Colony Research Group
Genealogy ~ DNA ~ Archaeology
Does the MCRA Really Mean?
MCRA or time to the Most Common Recent Ancestor is a calculation provided
by both Family Tree DNA and Ancestry.com for their clients who have taken
the Y-line DNA tests. I have a great example of how this actually
translates into reality.
I receive communications from people who say something like this:
says that I'm related to John Doe within 6 generations. I have both of
your genealxxxxxogy to 6 generations, and I can't find our common ancestor.
What is wrong?"
answer to "What is wrong?" is easy. The person doesn't
understand what the tool that estimates MCRA is telling them. And, I'm
betting they didn't read the instructions and explanations either, that is
if they tested at Family Tree DNA who provides such.
Tree DNA provides a great deal more information and a far more robust tool
than Ancestry. Family Tree DNA begins with this information:
"The probability that John Doe and William Doe shared
a common ancestor within the last..."
can also change the generational display. I change mine to "every
is followed by an explanation and instructions for how to refine the
Refine your results with paper trail input
However, these results can be refined if their
paper trail indicates that no common ancestor between John Doe and William
Doe could have lived in a certain number of past generations.
If you don't know this information for a
fact, do not change the "1" in the box in the next paragraph.
However, if you have the information, please enter in the box and click on
the recalculate button.
John Doe and William Doe did not share a common ancestor
more recently than
generation(s). (Because the important factor in
calculating the time to the Most Recent Common Ancestor is the number of
generations between which mutations could take place, the number of years
per generation is irrelevant in FTDNATiP™ calculations). 1
that, additional explanation and a reference to a FAQ sheet:
* The FTDNATiP™ results are based on the mutation rate
study presented during the 1st International Conference on Genetic
Genealogy, on Oct. 30, 2004. The above probabilities take into
consideration the mutation rates for each individual marker being
Since each marker has a different mutation rate,
identical Genetic Distances will not necessarily yield the same
probabilities. In other words, even though John Doe has a Genetic
Distance‡ of 4 from William Doe, someone else with the same
Genetic Distance may have different probabilities, because the distance of
4 was prompted by mutations in different markers, with different mutation
‡Note: The Genetic Distance is
the count of the total difference between two individuals. For example, if
a marker differs by 2, then the Genetic Distance will count this as a
distance of 2.
More questions? Please refer to the FTDNATiP™ FAQ
is a huge difference compared to Ancestry who only gives you a number with
absolutely no explanation at all:
MCRA is the small number beside the name - so John Doe is an MCRA of 2 and
William is 14. I have highlighted these in red below so that you can see
is the explanation the Ancestry which is followed by the match table.
"You could be close to a meaningful family
connection! The list below is sorted by how close your DNA matches (MRCA).
The closest matches are at the top."
what does all this really mean, in real life, to me?
I have a client who has tested at both locations, and has another man who
he matches both at Ancestry and at Family Tree DNA. In addition, we know
who their common ancestor is, and we can use this information to compare
the accuracy and usefulness of the MCRA calculations.
Ancestry, these men have tested 34 markers in common and have 4 mutations
difference. Ancestry calls this relationship a distant match at 24
generations to the most common recent ancestor (MCRA).
Tree DNA, they have tested 37 markers in common and have 4 mutations.
Family Tree DNA, without refining the MCRA with the paper trail, calls
this as the 50th percentile at 11 generations. This means that there is a
50% chance that you have a common ancestor within 11 generations. I use
the 50th percentile number because that is the "most likely"
spot - meaning that it's equally likely that your ancestor was closer
generationally or further away.
that these men are at 8 generations to a common ancestor for one man and 7
generations for the other.
Family Tree DNA's chart for 7 and 8 generations, that percentage or
probability is 20% and 27% respectively.
| Real Relationship
|| 7-8 generations
|| Proven by paper trail
| Family Tree DNA
|| Not provided