pedigree collapse

[Talacharn]

I have a DNA link at 53.3cM . Largest 19.6 . Gen 4.04.
DNA Painter says: Assuming no pedigree collapse or endogamy and that you're related in just one way, the *furthest* back you might need to go to find common ancestors for a match of 53.3cM is 8th-Great-Grandparent or generation 11 on your pedigree chart. The connection could be closer.

I know the link is on my paternal side and would like to establish where that person fits. My paternal grandparents were first cousins. Their parents I believe were also first cousins, though I am still trying to confirm. How does that impact on the predictions?

[Glen in Tinsel Kni]

Building the tree is the way to establish where they fit regardless of predictions and other factors such as pedigree collapse, in many cases going back to the early 1800's and beyond can uncover inter family marriages & multiple relationships between individuals.

[Biggles50]

Where pedigree collapse occurs or in your case is known about, the likely outcome is probably a larger amount of Shared DNA being inherited which skews relationship research.

We cannot be definitive with relationships as DNA inheritance is a random process.

DNA Painter has a database build around what users have submitted to them and in each case there is a wide range of Shared DNA for a specific relationship.

Hence why they include caveats on generational distance possibilities.

Look at the Shared Matches and see if there are any clues there.

I hope the test is with Ancestry and if it is then subscribing to Pro Tools will enable the cM that the 53.3cM match shares with each of the Shared Matches between the two of you and this in turn will aide tree building and incorporating the Shared Matches in the tree.

It took me building a tree of 900 and another of 700 for me to solve my big DNA puzzles, so it can be done, the issue just needs to be worked.

Good Luck.

[SouthseaSteel]

When there is just multiple relationships (pedigree collapse) rather than societal endogamy then the shared DNA between any two relatives is simply just the sum of the various relationships that exist.  So I can easily imagine in your case, you and another not only being first cousins but 2nd cousins also, and may be even 3rd cousins also.  The total shared DNA and indeed the range values is calculated by adding all these relationships. This obviously increases the shared DNA you will have with somebody who at face value is just a 1st cousin.

[LizzieL]

I have an odd case which you might think of as pseudo-endogamy. I have a 406 cM match across 18 segments (Longest segment 71 cM) with a second cousin. Rather high you might think. No true endogamy in the family. But my grandfather and this match's grandfather were identical twins. So from the DNA point of view it as if my grandfather had two wives, my grandmother and my match's grandmother, and our DNA relationship is equivalent to half first cousins.

[Talacharn]

Thanks for your comments. I delayed responding as I needed to dig a little further. My DNA test was with LivingDNA and unhappy with them, once uploaded to GedMatch I deleted my sample. At some point I will test with Ancestry.

The person I want to place in my tree (A) has not responded to my attempts at contacting. There is traveller/gipsy DNA linking the families in one area, through 1 child and possibly 3 children and the same mother. To one of the descendants (B), I know there is a stronger DNA link between A and B at Shared 159.9 . Largest 58.6 . Gen 3.24 . Generations Difference 0. I do not link through DNA to (B), so I assume it was not found as I have a paper trail.

DNA Painter says to (A) I am: 30% = Half 3C . 3C1R . Half 2C2R . 2C3R, then up to 7C. From my paper research, the link should be 2C 1/2R, so DNA seems right considering what you say, but with such common names I cannot take those few lines in either direction. On GedMatch, (B) has a GEDCOM with 7 people going back to grandparents with all hidden, and also did not respond to my attempt at contacting, which I find frustrating.

GedMatch allows me to compare and list those shared by both and with (A)  there are 10 individuals. The highest has Shared 27.6 . Largest 11.0 . Gen 4.5 . Generations Difference 0.0
Knowing (A) is a match on my paternal side, can I assume all 10 are related on my paternal side?
What does Gen 4.5 signify?
When the Generations Difference is 0.0 does that mean the same level on my tree?
And how accurate are these?

When I compare shared matches between (A) and (B) there are 324 individuals with only a few tested twice. The largest is Shared 546.1 . Largest 97.1 . Gen 2.4 . Generations Difference 2.3 and the smallest Shared 20.1 . Largest 12.5 . Gen 4.7 . Generations Difference 0.4. Many are names I associate with travellers and several seem to be of Irish descent which makes sense.

[LizzieL]

Info on Generations on Gedmatch

"In the generation listing your parent or child is 1, an aunt or niece is about 1.5, a grandparent is 2. For cousins subtract one from the number, so if it shows generations of 4, the suggestion is 3rd cousin. Kitty Cooper's recommendation is to follow up with anyone who is 4.5 or less. Start with the closer ones. Accuracy in autosomal matching declines after 3rd cousins."

Ao I guess 4.5 would be between 3rd and 4th cousin.

[LizzieL]

Though this generations thing is quite variable. I have 2x half 3rd cousins once removed (not sisters to each other but 1st cousins - their fathers were brothers) one is generation 3.86 and the other 4.30.
To each other they are generation 2.1, which sounds about right as they share one set of grandparents

[Talacharn]

Thanks LizzieL for the explanations. Having contacted the most interesting with no response I gave up. I have now started again with those around Gen 4.0 as from their lists they seem to be from my maternal side, and I do not know where they fit.