Saturday, 10 June 2017

DNA Diary – Clynch update


Perhaps you remember from my recent posts – The Clynch Connection and The Clinch family of Aurora, Illinois – I concluded I’d probably need a DNA match to prove my Dad’s relationship to the Clinch family of Aurora. Well, the good news is I’ve now ‘met’ a living descendant of Martin Clinch and she has already taken a DNA test.  

You may also remember, Martin Clynch, along with his supposed siblings Edward and Mary, left their home in Blackrath and Athgarvan, in 1854, for a new life in America. I’m nearly certain Martin and his siblings were related to Dad’s second great-grandmother, Anne (Clynch) Byrne, who lived in the same townland in Co. Kildare. Anne could even have been their sister, a theory being they were all the children of Patrick Clynch and Catherine Murphy, from Athgarvan.

My prospective ‘cousin’ agreed to upload her DNA results (for free) to GEDmatch, a third-party company providing tools for genealogy research. We were then able to compare her results with my Dad’s. Sadly, however, they don’t match. For matching purposes, it is generally accepted ‘cousins’ should share at least one matching segment of 7cMs or more, and they don’t. 

When I lower the thresholds though, they do share several smaller segments, signifying a potential relationship. Then again, Ireland is a small country, and people generally descend from same limited gene pool. So, small segment matches are to be expected, even if people are not related in a genealogical timeframe. Plus, this match is not at all convincing.

Dad’s matching DNA segments with a Clynch descendant 

You get 50% of your DNA from each parent, about 25% from each grandparent and on average 12.5% from each great-grandparent, etc. You have 32 third great-grandparents, so receive an average of just over 3.125% (1/32) from each one. But, DNA is inherited randomly. The deviation from average increases with every generation, so it’s possible to receive far less than ‘average’ from any individual ancestor. And, the odds on two descendants inheriting the exact same section are obviously even higher.

Source: ISOGG Cousin statistics

If our most recent common ancestors were Patrick and Catherine Clynch, Dad and our potential cousin are fourth cousins, once removed. Statistics show less than half such cousins show up as a DNA match, i.e. there is a 52% probability of no detectable DNA relationship. And, it’s quite possible our most recent common ancestors were even earlier than Patrick and Catherine, making the likelihood of matching even more remote.

But, there is one thing in our favour - Martin Clinch of Aurora has many descendants, so there’s a chance one of them may share Clynch DNA with Dad. Maybe someday I’ll meet a match.

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© Black Raven Genealogy 

2 comments:

  1. Following your DNA saga with interest, as I dig deeper into my DNA results via GEDMatch. Thanks for sharing that valuable cousin statistics table from ISOGG>

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  2. Thanks Marian, I'm still waiting for that lucky break with our DNA kits. I suspect it will become easier and easier once matches are identified, but getting a start is proving difficult.

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