How far back can AncestryDNA's "Common Ancestors" feature work?

[Albufera32]

Thru Lines are a form of hint - and are as reliable (or not) as every other hint.

Like every other hint, they can be both enormously helpful or frustratingly misleading.

[brigidmac]

I agree you always have to check thru lines with documents

I have some relatives where different thru lines are possible because 2nd cousins in small villages married so we are related to both sides

I think ancestry prioritises thru lines from the ones that have the most documents and numbers of connections ..whereas I'd like to see the more obscure links

In the same way looking for a person on family trees the trees with most records are computer generated first
So if the information is wrong it's perpetuated by being copied by more people

Having said that thru lines have been able to confirm matches for distant relatives . One lady named her son after one man but named another as father on birth record ...DNA showed matches with thru line to the family whose surname he had as a middle name !

[Albufera32]

I have three matches who appear (all three of them) on not just two but three thru lines through three different common ancestors.

The slightly horrifying thing is I rather suspect all three thru lines are correct for all three matches.

[History Lives]

I've been in a similar situation. It essentially makes grouping matches via colour coding impossible for those lines.

[LizzieL]

I have a 10cM match with a person who Ancestry flags up as us having a common Ancestor and correctly predicts he is my 5th cousin once removed. Shared ancestors are my 4 x great grandparents and his 5 x ggp.
I also have a 10 cM match with his son, but Ancestry is not flagging up that we have common ancestors, because the shared Ancestors are his 6 x great grandparents - too many generations for Ancestry's algorithm.
In both cases the individuals are correctly linked to an extensive tree

[History Lives]

I have a 10cM match with a person who Ancestry flags up as us having a common Ancestor and correctly predicts he is my 5th cousin once removed. Shared ancestors are my 4 x great grandparents and his 5 x ggp.
I also have a 10 cM match with his son, but Ancestry is not flagging up that we have common ancestors, because the shared Ancestors are his 6 x great grandparents - too many generations for Ancestry's algorithm.
In both cases the individuals are correctly linked to an extensive tree

Would be great if they expanded this out at a later date; thankfully, most of my brick walls are now further back than this. Interestingly though, the shared surnames feature seems to work back to the 1600s (possibly 1500s?).

[clayton bradley]

Using the shared surnames I found a cluster of 9 Americans, from 23 cMs down to 10 cMs, descended from Cornelis Pieter Jongewaard born in the Zaanstad (Netherlands) 1641. The ancestor of the cluster left for America, mine remained in the Zaanstad and my father came to England in WWII. So it does seem you can go a long way back, in certain circumstances.

[Petros]

I actually have 9 6th cousins show up by common ancestors, most (all?) of whom appear to be genuine, some up to 14 cM

[LizzieL]

Using the shared surnames I found a cluster of 9 Americans, from 23 cMs down to 10 cMs, descended from Cornelis Pieter Jongewaard born in the Zaanstad (Netherlands) 1641. The ancestor of the cluster left for America, mine remained in the Zaanstad and my father came to England in WWII. So it does seem you can go a long way back, in certain circumstances.

Did Ancestry flag this group up as having common ancestors with you? Or did you find them by your own research?