### TMRCA Calculator October 2014 version

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 generations back to the Most Recent Common Ancestor (MRCA) of a certain pair of people and the cumulative probability that the actual number of generations is less than a certain value. Note that the convention using generations is changed from an earlier version of this calculator which used "transmission events". It can list both result types in a table or graph. In either case the horizontal axis stops at the point where the cumulative probability reaches 95% or 10 generations, whichever is longer, or an absolute max of 50,000. Beyond 90% the calculation becomes inaccurate.

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, 2014 and except for the FTDNA 12 to 67 marker sets are still not very well determined. The SNP rates are particularly poorly known. For the Y chromosome these rates assume a 31 year generation.

This calculator can use billions of markers. For BigY we suggest 10 million markers, for Full Genomes Elite we suggest 20 million, using the mutation rate listed below, and counting *all* markers which differ between two people. However, if comparing many people and using only markers for which no more than 5% of those people have no-calls, use instead a value of 8.3 million markers for BigY.

FTDNA Y‑12 STR | 0.0020 | mtDNA complete genome | 3·10‑6 (type 3.e-6) |

FTDNA Y‑25 STR | 0.0026 | mtDNA coding | 2·10‑6 (type 2.e-6) |

FTDNA Y‑37 STR | 0.0042 | mtDNA HVR | 2·10‑5 (type 2.e-5) |

FTDNA Y‑67 STR | 0.0029 | autosomal and X SNPs | 1·10‑8 (type 1.e-8) |

FTDNA Y‑111 STR | 0.0026 | Y SNPs (BigY etc.) | 3.0·10‑8 (type 3.e-8) |

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