Neolithic Swedes. On the recent side, researchers have used surnames or even toponyms to show that ethnic admixture in the recent historical past has shifted Y-chromosome frequencies around.
A new paper in EJHG follows on this tradition by comparing pre- and post-WWII patterns of Y chromosome variation in Germany and Poland. Y-haplogroup frequencies can be seen on top left. From the caption: "Phylogenetic relationship and frequencies of Y-chromosomal haplogroups in the studied populations. Ka Kaszuby; Ko Kociewie; Ku Kurpie; Lu Lusatia; Sl Slovakia; Me Mecklenburg; Ba Bavaria."
It is important to note that the researchers were able to study pre-war populations, because most everybody knows where their patrilineal ancestor lived less than 100 years ago. But, European history consists of many events whose effects on the current population are less known, because they occurred at an older time. In some cases, populations may have migrated (such as the Germans of eastern Europe following WWII), in others populations that have once existed there have almost disappeared, or become much less numerically significant (such as the Ashkenazi Jews due to persecution during WWII and after it through migration to Israel and elsewhere, or various Christian and Jewish communities that once flourished throughout the Middle East). Other, less known groups, such as the Old Prussians or the Jassic speakers of Hungary have been presumably absorbed by surrounding majorities, or through a process of elite dominance.
In many cases, the available information, in the form of linguistic, genealogical, or historical evidence, can be used to remove layers of admixture, migration, and extinction in history; but, the gap between the deep prehistoric past and the recent, historical one cannot be bridged by these methods alone. Ultimately, ancient DNA researchers must close in on the present by targeting more recent populations for analysis. As the realization of genetic change continues to amass on both sides of the divide, I suspect that this will come naturally, although I do expect some reticence to the findings as they begin to touch upon the most cherished origins traditions of the multitude of extant European nations.
European Journal of Human Genetics advance online publication 12 September 2012; doi: 10.1038/ejhg.2012.190
Contemporary paternal genetic landscape of Polish and German populations: from early medieval Slavic expansion to post-World War II resettlements
Krzysztof Rebala et al.
Homogeneous Proto-Slavic genetic substrate and/or extensive mixing after World War II were suggested to explain homogeneity of contemporary Polish paternal lineages. Alternatively, Polish local populations might have displayed pre-war genetic heterogeneity owing to genetic drift and/or gene flow with neighbouring populations. Although sharp genetic discontinuity along the political border between Poland and Germany indisputably results from war-mediated resettlements and homogenisation, it remained unknown whether Y-chromosomal diversity in ethnically/linguistically defined populations was clinal or discontinuous before the war. In order to answer these questions and elucidate early Slavic migrations, 1156 individuals from several Slavic and German populations were analysed, including Polish pre-war regional populations and an autochthonous Slavic population from Germany. Y chromosomes were assigned to 39 haplogroups and genotyped for 19 STRs. Genetic distances revealed similar degree of differentiation of Slavic-speaking pre-war populations from German populations irrespective of duration and intensity of contacts with German speakers. Admixture estimates showed minor Slavic paternal ancestry (~20%) in modern eastern Germans and hardly detectable German paternal ancestry in Slavs neighbouring German populations for centuries. BATWING analysis of isolated Slavic populations revealed that their divergence was preceded by rapid demographic growth, undermining theory that Slavic expansion was primarily linguistic rather than population spread. Polish pre-war regional populations showed within-group heterogeneity and lower STR variation within R-M17 subclades compared with modern populations, which might have been homogenised by war resettlements. Our results suggest that genetic studies on early human history in the Vistula and Oder basins should rely on reconstructed pre-war rather than modern populations.