TMRCA Calculator

This program calculates the probability that two people have a certain number of generations between them, based on the standard infinite alleles formula of Walsh. It calculates both the probability of being at an exact number of "transmission events" between a certain pair of people and the cumulative probability that the actual number of transmission events is less than a certain value. It can list both result types in a table, or graph either type. In either case the horizontal axis stops at the point where the cumulative probability reaches 97.5% or 10 generations, whichever is longer. Note that the number of transmission events is essentially twice the number of generations back to the MRCA (Most Recent Common Ancestor).

Suggested values for the average mutation rate per marker per generation are given below. These are estimates from all available sources by the author as of October, 2006 and except for the FTDNA 12 set are still not very well determined. The SNP rates are particularly poorly known. More up to date estimates can sometimes be found in the Rootsweb genealogy-dna mailing list archives.

FTDNA Y‑12 STR 0.0020    SMGF STR set (no 464)  0.0021    mtDNA complete genome 3·10‑6
FTDNA Y‑25 STR0.0023All 118 available Y STR   0.0025autosomal, X, and Y SNPs1·10‑8
FTDNA Y‑37 STR0.0033mtDNA HVR  2·10‑5
FTDNA Y‑67 STR0.0028mtDNA coding  2·10‑6

This program was created by J. D. McDonald and is public domain.

   Number of markers            Number of markers that match

   Mutation Rate                  Cumulative Probability