A Donegal McFadden modal?

First, some basics:

• M222 is a DNA marker unique to one man who lived a couple thousand years ago and his direct male descendants.  All men in this group are referred to as M222+.  One of those descendants is believed to have been Niall of the Nine Hostages.  About eight percent of Irish men and more than 20 percent of men from the northwest of Ireland have this marker and the vast majority are believed to have a common paternal-line ancestor who lived around the time of Niall.  A significant percentage of Scottish men are also M222+.
• In terms of Y-DNA, a modal haplotype is a distinctive set of markers that define a group of men who share a common paternal-line ancestor.  For example, it is possible to assume that some men are M222+ based on the results of a simple 12-marker Y-DNA test even though M222 is not one of the markers tested.  These assumptions cannot always be made and are not always correct, but generally have a very high degree of accuracy.

I have split the results of the FTDNA McFadden project into several categories in order to help show the relation or non-relation between the participants.  These categories are based on haplotype.  It’s important to note that men who have the same basic haplotype can still be unrelated.  The R1a1a haplotype, for example, is thousands of years old.  Hereditary surnames only came into use about a thousand years ago.  So two men with the same last name who are both R1a1a may still be from completely different lines.  Looking at the R1a1a group in the McFadden project, it is a near certainty that kit 162088 is not related to anyone else in a meaningful way.

On the other hand, everyone in the group designated as “R1b1a2 (M222+ Group 2)” does appear to come from the same line and I’d like to examine them further.

Three of the men are closely related.  Kits 216073 and 28329 are third cousins.  Kit B4058 is the nephew of 216073.  Interestingly (and slightly off-topic), that means 216073′s value of 10 at DYS426 is likely unique within this haplotype.  The other two kits have no known connections.  Kit 191217 is from Scotland, but traces his line to Ireland.  Kit 137736 is descended from pre-famine American immigrants from Donegal.

At first glance, 137736 appears to have too many differences from the rest of the group (aka “genetic distance” or GD) to assume there is a relation.  In fact, the rest of the group has a lesser GD with several people who have different surnames and likely no meaningful connection.  So what evidence is there that this kit is of the same line?  To answer that, we need to look at the M222 modal haplotype.  The M222 project at FTNDA has almost a thousand participants, which represents a legitimate population sample.  On the results page of that project, you can find the M222 modal by looking under the category “0. M222″ and following the “Mode” line.  The numbers listed there represent the most common values for each marker among the kits in the project.

Each of the kits in the McFadden M222+ Group 2 has a number of differences with the M222 modal.  The importance lies in those values that are different from the M222 modal, but shared within the group.  These “off-modal” values are DYS458=16, DYS449=31 and CDYa=35.

I went through all of the results in the M222 project and came up with the following stats:

• A value of 16 or lower at DYS458 is found in 87 of 931 kits (9.3 percent).
• A value of 31 or higher at DYS449 is found in 170 of 931 kits (18.3 percent).
• A value of 35 or lower at CDYa is found in 23 of 902 kits (2.5 percent).

The reason I counted values that were 16 or lower at DYS458 is because the modal value there is 17, which means a value lower than 16 likely would have been 16 at some point.  The number of total kits for CDYa is lower because fewer people have tested the necessary 37 markers to determine that result.

To really drive home the point I’m making, no kit other than my own out of 900 in the M222 project had all three of these values.  So the significance of several men with the same last name sharing all of these values is obvious.  The two McFaddens in the group that have tested to 67 markers also share an additional off-modal value in DYS557=15.  I am proposing that the combination of these four values may indicate a distinct haplotype for the McFaddens of Co. Donegal.

It should be noted that there are apparently a handful of men with the Cowan, Ewing and Dougherty surnames that also have these results, so more McFaddens with ties to Donegal are needed for testing in order to flesh out this theory.

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