Of the thing that people get overwhelmed with the GEDMatch
website is the amount of information that you are given
and the idea here is is they're going to give you everything
that they have and you can use that to figure out your
research how you want rather than trying to give you
specific things and only those specific things and you have to
figure out how to use just those specific things. They're
going to give you everything and that's where the gen column
comes in. People have asked what does the gen column mean
and how can I use this gen column in my genealogical
research. So today I'm going to go over gen in GEDmatch. Now
if we go over to GEDMatch in the one too many tool and we
look at a list here. We are going to see several different
columns and the one that I'm concerned about here is the gen
column under autosomal. And we click on the little question
mark we get an explanation of it as well as a link to Kitty
Cooper's blog where she describes this but you can see
that as I'm looking at this list, the numbers go from one
up to two then three then four and they can go even higher
than that depending on which matches you are looking at. So,
what does this column mean and then, how can we use it? Now,
typically, what this is usually described at and where it's
listed on the 1 to1 is the generate to the most recent
common ancestor MRCA. In other words, how far distantly
related are you to this match? Now, that verbiage in there has
a couple of caveats here. So, first off, if it's listing your
parent or your child, it says that gen number should be one
which makes sense because you're just one generation from
either your parent or your child. Then, it says, an aunt
or niece is about a 1. 5 okay if you think of going one
generation to your parents another generation to your
grandparents and then we have to subtract a generation to go
to our aunts well we're actually really only
subtracting a half a generation that kind of sort of make sense
grandparents is a two yes that's two interestingly enough
siblings are a 1. 2, which when we think about the difference
between going through an aunt or a niece to a or versus a
sibling we said for an antennase we're going back two
and then coming forward one but it's really only a half because
it's not the same person so we're saying a 1. 5 well with
siblings we're going back one and coming forward so we really
would think that it would be like a. 5, but it's 1. 2 so
that part might be confusing sometimes then we get to the
next part it says for cousins subtract one from the number so
if it shows generations of four The suggestion is third cousin.
So let me go back to my one to many here really quick. So I
have these ones and this is all either me or my parents. And
then I have a 1. 5 1. 5 1. 5. Those are going to be my aunts.
And then I have some two aunts, uncles, or grandparents. Oh
those are grandparents actually. I know they're
grandparents because I have my GEDmatch on them. So my
grandparents show up as 1. 5s and then we get to a 22. 5 and
then we get into these threes fours natin for cousins. So,
using what this says, you would assume that a 1. 5 is about a
first cousin once removed. A or sorry a 2. 5 would be about a
first cousin once removed because that would then be 1. 5
cousins I guess. A 3. 5 would be about second cousins once
removed maybe. So let's take a look at some of this data in a
different way. Now Kenny Cooper's recommendation is that
we follow up with anybody who is a 4. 5 or less. So in other
words about a third cousin once removed or less. Start with the
closer ones. That's common sense with a lot of DNA
research. You don't want to go and pull out somebody who's six
generations removed from you and try to figure that right
away. You want to make sure you have all of your close
relatives figured out first so that you can link those close
relatives to these other more distant relatives as well and
finally, this tells us that accuracy in autozoma matching
declines after third cousins. So, if we're looking at
anything more than third cousins, then, that is going to
decline. In other words, if you're looking at anything
above a full on generation that accuracy of that is going to be
very questionable. Now let's look at this data in a
different way. What I did is I took I think 3001, 000 matches
1, 000 my top matches and I basically graphed how much
shared DNA to what the generation is and you can see
that as we get closer to almost no shared DNA we are up to
practically five generations and and sometimes even more.
This this only went down I think to about 18 centimorgans
or so. Whereas if we keep going over with more we're seeing
that generations go up and up and up until we get to the one
which is our parents or our children. So if we start to
graph some of these people on here. Our parents is really
easy. They share a very narrow amount. You're going to share
right around 3500 centimorgans with your parents or with your
children for that matter. And that makes sense because we get
a set of chromosomes from each one of our parents in a set of
chromosomes is 3500 centimorgans now when we're
talking about every other relationship it's not an exact
number we may throw around exact numbers at different
times but what it really is is a range of numbers so we start
with siblings and you'll notice that our siblings share from
just above 2000 centimorgans to just below 3, 000 centimorgans.
