Howdy, I'm Andy Lee with Family History Fanatics. And today we have another viewer question for
you. If you'd like to have your question answered, then just put it into any one of
the videos and eventually we come across it. And if it is something I think lots of people
will be able to gain something from, then I'll turn it into a video as well.
So today's question- why do some matches not share ethnicity groups?
Now, this was again from a viewer question on one of the videos.
And here's what the person said,
"Hi, can you please go over why DNA matches might have no shared ethnicity with each other."
You might think, "hey, this is a little odd. We share DNA but we don't share any ethnicity?
But they're calculating ethnicity from DNA, so how is that possible?
"I have multiple matches from around the North Sea."
Okay, so we're talking Northern Europe.
"... and I'm South Asian."
Now South Asian, if I remember right, is like India, Pakistan area.
Very widely different as far as where those two areas are.
And you wouldn't necessarily expect that somebody from South Asia is necessarily
going to have a lot of matches from the North Sea and vice versa.
"... we share mo ethnicity when compared."
And not every website allows you to see what ethnicities you share,
but when they do you can see- 'hey, maybe we share something. Maybe we don't."
So they wanted to know some reasons and so I sat and I brainstormed and I looked at some
different things. And I came up with three main reasons of why we share no ethnicity.
First one, your DNA matches (in other words the segments that match) and the ethnicity
are calculated in completely different ways. They are not the same thing.
When it comes to the analysis, they are not determined in the same method.
Other than the fact that the DNA results are used for both of them. That's about
the where the similarity ends. With this you can have a DNA match
and not match an ethnicity - and that's what the question is here.
But let's flip that around and see if the reverse makes sense.
You can have no DNA match and match in ethnicity.
Well, yeah! That does make sense.
Because, for instance, I primarily have English Heritage.
It's something like eighty percent. Well, you know, all depends on which
company you look at, but the majority of of my ancestry is from England.
On the other hand, I don't match everybody that is from England.
In other words, there's plenty of English people that we don't share any DNA at all.
And I know that because my matches would be vastly larger than it is right now.
For instance, there's roughly 10 percent of the United States that identifies English
Heritage as part of their Heritage. So that's 30 million people.
I don't have 30 million matches in my database. That doesn't add in the other 80 million people
that are in the United Kingdom as well that a lot of them the majority of them have English DNA.
So we can have shared ethnicity without having shared DNA.
If that's the case, then why can't we have a DNA match that doesn't match an ethnicity.
Okay that's what we're going to talk about some more.
Now the DNA match the segments that match they're usually looking at only one of your
two chromosomes. Remember, every chromosome you have a pair a maternal or a paternal chromosome.
Now, you usually only match on one of those. In other words, you match through your
mother or you match through your father. Now sometimes, you may match through both
your mother and your father, but it's very rarely on the exact same segment.
It is almost always on a different segment on the same chromosome
or a different chromosome completely. But all those DNA matches are looking at
one of the pair of chromosomes really to match up. Now, your ethnicity results well they're comparing
it with both of those chromosomes the information together in order to try to
figure out what the ethnicity is. So that's the first reason of how
this is calculated completely different. The next is is that your DNA segment matches-
they are an exact match over some variable length. So you know if you look at your matches you have
anywhere from 7 centimorgans all the way up to 250 centimorgans whatever the longest chromosome is.
And there's usually a minimum length to that which can be interpreted by a certain number of SNPs.
So between you know maybe 700 to 1000 SNPs is the minimum.
Although sometimes it might go down to 300 or 4000 SNPs, but there's some minimum length that is the
threshold of where they'll say a match starts. And that really can go, you know, the whole length
of a chromosome as far as the the length of it. But those segments vary in length. Ethnicity
results- they're not an exact match. What they are is they are a
closest match (really a statistical evaluation) over some discrete length.
So for instance, they're taking all of your chromosomes (all of your DNA) dividing it up
into 100 SNP chunks. Determining what each one of those the closest match it is like. For instance,
hey, this SNP it's closest to English. This next SNP is closest to Scottish.
And on down all of your chromosomes and then summing all of those up to
come up with some percentage of how much of a certain ethnicity you have.
So hopefully you can see there how the DNA match and the ethnicity they're calculated different
ways. They both use the DNA, but they're calculated in completely different ways.
Reason number two- the ethnicity is being compared I said that it was a closest match.
What is it a match too? Well, it's a match to a reference population.
So your ethnicity reference populations don't have the full range of genetic diversity represented.
In other words, there's a lot more DNA in some ethnicity population then there is people that
are in the reference population. Why is that?
Well, first off there's really strict criteria to be in a reference population.
You have to be the only member of your family that has tested.
In other words, they can't already be a member of your family in the reference population.
You have to have all four of your grandparents or all eight
of your great-grandparents (depending on which company is using) that are from the same area.
Now how they define area also is variable. So for instance, you may define area as England.
While another company may define an area as the United Kingdom.
Or even down to a county level, maybe you define area as Cornwall.
