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Author Topic: A question on probability....  (Read 1900 times)
New Member
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« on: July 15, 2006, 09:53:22 AM »

Here's a question on probabilities... I'm adopted and I have no records on my birth parents, so my last name could be anything. I recieved my 37 marker test and went to my "Y-DNA Matches" page. Under my 25 marker matches I have a significant amount of exact matches with a certain sirname or a variant of it. I don't have any exact matches on my 37 markers, but I do have two people of that same sirname that match at a distance of 2, and one person of the same sirname that matches at a distance of 1. Now, can these results be interpreted as that I actually belong to this sirname group? Or do I need more definetive proof (ie. paper trail, 67 marker test, etc)?
Terry Barton
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« Reply #1 on: July 15, 2006, 01:37:22 PM »

This is a strong indication that your birth father's surname was the same as the one that you are nearly matching.?

I am not sure how you'll ever have a paper trail to tie to, but it might be useful to see if this surname is in the area where you were born (if you know it)

The higher level of match that you have, the more likely that this is someone with whom you share a recent common ancestor.? Increasing to 67 markers may help.?

Don't get too focused on the precision of the match, as mutations are totally at random.? In my personal example, you can see this, as if you were to  simply count mutations, you'd decide that Richard was more closely related to my Uncle Bob than I am.?

I am only 41/43 (Sorenson test) with my uncle Bob, as my Dad and I each started a mutation.? On the other hand, my partner, Richard, is 43/43 with my uncle.? However, Richard and Bob can't share a common ancestor born any later than the 1620s, while Bob's father and my grandfather are the same man.

It also makes a difference which markers you are comparing.? If you use our FTDNA markers comparison, Bob and I are 36/37 and Richard and Bob are also 36/37 - but different markers are involved.

Suggestion:? go to the project site where you are matching and see if they have established an ancestral haplotype for the common ancestor that you share with the close matches of yours.? Then:

1. See what your comparison is to the ancestral haplotype

2. See if any of the men in this group are sharing a mutation with you (as compared to the ancestral haplotype)

3. Talk to the Project Admin about joining their project.

Good Luck!? Terry?

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