When you get your DNA results, the DNA company tries to give you a
sense of how you are connected to your matches. They will identify each
relationship as parent, close family, sibling, second cousin, third
cousin, fourth cousin, distant cousin, etc.
On MyHeritage it looks like this:
On Ancestry it looks like this:
It's important to understand that the relationship provided is just
an estimate. There are actually a number of possible ways you could be
related to any given DNA match.
Now take a look at those same images and notice that next to or
underneath the relationship you see a number and the initials cM. cM
stands for centiMorgans which is the unit of measurement for DNA. The
more cM you share with a DNA match the more closely related you are. The
less cM you share, the more distant your relationship.
The Shared cM Project
In order to understand better all the possible relationships you have with a DNA match, genetic genealogist
Blaine Bettinger came up with a data driven tool called the
Shared cM Project.
Blaine asked DNA test takers to provide the amount of cM they shared
with known relationships. From this he was able to create charts that
showed the various possible relationships through the range and averages
of centiMorgans.
From the data, Blaine produced the Shared cM Project chart below. In
each box the first line is the relationship, the second line is the
average cM for that relationship and the third line is the range he has
determined based on the data.
So if we take the example above - 2nd-3rd cousin, 276 cM - we would
look for the box where the average is closest to 276 cM. You'll notice
that there are three boxes that are pretty close: Half 1C1R (226 cM),
1C2R (229 cM) and 2C (233 cM). If you look beyond the averages to the
ranges you'll notice that there are even more possibilities. This is
just to show that your actual relationship to your DNA match could be
any of a number of possibilities besides what the DNA company estimates
for you. In this particular case, I know the cousin personally and I am
accurately able to identify her as my second cousin and not a third
cousin or any of the other choices.
Blaine Bettinger, The Shared cM Project, https://thegeneticgenealogist.com
(Click to enlarge), Creative Commons attribution
Interactive Shared cM Project on DNA Painter
Recently Jonny Perl, the creator of
DNA Painter presented a
webinar about DNA Painter
on Legacy Family Tree Webinars (which is free to watch). Jonny has
transformed Blaine's chart into an interactive tool on DNA Painter.
Let's see how it works with two new DNA matches I received just today.
From the main DNA Painter home page choose the Tools menu option.
On the next page choose the Shared CM Tool option:
Next put the amount of cM your share with your DNA in the Filter box.
For this exercise I will use my two brand new dna matches.
For the first new cousin I get this result:
You
can see there are a lot of possibilities for this relationship! In
fact, this cousin I know personally. She and I are Half first cousins
once removed (Half 1C1R). That result was in the second tier of options.
It's important not to make assumptions when working with unknown
matches.
The second new match of the day was also described as a 3rd-4th cousin.
It's
interesting to see how much the results change just by changing the cM a
bit. The results are quite different even though they were both
presented in the same 3rd-4th cousin range. This person is unknown to
me. I will have to compare our shared matches and do some research to
determine which of the above relationships is accurate. It's intriguing
and I can't wait to uncover this new cousin.
Both the
Shared cM Project chart and
DNA Painter are free to use. These tools will greatly help you in your genetic genealogy research. Give them a try.
You can learn more about understanding your DNA results from classes
in the Legacy library. If you are just starting out with DNA take a look
at Blaine Bettinger's
Foundations of DNA series. If you're already pretty comfortable with DNA then choose from among the
74 DNA classes in the library.
Marian Pierre-Louis is the Online Education Producer for Legacy
Family Tree Webinars. She hosts the monthly evening webinar on the
second Tuesday of each month. Her areas of expertise include house
history research and southern New England research. Check out her
webinars in the Legacy library.
Informations from FamilySearch (by asking about 5.5.5):
“The Church of Jesus Christ has the copyright on the Gedcom Specification since 1987. There has not been a legal transfer of the rights we have to the Gedcom Specification.”
So 5.5.5 is not a legal GEDCOM version.