How far back can you triangulate DNA?

Question

I have been trying to confirm/triangulate all my ancestors and have hit a major roadblock. My 5th great grandfather (my mother’s fourth g grandfather)  was a loyalist who moved to Canada and married a French Canadian woman. I cannot triangulate DNA past him (I can for his wife) and appear to have no autosomal DNA from either of his parents. This could be an NPE, but  I don’t know how likely that is. The loyalist’s daughter (my 4 great grandmother) was named after his sister and both siblings nearest her have been able to prove that he was their father. Unfortunately, I have only been able to test mine and my mother’s DNA to try and confirm. Also worth noting: French Canadians are somewhat endogamous...my 3rd g grandparents on this particular line are second counsins through other lines.

My question is: is it possible that we just didn’t receive DNA from him? How far back (generally) would you be able to confirm DNA matches?

Answer 1

Yes, it's possible that you just didn't receive any DNA from him. Generally it's difficult to confirm back further than 4th, possibly 5th cousins using auDNA. And endogamy can make it extremely difficult--because it's so hard to figure out which of the multiple shared ancestors was the source of the shared auDNA. If you want to go back further than 4th cousins you should consider using yDNA, if you can find appropriate men to test.

Answer 2

Yes, it is very possible that you didn't receive any of his DNA....  the best way I have figured out how to explain how this could happen is like this....

Lets say you have a deck of cards that is representing your parents genes, 50% your mothers and 50% your fathers.

Now you shuffle the cards and deal yourself 23 cards or "genes"

Now you take all the cards back shuffle again and deal 23 cards or "Genes" to your sibling .....shuffling and repeating this for all your siblings.

So.... there will be cards that you were dealt .... that none of your siblings were dealt.....as well as your siblings will get cards that you didn't get.

AND there will be cards that you and your siblings received that were the same.

Once this shuffle and deal is repeated over generations....the more generations between you and your ancestor..... the smaller and smaller chances you'll actually draw their card

Comments

I can confirm that.  I have an important lineage with descendants that I don't match AT ALL.  Then I got my sister and brother tested - and my sister matches well, and my brother matches perfectly!  If they match your full siblings, then they match you!

Of course, this points out that having your parents and grandparents tested is more important than your own test.  One or two less shuffles.

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Here, here, Rob!  It is so important to remind people to always test their oldest living relative first.  So if you've got parents -- or better yet grandparents -- still alive, do yourself a huge favor and test them while you can!  I was fortunate to be able to test both of my parents.  Now I work solely from their kits.  They are both only children, as was one grandmother, so I am lucky that autosomal testing came along in their lifetime!

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I wish I had known this a decade ago.

Time to find a shovel :-p

Answer 3

I've been able to get back as far as ten generations.  it doesn't happen very often, and so far I've only located it when it is someone that ends up triangulating on a portion of a larger segment I share with a more recent cousin.  I have some Loyalist cousins (my ancestor was the sole Patriot) that went to Nova Scotia.  I just recently located and made the connection, as my Patriot ancestor has tons of descendants that have tested and I have a lot of mapped segments from him.

As others have said, there's a good chance you didn't get any DNA from that person...