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Y-DNA Projects Common Ancestors

Time to Closest Ancestor

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Time to Closest Ancestor

The primary objective for participating in a Y-DNA study is determine whether you have a 'Common Paternal Ancestor' with another participate.  This page addresses how many generations back your common paternal ancestor maybe.

bulletStatically, mutations occur between father and son about every twenty to twenty-five years.
bulletOne mutational difference is not considered significant, the probability of relationship diminishes with each mutation.
bulletParticipants with 12 marker results should order the 25 marker test to narrow down the time-frame for determining their Time to Closest Ancestor.

To learn more, see the Time to Closest Ancestor Calculator site.

12 Marker Test - Time to Closest Ancestor

Test results having an exact match on all 12 markers, time to their closest ancestor, can be calculated as follows:

Estimates using the Infinite Alleles method and the standard mutation rate of 0.002 are bulleted below.  This estimate was obtained from this site Probability distribution of time to MRCA: Y Chromosome markers that explains in further details how this information was calculated for test results reflecting a 12 marker match. 

bulletThey have a 50% chance of having a common ancestor within 14 generations.
bulletThey have a 90% chance of having a common ancestor within 48 generations.
bulletThey have a 95% chance of having a common ancestor within 62 generations.

Estimates using the Infinite Alleles method and a high mutation rate of 0.004 are bulleted below. 

bulletThey have a 50% chance of having a common ancestor within 7 generations.
bulletThey have a 90% chance of having a common ancestor within 24 generations.
bulletThey have a 95% chance of having a common ancestor within 31 generations.

Test results having a single step mutation, their time to their closest ancestor can be calculated as follows:

Estimates using the Infinite Alleles method and the 0.002 average are bulleted below.  This estimate was obtained from this site Probability distribution of time to MRCA: Y Chromosome markers that explains in further details how this information was calculated for test results reflecting a 1 single step mutation.

bulletThey have a 50% chance of having a common ancestor within 37 generations.
bulletThey have a 90% chance of having a common ancestor within 85 generations.
bulletThey have a 95% chance of having a common ancestor within 103 generations.

Test results having two single step mutations, their time to their closest ancestor can be calculated as follows:

Estimate using the Infinite Alleles method and the 0.002 average are bulleted below.  This estimate was obtained from this site Probability distribution of time to MRCA: Y Chromosome markers that explains in further details how this information was calculated for test results with 2 single step mutation.

bulletThey have a 50% chance of having a common ancestor within 61 generations.
bulletThey have a 90% chance of having a common ancestor within 122 generations.
bulletThey have a 95% chance of having a common ancestor within 144 generations.

25 Marker Test - Time to Closest Ancestor

Test results having an exact match on all 25 markers, time to their closest ancestor, can be calculated as follows:

Estimates using the Infinite Alleles method and the standard mutation rate of 0.002 are bulleted below.  This estimate was obtained from this site Probability distribution of time to MRCA: Y Chromosome markers that explains in further details how this information was calculated for test results reflecting a 12 marker match. 

bulletThey have a 50% chance of having a common ancestor within 7 generations.
bulletThey have a 90% chance of having a common ancestor within 23 generations.
bulletThey have a 95% chance of having a common ancestor within 30 generations.

Estimates using the Infinite Alleles method and a high mutation rate of 0.004 are bulleted below. 

bulletThey have a 50% chance of having a common ancestor within 4 generations.
bulletThey have a 90% chance of having a common ancestor within 12 generations.
bulletThey have a 95% chance of having a common ancestor within 15 generations.

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