Update on Lineage II - the Gleeson's of North Tipperary

There are now 57 participants within the project who have been allocated to Lineage II. Of these, 36 (63%) have done some form of SNP testing (i.e. either the Big Y test, a single SNP test, or a SNP Pack test). This high level of advanced testing has allowed us to construct a "genetic family tree" for the group based on their SNP markers. This is referred to as a Mutation History Tree (MHT) in previous posts, because it is based on mutations in both the SNP markers and STR markers (the two types of DNA marker on the Y-chromosome).

The Branching Structure of the Genetic Family Tree

Overall, the structure of the genetic family tree has not changed very much over the past 4 years, indicating that the project has probably achieved a degree of maturity that will remain relatively constant moving forward.

However, since the previous update, FTDNA has introduced several new features, including the Time Tree and Group Time Tree. These new tools include a very useful graphical representation of the genetic family tree for Lineage II, showing the branching structure, the surname of each test-taker on each branch, and their Most Distant Known Ancestor on their direct male line. (These Time Trees only include participants who have done a Big Y test and who have adjusted their Settings to allow the public display of their Y-DNA results, so only 16 of the 36 project members who have done a SNP test appear in the sub-A5631 section of the Group Time Tree below - see also Note 1 below.)

Group Time Tree for Lineage II 
showing the branching structure of the genetic family tree
below the branch characterised by the SNP marker A5631
click to enlarge

The branching structure is very similar to that described in the previous iteration (version 4) of the Mutation History Tree (MHT) for Lineage II. The only notable difference to the branching structure is the addition of one new branch, characterised by the SNP marker FT89811. This sits below the pre-existing branch Y16880 (i.e. the new branch is a "son" of Y16880). Note that the timeline for the Group Time Tree diagram above runs from left to right (distant to recent), whereas the timeline in the MHT diagram below runs from right (distant) to left (recent).

Gleeson Lineage II MHT version 4 - download pdf document here
(click to enlarge)

Age Estimates for the Branching Points

The Time Tree also includes much more accurate age estimates for the various branching points within the genetic family tree. It is interesting to compare these new age estimates with those from the previous update and this is summarised in the table below. These revised age estimates have some important implications. (Note: these age estimates are described as TMRCA estimates, where TMRCA means Time to Most Recent Common Ancestor).

• Firstly, the new estimates come with a Central Estimate surrounded by a 95% Confidence Interval. What this means is that there is a 95% probability that the real age estimate falls somewhere between the lower and upper levels of the Confidence Interval. Put another way, we will be wrong 5% of the time (i.e. 1 in 20 times). 
• In addition, these Confidence Intervals are very large - usually in the range of +/- 200-500 years, which means that the real / actual age is estimated to be somewhere within a 400 year to 1000 year window. This lacks the precision we would desire from a genealogical perspective. Ideally we would want an age estimate that was +/- 10 years. But unfortunately, these age estimates are as accurate as they can be (given the limitations of the technology), and are likely to remain "crude" from a genealogical perspective. Even if we had several thousand Big Y test-takers, the range would not be reduced to less than +/-50 years (which is still not precise enough for genealogy). In short, these estimates will always remain crude, and we should take them with a very large pinch of salt. Furthermore, they will change (usually slightly) over time as they are regularly revised with new data from new Big Y test-takers.
• Lastly, we previously thought that the SNP marker A5631 was the overarching SNP marker for all the Gleeson men of Lineage II. But the revised central estimate for for A5631 is 658 AD, well before the time that surnames emerged in Ireland, and in addition the upper limit of the 95% Confidence Interval is 952 AD which is a little early (but possible) for the emergence of the Gleeson surname. So, based on these revised estimates, it would seem more likely that A5629 is the overarching SNP marker ... but this leaves us with having to explain why there are about 8 Gleeson men on the adjacent branch BY14197 (who share a common genetic ancestor born about 1106 AD). Are they a parallel branch that arose independently, but there was a surname switch to Gleeson some time before 1106 AD? or do they share a common ancestor with the rest of Lineage II who bore the name Gleeson (or rather, its Irish language equivalent)? in which case, the current age estimate for A5631 is out by a few hundred years? Only further Big Y testing will help refine these age estimates and help address this question.

Age estimates (TMRCA) for the common ancestor of each branch 
comparing 2020 estimates (using the SAPP programme) 
with April 2024 estimates (using the Time Tree estimates)
click to enlarge

Which branch do you sit on? & Who are your closest matches?

Not everyone in the project has done SNP testing (e.g. the Big Y test) but it is still possible to allocate many of them to a specific branch of the genetic family tree based on the fact that a) they are a known relative of someone who has done SNP testing, or b) they have a very similar STR marker signature (i.e. their row of numbers on the public Results Page) to that of someone who has done SNP testing.

The diagram below is the Group Time Tree diagram overlaid with kit numbers of 35 of 38 project members who have allowed public display of their results. (1) To see who your closest matches are, simply look for your kit number in the diagram below. If you don't see it, email me (mauricegleeson AT doctors.org.uk).

Group Time Tree for Lineage II 
showing which people sit on which branch
(kit numbers are from the public Results Page)
Green highlight = SNP tested; Yellow highlight = not SNP-tested
click to enlarge

All the people on your branch share the same common ancestor. This ancestor passed down your branch's defining SNP marker to all of you. The age estimate of the SNP marker indicates roughly when he was born. There may be certain individuals on your branch with whom you share a more recent common ancestor than the overarching common ancestor for all the people on your branch. Contacting the other people on your branch (and sharing genealogical information) could reveal a connection that allows you to break down a Brick Wall in your own family tree.

Conclusions

As more people join the project and do Big Y testing, the branching structure within the genetic family tree will become more fine-detailed, and the age estimates of the branching points will become more refined. 

It would certainly help if more people allowed their (automatically anonymised) Y-DNA results to be publicly displayed on the public Results Page (but this is entirely up to each individual to decide). (1) Doing so would allow these updates to be more informative for everyone within the project and would optimise the potential benefit of the Y-DNA test that everyone in the project has undertaken.

In time, we may be able to identify which branch came from where, and this could be really helpful information for both new and existing members. If we were able to associate a particular branch (or SNP marker) with a particular town, or townland, or barony within a county, this would certainly be of great assistance in focusing your research in the surviving documentary records.

Maurice Gleeson

Apr 2024

Big Y Block Tree for Lineage II
showing the various branches of the genetic family tree
and the number of SNPs in each "SNP Block"
click to enlarge

Notes & Links

1) If you want to change your settings so that your (automatically anonymised) Y-DNA results appear on the public Results Page and the Group Time Tree, do the following:

1. log in to your FTDNA account
2. click on your name (top right)
3. click on Account Settings
4. go to the tab entitled Project Preferences
5. scroll down to Group Project Profile and click the button so that it is in the ON position