPhoenicia001 View Post
    Just wondering how reliable the 23andme DNA relatives could be. I have many DNA relatives from countries I don't have any known ancestry from. For example, I have 41 relatives from Italy (9 of those having 4 Italian grandparents, the rest mixed with American mostly) and 20 in Greece of which 10 are full Greek. I also have a large amount of Americans who are mostly Northern European of which I have no idea how they could be related. In addition, there's some full blooded Germans, Irish, and Hungarians. The only European ancestry I am aware of is from Albania and I only have a few Albanian matches. I am just confused how I'm related to full blooded North Europeans and if it might be a mistake or I actually do have ancestry from those areas?
    On the topic of unexpected matches, I get plenty of matches with 100% NW European or Ashkenazi ancestry, which I am always skeptical about.
    However, I was contacted by one of the DNA relatives from my region who was interested to know if I had a German ancestor too.

    He was looking for descendants on the line of his German great-grandmother.
    I don't know if Germans usually get 100% NW Euro, in which case he should have inherited roughly 12.5%. He is getting 7.6% instead, of which most is Broad and the rest falls under British Isles and Scandinavian. Then he also has 5% under Broad Euro, so maybe it just can't be identified yet.
    I suppose he contacted me, since I'm getting something similar at 7.3%, where 1.7% is French & German and the rest is Broad.

    But compared to him, I don't have any known German ancestry at the level of great-grandparents or the 4/16 known 2x-great-grandparents or 1/32 3x-great-grandparents.

    There are some weird surnames for the individual on the 3x-ggp, his son and wife at 2x-ggp levels though. They are not included on any list of Romanian surnames that I've read and to me they just look ancient.

    https://www.behindthename.com/name/karp
    https://www.behindthename.com/name/isay
    https://www.behindthename.com/name/matrona

    Maybe it will become clearer, once I start digging into the paper trail.

    So, I suggest keeping an open mind until you have enough data to draw conclusions from.
    Last edited by Dorkymon; 01-02-2019 at 03:31 PM.
    Known ancestry: 1/2 Romanian Northeast + 1/4 Romanian Southeast + 1/4 Romanian Bukovina Ukraine
    23andme: 53.6% Greek & Balkan (4% Broadly South Euro), 35.7% East Euro, 0.3% Ashkenazi Jewish, 6.5% Broadly Euro
    MyHeritage: 92.2% Balkan, 5.8% English, 1.1% Eskimo, 0.9% Japanese
    FTDNA: 45% Southeast Euro, 45% East Euro, 4% British Isles, 3% West Middle East, 2% NE Asia
    Global 25: Anatolia_N 50.2%, EHG 32.6%, CHG 11.2%, WHG 3.8%, East Asian 2.2%
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    Quote Originally Posted by Táltos View Post
    Your matches from Italy, and Greece likely have Albanian ancestry. My mother was half Italian/Albanian. We also get matches to some who have ancestry from Greece (4 grandparent too). One of them once told me that the Albanians had large families, and in the Peloponnese. Funny enough that is one of the regions that my mother has a likely match to in the new beta opt in reports.
    This is what I thought the explanation was originally. Many actually do have Albanians in our mutual relatives, but there are some who seem to come from a different 'branch' or the mutual relatives seem to point as to being related through my father (who is full Lebanese). Guess I would need to test one of my parents to find out for sure which side they're coming from.
    78.1% Lebanese (Lebanon) + 21.9% Kosovar (Kosovo) @ 3.3

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    Quote Originally Posted by sublime View Post
    Good question, one that can also be extended to include the GEDmatch 'One-to-many matches' tool.

    What is the minimum size of matching segment that qualifies as a bonafide DNA relative?

    The default value in GEDmatch is 7cM, however, this is primarily in place to make the calculation less CPU-intensive.

    Is it possible that below a certain threshold, the matching segment could be pure coincidence, or that it is such a distant relative that it is insignificant from a genealogical perspective?
    Not sure about the whole science behind the relative finder, but I don't think many people get unusual matches (or at least not in the amount I have). Im just wondering how far back can they go to detect a relative.
    78.1% Lebanese (Lebanon) + 21.9% Kosovar (Kosovo) @ 3.3

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    Some people have said they have common matches that go back to the 1600s, although there may be more endogamy in those lines.

    My farthest back so far are mid 1700s, but I also ignore most of the very small matches as likely not real matches or impossible to figure out. There are regions that tend to get passed down without changing so I have some smaller cM regions that seem to be shared by a ridiculously huge number of people and likely from very far back.

