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

 

Kerchner Surname Project Example of Using Henry Numbers to Show Relationships to 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

 

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Copyright © 2005

Charles F. Kerchner, Jr.

All Rights Reserved

Created: 15 Oct 2005

Updated: 18 Nov 2005