Most Recent Common Ancestor (MRCA)
The most recent common male ancestor, or most recent
common female ancestor, from whom two or more individuals biologically descend. Typically used in Genetic Genealogy discussions in
relation to finding the most recent common direct male line ancestor for two or
more males in Y-DNA testing and analysis in a surname project or the most
recent common direct female line ancestor for two or more individuals in mtDNA
testing and analysis for a maternal line project. Note: There is one and only one MRCA (male or
female depending if it’s a Y-DNA or mtDNA project) for a known to be
biologically related group or cluster tested.
Source: http://www.geneticgenealogydictionary.com/
See the example Descent Tree Chart
linked to below prepared for the Kerchner Surname Y-DNA
Project showing the earliest known ancestor (in this case the immigrant
Adam) and the MRCA, i.e., the Most Recent Common Ancestor, in this case
Frederick. Note: The earliest known ancestor and the MRCA is not the same
person and in many cases that is true. In this example the reason they are
different is because the immigrant ancestor had only one son so all male line
descendants lead back first to Frederick Kerchner, i.e.,
the “most recent” common ancestor. The chart also shows the transmission events
as black nodes on the connecting lines down the chart. This is the minimum
number of births required to create the individuals who have been Y-DNA tested
in “the proven to be related from traditional evidence” group or cluster in
your project starting from the MRCA. When preparing a chart like this always
put the sons in each generation in each branch of descent from left to right in
order of birth in their family. That helps others quickly understand and see
the relationships when viewing your chart. You can also fill in the Henry Numbers if you know
them. The Henry Number is a useful tool in surname projects and can be used to
indicate relationships in other charts and reports in your surname project such
as your Excel table used to display the group or cluster Deduced Ancestral
Haplotype and the mutations, if any, observed in descendants tested. See the second link below for and example of
such an Excel table.
Diagrammatic Example of
Counting Unique Transmission Events from the MRCA in a Surname Project
Time to Most Recent
Common Ancestry (TMRCA) Estimation Algorithm
Using Genetic Marker
Similarity between Two Individuals
By Dr. Bruce Walsh of
the University of Arizona
Time to Most Recent Common Ancestor mtDNA Calculation Example
Copyright © 2005
Charles F. Kerchner, Jr.
All Rights Reserved
Created: 15 Oct 2005
Updated: 18 Nov 2005