Richard, > -----Original Message----- > From: y-dna-projects-bounces@rootsweb.com On Behalf Of RT > Sent: Wednesday, August 11, 2010 8:30 PM > To: y-dna-projects@rootsweb.com > Subject: Re: [Y-DNA-projects] WAMH vis-a-vis CMA > > Thank you for the insights, Diana > > You mention "It is possible to build a useful STR cladogram for individual families in > genealogical time because the paper genealogy can tell you the polarity of the > mutations, provided you can test enough cousins to "triangulate" on the location of > all the mutations in the family. " > > That is, provided that the paper genealogy can tell you the polarity of the mutations. Assuming the paper genealogy is correct and you have tested enough cousins, the paper genealogy will give you the polarity. The only case where it won't is where the progenitor had just two sons and one has a mutation. And, of course, that's a plus, not a negative, because you now you can distinguish the two branches of the family. > This is very often not the case in real life, and I assume it is not the case in Ralph's > example. He did not suggest a logical cladistic analysis. What example? Did I miss a message? I'm recovering from a computer failure, so it's possible I missed something... but, I just checked the archive, and I don't find a message from Ralph that would be an example. Please explain. > Re "However, I would take exception to your statement that a "mathematical" (i.e., > statistical) basis is stronger than a logical one. The situation is quite the reverse, " I > didn't actually say that. Rather, (clearly) both are helpful. A logical proof is 100% true. It always trumps a statistical proof. Yes, statistical proofs are helpful -- most conclusions of most research are statistical -- but a cladogram is a logical proof. > But the more obscure > mathematical treatment has been ignored by most. It's not that Ken's work is "obscure," it's that it's largely not relevant in genealogical time. This list is about STR testing for Y-DNA surname projects, which makes discussion of his work on topic for the GENEALOGY-DNA or Y-DNA-HAPLOGROUP-I lists, but off topic for this list. > In particular, I think that you are > implicitly relying on statistics in your logical argument. It's OK, no big deal. Forgive me, but I don't understand that statement. Please tell me where the statistics are in my example of a logical proof (see backquoted below). I wouldn't press the point, except that that the difference was the point. Diana > thanks! > Richard Thrift > > ---- Diana Gale Matthiesen <DianaGM@dgmweb.net> wrote: > Richard, > > > -----Original Message----- > > From: y-dna-projects-bounces@rootsweb.com [mailto:y-dna-projects- > > bounces@rootsweb.com] On Behalf Of RT > > Sent: Wednesday, August 11, 2010 1:59 PM > > To: y-dna-projects@rootsweb.com; rt-sails@comcast.net > > Subject: Re: [Y-DNA-projects] WAMH vis-a-vis CMA > > > > I can't say anything specific, other than that there's a HUGE possible > > range > for > > TMRCA. > > I agree with you that the confidence intervals on TMRCA's are huge, so huge that, > IMO, they are useless for genealogical purposes, as I discuss on this web > page: > http://dgmweb.net/DNA/y-dna-projects/TMRCA.shtml > > > This article by Ken Nordtvedt is very relevant, but people have tended > > to > ignore it. I > > feel it presents a mathematical basis for the "purely logical" process > > many > people use > > of looking at off-modal markers to identify a lineage. > > http://www.jogg.info/42/files/Nordtvedt.htm > > However, I would take exception to your statement that a "mathematical" (i.e., > statistical) basis is stronger than a logical one. The situation is quite the reverse. If > you can arrive at a conclusion based on established facts and a valid logical > deduction, it's a far stronger proof than a statistical one. As a simple example... > > Logical argument: > A is taller than B. > B is taller than C. > Therefore, A must be taller than C. > > Statistical argument: > A has a 90% probability of being taller than B. > B has a 90% probability of being taller than C. > Therefore, A is probably taller than C, but might not be. > > Cladistic analysis is a matter of deducing the polarity of traits (ancestral vs. > derived), then finding the most logical order of their appearance to form a cladogram > (a phylogenetic tree). The most common method of determining the polarity of traits > is through outgroup comparison, though there are other ways. > > There is a fundamental difference here between trying to construct a haplotree based > on SNP mutations and one based on STR mutations, mainly because the polarity of a > SNP mutation is much easier to deduce. They are easier to deduce because they > usually have only one of two states and they are relatively rare. > In contrast, it's difficult to determine the polarity of an STR mutation because, not > only are they relatively common (so choosing the right outgroup is difficult), they can > have many states (e.g., just because someone is 12 at a marker doesn't mean the > ancestral value was 11 -- it might have been 13), and reversals are largely > undetectable. > > It is possible to build a useful STR cladogram for individual families in genealogical > time because the paper genealogy can tell you the polarity of the mutations, provided > you can test enough cousins to "triangulate" on the location of all the mutations in > the family. > > Ken is using (or appears to me to be using) statistical haplotype "resemblance" > to form his groups, without reference to trait polarity, which means he is not engaged > in cladistics and his trees are not cladograms, except when confined to SNPs alone. > (Ken and I have been arguing this point *for years*, both on GENEALOGY-DNA and on > Y-DNA-HAPLOGROUP-I.) You may find his statistical results useful, and I do, but > statistical results based on resemblance cannot be as reliably true as a logical > cladistic analysis would be. > > Diana >