Have you heard that you can do triangulation with Ancestry? There's some confusion out there
between some people who are into genetic genealogy about what triangulation is. today I want to help
clear that up. And what it is you can and can't do with your Ancestry DNA data. Howdy!
Welcome to Family History Fanatics, where we love helping you to climb your family tree and have fun
along the way. Ancestry DNA allows you to do something that I call Match Triangulation.
Now, you need to understand what triangulation is when we're talking about genetic genealogy first.
So, that you can understand what you can actually do with Ancestry DNA data. let's go over
triangulation. to begin with, you need to have at least two people. you need to have a match. A has
to match B., but for triangulation, you need to add a third person- C. So, B has to match Person
C., And we need to have Person C match Person A. So, we have at least three people. And all
three of them match each other. Now, typically when we're talking about DNA and triangulation,
just matching each other is not enough. it. you can't just share DNA. You actually have to
share DNA all on the same segment. So, a specific chromosome. a specific location
start and endpoint on that chromosome. you have to share with all three of these people. what this
means is that Person A, B, and C, who remember all share this same segment, are related through
a common ancestor. in other words, that segment of DNA that these three people share was passed down
through this common ancestor. one of the ways that I like to show this is throwing up a triangle.
And here we can see that A has to equal B. B has to equal C. And C has to equal A. Now,
these segments don't necessarily have to be very long. in a lot of cases, they're, you know, 7-10
centimorgans. if you're able to find triangulated segments that are 15 or 20 centimorgans or more,
that's just absolutely amazing! And it probably indicates a pretty recent ancestor- maybe a
second great-grandparent or. So, or a third great-grandparent. So, that is what triangulation
in the classical sense. that we're talking about with DNA means we have three people that all match
each other on the same segment. Well, if you've tested with Ancestry DNA, one of the things that,
you know, is that they don't provide you this segment information. they provide you how much
you share with your DNA matches. how many segments you share with your DNA matches. And the largest
segment of that, that you share. but each of the individual segments, you know, which chromosome
they're on and where their start and end locations are. they don't provide that. So, what are you
supposed to do with your Ancestry DNA data? When you think of Ancestry DNA, and you hear the word
triangulation, you should be thinking Shared Matches. And this is actually something that all
companies provide you is a list of matches that you share with another person. And sometimes, this
might be called Match Triangulation. but whenever we're talking about Ancestry, this is the only
kind of triangulation that we can do on Ancestry. So, let's go over what this is going to look like.
here I have a Shared Match list between Person A, who happens to be my wife. And
Person B, which is just one of her matches that I chose. Now, as we're looking at this match list,
every single one of these people share DNA with Person A., And they also share DNA with
Person B. I'm just going to choose one of these to be Person C from this list. And you can see that
as I draw the relationships as far as shared DNA. there is a little triangle that forms.
And I think that's where people start to get confused about triangulation. is because we've
got a triangulated group. They all share DNA. Now, this type of relationship- a Shared Match-
it's similar in that it indicates that Person A, B, and C might be related to a common ancestor.
And that's that might is what is highlighted there. because that's the real key difference
between Segment Triangulation and just a Shared Match Triangulation. with a Segment Triangulation,
we're fairly certain that that segment has been passed down from that common ancestor.
however, with just a Match Triangulation, you don't have enough data to be able to
tell whether or not that was passed down. So, for instance. if we go back and we look at this same
people. And we look at the research that we've done. what we may find is that Person C is
actually related to Person A through their father. And Person C is related to Person B through
their mother. So, if we're thinking of segments, it's impossible that these three could share the
same segment. because the relationship is through a father and a mother, which means what is shared
between these different people is going to be on different chromosomes. perhaps the same number
but still different chromosomes. because we get one set of chromosomes from our father and one
set from our mother. Now, just because this can happen. And as you look at some of these matches
more and more. you'll see that it doesn't mean that Shared Matches or that Match Triangulation.
in this regard is useless. it doesn't mean that it doesn't have any value. in fact,
what I have found from my personal experience. And this is looking at,
you know, your the most closely related matches. isn't looking at all the matches down to
seven centimorgans and below. but mainly the more closely related matches if you find triangulated
groups. in other words, with a Segment Triangulated between at least three people.
99% of the time, there is going to be a Most Recent Common Ancestor. there's actually
a scenario that can happen where you can look like you're triangulated. But you're actually
not all related to the same common ancestor. but that is very rare. with Shared Matches, we
actually see somewhere between 75 and 90 of those Shared Matches you are able to see a Most Recent
Common Ancestor. Now, again this is for the ones that are more closely related to you, let's say,
uh, 20 centimorgans and above. as you get down to more and more of the smaller 10 centimorgans or 7
centimorgans, you start to have a large number of false matches which of course you're not related
to and any kind of triangulated groups you're not going to find. but Ancestry, on their Shared
Matches, they only report 20 centimorgans and above. So, for that Shared Match list, probably 75
to 90 of them, there is going to be a Most Recent Common Ancestor. what this means is that for
somebody starting out, this Shared Match list is perfectly fine to get used to. doing some research
identifying people and comparing trees in order to find some of these Most Recent Common Ancestors.
but as you have sort of exhausted what you can find with just the the Shared Match list,
it's probably time that you're testing with another company in order to get some of that
segment data so that you can do some of this triangulation. the nice thing
about the triangulation is as we get to smaller segments like 10 centimorgans and 7 centimorgans.
if we can find a triangulated group with them, even though that 7 centimorgans is
just a really small amount of DNA, because of these other people that share that same segment,
we have confidence that there is a Most Recent Common Ancestor that we can be working towards
identifying. if you still have questions about DNA consider, joining us for our free DNA live
streams where we answer your questions. or become an FHF Xtra Member when you will have access to
more DNA Q&A sessions. As well as webinars where we teach you about DNA. So, if you've only tested
your Ancestry, then don't worry. there's still a lot of valuable data there for you to start
to glean. And in fact, Ancestry has the largest database. So, you're going to have more matches
from them than anywhere else. And in fact, somebody could probably spend their whole life
just researching each one of those matches, trying to find out how they fit into their family tree.
Now, if you would like to learn more about triangulation and the GEDmatch tool that you
can use. why don't you check out this video on the top here? If you want to learn something else
about DNA, then try this video on the bottom right down here. that's out in the links.