I didn't proved it, but Rębała did. I provided you his article. I will quote it if you wish, but it was your homework to get to know the evidence:
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suplementary info
So he estimated admixture (supplementary table 4) for sample from Mecklenburg as 1.2%; 18.8% and 12.4% using Kashubia, Lusatia and Bavaria. When he added Kayser’s samples received 18.2-26.1% of Slavic ancestry. I think that next studies will have more pre-WWII populations to comparison, so the results will be more appropriate.
Samples used in this survey:
1. In table 4
R1a: Bavaria (n=218) 12.4%; Mecklenburg (n=131) 13.7%; Kaszuby (n=204) 61.8%; Sorbs (n=123) 65.0%
Slavic admixture in Mecklenburg 1.2% or 18.8% or 12.4%
2. With Kaysers samples
R1a: Western Germany (n=886) 12.6%; Eastern Germany (n=678) 22.3% Kashubians and Sorbs as above.
Slavic admixture in Eastern Germany 18.2-26.1%
Even though the Kayser’s data was not collected from people whose paternal lineage was in the place before WWII, so it included Germans from Poland and Eastern Europe, it showed about 20% admixture of populations like Kashubians or Sorbs. Western German population was poorer in R1a before population movement after WW2. Percentages of expellees in western Germny you can find on pages 42 and 43 in “
Population of the Federal Republic of Germany and West Berlin”.
I believe that R1a was spread Corded Ware period, but it also was dragged every ware where Slavic people decided to stay. If R1a in Germany is mostly of Corded Ware descent then there should be specific German subclades of R1a because of time of origin of Z282 around 2900 BCA. There are some clades that are older than Z280 and M458 or specific to that area - Z282*, L644, Z284, but they are less numerous then Z280 and M458. Last two clades are specific to whole central-eastern Europe, this suggest its later arrival then Corded Ware period. Alternative hypothesis are: 1. Slavic migration which outnumbered previous Germanic population so much that even Lusatian Sorbs seems to have no Germanic admixture. 2. Eastern Germany and Poland before Slavic migrations was already area of different genetic makeup much closer related paternally to populations from Dnieper basin then from Rhine basin or Jutland. If so we should expect Eastern Germanic tribes to be more like modern Poles genetically then like any Germanic population.
In coming years we will see more and more results about modern and ancient DNA and I hope this case will be solved soon.
Personally I think the most probable scenario is close to the second one, that in Central Europe population is stable genetically from early Iron Age - Lusatian culture - until
Ostsiedlung in
12th century.
Edit:
Do not forget about
Ruhrpolen their presence also raised ratio of R1a in Western Germany what is seen in Kayser's results where Cologne has 15.8% of R1a while Muenster Have only 7.8% the same for Mainz 8.4%.
Edit 2:
Are you trying to tell me that Poles are nationalistic, because you don't know when and how Polabian Slavs ware subjugated to Saxons and Danes?
Expellees in Germany were mostly located in northern Land including Mecklenburg and Schleswig-Holstein so the high R1a ratio in Rostock is probably result of immigration of Germans from eastern Europe, while the same ratio in Saxony is probably autochthonous.
Here is map showing percentages of displaced population in lands until 1950:
View attachment 7276
Next important thing is that mass migration inside Germany didn’t stop until 1961 when inner border was closed. By that time about 3,5 mln people moved from DDR to Western Germany.
Here is link to site where in the bottom is table showing increase of expellees among people in western Germany. E.g. Nordrhein-Westfalen in 1950 10% but in 1961 20%.
This process certainly influenced Rębała’s results in measurement of Slavic admixture in Eastern Germany by increasing western German ancestry.
