Sorry about the last post - I am using my laptop, literally on my lap, and
hit send too soon.
Chart:
Understanding MRCA
1. If I submit a sample to you for testing and you find that I match exactly
with another person, how many generations ago did we have a common ancestor?
Here are the times back to the MRCA when ALL the markers match. For example,
with 37/37 (all 37 markers match), there is a 50% probability that the MRCA
was no longer than 5 generations, and a 90% probability that the MRCA was
within the last 16 generations. Compare these with 25 and 12 -- with 25
markers, there is a 50% probability that the MRCA was within the last 7
generations, while with 12 markers, there is a 50% probability that the MRCA
was within the last 14.5 generations.
Table 1. Probability for Most Recent Common Ancestor (MRCA)
Number of matching markers
50% probability
that the MRCA was no longer than this number of generations
12 of 12 match - 14.5 generations.
90% probability
that the MRCA was no longer than this number of generations
12 0f 12 match - 48 generations.
95% probability
that the MRCA was no longer than this number of generations
12 of 12 march - 62 generations.
Here is the link to the entire chart
http://www.familytreedna.com/faq2.html#table1
Vickie