I wanted to participate in this thread earlier but somehow forgot, ancestry DNA is organized along the same lines as "Genographic Project" which essentially is a paid evaluation and costs a minimum of $100, ancestry DNA if I am not wrong is 79 British Pound. Over the period of time those who have opted for the test due to one reason or the other their data is collected, compiled and common markers are identified and classified. My understanding is all such initiatives share their data with other agencies like AncestrsyDNA with Genographic and a whole array of such projects.
This would depend. In the West, any such sharing has to be disclosed to the end user for legal reasons. Also, many larger companies would rely on their database size and samples being distinct for competitive advantage.
What actually happening is that a sample from upper 5-10% of the population has been contributing to these test/databanks for one reason or the other, the sample size is very limited in scope and I know for sure that there are families/tribes out here in Pakistan which have never married outside their own blood line, there are communities which are totally isolated, I have no idea about the sample size but truly while those who could afford to go for this test for establishing their roots or those opting for the test to establish parental/descendant/sibling status is very limited.
This again would depend. For e.g, regions with limited genetic flow from other parts of the world, like Scandinavia, would be much easier to classify even with relatively smaller sample population sizes. However, countries like Pakistan that sit in very prominent geography due to historic trade and countless migrations/empires, it would indeed become more difficult to correctly classify who's who and what originated where. In many ways, this question is answered by collecting large amounts of samples from other regions around the world where populations are less mixed, and then having to use historic knowledge to a certain extent to undo the complications. Of course, as sample sizes increase, this becomes much easier.
We could, of course, link the above to a simple test of comparing siblings, where a very large amount of genetic data is shared, and therefore it becomes relatively easier to identify origin. That said, ancestry and general familial relationship testing is quite different due to the basis for results being highly differentiated because of geography based markers.
Coming back to this particular test, as the database size increases, the results will start to become more accurate, but even 5-10% would be considered significant in most regions, and the test will therefore show a larger geographic area during initial result disclosure for such samples. Sticking to these tests, it is only now that the region in question is becoming much easier to classify from earlier times when only a larger geography was disclosed, and this will be due to an increase in sample size, much like tiny European countries sitting in Central Europe being quite difficult to classify with any kind of accuracy.
Overall, though, the recently published scientific papers that took samples from ancient population skeletons were a major turning point in making sense of much of this.
While many have opted to establish the first one the second one is anathema. This data could not effectively establish its conclusion, unless it adds that the conclusion from the sample leads to the theory but the confidence interval is highly questionable and unless I missed something major out.
Well, as above, you can't really establish geographic status for a tribe that once lived in Southern Europe and moved in whole to a completely different but genetically close area, so ancient samples are needed to establish that connection. However, such data can never be truly accurate in some cases, but with very large sample sizes and more accurate ancient DNA tagged along with accurate historic information, much of the puzzle pieces will simply just fall in place.
As a consolation, most of the larger companies are continually updating their origin data as new information and data becomes available, which is exactly what has happened here.
All said, the biggest issue faced in the region was largely down to Indian origin scientists constantly withholding information or providing skewed results that threw everyone off, much of which I would put down to political meddling due to the promotion of a single unifying identity by the recent governments in that country.
In fact, it was only when the linked report was published by over 90 world scientists, although continually delayed due to said nationality contributors, that the picture drastically changed.
The very notion of the promotion of the Out-of-India theory given all the evidence speaks volumes on that account.
