5th - 8th cousins - several "shared matches" with one person

[Lisa in California]

Hi:

I received my DNA results late last year and I check the matches a couple of times a week; I am determined to find distant relatives from my brickwall ancestors. 

When I check the matches that are 5th - 8th cousins, understandably, our "shared matches" almost always result in 0 matches.  However, a few minutes ago, as I was checking shared matches with another 5th - 8th cousin match, there are 7 results.

Apologies for what could be a silly question but what would be the reason for almost all of my 5th - 8th cousin matches to not share any matches and then have one that has so many matches?  (All of these results are 4th - 6th cousins and closer.)  One reason could be that more descendants of this line took DNA tests than my other lines, but are there other reasons, please?  Thank you for any guidance.  Lisa

PS  I used an Ancestry DNA kit; I am Canadian with English and Irish ancestors, in case it makes any difference.

[davidft]

The reason could be because of the shear number of cousins you have at the 7th or 8th cousin level. To explain this blog article may help

http://blog.kittycooper.com/2016/07/how-many-cousins-share-my-5th-grandparents/

from that you can see that at the 7th cousin level if each generation had say 4 children you would have 65,536 7th cousins. Bearing in mind that during the period covered families were often very large say 8 or more children then you would have over 2 million 7th cousins.

Needless to say most of your distant cousins will not have tested and the ones that have the chances of you having shared matches will be very small because of the shear number of people involved and the relatively small proportion of DNA you have from any one ancestor 8 generations back.

Turning to why you suddenly have 7 matches with another 5-8th cousin match I think the most likely explanation is that is a match with someone who has several close family members who have also tested and so naturally you match with them too.

Just some initial thoughts and no doubt others will be able to add more

[Lisa in California]

"...Turning to why you suddenly have 7 matches with another 5-8th cousin match I think the most likely explanation is that is a match with someone who has several close family members who have also tested and so naturally you match with them too."

Thank you davidft.  I didn't think of that possibility; that makes a lot of sense.

I will read the article now.  Thank you very much for referencing it.  While I've been involved in genealogy a long time, I am still very new to DNA and I've not taken the time to learn about it.  I appreciate your reply; you've been very helpful.  Lisa

[IJDisney]

I had a similar situation, where I found a set of about 12 distant cousins all coming up as shared matches. It turns out they all descend from an English man who emigrated to Salt Lake City, Utah in the 19th century and was a Morman. Since that religion generates an interest in  genealogy, it isn't surprising that a greater number of his descendants should have had a DNA test done, then might be expected for the average.

Maybe your clutch of cousins is due to something similar?

[Lisa in California]

Thank you for your reply, lJDisney.  Actually, my story is somewhat similar.  My ancestor, George, was born in England and settled in Canada c1869.  George had 11 children who survived childhood.

About 20 years ago, I located a distant cousin from one of George's children.  She had been researching her family and over the years had located about 10 people, all living in Canada and America; each person was a descendant of George's children.

I don't know why we were all interested in genealogy; there was nothing noteworthy to encourage descendants to learn more.  At the time, I thought it was so unusual to have so many distant relatives researching (and wishing my other lines would do the same!).  Perhaps either they or their children are some of the ones who took DNA tests.

Thank you for suggesting your idea; this is all starting to make sense.    Lisa

[diplodicus]

I too have one Mormon ancestor who emigrated from West Wales (as did many people in mid-nineteenth century). some of his descendants are among my "closest" matches and so far I have linked twenty-nine people  with several more to document.

Once you start to cross-reference the matches, the number starts growing. This is because of ancestry's matching process whereby with your 5th to 8th cousins, only matches to 4th to 6th cousins are displayed.

Fr'instance: I have a 4th to 6th cousin Tom who matches to another cousin Dick.

But when I look at Dick's matches, he is shown as matching to Tom but also to Harry.

So, I can now connect Tom to Harry even though they are not shown as a match in Ancestry.

One word of caution: there is always a possibility of there not being a connection, especially in small rural communities where 2nd cousins can marry, sometimes without realising the connection.

A spreadsheet becomes a real necessity and it soon starts to get rather large!!!

p.s.   I still can't find our common ancestor even though I know exactly where his family lived (very, very near my known direct line). This is where Gedmatch.com or Familytreedna.com become really useful provided you can persuade the other people to upload their results (for free by the way).

[Lisa in California]

Once you start to cross-reference the matches, the number starts growing. This is because of ancestry's matching process whereby with your 5th to 8th cousins, only matches to 4th to 6th cousins are displayed.

Hi diplodicus:

Thank you for the additional explanation; I didn't know about this aspect.

While I started to write contact information on index cards (one for every ancestral surname), a spreadsheet sounds like a better idea.

I did upload my results to gedmatch, but didn't find anything helpful.  I should look again as it's been a month or two since I last looked.

I hope you are able to find your common ancestor; I know the feeling.       Thank you for your reply; it is quite helpful.  Lisa

[diplodicus]

I did upload my results to gedmatch, but didn't find anything helpful.  I should look again as it's been a month or two since I last looked.

I think Gedmatch requires a lot of learning and comes into its own when you recognise someone there who is also someone you recognise from Ancestry. You can then use the "People who match one or both kits" function to identify others who share the same lump of DNA.

If (big if!) you can find one of these people in your tree as well, then you can now label that piece of dNA as "Smith" or "Jones" or even "Trump"

[Lisa in California]

Hi diplodicus:

I did find it a bit difficult to understand (I still don't know a lot)  but it is interesting.  In the one-to-many comparison, the first ten results are from two of our well-researched surnames, so while it is interesting to see the names, it would be great to come across some of the people with whom I've been corresponding but have not yet found proof that we are distantly related.  (I hope that makes sense.)

Actually, looking at the results again, I will give it another go - perhaps this time I might find something helpful. 

No, no labeling any Smiths or Jones or Trumps for me, thank you.     Thank you again for your help and interest.  Lisa