25/25 match different surname question

[JamesBianco]

I have 2 exact matches at 37 markers that I'm not even related to.

That you know of... there are always the possibility of Non-Parental events .. 5, 6 heck 10 generations back.

This is always in the back of my mind when I have a close match and no obvious connection to my line.

[lc0]

>> I have 2 exact matches at 37 markers that I'm not even related to ...
>> That kind of situation is what has caused me to lose confidence in the whole thing.

a. Ultimately we are all related to eachother as long as go you far enough back in time.

b. There are most likely 10'000s if not more people that have EXACTLY the same 37 marker haplotype as you do, but they haven't tested. This is easy to see by checking the statistics for each marker, multiplying the relative frequencies times the relevant population size. Reality is a bit more complicated but it is reasonable start. For the distribution of the most-recent-common-ancestor for all those 1000s of 37/37 matches, see the graphs by FTDNA

c. The fewer markers tested the more people will have an exact match. However, the more markers tested the larger the genetic distance to KNOWN relatives (i.e., known from the last N generations). This per definition creates a dilema : testing more markers narrows the group of people with EXACT matches but increases the likelyhood of a increasing genetic distance with the sought relatives.

[AJAskey]

Haplogroups

I have found that determining a high resolution on a haplogroup makes everything much easier. I am in Haplogroup U152 at this time and hoping to resolve this even deeper. This may or may not match my historic paper trail into Scotland. In in any case, I have no need to investigate any Y match or FF match (or paper trail) that is not in a U152 land mass.

[Dumbldorf]

I have found that determining a high resolution on a haplogroup makes everything much easier. I am in Haplogroup U152 at this time and hoping to resolve this even deeper. This may or may not match my historic paper trail into Scotland. In in any case, I have no need to investigate any Y match or FF match (or paper trail) that is not in a U152 land mass.

That may hold true for the Y trail but FF matches can be in other haplogroups.