Here is a bit more detail in connection with a question that relates to the significance of finding matches between Plant/Plantt and Warren/Waring. The key question is: Would these matches be expected just by random chance or are they a significant finding? I have now looked into this a bit further, using the latest evidence I can find.
First, here is a bit more detail for the matter of the Plant/Plantt and Warren/Waring matches at the 12 marker level. The most common signature (PMH12) for Plant/Plantt at the 12 marker level is just 1 mutation different from the WAMH (the most common signature for the general population of men in Western Europe). About 2.5% of men in Western Europe have the 12 marker WAMH and, no doubt, (?far) fewer have the PMH12 which is 1 mutation different. I do not know the exact percentage for PMH12 but, let's be cautious, and say it could be as many as 2%. There is one Warren and one Waring who match exactly the PMH12 (at the 12 marker level). Sinceresults are now available for 68 Warrens and 9 Warings we can now say that 2.7% have matched exactly with Plant/Plantt which may not be many more than the randomly expected number (which may be as high as 2%). When the Plant-Waring match was first found, it seemed more surprising than it has now become.
Turning to the 25 marker level, the situation is rather different. At the 25 marker level, the most common signature for Plant/Plantt (PMH25) is more distinct, being 7 mutations different from the super-WAMH. I do not know the percentage for the super-WAMH but it is presumably far lower than 2% and the percentage for the PMH25 is no doubt very small indeed. I shall keep working at this to see if I can get the actual percentages. However, suffice it to say for the moment that this helps to explain why I consider that there is not normally a good reason for going beyond 25 markers for the Plant/Plantt signature. However, the situation for the Warren/Waring 25 marker match is not quite so good, for three different reasons:
1. it involves only 1 individual from each family rather than the most common signature for each family;
2. while 1.5 mutations difference between them is expected if the relationship was 30 generations ago, the match found is on the outer edge of this at 2 mutations; and,
3. the matching Warren has exactly the super-WAMH at the 25 marker level (with the matching Waring 2 mutations different) and so his 25 marker signature is not nearly as distinct as that for Plant/Plantt; in this situation, there is a greater case (than for Plant/Plantt) for going for still more markers than 25.
Hoping that this is of some interest. It seems important to consider this level of detail for assessing the significance of the matches.
(a) the Plant to Plantt match is very sound;
(b) the individual Warren match to an individual Waring is far less sound, though there is a bit of documentary evidence that is consistent with this possibility; and,
(c) the Plant/Plantt match to another Warren, who has only been checked out to the 12 marker level, is hardly more than can be expected by random chance