I updated from Y-500 to Y-700 and now there are four "matches" appearing on my Block Tree. These are my only matches but, unlike me, they have more recent haplogroups downstream from FGC-17460. There are several other surnames that also have FGC-17460 but they are not considered matches. Is that because they have more than 30 Non-Matching Variants compared to my results? If so, do my matches mean anything of significance compared to any other male with FGC-17460??

Thanks,
Shane

I did some searching for previous threads and found that the Block Tree has been confusing for more than just me. I understand that fewer NMVs means a relatively closer connection. But in my mind a "match" is something more meaningful that a 2-step haplogroup difference. My closest match appears to be around 1,826 years ago, if I did the math right (21 NMVs x 83). That's starting to get useful for my goal of better understanding my ancestry in the Early Middle Ages. Please correct me if I'm misunderstanding something.

Shane

Shane,

The correct formula is for TMRCA is [(NMV/2) x years-per-NMV], but I'd suggest avoiding using this method and directly lookup the TMRCA estimate using FTDNA's "Discover" tool.

Their TMRCA estimates account for many factors that the simple rule of thumb measures can't account for. Plus FTDNA give you 95% and 99% confidence intervals in addition to the central estimate.

Regardless of the number NMVs, you are more closely related to people within your terminal haplogroup than to people outside of it. ?If you're in a paragroup it's a little different.

Vince

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Thanks for the replies Vince and Myles. TMRCA has always been a bit of a mystery, this helps.

All that's been said here regarding TMRCA is correct but a real world example may help. The 83 year rule is very much an average and, as such, is reasonably close over long periods of time, say 1,000 years or more. But the shorter the time the less accurate it becomes. I ran a study of 13 men, all descendants of one man born in 1646. We are descendants of four of his sons and continue to branch further over time. 8-10 generations have passed with half of us at 9 generations since the birth of our MRCA. The number of NMVs that have grown into each of those lineages varies from 2 to 7. If you were to compare any two of us using the [(NMV/2) x 83] formula you could get a birth year for our MRCA of 1858 to 1485. When doing this for each possible pair of us, the distribution does come very close to the expected Poisson distribution that is the basis for the confidence interval that FTDNA gives.

Mike,
From what you said, it seems that the accuracy of a TMRCA depends on the number of examples that can be tested. Since it's just me the results are likely to be off by a significant amount, right?

Not exactly related but I'd like to hear opinions: I've read often that I'm actually more closely related to those who share my terminal haplogroup than to those who have downstream subclades. So it seems odd to me that neither of the two men who are stuck at FGC17460 with me shown up as matches, yet four men who have several subclades beyond me are matches. Is there any rhyme or reason to the number of NMVs you can have with someone in a close branch?

Shane

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Shane,

Shane

Iain gave a thorough reply regarding TMRCA on /g/R1b-U106/topic/106393562 that you may not have seen that would answer your first question.

Regarding relatedness with those in FGC17460 vs downstream terminal groups and to expand on what Vince said: Those in the downstream terminal haplogroups are also in FGC17460 and therefore you are all "equally" related. You all had the same terminal haplogroup (FGC17460) before a couple of them got matches forming a new terminal haplogroup. That did not make them less related to the group; it only made them more closely related to each other.
An analogy may help. Think of FGC17460 as a group of Europeans. You are all equally related because you are all Europeans (we know nothing else about you yet). Investigating further we find a pair of you who are French and another pair who are German so they form two downstream groups. You don't know who you are yet because no one matches you well enough to form a group. But you happen to be Swiss and the other two Europeans are British and Portuguese. You are a "match" to the French and Germans because you are a little more closely related to them than you are to the other two. In terms of NMVs, you could be just a bit one side or the other to whatever the cutoff for a "match" is.
In theory, you could form another group with those downstream groups who are matches; a haplogroup intermediate between your current one and theirs that would become your new terminal haplogroup, but not theirs. Sometimes it takes a long time for FTDNA to process that. Also keep in mind that "terminal" is somewhat meaningless unless its just you and your father. The terminal haplogroups evolve as more results come in and should really be "most recent" haplogroup.

Cheers
Mike

Thanks to everyone for their help, really appreciated. That was a great explanation, Mike. Even an Art Major understood it. I never really thought about a bridge subclade connecting to another haplogroup. I guess I always assumed any in-between subclades would already show up in the results. ?

Given the tribal nature of the early Germanics, it would seem pretty likely to find many seemingly unrelated subclades that were part of the same historical experience for at least some period of time. It is interesting that when looking at the FGC-17460 participants in our U106 project, they all seem to divide essentially into two STR haplotypes. One group are DYS392-12 and DYS389ii-29 while the others are DYS392-13 and DYS389ii-30. Almost all are DYS439-10. I know not to make too much of STRs, but it seems fairly consistent. Whether or not that means anything, I have no clue.

Shane?