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 scrape in with two borderline matches above 9 cM.
Also, the matches are not where they should be. The theory says we are closest to REV. But the matches are in ED.
They are both in the Griffin line, and probably that is the line the match is through, not through Blennerhassett.
Compare this with the 9 cM table for the Baronets theory, which has some great hits.
There are borderline matches of 8.9 and 8.6 and 8.5 cM with REV, which would round up to 9 cM. However, analysis shows that both the 8.9 and the 8.5 are fake matches, that happened by chance. So we have an 8.6, but this hardly changes our analysis.

Best match found

The best match for the Letitia theory is this 9.4 cM match of ED.5 and CASH.21.
ED.5 is in the Clifford line, descended from Mary Blennerhassett, sister of Rev. John.
CASH.21 is a descendant of Blennerhassett Cashel.

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.

Matches for CASH with LETITIA emerge:

With this metric (minimum segment 7 cM), more borderline matches emerge, including some with REV.
But the matches are not hugely convincing.
Compare this with the 7 cM table for the Baronets theory, which is 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.
One of the best matches, CASH.23, 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.
One of the best matches, REV.11, is a fake match:
- REV.11 looks like the best all-rounder sample, 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 sample of all the above 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 is 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. The Letitia theory is false.

The Letitia theory looks false.
5.0 and 5.1 cousins should have much stronger matches.

Our only matches show up here, for postulated 6th cousins.
They are borderline matches. Most likely not through the Blennerhassett line.

Conclusion - The Letitia theory looks false

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

We have some borderline matches of CASH with ED and REV.
We got just above 9 cM, but only after hundreds of comparisons. And they are in ED. The matches should be in REV.
If you look at the MRCA, CASH seems to weakly match ED and REV. But the numbers are weak.
If we look at all of our matches the pattern is very random, and strongly suggests the Letitia theory is false.
The total failure of 4th cousin matches strongly suggests the Letitia theory is false.