A new study on human Y chromosomes has found a strong differentiation between German and Polish Y-chromosomes. The differentiation occurs precisely at the border between the two countries, with all German and all Polish populations clustering together.
The explanation for this phenomenon is that resettlements after WWII homogenized the two nations on an ethnic basis. Moreover, a necessary assumption is that there was little male admixture between the two peoples when they co-existed geographically.
The differentiation is evident based on analyses both of Y-STR haplotypes and Y-chromosomal haplogroups. The main contributors to the differentiation are the higher frequency of R1a1 in Poland and correspondingly higher frequency of R1*(xR1a1) in Germany, and the presence of different haplotype clusters for haplogroup I in the two countries. The correspondence analysis between haplogroups and populations is particularly interesting:
We see that Poles are differentiated by Germans on the basis of R1a1 and N3 (Finno-Ugrian admixture). The differentiation on the basis of I subgroups is not evident, because no downstream markers for this haplogroup were examined in this study.
Also of particular interest is that of the two Neolithic haplogroups, J2 is associated with Germans, whereas DE* is apparently not. So, this may hint at different patterns of arrival of the two haplogroups in this part of the world. This would agree with some recent results from Balkan Slavic populations, that typically found a higher-percentage of YAP (DE) lineages than J2 ones.
Human Genetics (advanced publication online)
Significant genetic differentiation between Poland and Germany follows present-day political borders, as revealed by Y-chromosome analysis
Manfred Kayser et al.
Abstract To test for human population substructure and to investigate human population history we have analysed Y-chromosome diversity using seven microsatellites (Y-STRs) and ten binary markers (Y-SNPs) in samples from eight regionally distributed populations from Poland (n=913) and 11 from Germany (n=1,215). Based on data from both Y-chromosome marker systems, which we found to be highly correlated (r=0.96), and using spatial analysis of the molecular variance (SAMOVA), we revealed statistically significant support for two groups of populations: (1) all Polish populations and (2) all German populations. By means of analysis of the molecular variance (AMOVA) we observed a large and statistically significant proportion of 14% (for Y-SNPs) and 15% (for Y-STRs) of the respective total genetic variation being explained between both countries. The same population differentiation was detected using Monmonierrsquos algorithm, with a resulting genetic border between Poland and Germany that closely resembles the course of the political border between both countries. The observed genetic differentiation was mainly, but not exclusively, due to the frequency distribution of two Y-SNP haplogroups and their associated Y-STR haplotypes: R1a1*, most frequent in Poland, and R1*(xR1a1), most frequent in Germany. We suggest here that the pronounced population differentiation between the two geographically neighbouring countries, Poland and Germany, is the consequence of very recent events in human population history, namely the forced human resettlement of many millions of Germans and Poles during and, especially, shortly after World War II. In addition, our findings have consequences for the forensic application of Y-chromosome markers, strongly supporting the implementation of population substructure into forensic Y chromosome databases, and also for genetic association studies.