Re: 17 Markers

M.Sjostrom wrote:
"....assumption in the statistics that Holland and Germany can be treated as a single population. This required that there would be free movement between Holland and Germany during the period. "


Nope. The statistics of y Dna has no such assumption.
Totally irrespective of whether population was single or very separated or whatever,
the likelihoods determined by the number of differences in markers, about generations probable between branching and the samples, are as statistics show.
The simply are dependent on mutations, not on population. Mutations happen more or less similar way, whether the population is whatever - also if the population is separated from others.

If there is an identical y Dna and if the populations of the two samples are totally separate (such as, one found in Polynesi and the other in Greenland), still, for their y Dna being identical, some explanatoon simply existed, and highly likely within the most recent half a millennium. Apparent lack of contact between populations notwithstanding.
It just happened, and there must be an explanation - however unlikely that explanation were in terms of plausible family history.
[Between Greenland and Polynesia, it simply could be something as unlikely but still not impossible as a Greenlander embarking with some merchant or pirate ship towards south, then he or his descendant finding his way to southern Pacific.]
The explanation does not need to be an usual occurrence; rather, the situation is that there must be a common patrilineal forefather, after the last mutation which changed anything in the y Dna.
Mobility of population has nothing to do with that necessity nor its likelihood of timing.

Instead, the mobility of population has to do with likelihood of the plausibility of those two branches finding so different places & ways to settle.
But plausibility is not the same as total impossibility.



Let me quote a snippet of one of Doug's earlier posts: "that's what the DNA says, ABSENT ANY OTHER INFORMATION" - his emphasis. "Absent of other information" is an assumption.

Can we agree that from the way Bjorn has posted his information that he and the other party have satisfied themselves that they can trace no common ancestor? I take this as read because if they had he wouldn't have bothered to ask the question. Can we also agree that this "no common ancestor" holds good as far as 1600 which is the earliest that the German line can be traced?

OK, so now we have other information: that they have no common ancestor subsequent to 1600. It follows from that that the common ancestor must lie prior to that date. As they have matching DNA now the DNA of their last known ancestors must also have had matching DNA - unless you're proposing a mutation which has changed non-matching DNA to matching.

So we now have to rebase our calculations to 1600.

In order to examine the effect of population exchange let's consider a hypothetical case where there has been *no* interchange of population between Holland and Germany in the interval 1300 to 1600. In that extreme case we would then know that there could have been no common ancestor before 1300. We would also know that their (separate) ancestors in 1300 must also have had matching DNA. In that case we would have to rebase our calculations to 1300.

The other limiting condition is completely free interchange which enables us to treat the populations of Holland and Germany as one and we can accept the rebase to 1600.

In practice there will have been some movement from Holland to Germany. If, however, this movement was very limited the probability that it contained a common ancestor is small. If the movement is larger then the probability is larger. If neither limiting condition applies then the probability distribution will give results somewhere between the two limits.

--
Ian

Hotmail is for spammers. Real mail address is igoddard
at nildram co uk
.

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