UPDATE (March 17):
From the paper:
The most outstanding populations were those of Poland and northern Belarus, while populations of central Belarus, southern Belarus and Slovakia were genetically indistinguishable.
The most apparent genetic distance was found between the northern (Eastern and Western) and Southern Slavs, who at the end of the 9th century were separated by the invasion of Finno-
Ugric Hungarians [...] The observed northern Slavic Y-STR genetic homogeneity extends from Slovakia and Ukraine to parts of Russia and Belarus, but also involves Southern-Slavic populations of Slovenia and western Croatia, and is the most probably due to a homogeneous genetic substrate inherited from the ancestral Slavic population. However, due to the Y-STR proximity of linguistically and geographically Southern-Slavic Slovenes and western Croats to the northern Slavic branch, the observed genetic differentiation cannot simply be explained by the separation of both Slavic-speaking groups by the non-Slavic Romanians, Hungarians, and Germanspeaking Austrians [...] Thus, the contribution of the Y chromosomes of peoples who settled in the region before the Slavic expansion to the genetic heritage of Southern Slavs is the most likely explanation for this phenomenon. On the other hand, our results indicate no significant genetic traces of pre-sixth-century inhabitants of present-day Slovenia in the Slovene Y chromosome genetic pool.
AMOVA revealed significant differences in Y-STR distribution between Slavic and Baltic populations (P < 0.005 for all pairwise comparisons), which is
likely to result from the previously observed different Ychromosomal
haplogroup distribution (Rosser et al. 2000). The Baltic populations are characterised by the high incidence of the Y-chromosomal haplogroup N3 (47% among Lithuanians, 32% among Latvians) (Rosser et al. 2000; Zerjal et al. 2001). Its distribution pattern in Slavic populations indicates that Proto-Slavs did not carry this lineage at a substantial frequency, since it is relatively rare among Slavs and at high frequency was observed only in some Russian subpopulations (Malyarchuk et al. 2004).
we estimated haplogroup N3 frequencies in the three Belarusian subpopulations. The results suggest that the uniqueness of the northern Belarusian population is most likely due to the high incidence of Y chromosomes from the haplogroup N3 (18.9%), which has half the frequency in central and southern Belarus (8.8 and 8.1%, respectively). Therefore, although the early ethnogenesis of the Belarusian nation has customarily been linked to the gradual Slavicisation of the homogeneous Baltic substrate on the territory of present-day Belarus (Sedov 1970), only northern Belarus seems to be a transient area for the Baltic and Slavic settlement.
Because Slavs unequivocally enter the records of history as late as the sixth century AD, when their expansion in Eastern Europe was already advanced, different theories concerning the Slavs’ geographic origin based on archaeological, anthropological and/or linguistic data have been formulated. Two such theories have gained the largest support among the scientists (Schenker 1995), one placing the cradle of Slavs in the watershed of the Vistula and Oder rivers (present-day Poland), and the other locating it in the watershed of the middle Dnieper (present-day Ukraine). Our results indicate that using the population-of-origin approach based on the AMOVA, as many as nine (P > 0.05) or ten (P > 0.01) populations can be traced back to the lands of present-day Ukraine, including Eastern-Slavic Russians and Belarusians, Western-Slavic Poles and Slovaks, and Southern-Slavic Slovenes and Croats.
Results of the interpopulation Y-STR haplotype analysis exclude a significant contribution of ancient tribes inhabiting present-day Poland to the gene pool of Eastern and Southern Slavs, and suggest that the Slavic expansion started from present-day Ukraine, thus supporting the hypothesis that places the earliest known homeland of Slavs in the basin of the middle Dnieper.
The paper confirms some points that were already known by previous work, namely the Y chromosomal homogeneity of Slavs. Some Slavic groups such as Czechs are missing from the analysis. The homogeneity is less visible in groups that have absorbed significant substrata, i.e., in some Balkan populations and in populations that have absorbed Finno-Ugrian elements characterized by haplogroup N3.
The interpretation of the homogeneity would benefit greatly by an estimation of time depth. There are not dates in the paper, so it is not clear (although possible) that the homogeneity is due to the medieval Slavic dispersal.
The use of Y-STRs is useful for estimating historical relationships, but a limited number of these is used for most populations except for the core group where 18 STRs were used. The use of binary haplogroup data - used in the paper only for the presence of haplogroup N3 - would help determine the elements present in the different populations. The chosen approach gives no insight about the genetic identity of the population of Proto-Slavs.
The paper does make a good case for Ukraine being the Proto-Slavic homeland, since Poland emerges clearly as a destination of a subset of Y chromosome diversity rather than as a unifying source of diversity observed in all major Slavic sub-groups. But, the date of the Out-of-Ukraine expansion, likely to be reflected in specific haplogroup R1a1 subclades is not established and must await further research.
Journal of Human Genetics (online early)
Y-STR variation among Slavs: evidence for the Slavic homeland in the middle Dnieper basin
Krzysztof Rębała, Alexei I. Mikulich, Iosif S. Tsybovsky, Daniela Siváková, Zuzana Džupinková, Aneta Szczerkowska-Dobosz and Zofia Szczerkowska
Abstract A set of 18 Y-chromosomal microsatellite loci was analysed in 568 males from Poland, Slovakia and three regions of Belarus. The results were compared to data available for 2,937 Y chromosome samples from 20 other Slavic populations. Lack of relationship between linguistic, geographic and historical relations between Slavic populations and Y-short tandem repeat (STR) haplotype distribution was observed. Two genetically distant groups of Slavic populations were revealed: one encompassing all Western-Slavic, Eastern-Slavic, and two Southern-Slavic populations, and one encompassing all remaining Southern Slavs. An analysis of molecular variance (AMOVA) based on Y-chromosomal STRs showed that the variation observed between the two population groups was 4.3%, and was higher than the level of genetic variance among populations within the groups (1.2%). Homogeneity of northern Slavic paternal lineages in Europe was shown to stretch from the Alps to the upper Volga and involve ethnicities speaking completely different branches of Slavic languages. The central position of the population of Ukraine in the network of insignificant AMOVA comparisons, and the lack of traces of significant contribution of ancient tribes inhabiting present-day Poland to the gene pool of Eastern and Southern Slavs, support hypothesis placing the earliest known homeland of Slavs in the middle Dnieper basin.