DNA is a tool in the genealogist toolbox. As more
and more people have tested, it's become a better and better
tool but it is not a tool that's going to be able to
solve all of your genealogy problems and in some cases,
it's pretty useless as a tool for genealogy.
Howdy, I'm Andy Lee with Family Houston Fanatics and this is a
segment of DNA. Be sure to subscribe to our channel and
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Now, more than 20 million people have had their DNA
tested and this has made DNA a great tool in genealogist
toolbox but there's sometimes where it's not going to help
because there is no DNA to match with a potential
relative. So, let's look at what you can expect to find
when you take a DNA test. We inherit DNA from both of our
parents who inherited from both of their parents and on and on
back through the generation. So, on the surface, it looks
like we should be related genetically to every single one
of our ancestors but because of the randomness of
recombination, we aren't. We also didn't get all of our
parents DNA and they didn't get all of their parents DNA. We
got half our siblings got half and some of that half overlaps
but some of it doesn't. Again, because of recombinations
somewhere down the line, we will have descendants that
don't match DNA with other of our descendants. So, where does
this happen exactly? Well, 23 and me post some statistics on
how likely it is that you share DNA with certain cousins. For
instance, with first cousins, we share DNA with 100% of them,
all of them. For second cousins, it's been
statistically calculated that we share DNA with more than 99%
of them and so far, there's been no documented second
cousins found that don't share DNA. So, in effect, we share
DNA with all of our second cousins but once we get to
third cousins, the numbers start going down. We only share
DNA with about 90% of our third cousins. So, there's 10% of our
third cousins who we're related to but we'd never find with DNA
because our segments don't match anywhere. We both
inherited completely different portions of DNA from our
parents and grandparents and so forth. Now, by the time you get
to sixth cousins, this is really the extent of where
you're going to be able to match segments with DNA and at
the sixth cousin level, we only share DNA with 5% of our sixth
cousins. So, the vast majority of our cousins at this level,
we're not going to see any of our match list because they
don't match with us. Now, I don't want to show just
probabilities. I want to show you some real numbers. So,
we'll use me as an example. I have 32 first cousins. Now, to
some people that sounds like a lot but actually in the last 6
months, I've met some people who have more than 10 first
cousins and I was blown away because I thought I had a lot
of first cousins. My wife only has five first cousins. If you
are the child of parents who were both only children, you
have zero first cousins but back to the probabilities that
23andMe provided. I should be genetically matched to all 32
of my first cousins because that's how closely related we
are. However, only 20 million people in the world have had
their DNA tested. Now, let's use the United States and say
that roughly 3% of the population of the United States
have had their DNA tested. Well, that means of those 32
first cousins, probably only one of them has had their DNA
tested and it turns out that's exactly right I have one of my
first cousins that has had his DNA tested and we match so that
is exactly what was expected now I don't know how many
second cousins or third cousins and certainly I don't know how
many fourth or fifth or sixth cousins I have but I looked at
some different population tables and some estimates that
people have made and basically if you take the number of first
cousins and you multiply it by five and then keep on doing
that through each generation that gives you a roughest of
how many you have and so that's what I used. So, I estimate I
have 162nd cousins. Now, multiplying that by 3 percent,
that means there should be five of them that have tested
through one of the different companies. So far, I have
identified three of those second cousins. Once again,
when we get to third cousins is where it gets interesting. I
should have 800 third cousins throughout the world. I
share DNA with only seven 20 of them and again, we multiply
that by the 3% and it turns out there's actually about 21 of
them that might have tested. So far in my research, I've
identified 5 third cousins. Now, as we go down the list,
we're multiplying each one of those cousins by five and so
the number of cousins increases dramatically but because the
probability of matching with those cousins goes down
dramatically and because only a small number of people have
actually tested compared to the overall population you see that
through the sixth cousin level there's really only about 300
people that I am going to have a DNA match with six cousins
there's more than 100,000 potential cousins I could match
but I'm only going to match with about. 3% of them so what
can you do to increase the odds of finding these second third
fourth fifth or six cousins well the first thing is if
there are older members of the your parents, your aunts or
uncles, your grandparents have them tested. Because your
parents are more closely related to your sixth cousins
than you are and your grandparents are even more
closely related. So if you have their DNA to use you're
going to be able to find those cousins a lot easier. The
second thing to do is test your siblings and your cousins
because remember while you inherited some of your parents
DNA your siblings inherited a different portion of that DNA
and your cousins inherited a different portion of your
grandparents DNA So, some of your third through six cousins,
you may match but your siblings may not match. Likewise,
they're going to have some of those third to six cousins that
they match but you don't match. DNA is not going to help you
find everyone but it can give you clues to find hundreds of
people. So, if you have any questions about your match list
and how to find relatives, put it in the comments below and
we'll try to answer it and if you like this video, give it a
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