CASH v. LETITIA

DNA testing - Cashel with the Letitia branch.
For background see DNA testing for the Blennerhassett problem.

This page is about the tests done to prove or disprove the Theory of our descent from Letitia Blennerhassett of Tarbert.

The results (below) say that the Letitia theory is not true. We are not closely related to Letitia Blennerhassett of Tarbert.

Groups

We compare individuals from the groups defined here.

This page will compare:

CASH v. LETITIA

Total segment matches (minimum segment 9)

We start by considering total segment matches, using minimum segment size = 9 cM.
9 cM is generally considered significant.

We compare our family with the Letitia Blennerhassett family.

This looks really bad.
We have done one to one comparisons. And we get only four matches above 9.0 cM, with the highest rounding to 11 cM.
Compare this with the equivalent table for the Baronets theory, which is full of green and blue level hits, going up to 24 cM.
Also, the matches above are not where they should be. The theory says we are closest to REV. But the matches are in ED.
In fact, all these matches are in the Griffin family, which has various Catholic Kerry ancestors. Probably the matches are not through the Blennerhassett line at all, but through some other Kerry line.
These matches are not really evidence for the Letitia theory, and the lack of REV matches is strong evidence against it.

Total segment matches (minimum segment 7)

Let us try (as some sites do) reducing the minimum segment size and looking at total segment matches.

Here is total segment matches using minimum segment size = 7 cM.

With this metric (minimum segment 7 cM), more borderline matches emerge, including some with REV.
But the matches are not hugely convincing.
Compare with the 7 cM table for the Baronets theory, which continues to look much stronger.
We have done a lot of samples to get such weak matches.
The Letitia theory predicts stronger matches with REV than with ED. And this is not what we see here.

Largest segment in match

We now take a wider look at the data by showing for every match, what is the largest segment.
Largest single segment in match, in cM.
Small segments can happen by chance. Large segments much less so.

CASH borderline matches REV and ED.
Our Letitia theory predicts much stronger matches with REV than with ED, though. And this is not what we see here.
CASH.23 and REV.4 is a fake match:
- CASH.23 has a match of 8.9 with REV.4. Sounds good, except the Cashel line goes through the mother of CASH.23, which is CASH.5, and she only has a match of 5.6 with REV.4. Conclusion: The DNA match comes through the father of CASH.23, i.e. just by chance. You can get 8.9 by chance.
REV.11 is a fake match:
- REV.11 looks like the best all-rounder, with modest DNA matches, but lots of them. However, the link of REV.11 to Blennerhassett is through his mother, who is REV.12, who does not have these matches. So these matches are by chance - they come through REV.11's father's line.
- REV.11 is arguably the best all-rounder sample of all REV and ED samples. And we know its matches are irrelevant and only happened by chance. This shows how bad the Letitia theory is.
Compare this with the Largest segment table for the Baronets theory, which is much stronger.

Estimated MRCA

If there is a segment over 5 cM, Gedmatch estimates the number of generations to Most Recent Common Ancestor (MRCA).
This is an estimate from the DNA, not from the family tree.
Gedmatch can give different estimates depending on the minimum segment length you pick. We use the closest estimate, which is the estimate given under minimum segment 5 cM.

The CASH link to ED and REV seems a bit stronger under this metric.
But the results are still fairly weak.
Compare this with the MRCA table for the Baronets theory, which is dramatically better.
The Letitia theory predicts a closer relationship with REV than with ED, and we do not see that.

Postulated cousins

Now we consider, under the Letitia theory, the postulated cousin relations of CASH with REV and ED.

If George Cashel is the son of Letitia Blennerhassett of Tarbert, then these would be the postulated cousin relations:

Here are the Gedmatch estimated MRCAs:

There is no match with the postulated cousins. The Letitia theory looks false.

Here are the largest segments:

There is no match with the postulated cousins. The Letitia theory looks false.

Real cousins v. Postulated cousins

Let us write out the entire list of results for real cousins versus the same list for postulated cousins, separate into lists for each type of cousin, and sort the lists, to see if the postulated has the same pattern as the real.

This is where the Letitia theory really looks false. The below shows that for we should already have got some great hits for CASH. We should have a bunch of strong "blue" hits already. But we have basically nothing. The Letitia theory is false.

Here are the lists, for each type of cousin, of largest segments for real cousins versus the same list for postulated cousins (for CASH crossed with REV and ED).
We start at "4.0" cousins (there are no closer living postulated cousins).

The Letitia theory looks false. 4.0 and 4.1 cousins should have much stronger matches.
I got all the 4th cousins: When I started the DNA testing, the closest of all living relations of the two sides (according to my theory of cousin relationship) were 4th cousins no times removed (4.0). Two living on my side. Three living on the Letitia side.
After much work, I managed to get all 5 samples, and could do all 6 comparisons. This, of all places, was where the theory should have been proved. And nothing matched at all. All 6 matches are shown above under 4.0. The highest is 5.3 cM. Just nothing.
Now maybe we could explain this. The two on my side are siblings, and that line could have got very little Blennerhassett DNA by chance. So let us now look at the 5th cousins.

It is the 5th cousins that really makes the Letitia theory look false.
There is just nothing here.
5.0 and 5.1 cousins should have much stronger matches.

Our best matches finally show up here, for postulated 6th cousins.
But why are they showing up here and not for 4th or 5th cousins?
When we look at what they are, all these matches are to the Griffin family, which has various Catholic Kerry ancestors. Probably the matches are not through the Blennerhassett line at all but through some other Kerry line.
This branch is a long way off from Letitia of Tarbert. Whatever they are evidence for, these 6th cousin matches are not really evidence for the Letitia of Tarbert theory.

Conclusion - The Letitia theory looks false

We have enough samples now to declare that the Letitia theory looks false.

After many hundreds of comparisons, we got some alright (but not great) matches of CASH with ED, and some even weaker matches with REV.
But they are in the wrong branch (ED not REV). And they are distant (6th) cousins not close (4th) cousins. And they are not even great matches. So whatever this is evidence of, it is not evidence of the Letitia theory.
If we look at all matches the pattern is fairly random, and suggests the Letitia theory is false.
The total failure of 4th cousin matches also suggests the Letitia theory is false.