23, 24, 25 of 25 matches with no common surname

[sailingdeacon]

On one y-dna information web site this is stated: "Matches of 23/25, 24/25 & 25/25 – there is a high probability that participants who share a surname share a common ancestor."

Why is it necessary that they share a common surname? Or is the probability somewhat less if there is no common surname?

[Jim Denning]

On one y-dna information web site this is stated: "Matches of 23/25, 24/25 & 25/25 – there is a high probability that participants who share a surname share a common ancestor."

Why is it necessary that they share a common surname? Or is the probability somewhat less if there is no common surname?

because if you buy a ford at a ford dealer you assume they can fix it better then a jaguar dealer. they assume it is easier to trace with a commom surname they are probably right.
i mean if you start your tree you want to think no one changed the surname for reasons unknown. maybe you wouldnt start your treee.

when you test other members with the surnames common lines emirge and lines take shape which close haplotypes. this allows you to take your possition in this line and match paperwork and find the common ancestor

[Jason]

Sometimes genetic matches can be random, and do not necessarily indicate common ancestry. Sometimes genetic matches can stretch back before the time of surnames, and so there could be a common ancestor but it couldn't be pinpointed.

But when a genetic match also includes a common surname, there is a far greater likelihood that there is a common ancestor within the past several hundred years. It basically makes it less likely that there was a random match.

To put it another way, the common surname and the genetic match function as two independent confirmations of a common ancestor, and this makes it more likely to be true than if you only had just the surname or just the genetic match.

On one y-dna information web site this is stated: "Matches of 23/25, 24/25 & 25/25 – there is a high probability that participants who share a surname share a common ancestor."

Why is it necessary that they share a common surname? Or is the probability somewhat less if there is no common surname?