FTDNA has introduced a new program which calculates and displays the cumulative probability that two individuals share a common ancestor within the last 4, 8, 12, 16, 20, and 24 generations, or equivalently the last 100, 200, 300, 400, 500, and 600 years because FTDNA assumes a generation length of 25 years. The program is called FTDNATiPTM, It as available on each personal page by looking at Y-DNA matches, then finding the person with the horizontal Y symbol on the right, and clicking on that symbol. FTDNATiPTM, uses new and as yet unpublished mutation rates for specific markers. Consequently the computed probabilities vary with the individuals involved even though their genetic distances may be the same as another pair of individuals. The only results that are always the same are those for a genetic distance of 0 because those pairs of individuals have exactly the same Alleles on all markers.
Here is an excerpt from the FAQ which explains what is so special about FTDNATiPTM, from the FAQ at http://www.familytreedna.com/faqtip.html. For other interesting information, see the FAQ.
“FTDNATiP™ is the world's first program that
incorporates specific mutation rates that have been proven to differ across
markers, which greatly increases the power and precision of estimates of Time
to the Most Recent Common Ancestor (TMRCA). Coupling this program with the
results of a recent mutation rate study conducted by the University of
Arizona, and presented by Family Tree DNA at the 1st International Conference
on Genetic Genealogy on Oct. 30, 2004, has resulted in an extremely powerful
new tool for genealogists.
In order to make these results available to all members of the Ausburn/Osborn surname project relative to other members in the project, they have been added to the genetic distance tables and can be seen by “mousing over” the hyperlinked genetic distances in the tables. The values shown are the percentages for 25 generations, or 100 years, as illustrated below.
First, for all entries that show a 0 for genetic distance, the probabilities are as follows:
Second, for these and other genetic distances up to 7, the results are shown in the hyperlink Screen Tip which appears when you pass the cursor over the hyperlinked genetic distance value.
The six percentage values are shown in order from 4 generations to 24 generations, or 100 years to 600 years, as in the tables above. Beyond a genetic distance of 7, the probability is zero, or negligibly small, for all times through 24 generations, so no probabilities are shown for genetic distances greater than 7, except in a few special cases. NOTE: It is only necessary to pass the cursor over the hyperlink to read the value; you do NOT need to click on the hyperlink to see the value. The hyperlink will always be to this page.
By comparing the percentages for larger genetic distances, it is obvious why certain genetic distances are declared “no relationship”.