So when you're looking at countries with immigrant populations, like the United States or Canada,
it's very rare to have somebody from one of these immigrant population countries
that has all four of their grandparents from the old homeland. Maybe all four of
my grandparents were from the United States, but that's not really a ethnic group in this.
In when we're talking about DNA and genetics here. So we'd really be looking at England.
If I look back, I think when I look at my great grandparents, I know I have
one great grandparent, for sure that is from England because he was an immigrant over here.
But the woman he married was actually the daughter of an immigrant from Germany.
So she's actually primarily German heritage. So right there, with just looking at two of
my great-grandparents- one married couple- I wouldn't fit into any kind
of reference population unless you were looking at Europe as a whole as a reference population.
Now, this is a problem because the reference sets are really small. Simply because there's
not enough people to meet the criteria because we've been mixing for thousands of years.
It's actually rather interesting as they've gone out and tested even some remote groups that,
you know. You wouldn't think have some of the DNA from from Europeans or from Native
Americans or from sub-Saharan Africans. And yet, some of that DNA is showing up.
There are very few groups in the world that are so isolated that you could say
that well they have a pure DNA for this. And those groups are so small that you'd
actually be easy to test all of them- all the people that are part of that group.
But it it's not helpful for all the rest of us- the other eight billion people in the world.
Because humans just have been mixing together for thousands upon thousands
of years. All right.
So the third reason then is there there's a large portion of your matches that are false matches.
And I've done videos on this. Now, this is especially the
case when we're talking about the smallest amount of shared centimorgans.
So when you're looking at 10 centimorgans and less, the number
of false matches increases exponentially. And how are these false matches made?
You can go watch the video, but here's just a couple of ways.
One is a match was made by the analysis of the DNA instead of looking at just the maternal
chromosome or just the paternal chromosome. It actually jumped between the chromosomes
to come up with a match. So you're not really matching with that person.
It just so happens that this little bit of DNA match, with this little bit of your other DNA
match, with this other little bit all adds up to something that looks like it matches someone else.
Another way is, hey, this match might have just been made by chance. In other words,
there's large portions of the population that have that sequence.
Now, in some cases, is these may be people that you still are related to
but you're related to them a thousand years ago or two thousand years ago.
And it just so happens that you share the same segment that many people in that population share.
And this is where we can talk about, you know, pile up regions and why
you don't want to use those as a match. Simply because it isn't indicative of any
kind of a close relationship that you're going to be able to show through genealogy records.
Now, how common is this whole phenomenon- having a DNA match that you don't share any ethnicity with?
I wanted to go through and figure this out, except that none of the companies have an easy
way to just compare your matches by ethnicity. They will show it on a match-by-match basis.
But I can't download a report that has everybody's ethnicity and my ethnicity to go through it.
And it's because they've just gone and increased their reference populations.
A lot of cases and divided them a lot so that there's literally in some cases hundreds
of difference of groups that you're being compared to as far as a reference population.
So what I did is I looked at different from me as possible.
So I started looking at at people from with sub-Saharan African heritage.
Actually I started with Ashkenazi Jewish heritage. Well too many of those also had either little
bits of Ashkenazi Jewish and then the rest of Europe, which I usually
match with anything from northern Europe. And so I moved on to sub-Saharan African.
Now, a lot of these people are African-American or they are ones that have immigrated to Great
Britain in the last hundred years or so. And so they almost always had some other
type of ethnicity group that I matched with the most common one.
I found interesting was Finish. Now, I have a small amount of
Finish on my heritage and a lot of these others also had a small amount of Finish.
So then I went to East Asian, uh, Chinese. And again same thing.
I'm finding some small bits of, you know, Finish that they match and I match for some reason.
So I went to Japanese and Korean because the problem here as I'm
doing this that I realize is my primarily being from England as far as my heritage.
Well, England in the last 500 years was great at going out and conquering everybody.
And so that English DNA has been spread all over the world.
Finally I was able to find somebody. They had to have Eastern European DNA
and they were from Hungary. Now, I chose this because the
Hungarians in particular are genetically very distinct from most of the rest of Europe.
I found one Augustine Ildiko. And she and I do not share any ethnic groups.
You can see that she is primarily Eastern European and Balkan and I am primarily
English and Irish Scottish Welsh. The closest is I have a little
bit of Finish and she has a little bit of Scandinavian but that is it.
Now, we matched 14 centimorgans on two segments each segment was uh 7 centimorgans long.
But because I have my parents DNA on my heritage as well, I was able to basically
prove that this was a false match. Because she does not match my
dad nor does she match my mom. If I was to take a guess as to how
common this is, I would guess it is probably one in a hundred maybe one in a thousand.
But at the same time, I'd like to say every person is going to be different.
Because if you are somebody who is not well represented in the databases, namely if you're
from Asia, Sub-Saharan, Africa, Polynesian Islands, you know, things like that- where
there's few people in the database to begin with. You probably have a better chance of matching
people who don't have any of the same ethnic categories that you have.
I hope you liked that video and the answer to the viewer question.
If you'd like to see another viewer question answered,
then you can watch this video up top here. But be sure to like our channel,
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