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Paternal Lineage (Y-DNA STR) Basics This is an area for those who are new to DNA testing for genealogy can ask about Y-DNA STR based tests and their test results. All may view this forum, but you must register and sign in to post.

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  #1  
Old 14th June 2018, 02:54 PM
scotto scotto is offline
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Join Date: Jun 2018
Location: USA
Posts: 1
Genetic distance of 2 question.

Hello I have a question.

I have 6 matches on 37 marker test, 3 of the top surnames are the same with a genetic distance of 2, but the surname is different than mine. Can I assume possible common ancestor and somewhere down the line our surname was changed or possible NPE? Both my surname and the one that appears many times from 12-37 markers have a heavy population in Northern Germany together. This is where my 2x's great grandfather comes from and the furthest back I can get on my surname side. My surname doesn't show at all in any of my matches from 12-37.

My main question is can you have a common ancestor with a different surname at genetic distance of 2?
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  #2  
Old 14th June 2018, 03:58 PM
John McCoy John McCoy is offline
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Join Date: Nov 2013
Posts: 712
This sort of test often gives you clues, but not proof. If you happened to match the surname and had a genetic distance of zero, the odds would be very high that you had found an actual relative, but even then, the number of generations separating you could still be too large to be of much help genealogically. NPE is always a possibility, but so is the possibility that you happen to belong in a part of the haplotree where the main STR pattern was established before stable surnames came into use. One thing you might want to do is look more closely at your own matches: are there many different surnames among the kits that FTDNA designates as "matches", or are most of them all one surname?

As an example: My own McCoy kit has several matches at Y 67 with genetic distance of 4 or 5, with the surname McMillan, and there were no other McCoys among these matches. But the Big Y test showed me that I am on a little twig of the haplotree pretty much by myself, separated by several SNP's and probably several centuries from the branch that has all the McMillans, and far removed from the part of the tree where most of the other McCoys are found. The Y DNA tests, especially those based on STR's, don't always give a clear answer. At least I can be fairly sure I'm not a McMillan, and I can safely ignore the ancestry of the other McCoys who have been tested.
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Old 14th June 2018, 08:49 PM
Ivar Kristensen Ivar Kristensen is offline
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Join Date: Oct 2017
Posts: 31
Father/Son tested and match at 67 markers with GD of 2. How is this possible? http://forums.familytreedna.com/arch...p/t-36922.html

Quote:
prairielad

11th February 2015, 10:22 AM

My father and his paternal 1st cousin are 4GD at the 37 and 67 marker level.

My Uncle and same cousin are 3GD @ 37 markers

My father and his brother are 1 GD @ 37 markers. Difference is my father registers a 2 step at DYS576 and my Uncle has only a 1 step.

Last edited by Ivar Kristensen; 14th June 2018 at 09:09 PM.
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  #4  
Old 14th June 2018, 09:42 PM
TwiddlingThumbs TwiddlingThumbs is offline
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Posts: 146
Quote:
Originally Posted by scotto View Post
My main question is can you have a common ancestor with a different surname at genetic distance of 2?
Of course. For lots of different reasons - eg NPEs. But, yes, it is possible to have a gd of 2 even if the most recent common male ancestor pre-dates the formation of surnames. I have 2 matches at 37 markers with a gd of 3 and different surnames and neither is likely related to me within the surname era.
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Old 15th June 2018, 12:12 AM
MoberlyDrake MoberlyDrake is offline
mtDNA: T2b5 | Y-DNA: J-M172
 
Join Date: May 2010
Posts: 1,545
It's impossible to actually tell how far back the common ancestor is. He could be recent or he could predate the adoption of surnames. And a man may have changed his surname for a variety of reasons. Have you joined the surname project for the name you are matching as well as the project for your own surname? The administrator may have some insights.

My 1st cousin and his 3rd cousin have a GD of 2. Apparently there was a different mutation in each of their lines between them and my great-great-great-grandfather. They also have different surnames and, in this case, it's due to a non-paternal event in my line.
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