Help me understand DNA testing

[dfmacliam]

So how does it work if my Scottish line comes thrugh my mother, her father and grandfather, thence through her great grandmother to her GGM's father and patrilineal from there?

Obviously the Y test isn't right, but will the mtDNA test shed light any better? Or is this a case of "you're hosed, turpin"?

I would think if you had an uncle or someone from her male line take the test... it will reflect that ancestory

[O'Callaghan]

I would think if you had an uncle or someone from her male line take the test... it will reflect that ancestory

This is similar to my situation. I have two uncles (my mum's brothers) who are the last male O'Callaghans of the name in our family. One never married, and the other married someone who already had a daughter and didn't want more children. They are both well into their eighties, so there's no likelihood that either of them will have a genetic son now.

I would love to know what a DNA test on either one of them would show, but I am hesitant to ask them to get tested. I doubt if they would immediately realise that it would only take a scraping from under the tongue (or so I've heard). OTOH, if it is left too long, then eventually it will be too late, for the saddest of reasons. I think I ought to speak to my mum about this. She is the family genealogist anyway, so she would be interested in the results I'm sure.

The burning question that it ought to answer is whether we are all descendants of Ceallachan of Cashel, King of Munster, d.953, or simply, as we already know, descended from a long line of Irish sailors. Whether a Y DNA test could even answer that I'm not sure, but the only way to really find out is to test one of my uncles.

[ForresterModern]

This is similar to my situation. I have two uncles (my mum's brothers) who are the last male O'Callaghans of the name in our family. One never married, and the other married someone who already had a daughter and didn't want more children. They are both well into their eighties, so there's no likelihood that either of them will have a genetic son now.

I would love to know what a DNA test on either one of them would show, but I am hesitant to ask them to get tested. I doubt if they would immediately realise that it would only take a scraping from under the tongue (or so I've heard). OTOH, if it is left too long, then eventually it will be too late, for the saddest of reasons. I think I ought to speak to my mum about this. She is the family genealogist anyway, so she would be interested in the results I'm sure.

The burning question that it ought to answer is whether we are all descendants of Ceallachan of Cashel, King of Munster, d.953, or simply, as we already know, descended from a long line of Irish sailors. Whether a Y DNA test could even answer that I'm not sure, but the only way to really find out is to test one of my uncles.

Theis no scientific way to prove it, even if you have yDNA profile on Ceallachan of Cashel or one of his direct patrilineal verified relatives, your paper trail is far more likely to yield results. YDNA on your uncles would be helpful for you to trace that particular lineage and see if it matches up with those of other callahans, particulalry in sizable numbers in the local where that ancestor hailed from. If one of them could prove descendency then you might be in luck, but still all you have proved is that you and the other person with the matching profile have at least one common ancestor, not necessarily that it actually is Ceallachan. It could be anyone who he shared a common male ancestry with, potentially generations above even Ceallachan---his father, uncle, nephews, grandfather, great grandfather, their other siblings or uncles or nephews, etc... All yDNA profiling proves is common ancestry on the male lineage side of SOME SORT, not any specific sort.

[Bugbear]

Ya, that's why I said it might open a few cans of worms...

[gilmore]

Ya, that's why I said it might open a few cans of worms...

As Oscar Wilde put it, "You should study the Peerage…It is the best thing in fiction the English have ever done."

[Bugbear]

Oh, Darth Gilmore! Are you my real father?

I suppose whether the genetic test of any particular clan chief turns out to match up with the rest of the family or not doesn't change the way it is supposed to be; at least in theory. It does, though, relate to tartan. That is, a clan tartan is chosen or accepted by the clan chief, and only the clan chief. The title of clan chief is usually based on blood relations, or put differently, the blood line of the chief must be passed on through genetic offspring for the clan to continue to have a chief. That does make the clan tartans related to genetics and the passing on of genetics, but not the genetics of the clan members who are swaring loilty to the chief.

I don't know that mix ups and errors, or things like that are the norm in the passing along of the title of chief through a blood line.

[gilmore]

Oh, Darth Gilmore! Are you my real father?

I suppose whether the genetic test of any particular clan chief turns out to match up with the rest of the family or not doesn't change the way it is supposed to be; at least in theory. It does, though, relate to tartan. That is, a clan tartan is chosen or accepted by the clan chief, and only the clan chief. The title of clan chief is usually based on blood relations, or put differently, the blood line of the chief must be passed on through genetic offspring for the clan to continue to have a chief. That does make the clan tartans related to genetics and the passing on of genetics, but not the genetics of the clan members who are swaring loilty to the chief.

I don't know that mix ups and errors, or things like that are the norm in the passing along of the title of chief through a blood line.

Come to the dark side, Ted.....

Right.

It should be pointed out that in law there is a presumption that a man is the father of his wife's children. Hence, clan chiefships, titles, etc---which are a form of property---are legally inherited by the child of the wife of the previous holder.

