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Old 5th March 2018, 09:44 AM
John McCoy John McCoy is offline
FTDNA Customer
Join Date: Nov 2013
Posts: 712
You are correct in questioning the idea that the situation of Y-DNA matches who share a surname (without specifying the circumstances) alters the probability that "genealogically significant" relationship exists.

Clearly, if the matches come from a culture that has used a patronymic system or some other system that results in frequent family name changes during past few centuries, there may be a significant probability, not accounted for by FTDNA's statistics and therefore violating the assumptions that went into their algorithm, that two men now have the same surname for reasons other than common descent from a man who lived centuries ago and who bore that same family name. For example, if two modern Norwegians happened to be named Olson AND matched on Y-67 with a genetic distance of 7, it would be ridiculous to suppose that they are more likely to be more closely related than two men who match at the same level but who have different family names. In any event, the suggested probabilities are not based on proved family histories, but rather on statistical models based on a number of (unstated?) assumptions that may not be correct. And, they likely omit other factors that should be important, such as the relative frequencies of the family names involved.
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Old 4th June 2018, 12:28 PM
Ivar Kristensen Ivar Kristensen is offline
FTDNA Customer
Join Date: Oct 2017
Posts: 31
Thank you John for your enlightening comments.

I just received my DYF371X results, and it certainly looks like I'm in a British/Irish/Scottish cluster.

see kit. nr. 755750, under I-M223, M284 Isles; DYF371X 10c-10c-13c-13c

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