DNA matches on mother's side

[HarryW]

I'm hoping someone will be able to answer my question:

My 4x Great Grandfather on my mother's side (her male lineage) may have been born in a particular area of Wiltshire.   If I can persuade someone who has the same surname in the same location to take a DNA test - is this a valid way of checking whether we are related ?   Or is that too simplistic ?

Harry

[familydar]

Theoretically yes, DNA testing could answer this question, but only in balance of probabilities terms, not yes/no answers, and it could get expensive as you'd probably end up sponsoring more than one test.

Have you already done a DNA test yourself, if so what type(s) and with whom?

Do you have a candidate in mind for the test you are proposing?  Are they male or female?  Do you know their lineage and does it dovetail with yours?

If you can give Rootschatters the answers to these questions one or other of us could probably give an opinion on how best to proceed.

best wishes
Jane :-)

[HarryW]

Thanks for the response.   I was only expecting to get a balance of probability.

To answer the questions:

Yes I have had my DNA tested (Ancestry)

I don't yet have a firm candidate as there are several possibilities.   I need to be clearer and have more confidence of my research before venturing further.

Harry

[Seaton Smithy]

Hi Harry

Something to keep in mind is the probability of matching cousins at different generation levels.

If you were looking at someone who descended from your 4x great-grandparents who was the same generation as you, you'd be looking at 5th cousins.  If you were looking at someone who descends from a sibling of your 4x great-grandfather, you'd be looking at 6th cousins.

You are really only guaranteed to match someone down to 2nd cousin level.  For 3rd cousins the probability of matching is around 90% (so still quite high), for 4th cousins the probability of matching is only around 50%, for 5th cousins around 10% and for 6th cousins less than 2%.

That's not to say you won't match with a 6th cousin (or greater), but that the chance of randomly matching any 6th cousin who happens to test is negligible.

Given that you are looking to find a match with a specific surname from a specific location, you might consider whether y-DNA might be more suitable in this situation.  A y-DNA is generally a less effective way to randomly find relatives than autosomal testing, but might be effective for your specific goal.

Sometimes y-DNA projects already exist for particular surnames and/or regions: https://www.familytreedna.com/projects.aspx

Of course, you would need a male relative of your mother, a brother, son of a brother or a male line cousin.

Testing for y-DNA is more expensive than autosomal tests but in the long run might be better value than paying for random people with the same surname to take the autosomal test.

[HarryW]

Thanks for the replies - I'm a bit clearer with my approach now (if I need to).

Harry

[medpat]

When I did my DNA on 23andMe one of my nearest relatives shown was an American. I emailed him with my pedigree list but the names didn't mean anything. He then told me his maternal grandparents were from UK and named my home town as their birthplace so I asked for their names. I already had them on my tree, last entry a 1901 census.

If he'd found his gt gt gt grandmother Ann's marriage and therefore her maiden name he would have hit one of my pedigree names as my gt gt gt grandmother Harriet was Ann's sister so we share our 4th gt grandparents. This proved all my paperwork from late 1700s up to present day for his direct family as well as mine.

I don't understand all the theory but I've successfully gone back to a 5th cousin but that because he still had the family name and my link was backed up by linking with another distant cousin of mine (we shared a gt gt grandmother who was from his family).

Hope this helps you understand how it actually links up relationships.