[Alan H]

This is similar to my situation. I have two uncles (my mum's brothers) who are the last male O'Callaghans of the name in our family. One never married, and the other married someone who already had a daughter and didn't want more children. They are both well into their eighties, so there's no likelihood that either of them will have a genetic son now.

I would love to know what a DNA test on either one of them would show, but I am hesitant to ask them to get tested. I doubt if they would immediately realise that it would only take a scraping from under the tongue (or so I've heard). OTOH, if it is left too long, then eventually it will be too late, for the saddest of reasons. I think I ought to speak to my mum about this. She is the family genealogist anyway, so she would be interested in the results I'm sure.

The burning question that it ought to answer is whether we are all descendants of Ceallachan of Cashel, King of Munster, d.953, or simply, as we already know, descended from a long line of Irish sailors. Whether a Y DNA test could even answer that I'm not sure, but the only way to really find out is to test one of my uncles.

There's no way to know For Sure. Even if we could retrieve a tissue specimen from some guy who died in 953 AD, and it had DNA intact enough to test the various marker haplotypes, you still wouldn't KNOW.

Even if you DID have that tissue, and there's been direct partilineal descent during that 1,000 yeas, well.... it's been over a thousand years. Random mutation could have introduced anywhere from 4 -40 point mutations during that period. Genetic Drift changes haplotypes.

If you have a large number of records of people who can without a doubt PROVE direct patrilineal descent from that EXACT MAN...and then get yDNA samples from those people to establish a pool of genetic variation, well, then you have a start. You'd then apply various parsimonious models of change to the array of mutations that you've got in these proven descendents to come to some sort of "hopeful best fit" hypothesis about Ceallachan of Cashel, King of Munsters actual genotype.

You could then attempt to calculate the probability that your Uncle's haplotype array could be derived from Ceallachan of Cashel, King of Munsters theoretical array.

There's something VERY, VERY important here, which gets glossed over a lot. It deserves its own post.

[O'Callaghan]

There's no way to know For Sure. Even if we could retrieve a tissue specimen from some guy who died in 953 AD, and it had DNA intact enough to test the various marker haplotypes, you still wouldn't KNOW.

Even if you DID have that tissue, and there's been direct partilineal descent during that 1,000 yeas, well.... it's been over a thousand years. Random mutation could have introduced anywhere from 4 -40 point mutations during that period. Genetic Drift changes haplotypes.

If you have a large number of records of people who can without a doubt PROVE direct patrilineal descent from that EXACT MAN...and then get yDNA samples from those people to establish a pool of genetic variation, well, then you have a start. You'd then apply various parsimonious models of change to the array of mutations that you've got in these proven descendents to come to some sort of "hopeful best fit" hypothesis about Ceallachan of Cashel, King of Munsters actual genotype.

You could then attempt to calculate the probability that your Uncle's haplotype array could be derived from Ceallachan of Cashel, King of Munsters theoretical array.

There's something VERY, VERY important here, which gets glossed over a lot. It deserves its own post.

There are undoubtedly people who claim descent from this individual and have a family tree showing that. They of course include the clan chief, who lives in Barcelona, Spain, and they include Baron Lismore of Lismore, Co. Waterford. Also the McCarthy Mor (clan chief of the Macarthys). I don't know if the DNA of any of these people or their close relatives is recorded, and of course we can't get DNA from him,as you point out.

Traditionally, according to the old lineages, everyone whose name is Ceallachain, O' Ceallachain, Callahan, Callaghan or O' Callaghan is descended from him, not to mention all the Sullivans and O'Sullivans, and the MacCarthys and McCarthys as well! The Macarthys are actually the senior line of descent from Ceallachain of Cashel, and the Callaghan line was founded by a grandson who also bore the name Ceallachain.

Some of the Macgraths, McGraths and Kennedys would also be descendants of Ceallachain of Cashel, but those names also have other known separate origins, as Irish surnames are based on Gaelic names that were used as single names before surnames existed, and there were multiple individuals called Maccraith and Cenneidhe in entirely separate tribes who left descendants. No, I don't know which one the Kennedys of Hyannisport (and Co. Wexford) descend from, but I think they know, I understand that they have a very extensive family tree plotted out going a very long way back.

However, it is also said that some clan members were not blood relatives, but their descendants also took the name of the clan, which is the same as the name of its founder, as their surname. So that's where you get people of the same name who are not related. Even then, some (most?) of them would have intermarried with members of the clan who were already related to its progenitor, so that would tend to make many of their descendants related to him anyway.

Putting this in perspective, I read somewhere that there are 100,000 Callaghans in Co. Cork alone. This does not necessarily even rule out the possibility that after 1,000 years perhaps all of them might be descendants of Ceallachain of Cashel. If everyone in Europe is a descendant of Charlemagne, as some maintain, then it seems possible, although I haven't attempted to do any calculations to see if it's feasible.