Anything in this range could be siblings and this includes not
just regular siblings but 3/ 4 siblings. It doesn't include
half siblings. So the next group we have is sometimes
called the quarter group and that's because instead of
sharing 50% of DNA like siblings do we share 25% of our
DNA on average. And this includes grandparents, aunts,
uncles, nieces, nephews and half siblings. Now, what you
will notice in this group is that it starts to overlap the
siblings group. Now, not by very much. What this means is
that you could have a grandparent that you share on
the high end of DNA with and that's as much DNA as you share
with a full sibling who happens to be on the lower end of what
that group typically shares and this is one of the things that
we will see as we add each group is that there's going be
some overlap and more and more of it. So we have the first
cousin group. This includes not just first cousins but great
grandparents, great aunts and uncles and half aunts and
uncles. Half nieces and nephews. You'll notice that
there is a little bit more overlap than there was between
the quarters and the sibling group. And we continue to go up
this line and we get to the second cousin group. Now
there's more overlap with the second cousin group and the
first cousin group than with the other ones. Which means
it's much likely to have somebody that maybe looks like
a first cousin but it's really a second cousin or vice versa
and we can go down further and further but in order to start
to see some of the other groups we've gotta change the scale
you'll notice here this is going from zero to 3500
centimorgans and now I'm going to change it so it's
going from zero to 250 centimorgans so we'll start
with that second cousin group and you'll notice here that
second cousin group covers almost all of this scale down
to just below 50 centimorgans. We share DNA with every single
one of our second cousins. Not necessarily our second cousins
once removed or twice removed but all of our second cousins.
Then we start to get into the groups where we may not share
DNA so they start at zero you'll notice that the third
cousin group also covers most of this range just above 200
centimorgans so there's a big overlap between third cousins
and second cousins and fourth cousins again a big overlap
fifth cousins still quite a bit of overlap in fact this fifth
cousins covers almost half of what the third cousin group
does and it covers about two 3 what the fourth cousin group
does and then we get the sixth cousins which again it covers
still about half of the fifth cousin group and a little bit
more a little bit less than a quarter or a third of the
fourth cousin group as well as some of the third cousin group
and if you look closely you can see that hey this sixth cousin
group it also covers some of the second cousin group so
let's lay out this graph in a different way so here we begin
change the scale of generations. Now we're just
going from third to fifth. So if we remember what the rule in
the GEDMatch gen column says is for cousins you should
subtract one from the generations to tell you what
cousins. So a generation of four would be a third cousin
suggestion. And here is the problem with that. While
GEDMatch does say hey anything more than third cousins starts
to get less accurate. I would argue that you know, anything
starting at second cousins starts to get inaccurate and
here's why. This line represents where the four
generation is which correlates to about 55 centimorgans. In
other words, this generations is really just a substitute for
the number of sentimorgans and as we can see here at 55
centimorgans, not only could we be in the third cousin group
which that rule of thumb would indicate as a possibility but
we could also be in the second cousin group, the fourth cousin
group, the fifth cousin group, or the six cousin group. In
other words, it's not just a third cousin as a good
suggestion. There's you know, a range of five levels of cousin
or more that you could be. I haven't plotted on here seventh
and eighth cousins but there's some where depending on how
much centimorgans you share, you know, in that 25 range you
could be seventh or eighth or 9th or tenth cousins with that
as well as sixth, fifth, 4th, and third cousins. Here's my
point in showing you this. The value on that chart it's
helpful for siblings for grandparents for even first
cousins and people in that area but because the number of
generations is basically calculated from the amount of
shared DNA that you have you can just use that value and so
actually in my research I've never really used the
generation column or even look at it or pay attention to that
generation column because all that information is contained
within the amount of shared DNA that you have anyway and that's
what I would recommend start with looking at let's say 35
centimorgans and above that's right around where that 4. 5
level is and if you are able to identify who those people are
then great you can use that to help find some of the lower
ones but I would say don't use the generation columns if it's
above three as an indication of how closely related you are as
you can see we just at number four and you could be anywhere
from second cousins all the way up to six cousins. That is
quite a spread you're talking about 150 years or more
difference between where your most recent common ancestor is
just with that number. Now, if you would like to learn how to
use the one too many tool, then check out this video up here
but if you want to learn something else about DNA, then
check out this video down below. Now, the last part of
this is that Kitty Cooper So, forget that. Let's look at this
data in a different way.