Why are geneticists retarded when sampling Poles?

[Peterski]

All genetic studies about Poles, use samples from "fringe groups" instead of ethnic core of Poland. Why?:

https://www.theapricity.com/forum/showthread.php?213172-K36-Lusatian-Sorbs-most-similar-to-Wielkopolska-Poles&p=4683487&viewfull=1#post4683487

Why the fuck do they use Latvian Poles or Estonian Poles, but not people from my area (for example)?:

https://www.theapricity.com/forum/showthread.php?218770-Subdivisions-of-Polish-people&p=4683313&viewfull=1#post4683313

https://i.imgur.com/komzDFr.jpg

I noticed surprising similarity between Poles and Latvians in Kushniarevich et al. study... :

http://www.eupedia.com/forum/threads/32372-Surprising-genetic-similarity-between-Poles-and-Latvians

... only to find out that they used Poles from former North-East Poland in that study.

Which explains their similarity to Latvians (but they are not like the majority of Poles):

https://i.imgur.com/wY6gSe5.png

These people are just +/- 15% of all Poles, and they have Baltic and East Slavic admixtures.

[RN97]

It might have something to do with difficulty. Romanian samples seem to consistently be from somewhere in the south and presumably it's easy to attain samples from there. Perhaps there are tons of samples from the "fringe" as you say and they are just re-used in several studies.

[Chev Chelios]

It happens in genetic studies, not just for Poles. When scientists choose region X instead of region Y, they have their own reasons for it. Yeah, it may affect the accuracy of the results, but their sampling is not unscientific. Big genetic studies and large amount of samples need high amount of money and too many scientists.

[Not a Cop]

Same with Russian samples, main sample is Kargopol Russians.

[Percivalle]

Same with many other ethnicities. And like RN97 said, these samples are just re-used in several studies.