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  #1  
Old 7th November 2016, 02:47 PM
Michael Kirk Michael Kirk is offline
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How to Determine Relationship

Thomas Kirk (1778-1846) is my most distant known paternal ancestor - my 5th great-grandfather.

I believe I have identified a man, Vachel Kirk (1783-1836) who was Thomas' brother. However, I'm unsure whether I am confirming that relationship with Y-DNA correctly, and would appreciate feedback/pointers.

Thomas Kirk had 7 sons who lived to adulthood. Curiously, Thomas' eldest son was also named Vachel Kirk (so it appears to be a family name, if the two men are in fact related). Direct male descendants of each of Thomas' 7 sons have completed Y-DNA tests (most up to 111 markers).

A direct male descendant of Vachel Kirk (1783-1836) has also Y-DNA tested but only to 37 markers.

At the 37 marker level, the descendant of Vachel is a match to the descendants of Thomas.

Two of Thomas' descendants match the Vachel descendant with a genetic distance of 1, suggesting a 97.28% likelihood that their MRCA was within 8 generations.

Counting the test-takers themselves and each ancestor back, the 8th generation slot would be the father of Thomas Kirk. Have I done that correctly?

Is there a different approach to take so that I can confidently say that Vachel and Thomas were brothers? I am reaching out to the descendant of Vachel to see if he will upgrade his Y-DNA test from 37 to more markers to yield greater confidence. Would 111 be preferred?

Thank you,
Mike
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  #2  
Old 7th November 2016, 06:07 PM
John McCoy John McCoy is offline
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I don't think you will get any argument at all, that the two lineages are closely related. The real question is whether you can show that the descendants of the elder Vachel can be distinguished by some "private" mutation from the descendants of Thomas. And, whether further analysis shows they are complete matches, or whether the two lineages have some small number of variations between them, you won't have direct proof that the elder Vachel is the brother of Thomas, only that they were very closely related. For example, there could be an error in one or both pedigrees with the result that a generation was skipped or listed incorrectly, or Vachel and Thomas could have been first cousins, etc. Genealogical certainty is frequently relative, rather than absolute. The idea of proof depends mainly on the strength of the paper trail, as long as the Y DNA evidence does not present a clear contradiction. In this case, it is not inconsistent but does not by itself rule out at least some alternatives.

Yes, Y-111 or even Big Y would make the case stronger, to the effect that the Y-DNA evidence does not provide any evidence against the idea that they were brothers or some other very close patrilineal relatives. However, because the mutations that may have accumulated since the 18th Century should be random and very infrequent, just counting them won't be enough to distinguish among the possibilities.
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  #3  
Old 7th November 2016, 07:56 PM
Michael Kirk Michael Kirk is offline
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If I understand correctly, it won't be possible to ever definitively say - with Y-DNA tests (even at the 111 marker level) that Thomas Kirk and Vachel Kirk were brothers?

I've identified a modal haplotype for Thomas Kirk (1778-1846) based on the Y-111 data collected from the 7 male descendants of his who have tested.

Even if I am able to test more male descendants of Vachel Kirk (1783-1836) at the Y-111 level and determine a likely haplotype for Vachel that controls for mutations, I still wouldn't be able to definitively say they're brothers?

The paper trail is pretty non-existent for these two men before each created their own families, so there's nothing for me to turn to as far as standard genealogy is concerned.
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  #4  
Old 7th November 2016, 11:10 PM
clintonslayton76 clintonslayton76 is offline
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Full brothers

"Brotherage" you cannot realistically get. Males from a common father will have nearly identical YDNA at the highest level. A first cousin will share the same YDNA to the point where there can be no distinction.
Since mutations are random and can even "revert" in the "fast" markers, that level of precision can only be achieved when those men rise from the grave and donate YDNA samples. I have fifteen men divided among three males, and we cannot prove that those three males are brothers, but we have virtually no mismatches. The strength of male YDNA is that it can "divide" lines from lines, but it cannot provide the detail within the paternal lines that can "fail to exclude" the possibility that one of the three is a son to the one of the other two, or a first cousin.
Further, the "other" test: autosomal DNA does not distribute shares evenly in terms of strength to a previous ancestor above the parents, in that a sibling can appear to be much less evidently a descendant from a common ancestor in terms of distance, i.e. one living testing sibling of any gender will share about 2500 cM with another full sibling who tests, but one may appear to be three gens from a common ancestor while another may appear to be five or six gens away.