    It would not be that surprising if your American matches have Albanian or Greek and it's just not showing up if it's a very small amount. How large are the matches? I have several on MyHeritage which are false (Norwegian, match me but neither parent). Only one confusing one based on ancestry that I've seen on 23andMe (Serbian with 4 Serbian grandparents, seemingly on my dad's side, my dad is basically British Isles). We share 0.30% (predicted 4th cousins). I have 1.1% general European and 2.6% general southern European, but am otherwise NW Europe. So somewhat mysterious, but I think it's probably not real absent more.

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    Quote Originally Posted by KingofPhoenicia001 View Post
    Not sure about the whole science behind the relative finder, but I don't think many people get unusual matches (or at least not in the amount I have). Im just wondering how far back can they go to detect a relative.
    For autosomal DNA it is really simple.

    You get half your DNA from each parent.

    In turn they each get half of their DNA from their parents.

    If you keep dividing by half for each generation you go back, after 10 generations (approx 300 years), you will only have 0.1% of the DNA from your ancestor.

    100 x 0.5 = 50 (parents)
    50 x 0.5 = 25 (gparents)
    25 x 0.5 = 12.5 (1 x gparents)
    12.5 x 0.5 = 6.25 (2 x gparents)
    6.25 x 0.5 = 3.125 (3 x gparents)
    3.125 x 0.5 = 1.5625 (4 x gparents)
    1.5625 x 0.5 = 0.7825 (5 x gparents)
    0.78125 x 0.5 = 0.390625 (6 x gparents)
    0.390625 x 0.5 = 0.1953125 (7 x gparents)
    0.1953125 X 0.5 = 0.09765625 (8 x grandparents)

    If you were born in 1980, your earliest traceable direct ancestor would have been born in 1680, 300 years before your date of birth.

    Y DNA on the other hand passes from father to son down your paternal line. Your 8 x paternal grandfather would share the same Y DNA as you.

    Similarly mT DNA passes from mother to child down your maternal line. Your 8 x maternal grandmother would share the same mT DNA as you.

    With y DNA and mT DNA, it is possible to go back much further in time to see where two individuals share a common ancestor beyond 10 generations. Although it is impossible to accurately determine how ancient this connection would be. It could be the 11th generation before you were born or an infinite number of generations stretching back thousands of years.

    Hope this clarifies.

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    Quote Originally Posted by msmarjoribanks View Post
    Some people have said they have common matches that go back to the 1600s, although there may be more endogamy in those lines.

    My farthest back so far are mid 1700s, but I also ignore most of the very small matches as likely not real matches or impossible to figure out. There are regions that tend to get passed down without changing so I have some smaller cM regions that seem to be shared by a ridiculously huge number of people and likely from very far back.

    It would not be that surprising if your American matches have Albanian or Greek and it's just not showing up if it's a very small amount. How large are the matches? I have several on MyHeritage which are false (Norwegian, match me but neither parent). Only one confusing one based on ancestry that I've seen on 23andMe (Serbian with 4 Serbian grandparents, seemingly on my dad's side, my dad is basically British Isles). We share 0.30% (predicted 4th cousins). I have 1.1% general European and 2.6% general southern European, but am otherwise NW Europe. So somewhat mysterious, but I think it's probably not real absent more.
    My closest Italian shares .34% (predicted 3rd cousins) but the rest are mostly .10-.14% shared (4th to distant). Interestingly, we only have two common relatives: a Lebanese who I am 90% sure is related through my father and a Slav (Croatian?) who shares many of my Slavic and Greek matches but none of the Albanians. Thats the kind of stuff that confuses me haha. Another example, .19% shared with a woman who is half Irish and half American (gets 100% European BritishIrish/FrenchGerman, no southern Euro at all). We share 18 relatives all exactly like her full Northern Europeans. Kind of funny? There are many matches that just lead me to confusion like this haha.
    78.1% Lebanese (Lebanon) + 21.9% Kosovar (Kosovo) @ 3.3

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    Quote Originally Posted by KingofPhoenicia001 View Post
    This is what I thought the explanation was originally. Many actually do have Albanians in our mutual relatives, but there are some who seem to come from a different 'branch' or the mutual relatives seem to point as to being related through my father (who is full Lebanese). Guess I would need to test one of my parents to find out for sure which side they're coming from.
    Testing a parent will be a big help. Test both if you can. Keep in mind the autosomal DNA does not pass down perfectly in half/quarters either.

    You can inherit more DNA from one grandparent vs another. Here is the breakdown for my daughter who has 3 grandparents tested at 23andme.
    Maternal grandmother-20.7%
    Maternal grandfather-29.3%
    Paternal grandmother-26.7%
    Paternal grandfather-23.1%
    Maternal Grandfather's Y Line: J-ZS1711
    Paternal Grandmother’s mtDNA: U5a1

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