Last edited by clintonslayton76; 7th November 2016 at 11:17 PM. Reason: adding
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  #5  
Old 7th November 2016, 11:30 PM
MoberlyDrake MoberlyDrake is offline
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Do you know the maiden name and parents of the mother of the two hypothetical brothers? It's very iffy at such a distance, but you could do Family Finder tests on the descendants of the two supposed brothers (as many as possible) and then check for matches descended from the mother's family. (And they could still be first cousins if their fathers were two brothers who married two sisters).
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  #6  
Old 8th November 2016, 08:09 AM
Michael Kirk Michael Kirk is offline
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@clintonslayton76: Thank you for confirming that "brotherage" cannot realistically be obtained with just Y-DNA. And don't think I haven't thought about exhumation and DNA testing. I just watched a fascinating lecture on the Earl of Barrymore DNA project that did just that (although I suppose they have more historical imperative than I do...).

It seems at best, if I'm understanding correctly, I can only add support with descendants' Y-DNA (though not singularly conclusive confirmation) to my theory that Thomas and Vachel were brothers.

A Next step could include having the descendant of Vachel Kirk upgrade to more markers (from his current 37) to ensure he is still a match to Thomas' descendants at the higher level but that's the best I can do with him. Is there value in testing other descendants of that Vachel Kirk (assuming there are other direct male descendants living)?

@MoberlyDrake: I don't know the parents' names for either Thomas or Vachel, which is the primary reason for this research effort.

The Vachel Kirk descendant has tested with Ancestry, and doesn't show up as a match to my particular line of Thomas' descendants. I figured this was because too many generations had passed and the DNA was lost in the autosomal shuffle. As another next step, I will make sure the other descendants of Thomas Kirk test their autosomal DNA and search for a match to Vachel's descendant. Thanks

Last edited by Michael Kirk; 8th November 2016 at 08:14 AM.
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  #7  
Old 6th January 2017, 04:05 AM
mouseinhouse mouseinhouse is offline
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If you want to be very ambitious, you could try to recreate the genomes of a near descendant of Vachel and a near descendant of Thomas using the Lazarus application at GEDmatch.com. If you recreate enough of their genomes, then you might be able to show a close cousinship distance between the two recreated genomes, further narrowing down the closeness of Vachel and Thomas.

That would require a bunch of autosomal DNA tests: from several Vachel descendant cousins and several Thomas descendant cousins. It doesn't sound like you've got more than the one Vachel descendant, at least at this time. But as an approach to the issue in general I believe it's sound.
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  #8  
Old 6th January 2017, 08:41 PM
Michael Kirk Michael Kirk is offline
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I had been thinking about this as an option and wondering if it would be feasible. I'm not as well versed in how this process would work.

Do you have a sense of what a good target number of autosomal tests would be for each man? When you mention several is as few as three feasible? I think there are other descendants of Vachel - not male - that have autosomal tested.
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  #9  
Old 27th February 2017, 04:03 PM
mouseinhouse mouseinhouse is offline
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Sorry for the long delay before replying (I thought I'd subscribed to the thread!). My impression from reading about other's work, people reconstructing ancestors at GEDmatch using Lazarus, is that they needed a lot of cousins to get more than half of their grandparent's DNA reconstructed. Like, 6-16 cousins, at least half descended from that same grandparent and also some cousins who are not. To reconstruct a parent would require fewer relatives, 4-8. It's clear this sort of thing is an ambitious project, requiring enough of the right relatives' DNA. I'm interested in doing it, but it will probably take me a few years to get together enough DNA samples.

Some examples in practice:
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  #10  
Old 2nd March 2017, 11:52 AM
Brunetmj Brunetmj is offline
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Well I thought this question should be asked. Have you completed any kind of paper trail? Birth certificates, census information?1778-1846 is not that far back and a records search should turn up information. I think genealogy is most powerful when traditional methods are paired with dna evidence.
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